Cisco Blade Switches for Dell Configuration Guide

Cisco Catalyst Blade Switch 3030 for Dell
Software Configuration Guide
Cisco IOS Release 15.0(2)SE
August 2012
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Fax: 408 527-0883
Text Part Number: OL-27326-01
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Cisco Catalyst Blade Switch 3030 for Dell Software Configuration Guide
© 2006-2012 Cisco Systems, Inc. All rights reserved.
CONTENTS
Preface
xxxvii
Audience
Purpose
xxxvii
xxxvii
Conventions
xxxvii
Related Publications
xxxviii
Obtaining Documentation and Submitting a Service Request
CHAPTER
1
Overview
1-1
Features 1-1
Ease-of-Deployment and Ease-of-Use Features
Performance Features 1-2
Management Options 1-3
Manageability Features 1-4
Availability and Redundancy Features 1-5
VLAN Features 1-6
Security Features 1-7
QoS and CoS Features 1-10
Layer 3 Features 1-11
Monitoring Features 1-12
Default Settings After Initial Switch Configuration
Design Concepts for Using the Switch
Where to Go Next
CHAPTER
2
xxxix
1-2
1-12
1-15
1-17
Using the Command-Line Interface
Understanding Command Modes
Understanding the Help System
2-1
2-1
2-3
Understanding Abbreviated Commands
2-3
Understanding no and default Forms of Commands
Understanding CLI Error Messages
Using Configuration Logging
2-4
2-4
2-4
Using Command History 2-5
Changing the Command History Buffer Size
Recalling Commands 2-5
2-5
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Disabling the Command History Feature
2-6
Using Editing Features 2-6
Enabling and Disabling Editing Features 2-6
Editing Commands through Keystrokes 2-7
Editing Command Lines that Wrap 2-8
Searching and Filtering Output of show and more Commands
Accessing the CLI
CHAPTER
3
2-9
2-9
Assigning the Switch IP Address and Default Gateway
Understanding the Bootup Process
3-1
3-1
Assigning Switch Information 3-2
Default Switch Information 3-3
Understanding DHCP-Based Autoconfiguration 3-3
DHCP Client Request Process 3-4
Understanding DHCP-based Autoconfiguration and Image Update 3-5
DHCP Autoconfiguration 3-5
DHCP Auto-Image Update 3-5
Limitations and Restrictions 3-5
Configuring DHCP-Based Autoconfiguration 3-6
DHCP Server Configuration Guidelines 3-6
Configuring the TFTP Server 3-7
Configuring the DNS 3-7
Configuring the Relay Device 3-8
Obtaining Configuration Files 3-9
Example Configuration 3-10
Configuring the DHCP Auto Configuration and Image Update Features 3-11
Configuring DHCP Autoconfiguration (Only Configuration File) 3-11
Configuring DHCP Auto-Image Update (Configuration File and Image) 3-12
Configuring the Client 3-13
Manually Assigning IP Information 3-14
Checking and Saving the Running Configuration
Configuring the NVRAM Buffer Size 3-16
3-15
Modifying the Startup Configuration 3-17
Default Bootup Configuration 3-18
Automatically Downloading a Configuration File 3-18
Specifying the Filename to Read and Write the System Configuration
Booting Up Manually 3-19
Booting Up a Specific Software Image 3-19
Controlling Environment Variables 3-20
3-18
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Scheduling a Reload of the Software Image 3-22
Configuring a Scheduled Reload 3-23
Displaying Scheduled Reload Information 3-24
CHAPTER
4
Configuring Cisco IOS Configuration Engine
4-1
Understanding Cisco Configuration Engine Software 4-1
Configuration Service 4-2
Event Service 4-3
NameSpace Mapper 4-3
What You Should Know About the CNS IDs and Device Hostnames
ConfigID 4-3
DeviceID 4-4
Hostname and DeviceID 4-4
Using Hostname, DeviceID, and ConfigID 4-4
Understanding Cisco IOS Agents 4-5
Initial Configuration 4-5
Incremental (Partial) Configuration
Synchronized Configuration 4-6
4-3
4-6
Configuring Cisco IOS Agents 4-6
Enabling Automated CNS Configuration 4-6
Enabling the CNS Event Agent 4-8
Enabling the Cisco IOS CNS Agent 4-9
Enabling an Initial Configuration 4-9
Enabling a Partial Configuration 4-13
Displaying CNS Configuration
CHAPTER
5
Administering the Switch
4-14
5-1
Managing the System Time and Date 5-1
Understanding the System Clock 5-1
Understanding Network Time Protocol 5-2
NTP Version 4 5-3
Configuring Time and Date Manually 5-4
Setting the System Clock 5-4
Displaying the Time and Date Configuration 5-5
Configuring the Time Zone 5-5
Configuring Summer Time (Daylight Saving Time) 5-6
Configuring a System Name and Prompt 5-7
Default System Name and Prompt Configuration
Configuring a System Name 5-8
5-8
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Understanding DNS 5-8
Default DNS Configuration 5-9
Setting Up DNS 5-9
Displaying the DNS Configuration
5-10
Creating a Banner 5-10
Default Banner Configuration 5-10
Configuring a Message-of-the-Day Login Banner
Configuring a Login Banner 5-12
5-11
Managing the MAC Address Table 5-12
Building the Address Table 5-13
MAC Addresses and VLANs 5-13
Default MAC Address Table Configuration 5-14
Changing the Address Aging Time 5-14
Removing Dynamic Address Entries 5-15
Configuring MAC Address Change Notification Traps 5-15
Configuring MAC Address Move Notification Traps 5-17
Configuring MAC Threshold Notification Traps 5-18
Adding and Removing Static Address Entries 5-19
Configuring Unicast MAC Address Filtering 5-20
Disabling MAC Address Learning on a VLAN 5-21
Displaying Address Table Entries 5-23
Managing the ARP Table
CHAPTER
6
Configuring SDM Templates
5-23
6-1
Understanding the SDM Templates 6-1
Dual IPv4 and IPv6 SDM Templates 6-2
Configuring the Switch SDM Template 6-3
Default SDM Template 6-3
SDM Template Configuration Guidelines
Setting the SDM Template 6-4
Displaying the SDM Templates
CHAPTER
7
6-4
6-5
Configuring Switch-Based Authentication
7-1
Preventing Unauthorized Access to Your Switch
7-1
Protecting Access to Privileged EXEC Commands 7-2
Default Password and Privilege Level Configuration 7-2
Setting or Changing a Static Enable Password 7-3
Protecting Enable and Enable Secret Passwords with Encryption
Disabling Password Recovery 7-5
7-3
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Setting a Telnet Password for a Terminal Line 7-6
Configuring Username and Password Pairs 7-6
Configuring Multiple Privilege Levels 7-7
Setting the Privilege Level for a Command 7-8
Changing the Default Privilege Level for Lines 7-9
Logging into and Exiting a Privilege Level 7-9
Controlling Switch Access with TACACS+ 7-10
Understanding TACACS+ 7-10
TACACS+ Operation 7-12
Configuring TACACS+ 7-12
Default TACACS+ Configuration 7-13
Identifying the TACACS+ Server Host and Setting the Authentication Key 7-13
Configuring TACACS+ Login Authentication 7-14
Configuring TACACS+ Authorization for Privileged EXEC Access and Network Services
Starting TACACS+ Accounting 7-17
Establishing a Session with a Router if the AAA Server is Unreachable 7-17
Displaying the TACACS+ Configuration 7-17
7-16
Controlling Switch Access with RADIUS 7-17
Understanding RADIUS 7-18
RADIUS Operation 7-19
RADIUS Change of Authorization 7-20
Overview 7-20
Change-of-Authorization Requests 7-20
CoA Request Response Code 7-22
CoA Request Commands 7-23
Configuring RADIUS 7-25
Default RADIUS Configuration 7-26
Identifying the RADIUS Server Host 7-26
Configuring RADIUS Login Authentication 7-28
Defining AAA Server Groups 7-30
Configuring RADIUS Authorization for User Privileged Access and Network Services 7-32
Starting RADIUS Accounting 7-33
Establishing a Session with a Router if the AAA Server is Unreachable 7-33
Configuring Settings for All RADIUS Servers 7-34
Configuring the Switch to Use Vendor-Specific RADIUS Attributes 7-34
Configuring the Switch for Vendor-Proprietary RADIUS Server Communication 7-36
Configuring CoA on the Switch 7-37
Monitoring and Troubleshooting CoA Functionality 7-38
Configuring RADIUS Server Load Balancing 7-38
Displaying the RADIUS Configuration 7-38
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Controlling Switch Access with Kerberos 7-38
Understanding Kerberos 7-39
Kerberos Operation 7-41
Authenticating to a Boundary Switch 7-41
Obtaining a TGT from a KDC 7-41
Authenticating to Network Services 7-42
Configuring Kerberos 7-42
Configuring the Switch for Local Authentication and Authorization
Configuring the Switch for Secure Shell 7-43
Understanding SSH 7-44
SSH Servers, Integrated Clients, and Supported Versions
Limitations 7-45
Configuring SSH 7-45
Configuration Guidelines 7-45
Setting Up the Switch to Run SSH 7-46
Configuring the SSH Server 7-47
Displaying the SSH Configuration and Status 7-48
7-42
7-44
Configuring the Switch for Secure Socket Layer HTTP 7-48
Understanding Secure HTTP Servers and Clients 7-48
Certificate Authority Trustpoints 7-49
CipherSuites 7-50
Configuring Secure HTTP Servers and Clients 7-51
Default SSL Configuration 7-51
SSL Configuration Guidelines 7-51
Configuring a CA Trustpoint 7-51
Configuring the Secure HTTP Server 7-52
Configuring the Secure HTTP Client 7-54
Displaying Secure HTTP Server and Client Status 7-54
Configuring the Switch for Secure Copy Protocol
Information About Secure Copy 7-55
CHAPTER
8
7-55
Configuring IEEE 802.1x Port-Based Authentication
8-1
Understanding IEEE 802.1x Port-Based Authentication 8-1
Device Roles 8-3
Authentication Process 8-4
Authentication Initiation and Message Exchange 8-6
Authentication Manager 8-8
Port-Based Authentication Methods 8-9
Per-User ACLs and Filter-Ids 8-9
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Authentication Manager CLI Commands 8-10
Ports in Authorized and Unauthorized States 8-11
802.1x Host Mode 8-12
802.1x Multiple Authentication Mode 8-13
MAC Move 8-14
MAC Replace 8-14
802.1x Accounting 8-15
802.1x Accounting Attribute-Value Pairs 8-15
802.1x Readiness Check 8-16
802.1x Authentication with VLAN Assignment 8-16
802.1x Authentication with Per-User ACLs 8-18
802.1x Authentication with Downloadable ACLs and Redirect URLs 8-19
Cisco Secure ACS and Attribute-Value Pairs for the Redirect URL 8-20
Cisco Secure ACS and Attribute-Value Pairs for Downloadable ACLs 8-21
VLAN ID-based MAC Authentication 8-21
802.1x Authentication with Guest VLAN 8-21
802.1x Authentication with Restricted VLAN 8-23
802.1x Authentication with Inaccessible Authentication Bypass 8-24
Support on Multiple-Authentication Ports 8-24
Authentication Results 8-24
Feature Interactions 8-24
802.1x User Distribution 8-25
802.1x User Distribution Configuration Guidelines 8-26
802.1x Authentication with Voice VLAN Ports 8-26
802.1x Authentication with Port Security 8-26
802.1x Authentication with Wake-on-LAN 8-27
802.1x Authentication with MAC Authentication Bypass 8-27
Network Admission Control Layer 2 802.1x Validation 8-28
Flexible Authentication Ordering 8-29
Open1x Authentication 8-29
Using Multidomain Authentication 8-30
Voice Aware 802.1x Security 8-31
802.1x Supplicant and Authenticator Switches with Network Edge Access Topology (NEAT)
Guidelines 8-32
Common Session ID 8-32
8-31
Configuring 802.1x Authentication 8-33
Default 802.1x Authentication Configuration 8-34
802.1x Authentication Configuration Guidelines 8-35
802.1x Authentication 8-35
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VLAN Assignment, Guest VLAN, Restricted VLAN, and Inaccessible Authentication
Bypass 8-36
MAC Authentication Bypass 8-37
Maximum Number of Allowed Devices Per Port 8-37
Configuring 802.1x Readiness Check 8-38
Configuring Voice Aware 802.1x Security 8-39
Configuring 802.1x Violation Modes 8-40
Configuring 802.1x Authentication 8-41
Configuring the Switch-to-RADIUS-Server Communication 8-42
Configuring the Host Mode 8-43
Enabling MAC Move 8-44
Enabling MAC Replace 8-45
Configuring Periodic Re-Authentication 8-45
Manually Re-Authenticating a Client Connected to a Port 8-46
Changing the Quiet Period 8-47
Changing the Switch-to-Client Retransmission Time 8-47
Setting the Switch-to-Client Frame-Retransmission Number 8-48
Setting the Re-Authentication Number 8-49
Configuring 802.1x Accounting 8-49
Configuring a Guest VLAN 8-50
Configuring a Restricted VLAN 8-51
Configuring the Inaccessible Authentication Bypass Feature 8-53
Configuring 802.1x User Distribution 8-56
Configuring 802.1x Authentication with WoL 8-57
Configuring MAC Authentication Bypass 8-57
Configuring NAC Layer 2 802.1x Validation 8-58
Configuring IEEE 802.1x Authentication Using a RADIUS Server 8-59
Configuring an Authenticator and a Supplicant Switch with NEAT 8-60
Configuring NEAT with ASP 8-61
Configuring 802.1x Authentication with Downloadable ACLs and Redirect URLs 8-61
Configuring Downloadable ACLs 8-62
Configuring a Downloadable Policy 8-62
Configuring VLAN ID-based MAC Authentication 8-64
Configuring Flexible Authentication Ordering 8-64
Configuring Open1x 8-65
Disabling 802.1x Authentication on the Port 8-65
Resetting the 802.1x Authentication Configuration to the Default Values
Displaying 802.1x Statistics and Status
8-66
8-66
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CHAPTER
9
Configuring Web-Based Authentication
9-1
Understanding Web-Based Authentication 9-1
Device Roles 9-2
Host Detection 9-2
Session Creation 9-3
Authentication Process 9-3
Local Web Authentication Banner 9-4
Web Authentication Customizable Web Pages 9-6
Guidelines 9-6
Web-based Authentication Interactions with Other Features
Port Security 9-7
LAN Port IP 9-8
Gateway IP 9-8
ACLs 9-8
Context-Based Access Control 9-8
802.1x Authentication 9-8
EtherChannel 9-8
9-7
Configuring Web-Based Authentication 9-9
Default Web-Based Authentication Configuration 9-9
Web-Based Authentication Configuration Guidelines and Restrictions
Web-Based Authentication Configuration Task List 9-10
Configuring the Authentication Rule and Interfaces 9-10
Configuring AAA Authentication 9-11
Configuring Switch-to-RADIUS-Server Communication 9-12
Configuring the HTTP Server 9-13
Customizing the Authentication Proxy Web Pages 9-14
Specifying a Redirection URL for Successful Login 9-15
Configuring the Web-Based Authentication Parameters 9-16
Configuring a Web Authentication Local Banner 9-16
Removing Web-Based Authentication Cache Entries 9-17
Displaying Web-Based Authentication Status
CHAPTER
10
Configuring Interface Characteristics
Understanding Interface Types
Port-Based VLANs 10-2
Switch Ports 10-2
Access Ports 10-3
Trunk Ports 10-3
Tunnel Ports 10-4
Routed Ports 10-4
9-9
9-17
10-1
10-1
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Switch Virtual Interfaces 10-4
SVI Autostate Exclude 10-5
EtherChannel Port Groups 10-6
Connecting Interfaces 10-6
Using Interface Configuration Mode 10-7
Procedures for Configuring Interfaces 10-8
Configuring a Range of Interfaces 10-8
Configuring and Using Interface Range Macros
10-10
Configuring Ethernet Interfaces 10-11
Default Ethernet Interface Configuration 10-12
Configuring Interface Speed and Duplex Mode 10-13
Speed and Duplex Configuration Guidelines 10-13
Setting the Interface Speed and Duplex Parameters
Configuring IEEE 802.3x Flow Control 10-15
Configuring Auto-MDIX on an Interface 10-16
Adding a Description for an Interface 10-17
Configuring Layer 3 Interfaces 10-17
Configuring SVI Autostate Exclude
Configuring the System MTU
10-14
10-19
10-20
Monitoring and Maintaining the Interfaces 10-21
Monitoring Interface Status 10-22
Clearing and Resetting Interfaces and Counters 10-22
Shutting Down and Restarting the Interface 10-23
CHAPTER
11
Configuring Smartports Macros
11-1
Understanding Smartports Macros
11-1
Configuring Smartports Macros 11-2
Default Smartports Macro Configuration 11-2
Smartports Macro Configuration Guidelines 11-2
Creating Smartports Macros 11-4
Applying Smartports Macros 11-5
Applying Cisco-Default Smartports Macros 11-6
Displaying Smartports Macros
CHAPTER
12
Configuring VLANs
11-8
12-1
Understanding VLANs 12-1
Supported VLANs 12-2
VLAN Port Membership Modes
12-3
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Configuring Normal-Range VLANs 12-4
Token Ring VLANs 12-6
Normal-Range VLAN Configuration Guidelines 12-6
Creating Normal-Range VLANs 12-7
Default Ethernet VLAN Configuration 12-7
Creating or Modifying an Ethernet VLAN 12-8
Deleting a VLAN 12-9
Assigning Static-Access Ports to a VLAN 12-10
Configuring Extended-Range VLANs 12-11
Default VLAN Configuration 12-11
Extended-Range VLAN Configuration Guidelines 12-11
Creating an Extended-Range VLAN 12-12
Creating an Extended-Range VLAN with an Internal VLAN ID
Displaying VLANs
12-13
12-14
Configuring VLAN Trunks 12-15
Trunking Overview 12-15
Encapsulation Types 12-17
IEEE 802.1Q Configuration Considerations 12-17
Default Layer 2 Ethernet Interface VLAN Configuration 12-18
Configuring an Ethernet Interface as a Trunk Port 12-18
Interaction with Other Features 12-18
Configuring a Trunk Port 12-19
Defining the Allowed VLANs on a Trunk 12-20
Changing the Pruning-Eligible List 12-21
Configuring the Native VLAN for Untagged Traffic 12-22
Configuring Trunk Ports for Load Sharing 12-22
Load Sharing Using STP Port Priorities 12-23
Load Sharing Using STP Path Cost 12-24
Configuring VMPS 12-26
Understanding VMPS 12-26
Dynamic-Access Port VLAN Membership 12-27
Default VMPS Client Configuration 12-27
VMPS Configuration Guidelines 12-27
Configuring the VMPS Client 12-28
Entering the IP Address of the VMPS 12-28
Configuring Dynamic-Access Ports on VMPS Clients
Reconfirming VLAN Memberships 12-29
Changing the Reconfirmation Interval 12-30
Changing the Retry Count 12-30
12-29
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Monitoring the VMPS 12-30
Troubleshooting Dynamic-Access Port VLAN Membership
VMPS Configuration Example 12-31
CHAPTER
13
Configuring VTP
12-31
13-1
Understanding VTP 13-1
The VTP Domain 13-2
VTP Modes 13-3
VTP Advertisements 13-3
VTP Version 2 13-4
VTP Version 3 13-5
VTP Pruning 13-5
Configuring VTP 13-7
Default VTP Configuration 13-7
VTP Configuration Guidelines 13-8
Domain Names 13-8
Passwords 13-8
VTP Version 13-9
Configuration Requirements 13-10
Configuring VTP Mode 13-10
Configuring a VTP Version 3 Password 13-12
Configuring a VTP Version 3 Primary Server 13-13
Enabling the VTP Version 13-13
Enabling VTP Pruning 13-14
Configuring VTP on a Per-Port Basis 13-15
Adding a VTP Client Switch to a VTP Domain 13-15
Monitoring VTP
CHAPTER
14
13-16
Configuring Voice VLAN
14-1
Understanding Voice VLAN 14-1
Cisco IP Phone Voice Traffic 14-2
Cisco IP Phone Data Traffic 14-2
Configuring Voice VLAN 14-3
Default Voice VLAN Configuration 14-3
Voice VLAN Configuration Guidelines 14-3
Configuring a Port Connected to a Cisco 7960 IP Phone 14-4
Configuring Cisco IP Phone Voice Traffic 14-5
Configuring the Priority of Incoming Data Frames 14-6
Displaying Voice VLAN
14-7
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CHAPTER
15
Configuring Private VLANs
15-1
Understanding Private VLANs 15-1
IP Addressing Scheme with Private VLANs 15-3
Private VLANs across Multiple Switches 15-4
Private-VLAN Interaction with Other Features 15-4
Private VLANs and Unicast, Broadcast, and Multicast Traffic
Private VLANs and SVIs 15-5
15-5
Configuring Private VLANs 15-5
Tasks for Configuring Private VLANs 15-6
Default Private-VLAN Configuration 15-6
Private-VLAN Configuration Guidelines 15-6
Secondary and Primary VLAN Configuration 15-7
Private-VLAN Port Configuration 15-8
Limitations with Other Features 15-8
Configuring and Associating VLANs in a Private VLAN 15-9
Configuring a Layer 2 Interface as a Private-VLAN Host Port 15-11
Configuring a Layer 2 Interface as a Private-VLAN Promiscuous Port 15-12
Mapping Secondary VLANs to a Primary VLAN Layer 3 VLAN Interface 15-13
Monitoring Private VLANs
CHAPTER
16
15-14
Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling
Understanding IEEE 802.1Q Tunneling
16-1
16-1
Configuring IEEE 802.1Q Tunneling 16-4
Default IEEE 802.1Q Tunneling Configuration 16-4
IEEE 802.1Q Tunneling Configuration Guidelines 16-4
Native VLANs 16-4
System MTU 16-5
IEEE 802.1Q Tunneling and Other Features 16-6
Configuring an IEEE 802.1Q Tunneling Port 16-6
Understanding Layer 2 Protocol Tunneling
16-7
Configuring Layer 2 Protocol Tunneling 16-10
Default Layer 2 Protocol Tunneling Configuration 16-11
Layer 2 Protocol Tunneling Configuration Guidelines 16-11
Configuring Layer 2 Protocol Tunneling 16-13
Configuring Layer 2 Tunneling for EtherChannels 16-14
Configuring the SP Edge Switch 16-14
Configuring the Customer Switch 16-16
Monitoring and Maintaining Tunneling Status
16-18
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17
Configuring STP
17-1
Understanding Spanning-Tree Features 17-1
STP Overview 17-2
Spanning-Tree Topology and BPDUs 17-3
Bridge ID, Switch Priority, and Extended System ID 17-4
Spanning-Tree Interface States 17-4
Blocking State 17-5
Listening State 17-6
Learning State 17-6
Forwarding State 17-6
Disabled State 17-7
How a Switch or Port Becomes the Root Switch or Root Port 17-7
Spanning Tree and Redundant Connectivity 17-8
Spanning-Tree Address Management 17-8
Accelerated Aging to Retain Connectivity 17-8
Spanning-Tree Modes and Protocols 17-9
Supported Spanning-Tree Instances 17-9
Spanning-Tree Interoperability and Backward Compatibility 17-10
STP and IEEE 802.1Q Trunks 17-10
Configuring Spanning-Tree Features 17-10
Default Spanning-Tree Configuration 17-11
Spanning-Tree Configuration Guidelines 17-12
Changing the Spanning-Tree Mode. 17-13
Disabling Spanning Tree 17-14
Configuring the Root Switch 17-14
Configuring a Secondary Root Switch 17-16
Configuring Port Priority 17-16
Configuring Path Cost 17-18
Configuring the Switch Priority of a VLAN 17-19
Configuring Spanning-Tree Timers 17-20
Configuring the Hello Time 17-20
Configuring the Forwarding-Delay Time for a VLAN 17-21
Configuring the Maximum-Aging Time for a VLAN 17-21
Configuring the Transmit Hold-Count 17-22
Displaying the Spanning-Tree Status
CHAPTER
18
Configuring MSTP
17-22
18-1
Understanding MSTP 18-2
Multiple Spanning-Tree Regions
18-2
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IST, CIST, and CST 18-3
Operations Within an MST Region 18-3
Operations Between MST Regions 18-4
IEEE 802.1s Terminology 18-5
Hop Count 18-5
Boundary Ports 18-6
IEEE 802.1s Implementation 18-6
Port Role Naming Change 18-7
Interoperation Between Legacy and Standard Switches
Detecting Unidirectional Link Failure 18-8
Interoperability with IEEE 802.1D STP 18-8
18-7
Understanding RSTP 18-8
Port Roles and the Active Topology 18-9
Rapid Convergence 18-10
Synchronization of Port Roles 18-11
Bridge Protocol Data Unit Format and Processing 18-12
Processing Superior BPDU Information 18-13
Processing Inferior BPDU Information 18-13
Topology Changes 18-13
Configuring MSTP Features 18-14
Default MSTP Configuration 18-14
MSTP Configuration Guidelines 18-15
Specifying the MST Region Configuration and Enabling MSTP
Configuring the Root Switch 18-17
Configuring a Secondary Root Switch 18-19
Configuring Port Priority 18-19
Configuring Path Cost 18-20
Configuring the Switch Priority 18-21
Configuring the Hello Time 18-22
Configuring the Forwarding-Delay Time 18-23
Configuring the Maximum-Aging Time 18-23
Configuring the Maximum-Hop Count 18-24
Specifying the Link Type to Ensure Rapid Transitions 18-24
Designating the Neighbor Type 18-25
Restarting the Protocol Migration Process 18-25
Displaying the MST Configuration and Status
CHAPTER
19
Configuring Optional Spanning-Tree Features
Understanding Optional Spanning-Tree Features
18-16
18-26
19-1
19-1
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Understanding Port Fast 19-2
Understanding BPDU Guard 19-2
Understanding BPDU Filtering 19-3
Understanding UplinkFast 19-3
Understanding BackboneFast 19-5
Understanding EtherChannel Guard 19-7
Understanding Root Guard 19-8
Understanding Loop Guard 19-9
Configuring Optional Spanning-Tree Features 19-9
Default Optional Spanning-Tree Configuration 19-9
Optional Spanning-Tree Configuration Guidelines 19-10
Enabling Port Fast 19-10
Enabling BPDU Guard 19-11
Enabling BPDU Filtering 19-12
Enabling UplinkFast for Use with Redundant Links 19-13
Enabling BackboneFast 19-13
Enabling EtherChannel Guard 19-14
Enabling Root Guard 19-15
Enabling Loop Guard 19-15
Displaying the Spanning-Tree Status
CHAPTER
20
19-16
Configuring Flex Links and the MAC Address-Table Move Update Feature
Understanding Flex Links and the MAC Address-Table Move Update
Flex Links 20-1
VLAN Flex Link Load Balancing and Support 20-2
Flex Link Multicast Fast Convergence 20-3
Learning the Other Flex Link Port as the mrouter Port 20-3
Generating IGMP Reports 20-3
Leaking IGMP Reports 20-4
MAC Address-Table Move Update 20-6
20-1
20-1
Configuring Flex Links and MAC Address-Table Move Update 20-7
Configuration Guidelines 20-8
Default Configuration 20-8
Configuring Flex Links 20-9
Configuring VLAN Load Balancing on Flex Links 20-10
Configuring the MAC Address-Table Move Update Feature 20-12
Monitoring Flex Links and the MAC Address-Table Move Update Information
20-14
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CHAPTER
21
Configuring DHCP Features and IP Source Guard
21-1
Understanding DHCP Features 21-1
DHCP Server 21-2
DHCP Relay Agent 21-2
DHCP Snooping 21-2
Option-82 Data Insertion 21-3
Cisco IOS DHCP Server Database 21-6
DHCP Snooping Binding Database 21-6
Configuring DHCP Features 21-7
Default DHCP Configuration 21-8
DHCP Snooping Configuration Guidelines 21-8
Configuring the DHCP Server 21-9
Configuring the DHCP Relay Agent 21-10
Specifying the Packet Forwarding Address 21-10
Enabling DHCP Snooping and Option 82 21-11
Enabling DHCP Snooping on Private VLANs 21-13
Enabling the Cisco IOS DHCP Server Database 21-13
Enabling the DHCP Snooping Binding Database Agent 21-14
Displaying DHCP Snooping Information
21-15
Understanding IP Source Guard 21-15
Source IP Address Filtering 21-16
Source IP and MAC Address Filtering 21-16
IP Source Guard for Static Hosts 21-16
Configuring IP Source Guard 21-17
Default IP Source Guard Configuration 21-17
IP Source Guard Configuration Guidelines 21-17
Enabling IP Source Guard 21-18
Configuring IP Source Guard for Static Hosts 21-19
Configuring IP Source Guard for Static Hosts on a Layer 2 Access Port 21-19
Configuring IP Source Guard for Static Hosts on a Private VLAN Host Port 21-23
Displaying IP Source Guard Information
21-25
Understanding DHCP Server Port-Based Address Allocation
21-25
Configuring DHCP Server Port-Based Address Allocation 21-25
Default Port-Based Address Allocation Configuration 21-25
Port-Based Address Allocation Configuration Guidelines 21-26
Enabling DHCP Server Port-Based Address Allocation 21-26
Displaying DHCP Server Port-Based Address Allocation
21-28
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CHAPTER
22
Configuring Dynamic ARP Inspection
22-1
Understanding Dynamic ARP Inspection 22-1
Interface Trust States and Network Security 22-3
Rate Limiting of ARP Packets 22-4
Relative Priority of ARP ACLs and DHCP Snooping Entries
Logging of Dropped Packets 22-4
Configuring Dynamic ARP Inspection 22-5
Default Dynamic ARP Inspection Configuration 22-5
Dynamic ARP Inspection Configuration Guidelines 22-6
Configuring Dynamic ARP Inspection in DHCP Environments
Configuring ARP ACLs for Non-DHCP Environments 22-8
Limiting the Rate of Incoming ARP Packets 22-10
Performing Validation Checks 22-12
Configuring the Log Buffer 22-13
Displaying Dynamic ARP Inspection Information
CHAPTER
23
Configuring IGMP Snooping and MVR
22-4
22-7
22-14
23-1
Understanding IGMP Snooping 23-1
IGMP Versions 23-2
Joining a Multicast Group 23-3
Leaving a Multicast Group 23-5
Immediate Leave 23-5
IGMP Configurable-Leave Timer 23-5
IGMP Report Suppression 23-6
Configuring IGMP Snooping 23-6
Default IGMP Snooping Configuration 23-6
Enabling or Disabling IGMP Snooping 23-7
Setting the Snooping Method 23-8
Configuring a Multicast Router Port 23-9
Configuring a Blade Server Statically to Join a Group 23-9
Enabling IGMP Immediate Leave 23-10
Configuring the IGMP Leave Timer 23-11
Configuring TCN-Related Commands 23-11
Controlling the Multicast Flooding Time After a TCN Event
Recovering from Flood Mode 23-12
Disabling Multicast Flooding During a TCN Event 23-13
Configuring the IGMP Snooping Querier 23-13
Disabling IGMP Report Suppression 23-15
Displaying IGMP Snooping Information
23-12
23-16
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Understanding Multicast VLAN Registration 23-17
Using MVR in a Multicast Television Application
Configuring MVR 23-19
Default MVR Configuration 23-19
MVR Configuration Guidelines and Limitations
Configuring MVR Global Parameters 23-20
Configuring MVR Interfaces 23-21
Displaying MVR Information
23-17
23-20
23-23
Configuring IGMP Filtering and Throttling 23-23
Default IGMP Filtering and Throttling Configuration 23-24
Configuring IGMP Profiles 23-24
Applying IGMP Profiles 23-26
Setting the Maximum Number of IGMP Groups 23-26
Configuring the IGMP Throttling Action 23-27
Displaying IGMP Filtering and Throttling Configuration
CHAPTER
24
Configuring Port-Based Traffic Control
23-28
24-1
Configuring Storm Control 24-1
Understanding Storm Control 24-1
Default Storm Control Configuration 24-3
Configuring Storm Control and Threshold Levels
Configuring Small-Frame Arrival Rate 24-5
24-3
Configuring Protected Ports 24-6
Default Protected Port Configuration 24-6
Protected Port Configuration Guidelines 24-7
Configuring a Protected Port 24-7
Configuring Port Blocking 24-7
Default Port Blocking Configuration 24-8
Blocking Flooded Traffic on an Interface 24-8
Configuring Port Security 24-8
Understanding Port Security 24-9
Secure MAC Addresses 24-9
Security Violations 24-10
Default Port Security Configuration 24-11
Port Security Configuration Guidelines 24-11
Enabling and Configuring Port Security 24-13
Enabling and Configuring Port Security Aging 24-17
Port Security and Private VLANs 24-18
Configuring Protocol Storm Protection
24-19
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Understanding Protocol Storm Protection 24-19
Default Protocol Storm Protection Configuration 24-20
Enabling Protocol Storm Protection 24-20
Displaying Port-Based Traffic Control Settings
CHAPTER
25
Configuring CDP
24-21
25-1
Understanding CDP
25-1
Configuring CDP 25-2
Default CDP Configuration 25-2
Configuring the CDP Characteristics 25-2
Disabling and Enabling CDP 25-3
Disabling and Enabling CDP on an Interface
Monitoring and Maintaining CDP
CHAPTER
26
25-4
25-5
Configuring LLDP, LLDP-MED, and Wired Location Service
26-1
Understanding LLDP, LLDP-MED, and Wired Location Service
LLDP 26-1
LLDP-MED 26-2
Wired Location Service 26-3
26-1
Configuring LLDP, LLDP-MED, and Wired Location Service
Default LLDP Configuration 26-4
Configuration Guidelines 26-5
Enabling LLDP 26-5
Configuring LLDP Characteristics 26-6
Configuring LLDP-MED TLVs 26-6
Configuring Network-Policy TLV 26-7
Configuring Location TLV and Wired Location Service
26-4
26-9
Monitoring and Maintaining LLDP, LLDP-MED, and Wired Location Service
CHAPTER
27
Configuring UDLD
26-10
27-1
Understanding UDLD 27-1
Modes of Operation 27-1
Methods to Detect Unidirectional Links
27-2
Configuring UDLD 27-4
Default UDLD Configuration 27-4
Configuration Guidelines 27-4
Enabling UDLD Globally 27-5
Enabling UDLD on an Interface 27-5
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Resetting an Interface Disabled by UDLD
Displaying UDLD Status
CHAPTER
28
27-6
27-6
Configuring SPAN and RSPAN
28-1
Understanding SPAN and RSPAN 28-1
Local SPAN 28-2
Remote SPAN 28-2
SPAN and RSPAN Concepts and Terminology 28-3
SPAN Sessions 28-3
Monitored Traffic 28-4
Source Ports 28-5
Source VLANs 28-6
VLAN Filtering 28-6
Destination Port 28-7
RSPAN VLAN 28-8
SPAN and RSPAN Interaction with Other Features 28-8
Configuring SPAN and RSPAN 28-9
Default SPAN and RSPAN Configuration 28-9
Configuring Local SPAN 28-10
SPAN Configuration Guidelines 28-10
Creating a Local SPAN Session 28-11
Creating a Local SPAN Session and Configuring Incoming Traffic 28-13
Specifying VLANs to Filter 28-14
Configuring RSPAN 28-15
RSPAN Configuration Guidelines 28-15
Configuring a VLAN as an RSPAN VLAN 28-16
Creating an RSPAN Source Session 28-17
Creating an RSPAN Destination Session 28-19
Creating an RSPAN Destination Session and Configuring Incoming Traffic
Specifying VLANs to Filter 28-22
Displaying SPAN and RSPAN Status
CHAPTER
29
Configuring RMON
28-20
28-23
29-1
Understanding RMON
29-1
Configuring RMON 29-3
Default RMON Configuration 29-3
Configuring RMON Alarms and Events 29-3
Collecting Group History Statistics on an Interface 29-5
Collecting Group Ethernet Statistics on an Interface 29-6
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Displaying RMON Status
CHAPTER
30
29-6
Configuring System Message Logging
30-1
Understanding System Message Logging
30-1
Configuring System Message Logging 30-2
System Log Message Format 30-2
Default System Message Logging Configuration 30-3
Disabling Message Logging 30-4
Setting the Message Display Destination Device 30-4
Synchronizing Log Messages 30-5
Enabling and Disabling Time Stamps on Log Messages 30-7
Enabling and Disabling Sequence Numbers in Log Messages 30-7
Defining the Message Severity Level 30-8
Limiting Syslog Messages Sent to the History Table and to SNMP 30-9
Enabling the Configuration-Change Logger 30-10
Configuring UNIX Syslog Servers 30-11
Logging Messages to a UNIX Syslog Daemon 30-11
Configuring the UNIX System Logging Facility 30-12
Displaying the Logging Configuration
CHAPTER
31
Configuring SNMP
30-13
31-1
Understanding SNMP 31-1
SNMP Versions 31-2
SNMP Manager Functions 31-3
SNMP Agent Functions 31-4
SNMP Community Strings 31-4
Using SNMP to Access MIB Variables 31-4
SNMP Notifications 31-5
SNMP ifIndex MIB Object Values 31-5
Configuring SNMP 31-6
Default SNMP Configuration 31-6
SNMP Configuration Guidelines 31-6
Disabling the SNMP Agent 31-7
Configuring Community Strings 31-8
Configuring SNMP Groups and Users 31-9
Configuring SNMP Notifications 31-12
Setting the CPU Threshold Notification Types and Values 31-16
Setting the Agent Contact and Location Information 31-16
Limiting TFTP Servers Used Through SNMP 31-17
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SNMP Examples
31-17
Displaying SNMP Status
CHAPTER
32
31-19
Configuring Embedded Event Manager
32-1
Understanding Embedded Event Manager 32-1
Event Detectors 32-2
Embedded Event Manager Actions 32-4
Embedded Event Manager Policies 32-4
Embedded Event Manager Environment Variables
EEM 3.2 32-5
32-5
Configuring Embedded Event Manager 32-6
Registering and Defining an Embedded Event Manager Applet 32-6
Registering and Defining an Embedded Event Manager TCL Script 32-7
Displaying Embedded Event Manager Information
CHAPTER
33
Configuring Network Security with ACLs
32-7
33-1
Understanding ACLs 33-2
Supported ACLs 33-2
Port ACLs 33-3
Router ACLs 33-4
VLAN Maps 33-5
Handling Fragmented and Unfragmented Traffic
33-5
Configuring IPv4 ACLs 33-6
Creating Standard and Extended IPv4 ACLs 33-7
Access List Numbers 33-8
ACL Logging 33-8
Creating a Numbered Standard ACL 33-9
Creating a Numbered Extended ACL 33-10
Resequencing ACEs in an ACL 33-14
Creating Named Standard and Extended ACLs 33-14
Using Time Ranges with ACLs 33-16
Including Comments in ACLs 33-18
Applying an IPv4 ACL to a Terminal Line 33-18
Applying an IPv4 ACL to an Interface 33-19
Hardware and Software Treatment of IP ACLs 33-21
Troubleshooting ACLs 33-21
IPv4 ACL Configuration Examples 33-22
Numbered ACLs 33-24
Extended ACLs 33-24
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Named ACLs 33-24
Time Range Applied to an IP ACL 33-25
Commented IP ACL Entries 33-25
ACL Logging 33-26
Creating Named MAC Extended ACLs 33-27
Applying a MAC ACL to a Layer 2 Interface
33-28
Configuring VLAN Maps 33-29
VLAN Map Configuration Guidelines 33-30
Creating a VLAN Map 33-31
Examples of ACLs and VLAN Maps 33-32
Applying a VLAN Map to a VLAN 33-34
Using VLAN Maps in Your Network 33-34
Wiring Closet Configuration 33-34
Denying Access to a Server on Another VLAN
Configuring VACL Logging 33-37
33-36
Using VLAN Maps with Router ACLs 33-38
VLAN Maps and Router ACL Configuration Guidelines 33-38
Examples of Router ACLs and VLAN Maps Applied to VLANs 33-39
ACLs and Switched Packets 33-39
ACLs and Routed Packets 33-40
Displaying IPv4 ACL Configuration
CHAPTER
34
Configuring QoS
33-41
34-1
Understanding QoS 34-1
Basic QoS Model 34-3
Classification 34-5
Classification Based on QoS ACLs 34-7
Classification Based on Class Maps and Policy Maps
Policing and Marking 34-8
Policing on Physical Ports 34-9
Policing on SVIs 34-10
Mapping Tables 34-12
Queueing and Scheduling Overview 34-13
Weighted Tail Drop 34-13
SRR Shaping and Sharing 34-14
Queueing and Scheduling on Ingress Queues 34-15
Queueing and Scheduling on Egress Queues 34-17
Packet Modification 34-19
Configuring Auto-QoS
34-7
34-20
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Generated Auto-QoS Configuration 34-21
VOIP Device Specifics 34-21
Enhanced Auto-QoS for Video, Trust, and Classification 34-22
Auto-QoS Configuration Migration 34-22
Auto-QoS Generated Configuration For VoIP Devices 34-26
Auto-QoS Generated Configuration For Enhanced Video, Trust, and Classify Devices
Effects of Auto-QoS on the Configuration 34-30
Auto-QoS Configuration Guidelines 34-30
Auto-QoS VoIP Considerations 34-31
Auto-QoS Enhanced Considerations 34-31
Enabling Auto-QoS 34-31
Troubleshooting Auto QoS Commands 34-32
Displaying Auto-QoS Information
34-27
34-33
Configuring Standard QoS 34-33
Default Standard QoS Configuration 34-34
Default Ingress Queue Configuration 34-34
Default Egress Queue Configuration 34-35
Default Mapping Table Configuration 34-36
Standard QoS Configuration Guidelines 34-36
QoS ACL Guidelines 34-36
Applying QoS on Interfaces 34-37
Policing Guidelines 34-37
General QoS Guidelines 34-38
Enabling QoS Globally 34-38
Enabling VLAN-Based QoS on Physical Ports 34-39
Configuring Classification Using Port Trust States 34-39
Configuring the Trust State on Ports within the QoS Domain 34-39
Configuring the CoS Value for an Interface 34-41
Configuring a Trusted Boundary to Ensure Port Security 34-42
Enabling DSCP Transparency Mode 34-43
Configuring the DSCP Trust State on a Port Bordering Another QoS Domain 34-44
Configuring a QoS Policy 34-46
Classifying Traffic by Using ACLs 34-47
Classifying Traffic by Using Class Maps 34-50
Classifying, Policing, and Marking Traffic on Physical Ports by Using Policy Maps 34-52
Classifying, Policing, and Marking Traffic on SVIs by Using Hierarchical Policy Maps 34-56
Classifying, Policing, and Marking Traffic by Using Aggregate Policers 34-63
Configuring DSCP Maps 34-65
Configuring the CoS-to-DSCP Map 34-66
Configuring the IP-Precedence-to-DSCP Map 34-67
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Configuring the Policed-DSCP Map 34-68
Configuring the DSCP-to-CoS Map 34-69
Configuring the DSCP-to-DSCP-Mutation Map 34-70
Configuring Ingress Queue Characteristics 34-71
Mapping DSCP or CoS Values to an Ingress Queue and Setting WTD Thresholds 34-72
Allocating Buffer Space Between the Ingress Queues 34-73
Allocating Bandwidth Between the Ingress Queues 34-74
Configuring the Ingress Priority Queue 34-75
Configuring Egress Queue Characteristics 34-76
Configuration Guidelines 34-76
Allocating Buffer Space to and Setting WTD Thresholds for an Egress Queue-Set 34-77
Mapping DSCP or CoS Values to an Egress Queue and to a Threshold ID 34-79
Configuring SRR Shaped Weights on Egress Queues 34-80
Configuring SRR Shared Weights on Egress Queues 34-81
Configuring the Egress Expedite Queue 34-82
Limiting the Bandwidth on an Egress Interface 34-82
Displaying Standard QoS Information
CHAPTER
35
34-83
Configuring EtherChannels and Layer 2 Trunk Failover
35-1
Understanding EtherChannels 35-1
EtherChannel Overview 35-2
Port-Channel Interfaces 35-3
Port Aggregation Protocol 35-4
PAgP Modes 35-4
PAgP Interaction with Virtual Switches and Dual-Active Detection
PAgP Interaction with Other Features 35-5
Link Aggregation Control Protocol 35-5
LACP Modes 35-6
LACP Interaction with Other Features 35-6
EtherChannel On Mode 35-6
Load Balancing and Forwarding Methods 35-7
35-5
Configuring EtherChannels 35-8
Default EtherChannel Configuration 35-9
EtherChannel Configuration Guidelines 35-9
Configuring Layer 2 EtherChannels 35-11
Configuring Layer 3 EtherChannels 35-13
Creating Port-Channel Logical Interfaces 35-13
Configuring the Physical Interfaces 35-14
Configuring EtherChannel Load Balancing 35-16
Configuring the PAgP Learn Method and Priority 35-17
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Configuring LACP Hot-Standby Ports 35-18
Configuring the LACP System Priority 35-19
Configuring the LACP Port Priority 35-20
Displaying EtherChannel, PAgP, and LACP Status
35-21
Understanding Layer 2 Trunk Failover 35-21
Configuring Layer 2 Trunk Failover 35-22
Default Layer 2 Trunk Failover Configuration 35-22
Layer 2 Trunk Failover Configuration Guidelines 35-23
Configuring Layer 2 Trunk Failover 35-23
Displaying Layer 2 Trunk Failover Status 35-24
CHAPTER
36
Configuring IP Unicast Routing
36-1
Understanding IP Routing 36-1
Types of Routing 36-2
Steps for Configuring Routing
36-3
Configuring IP Addressing 36-3
Default Addressing Configuration 36-4
Assigning IP Addresses to Network Interfaces 36-5
Use of Subnet Zero 36-5
Classless Routing 36-6
Configuring Address Resolution Methods 36-7
Define a Static ARP Cache 36-8
Set ARP Encapsulation 36-9
Enable Proxy ARP 36-9
Routing Assistance When IP Routing is Disabled 36-10
Proxy ARP 36-10
Default Gateway 36-10
ICMP Router Discovery Protocol (IRDP) 36-11
Configuring Broadcast Packet Handling 36-12
Enabling Directed Broadcast-to-Physical Broadcast Translation
Forwarding UDP Broadcast Packets and Protocols 36-13
Establishing an IP Broadcast Address 36-14
Flooding IP Broadcasts 36-15
Monitoring and Maintaining IP Addressing 36-16
Enabling IP Unicast Routing
36-12
36-17
Configuring RIP 36-17
Default RIP Configuration 36-18
Configuring Basic RIP Parameters 36-19
Configuring RIP Authentication 36-20
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Configuring Summary Addresses and Split Horizon
Configuring Split Horizon 36-22
36-21
Configuring OSPF for Routed Access 36-23
Default OSPF Configuration 36-24
Configuring Basic OSPF Parameters 36-25
Configuring OSPF Interfaces 36-26
Configuring OSPF Area Parameters 36-27
Configuring Other OSPF Parameters 36-28
Changing LSA Group Pacing 36-30
Configuring a Loopback Interface 36-30
Monitoring OSPF 36-31
Configuring Stub Routing 36-32
Understanding PIM Stub Routing 36-32
Configuring PIM Stub Routing 36-33
PIM Stub Routing Configuration Guidelines
Enabling PIM Stub Routing 36-33
Understanding EIGRP Stub Routing 36-35
Configuring EIGRP Stub Routing 36-36
36-33
Configuring Protocol-Independent Features 36-37
Configuring Cisco Express Forwarding 36-37
Configuring the Number of Equal-Cost Routing Paths 36-38
Configuring Static Unicast Routes 36-39
Specifying Default Routes and Networks 36-40
Using Route Maps to Redistribute Routing Information 36-41
Filtering Routing Information 36-43
Setting Passive Interfaces 36-43
Controlling Advertising and Processing in Routing Updates 36-44
Filtering Sources of Routing Information 36-44
Managing Authentication Keys 36-45
To remove the key chain, use the no key chain name-of-chain global configuration
command. 36-46
User Interface for VRF-Aware RADIUS
36-46
Monitoring and Maintaining the IP Network
CHAPTER
37
Configuring IPv6 Unicast Routing
36-46
37-1
Understanding IPv6 37-1
IPv6 Addresses 37-2
Supported IPv6 Unicast Host Features 37-2
128-Bit Wide Unicast Addresses 37-3
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DNS for IPv6 37-3
Path MTU Discovery for IPv6 Unicast 37-3
ICMPv6 37-4
Neighbor Discovery 37-4
Default Router Preference 37-4
IPv6 Stateless Autoconfiguration and Duplicate Address Detection
IPv6 Applications 37-5
Dual IPv4 and IPv6 Protocol Stacks 37-5
DHCP for IPv6 Address Assignment 37-6
Static Routes for IPv6 37-6
RIP for IPv6 37-6
SNMP and Syslog Over IPv6 37-7
HTTP(S) Over IPv6 37-7
Unsupported IPv6 Unicast Routing Features 37-7
Limitations 37-8
Configuring IPv6 37-9
Default IPv6 Configuration 37-9
Configuring IPv6 Addressing and Enabling IPv6 Routing
Configuring Default Router Preference 37-12
Configuring IPv4 and IPv6 Protocol Stacks 37-12
Configuring IPv6 ICMP Rate Limiting 37-14
Configuring CEF for IPv6 37-14
Configuring Static Routes for IPv6 37-15
Configuring RIP for IPv6 37-16
Displaying IPv6
CHAPTER
38
37-4
37-9
37-17
Configuring IPv6 MLD Snooping
38-1
Understanding MLD Snooping 38-1
MLD Messages 38-2
MLD Queries 38-3
Multicast Client Aging Robustness 38-3
Multicast Router Discovery 38-3
MLD Reports 38-4
MLD Done Messages and Immediate-Leave 38-4
Topology Change Notification Processing 38-5
Configuring IPv6 MLD Snooping 38-5
Default MLD Snooping Configuration 38-5
MLD Snooping Configuration Guidelines 38-6
Enabling or Disabling MLD Snooping 38-6
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Configuring a Static Multicast Group 38-8
Configuring a Multicast Router Port 38-8
Enabling MLD Immediate Leave 38-9
Configuring MLD Snooping Queries 38-10
Disabling MLD Listener Message Suppression
Displaying MLD Snooping Information
CHAPTER
39
Configuring IPv6 ACLs
38-11
38-11
39-1
Understanding IPv6 ACLs 39-1
Supported ACL Features 39-2
IPv6 ACL Limitations 39-2
Configuring IPv6 ACLs 39-3
Default IPv6 ACL Configuration 39-3
Interaction with Other Features 39-3
Creating IPv6 ACLs 39-4
Applying an IPv6 ACL to an Interface 39-6
Displaying IPv6 ACLs
CHAPTER
40
39-7
Configuring HSRP, VRRP, and Enhanced Object Tracking
40-1
Understanding HSRP 40-1
HSRP Versions 40-3
Multiple HSRP 40-4
Configuring HSRP 40-5
Default HSRP Configuration 40-5
HSRP Configuration Guidelines 40-5
Enabling HSRP 40-6
Configuring HSRP Priority 40-7
Configuring MHSRP 40-9
Configuring HSRP Authentication and Timers 40-10
Enabling HSRP Support for ICMP Redirect Messages
Displaying HSRP Configurations
40-11
40-11
Configuring VRRP 40-12
VRRP Limitations 40-12
Configuring Enhanced Object Tracking 40-12
Understanding Enhanced Object Tracking 40-13
Configuring Enhanced Object Tracking Features 40-13
Tracking Interface Line-Protocol or IP Routing State
Configuring a Tracked List 40-14
40-13
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Configuring HSRP Object Tracking 40-18
Configuring Other Tracking Characteristics
Monitoring Enhanced Object Tracking 40-19
CHAPTER
41
Configuring Cisco IOS IP SLAs Operations
40-19
41-1
Understanding Cisco IOS IP SLAs 41-1
Using Cisco IOS IP SLAs to Measure Network Performance
IP SLAs Responder and IP SLAs Control Protocol 41-4
Response Time Computation for IP SLAs 41-4
Configuring IP SLAs Operations 41-5
Default Configuration 41-5
Configuration Guidelines 41-5
Configuring the IP SLAs Responder
Monitoring IP SLAs Operations
CHAPTER
42
Troubleshooting
41-3
41-6
41-6
42-1
Recovering from a Software Failure
42-2
Recovering from a Lost or Forgotten Password 42-4
Procedure with Password Recovery Enabled 42-5
Procedure with Password Recovery Disabled 42-7
Preventing Autonegotiation Mismatches
SFP Module Security and Identification
Monitoring SFP Module Status
42-8
42-9
42-9
Using Ping 42-9
Understanding Ping 42-10
Executing Ping 42-10
Using Layer 2 Traceroute 42-11
Understanding Layer 2 Traceroute 42-11
Usage Guidelines 42-11
Displaying the Physical Path 42-13
Using IP Traceroute 42-13
Understanding IP Traceroute 42-13
Executing IP Traceroute 42-14
Using Debug Commands 42-15
Enabling Debugging on a Specific Feature 42-15
Enabling All-System Diagnostics 42-16
Redirecting Debug and Error Message Output 42-16
Using the show platform forward Command
42-16
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Using the crashinfo Files 42-18
Basic crashinfo Files 42-19
Extended crashinfo Files 42-19
Memory Consistency Check Routines 42-19
Displaying TCAM Memory Consistency Check Errors
Troubleshooting CPU Utilization 42-21
Possible Symptoms of High CPU Utilization
Verifying the Problem and Cause 42-21
CHAPTER
43
Configuring Online Diagnostics
42-21
43-1
Understanding How Online Diagnostics Work
Scheduling Online Diagnostics
42-20
43-1
43-1
Configuring Health-Monitoring Diagnostics
43-2
Running Online Diagnostic Tests 43-3
Starting Online Diagnostic Tests 43-3
Displaying Online Diagnostic Tests and Test Results
APPENDIX
44
43-3
Working with the Cisco IOS File System, Configuration Files, and Software Images
Working with the Flash File System 44-1
Displaying Available File Systems 44-2
Setting the Default File System 44-3
Displaying Information about Files on a File System 44-3
Changing Directories and Displaying the Working Directory
Creating and Removing Directories 44-4
Copying Files 44-4
Deleting Files 44-5
Creating, Displaying, and Extracting tar Files 44-5
Creating a tar File 44-6
Displaying the Contents of a tar File 44-6
Extracting a tar File 44-8
Displaying the Contents of a File 44-8
44-1
44-3
Working with Configuration Files 44-8
Guidelines for Creating and Using Configuration Files 44-9
Configuration File Types and Location 44-10
Creating a Configuration File By Using a Text Editor 44-10
Copying Configuration Files By Using TFTP 44-10
Preparing to Download or Upload a Configuration File By Using TFTP
Downloading the Configuration File By Using TFTP 44-11
44-11
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Uploading the Configuration File By Using TFTP 44-12
Copying Configuration Files By Using FTP 44-12
Preparing to Download or Upload a Configuration File By Using FTP 44-13
Downloading a Configuration File By Using FTP 44-13
Uploading a Configuration File By Using FTP 44-14
Copying Configuration Files By Using RCP 44-15
Preparing to Download or Upload a Configuration File By Using RCP 44-16
Downloading a Configuration File By Using RCP 44-17
Uploading a Configuration File By Using RCP 44-18
Clearing Configuration Information 44-18
Clearing the Startup Configuration File 44-19
Deleting a Stored Configuration File 44-19
Replacing and Rolling Back Configurations 44-19
Understanding Configuration Replacement and Rollback 44-19
Configuration Guidelines 44-20
Configuring the Configuration Archive 44-21
Performing a Configuration Replacement or Rollback Operation 44-22
Working with Software Images 44-23
Image Location on the Switch 44-23
tar File Format of Images on a Server or Cisco.com 44-24
Copying Image Files By Using TFTP 44-25
Preparing to Download or Upload an Image File By Using TFTP 44-25
Downloading an Image File By Using TFTP 44-26
Uploading an Image File By Using TFTP 44-27
Copying Image Files By Using FTP 44-28
Preparing to Download or Upload an Image File By Using FTP 44-28
Downloading an Image File By Using FTP 44-29
Uploading an Image File By Using FTP 44-31
Copying Image Files By Using RCP 44-32
Preparing to Download or Upload an Image File By Using RCP 44-32
Downloading an Image File By Using RCP 44-34
Uploading an Image File By Using RCP 44-35
APPENDIX
45
Unsupported Commands in Cisco IOS Release 15.0(2)SE
45-1
Access Control Lists 45-1
Unsupported Privileged EXEC Commands 45-1
Unsupported Global Configuration Commands 45-1
Unsupported Route-Map Configuration Command 45-1
Archive Commands
45-2
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Unsupported Privileged EXEC Commands
45-2
ARP Commands 45-2
Unsupported Global Configuration Commands 45-2
Unsupported Interface Configuration Commands 45-2
Bootloader Commands 45-2
Unsupported user EXEC Command 45-2
Unsupported Global Configuration Command
Debug Commands 45-3
Unsupported Privileged EXEC Commands
45-2
45-3
Embedded Syslog Manager 45-3
Unsupported Global Configuration Commands 45-3
Unsupported Privileged EXEC Commands 45-3
HSRP 45-3
Unsupported Global Configuration Commands 45-3
Unsupported Interface Configuration Commands 45-3
IGMP Snooping Commands 45-4
Unsupported Global Configuration Command
45-4
Interface Commands 45-4
Unsupported Privileged EXEC Command 45-4
Unsupported Global Configuration Command 45-4
Unsupported Interface Configuration Command 45-4
IP Unicast Routing 45-4
Unsupported Privileged EXEC or User EXEC Commands 45-4
Unsupported Global Configuration Commands 45-4
Unsupported Interface Configuration Commands 45-5
Unsupported Route Map Commands 45-5
MAC Address Commands 45-7
Unsupported Privileged EXEC Commands 45-7
Unsupported Global Configuration Commands 45-7
Miscellaneous 45-7
Unsupported User EXEC Commands 45-7
Unsupported Privileged EXEC Commands 45-7
Unsupported Global Configuration Commands 45-8
NetFlow Commands 45-8
Unsupported Global Configuration Commands
45-8
Network Address Translation (NAT) Commands 45-8
Unsupported Privileged EXEC Commands 45-8
QoS
45-8
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Unsupported Global Configuration Command 45-8
Unsupported Interface Configuration Commands 45-8
Unsupported Policy-Map Configuration Command 45-9
RADIUS 45-9
Unsupported Global Configuration Commands
45-9
SNMP 45-9
Unsupported Global Configuration Commands
45-9
Spanning Tree 45-9
Unsupported Global Configuration Command 45-9
Unsupported Interface Configuration Command 45-9
VLAN 45-10
Unsupported Global Configuration Command
Unsupported User EXEC Commands 45-10
VTP
45-10
45-10
Unsupported Privileged EXEC Command
45-10
INDEX
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Preface
Audience
This guide is for the networking professional managing the Cisco Catalyst Blade Switch 3030 for Dell,
referred to as the switch. Before using this guide, you should have experience working with the Cisco
IOS software and be familiar with the concepts and terminology of Ethernet and local area networking.
Purpose
The Layer 3 switch IP base image provides Layer 2+ features including access control lists (ACLs),
quality of service (QoS), static routing, EIGRP and PIM stub routing, and the Routing Information
Protocol (RIP).
This guide provides the information that you need to configure Cisco IOS software features on your
switch. The Cisco Catalyst Blade Switch 3030 for Dell software provides enterprise-class intelligent
services such as access control lists (ACLs) and quality of service (QoS) features.
This guide provides procedures for using the commands that have been created or changed for use with
the Cisco Catalyst Blade Switch 3030 for Dell switch. It does not provide detailed information about
these commands. For detailed information about these commands, see the Cisco Catalyst Blade
Switch 3030 for Dell Command Reference for this release. For information about the standard Cisco IOS
Release 15.0 commands, see the Cisco IOS documentation set available from the Cisco.com.
This guide does not provide detailed information on the graphical user interface (GUIs) for the
embedded device manager that you can use to manage the switch. However, the concepts in this guide
are applicable to the GUI user. For information about the device manager, see the switch online help.
This guide does not describe system messages you might encounter or how to install your switch. For
more information, see the Cisco Catalyst Blade Switch 3030 for Dell System Message Guide for this
release and the Cisco Catalyst Blade Switch 3030 for Dell Hardware Installation Guide.
For documentation updates, see the release notes for this release.
Conventions
This publication uses these conventions to convey instructions and information:
Command descriptions use these conventions:
•
Commands and keywords are in boldface text.
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•
Arguments for which you supply values are in italic.
•
Square brackets ([ ]) mean optional elements.
•
Braces ({ }) group required choices, and vertical bars ( | ) separate the alternative elements.
•
Braces and vertical bars within square brackets ([{ | }]) mean a required choice within an optional
element.
Interactive examples use these conventions:
•
Terminal sessions and system displays are in screen font.
•
Information you enter is in boldface screen font.
•
Nonprinting characters, such as passwords or tabs, are in angle brackets (< >).
Notes, cautions, and timesavers use these conventions and symbols:
Note
Caution
Means reader take note. Notes contain helpful suggestions or references to materials not contained in
this manual.
Means reader be careful. In this situation, you might do something that could result in equipment
damage or loss of data.
Related Publications
For more information about the switch, see the Cisco Catalyst Blade Switch 3030 for Dell
documentation on Cisco.com:
http://www.cisco.com/en/US/products/ps8742/tsd_products_support_series_home.html
Note
Before installing, configuring, or upgrading the switch, see these documents:
•
For initial configuration information, see the blade switch configuration and installation instructions
in the getting started guide or the “Configuring the Switch with the CLI-Based Setup Program”
appendix in the hardware installation guide.
•
For device manager requirements, see the “System Requirements” section in the release notes (not
orderable but available on Cisco.com).
•
For upgrading information, see the “Downloading Software” section in the release notes.
•
Release Notes for the Cisco Catalyst Blade Switch 3030 for Dell, Cisco IOS Release 12.2(50)SE
•
Cisco Catalyst Blade Switch 3030 for Dell System Message Guide
•
Cisco Catalyst Blade Switch 3030 for Dell Software Configuration Guide
•
Cisco Catalyst Blade Switch 3030 for Dell Command Reference
•
Device manager online help (available on the switch)
•
Cisco Catalyst Blade Switch 3030 for Dell Hardware Installation Guide
•
Cisco Catalyst Blade Switch 3030 for Dell Getting Started Guide
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•
Regulatory Compliance and Safety Information for the Cisco Catalyst Blade Switch 3030 for Dell
•
Cisco Small Form-Factor Pluggable Modules Installation Notes
•
These compatibility matrix documents are available from this Cisco.com site:
http://www.cisco.com/en/US/products/hw/modules/ps5455/products_device_support_tables_list.ht
ml
– Cisco Gigabit Ethernet Transceiver Modules Compatibility Matrix
– Cisco Small Form-Factor Pluggable Modules Compatibility Matrix
– Compatibility Matrix for 1000BASE-T Small Form-Factor Pluggable Modules
Obtaining Documentation and Submitting a Service Request
For information on obtaining documentation, submitting a service request, and gathering additional
information, see the monthly What’s New in Cisco Product Documentation, which also lists all new and
revised Cisco technical documentation, at:
http://www.cisco.com/en/US/docs/general/whatsnew/whatsnew.html
Subscribe to the What’s New in Cisco Product Documentation as a Really Simple Syndication (RSS) feed
and set content to be delivered directly to your desktop using a reader application. The RSS feeds are a free
service and Cisco currently supports RSS Version 2.0.
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1
Overview
This chapter provides these topics about the switch software:
•
Features, page 1-1
•
Default Settings After Initial Switch Configuration, page 1-12
•
Design Concepts for Using the Switch, page 1-15
•
Where to Go Next, page 1-17
In this document, IP refers to IP Version 4 (IPv4) unless there is a specific reference to IP Version 6
(IPv6).
Features
The switch ships with the IP base image installed, which provides Layer 2+ features (enterprise-class
intelligent services). These features include access control lists (ACLs), quality of service (QoS), static
routing, EIGRP and PIM stub routing, the Hot Standby Router Protocol (HSRP), the Routing
Information Protocol (RIP), IPv6 host management, and IPv6 MLD snooping.
Some features described in this chapter are available only on the cryptographic (supports encryption)
version of the software. You must obtain authorization to use this feature and to download the
cryptographic version of the software from Cisco.com. For more information, see the release notes for
this release.
The switch has these features:
•
Ease-of-Deployment and Ease-of-Use Features, page 1-2
•
Performance Features, page 1-2
•
Management Options, page 1-3
•
Manageability Features, page 1-4 (includes a feature requiring the cryptographic version of the
software)
•
Availability and Redundancy Features, page 1-5
•
VLAN Features, page 1-6
•
Security Features, page 1-7 (includes a feature requiring the cryptographic version of the software)
•
QoS and CoS Features, page 1-10
•
Layer 3 Features, page 1-11
•
Monitoring Features, page 1-12
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Features
Ease-of-Deployment and Ease-of-Use Features
The switch ships with an embedded device manager GUI for configuring and monitoring a single switch
through a web browser. For more information about launching the device manager, see the getting started
guide. For more information about the device manager, see the switch online help.
•
User-defined and Cisco-default Smartports macros for creating custom switch configurations for
simplified deployment across the network.
•
AutoSmartport enhancements, which add support for global macros, last-resort macros, event
trigger control, access points, EtherChannels, auto-QoS with Cisco Medianet, and IP phones.
•
Call Home to provide e-mail-based and web-based notification of critical system events. Users with
a service contract directly with Cisco Systems can register Call Home devices for the Cisco Smart
Call Home service that generates automatic service requests with the Cisco TAC.
Performance Features
The switch ships with these performance features:
•
Autosensing of port speed and autonegotiation of duplex mode on all switch ports for optimizing
bandwidth
•
Automatic-medium-dependent interface crossover (auto-MDIX) capability on 10/100/1000 Mb/s
interfaces and on 10/100/1000 BASE-TX SFP module interfaces that enables the interface to
automatically detect the required cable connection type (straight-through or crossover) and to
configure the connection appropriately
•
Support for up to 1546 bytes routed frames
•
IEEE 802.3x flow control on all ports (the switch does not send pause frames)
•
EtherChannel for enhanced fault tolerance and for providing up to 8 Gb/s (Gigabit EtherChannel)
full-duplex bandwidth among switches, routers, and servers
•
Port Aggregation Protocol (PAgP) and Link Aggregation Control Protocol (LACP) for automatic
creation of EtherChannel links
•
Forwarding of Layer 2 and Layer 3 packets at Gigabit line rate
•
Per-port storm control for preventing broadcast, multicast, and unicast storms
•
Port blocking on forwarding unknown Layer 2 unknown unicast, multicast, and bridged broadcast
traffic
•
Protocol storm protection to control the rate of incoming protocol traffic to a switch by dropping
packets that exceed a specified ingress rate
•
Cisco Group Management Protocol (CGMP) server support and Internet Group Management
Protocol (IGMP) snooping for IGMP Versions 1, 2, and 3:
– (For CGMP devices) CGMP for limiting multicast traffic to specified end stations and reducing
overall network traffic
– (For IGMP devices) IGMP snooping for efficiently forwarding multimedia and multicast traffic
•
Internet Group Management Protocol (IGMP) snooping for IGMP Versions 1, 2, and 3 for
efficiently forwarding multimedia and multicast traffic
•
IGMP report suppression for sending only one IGMP report per multicast router query to the
multicast devices (supported only for IGMPv1 or IGMPv2 queries)
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Features
•
IGMP snooping querier support to configure switch to generate periodic IGMP General Query
messages
•
IGMP helper to allow the switch to forward a host request to join a multicast stream to a specific IP
destination address
•
Multicast Listener Discovery (MLD) snooping to enable efficient distribution of IP Version 6 (IPv6)
multicast data to clients and routers in a switched network.
•
Multicast VLAN registration (MVR) to continuously send multicast streams in a multicast VLAN
while isolating the streams from subscriber VLANs for bandwidth and security reasons
•
IGMP filtering for controlling the set of multicast groups to which hosts on a switch port can belong
•
IGMP throttling for configuring the action when the maximum number of entries is in the IGMP
forwarding table
•
IGMP leave timer for configuring the leave latency for the network
•
Switch Database Management (SDM) templates for allocating system resources to maximize
support for user-selected features
•
Cisco IOS IP Service Level Agreements (SLAs), a part of Cisco IOS software that uses active traffic
monitoring for measuring network performance
•
Configurable small-frame arrival threshold to prevent storm control when small frames (64 bytes or
less) arrive on an interface at a specified rate (the threshold)
•
RADIUS server load balancing to allow access and authentication requests to be distributed evenly
across a server group
•
Cisco Medianet to enable intelligent services in the network infrastructure for a wide variety of
video applications. One of the services of Medianet is auto provisioning for Cisco Digital Media
Players and Cisco IP Video Surveillance cameras through Auto Smartports.
•
Multicast VLAN registration (MVR) enhancements include the ability to configure 2000 MVR
groups when the switch is in dynamic MVR mode and a new command (mvr ringmode flood) to
ensure that forwarding in a ring topology is limited to member ports.
•
Memory consistency check routines to detect and correct invalid ternary content addressable
memory (TCAM) table entries.
Management Options
These are the options for configuring and managing the switch:
•
An embedded device manager—The device manager is a GUI that is integrated in the software
image. You use it to configure and to monitor a single switch. For information about launching the
device manager, see the getting started guide. For more information about the device manager, see the
switch online help.
•
CLI—The Cisco IOS software supports desktop- and multilayer-switching features. You can access
the CLI either by connecting your management station directly to the switch console port or by using
Telnet from a remote management station. For more information about the CLI, see Chapter 2,
“Using the Command-Line Interface.”
•
SNMP—SNMP management applications such asHP OpenView. You can manage from an
SNMP-compatible management station that is running platforms such as HP OpenView or SunNet
Manager. The switch supports a comprehensive set of MIB extensions and four remote monitoring
(RMON) groups. For more information about using SNMP, see Chapter 31, “Configuring SNMP.”
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Features
•
Note
Cisco IOS Configuration Engine (previously known to as the Cisco IOS CNS
agent)-—Configuration service automates the deployment and management of network devices and
services. You can automate initial configurations and configuration updates by generating
switch-specific configuration changes, sending them to the switch, executing the configuration
change, and logging the results. For more information, see Chapter 4, “Configuring Cisco IOS
Configuration Engine.”
For additional descriptions of the management interfaces, see the “Design Concepts for Using the
Switch” section on page 1-15.
Manageability Features
These are the manageability features:
•
CNS embedded agents for automating switch management, configuration storage, and delivery
•
DHCP for automating configuration of switch information (such as IP address, default gateway,
hostname, and Domain Name System [DNS] and TFTP server names)
•
DHCP relay for forwarding User Datagram Protocol (UDP) broadcasts, including IP address
requests, from DHCP clients
•
DHCP server for automatic assignment of IP addresses and other DHCP options to IP hosts
•
DHCP-based autoconfiguration and image update to download a specified configuration a new
image to a large number of switches
•
DHCP server port-based address allocation for the preassignment of an IP address to a switch port
•
Directed unicast requests to a DNS server for identifying a switch through its IP address and its
corresponding hostname and to a TFTP server for administering software upgrades from a TFTP
server
•
Address Resolution Protocol (ARP) for identifying a switch through its IP address and its
corresponding MAC address
•
Unicast MAC address filtering to drop packets with specific source or destination MAC addresses
•
Disabling MAC address learning on a VLAN
•
Configurable MAC address scaling that allows disabling MAC address learning on a VLAN to limit
the size of the MAC address table
•
Cisco Discovery Protocol (CDP) Versions 1 and 2 for network topology discovery and mapping
between the switch and other Cisco devices on the network
•
Link Layer Discovery Protocol (LLDP) and LLDP Media Endpoint Discovery (LLDP-MED) for
interoperability with third-party IP phones
•
LLDP media extensions (LLDP-MED) location TLV that provides location information from the
switch to the endpoint device
•
LLDP-MED network-policy profile time, length, value (TLV) for creating a profile for voice and
voice-signalling by specifying the values for VLAN, class of service (CoS), differentiated services
code point (DSCP), and tagging mode
•
CDP and LLDP enhancements for exchanging location information with video end points for
dynamic location-based content distribution from servers
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Features
•
Wired location service sends location and attachment tracking information for connected devices to
a Cisco Mobility Services Engine (MSE)
•
Network Time Protocol (NTP) for providing a consistent time stamp to all switches from an external
source
•
Network Time Protocol version 4 (NTPv4) to support both IPv4 and IPv6 and compatibility with
NTPv3
•
Cisco IOS File System (IFS) for providing a single interface to all file systems that the switch uses
•
Configuration logging to log and to view changes to the switch configuration
•
Unique device identifier to provide product identification information through a show inventory
user EXEC command display
•
In-band management access through the device manager over a Netscape Navigator or Microsoft
Internet Explorer browser session
•
In-band management access for up to 16 simultaneous Telnet connections for multiple CLI-based
sessions over the network
•
In-band management access for up to five simultaneous, encrypted Secure Shell (SSH) connections
for multiple CLI-based sessions over the network (requires the cryptographic version of the
software)
•
In-band management access through SNMP Versions 1, 2c, and 3 get and set requests
•
Out-of-band management access through the switch console port to a directly attached terminal or
to a remote terminal through a serial connection or a modem
•
CPU utilization threshold trap monitors CPU utilization
•
Secure Copy Protocol (SCP) feature to provide a secure and authenticated method for copying
switch configuration or switch image files (requires the cryptographic version of the software)
•
The HTTP client in Cisco IOS supports can send requests to both IPv4 and IPv6 HTTP servers, and
the HTTP server in Cisco IOS can service HTTP requests from both IPv4 and IPv6 HTTP clients.
•
Simple Network and Management Protocol (SNMP) can be configured over IPv6 transport so that
an IPv6 host can send SNMP queries and receive SNMP notifications from a device running IPv6.
•
IPv6 supports stateless autoconfiguration to manage link, subnet, and site addressing changes, such
as management of host and mobile IP addresses.
•
Support for including a hostname in the option 12 field of DHCPDISCOVER packets. This provides
identical configuration files to be sent by using the DHCP protocol.DHCP Snooping enhancement
to support the selection of a fixed string-based format for the circuit-id sub-option of the Option 82
DHCP field.
Availability and Redundancy Features
These are the availability and redundancy features:
•
HSRP for command switch and Layer 3 router redundancy
•
UniDirectional Link Detection (UDLD) and aggressive UDLD for detecting and disabling
unidirectional links on fiber-optic interfaces caused by incorrect fiber-optic wiring or port faults
•
IEEE 802.1D Spanning Tree Protocol (STP) for redundant backbone connections and loop-free
networks. STP has these features:
– Up to 128 spanning-tree instances supported
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Features
– Per-VLAN spanning-tree plus (PVST+) for load balancing across VLANs
– Rapid PVST+ for load balancing across VLANs and providing rapid convergence of
spanning-tree instances
– UplinkFast and BackboneFast for fast convergence after a spanning-tree topology change and
for achieving load balancing between redundant uplinks, including Gigabit uplinks
•
IEEE 802.1s Multiple Spanning Tree Protocol (MSTP) for grouping VLANs into a spanning-tree
instance and for providing multiple forwarding paths for data traffic and load balancing and rapid
per-VLAN Spanning-Tree plus (rapid-PVST+) based on the IEEE 802.1w Rapid Spanning Tree
Protocol (RSTP) for rapid convergence of the spanning tree by immediately changing root and
designated ports to the forwarding state
•
Optional spanning-tree features available in PVST+, rapid-PVST+, and MSTP mode:
– Port Fast for eliminating the forwarding delay by enabling a port to immediately change from
the blocking state to the forwarding state
– BPDU guard for shutting down Port Fast-enabled ports that receive bridge protocol data units
(BPDUs)
– BPDU filtering for preventing a Port Fast-enabled port from sending or receiving BPDUs
– Root guard for preventing switches outside the network core from becoming the spanning-tree
root
– Loop guard for preventing alternate or root ports from becoming designated ports because of a
failure that leads to a unidirectional link
•
Equal-cost routing for link-level and switch-level redundancy
•
Flex Link Layer 2 interfaces to back up one another as an alternative to STP for basic link
redundancy
•
Link state tracking (Layer 2 trunk failover) to mirror the state of the external Ethernet links and to
allow the failover of the processor blade traffic to an operational external link on a separate Cisco
Ethernet switch
VLAN Features
These are the VLAN features:
•
Support for up to 1005 VLANs for assigning users to VLANs associated with appropriate network
resources, traffic patterns, and bandwidth
•
Support for VLAN IDs in the 1 to 4094 range as allowed by the IEEE 802.1Q standard
•
VLAN Query Protocol (VQP) for dynamic VLAN membership
•
Inter-Switch Link (ISL) and IEEE 802.1Q trunking encapsulation on all ports for network moves,
adds, and changes; management and control of broadcast and multicast traffic; and network security
by establishing VLAN groups for high-security users and network resources
•
Dynamic Trunking Protocol (DTP) for negotiating trunking on a link between two devices and for
negotiating the type of trunking encapsulation (IEEE 802.1Q or ISL) to be used
•
VLAN Trunking Protocol (VTP) and VTP pruning for reducing network traffic by restricting
flooded traffic to links destined for stations receiving the traffic
•
Voice VLAN for creating subnets for voice traffic from Cisco IP Phones
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Features
•
VLAN 1 minimization for reducing the risk of spanning-tree loops or storms by allowing VLAN 1
to be disabled on any individual VLAN trunk link. With this feature enabled, no user traffic is sent
or received on the trunk. The switch CPU continues to send and receive control protocol frames.
•
VLAN Flex Link Load Balancing to provide Layer 2 redundancy without requiring Spanning Tree
Protocol (STP). A pair of interfaces configured as primary and backup links can load balance traffic
based on VLAN.
•
Private VLANs to address VLAN scalability problems, to provide a more controlled IP address
allocation, and to allow Layer 2 ports to be isolated from other ports on the switch
•
Port security on a PVLAN host to limit the number of MAC addresses learned on a port, or define
which MAC addresses may be learned on a port
•
Support for VTP version 3 that includes support for configuring extended range VLANs (VLANs
1006 to 4094) in any VTP mode, enhanced authentication (hidden or secret passwords), propagation
of other databases in addition to VTP, VTP primary and secondary servers, and the option to turn
VTP on or off by port.
Security Features
The switch ships with these security features:
•
IP Service Level Agreements (IP SLAs) support to measure network performance by using active
traffic monitoring
•
Web authentication to allow a supplicant (client) that does not support IEEE 802.1x functionality to
be authenticated using a web browser
•
MAC authentication bypass (MAB) aging timer to detect inactive hosts that have authenticated after
they have authenticated by using MAB
•
Local web authentication banner so that custom banner or image file can be displayed at a web
authentication login screen
•
Password-protected access (read-only and read-write access) to management interfaces (device
manager and the CLI for protection against unauthorized configuration changes
•
Multilevel security for a choice of security level, notification, and resulting actions
•
Static MAC addressing for ensuring security
•
Protected port option for restricting the forwarding of traffic to designated ports on the same switch
•
Port security option for limiting and identifying MAC addresses of the stations allowed to access
the port
•
VLAN aware port security option shut down the VLAN on the port when a violation occurs, instead
of shutting down the entire port.
•
Voice aware IEEE 802.1x and mac authentication bypass (MAB) security violation to shut down
only the data VLAN on a port when a security violation occurs
•
Port security aging to set the aging time for secure addresses on a port
•
BPDU guard for shutting down a Port Fast-configured port when an invalid configuration occurs
•
Standard and extended IP access control lists (ACLs) for defining security policies in both directions
on routed interfaces (router ACLs) and VLANs and inbound on Layer 2 interfaces (port ACLs)
•
Extended MAC access control lists for defining security policies in the inbound direction on Layer 2
interfaces
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Overview
Features
•
VLAN ACLs (VLAN maps) for providing intra-VLAN security by filtering traffic based on
information in the MAC, IP, and TCP/UDP headers
•
Source and destination MAC-based ACLs for filtering non-IP traffic
•
Support for dynamic creation or attachment of an auth-default ACL on a port that has no configured
static ACLs
•
DHCP snooping to filter untrusted DHCP messages between untrusted hosts and DHCP servers
•
IP source guard to restrict traffic on nonrouted interfaces by filtering traffic based on the DHCP
snooping database and IP source bindings
•
Dynamic ARP inspection to prevent malicious attacks on the switch by not relaying invalid ARP
requests and responses to other ports in the same VLAN
•
IEEE 802.1Q tunneling so that customers with users at remote sites across a service-provider
network can keep VLANs segregated from other customers and Layer 2 protocol tunneling to ensure
that the customer’s network has complete STP, CDP, and VTP information about all users
•
Layer 2 point-to-point tunneling to facilitate the automatic creation of EtherChannels
•
Layer 2 protocol tunneling bypass feature to provide interoperability with third-party vendors
•
IEEE 802.1x with open access to allow a host to access the network before being authenticated
•
Flexible-authentication sequencing to configure the order of the authentication methods that a port
tries when authenticating a new host
•
IEEE 802.1x port-based authentication to prevent unauthorized devices (clients) from gaining
access to the network. These features are supported:
– VLAN assignment for restricting IEEE 802.1x-authenticated users to a specified VLAN
– Port security for controlling access to IEEE 802.1x ports
– Voice VLAN to permit a Cisco IP Phone to access the voice VLAN regardless of the authorized
or unauthorized state of the port
– Guest VLAN to provide limited services to non-IEEE 802.1x-compliant users
– Restricted VLAN to provide limited services to users who are IEEE 802.1x compliant, but do
not have the credentials to authenticate via the standard IEEE 802.1x processes
– Support for VLAN assignment on a port configured for multi-auth mode. The RADIUS server
assigns a VLAN to the first host to authenticate on the port, and subsequent hosts use the same
VLAN. Voice VLAN assignment is supported for one IP phone.
– IEEE 802.1x accounting to track network usage
– IEEE 802.1x with wake-on-LAN to allow dormant PCs to be powered on based on the receipt
of a specific Ethernet frame
– IEEE 802.1x readiness check to determine the readiness of connected end hosts before
configuring IEEE 802.1x on the switch
– Voice aware IEEE 802.1x security to apply traffic violation actions only on the VLAN on which
a security violation occurs
– Voice aware IEEE 802.1x security to apply traffic violation actions only on the VLAN on which
a security violation occurs
– Network Edge Access Topology (NEAT) with 802.1X switch supplicant, host authorization
with CISP, and auto enablement to authenticate a switch outside a wiring closet as a supplicant
to another switch
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Overview
Features
– IEEE 802.1x authentication with downloadable ACLs and redirect URLs to allow per-user ACL
downloads from a Cisco Secure ACS server to an authenticated switch
– Multiple-user authentication to allow more than one host to authenticate on an 802.1x-enabled
port
•
MAC authentication bypass to authorize clients based on the client MAC address
•
Network Admission Control (NAC) features:
– NAC Layer 2 IEEE 802.1x validation of the antivirus condition or posture of endpoint systems
or clients before granting the devices network access.
For information about configuring NAC Layer 2 IEEE 802.1x validation, see the “Configuring
NAC Layer 2 802.1x Validation” section on page 8-58.
– NAC Layer 2 IP validation of the posture of endpoint systems or clients before granting the
devices network access.
For information about configuring NAC Layer 2 IP validation, see the Network Admission
Control Software Configuration Guide.
– IEEE 802.1x inaccessible authentication bypass.
For information about configuring this feature, see the “Configuring the Inaccessible
Authentication Bypass Feature” section on page 8-53.
– Authentication, authorization, and accounting (AAA) down policy for a NAC Layer 2 IP
validation of a host if the AAA server is not available when the posture validation occurs.
For information about this feature, see the Network Admission Control Software Configuration
Guide.
•
TACACS+, a proprietary feature for managing network security through a TACACS server
•
RADIUS for verifying the identity of, granting access to, and tracking the actions of remote users
through authentication, authorization, and accounting (AAA) services
•
Enhancements to RADIUS, TACACS+, and SSH to function over IPv6.
•
Kerberos security system to authenticate requests for network resources by using a trusted third
party (requires the cryptographic version of the software)
•
Secure Socket Layer (SSL) Version 3.0 support for the HTTP 1.1 server authentication, encryption,
and message integrity and HTTP client authentication to allow secure HTTP communications
(requires the cryptographic version of the software)
•
Support for IP source guard on static hosts.
•
RADIUS Change of Authorization (CoA) to change the attributes of a certain session after it is
authenticated. When there is a change in policy for a user or user group in AAA, administrators can
send the RADIUS CoA packets from the AAA server, such as Cisco Secure ACS to reinitialize
authentication, and apply to the new policies.
•
IEEE 802.1x User Distribution to allow deployments with multiple VLANs (for a group of users) to
improve scalability of the network by load balancing users across different VLANs. Authorized
users are assigned to the least populated VLAN in the group, assigned by RADIUS server.
•
Support for critical VLAN with multiple-host authentication so that when a port is configured for
multi-auth, and an AAA server becomes unreachable, the port is placed in a critical VLAN in order
to still permit access to critical resources.
•
Customizable web authentication enhancement to allow the creation of user-defined login, success,
failure and expire web pages for local web authentication.
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Features
•
Support for Network Edge Access Topology (NEAT) to change the port host mode and to apply a
standard port configuration on the authenticator switch port.
•
VLAN-ID based MAC authentication to use the combined VLAN and MAC address information for
user authentication to prevent network access from unauthorized VLANs.
•
MAC move to allow hosts (including the hosts connected behind an IP phone) to move across ports
within the same switch without any restrictions to enable mobility. With MAC move, the switch
treats the reappearance of the same MAC address on another port in the same way as a completely
new MAC address.
•
Support for 3DES and AES with version 3 of the Simple Network Management Protocol (SNMPv3).
This release adds support for the 168-bit Triple Data Encryption Standard (3DES) and the 128-bit,
192-bit, and 256-bit Advanced Encryption Standard (AES) encryption algorithms to SNMPv3.
•
Support for the Security Group Tag (SCT) Exchange Protocol (SXP) component of Cisco TrustSec,
a security architecture using authentication, encryption, and access control.
QoS and CoS Features
These are the QoS and CoS features:
•
Automatic QoS (auto-QoS) to simplify the deployment of existing QoS features by classifying
traffic and configuring egress queues
•
Classification
– IP type-of-service/Differentiated Services Code Point (IP ToS/DSCP) and IEEE 802.1p CoS
marking priorities on a per-port basis for protecting the performance of mission-critical
applications
– IP ToS/DSCP and IEEE 802.1p CoS marking based on flow-based packet classification
(classification based on information in the MAC, IP, and TCP/UDP headers) for
high-performance quality of service at the network edge, allowing for differentiated service
levels for different types of network traffic and for prioritizing mission-critical traffic in the
network
– Trusted port states (CoS, DSCP, and IP precedence) within a QoS domain and with a port
bordering another QoS domain
– Trusted boundary for detecting the presence of a Cisco IP Phone, trusting the CoS value
received, and ensuring port security
•
Policing
– Traffic-policing policies on the switch port for managing how much of the port bandwidth
should be allocated to a specific traffic flow
– If you configure multiple class maps for a hierarchical policy map, each class map can be
associated with its own port-level (second-level) policy map. Each second-level policy map can
have a different policer.
– Aggregate policing for policing traffic flows in aggregate to restrict specific applications or
traffic flows to metered, predefined rates
•
Out-of-Profile
– Out-of-profile markdown for packets that exceed bandwidth utilization limits
•
Ingress queueing and scheduling
– Two configurable ingress queues for user traffic (one queue can be the priority queue)
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Features
– Weighted tail drop (WTD) as the congestion-avoidance mechanism for managing the queue
lengths and providing drop precedences for different traffic classifications
– Shaped round robin (SRR) as the scheduling service for specifying the rate at which packets are
sent to the internal ring (sharing is the only supported mode on ingress queues)
•
Egress queues and scheduling
– Four egress queues per port
– WTD as the congestion-avoidance mechanism for managing the queue lengths and providing
drop precedences for different traffic classifications
– SRR as the scheduling service for specifying the rate at which packets are dequeued to the
egress interface (shaping or sharing is supported on egress queues). Shaped egress queues are
guaranteed but limited to using a share of port bandwidth. Shared egress queues are also
guaranteed a configured share of bandwidth, but can use more than the guarantee if other queues
become empty and do not use their share of the bandwidth.
•
Support for IPv6 QoS trust capability.
•
Auto-QoS enhancements that add automatic configuration classification of traffic flow from video
devices, such as the Cisco Telepresence System and Cisco Surveillance Camera.
Layer 3 Features
•
HSRP Version 1 (HSRPv1) and HSRP Version 2 (HSRPv2) for Layer 3 router redundancy
•
IP routing protocols for load balancing and for constructing scalable, routed backbones, including
RIP Versions 1 and 2
•
OSPF for routed access to enable customers to extend Layer 3 routing capabilities to the access or
wiring closet.
•
IP routing between VLANs (inter-VLAN routing) for full Layer 3 routing between two or more
VLANs, allowing each VLAN to maintain its own autonomous data-link domain
•
Static IP routing for manually building a routing table of network path information
•
Equal-cost routing for load balancing and redundancy
•
Internet Control Message Protocol (ICMP) and ICMP Router Discovery Protocol (IRDP) for using
router advertisement and router solicitation messages to discover the addresses of routers on directly
attached subnets
•
DHCP relay for forwarding UDP broadcasts, including IP address requests, from DHCP clients
•
DHCPv6 bulk-lease query to support new bulk lease query type (as defined in RFC5460).
•
The DHCPv6 relay source configuration feature to configure a source address for DHCPv6 relay
agent.
•
IPv6 default router preference (DRP) for improving the ability of a host to select an appropriate
router
•
IPv6 unicast host management
•
The ability to exclude a port in a VLAN from the SVI line-state up or down calculation
•
Support for the Virtual Router Redundancy Protocol (VRRP for IPv4), which dynamically assigns
responsibility for one or more virtual routers to the VRRP routers on a LAN, allowing multiple
routers on a multiaccess link to utilize the same virtual IP address.
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Default Settings After Initial Switch Configuration
Monitoring Features
These are the monitoring features:
•
Switch LEDs that provide port- and switch-level status
•
MAC address notification traps and RADIUS accounting for tracking users on a network by storing
the MAC addresses that the switch has learned or removed
•
Switched Port Analyzer (SPAN) and Remote SPAN (RSPAN) for traffic monitoring on any port or
VLAN
•
SPAN and RSPAN support of Intrusion Detection Systems (IDS) to monitor, repel, and report
network security violations
•
Four groups (history, statistics, alarms, and events) of embedded RMON agents for network
monitoring and traffic analysis
•
Syslog facility for logging system messages about authentication or authorization errors, resource
issues, and time-out events
•
Layer 2 traceroute to identify the physical path that a packet takes from a source device to a
destination device
•
SFP module diagnostic management interface to monitor physical or operational status of an SFP
module
•
Generic online diagnostics to test hardware functionality of the supervisor engine, modules, and
switch while the switch is connected to a live network.
•
Enhanced object tracking for HSRP.
•
Support for Embedded Event Manager (EEM) for event detection and recovery within a Cisco IOS
device, and EEM 3.2, which introduces event detectors for Neighbor Discovery, Identity, and
MAC-Address-Table.
•
IETF IP-MIB and IP-FORWARD-MIB(RFC4292 and RFC4293) updates to support the IP version 6
(IPv6)-only and the IPv6 part of the protocol-version independent (PVI) objects and tables.
Default Settings After Initial Switch Configuration
The switch is designed for plug-and-play operation, requiring only that you assign basic IP information
to the switch and connect it to the other devices in your network. If you have specific network needs,
you can change the interface-specific and system-wide settings.
Note
For information about assigning an IP address by using the CLI-based setup program, see the hardware
installation guide.
If you do not configure the switch at all, the switch operates with these default settings:
•
Default switch IP address, subnet mask, and default gateway is 0.0.0.0. For more information, see
Chapter 3, “Assigning the Switch IP Address and Default Gateway,” and Chapter 21, “Configuring
DHCP Features and IP Source Guard.”
•
Default domain name is not configured. For more information, see Chapter 3, “Assigning the Switch
IP Address and Default Gateway.”
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Default Settings After Initial Switch Configuration
•
DHCP client is enabled, the DHCP server is enabled (only if the device acting as a DHCP server is
configured and is enabled), and the DHCP relay agent is enabled (only if the device is acting as a
DHCP relay agent is configured and is enabled). For more information, see Chapter 3, “Assigning
the Switch IP Address and Default Gateway,” and Chapter 21, “Configuring DHCP Features and IP
Source Guard.”
•
No passwords are defined. For more information, see Chapter 5, “Administering the Switch.”
•
System name and prompt is Switch. For more information, see Chapter 5, “Administering the
Switch.”
•
NTP is enabled. For more information, see Chapter 5, “Administering the Switch.”
•
DNS is enabled. For more information, see Chapter 5, “Administering the Switch.”
•
TACACS+ is disabled. For more information, see Chapter 7, “Configuring Switch-Based
Authentication.”
•
RADIUS is disabled. For more information, see Chapter 7, “Configuring Switch-Based
Authentication.”
•
The standard HTTP server and Secure Socket Layer (SSL) HTTPS server are both enabled. For more
information, see Chapter 7, “Configuring Switch-Based Authentication.”
•
IEEE 802.1x is disabled. For more information, see Chapter 8, “Configuring IEEE 802.1x
Port-Based Authentication.”
•
Port parameters
– Operating mode is Layer 2 (switchport). For more information, see Chapter 10, “Configuring
Interface Characteristics.”
– Interface speed and duplex mode is autonegotiate. For more information, see Chapter 10,
“Configuring Interface Characteristics.”
– Auto-MDIX is enabled. For more information, see Chapter 10, “Configuring Interface
Characteristics.”
– Flow control is off. For more information, see Chapter 10, “Configuring Interface
Characteristics.”
– PortFast is enabled on the ten internal Gigabit Ethernet ports. For more information, see
Chapter 19, “Configuring Optional Spanning-Tree Features.”
•
No Smartports macros are defined. For more information, see Chapter 11, “Configuring Smartports
Macros.”
•
VLANs
– Default VLAN is VLAN 1. For more information, see Chapter 12, “Configuring VLANs.”
– VLAN trunking setting is dynamic auto (DTP). For more information, see Chapter 12,
“Configuring VLANs.”
– Trunk encapsulation is negotiate. For more information, see Chapter 12, “Configuring VLANs.”
– VTP mode is server. For more information, see Chapter 13, “Configuring VTP.”
– VTP version is Version 1. For more information, see Chapter 13, “Configuring VTP.”
– No private VLANs are configured. For more information, see Chapter 15, “Configuring Private
VLANs.”
– Voice VLAN is disabled. For more information, see Chapter 14, “Configuring Voice VLAN.”
•
IEEE 802.1Q tunneling and Layer 2 protocol tunneling are disabled. For more information, see
Chapter 16, “Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling.”
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Default Settings After Initial Switch Configuration
•
STP, PVST+ is enabled on VLAN 1. For more information, see Chapter 17, “Configuring STP.”
•
MSTP is disabled. For more information, see Chapter 18, “Configuring MSTP.”
•
Optional spanning-tree features are disabled. For more information, see Chapter 19, “Configuring
Optional Spanning-Tree Features.”
•
Flex Links are not configured. For more information, see Chapter 20, “Configuring Flex Links and
the MAC Address-Table Move Update Feature.”
•
DHCP snooping is disabled. The DHCP snooping information option is enabled. For more
information, see Chapter 21, “Configuring DHCP Features and IP Source Guard.”
•
IP source guard is disabled. For more information, see Chapter 21, “Configuring DHCP Features
and IP Source Guard.”
•
Dynamic ARP inspection is disabled on all VLANs. For more information, see Chapter 22,
“Configuring Dynamic ARP Inspection.”
•
IGMP snooping is enabled. No IGMP filters are applied. For more information, see Chapter 23,
“Configuring IGMP Snooping and MVR.”
•
IGMP throttling setting is deny. For more information, see Chapter 23, “Configuring IGMP
Snooping and MVR.”
•
The IGMP snooping querier feature is disabled. For more information, see Chapter 23, “Configuring
IGMP Snooping and MVR.”
•
MVR is disabled. For more information, see Chapter 23, “Configuring IGMP Snooping and MVR.”
•
Port-based traffic
– Broadcast, multicast, and unicast storm control is disabled. For more information, see
Chapter 24, “Configuring Port-Based Traffic Control.”
– No protected ports are defined. For more information, see Chapter 24, “Configuring Port-Based
Traffic Control.”
– Unicast and multicast traffic flooding is not blocked. For more information, see Chapter 24,
“Configuring Port-Based Traffic Control.”
– No secure ports are configured. For more information, see Chapter 24, “Configuring Port-Based
Traffic Control.”
•
CDP is enabled. For more information, see Chapter 25, “Configuring CDP.”
•
UDLD is disabled. For more information, see Chapter 27, “Configuring UDLD.”
•
SPAN and RSPAN are disabled. For more information, see Chapter 28, “Configuring SPAN and
RSPAN.”
•
RMON is disabled. For more information, see Chapter 29, “Configuring RMON.”
•
Syslog messages are enabled and appear on the console. For more information, see Chapter 30,
“Configuring System Message Logging.”
•
SNMP is enabled (Version 1). For more information, see Chapter 31, “Configuring SNMP.”
•
No ACLs are configured. For more information, see Chapter 33, “Configuring Network Security
with ACLs.”
•
QoS is disabled. For more information, see Chapter 34, “Configuring QoS.”
•
No EtherChannels are configured. For more information, see Chapter 35, “Configuring
EtherChannels and Layer 2 Trunk Failover.”
•
IP unicast routing is disabled. For more information, see Chapter 36, “Configuring IP Unicast
Routing.”
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Design Concepts for Using the Switch
•
No HSRP groups are configured. For more information, see Chapter 40, “Configuring HSRP, VRRP,
and Enhanced Object Tracking.”
Design Concepts for Using the Switch
As your network users compete for network bandwidth, it takes longer to send and receive data. When
you configure your network, consider the bandwidth required by your network users and the relative
priority of the network applications that they use.
Table 1-1 describes what can cause network performance to degrade and how you can configure your
network to increase the bandwidth available to your network users.
Table 1-1
Increasing Network Performance
Network Demands
Suggested Design Methods
Too many users on a single network
segment and a growing number of
users accessing the Internet
•
Increased power of new PCs,
workstations, and servers
•
High bandwidth demand from
networked applications (such as
e-mail with large attached files)
and from bandwidth-intensive
applications (such as
multimedia)
•
Create smaller network segments so that fewer users share the bandwidth, and use
VLANs and IP subnets to place the network resources in the same logical network
as the users who access those resources most.
•
Use full-duplex operation between the switch and its connected workstations.
•
Connect global resources—such as servers and routers to which the network users
require equal access—directly to the high-speed switch ports so that they have
their own high-speed segment.
•
Use the EtherChannel feature between the switch and its connected servers and
routers.
Bandwidth alone is not the only consideration when designing your network. As your network traffic
profiles evolve, consider providing network services that can support applications for voice and data
integration, multimedia integration, application prioritization, and security. Table 1-2 describes some
network demands and how you can meet them.
Table 1-2
Providing Network Services
Network Demands
Efficient bandwidth usage for
multimedia applications and
guaranteed bandwidth for critical
applications
Suggested Design Methods
•
Use IGMP snooping to efficiently forward multimedia and multicast traffic.
•
Use other QoS mechanisms such as packet classification, marking, scheduling,
and congestion avoidance to classify traffic with the appropriate priority level,
thereby providing maximum flexibility and support for mission-critical, unicast,
and multicast and multimedia applications.
•
Use MVR to continuously send multicast streams in a multicast VLAN but to
isolate the streams from subscriber VLANs for bandwidth and security reasons.
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Design Concepts for Using the Switch
Table 1-2
Providing Network Services (continued)
Network Demands
Suggested Design Methods
High demand on network redundancy
and availability to provide always on
mission-critical applications
•
Use Hot Standby Router Protocol (HSRP) for cluster command switch and router
redundancy.
•
Use VLAN trunks and BackboneFast for traffic-load balancing on the uplink ports
so that the uplink port with a lower relative port cost is selected to carry the VLAN
traffic.
An evolving demand for IP telephony
•
Use QoS to prioritize applications such as IP telephony during congestion and to
help control both delay and jitter within the network.
•
Use switches that support at least two queues per port to prioritize voice and data
traffic as either high- or low-priority, based on IEEE 802.1p/Q. The switch
supports at least four queues per port.
•
Use voice VLAN IDs (VVIDs) to provide separate VLANs for voice traffic.
You can use the switches to create the following:
•
Cost-effective Gigabit-to-the-blade server for high-performance workgroups (Figure 1-1)—For
high-speed access to network resources, you can use the Cisco Catalyst Blade Switch 3030 for Dell
in the access layer to provide Gigabit Ethernet to the blade servers. To prevent congestion, use QoS
DSCP marking priorities on these switches. For high-speed IP forwarding at the distribution layer,
connect the switches in the access layer to a Gigabit multilayer switch with routing capability, such
as a Catalyst 3750 switch, or to a router.
The first illustration is of an isolated high-performance workgroup, where the blade switches are
connected to Catalyst 3750 switches in the distribution layer.
Each blade switch in this configuration provides users with a dedicated 1-Gb/s connection to
network resources. Using SFP modules also provides flexibility in media and distance options
through fiber-optic connections.
Figure 1-1
High-Performance Workgroup (Gigabit-to-the-Blade Server)
Catalyst 3750
switches
119954
Blade Switches
Blade Server
Blade Server
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Where to Go Next
•
Server aggregation (Figure 1-2)—You can use the switches to interconnect groups of servers,
centralizing physical security and administration of your network. For high-speed IP forwarding at
the distribution layer, connect the switches in the access layer to multilayer switches with routing
capability. The Gigabit interconnections minimize latency in the data flow.
QoS and policing on the blade switches provide preferential treatment for certain data streams. They
segment traffic streams into different paths for processing. Security features on the blade switch
ensure rapid handling of packets.
Fault tolerance from the server racks to the core is achieved through dual homing of servers
connected to the blade switches, which have redundant Gigabit EtherChannels.
Using dual SFP module uplinks from the blade switches provides redundant uplinks to the network
core. Using SFP modules provides flexibility in media and distance options through fiber-optic
connections.
Figure 1-2
Server Aggregation
Campus
core
Catalyst 6500
switches
Catalyst 3750
StackWise
switch stacks
Blade
Servers
119956
Blade
Switches
Where to Go Next
Before configuring the switch, review these sections for startup information:
•
Chapter 2, “Using the Command-Line Interface”
•
Chapter 3, “Assigning the Switch IP Address and Default Gateway”
To locate and download MIBs for a specific Cisco product and release, use the Cisco MIB Locator:
http://cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml.
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Where to Go Next
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CH A P T E R
2
Using the Command-Line Interface
This chapter describes the Cisco IOS command-line interface (CLI) and how to use it to configure your
switch. It contains these sections:
•
Understanding Command Modes, page 2-1
•
Understanding the Help System, page 2-3
•
Understanding Abbreviated Commands, page 2-3
•
Understanding no and default Forms of Commands, page 2-4
•
Understanding CLI Error Messages, page 2-4
•
Using Configuration Logging, page 2-4
•
Using Command History, page 2-5
•
Using Editing Features, page 2-6
•
Searching and Filtering Output of show and more Commands, page 2-9
•
Accessing the CLI, page 2-9
Understanding Command Modes
The Cisco IOS user interface is divided into many different modes. The commands available to you
depend on which mode you are currently in. Enter a question mark (?) at the system prompt to obtain a
list of commands available for each command mode.
When you start a session on the switch, you begin in user mode, often called user EXEC mode. Only a
limited subset of the commands are available in user EXEC mode. For example, most of the user EXEC
commands are one-time commands, such as show commands, which show the current configuration
status, and clear commands, which clear counters or interfaces. The user EXEC commands are not saved
when the switch reboots.
To have access to all commands, you must enter privileged EXEC mode. Normally, you must enter a
password to enter privileged EXEC mode. From this mode, you can enter any privileged EXEC
command or enter global configuration mode.
Using the configuration modes (global, interface, and line), you can make changes to the running
configuration. If you save the configuration, these commands are stored and used when the switch
reboots. To access the various configuration modes, you must start at global configuration mode. From
global configuration mode, you can enter interface configuration mode and line configuration mode.
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Using the Command-Line Interface
Understanding Command Modes
Table 2-1 describes the main command modes, how to access each one, the prompt you see in that mode,
and how to exit the mode. The examples in the table use the hostname Switch.
Table 2-1
Command Mode Summary
Mode
Access Method
Prompt
User EXEC
Begin a session with Switch>
your switch.
Exit Method
About This Mode
Enter logout or
quit.
Use this mode to
•
Change terminal settings.
•
Perform basic tests.
•
Display system
information.
Privileged EXEC
While in user EXEC Switch#
mode, enter the
enable command.
Enter disable to
exit.
Global configuration
While in privileged
EXEC mode, enter
the configure
command.
Switch(config)#
To exit to privileged Use this mode to configure
EXEC mode, enter parameters that apply to the
exit or end, or press entire switch.
Ctrl-Z.
VLAN configuration
While in global
configuration mode,
enter the
vlan vlan-id
command.
Switch(config-vlan)#
To exit to global
configuration mode,
enter the exit
command.
While in global
configuration mode,
enter the interface
command (with a
specific interface).
Switch(config-if)#
Interface
configuration
To return to
privileged EXEC
mode, press Ctrl-Z
or enter end.
Use this mode to verify
commands that you have
entered. Use a password to
protect access to this mode.
Use this mode to configure
VLAN parameters. When VTP
mode is transparent, you can
create extended-range VLANs
(VLAN IDs greater than 1005)
and save configurations in the
switch startup configuration
file.
Use this mode to configure
To exit to global
configuration mode, parameters for the Ethernet
ports.
enter exit.
To return to
privileged EXEC
mode, press Ctrl-Z
or enter end.
For information about defining
interfaces, see the “Using
Interface Configuration Mode”
section on page 10-7.
To configure multiple
interfaces with the same
parameters, see the
“Configuring a Range of
Interfaces” section on
page 10-8.
Line configuration
While in global
configuration mode,
specify a line with
the line vty or line
console command.
Switch(config-line)#
Use this mode to configure
To exit to global
configuration mode, parameters for the terminal
line.
enter exit.
To return to
privileged EXEC
mode, press Ctrl-Z
or enter end.
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Understanding the Help System
For more detailed information on the command modes, see the command reference guide for this release.
Understanding the Help System
You can enter a question mark (?) at the system prompt to display a list of commands available for each
command mode. You can also obtain a list of associated keywords and arguments for any command, as
shown in Table 2-2.
Table 2-2
Help Summary
Command
Purpose
help
Obtain a brief description of the help system in any command mode.
abbreviated-command-entry?
Obtain a list of commands that begin with a particular character string.
For example:
Switch# di?
dir disable disconnect
abbreviated-command-entry<Tab>
Complete a partial command name.
For example:
Switch# sh conf<tab>
Switch# show configuration
?
List all commands available for a particular command mode.
For example:
Switch> ?
command ?
List the associated keywords for a command.
For example:
Switch> show ?
command keyword ?
List the associated arguments for a keyword.
For example:
Switch(config)# cdp holdtime ?
<10-255> Length of time (in sec) that receiver must keep this packet
Understanding Abbreviated Commands
You need to enter only enough characters for the switch to recognize the command as unique.
This example shows how to enter the show configuration privileged EXEC command in an abbreviated
form:
Switch# show conf
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Understanding no and default Forms of Commands
Understanding no and default Forms of Commands
Almost every configuration command also has a no form. In general, use the no form to disable a feature
or function or reverse the action of a command. For example, the no shutdown interface configuration
command reverses the shutdown of an interface. Use the command without the keyword no to re-enable
a disabled feature or to enable a feature that is disabled by default.
Configuration commands can also have a default form. The default form of a command returns the
command setting to its default. Most commands are disabled by default, so the default form is the same
as the no form. However, some commands are enabled by default and have variables set to certain default
values. In these cases, the default command enables the command and sets variables to their default
values.
Understanding CLI Error Messages
Table 2-3 lists some error messages that you might encounter while using the CLI to configure your
switch.
Table 2-3
Common CLI Error Messages
Error Message
Meaning
How to Get Help
% Ambiguous command:
"show con"
You did not enter enough characters
for your switch to recognize the
command.
Re-enter the command followed by a question mark (?)
with a space between the command and the question
mark.
The possible keywords that you can enter with the
command appear.
% Incomplete command.
You did not enter all the keywords or Re-enter the command followed by a question mark (?)
values required by this command.
with a space between the command and the question
mark.
The possible keywords that you can enter with the
command appear.
% Invalid input detected
at ‘^’ marker.
You entered the command
incorrectly. The caret (^) marks the
point of the error.
Enter a question mark (?) to display all the commands
that are available in this command mode.
The possible keywords that you can enter with the
command appear.
Using Configuration Logging
You can log and view changes to the switch configuration. You can use the Configuration Change
Logging and Notification feature to track changes on a per-session and per-user basis. The logger tracks
each configuration command that is applied, the user who entered the command, the time that the
command was entered, and the parser return code for the command. This feature includes a mechanism
for asynchronous notification to registered applications whenever the configuration changes. You can
choose to have the notifications sent to the syslog.
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Using the Command-Line Interface
Using Command History
For more information, see the Configuration Change Notification and Logging feature module at this
URL:
http://www.cisco.com/en/US/products/sw/iosswrel/ps5207/products_feature_guide09186a00801d1e81.
html
Note
Only CLI or HTTP changes are logged.
Using Command History
The software provides a history or record of commands that you have entered. The command history
feature is particularly useful for recalling long or complex commands or entries, including access lists.
You can customize this feature to suit your needs as described in these sections:
•
Changing the Command History Buffer Size, page 2-5 (optional)
•
Recalling Commands, page 2-5 (optional)
•
Disabling the Command History Feature, page 2-6 (optional)
Changing the Command History Buffer Size
By default, the switch records ten command lines in its history buffer. You can alter this number for a
current terminal session or for all sessions on a particular line. These procedures are optional.
Beginning in privileged EXEC mode, enter this command to change the number of command lines that
the switch records during the current terminal session:
Switch# terminal history
[size number-of-lines]
The range is from 0 to 256.
Beginning in line configuration mode, enter this command to configure the number of command lines
the switch records for all sessions on a particular line:
Switch(config-line)# history
[size number-of-lines]
The range is from 0 to 256.
Recalling Commands
To recall commands from the history buffer, perform one of the actions listed in Table 2-4. These actions
are optional.
Table 2-4
Recalling Commands
Action1
Result
Press Ctrl-P or the up arrow key.
Recall commands in the history buffer, beginning with the most recent command.
Repeat the key sequence to recall successively older commands.
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Using Editing Features
Table 2-4
Recalling Commands (continued)
Action1
Result
Press Ctrl-N or the down arrow key.
Return to more recent commands in the history buffer after recalling commands
with Ctrl-P or the up arrow key. Repeat the key sequence to recall successively
more recent commands.
show history
While in privileged EXEC mode, list the last several commands that you just
entered. The number of commands that appear is controlled by the setting of the
terminal history global configuration command and the history line configuration
command.
1. The arrow keys function only on ANSI-compatible terminals such as VT100s.
Disabling the Command History Feature
The command history feature is automatically enabled. You can disable it for the current terminal session
or for the command line. These procedures are optional.
To disable the feature during the current terminal session, enter the terminal no history privileged
EXEC command.
To disable command history for the line, enter the no history line configuration command.
Using Editing Features
This section describes the editing features that can help you manipulate the command line. It contains
these sections:
•
Enabling and Disabling Editing Features, page 2-6 (optional)
•
Editing Commands through Keystrokes, page 2-7 (optional)
•
Editing Command Lines that Wrap, page 2-8 (optional)
Enabling and Disabling Editing Features
Although enhanced editing mode is automatically enabled, you can disable it, re-enable it, or configure
a specific line to have enhanced editing. These procedures are optional.
To globally disable enhanced editing mode, enter this command in line configuration mode:
Switch (config-line)# no editing
To re-enable the enhanced editing mode for the current terminal session, enter this command in
privileged EXEC mode:
Switch# terminal editing
To reconfigure a specific line to have enhanced editing mode, enter this command in line configuration
mode:
Switch(config-line)# editing
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Using Editing Features
Editing Commands through Keystrokes
Table 2-5 shows the keystrokes that you need to edit command lines. These keystrokes are optional.
Table 2-5
Editing Commands through Keystrokes
Capability
Keystroke1
Move around the command line to
make changes or corrections.
Press Ctrl-B, or press the Move the cursor back one character.
left arrow key.
Purpose
Press Ctrl-F, or press the
right arrow key.
Move the cursor forward one character.
Press Ctrl-A.
Move the cursor to the beginning of the command line.
Press Ctrl-E.
Move the cursor to the end of the command line.
Press Esc B.
Move the cursor back one word.
Press Esc F.
Move the cursor forward one word.
Press Ctrl-T.
Transpose the character to the left of the cursor with the
character located at the cursor.
Recall commands from the buffer and Press Ctrl-Y.
paste them in the command line. The
switch provides a buffer with the last
ten items that you deleted.
Recall the most recent entry in the buffer.
Press Esc Y.
Recall the next buffer entry.
The buffer contains only the last 10 items that you have
deleted or cut. If you press Esc Y more than ten times, you
cycle to the first buffer entry.
Delete entries if you make a mistake Press the Delete or
or change your mind.
Backspace key.
Capitalize or lowercase words or
capitalize a set of letters.
Erase the character to the left of the cursor.
Press Ctrl-D.
Delete the character at the cursor.
Press Ctrl-K.
Delete all characters from the cursor to the end of the
command line.
Press Ctrl-U or Ctrl-X.
Delete all characters from the cursor to the beginning of
the command line.
Press Ctrl-W.
Delete the word to the left of the cursor.
Press Esc D.
Delete from the cursor to the end of the word.
Press Esc C.
Capitalize at the cursor.
Press Esc L.
Change the word at the cursor to lowercase.
Press Esc U.
Capitalize letters from the cursor to the end of the word.
Designate a particular keystroke as
Press Ctrl-V or Esc Q.
an executable command, perhaps as a
shortcut.
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Table 2-5
Editing Commands through Keystrokes (continued)
Capability
Keystroke1
Purpose
Scroll down a line or screen on
displays that are longer than the
terminal screen can display.
Press the Return key.
Scroll down one line.
Press the Space bar.
Scroll down one screen.
Press Ctrl-L or Ctrl-R.
Redisplay the current command line.
Note
The More prompt is used for
any output that has more
lines than can be displayed
on the terminal screen,
including show command
output. You can use the
Return and Space bar
keystrokes whenever you see
the More prompt.
Redisplay the current command line
if the switch suddenly sends a
message to your screen.
1. The arrow keys function only on ANSI-compatible terminals such as VT100s.
Editing Command Lines that Wrap
You can use a wraparound feature for commands that extend beyond a single line on the screen. When
the cursor reaches the right margin, the command line shifts ten spaces to the left. You cannot see the
first ten characters of the line, but you can scroll back and check the syntax at the beginning of the
command. The keystroke actions are optional.
To scroll back to the beginning of the command entry, press Ctrl-B or the left arrow key repeatedly. You
can also press Ctrl-A to immediately move to the beginning of the line.
The arrow keys function only on ANSI-compatible terminals such as VT100s.
In this example, the access-list global configuration command entry extends beyond one line. When the
cursor first reaches the end of the line, the line is shifted ten spaces to the left and redisplayed. The dollar
sign ($) shows that the line has been scrolled to the left. Each time the cursor reaches the end of the line,
the line is again shifted ten spaces to the left.
Switch(config)#
Switch(config)#
Switch(config)#
Switch(config)#
access-list 101 permit tcp 131.108.2.5 255.255.255.0 131.108.1
$ 101 permit tcp 131.108.2.5 255.255.255.0 131.108.1.20 255.25
$t tcp 131.108.2.5 255.255.255.0 131.108.1.20 255.255.255.0 eq
$108.2.5 255.255.255.0 131.108.1.20 255.255.255.0 eq 45
After you complete the entry, press Ctrl-A to check the complete syntax before pressing the Return key
to execute the command. The dollar sign ($) appears at the end of the line to show that the line has been
scrolled to the right:
Switch(config)# access-list 101 permit tcp 131.108.2.5 255.255.255.0 131.108.1$
The software assumes you have a terminal screen that is 80 columns wide. If you have a width other than
that, use the terminal width privileged EXEC command to set the width of your terminal.
Use line wrapping with the command history feature to recall and modify previous complex command
entries. For information about recalling previous command entries, see the “Editing Commands through
Keystrokes” section on page 2-7.
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Searching and Filtering Output of show and more Commands
Searching and Filtering Output of show and more Commands
You can search and filter the output for show and more commands. This is useful when you need to sort
through large amounts of output or if you want to exclude output that you do not need to see. Using these
commands is optional.
To use this functionality, enter a show or more command followed by the pipe character (|), one of the
keywords begin, include, or exclude, and an expression that you want to search for or filter out:
command | {begin | include | exclude} regular-expression
Expressions are case sensitive. For example, if you enter | exclude output, the lines that contain output
are not displayed, but the lines that contain Output appear.
This example shows how to include in the output display only lines where the expression protocol
appears:
Switch# show interfaces | include protocol
Vlan1 is up, line protocol is up
Vlan10 is up, line protocol is down
GigabitEthernet0/1 is up, line protocol is down
GigabitEthernet0/2 is up, line protocol is up
Accessing the CLI
You can access the CLI through a console connection, through Telnet, or by using the browser.
Before you can access the CLI, you must connect a terminal or PC to the switch console port and power
on the switch, as described in the hardware installation guide that shipped with your switch. Then, to
understand the boot up process and the options available for assigning IP information, see Chapter 3,
“Assigning the Switch IP Address and Default Gateway.”
If your switch is already configured, you can access the CLI through a local console connection or
through a remote Telnet session, but your switch must first be configured for this type of access. For
more information, see the “Setting a Telnet Password for a Terminal Line” section on page 7-6.
You can use one of these methods to establish a connection with the switch:
•
Connect the switch console port to a management station or dial-up modem. For information about
connecting to the console port, see the switch hardware installation guide.
•
Use any Telnet TCP/IP or encrypted Secure Shell (SSH) package from a remote management
station. The switch must have network connectivity with the Telnet or SSH client, and the switch
must have an enable secret password configured.
For information about configuring the switch for Telnet access, see the “Setting a Telnet Password
for a Terminal Line” section on page 7-6. The switch supports up to 16 simultaneous Telnet sessions.
Changes made by one Telnet user are reflected in all other Telnet sessions.
For information about configuring the switch for SSH, see the “Configuring the Switch for Secure
Shell” section on page 7-43. The switch supports up to five simultaneous secure SSH sessions.
After you connect through the console port, through a Telnet session or through an SSH session, the
user EXEC prompt appears on the management station.
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Accessing the CLI
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CH A P T E R
3
Assigning the Switch IP Address and Default
Gateway
This chapter describes how to create the initial switch configuration (for example, assigning the IP
address and default gateway information) by using a variety of automatic and manual methods. It also
describes how to modify the switch startup configuration.
Note
For complete syntax and usage information for the commands used in this chapter, see the command
reference for this release and the Cisco IOS IP Command Reference, Volume 1 of 3: Addressing and
Services from Cisco.com.
This chapter consists of these sections:
Note
•
Understanding the Bootup Process, page 3-1
•
Assigning Switch Information, page 3-2
•
Checking and Saving the Running Configuration, page 3-15
•
Modifying the Startup Configuration, page 3-17
•
Scheduling a Reload of the Software Image, page 3-22
Information in this chapter about configuring IP addresses and DHCP is specific to IP Version 4 (IPv4).
Understanding the Bootup Process
To start your switch, you need to follow the procedures in the getting started guide or the hardware
installation guide for installing the switch and setting up the initial switch configuration (IP address,
subnet mask, default gateway, secret and Telnet passwords, and so forth).
The normal bootup process involves the operation of the bootloader software, which performs these
activities:
•
Performs low-level CPU initialization. It initializes the CPU registers, which control where physical
memory is mapped, its quantity, its speed, and so forth.
•
Performs power-on self-test (POST) for the CPU subsystem. It tests the CPU DRAM and the portion
of the flash device that makes up the flash file system.
•
Initializes the flash file system on the system board.
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•
Loads a default operating system software image into memory and boots the switch.
The bootloader provides access to the flash file system before the operating system is loaded. Normally,
the bootloader is used only to load, uncompress, and launch the operating system. After the bootloader
gives the operating system control of the CPU, the bootloader is not active until the next system reset or
power-on.
The bootloader also provides trap-door access into the system if the operating system has problems
serious enough that it cannot be used. The trap-door mechanism provides enough access to the system
so that if it is necessary, you can format the flash file system, reinstall the operating system software
image by using the Xmodem Protocol, recover from a lost or forgotten password, and finally restart the
operating system. For more information, see the “Recovering from a Software Failure” section on
page 42-2 and the “Recovering from a Lost or Forgotten Password” section on page 42-4.
Note
You can disable password recovery. For more information, see the “Disabling Password Recovery”
section on page 7-5.
Before you can assign switch information, make sure you have connected a PC or terminal to the console
port, and configured the PC or terminal-emulation software baud rate and character format to match
these of the switch console port:
•
Baud rate default is 9600.
•
Data bits default is 8.
Note
If the data bits option is set to 8, set the parity option to none.
•
Stop bits default is 1.
•
Parity settings default is none.
Assigning Switch Information
You can assign IP information through the switch setup program, through a DHCP server, or manually.
Use the switch setup program if you want to be prompted for specific IP information. With this program,
you can also configure a hostname and an enable secret password. It gives you the option of assigning a
Telnet password (to provide security during remote management) and configuring your switch as a
standalone switch. For more information about the setup program, see the hardware installation guide.
Use a DHCP server for centralized control and automatic assignment of IP information after the server
is configured.
Note
If you are using DHCP, do not respond to any of the questions in the setup program until the switch
receives the dynamically assigned IP address and reads the configuration file.
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Assigning Switch Information
If you are an experienced user familiar with the switch configuration steps, manually configure the
switch. Otherwise, use the setup program described previously.
These sections contain this configuration information:
•
Default Switch Information, page 3-3
•
Understanding DHCP-Based Autoconfiguration, page 3-3
•
Manually Assigning IP Information, page 3-14
Default Switch Information
Table 3-1 shows the default switch information.
Table 3-1
Default Switch Information
Feature
Default Setting
IP address and subnet mask
No IP address or subnet mask are defined.
Default gateway
No default gateway is defined.
Enable secret password
No password is defined.
Hostname
The factory-assigned default hostname is Switch.
Telnet password
No password is defined.
Understanding DHCP-Based Autoconfiguration
DHCP provides configuration information to Internet hosts and internetworking devices. This protocol
consists of two components: one for delivering configuration parameters from a DHCP server to a device
and a mechanism for allocating network addresses to devices. DHCP is built on a client-server model,
in which designated DHCP servers allocate network addresses and deliver configuration parameters to
dynamically configured devices. The switch can act as both a DHCP client and a DHCP server.
During DHCP-based autoconfiguration, your switch (DHCP client) is automatically configured at
startup with IP address information and a configuration file.
With DHCP-based autoconfiguration, no DHCP client-side configuration is needed on your switch.
However, you need to configure the DHCP server for various lease options associated with IP addresses.
If you are using DHCP to relay the configuration file location on the network, you might also need to
configure a Trivial File Transfer Protocol (TFTP) server and a Domain Name System (DNS) server.
The DHCP server for your switch can be on the same LAN or on a different LAN than the switch. If the
DHCP server is running on a different LAN, you should configure a DHCP relay device between your
switch and the DHCP server. A relay device forwards broadcast traffic between two directly connected
LANs. A router does not forward broadcast packets, but it forwards packets based on the destination IP
address in the received packet.
DHCP-based autoconfiguration replaces the BOOTP client functionality on your switch.
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DHCP Client Request Process
When you boot up your switch, the DHCP client is invoked and requests configuration information from
a DHCP server when the configuration file is not present on the switch. If the configuration file is present
and the configuration includes the ip address dhcp interface configuration command on specific routed
interfaces, the DHCP client is invoked and requests the IP address information for those interfaces.
Figure 3-1 shows the sequence of messages that are exchanged between the DHCP client and the DHCP
server.
Figure 3-1
DHCP Client and Server Message Exchange
DHCPDISCOVER (broadcast)
Switch A
DHCPOFFER (unicast)
DHCP server
DHCPACK (unicast)
51807
DHCPREQUEST (broadcast)
The client, Switch A, broadcasts a DHCPDISCOVER message to locate a DHCP server. The DHCP
server offers configuration parameters (such as an IP address, subnet mask, gateway IP address, DNS IP
address, a lease for the IP address, and so forth) to the client in a DHCPOFFER unicast message.
In a DHCPREQUEST broadcast message, the client returns a formal request for the offered
configuration information to the DHCP server. The formal request is broadcast so that all other DHCP
servers that received the DHCPDISCOVER broadcast message from the client can reclaim the IP
addresses that they offered to the client.
The DHCP server confirms that the IP address has been allocated to the client by returning a DHCPACK
unicast message to the client. With this message, the client and server are bound, and the client uses
configuration information received from the server. The amount of information the switch receives
depends on how you configure the DHCP server. For more information, see the “Configuring the TFTP
Server” section on page 3-7.
If the configuration parameters sent to the client in the DHCPOFFER unicast message are invalid (a
configuration error exists), the client returns a DHCPDECLINE broadcast message to the DHCP server.
The DHCP server sends the client a DHCPNAK denial broadcast message, which means that the offered
configuration parameters have not been assigned, that an error has occurred during the negotiation of the
parameters, or that the client has been slow in responding to the DHCPOFFER message (the DHCP
server assigned the parameters to another client).
A DHCP client might receive offers from multiple DHCP or BOOTP servers and can accept any of the
offers; however, the client usually accepts the first offer it receives. The offer from the DHCP server is
not a guarantee that the IP address is allocated to the client; however, the server usually reserves the
address until the client has had a chance to formally request the address. If the switch accepts replies
from a BOOTP server and configures itself, the switch broadcasts, instead of unicasts, TFTP requests to
obtain the switch configuration file.
The DHCP hostname option allows a group of switches to obtain hostnames and a standard configuration
from the central management DHCP server. A client (switch) includes in its DCHPDISCOVER message
an option 12 field used to request a hostname and other configuration parameters from the DHCP server.
The configuration files on all clients are identical except for their DHCP-obtained hostnames.
If a client has a default hostname (the hostname name global configuration command is not configured
or the no hostname global configuration command is entered to remove the hostname), the DHCP
hostname option is not included in the packet when you enter the ip address dhcp interface
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configuration command. In this case, if the client receives the DCHP hostname option from the DHCP
interaction while acquiring an IP address for an interface, the client accepts the DHCP hostname option
and sets the flag to show that the system now has a hostname configured.
Understanding DHCP-based Autoconfiguration and Image Update
You can use the DHCP image upgrade features to configure a DHCP server to download both a new
image and a new configuration file to one or more switches in a network. This helps ensure that each
new switch added to a network receives the same image and configuration.
There are two types of DHCP image upgrades: DHCP autoconfiguration and DHCP auto-image update.
DHCP Autoconfiguration
DHCP autoconfiguration downloads a configuration file to one or more switches in your network from
a DHCP server. The downloaded configuration file becomes the running configuration of the switch. It
does not over write the bootup configuration saved in the flash, until you reload the switch.
DHCP Auto-Image Update
You can use DHCP auto-image upgrade with DHCP autoconfiguration to download both a configuration
and a new image to one or more switches in your network. The switch (or switches) downloading the
new configuration and the new image can be blank (or only have a default factory configuration loaded).
If the new configuration is downloaded to a switch that already has a configuration, the downloaded
configuration is appended to the configuration file stored on the switch. (Any existing configuration is
not overwritten by the downloaded one.)
Note
To enable a DHCP auto-image update on the switch, the TFTP server where the image and configuration
files are located must be configured with the correct option 67 (the configuration filename), option 66
(the DHCP server hostname) option 150 (the TFTP server address), and option 125 (description of the
file) settings.
For procedures to configure the switch as a DHCP server, see the “Configuring DHCP-Based
Autoconfiguration” section on page 3-6 and the “Configuring DHCP” section of the “IP addressing and
Services” section of the Cisco IOS IP Configuration Guide, Release 12.2.
After you install the switch in your network, the auto-image update feature starts. The downloaded
configuration file is saved in the running configuration of the switch, and the new image is downloaded
and installed on the switch. When you reboot the switch, the configuration is stored in the saved
configuration on the switch.
Limitations and Restrictions
These are the limitations:
•
The DHCP-based autoconfiguration with a saved configuration process stops if there is not at least
one Layer 3 interface in an up state without an assigned IP address in the network.
•
Unless you configure a timeout, the DHCP-based autoconfiguration with a saved configuration
feature tries indefinitely to download an IP address.
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•
Note
The auto-install process stops if a configuration file cannot be downloaded or it the configuration
file is corrupted.
The configuration file that is downloaded from TFTP is merged with the existing configuration in the
running configuration but is not saved in the NVRAM unless you enter the write memory or
copy running-configuration startup-configuration privileged EXEC command. Note that if the
downloaded configuration is saved to the startup configuration, the feature is not triggered during
subsequent system restarts.
Configuring DHCP-Based Autoconfiguration
These sections contain this configuration information:
•
DHCP Server Configuration Guidelines, page 3-6
•
Configuring the TFTP Server, page 3-7
•
Configuring the DNS, page 3-7
•
Configuring the Relay Device, page 3-8
•
Obtaining Configuration Files, page 3-9
•
Example Configuration, page 3-10
If your DHCP server is a Cisco device, for additional information about configuring DHCP, see the
“Configuring DHCP” section of the “IP Addressing and Services” section of the Cisco IOS IP
Configuration Guide from Cisco.com.
DHCP Server Configuration Guidelines
Follow these guidelines if you are configuring a device as a DHCP server:
You should configure the DHCP server with reserved leases that are bound to each switch by the switch
hardware address.
If you want the switch to receive IP address information, you must configure the DHCP server with these
lease options:
•
IP address of the client (required)
•
Subnet mask of the client (required)
•
DNS server IP address (optional)
•
Router IP address (default gateway address to be used by the switch) (required)
If you want the switch to receive the configuration file from a TFTP server, you must configure the
DHCP server with these lease options:
•
TFTP server name (required)
•
Boot filename (the name of the configuration file that the client needs) (recommended)
•
Hostname (optional)
Depending on the settings of the DHCP server, the switch can receive IP address information, the
configuration file, or both.
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If you do not configure the DHCP server with the lease options described previously, it replies to client
requests with only those parameters that are configured. If the IP address and the subnet mask are not in
the reply, the switch is not configured. If the router IP address or the TFTP server name are not found,
the switch might send broadcast, instead of unicast, TFTP requests. Unavailability of other lease options
does not affect autoconfiguration.
The switch can act as a DHCP server. By default, the Cisco IOS DHCP server and relay agent features
are enabled on your switch but are not configured. These features are not operational. If your DHCP
server is a Cisco device, for additional information about configuring DHCP, see the “Configuring
DHCP” section of the “IP Addressing and Services” section of the Cisco IOS IP Configuration Guide
from the Cisco.com page under Documentation > Cisco IOS Software > 12.2 Mainline >
Configuration Guides.
Configuring the TFTP Server
Based on the DHCP server configuration, the switch attempts to download one or more configuration
files from the TFTP server. If you configured the DHCP server to respond to the switch with all the
options required for IP connectivity to the TFTP server, and if you configured the DHCP server with a
TFTP server name, address, and configuration filename, the switch attempts to download the specified
configuration file from the specified TFTP server.
If you did not specify the configuration filename, the TFTP server, or if the configuration file could not
be downloaded, the switch attempts to download a configuration file by using various combinations of
filenames and TFTP server addresses. The files include the specified configuration filename (if any) and
these files: network-config, cisconet.cfg, hostname.config, or hostname.cfg, where hostname is the
switch’s current hostname. The TFTP server addresses used include the specified TFTP server address
(if any) and the broadcast address (255.255.255.255).
For the switch to successfully download a configuration file, the TFTP server must contain one or more
configuration files in its base directory. The files can include these files:
•
The configuration file named in the DHCP reply (the actual switch configuration file).
•
The network-confg or the cisconet.cfg file (known as the default configuration files).
•
The router-confg or the ciscortr.cfg file (These files contain commands common to all switches.
Normally, if the DHCP and TFTP servers are properly configured, these files are not accessed.)
If you specify the TFTP server name in the DHCP server-lease database, you must also configure the
TFTP server name-to-IP-address mapping in the DNS-server database.
If the TFTP server to be used is on a different LAN from the switch, or if it is to be accessed by the switch
through the broadcast address (which occurs if the DHCP server response does not contain all the
required information described previously), a relay must be configured to forward the TFTP packets to
the TFTP server. For more information, see the “Configuring the Relay Device” section on page 3-8. The
preferred solution is to configure the DHCP server with all the required information.
Configuring the DNS
The DHCP server uses the DNS server to resolve the TFTP server name to an IP address. You must
configure the TFTP server name-to-IP address map on the DNS server. The TFTP server contains the
configuration files for the switch.
You can configure the IP addresses of the DNS servers in the lease database of the DHCP server from
where the DHCP replies will retrieve them. You can enter up to two DNS server IP addresses in the lease
database.
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The DNS server can be on the same or on a different LAN as the switch. If it is on a different LAN, the
switch must be able to access it through a router.
Configuring the Relay Device
You must configure a relay device, also referred to as a relay agent, when a switch sends broadcast
packets that require a response from a host on a different LAN. Examples of broadcast packets that the
switch might send are DHCP, DNS, and in some cases, TFTP packets. You must configure this relay
device to forward received broadcast packets on an interface to the destination host.
If the relay device is a Cisco router, enable IP routing (ip routing global configuration command), and
configure helper addresses by using the ip helper-address interface configuration command.
For example, in Figure 3-2, configure the router interfaces as follows:
On interface 10.0.0.2:
router(config-if)# ip helper-address 20.0.0.2
router(config-if)# ip helper-address 20.0.0.3
router(config-if)# ip helper-address 20.0.0.4
On interface 20.0.0.1
router(config-if)# ip helper-address 10.0.0.1
Note
If the switch is acting as the relay device, configure the interface as a routed port. For more information,
see the “Routed Ports” section on page 10-4 and the “Configuring Layer 3 Interfaces” section on
page 10-17.
Figure 3-2
Relay Device Used in Autoconfiguration
Switch
(DHCP client)
Cisco router
(Relay)
10.0.0.2
10.0.0.1
DHCP server
20.0.0.3
TFTP server
20.0.0.4
DNS server
49068
20.0.0.2
20.0.0.1
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Obtaining Configuration Files
Depending on the availability of the IP address and the configuration filename in the DHCP reserved
lease, the switch obtains its configuration information in these ways:
•
The IP address and the configuration filename is reserved for the switch and provided in the DHCP
reply (one-file read method).
The switch receives its IP address, subnet mask, TFTP server address, and the configuration
filename from the DHCP server. The switch sends a unicast message to the TFTP server to retrieve
the named configuration file from the base directory of the server and upon receipt, it completes its
bootup process.
•
The IP address and the configuration filename is reserved for the switch, but the TFTP server
address is not provided in the DHCP reply (one-file read method).
The switch receives its IP address, subnet mask, and the configuration filename from the DHCP
server. The switch sends a broadcast message to a TFTP server to retrieve the named configuration
file from the base directory of the server, and upon receipt, it completes its bootup process.
•
Only the IP address is reserved for the switch and provided in the DHCP reply. The configuration
filename is not provided (two-file read method).
The switch receives its IP address, subnet mask, and the TFTP server address from the DHCP server.
The switch sends a unicast message to the TFTP server to retrieve the network-confg or cisconet.cfg
default configuration file. (If the network-confg file cannot be read, the switch reads the cisconet.cfg
file.)
The default configuration file contains the hostnames-to-IP-address mapping for the switch. The
switch fills its host table with the information in the file and obtains its hostname. If the hostname
is not found in the file, the switch uses the hostname in the DHCP reply. If the hostname is not
specified in the DHCP reply, the switch uses the default Switch as its hostname.
After obtaining its hostname from the default configuration file or the DHCP reply, the switch reads
the configuration file that has the same name as its hostname (hostname-confg or hostname.cfg,
depending on whether network-confg or cisconet.cfg was read earlier) from the TFTP server. If the
cisconet.cfg file is read, the filename of the host is truncated to eight characters.
If the switch cannot read the network-confg, cisconet.cfg, or the hostname file, it reads the
router-confg file. If the switch cannot read the router-confg file, it reads the ciscortr.cfg file.
Note
The switch broadcasts TFTP server requests if the TFTP server is not obtained from the DHCP replies,
if all attempts to read the configuration file through unicast transmissions fail, or if the TFTP server
name cannot be resolved to an IP address.
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Example Configuration
Figure 3-3 shows a sample network for retrieving IP information by using DHCP-based autoconfiguration.
Figure 3-3
DHCP-Based Autoconfiguration Network Example
Switch 1
Switch 2
Switch 3
Switch 4
00e0.9f1e.2001 00e0.9f1e.2002 00e0.9f1e.2003 00e0.9f1e.2004
Cisco router
10.0.0.10
DHCP server
10.0.0.2
DNS server
10.0.0.3
TFTP server
(tftpserver)
111394
10.0.0.1
Table 3-2 shows the configuration of the reserved leases on the DHCP server.
Table 3-2
DHCP Server Configuration
Switch A
Switch B
Switch C
Switch D
Binding key (hardware address)
00e0.9f1e.2001
00e0.9f1e.2002
00e0.9f1e.2003
00e0.9f1e.2004
IP address
10.0.0.21
10.0.0.22
10.0.0.23
10.0.0.24
Subnet mask
255.255.255.0
255.255.255.0
255.255.255.0
255.255.255.0
Router address
10.0.0.10
10.0.0.10
10.0.0.10
10.0.0.10
DNS server address
10.0.0.2
10.0.0.2
10.0.0.2
10.0.0.2
TFTP server name
tftpserver or
10.0.0.3
tftpserver or
10.0.0.3
tftpserver or
10.0.0.3
tftpserver or
10.0.0.3
Boot filename (configuration file)
(optional)
switcha-confg
switchb-confg
switchc-confg
switchd-confg
Hostname (optional)
switcha
switchb
switchc
switchd
DNS Server Configuration
The DNS server maps the TFTP server name tftpserver to IP address 10.0.0.3.
TFTP Server Configuration (on UNIX)
The TFTP server base directory is set to /tftpserver/work/. This directory contains the network-confg file
used in the two-file read method. This file contains the hostname to be assigned to the switch based on
its IP address. The base directory also contains a configuration file for each switch (switcha-confg,
switchb-confg, and so forth) as shown in this display:
prompt> cd /tftpserver/work/
prompt> ls
network-confg
switcha-confg
switchb-confg
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switchc-confg
switchd-confg
prompt> cat network-confg
ip host switcha 10.0.0.21
ip host switchb 10.0.0.22
ip host switchc 10.0.0.23
ip host switchd 10.0.0.24
DHCP Client Configuration
No configuration file is present on Switch A through Switch D.
Configuration Explanation
In Figure 3-3, Switch A reads its configuration file as follows:
•
It obtains its IP address 10.0.0.21 from the DHCP server.
•
If no configuration filename is given in the DHCP server reply, Switch A reads the network-confg
file from the base directory of the TFTP server.
•
It adds the contents of the network-confg file to its host table.
•
It reads its host table by indexing its IP address 10.0.0.21 to its hostname (switcha).
•
It reads the configuration file that corresponds to its hostname; for example, it reads switch1-confg
from the TFTP server.
Switches B through D retrieve their configuration files and IP addresses in the same way.
Configuring the DHCP Auto Configuration and Image Update Features
Using DHCP to download a new image and a new configuration to a switch requires that you configure
at least two switches: One switch acts as a DHCP and TFTP server. The client switch is configured to
download either a new configuration file or a new configuration file and a new image file.
Configuring DHCP Autoconfiguration (Only Configuration File)
Beginning in privileged EXEC mode, follow these steps to configure DHCP autoconfiguration of the
TFTP and DHCP settings on a new switch to download a new configuration file.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
ip dhcp poolname
Create a name for the DHCP Server address pool, and enter DHCP
pool configuration mode.
Step 3
bootfile filename
Specify the name of the configuration file that is used as a boot image.
Step 4
network network-number mask
prefix-length
Specify the subnet network number and mask of the DHCP address
pool.
Note
The prefix length specifies the number of bits that comprise
the address prefix. The prefix is an alternative way of
specifying the network mask of the client. The prefix length
must be preceded by a forward slash (/).
Step 5
default-router address
Specify the IP address of the default router for a DHCP client.
Step 6
option 150 address
Specify the IP address of the TFTP server.
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Command
Purpose
Step 7
exit
Return to global configuration mode.
Step 8
tftp-server flash:filename.text
Specify the configuration file on the TFTP server.
Step 9
interface interface-id
Specify the address of the client that will receive the configuration
file.
Step 10
no switchport
Put the interface into Layer 3 mode.
Step 11
ip address address mask
Specify the IP address and mask for the interface.
Step 12
end
Return to privileged EXEC mode.
Step 13
copy running-config startup-config
(Optional) Save your entries in the configuration file.
This example shows how to configure a switch as a DHCP server so that it will download a configuration file:
Switch# configure terminal
Switch(config)# ip dhcp pool pool1
Switch(dhcp-config)# network 10.10.10.0 255.255.255.0
Switch(dhcp-config)# bootfile config-boot.text
Switch(dhcp-config)# default-router 10.10.10.1
Switch(dhcp-config)# option 150 10.10.10.1
Switch(dhcp-config)# exit
Switch(config)# tftp-server flash:config-boot.text
Switch(config)# interface gigabitethernet1/0/4
Switch(config-if)# no switchport
Switch(config-if)# ip address 10.10.10.1 255.255.255.0
Switch(config-if)# end
Configuring DHCP Auto-Image Update (Configuration File and Image)
Beginning in privileged EXEC mode, follow these steps to configure DHCP autoconfiguration to
configure TFTP and DHCP settings on a new switch to download a new image and a new configuration
file.
Note
Before following the steps in this table, you must create a text file (for example, autoinstall_dhcp) that
will be uploaded to the switch. In the text file, put the name of the image that you want to download (for
example, c3030mipbase-mz.122-44.3.SE.tar). This image must be a tar and not a bin file.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
ip dhcp pool name
Create a name for the DHCP server address pool and enter DHCP pool
configuration mode.
Step 3
bootfile filename
Specify the name of the file that is used as a boot image.
Step 4
network network-number mask
prefix-length
Specify the subnet network number and mask of the DHCP address pool.
default-router address
Specify the IP address of the default router for a DHCP client.
Step 5
Note
The prefix length specifies the number of bits that comprise the
address prefix. The prefix is an alternative way of specifying the
network mask of the client. The prefix length must be preceded
by a forward slash (/).
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Command
Purpose
Step 6
option 150 address
Specify the IP address of the TFTP server.
Step 7
option 125 hex
Specify the path to the text file that describes the path to the image file.
Step 8
copy tftp flash filename.txt
Upload the text file to the switch.
Step 9
copy tftp flash imagename.tar
Upload the tarfile for the new image to the switch.
Step 10
exit
Return to global configuration mode.
Step 11
tftp-server flash:config.text
Specify the Cisco IOS configuration file on the TFTP server.
Step 12
tftp-server flash:imagename.tar
Specify the image name on the TFTP server.
Step 13
tftp-server flash:filename.txt
Specify the text file that contains the name of the image file to download
Step 14
interface interface-id
Specify the address of the client that will receive the configuration file.
Step 15
no switchport
Put the interface into Layer 3 mode.
Step 16
ip address address mask
Specify the IP address and mask for the interface.
Step 17
end
Return to privileged EXEC mode.
Step 18
copy running-config startup-config
(Optional) Save your entries in the configuration file.
This example shows how to configure a switch as a DHCP server so it downloads a configuration file:
Switch# config terminal
Switch(config)# ip dhcp pool pool1
Switch(dhcp-config)# network 10.10.10.0 255.255.255.0
Switch(dhcp-config)# bootfile config-boot.text
Switch(dhcp-config)# default-router 10.10.10.1
Switch(dhcp-config)# option 150 10.10.10.1
Switch(dhcp-config)# option 125 hex
0000.0009.0a05.08661.7574.6f69.6e73.7461.6c6c.5f64.686370
Switch(dhcp-config)# exit
Switch(config)# tftp-server flash:config-boot.text
Switch(config)# tftp-server flash:c3750m-ipservices-mz.122-44.3.SE.tar
Switch(config)# tftp-server flash:boot-config.text
Switch(config)# tftp-server flash: autoinstall_dhcp
Switch(config)# interface gigabitEthernet1/0/4
Switch(config-if)# no switchport
Switch(config-if)# ip address 10.10.10.1 255.255.255.0
Switch(config-if)# end
Configuring the Client
Beginning in privileged EXEC mode, follow these steps to configure a switch to download a
configuration file and new image from a DHCP server:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
boot host dhcp
Enable autoconfiguration with a saved configuration.
Step 3
boot host retry timeout timeout-value
(Optional) Set the amount of time the system tries to
download a configuration file.
Note
If you do not set a timeout the system will
indefinitely try to obtain an IP address from the
DHCP server.
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Command
Purpose
Step 4
banner config-save ^C warning-message ^C
(Optional) Create warning messages to be displayed
when you try to save the configuration file to NVRAM.
Step 5
end
Return to privileged EXEC mode.
Step 6
show boot
Verify the configuration.
This example uses a Layer 3 SVI interface on VLAN 99 to enable DHCP-based autoconfiguration with
a saved configuration:
Switch# configure terminal
Switch(conf)# boot host dhcp
Switch(conf)# boot host retry timeout 300
Switch(conf)# banner config-save ^C Caution - Saving Configuration File to NVRAM May Cause
You to Nolonger Automatically Download Configuration Files at Reboot^C
Switch(config)# vlan 99
Switch(config-vlan)# interface vlan 99
Switch(config-if)# no shutdown
Switch(config-if)# end
Switch# show boot
BOOT path-list:
Config file:
flash:/config.text
Private Config file: flash:/private-config.text
Enable Break:
no
Manual Boot:
no
HELPER path-list:
NVRAM/Config file
buffer size:
32768
Timeout for Config
Download:
300 seconds
Config Download
via DHCP:
enabled (next boot: enabled)
Switch#
Note
You should only configure and enable the Layer 3 interface. Do not assign an IP address or DHCP-based
autoconfiguration with a saved configuration.
Manually Assigning IP Information
Beginning in privileged EXEC mode, follow these steps to manually assign IP information to multiple
switched virtual interfaces (SVIs):
Note
You can also manually assign IP information to a port if you first put the port into Layer 3 mode by using
the no switchport interface configuration command.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface vlan vlan-id
Enter interface configuration mode, and enter the VLAN to which the IP
information is assigned. The VLAN range is 1 to 4094.
Step 3
ip address ip-address subnet-mask
Enter the IP address and subnet mask.
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Command
Purpose
Step 4
exit
Return to global configuration mode.
Step 5
ip default-gateway ip-address
Enter the IP address of the next-hop router interface that is directly
connected to the switch where a default gateway is being configured. The
default gateway receives IP packets with unresolved destination IP
addresses from the switch.
Once the default gateway is configured, the switch has connectivity to the
remote networks with which a host needs to communicate.
Note
When your switch is configured to route with IP, it does not need
to have a default gateway set.
Step 6
end
Return to privileged EXEC mode.
Step 7
show interfaces vlan vlan-id
Verify the configured IP address.
Step 8
show ip redirects
Verify the configured default gateway.
Step 9
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To remove the switch IP address, use the no ip address interface configuration command. If you are
removing the address through a Telnet session, your connection to the switch will be lost. To remove the
default gateway address, use the no ip default-gateway global configuration command.
For information on setting the switch system name, protecting access to privileged EXEC commands,
and setting time and calendar services, see Chapter 5, “Administering the Switch”.
Checking and Saving the Running Configuration
You can check the configuration settings that you entered or changes that you made by entering this
privileged EXEC command:
Switch# show running-config
Building configuration...
Current configuration : 1833 bytes
!
version 12.2
no service pad
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
!
no aaa new-model
ip subnet-zero
!
no file verify auto
!
spanning-tree mode pvst
spanning-tree extend system-id
!
vlan internal allocation policy ascending
!
interface GigabitEthernet0/1
switchport trunk encapsulation dot1q
switchport mode trunk
speed 1000
spanning-tree portfast
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!
interface GigabitEthernet0/2
switchport access vlan 2
speed 1000
storm-control unicast level 50.00
storm-control action shutdown
spanning-tree portfast
!
<output truncated>
!
interface Vlan1
ip address 192.168.100.21 255.255.255.0
no ip route-cache
!
ip http server
ip http secure-server
!
control-plane
!
!
line con 0
exec-timeout 0 0
line vty 0 4
no login
line vty 5 15
no login
!
end
To store the configuration or changes you have made to your startup configuration in flash memory, enter
this privileged EXEC command:
Switch# copy running-config startup-config
Destination filename [startup-config]?
Building configuration...
This command saves the configuration settings that you made. If you fail to do this, your configuration
will be lost the next time you reload the system. To display information stored in the NVRAM section
of flash memory, use the show startup-config or more startup-config privileged EXEC command.
For more information about alternative locations from which to copy the configuration file, see
Appendix 44, “Working with the Cisco IOS File System, Configuration Files, and Software Images.”
Configuring the NVRAM Buffer Size
The default NVRAM buffer size is 512 KB. In some cases, the configuration file might be too large to
save to NVRAM. Typically, this occurs when you have many switches in a switch stack. You can
configure the size of the NVRAM buffer to support larger configuration files. The new NVRAM buffer
size is synced to all current and new member switches.
Note
After you configure the NVRAM buffer size, reload the switch or switch stack.
When you add a switch to a stack and the NVRAM size differs, the new switch syncs with the stack and
reloads automatically.
Beginning in privileged EXEC mode, follow these steps to configure the NVRAM buffersize:
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Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
boot buffersize size
Configure the NVRAM buffersize in KB. The valid range
for size is from 4096 to 1048576.
Step 3
end
Return to privileged EXEC mode.
Step 4
show boot
Verify the configuration.
This example shows how to configure the NVRAM buffer size:
Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# boot buffersize 524288
Switch(config)# end
Switch# show boot
BOOT path-list
:
Config file
: flash:/config.text
Private Config file : flash:/private-config.text
Enable Break
: no
Manual Boot
: no
HELPER path-list
:
Auto upgrade
: yes
Auto upgrade path
:
NVRAM/Config file
buffer size:
524288
Timeout for Config
Download:
300 seconds
Config Download
via DHCP:
enabled (next boot: enabled)
Switch#
Modifying the Startup Configuration
These sections describe how to modify the switch startup configuration:
•
Default Bootup Configuration, page 3-18
•
Automatically Downloading a Configuration File, page 3-18
•
Booting Up Manually, page 3-19
•
Booting Up a Specific Software Image, page 3-19
•
Controlling Environment Variables, page 3-20
See also Appendix 44, “Working with the Cisco IOS File System, Configuration Files, and Software
Images,” for information about switch configuration files.
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Default Bootup Configuration
Table 3-3 shows the default bootup configuration.
Table 3-3
Default Bootup Configuration
Feature
Default Setting
Operating system software image
The switch attempts to automatically boot up the system using information in the
BOOT environment variable. If the variable is not set, the switch attempts to load and
execute the first executable image it can by performing a recursive, depth-first search
throughout the flash file system.
The Cisco IOS image is stored in a directory that has the same name as the image file
(excluding the .bin extension).
In a depth-first search of a directory, each encountered subdirectory is completely
searched before continuing the search in the original directory.
Configuration file
Configured switches use the config.text file stored on the system board in flash
memory.
A new switch has no configuration file.
Automatically Downloading a Configuration File
You can automatically download a configuration file to your switch by using the DHCP-based
autoconfiguration feature. For more information, see the “Understanding DHCP-Based
Autoconfiguration” section on page 3-3.
Specifying the Filename to Read and Write the System Configuration
By default, the Cisco IOS software uses the file config.text to read and write a nonvolatile copy of the
system configuration. However, you can specify a different filename, which will be loaded during the
next bootup cycle.
Beginning in privileged EXEC mode, follow these steps to specify a different configuration filename:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
boot config-file flash:/file-url
Specify the configuration file to load during the next bootup cycle.
For file-url, specify the path (directory) and the configuration
filename.
Filenames and directory names are case sensitive.
Step 3
end
Return to privileged EXEC mode.
Step 4
show boot
Verify your entries.
The boot config-file global configuration command changes the
setting of the CONFIG_FILE environment variable.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
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Modifying the Startup Configuration
To return to the default setting, use the no boot config-file global configuration command.
Booting Up Manually
By default, the switch automatically boots up; however, you can configure it to manually boot up.
Beginning in privileged EXEC mode, follow these steps to configure the switch to manually boot up
during the next bootup cycle:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
boot manual
Enable the switch to manually boot up during the next bootup cycle.
Step 3
end
Return to privileged EXEC mode.
Step 4
show boot
Verify your entries.
The boot manual global command changes the setting of the
MANUAL_BOOT environment variable.
The next time you reboot the system, the switch is in bootloader
mode, shown by the switch: prompt. To boot up the system, use the
boot filesystem:/file-url bootloader command.
•
For filesystem:, use flash: for the system board flash device.
•
For file-url, specify the path (directory) and the name of the
bootable image.
Filenames and directory names are case sensitive.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To disable manual booting up, use the no boot manual global configuration command.
Booting Up a Specific Software Image
By default, the switch attempts to automatically boot up the system using information in the BOOT
environment variable. If this variable is not set, the switch attempts to load and execute the first
executable image it can by performing a recursive, depth-first search throughout the flash file system. In
a depth-first search of a directory, each encountered subdirectory is completely searched before
continuing the search in the original directory. However, you can specify a specific image with which to
boot up the switch.
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Modifying the Startup Configuration
Beginning in privileged EXEC mode, follow these steps to configure the switch to boot up a specific
image during the next bootup cycle:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
boot system filesystem:/file-url
Configure the switch to boot up a specific image in flash memory during
the next bootup cycle.
•
For filesystem:, use flash: for the system board flash device.
•
For file-url, specify the path (directory) and the name of the bootable
image.
Filenames and directory names are case sensitive.
Step 3
end
Return to privileged EXEC mode.
Step 4
show boot
Verify your entries.
The boot system global command changes the setting of the BOOT
environment variable.
During the next bootup cycle, the switch attempts to automatically boot up
the system using information in the BOOT environment variable.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To return to the default setting, use the no boot system global configuration command.
Controlling Environment Variables
With a normally operating switch, you enter the bootloader mode only through a switch console
connection configured for 9600 b/s. The switch bootloader uses break-key detection to stop the
automatic boot sequence and to enter bootloader mode.
Note
The break-key character is different for each operating system.
On a SUN work station running UNIX, Ctrl-C is the break key.
On a PC running Hyperterminal on Windows XP or 2000, Ctrl-Break is the break key.
Cisco TAC has tabulated break keys for the most common operating systems and an alternative break
key sequence for those terminal emulators that do not support the break keys. See
http://www.cisco.com/warp/public/701/61.html#how-to for that list.
Follow these steps to enter bootloader mode:
Step 1
Connect a terminal or PC with terminal emulation software to the console port on the front of the switch.
For more information, see the switch hardware installation guide or the switch getting started guide.
Step 2
Set the line speed on the emulation software to 9600 baud.
Step 3
If the switch is already installed in a server chassis module bay, push the release latch on the front of the
switch to the open position.
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Step 4
Pull the switch partially out of the module bay until the power disconnects, and then push it in again.
The switch restarts when it reseats in the server chassis. The switch performs POST after power is
applied.
Step 5
Push the release latch on the front of the switch to the closed position.
Step 6
After the switch performs POST, the switch begins the autoboot process. Enter the break-key character
during the bootup sequence, when this message appears:
Initializing Flash
This example shows the messages that appear on the console after you enter a break key:
The system has been interrupted prior to initializing the flash file system.
The following commands will initialize the flash file system, and finish loading the
operating system software:
flash_init
load_helper
boot
After the message appears, the bootloader prompt resumes.
Note
You can also prompt the switch to reload the operating system by using the reload EXEC command or
by using the interface provided by the Dell Remote Access Controller/Modular Chassis (DRAC/MC)
management board.
See the “Connecting through the DRAC/MC” section of the Cisco Catalyst Blade Switch 3030 Getting
Started Guide for instructions on how to connect to the switch by using the DRAC/MC.
The switch bootloader software provides support for nonvolatile environment variables, which can be
used to control how the bootloader, or any other software running on the system, behaves. bootloader
environment variables are similar to environment variables that can be set on UNIX or DOS systems.
Environment variables that have values are stored in flash memory outside of the flash file system.
Each line in these files contains an environment variable name and an equal sign followed by the value
of the variable. A variable has no value if it is not listed in this file; it has a value if it is listed in the file
even if the value is a null string. A variable that is set to a null string (for example, “ ”) is a variable with
a value. Many environment variables are predefined and have default values.
Environment variables store two kinds of data:
•
Data that controls code, which does not read the Cisco IOS configuration file. For example, the name
of a bootloader helper file, which extends or patches the functionality of the bootloader can be stored
as an environment variable.
•
Data that controls code, which is responsible for reading the Cisco IOS configuration file. For
example, the name of the Cisco IOS configuration file can be stored as an environment variable.
You can change the settings of the environment variables by accessing the bootloader or by using Cisco
IOS commands. Under normal circumstances, it is not necessary to alter the setting of the environment
variables.
Note
For complete syntax and usage information for the bootloader commands and environment variables, see
the command reference for this release.
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Scheduling a Reload of the Software Image
Table 3-4 describes the function of the most common environment variables.
Table 3-4
Environment Variables
Variable
Bootloader Command
Cisco IOS Global Configuration Command
BOOT
set BOOT filesystem:/file-url ...
boot system filesystem:/file-url ...
A semicolon-separated list of executable files to Specifies the Cisco IOS image to load during the
next bootup cycle. This command changes the
try to load and execute when automatically
booting up the switch. If the BOOT environment setting of the BOOT environment variable.
variable is not set, the system attempts to load
and execute the first executable image it can find
by using a recursive, depth-first search through
the flash file system. If the BOOT variable is set
but the specified images cannot be loaded, the
system attempts to boot up the first bootable file
that it can find in the flash file system.
MANUAL_BOOT
set MANUAL_BOOT yes
boot manual
Decides whether the switch automatically or
manually boots up.
Enables manually booting up the switch during
the next bootup cycle and changes the setting of
the MANUAL_BOOT environment variable.
Valid values are 1, yes, 0, and no. If it is set to no
or 0, the bootloader attempts to automatically
boot up the system. If it is set to anything else,
you must manually boot up the switch from the
bootloader mode.
CONFIG_FILE
set CONFIG_FILE flash:/file-url
The next time you reboot the system, the switch is
in bootloader mode. To boot up the system, use the
boot flash:filesystem:/file-url bootloader
command, and specify the name of the bootable
image.
boot config-file flash:/file-url
Changes the filename that Cisco IOS uses to read Specifies the filename that Cisco IOS uses to read
and write a nonvolatile copy of the system
and write a nonvolatile copy of the system
configuration. This command changes the
configuration.
CONFIG_FILE environment variable.
Scheduling a Reload of the Software Image
You can schedule a reload of the software image to occur on the switch at a later time (for example, late
at night or during the weekend when the switch is used less), or you can synchronize a reload
network-wide (for example, to perform a software upgrade on all switches in the network).
Note
A scheduled reload must take place within approximately 24 days.
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Scheduling a Reload of the Software Image
Configuring a Scheduled Reload
To configure your switch to reload the software image at a later time, use one of these commands in
privileged EXEC mode:
•
reload in [hh:]mm [text]
This command schedules a reload of the software to take affect in the specified minutes or hours and
minutes. The reload must take place within approximately 24 days. You can specify the reason for
the reload in a string up to 255 characters in length.
•
reload at hh:mm [month day | day month] [text]
This command schedules a reload of the software to take place at the specified time (using a 24-hour
clock). If you specify the month and day, the reload is scheduled to take place at the specified time
and date. If you do not specify the month and day, the reload takes place at the specified time on the
current day (if the specified time is later than the current time) or on the next day (if the specified
time is earlier than the current time). Specifying 00:00 schedules the reload for midnight.
Note
Use the at keyword only if the switch system clock has been set (through Network Time
Protocol (NTP), the hardware calendar, or manually). The time is relative to the configured
time zone on the switch. To schedule reloads across several switches to occur
simultaneously, the time on each switch must be synchronized with NTP.
The reload command halts the system. If the system is not set to manually boot up, it reboots itself. Use
the reload command after you save the switch configuration information to the startup configuration
(copy running-config startup-config).
If your switch is configured for manual booting up, do not reload it from a virtual terminal. This
restriction prevents the switch from entering the bootloader mode and thereby taking it from the remote
user’s control.
If you modify your configuration file, the switch prompts you to save the configuration before reloading.
During the save operation, the system requests whether you want to proceed with the save if the
CONFIG_FILE environment variable points to a startup configuration file that no longer exists. If you
proceed in this situation, the system enters setup mode upon reload.
This example shows how to reload the software on the switch on the current day at 7:30 p.m:
Switch# reload at 19:30
Reload scheduled for 19:30:00 UTC Wed Jun 5 1996 (in 2 hours and 25 minutes)
Proceed with reload? [confirm]
This example shows how to reload the software on the switch at a future time:
Switch# reload at 02:00 jun 20
Reload scheduled for 02:00:00 UTC Thu Jun 20 1996 (in 344 hours and 53 minutes)
Proceed with reload? [confirm]
To cancel a previously scheduled reload, use the reload cancel privileged EXEC command.
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Scheduling a Reload of the Software Image
Displaying Scheduled Reload Information
To display information about a previously scheduled reload or to find out if a reload has been scheduled
on the switch, use the show reload privileged EXEC command.
It displays reload information including the time the reload is scheduled to occur and the reason for the
reload (if it was specified when the reload was scheduled).
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4
Configuring Cisco IOS Configuration Engine
This chapter describes how to configure the feature on the switch.
Note
For complete configuration information for the Cisco Configuration Engine, go to
http://www.cisco.com/en/US/products/sw/netmgtsw/ps4617/tsd_products_support_series_home.html
For complete syntax and usage information for the commands used in this chapter, go to the Cisco IOS
Network Management Command Reference, Release 12.4 at
http://www.cisco.com/en/US/docs/ios/netmgmt/command/reference/nm_book.html
This chapter consists of these sections:
•
Understanding Cisco Configuration Engine Software, page 4-1
•
Understanding Cisco IOS Agents, page 4-5
•
Configuring Cisco IOS Agents, page 4-6
•
Displaying CNS Configuration, page 4-14
Understanding Cisco Configuration Engine Software
The Cisco Configuration Engine is network management software that acts as a configuration service
for automating the deployment and management of network devices and services (see Figure 4-1). Each
Configuration Engine manages a group of Cisco devices (switches and routers) and the services that they
deliver, storing their configurations and delivering them as needed. The Configuration Engine automates
initial configurations and configuration updates by generating device-specific configuration changes,
sending them to the device, executing the configuration change, and logging the results.
The Configuration Engine supports standalone and server modes and has these CNS components:
•
Configuration service (web server, file manager, and namespace mapping server)
•
Event service (event gateway)
•
Data service directory (data models and schema)
In standalone mode, the Configuration Engine supports an embedded Directory Service. In this mode,
no external directory or other data store is required. In server mode, the Configuration Engine supports
the use of a user-defined external directory.
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Understanding Cisco Configuration Engine Software
Figure 4-1
Configuration Engine Architectural Overview
Service provider network
Configuration
engine
Data service
directory
Configuration server
Event service
141327
Web-based
user interface
Order entry
configuration management
These sections contain this conceptual information:
•
Configuration Service, page 4-2
•
Event Service, page 4-3
•
What You Should Know About the CNS IDs and Device Hostnames, page 4-3
Configuration Service
The Configuration Service is the core component of the Cisco Configuration Engine. It consists of a
configuration server that works with Cisco IOS CNS agents on the switch. The Configuration Service
delivers device and service configurations to the switch for initial configuration and mass
reconfiguration by logical groups. Switches receive their initial configuration from the Configuration
Service when they start up on the network for the first time.
The Configuration Service uses the CNS Event Service to send and receive configuration change events
and to send success and failure notifications.
The configuration server is a web server that uses configuration templates and the device-specific
configuration information stored in the embedded (standalone mode) or remote (server mode) directory.
Configuration templates are text files containing static configuration information in the form of CLI
commands. In the templates, variables are specified using Lightweight Directory Access Protocol
(LDAP) URLs that reference the device-specific configuration information stored in a directory.
The Cisco IOS agent can perform a syntax check on received configuration files and publish events to
show the success or failure of the syntax check. The configuration agent can either apply configurations
immediately or delay the application until receipt of a synchronization event from the configuration
server.
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Understanding Cisco Configuration Engine Software
Event Service
The Cisco Configuration Engine uses the Event Service for receipt and generation of configuration
events. The event agent is on the switch and facilitates the communication between the switch and the
event gateway on the Configuration Engine.
The Event Service is a highly capable publish-and-subscribe communication method. The Event Service
uses subject-based addressing to send messages to their destinations. Subject-based addressing
conventions define a simple, uniform namespace for messages and their destinations.
NameSpace Mapper
The Configuration Engine includes the NameSpace Mapper (NSM) that provides a lookup service for
managing logical groups of devices based on application, device or group ID, and event.
Cisco IOS devices recognize only event subject-names that match those configured in Cisco IOS
software; for example, cisco.cns.config.load. You can use the namespace mapping service to designate
events by using any desired naming convention. When you have populated your data store with your
subject names, NSM changes your event subject-name strings to those known by Cisco IOS.
For a subscriber, when given a unique device ID and event, the namespace mapping service returns a set
of events to which to subscribe. Similarly, for a publisher, when given a unique group ID, device ID, and
event, the mapping service returns a set of events on which to publish.
What You Should Know About the CNS IDs and Device Hostnames
The Configuration Engine assumes that a unique identifier is associated with each configured switch.
This unique identifier can take on multiple synonyms, where each synonym is unique within a particular
namespace. The event service uses namespace content for subject-based addressing of messages.
The Configuration Engine intersects two namespaces, one for the event bus and the other for the
configuration server. Within the scope of the configuration server namespace, the term ConfigID is the
unique identifier for a device. Within the scope of the event bus namespace, the term DeviceID is the
CNS unique identifier for a device.
Because the Configuration Engine uses both the event bus and the configuration server to provide
configurations to devices, you must define both ConfigID and Device ID for each configured switch.
Within the scope of a single instance of the configuration server, no two configured switches can share
the same value for ConfigID. Within the scope of a single instance of the event bus, no two configured
switches can share the same value for DeviceID.
ConfigID
Each configured switch has a unique ConfigID, which serves as the key into the Configuration Engine
directory for the corresponding set of switch CLI attributes. The ConfigID defined on the switch must
match the ConfigID for the corresponding switch definition on the Configuration Engine.
The ConfigID is fixed at startup time and cannot be changed until the device restarts, even if the switch
hostname is reconfigured.
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DeviceID
Each configured switch participating on the event bus has a unique DeviceID, which is analogous to the
switch source address so that the switch can be targeted as a specific destination on the bus. All switches
configured with the cns config partial global configuration command must access the event bus.
Therefore, the DeviceID, as originated on the switch, must match the DeviceID of the corresponding
switch definition in the Configuration Engine.
The origin of the DeviceID is defined by the Cisco IOS hostname of the switch. However, the DeviceID
variable and its usage reside within the event gateway adjacent to the switch.
The logical Cisco IOS termination point on the event bus is embedded in the event gateway, which in
turn functions as a proxy on behalf of the switch. The event gateway represents the switch and its
corresponding DeviceID to the event bus.
The switch declares its hostname to the event gateway immediately after the successful connection to
the event gateway. The event gateway couples the DeviceID value to the Cisco IOS hostname each time
this connection is established. The event gateway caches this DeviceID value for the duration of its
connection to the switch.
Hostname and DeviceID
The DeviceID is fixed at the time of the connection to the event gateway and does not change even when
the switch hostname is reconfigured.
When changing the switch hostname on the switch, the only way to refresh the DeviceID is to break the
connection between the switch and the event gateway. Enter the no cns event global configuration
command followed by the cns event global configuration command.
When the connection is re-established, the switch sends its modified hostname to the event gateway. The
event gateway redefines the DeviceID to the new value.
Caution
When using the Configuration Engine user interface, you must first set the DeviceID field to the
hostname value that the switch acquires after–not before–you use the cns config initial global
configuration command at the switch. Otherwise, subsequent cns config partial global configuration
command operations malfunction.
Using Hostname, DeviceID, and ConfigID
In standalone mode, when a hostname value is set for a switch, the configuration server uses the
hostname as the DeviceID when an event is sent on hostname. If the hostname has not been set, the event
is sent on the cn=<value> of the device.
In server mode, the hostname is not used. In this mode, the unique DeviceID attribute is always used for
sending an event on the bus. If this attribute is not set, you cannot update the switch.
These and other associated attributes (tag value pairs) are set when you run Setup on the Configuration
Engine.
Note
For more information about running the setup program on the Configuration Engine, see the
Configuration Engine setup and configuration guide at
http://www.cisco.com/en/US/products/sw/netmgtsw/ps4617/prod_installation_guides_list.html
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Understanding Cisco IOS Agents
Understanding Cisco IOS Agents
The CNS event agent feature allows the switch to publish and subscribe to events on the event bus and
works with the Cisco IOS agent. The Cisco IOS agent feature supports the switch by providing these
features:
•
Initial Configuration, page 4-5
•
Incremental (Partial) Configuration, page 4-6
•
Synchronized Configuration, page 4-6
Initial Configuration
When the switch first comes up, it attempts to get an IP address by broadcasting a DHCP request on the
network. Assuming there is no DHCP server on the subnet, the distribution switch acts as a DHCP relay
agent and forwards the request to the DHCP server. Upon receiving the request, the DHCP server assigns
an IP address to the new switch and includes the TFTP server IP address, the path to the bootstrap
configuration file, and the default gateway IP address in a unicast reply to the DHCP relay agent. The
DHCP relay agent forwards the reply to the switch.
The switch automatically configures the assigned IP address on interface VLAN 1 (the default) and
downloads the bootstrap configuration file from the TFTP server. Upon successful download of the
bootstrap configuration file, the switch loads the file in its running configuration.
The Cisco IOS agents initiate communication with the Configuration Engine by using the appropriate
ConfigID and EventID. The Configuration Engine maps the Config ID to a template and downloads the
full configuration file to the switch.
Figure 4-2 shows a sample network configuration for retrieving the initial bootstrap configuration file
by using DHCP-based autoconfiguration.
Figure 4-2
Initial Configuration Overview
TFTP
server
Configuration
Engine
WAN
V
DHCP
server
Access layer
switches
DHCP relay agent
default gateway
141328
Distribution layer
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Configuring Cisco IOS Agents
Incremental (Partial) Configuration
After the network is running, new services can be added by using the Cisco IOS agent. Incremental
(partial) configurations can be sent to the switch. The actual configuration can be sent as an event
payload by way of the event gateway (push operation) or as a signal event that triggers the switch to
initiate a pull operation.
The switch can check the syntax of the configuration before applying it. If the syntax is correct, the
switch applies the incremental configuration and publishes an event that signals success to the
configuration server. If the switch does not apply the incremental configuration, it publishes an event
showing an error status. When the switch has applied the incremental configuration, it can write it to
NVRAM or wait until signaled to do so.
Synchronized Configuration
When the switch receives a configuration, it can defer application of the configuration upon receipt of a
write-signal event. The write-signal event tells the switch not to save the updated configuration into its
NVRAM. The switch uses the updated configuration as its running configuration. This ensures that the
switch configuration is synchronized with other network activities before saving the configuration in
NVRAM for use at the next reboot.
Configuring Cisco IOS Agents
The Cisco IOS agents embedded in the switch Cisco IOS software allow the switch to be connected and
automatically configured as described in the “Enabling Automated CNS Configuration” section on
page 4-6. If you want to change the configuration or install a custom configuration, see these sections
for instructions:
•
Enabling the CNS Event Agent, page 4-8
•
Enabling the Cisco IOS CNS Agent, page 4-9
Enabling Automated CNS Configuration
To enable automated CNS configuration of the switch, you must first complete the prerequisites in
Table 4-1. When you complete them, power on the switch. At the setup prompt, do nothing: The switch
begins the initial configuration as described in the “Initial Configuration” section on page 4-5. When the
full configuration file is loaded on your switch, you need to do nothing else.
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Table 4-1
Prerequisites for Enabling Automatic Configuration
Device
Required Configuration
Access switch
Factory default (no configuration file)
Distribution switch
DHCP server
TFTP server
CNS Configuration Engine
Note
•
IP helper address
•
Enable DHCP relay agent
•
IP routing (if used as default gateway)
•
IP address assignment
•
TFTP server IP address
•
Path to bootstrap configuration file on the TFTP server
•
Default gateway IP address
•
A bootstrap configuration file that includes the CNS
configuration commands that enable the switch to
communicate with the Configuration Engine
•
The switch configured to use either the switch MAC address
or the serial number (instead of the default hostname) to
generate the ConfigID and EventID
•
The CNS event agent configured to push the configuration file
to the switch
One or more templates for each type of device, with the ConfigID
of the device mapped to the template.
For more information about running the setup program and creating templates on the Configuration
Engine, see the Cisco Configuration Engine Installation and Setup Guide, 1.5 for Linux at
http://www.cisco.com/en/US/docs/net_mgmt/configuration_engine/1.5/installation_linux/guide/setup_
1.html
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Configuring Cisco IOS Agents
Enabling the CNS Event Agent
Note
You must enable the CNS event agent on the switch before you enable the CNS configuration agent.
Beginning in privileged EXEC mode, follow these steps to enable the CNS event agent on the switch:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
cns event {hostname | ip-address} [port-number]
[backup] [failover-time seconds] [keepalive seconds
retry-count] [reconnect time] [source ip-address]
Enable the event agent, and enter the gateway parameters.
•
For {hostname | ip-address}, enter either the
hostname or the IP address of the event gateway.
•
(Optional) For port number, enter the port number for
the event gateway. The default port number is 11011.
•
(Optional) Enter backup to show that this is the
backup gateway. (If omitted, this is the primary
gateway.)
•
(Optional) For failover-time seconds, enter how long
the switch waits for the primary gateway route after
the route to the backup gateway is established.
•
(Optional) For keepalive seconds, enter how often the
switch sends keepalive messages. For retry-count,
enter the number of unanswered keepalive messages
that the switch sends before the connection is
terminated. The default for each is 0.
•
(Optional) For reconnect time, enter the maximum
time interval that the switch waits before trying to
reconnect to the event gateway.
•
(Optional) For source ip-address, enter the source IP
address of this device.
Note
Though visible in the command-line help string,
the encrypt and the clock-timeout time keywords
are not supported.
Step 3
end
Return to privileged EXEC mode.
Step 4
show cns event connections
Verify information about the event agent.
Step 5
show running-config
Verify your entries.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To disable the CNS event agent, use the no cns event {ip-address | hostname} global configuration
command.
This example shows how to enable the CNS event agent, set the IP address gateway to 10.180.1.27, set
120 seconds as the keepalive interval, and set 10 as the retry count.
Switch(config)# cns event 10.180.1.27 keepalive 120 10
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Enabling the Cisco IOS CNS Agent
After enabling the CNS event agent, start the Cisco IOS CNS agent on the switch. You can enable the
Cisco IOS agent with these commands:
•
The cns config initial global configuration command enables the Cisco IOS agent and initiates an
initial configuration on the switch.
•
The cns config partial global configuration command enables the Cisco IOS agent and initiates a
partial configuration on the switch. You can then use the Configuration Engine to remotely send
incremental configurations to the switch.
Enabling an Initial Configuration
Beginning in privileged EXEC mode, follow these steps to enable the CNS configuration agent and
initiate an initial configuration on the switch:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
cns template connect name
Enter CNS template connect configuration mode, and
specify the name of the CNS connect template.
Step 3
cli config-text
Enter a command line for the CNS connect template.
Repeat this step for each command line in the template.
Step 4
Repeat Steps 2 to 3 to configure another CNS connect
template.
Step 5
exit
Return to global configuration mode.
Step 6
cns connect name [retries number] [retry-interval
seconds] [sleep seconds] [timeout seconds]
Enter CNS connect configuration mode, specify the name
of the CNS connect profile, and define the profile
parameters. The switch uses the CNS connect profile to
connect to the Configuration Engine.
•
Enter the name of the CNS connect profile.
•
(Optional) For retries number, enter the number of
connection retries. The range is 1 to 30. The default
is 3.
•
(Optional) For retry-interval seconds, enter the
interval between successive connection attempts to the
Configuration Engine. The range is 1 to 40 seconds.
The default is 10 seconds.
•
(Optional) For sleep seconds, enter the amount of time
before which the first connection attempt occurs. The
range is 0 to 250 seconds. The default is 0.
•
(Optional) For timeout seconds, enter the amount of
time after which the connection attempts end. The
range is 10 to 2000 seconds. The default is 120.
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Configuring Cisco IOS Agents
Step 7
Command
Purpose
discover {controller controller-type | dlci
[subinterface subinterface-number] | interface
[interface-type] | line line-type}
Specify the interface parameters in the CNS connect
profile.
•
For controller controller-type, enter the controller
type.
•
For dlci, enter the active data-link connection
identifiers (DLCIs).
(Optional) For subinterface subinterface-number,
specify the point-to-point subinterface number that is
used to search for active DLCIs.
Step 8
template name [ ... name]
Step 9
•
For interface [interface-type], enter the type of
interface.
•
For line line-type, enter the line type.
Specify the list of CNS connect templates in the CNS
connect profile to be applied to the switch configuration.
You can specify more than one template.
Repeat Steps 7 to 8 to specify more interface parameters
and CNS connect templates in the CNS connect profile.
Step 10
exit
Return to global configuration mode.
Step 11
hostname name
Enter the hostname for the switch.
Step 12
ip route network-number
(Optional) Establish a static route to the Configuration
Engine whose IP address is network-number.
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Step 13
Command
Purpose
cns id interface num {dns-reverse | ipaddress |
mac-address} [event] [image]
(Optional) Set the unique EventID or ConfigID used by the
Configuration Engine.
or
•
For interface num, enter the type of interface–for
example, ethernet, group-async, loopback, or
virtual-template. This setting specifies from which
interface the IP or MAC address should be retrieved to
define the unique ID.
•
For {dns-reverse | ipaddress | mac-address}, enter
dns-reverse to retrieve the hostname and assign it as
the unique ID, enter ipaddress to use the IP address, or
enter mac-address to use the MAC address as the
unique ID.
•
(Optional) Enter event to set the ID to be the event-id
value used to identify the switch.
•
(Optional) Enter image to set the ID to be the image-id
value used to identify the switch.
cns id {hardware-serial | hostname | string string |
udi} [event] [image]
Note
•
If both the event and image keywords are omitted,
the image-id value is used to identify the switch.
For {hardware-serial | hostname| string string |
udi}, enter hardware-serial to set the switch serial
number as the unique ID, enter hostname (the default)
to select the switch hostname as the unique ID, enter
an arbitrary text string for string string as the unique
ID, or enter udi to set the unique device identifier
(UDI) as the unique ID.
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Step 14
Command
Purpose
cns config initial {hostname | ip-address}
[port-number] [event] [no-persist] [page page]
[source ip-address] [syntax-check]
Enable the Cisco IOS agent, and initiate an initial
configuration.
•
For {hostname | ip-address}, enter the hostname or the
IP address of the configuration server.
•
(Optional) For port-number, enter the port number of
the configuration server. The default port number is 80.
•
(Optional) Enable event for configuration success,
failure, or warning messages when the configuration is
finished.
•
(Optional) Enable no-persist to suppress the
automatic writing to NVRAM of the configuration
pulled as a result of entering the cns config initial
global configuration command. If the no-persist
keyword is not entered, using the cns config initial
command causes the resultant configuration to be
automatically written to NVRAM.
•
(Optional) For page page, enter the web page of the
initial configuration. The default is /Config/config/asp.
•
(Optional) Enter source ip-address to use for source IP
address.
•
(Optional) Enable syntax-check to check the syntax
when this parameter is entered.
Note
Though visible in the command-line help string,
the encrypt, status url, and inventory keywords
are not supported.
Step 15
end
Return to privileged EXEC mode.
Step 16
show cns config connections
Verify information about the configuration agent.
Step 17
show running-config
Verify your entries.
To disable the CNS Cisco IOS agent, use the no cns config initial {ip-address | hostname} global
configuration command.
This example shows how to configure an initial configuration on a remote switch when the switch
configuration is unknown (the CNS Zero Touch feature).
Switch(config)# cns template connect template-dhcp
Switch(config-tmpl-conn)# cli ip address dhcp
Switch(config-tmpl-conn)# exit
Switch(config)# cns template connect ip-route
Switch(config-tmpl-conn)# cli ip route 0.0.0.0 0.0.0.0 ${next-hop}
Switch(config-tmpl-conn)# exit
Switch(config)# cns connect dhcp
Switch(config-cns-conn)# discover interface gigabitethernet
Switch(config-cns-conn)# template template-dhcp
Switch(config-cns-conn)# template ip-route
Switch(config-cns-conn)# exit
Switch(config)# hostname RemoteSwitch
RemoteSwitch(config)# cns config initial 10.1.1.1 no-persist
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Configuring Cisco IOS Agents
This example shows how to configure an initial configuration on a remote switch when the switch IP
address is known. The Configuration Engine IP address is 172.28.129.22.
Switch(config)# cns template connect template-dhcp
Switch(config-tmpl-conn)# cli ip address dhcp
Switch(config-tmpl-conn)# exit
Switch(config)# cns template connect ip-route
Switch(config-tmpl-conn)# cli ip route 0.0.0.0 0.0.0.0 ${next-hop}
Switch(config-tmpl-conn)# exit
Switch(config)# cns connect dhcp
Switch(config-cns-conn)# discover interface gigabitethernet
Switch(config-cns-conn)# template template-dhcp
Switch(config-cns-conn)# template ip-route
Switch(config-cns-conn)# exit
Switch(config)# hostname RemoteSwitch
RemoteSwitch(config)# ip route 172.28.129.22 255.255.255.255 11.11.11.1
RemoteSwitch(config)# cns id ethernet 0 ipaddress
RemoteSwitch(config)# cns config initial 172.28.129.22 no-persist
Enabling a Partial Configuration
Beginning in privileged EXEC mode, follow these steps to enable the Cisco IOS agent and to initiate a
partial configuration on the switch:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
cns config partial {ip-address | hostname}
[port-number] [source ip-address]
Enable the configuration agent, and initiate a partial
configuration.
•
For {ip-address | hostname}, enter the IP address or
the hostname of the configuration server.
•
(Optional) For port-number, enter the port number of
the configuration server. The default port number is 80.
•
(Optional) Enter source ip-address to use for the
source IP address.
Note
Though visible in the command-line help string,
the encrypt keyword is not supported.
Step 3
end
Return to privileged EXEC mode.
Step 4
show cns config stats
or
show cns config outstanding
Verify information about the configuration agent.
Step 5
show running-config
Verify your entries.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To disable the Cisco IOS agent, use the no cns config partial {ip-address | hostname} global
configuration command. To cancel a partial configuration, use the cns config cancel privileged EXEC
command.
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Displaying CNS Configuration
Displaying CNS Configuration
You can use the privileged EXEC commands in Table 4-2 to display CNS configuration information.
Table 4-2
Displaying CNS Configuration
Command
Purpose
show cns config connections
Displays the status of the CNS Cisco IOS agent connections.
show cns config outstanding
Displays information about incremental (partial) CNS
configurations that have started but are not yet completed.
show cns config stats
Displays statistics about the Cisco IOS agent.
show cns event connections
Displays the status of the CNS event agent connections.
show cns event stats
Displays statistics about the CNS event agent.
show cns event subject
Displays a list of event agent subjects that are subscribed to by
applications.
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5
Administering the Switch
This chapter describes how to perform one-time operations to administer the switch.
This chapter consists of these sections:
•
Managing the System Time and Date, page 5-1
•
Configuring a System Name and Prompt, page 5-7
•
Creating a Banner, page 5-10
•
Managing the MAC Address Table, page 5-12
•
Managing the ARP Table, page 5-23
Managing the System Time and Date
You can manage the system time and date on your switch using automatic configuration, such as the
Network Time Protocol (NTP), or manual configuration methods.
Note
For complete syntax and usage information for the commands used in this section, see the Cisco IOS
Configuration Fundamentals Command Reference from the Cisco.com page under Documentation >
Cisco IOS Software > 12.2 Mainline > Command References.
These sections contain this configuration information:
•
Understanding the System Clock, page 5-1
•
Understanding Network Time Protocol, page 5-2
•
NTP Version 4, page 5-3
•
Configuring Time and Date Manually, page 5-4
Understanding the System Clock
The heart of the time service is the system clock. This clock runs from the moment the system starts up
and keeps track of the date and time.
The system clock can then be set from these sources:
•
NTP
•
Manual configuration
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Managing the System Time and Date
The system clock can provide time to these services:
•
User show commands
•
Logging and debugging messages
The system clock keeps track of time internally based on Universal Time Coordinated (UTC), also
known as Greenwich Mean Time (GMT). You can configure information about the local time zone and
summer time (daylight saving time) so that the time appears correctly for the local time zone.
The system clock keeps track of whether the time is authoritative or not (that is, whether it has been set
by a time source considered to be authoritative). If it is not authoritative, the time is available only for
display purposes and is not redistributed. For configuration information, see the “Configuring Time and
Date Manually” section on page 5-4.
Understanding Network Time Protocol
The NTP is designed to time-synchronize a network of devices. NTP runs over User Datagram Protocol
(UDP), which runs over IP. NTP is documented in RFC 1305.
An NTP network usually gets its time from an authoritative time source, such as a radio clock or an
atomic clock attached to a time server. NTP then distributes this time across the network. NTP is
extremely efficient; no more than one packet per minute is necessary to synchronize two devices to
within a millisecond of one another.
NTP uses the concept of a stratum to describe how many NTP hops away a device is from an
authoritative time source. A stratum 1 time server has a radio or atomic clock directly attached, a
stratum 2 time server receives its time through NTP from a stratum 1 time server, and so on. A device
running NTP automatically chooses as its time source the device with the lowest stratum number with
which it communicates through NTP. This strategy effectively builds a self-organizing tree of NTP
speakers.
NTP avoids synchronizing to a device whose time might not be accurate by never synchronizing to a
device that is not synchronized. NTP also compares the time reported by several devices and does not
synchronize to a device whose time is significantly different than the others, even if its stratum is lower.
The communications between devices running NTP (known as associations) are usually statically
configured; each device is given the IP address of all devices with which it should form associations.
Accurate timekeeping is possible by exchanging NTP messages between each pair of devices with an
association. However, in a LAN environment, NTP can be configured to use IP broadcast messages
instead. This alternative reduces configuration complexity because each device can simply be configured
to send or receive broadcast messages. However, in that case, information flow is one-way only.
The time kept on a device is a critical resource; you should use the security features of NTP to avoid the
accidental or malicious setting of an incorrect time. Two mechanisms are available: an access list-based
restriction scheme and an encrypted authentication mechanism.
Cisco’s implementation of NTP does not support stratum 1 service; it is not possible to connect to a radio
or atomic clock. We recommend that the time service for your network be derived from the public NTP
servers available on the IP Internet.
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Managing the System Time and Date
Figure 5-1 shows a typical network example using NTP. Switch A is the NTP master, with Switches B,
C, and D configured in NTP server mode, in server association with Switch A. Switch E is configured
as an NTP peer to the upstream and downstream switches, Switch B and Switch F.
Figure 5-1
Typical NTP Network Configuration
Switch A
Local
workgroup
servers
Switch B
Switch C
Switch D
Switch E
Workstations
101349
Switch F
Workstations
If the network is isolated from the Internet, Cisco’s implementation of NTP allows a device to act as if
it is synchronized through NTP, when in fact it has learned the time by using other means. Other devices
then synchronize to that device through NTP.
When multiple sources of time are available, NTP is always considered to be more authoritative. NTP
time overrides the time set by any other method.
Several manufacturers include NTP software for their host systems, and a publicly available version for
systems running UNIX and its various derivatives is also available. This software allows host systems to
be time-synchronized as well.
NTP Version 4
NTP version 4 is implemented on the switch. NTPv4 is an extension of NTP version 3. NTPv4 supports
both IPv4 and IPv6 and is backward-compatible with NTPv3.
NTPv4 provides these capabilities:
•
Support for IPv6.
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Managing the System Time and Date
•
Improved security compared to NTPv3. The NTPv4 protocol provides a security framework based
on public key cryptography and standard X509 certificates.
•
Automatic calculation of the time-distribution hierarchy for a network. Using specific multicast
groups, NTPv4 automatically configures the hierarchy of the servers to achieve the best time
accuracy for the lowest bandwidth cost. This feature leverages site-local IPv6 multicast addresses.
For details about configuring NTPv4, see the Cisco IOS IPv6 Configuration Guide, Release 12.4T.
Configuring Time and Date Manually
If no other source of time is available, you can manually configure the time and date after the system is
restarted. The time remains accurate until the next system restart. We recommend that you use manual
configuration only as a last resort. If you have an outside source to which the switch can synchronize,
you do not need to manually set the system clock.
These sections contain this configuration information:
•
Setting the System Clock, page 5-4
•
Displaying the Time and Date Configuration, page 5-5
•
Configuring the Time Zone, page 5-5
•
Configuring Summer Time (Daylight Saving Time), page 5-6
Setting the System Clock
If you have an outside source on the network that provides time services, such as an NTP server, you do
not need to manually set the system clock.
Beginning in privileged EXEC mode, follow these steps to set the system clock:
Step 1
Command
Purpose
clock set hh:mm:ss day month year
Manually set the system clock using one of these formats.
or
•
For hh:mm:ss, specify the time in hours (24-hour format), minutes,
and seconds. The time specified is relative to the configured time
zone.
•
For day, specify the day by date in the month.
•
For month, specify the month by name.
•
For year, specify the year (no abbreviation).
clock set hh:mm:ss month day year
This example shows how to manually set the system clock to 1:32 p.m. on July 23, 2001:
Switch# clock set 13:32:00 23 July 2001
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Managing the System Time and Date
Displaying the Time and Date Configuration
To display the time and date configuration, use the show clock [detail] privileged EXEC command.
The system clock keeps an authoritative flag that shows whether the time is authoritative (believed to be
accurate). If the system clock has been set by a timing source such as NTP, the flag is set. If the time is
not authoritative, it is used only for display purposes. Until the clock is authoritative and the
authoritative flag is set, the flag prevents peers from synchronizing to the clock when the peers’ time is
invalid.
The symbol that precedes the show clock display has this meaning:
•
*—Time is not authoritative.
•
(blank)—Time is authoritative.
•
.—Time is authoritative, but NTP is not synchronized.
Configuring the Time Zone
Beginning in privileged EXEC mode, follow these steps to manually configure the time zone:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
clock timezone zone hours-offset
[minutes-offset]
Set the time zone.
The switch keeps internal time in universal time coordinated (UTC), so
this command is used only for display purposes and when the time is
manually set.
•
For zone, enter the name of the time zone to be displayed when
standard time is in effect. The default is UTC.
•
For hours-offset, enter the hours offset from UTC.
•
(Optional) For minutes-offset, enter the minutes offset from UTC.
Step 3
end
Return to privileged EXEC mode.
Step 4
show running-config
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
The minutes-offset variable in the clock timezone global configuration command is available for those
cases where a local time zone is a percentage of an hour different from UTC. For example, the time zone
for some sections of Atlantic Canada (AST) is UTC-3.5, where the 3 means 3 hours and .5 means 50
percent. In this case, the necessary command is clock timezone AST -3 30.
To set the time to UTC, use the no clock timezone global configuration command.
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Managing the System Time and Date
Configuring Summer Time (Daylight Saving Time)
Beginning in privileged EXEC mode, follow these steps to configure summer time (daylight saving time)
in areas where it starts and ends on a particular day of the week each year:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
clock summer-time zone recurring
Configure summer time to start and end on the specified days every year.
[week day month hh:mm week day month
Summer time is disabled by default. If you specify clock summer-time
hh:mm [offset]]
zone recurring without parameters, the summer time rules default to the
United States rules.
•
For zone, specify the name of the time zone (for example, PDT) to be
displayed when summer time is in effect.
•
(Optional) For week, specify the week of the month (1 to 5 or last).
•
(Optional) For day, specify the day of the week (Sunday, Monday...).
•
(Optional) For month, specify the month (January, February...).
•
(Optional) For hh:mm, specify the time (24-hour format) in hours and
minutes.
•
(Optional) For offset, specify the number of minutes to add during
summer time. The default is 60.
Step 3
end
Return to privileged EXEC mode.
Step 4
show running-config
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
The first part of the clock summer-time global configuration command specifies when summer time
begins, and the second part specifies when it ends. All times are relative to the local time zone. The start
time is relative to standard time. The end time is relative to summer time. If the starting month is after
the ending month, the system assumes that you are in the southern hemisphere.
This example shows how to specify that summer time starts on the first Sunday in April at 02:00 and
ends on the last Sunday in October at 02:00:
Switch(config)# clock summer-time PDT recurring 1 Sunday April 2:00 last Sunday October
2:00
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Configuring a System Name and Prompt
Beginning in privileged EXEC mode, follow these steps if summer time in your area does not follow a
recurring pattern (configure the exact date and time of the next summer time events):
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
Configure summer time to start on the first date and end on the second
clock summer-time zone date [month
date year hh:mm month date year hh:mm date.
[offset]]
Summer time is disabled by default.
or
• For zone, specify the name of the time zone (for example, PDT) to be
clock summer-time zone date [date
displayed when summer time is in effect.
month year hh:mm date month year
• (Optional) For week, specify the week of the month (1 to 5 or last).
hh:mm [offset]]
• (Optional) For day, specify the day of the week (Sunday, Monday...).
•
(Optional) For month, specify the month (January, February...).
•
(Optional) For hh:mm, specify the time (24-hour format) in hours and
minutes.
•
(Optional) For offset, specify the number of minutes to add during
summer time. The default is 60.
Step 3
end
Return to privileged EXEC mode.
Step 4
show running-config
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
The first part of the clock summer-time global configuration command specifies when summer time
begins, and the second part specifies when it ends. All times are relative to the local time zone. The start
time is relative to standard time. The end time is relative to summer time. If the starting month is after
the ending month, the system assumes that you are in the southern hemisphere.
To disable summer time, use the no clock summer-time global configuration command.
This example shows how to set summer time to start on October 12, 2000, at 02:00, and end on April 26,
2001, at 02:00:
Switch(config)# clock summer-time pdt date 12 October 2000 2:00 26 April 2001 2:00
Configuring a System Name and Prompt
You configure the system name on the switch to identify it. By default, the system name and prompt are
Switch.
If you have not configured a system prompt, the first 20 characters of the system name are used as the
system prompt. A greater-than symbol [>] is appended. The prompt is updated whenever the system
name changes.
For complete syntax and usage information for the commands used in this section, from the Cisco.com
page, select Documentation > Cisco IOS Software > 12.2 Mainline > Command References and see
the Cisco IOS Configuration Fundamentals Command Reference and the Cisco IOS IP Command
Reference, Volume 2 of 3: Routing Protocols.
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Configuring a System Name and Prompt
These sections contain this configuration information:
•
Default System Name and Prompt Configuration, page 5-8
•
Configuring a System Name, page 5-8
•
Understanding DNS, page 5-8
Default System Name and Prompt Configuration
The default switch system name and prompt is Switch.
Configuring a System Name
Beginning in privileged EXEC mode, follow these steps to manually configure a system name:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
hostname name
Manually configure a system name.
The default setting is switch.
The name must follow the rules for ARPANET hostnames. They must start
with a letter, end with a letter or digit, and have as interior characters only
letters, digits, and hyphens. Names can be up to 63 characters.
Step 3
end
Return to privileged EXEC mode.
Step 4
show running-config
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
When you set the system name, it is also used as the system prompt.
To return to the default hostname, use the no hostname global configuration command.
Understanding DNS
The DNS protocol controls the Domain Name System (DNS), a distributed database with which you can
map hostnames to IP addresses. When you configure DNS on your switch, you can substitute the
hostname for the IP address with all IP commands, such as ping, telnet, connect, and related Telnet
support operations.
IP defines a hierarchical naming scheme that allows a device to be identified by its location or domain.
Domain names are pieced together with periods (.) as the delimiting characters. For example, Cisco
Systems is a commercial organization that IP identifies by a com domain name, so its domain name is
cisco.com. A specific device in this domain, for example, the File Transfer Protocol (FTP) system is
identified as ftp.cisco.com.
To keep track of domain names, IP has defined the concept of a domain name server, which holds a cache
(or database) of names mapped to IP addresses. To map domain names to IP addresses, you must first
identify the hostnames, specify the name server that is present on your network, and enable the DNS.
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These sections contain this configuration information:
•
Default DNS Configuration, page 5-9
•
Setting Up DNS, page 5-9
•
Displaying the DNS Configuration, page 5-10
Default DNS Configuration
Table 5-1 shows the default DNS configuration.
Table 5-1
Default DNS Configuration
Feature
Default Setting
DNS enable state
Enabled.
DNS default domain name
None configured.
DNS servers
No name server addresses are configured.
Setting Up DNS
Beginning in privileged EXEC mode, follow these steps to set up your switch to use the DNS:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
ip domain-name name
Define a default domain name that the software uses to complete unqualified
hostnames (names without a dotted-decimal domain name).
Do not include the initial period that separates an unqualified name from the
domain name.
At bootup time, no domain name is configured; however, if the switch
configuration comes from a BOOTP or Dynamic Host Configuration Protocol
(DHCP) server, then the default domain name might be set by the BOOTP or
DHCP server (if the servers were configured with this information).
Step 3
Step 4
ip name-server server-address1
[server-address2 ...
server-address6]
Specify the address of one or more name servers to use for name and address
resolution.
ip domain-lookup
(Optional) Enable DNS-based hostname-to-address translation on your switch.
This feature is enabled by default.
You can specify up to six name servers. Separate each server address with a
space. The first server specified is the primary server. The switch sends DNS
queries to the primary server first. If that query fails, the backup servers are
queried.
If your network devices require connectivity with devices in networks for which
you do not control name assignment, you can dynamically assign device names
that uniquely identify your devices by using the global Internet naming scheme
(DNS).
Step 5
end
Return to privileged EXEC mode.
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Creating a Banner
Command
Purpose
Step 6
show running-config
Verify your entries.
Step 7
copy running-config
startup-config
(Optional) Save your entries in the configuration file.
If you use the switch IP address as its hostname, the IP address is used and no DNS query occurs. If you
configure a hostname that contains no periods (.), a period followed by the default domain name is
appended to the hostname before the DNS query is made to map the name to an IP address. The default
domain name is the value set by the ip domain-name global configuration command. If there is a
period (.) in the hostname, the Cisco IOS software looks up the IP address without appending any default
domain name to the hostname.
To remove a domain name, use the no ip domain-name name global configuration command. To remove
a name server address, use the no ip name-server server-address global configuration command. To
disable DNS on the switch, use the no ip domain-lookup global configuration command.
Displaying the DNS Configuration
To display the DNS configuration information, use the show running-config privileged EXEC
command.
Creating a Banner
You can configure a message-of-the-day (MOTD) and a login banner. The MOTD banner displays on all
connected terminals at login and is useful for sending messages that affect all network users (such as
impending system shutdowns).
The login banner also displays on all connected terminals. It appears after the MOTD banner and before
the login prompts.
Note
For complete syntax and usage information for the commands used in this section, see the Cisco IOS
Configuration Fundamentals Command Reference, Release 12.2 from the Cisco.com page under
Documentation > Cisco IOS Software > 12.2 Mainline > Command References.
These sections contain this configuration information:
•
Default Banner Configuration, page 5-10
•
Configuring a Message-of-the-Day Login Banner, page 5-11
•
Configuring a Login Banner, page 5-12
Default Banner Configuration
The MOTD and login banners are not configured.
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Creating a Banner
Configuring a Message-of-the-Day Login Banner
You can create a single or multiline message banner that appears on the screen when someone logs in to
the switch.
Beginning in privileged EXEC mode, follow these steps to configure a MOTD login banner:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
banner motd c message c
Specify the message of the day.
For c, enter the delimiting character of your choice, for example, a
pound sign (#), and press the Return key. The delimiting character
signifies the beginning and end of the banner text. Characters after the
ending delimiter are discarded.
For message, enter a banner message up to 255 characters. You cannot
use the delimiting character in the message.
Step 3
end
Return to privileged EXEC mode.
Step 4
show running-config
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To delete the MOTD banner, use the no banner motd global configuration command.
This example shows how to configure a MOTD banner for the switch by using the pound sign (#) symbol
as the beginning and ending delimiter:
Switch(config)# banner motd #
This is a secure site. Only authorized users are allowed.
For access, contact technical support.
#
Switch(config)#
This example shows the banner that appears from the previous configuration:
Unix> telnet 172.2.5.4
Trying 172.2.5.4...
Connected to 172.2.5.4.
Escape character is '^]'.
This is a secure site. Only authorized users are allowed.
For access, contact technical support.
User Access Verification
Password:
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Managing the MAC Address Table
Configuring a Login Banner
You can configure a login banner to be displayed on all connected terminals. This banner appears after
the MOTD banner and before the login prompt.
Beginning in privileged EXEC mode, follow these steps to configure a login banner:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
banner login c message c
Specify the login message.
For c, enter the delimiting character of your choice, for example, a pound
sign (#), and press the Return key. The delimiting character signifies the
beginning and end of the banner text. Characters after the ending delimiter
are discarded.
For message, enter a login message up to 255 characters. You cannot use the
delimiting character in the message.
Step 3
end
Return to privileged EXEC mode.
Step 4
show running-config
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To delete the login banner, use the no banner login global configuration command.
This example shows how to configure a login banner for the switch by using the dollar sign ($) symbol
as the beginning and ending delimiter:
Switch(config)# banner login $
Access for authorized users only. Please enter your username and password.
$
Switch(config)#
Managing the MAC Address Table
The MAC address table contains address information that the switch uses to forward traffic between
ports. All MAC addresses in the address table are associated with one or more ports. The address table
includes these types of addresses:
•
Dynamic address: a source MAC address that the switch learns and then ages when it is not in use.
•
Static address: a manually entered unicast address that does not age and that is not lost when the
switch resets.
The address table lists the destination MAC address, the associated VLAN ID, and port number
associated with the address and the type (static or dynamic).
Note
For complete syntax and usage information for the commands used in this section, see the command
reference for this release.
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Managing the MAC Address Table
These sections contain this configuration information:
•
Building the Address Table, page 5-13
•
MAC Addresses and VLANs, page 5-13
•
Default MAC Address Table Configuration, page 5-14
•
Changing the Address Aging Time, page 5-14
•
Removing Dynamic Address Entries, page 5-15
•
Configuring MAC Address Change Notification Traps, page 5-15
•
Configuring MAC Address Move Notification Traps, page 5-17
•
Configuring MAC Threshold Notification Traps, page 5-18
•
Adding and Removing Static Address Entries, page 5-19
•
Configuring Unicast MAC Address Filtering, page 5-20
•
Disabling MAC Address Learning on a VLAN, page 5-21
•
Displaying Address Table Entries, page 5-23
Building the Address Table
With multiple MAC addresses supported on all ports, you can connect any port on the switch to
individual workstations, repeaters, switches, routers, or other network devices. The switch provides
dynamic addressing by learning the source address of packets it receives on each port and adding the
address and its associated port number to the address table. As stations are added or removed from the
network, the switch updates the address table, adding new dynamic addresses and aging out those that
are not in use.
The aging interval is globally configured. However, the switch maintains an address table for each
VLAN, and STP can accelerate the aging interval on a per-VLAN basis.
The switch sends packets between any combination of ports, based on the destination address of the
received packet. Using the MAC address table, the switch forwards the packet only to the port associated
with the destination address. If the destination address is on the port that sent the packet, the packet is
filtered and not forwarded. The switch always uses the store-and-forward method: complete packets are
stored and checked for errors before transmission.
MAC Addresses and VLANs
All addresses are associated with a VLAN. An address can exist in more than one VLAN and have
different destinations in each. Unicast addresses, for example, could be forwarded to port 1 in VLAN 1
and ports 9, 10, and 1 in VLAN 5.
Each VLAN maintains its own logical address table. A known address in one VLAN is unknown in
another until it is learned or statically associated with a port in the other VLAN.
When private VLANs are configured, address learning depends on the type of MAC address:
•
Dynamic MAC addresses learned in one VLAN of a private VLAN are replicated in the associated
VLANs. For example, a MAC address learned in a private-VLAN secondary VLAN is replicated in
the primary VLAN.
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•
Static MAC addresses configured in a primary or secondary VLAN are not replicated in the
associated VLANs. When you configure a static MAC address in a private VLAN primary or
secondary VLAN, you should also configure the same static MAC address in all associated VLANs.
For more information about private VLANs, see Chapter 15, “Configuring Private VLANs.”
Default MAC Address Table Configuration
Table 5-2 shows the default MAC address table configuration.
Table 5-2
Default MAC Address Table Configuration
Feature
Default Setting
Aging time
300 seconds
Dynamic addresses
Automatically learned
Static addresses
None configured
Changing the Address Aging Time
Dynamic addresses are source MAC addresses that the switch learns and then ages when they are not in
use. You can change the aging time setting for all VLANs or for a specified VLAN.
Setting too short an aging time can cause addresses to be prematurely removed from the table. Then
when the switch receives a packet for an unknown destination, it floods the packet to all ports in the same
VLAN as the receiving port. This unnecessary flooding can impact performance. Setting too long an
aging time can cause the address table to be filled with unused addresses, which prevents new addresses
from being learned. Flooding results, which can impact switch performance.
Beginning in privileged EXEC mode, follow these steps to configure the dynamic address table aging
time:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
mac address-table aging-time [0 |
10-1000000] [vlan vlan-id]
Set the length of time that a dynamic entry remains in the MAC
address table after the entry is used or updated.
The range is 10 to 1000000 seconds. The default is 300. You can also
enter 0, which disables aging. Static address entries are never aged
or removed from the table.
For vlan-id, valid IDs are 1 to 4094.
Step 3
end
Return to privileged EXEC mode.
Step 4
show mac address-table aging-time
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To return to the default value, use the no mac address-table aging-time global configuration command.
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Managing the MAC Address Table
Removing Dynamic Address Entries
To remove all dynamic entries, use the clear mac address-table dynamic command in privileged EXEC
mode. You can also remove a specific MAC address (clear mac address-table dynamic address
mac-address), remove all addresses on the specified physical port or port channel (clear mac
address-table dynamic interface interface-id), or remove all addresses on a specified VLAN (clear
mac address-table dynamic vlan vlan-id).
To verify that dynamic entries have been removed, use the show mac address-table dynamic privileged
EXEC command.
Configuring MAC Address Change Notification Traps
MAC address change notification tracks users on a network by storing the MAC address change activity.
When the switch learns or removes a MAC address, an SNMP notification trap can be sent to the NMS.
If you have many users coming and going from the network, you can set a trap-interval time to bundle
the notification traps to reduce network traffic. The MAC notification history table stores MAC address
activity for each port for which the trap is set. MAC address change notifications are generated for
dynamic and secure MAC addresses. Notifications are not generated for self addresses, multicast
addresses, or other static addresses.
Beginning in privileged EXEC mode, follow these steps to configure the switch to send MAC address
change notification traps to an NMS host:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
snmp-server host host-addr {traps | informs} {version {1 Specify the recipient of the trap message.
| 2c | 3}} community-string notification-type
• For host-addr, specify the name or address of the
NMS.
•
Specify traps (the default) to send SNMP traps
to the host. Specify informs to send SNMP
informs to the host.
•
Specify the SNMP version to support. Version 1,
the default, is not available with informs.
•
For community-string, specify the string to send
with the notification operation. Though you can
set this string by using the snmp-server host
command, we recommend that you define this
string by using the snmp-server community
command before using the snmp-server host
command.
•
For notification-type, use the mac-notification
keyword.
Step 3
snmp-server enable traps mac-notification change
Enable the switch to send MAC address change
notification traps to the NMS.
Step 4
mac address-table notification change
Enable the MAC address change notification feature.
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Step 5
Command
Purpose
mac address-table notification change [interval value]
[history-size value]
Enter the trap interval time and the history table size.
•
(Optional) For interval value, specify the
notification trap interval in seconds between
each set of traps that are generated to the NMS.
The range is 0 to 2147483647 seconds; the
default is 1 second.
•
(Optional) For history-size value, specify the
maximum number of entries in the MAC
notification history table. The range is 0 to 500;
the default is 1.
Step 6
interface interface-id
Enter interface configuration mode, and specify the
Layer 2 interface on which to enable the SNMP
MAC address notification trap.
Step 7
snmp trap mac-notification change {added | removed}
Enable the MAC address change notification trap on
the interface.
•
Enable the trap when a MAC address is added
on this interface.
•
Enable the trap when a MAC address is removed
from this interface.
Step 8
end
Return to privileged EXEC mode.
Step 9
show mac address-table notification change interface
Verify your entries.
show running-config
Step 10
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To disable MAC address-change notification traps, use the no snmp-server enable traps
mac-notification change global configuration command. To disable the MAC address-change
notification traps on a specific interface, use the no snmp trap mac-notification change {added |
removed} interface configuration command. To disable the MAC address-change notification feature,
use the no mac address-table notification change global configuration command.
This example shows how to specify 172.20.10.10 as the NMS, enable the switch to send MAC address
notification traps to the NMS, enable the MAC address-change notification feature, set the interval time
to 123 seconds, set the history-size to 100 entries, and enable traps whenever a MAC address is added
on the specified port.
Switch(config)# snmp-server host 172.20.10.10 traps private mac-notification
Switch(config)# snmp-server enable traps mac-notification change
Switch(config)# mac address-table notification change
Switch(config)# mac address-table notification change interval 123
Switch(config)# mac address-table notification change history-size 100
Switch(config)# interface gigabitethernet0/2
Switch(config-if)# snmp trap mac-notification change added
You can verify your settings by entering the show mac address-table notification change interface and
the show mac address-table notification change privileged EXEC commands.
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Managing the MAC Address Table
Configuring MAC Address Move Notification Traps
When you configure MAC-move notification, an SNMP notification is generated and sent to the network
management system whenever a MAC address moves from one port to another within the same VLAN.
Beginning in privileged EXEC mode, follow these steps to configure the switch to send MAC
address-move notification traps to an NMS host:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
snmp-server host host-addr {traps | informs} {version {1 Specify the recipient of the trap message.
| 2c | 3}} community-string notification-type
• For host-addr, specify the name or address of the
NMS.
•
Specify traps (the default) to send SNMP traps
to the host. Specify informs to send SNMP
informs to the host.
•
Specify the SNMP version to support. Version 1,
the default, is not available with informs.
•
For community-string, specify the string to send
with the notification operation. Though you can
set this string by using the snmp-server host
command, we recommend that you define this
string by using the snmp-server community
command before using the snmp-server host
command.
•
For notification-type, use the mac-notification
keyword.
Step 3
snmp-server enable traps mac-notification move
Enable the switch to send MAC address move
notification traps to the NMS.
Step 4
mac address-table notification mac-move
Enable the MAC address move notification feature.
Step 5
end
Return to privileged EXEC mode.
Step 6
show mac address-table notification mac-move
Verify your entries.
show running-config
Step 7
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To disable MAC address-move notification traps, use the no snmp-server enable traps
mac-notification move global configuration command. To disable the MAC address-move notification
feature, use the no mac address-table notification mac-move global configuration command.
This example shows how to specify 172.20.10.10 as the NMS, enable the switch to send MAC address
move notification traps to the NMS, enable the MAC address move notification feature, and enable traps
when a MAC address moves from one port to another.
Switch(config)# snmp-server host 172.20.10.10 traps private mac-notification
Switch(config)# snmp-server enable traps mac-notification move
Switch(config)# mac address-table notification mac-move
You can verify your settings by entering the show mac address-table notification mac-move privileged
EXEC commands.
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Managing the MAC Address Table
Configuring MAC Threshold Notification Traps
When you configure MAC threshold notification, an SNMP notification is generated and sent to the
network management system when a MAC address table threshold limit is reached or exceeded.
Beginning in privileged EXEC mode, follow these steps to configure the switch to send MAC address
table threshold notification traps to an NMS host:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
snmp-server host host-addr {traps | informs} {version {1 Specify the recipient of the trap message.
| 2c | 3}} community-string notification-type
• For host-addr, specify the name or address of the
NMS.
•
Specify traps (the default) to send SNMP traps
to the host. Specify informs to send SNMP
informs to the host.
•
Specify the SNMP version to support. Version 1,
the default, is not available with informs.
•
For community-string, specify the string to send
with the notification operation. Though you can
set this string by using the snmp-server host
command, we recommend that you define this
string by using the snmp-server community
command before using the snmp-server host
command.
•
For notification-type, use the mac-notification
keyword.
Step 3
snmp-server enable traps mac-notification threshold
Enable the switch to send MAC threshold
notification traps to the NMS.
Step 4
mac address-table notification threshold
Enable the MAC address threshold notification
feature.
Step 5
mac address-table notification threshold [limit
percentage] | [interval time]
Enter the threshold value for the MAC address
threshold usage monitoring.
•
(Optional) For limit percentage, specify the
percentage of the MAC address table use; valid
values are from 1 to 100 percent. The default is
50 percent.
•
(Optional) For interval time, specify the time
between notifications; valid values are greater
than or equal to 120 seconds. The default is 120
seconds.
Step 6
end
Return to privileged EXEC mode.
Step 7
show mac address-table notification threshold
show running-config
Verify your entries.
Step 8
copy running-config startup-config
(Optional) Save your entries in the configuration file.
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To disable MAC address-threshold notification traps, use the no snmp-server enable traps
mac-notification threshold global configuration command. To disable the MAC address-threshold
notification feature, use the no mac address-table notification threshold global configuration
command.
This example shows how to specify 172.20.10.10 as the NMS, enable the MAC address threshold
notification feature, set the interval time to 123 seconds, and set the limit to 78 per cent.
Switch(config)#
Switch(config)#
Switch(config)#
Switch(config)#
Switch(config)#
snmp-server host 172.20.10.10 traps private mac-notification
snmp-server enable traps mac-notification threshold
mac address-table notification threshold
mac address-table notification threshold interval 123
mac address-table notification threshold limit 78
You can verify your settings by entering the show mac address-table notification threshold privileged
EXEC commands.
Adding and Removing Static Address Entries
A static address has these characteristics:
•
It is manually entered in the address table and must be manually removed.
•
It can be a unicast or multicast address.
•
It does not age and is retained when the switch restarts.
You can add and remove static addresses and define the forwarding behavior for them. The forwarding
behavior defines how a port that receives a packet forwards it to another port for transmission. Because
all ports are associated with at least one VLAN, the switch acquires the VLAN ID for the address from
the ports that you specify. You can specify a different list of destination ports for each source port.
A packet with a static address that arrives on a VLAN where it has not been statically entered is flooded
to all ports and not learned.
You add a static address to the address table by specifying the destination MAC unicast address and the
VLAN from which it is received. Packets received with this destination address are forwarded to the
interface specified with the interface-id option.
When you configure a static MAC address in a private-VLAN primary or secondary VLAN, you should
also configure the same static MAC address in all associated VLANs. Static MAC addresses configured
in a private-VLAN primary or secondary VLAN are not replicated in the associated VLAN. For more
information about private VLANs, see Chapter 15, “Configuring Private VLANs.”
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Managing the MAC Address Table
Beginning in privileged EXEC mode, follow these steps to add a static address:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
mac address-table static mac-addr
vlan vlan-id interface interface-id
Add a static address to the MAC address table.
•
For mac-addr, specify the destination MAC unicast address to add to
the address table. Packets with this destination address received in the
specified VLAN are forwarded to the specified interface.
•
For vlan-id, specify the VLAN for which the packet with the
specified MAC address is received. Valid VLAN IDs are 1 to 4094.
•
For interface-id, specify the interface to which the received packet is
forwarded. Valid interfaces include physical ports or port channels.
For static multicast addresses, you can enter multiple interface IDs.
For static unicast addresses, you can enter only one interface at a
time, but you can enter the command multiple times with the same
MAC address and VLAN ID.
Step 3
end
Return to privileged EXEC mode.
Step 4
show mac address-table static
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To remove static entries from the address table, use the no mac address-table static mac-addr vlan
vlan-id [interface interface-id] global configuration command.
This example shows how to add the static address c2f3.220a.12f4 to the MAC address table. When a
packet is received in VLAN 4 with this MAC address as its destination address, the packet is forwarded
to the specified port:
Switch(config)# mac address-table static c2f3.220a.12f4 vlan 4 interface
gigabitethernet0/1
Configuring Unicast MAC Address Filtering
When unicast MAC address filtering is enabled, the switch drops packets with specific source or
destination MAC addresses. This feature is disabled by default and only supports unicast static
addresses.
Follow these guidelines when using this feature:
•
Multicast MAC addresses, broadcast MAC addresses, and router MAC addresses are not supported.
If you specify one of these addresses when entering the mac address-table static mac-addr vlan
vlan-id drop global configuration command, one of these messages appears:
% Only unicast addresses can be configured to be dropped
% CPU destined address cannot be configured as drop address
•
Packets that are forwarded to the CPU are also not supported.
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•
If you add a unicast MAC address as a static address and configure unicast MAC address filtering,
the switch either adds the MAC address as a static address or drops packets with that MAC address,
depending on which command was entered last. The second command that you entered overrides the
first command.
For example, if you enter the mac address-table static mac-addr vlan vlan-id interface
interface-id global configuration command followed by the mac address-table static mac-addr
vlan vlan-id drop command, the switch drops packets with the specified MAC address as a source
or destination.
If you enter the mac address-table static mac-addr vlan vlan-id drop global configuration
command followed by the mac address-table static mac-addr vlan vlan-id interface interface-id
command, the switch adds the MAC address as a static address.
You enable unicast MAC address filtering and configure the switch to drop packets with a specific
address by specifying the source or destination unicast MAC address and the VLAN from which it is
received.
Beginning in privileged EXEC mode, follow these steps to configure the switch to drop a source or
destination unicast static address:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
mac address-table static mac-addr
vlan vlan-id drop
Enable unicast MAC address filtering and configure the switch to drop a
packet with the specified source or destination unicast static address.
•
For mac-addr, specify a source or destination unicast MAC address.
Packets with this MAC address are dropped.
•
For vlan-id, specify the VLAN for which the packet with the
specified MAC address is received. Valid VLAN IDs are 1 to 4094.
Step 3
end
Return to privileged EXEC mode.
Step 4
show mac address-table static
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To disable unicast MAC address filtering, use the no mac address-table static mac-addr vlan vlan-id
global configuration command.
This example shows how to enable unicast MAC address filtering and to configure the switch to drop
packets that have a source or destination address of c2f3.220a.12f4. When a packet is received in
VLAN 4 with this MAC address as its source or destination, the packet is dropped:
Switch(config)# mac a ddress-table static c2f3.220a.12f4 vlan 4 drop
Disabling MAC Address Learning on a VLAN
By default, MAC address learning is enabled on all VLANs on the switch. You can control MAC address
learning on a VLAN to manage the available MAC address table space by controlling which VLANs,
and therefore which ports, can learn MAC addresses. Before you disable MAC address learning, be sure
that you are familiar with the network topology and the switch system configuration. Disabling MAC
address learning on a VLAN could cause flooding in the network.
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Follow these guidelines when disabling MAC address learning on a VLAN:
•
Use caution before disabling MAC address learning on a VLAN with a configured switch virtual
interface (SVI). The switch then floods all IP packets in the Layer 2 domain.
•
You can disable MAC address learning on a single VLAN (for example, no mac address-table
learning vlan 223) or on a range of VLANs (for example, no mac address-table learning vlan
1-10, 15).
•
We recommend that you disable MAC address learning only in VLANs with two ports. If you
disable MAC address learning on a VLAN with more than two ports, every packet entering the
switch is flooded in that VLAN domain.
•
You cannot disable MAC address learning on a VLAN that is used internally by the switch. If the
VLAN ID that you enter is an internal VLAN, the switch generates an error message and rejects the
command. To view internal VLANs in use, enter the show vlan internal usage privileged EXEC
command.
•
If you disable MAC address learning on a VLAN configured as a private-VLAN primary VLAN,
MAC addresses are still learned on the secondary VLAN that belongs to the private VLAN and are
then replicated on the primary VLAN. If you disable MAC address learning on the secondary
VLAN, but not the primary VLAN of a private VLAN, MAC address learning occurs on the primary
VLAN and is replicated on the secondary VLAN.
•
You cannot disable MAC address learning on an RSPAN VLAN. The configuration is not allowed.
•
If you disable MAC address learning on a VLAN that includes a secure port, MAC address learning
is not disabled on that port. If you disable port security, the configured MAC address learning state
is enabled.
Beginning in privileged EXEC mode, follow these steps to disable MAC address learning on a VLAN:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
no mac address-table learning vlan
vlan-id
Disable MAC address learning on the specified VLAN or VLANs. You
can specify a single VLAN, or a range of VLANs separated by a hyphen
or comma.Valid VLAN IDs are 1 to 4094. It cannot be an internal VLAN.
Step 3
end
Return to privileged EXEC mode.
Step 4
show mac address-table learning [vlan Verify the configuration.
vlan-id]
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To reenable MAC address learning on a VLAN, use the default mac address-table learning vlan
vlan-id global configuration command. You can also reenable MAC address learning on a VLAN by
entering the mac address-table learning vlan vlan-id global configuration command. The first
(default) command returns to a default condition and therefore does not appear in the output from the
show running-config command. The second command causes the configuration to appear in the show
running-config privileged EXEC command display.
This example shows how to disable MAC address learning on VLAN 200:
Switch(config)# no mac a ddress-table learning vlan 200
You can display the MAC address learning status of all VLANs or a specified VLAN by entering the
show mac-address-table learning [vlan vlan-id] privileged EXEC command.
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Administering the Switch
Managing the ARP Table
Displaying Address Table Entries
You can display the MAC address table by using one or more of the privileged EXEC commands
described in Table 5-3:
Table 5-3
Commands for Displaying the MAC Address Table
Command
Description
show ip igmp snooping groups
Displays the Layer 2 multicast entries for all VLANs or the specified VLAN.
show mac address-table address
Displays MAC address table information for the specified MAC address.
show mac address-table aging-time
Displays the aging time in all VLANs or the specified VLAN.
show mac address-table count
Displays the number of addresses present in all VLANs or the specified VLAN.
show mac address-table dynamic
Displays only dynamic MAC address table entries.
show mac address-table interface
Displays the MAC address table information for the specified interface.
show mac address-table notification
Displays the MAC notification parameters and history table.
show mac address-table static
Displays only static MAC address table entries.
show mac address-table vlan
Displays the MAC address table information for the specified VLAN.
Managing the ARP Table
To communicate with a device (over Ethernet, for example), the software first must learn the 48-bit MAC
address or the local data link address of that device. The process of learning the local data link address
from an IP address is called address resolution.
The Address Resolution Protocol (ARP) associates a host IP address with the corresponding media or
MAC addresses and the VLAN ID. Using an IP address, ARP finds the associated MAC address. When
a MAC address is found, the IP-MAC address association is stored in an ARP cache for rapid retrieval.
Then the IP datagram is encapsulated in a link-layer frame and sent over the network. Encapsulation of
IP datagrams and ARP requests and replies on IEEE 802 networks other than Ethernet is specified by
the Subnetwork Access Protocol (SNAP). By default, standard Ethernet-style ARP encapsulation
(represented by the arpa keyword) is enabled on the IP interface.
ARP entries added manually to the table do not age and must be manually removed.
Note
For CLI procedures, see the Cisco IOS Release 12.2 documentation from the Cisco.com page under
Documentation > Cisco IOS Software > 12.2 Mainline.
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Administering the Switch
Managing the ARP Table
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6
Configuring SDM Templates
This chapter describes how to configure the Switch Database Management (SDM) templates on the
switch.
Note
For complete syntax and usage information for the commands used in this chapter, see the command
reference for this release.
This chapter consists of these sections:
•
Understanding the SDM Templates, page 6-1
•
Configuring the Switch SDM Template, page 6-3
•
Displaying the SDM Templates, page 6-5
Understanding the SDM Templates
You can use SDM templates to configure system resources in the switch to optimize support for specific
features, depending on how the switch is used in the network. You can select a template to provide
maximum system usage for some functions or use the default template to balance resources. For
example, you could use access template to obtain maximum ACL usage.
To allocate ternary content addressable memory (TCAM) resources for different usages, the switch SDM
templates prioritize system resources to optimize support for certain features. You can select SDM
templates for IP Version 4 (IPv4) to optimize these features:
•
Access—The access template maximizes system resources for access control lists (ACLs) to
accommodate a large number of ACLs.
•
Routing—The routing template maximizes system resources for unicast routing, typically required
for a router or aggregator in the center of a network.
•
VLANs—The VLAN template disables routing and supports the maximum number of unicast MAC
addresses. It would typically be selected for a Layer 2 switch.
•
Default—The default template gives balance to all functions.
You can also select a dual IPv4 and IPv6 template to support a a dual-stack environment. See the “Dual
IPv4 and IPv6 SDM Templates” section on page 6-2. You must enable a dual-stack template to configure
IPv6 host or IPv6 MLD snooping.
Table 6-1 lists the approximate numbers of each resource supported in each IPv4 template.
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Configuring SDM Templates
Understanding the SDM Templates
Table 6-1
Approximate Number of IPv4 Features Allowed by Each Template
Resource
Access
Default
Routing
VLAN
Unicast MAC addresses
4K
6K
3K
12 K
IGMP groups and multicast routes
1K
1K
1K
1K
Unicast routes
6K
8K
11 K
0
•
Directly connected hosts
4K
6K
3K
0
•
Indirect routes
2K
2K
8K
0
0.5 K
0
0.5 K
0
QoS classification ACEs
0.75K
0.75K
0.75K
0.75K
Security ACEs
2K
1K
1K
1K
Policy-based routing ACEs
1
1.Policy-based routing is not supported in the IP base image on the switch.
The rows in the table represent approximate hardware boundaries set when a template is selected. The
template optimizes resources in the switch to support the indicated level of features for 8 routed
interfaces and 1024 Layer 2 VLANs. If a section of a hardware resource is full, all processing overflow
is sent to the CPU, seriously impacting switch performance.
Dual IPv4 and IPv6 SDM Templates
You can select SDM templates to support IP Version 6 (IPv6). For more information about IPv6, see
Chapter 37, “Configuring IPv6 Unicast Routing.” The switch does not support IPv6 multicast routing
and QoS. This release does support IPv6 host and IPv6 Multicast Listener Discovery (MLD) snooping.
The dual IPv4 and IPv6 template allows the switch to be used in dual stack environments (supporting
both IPv4 and IPv6). Using the dual stack templates results in less TCAM capacity allowed for each
resource. Do not use them if you plan to forward only IPv4 traffic.
The dual IPv4 and IPv6 default template supports Layer 2, multicast, routing, QoS, and ACLs for IPv4;
and Layer 2, routing, and ACLs for IPv6 on the switch.
These SDM templates support IPv4 and IPv6 environments:
Note
•
The dual IPv4 and IPv6 default template supports Layer 2, multicast, routing, QoS, and ACLs for
IPv4; and Layer 2, routing, and ACLs for IPv6 on the switch.
•
The dual IPv4 and IPv6 routing template supports Layer 2, multicast, routing (including
policy-based routing), QoS, and ACLs for IPv4; and Layer 2, routing, and ACLs for IPv6 on the
switch.
•
The dual IPv4 and IPv6 VLAN template supports basic Layer 2, multicast, QoS, and ACLs for IPv4,
and basic Layer 2 and ACLs for IPv6 on the switch.
An IPv4 route requires only one TCAM entry. Because of the hardware compression scheme used for
IPv6, an IPv6 route can take more than one TCAM entry, reducing the number of entries forwarded in
hardware. For example, for IPv6 directly connected IP addresses, the desktop template might allow less
than two thousand entries.
Table 6-2 defines the approximate feature resources allocated by each new template. Template
estimations are based on a switch with 8 routed interfaces and approximately 1000 VLANs.
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Configuring SDM Templates
Configuring the Switch SDM Template
Table 6-2
Approximate Feature Resources Allowed by Dual IPv4-IPv6 Templates
Resource
IPv4-and-IPv6
Default
IPv4-and-IPv6
Routing
IPv4-and-IPv6
VLAN
Unicast MAC addresses
2K
1.5 K
8K
IPv4 IGMP groups and multicast routes
1K
1K
1K
Total IPv4 unicast routes:
3K
2.75 K
0
•
Directly connected IPv4 hosts
2K
1.5 K
0
•
Indirect IPv4 routes
1K
1.25 K
0
IPv6 multicast groups
1.125 K
1.125 K
1.125 K
Total IPv6 unicast routes:
3K
2.75 K
0
•
Directly connected IPv6 addresses
2K
1.5 K
0
•
Indirect IPv6 unicast routes
1K
1.25 K
0
0
0.25 K
0
IPv4 or MAC QoS ACEs (total)
0.75 K
0.75 K
0.75 K
IPv4 or MAC security ACEs (total)
1K
0.5 K
1K
IPv6 policy-based routing ACEs1
0
0.25 K
0
0.5 K
0.5 K
0.5 K
0.5 K
0.5 K
0.5 K
IPv4 policy-based routing ACEs
IPv6 QoS ACEs
1
1
IPv6 security ACEs
2
1. Not supported in the IP base image that runs on the switch.
2. The switch supports only input IPv6 router ACLs for management traffic.
Note
Although these features are visible in the template in the CLI, the switch does not support IPv4 or IPv6
policy-based routing or IPv6 Qos ACLs.
Configuring the Switch SDM Template
These sections contain this configuration information:
•
Default SDM Template, page 6-3
•
SDM Template Configuration Guidelines, page 6-4
•
Setting the SDM Template, page 6-4
Default SDM Template
The default template is the default.
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Configuring SDM Templates
Configuring the Switch SDM Template
SDM Template Configuration Guidelines
Follow these guidelines when selecting and configuring SDM templates:
•
When you select and configure SDM templates, you must reload the switch for the configuration to
take effect.
•
Use the sdm prefer vlan global configuration command only on switches intended for Layer 2
switching with no routing. When you use the VLAN template, no system resources are reserved for
routing entries, and any routing is done through software. This overloads the CPU and severely
degrades routing performance.
•
Do not use the routing template if you do not have routing enabled on your switch. The sdm prefer
routing global configuration command prevents other features from using the memory allocated to
unicast routing in the routing template.
•
If you try to configure IPv6 without first selecting a dual IPv4 and IPv6 template, a warning message
is generated.
•
Using the dual stack templates results in less TCAM capacity allowed for each resource, so do not
use if you plan to forward only IPv4 traffic.
•
Although these features are visible in the template in the CLI, the switch does not support IPv4 or
IPv6 policy-based routing or IPv6 Qos ACLs.
Setting the SDM Template
Beginning in privileged EXEC mode, follow these steps to use the SDM template to maximize feature
usage:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
sdm prefer {access | default |
dual-ipv4-and-ipv6 {default | routing |
vlan} | routing | vlan}
Specify the SDM template to be used on the switch:
The keywords have these meanings:
•
access—Maximizes system resources for ACLs.
•
default—Gives balance to all functions.
•
dual-ipv4-and-ipv6—Select a template that supports both IPv4
and IPv6 routing.
– default—Balance IPv4 and IPv6 Layer 2 and Layer 3
functionality.
– routing—Provide maximum usage for IPv4 and IPv6
routing, including IPv4 policy-based routing.
– vlan—Provide maximum usage for IPv4 and IPv6 VLANs.
•
routing—Maximizes routing on the switch.
•
vlan—Maximizes VLAN configuration on the switch with no
routing supported in hardware.
The default template balances the use of system resources.
Step 3
end
Return to privileged EXEC mode.
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Displaying the SDM Templates
Step 4
Command
Purpose
reload
Reload the operating system.
After the system reboots, you can use the show sdm prefer privileged EXEC command to verify the new
template configuration. If you enter the show sdm prefer command before you enter the reload
privileged EXEC command, the show sdm prefer command shows the template currently in use and the
template that will become active after a reload.
This is an example of an output display when you have changed the template and have not reloaded the
switch:
Switch# show sdm prefer
The current template is "desktop default" template.
The selected template optimizes the resources in
the switch to support this level of features for
8 routed interfaces and 1024 VLANs.
number of unicast mac addresses:
number of IPv4 IGMP groups + multicast routes:
number of IPv4 unicast routes:
number of directly-connected IPv4 hosts:
number of indirect IPv4 routes:
number of IPv4 policy based routing aces:
number of IPv4/MAC qos aces:
number of IPv4/MAC security aces:
6K
1K
8K
6K
2K
0
0.75K
1K
On next reload, template will be “desktop vlan” template.
To return to the default template, use the no sdm prefer global configuration command.
This example shows how to configure a switch with the routing template.
Switch(config)# sdm prefer routing
Switch(config)# end
Switch# reload
Proceed with reload? [confirm]
This example shows how to configure the IPv4-and-IPv6 default template on a switch:
Switch(config)# sdm prefer dual-ipv4-and-ipv6 default
Switch(config)# exit
Switch# reload
Proceed with reload? [confirm]
Displaying the SDM Templates
Use the show sdm prefer privileged EXEC command with no parameters to display the active template.
Use the show sdm prefer [access | default | dual-ipv4-and-ipv6 {default | vlan} |routing | vlan]
privileged EXEC command to display the resource numbers supported by the specified template.
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Displaying the SDM Templates
This is an example of output from the show sdm prefer command, displaying the template in use.
Switch# show sdm prefer
The current template is "desktop default" template.
The selected template optimizes the resources in
the switch to support this level of features for
8 routed interfaces and 1024 VLANs.
number of unicast mac addresses:
number of IPv4 IGMP groups + multicast routes:
number of IPv4 unicast routes:
number of directly-connected IPv4 hosts:
number of indirect IPv4 routes:
number of IPv4 policy based routing aces:
number of IPv4/MAC qos aces:
number of IPv4/MAC security aces:
6K
1K
8K
6K
2K
0
0.75K
1K
This is an example of output from the show sdm prefer routing command:
Switch# show sdm prefer routing
"desktop routing" template:
The selected template optimizes the resources in
the switch to support this level of features for
8 routed interfaces and 1024 VLANs.
number of unicast mac addresses:
number of IPv4 IGMP groups + multicast routes:
number of IPv4 unicast routes:
number of directly-connected IPv4 hosts:
number of indirect IPv4 routes:
number of IPv4 policy based routing aces:
number of IPv4/MAC qos aces:
number of IPv4/MAC security aces:
3K
1K
11K
3K
8K
0.5K
0.75K
1K
This is an example of output from the show sdm prefer dual-ipv4-and-ipv6 default command:
Switch# show sdm prefer dual-ipv4-and-ipv6 default
"desktop IPv4 and IPv6 default" template:
The selected template optimizes the resources in
the switch to support this level of features for
8 routed interfaces and 1024 VLANs.
number of unicast mac addresses:
number of IPv4 IGMP groups + multicast routes:
number of IPv4 unicast routes:
number of directly-connected IPv4 hosts:
number of indirect IPv4 routes:
number of IPv6 multicast groups:
number of directly-connected IPv6 addresses:
number of indirect IPv6 unicast routes:
number of IPv4 policy based routing aces:
number of IPv4/MAC qos aces:
number of IPv4/MAC security aces:
number of IPv6 policy based routing aces:
number of IPv6 qos aces:
number of IPv6 security aces:
2K
1K
3K
2K
1K
1.125k
2K
1K
0
0.75K
1K
0
0.5K
0.5K
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7
Configuring Switch-Based Authentication
This chapter describes how to configure switch-based authentication on the switch. It consists of these
sections:
•
Preventing Unauthorized Access to Your Switch, page 7-1
•
Protecting Access to Privileged EXEC Commands, page 7-2
•
Controlling Switch Access with TACACS+, page 7-10
•
Controlling Switch Access with RADIUS, page 7-17
•
Controlling Switch Access with Kerberos, page 7-38
•
Configuring the Switch for Local Authentication and Authorization, page 7-42
•
Configuring the Switch for Secure Shell, page 7-43
•
Configuring the Switch for Secure Socket Layer HTTP, page 7-48
•
Configuring the Switch for Secure Copy Protocol, page 7-55
Preventing Unauthorized Access to Your Switch
You can prevent unauthorized users from reconfiguring your switch and viewing configuration
information. Typically, you want network administrators to have access to your switch while you restrict
access to users who dial from outside the network through an asynchronous port, connect from outside
the network through a serial port, or connect through a terminal or workstation from within the local
network.
To prevent unauthorized access into your switch, you should configure one or more of these security
features:
•
At a minimum, you should configure passwords and privileges at each switch port. These passwords
are locally stored on the switch. When users attempt to access the switch through a port or line, they
must enter the password specified for the port or line before they can access the switch. For more
information, see the “Protecting Access to Privileged EXEC Commands” section on page 7-2.
•
For an additional layer of security, you can also configure username and password pairs, which are
locally stored on the switch. These pairs are assigned to lines or ports and authenticate each user
before that user can access the switch. If you have defined privilege levels, you can also assign a
specific privilege level (with associated rights and privileges) to each username and password pair.
For more information, see the “Configuring Username and Password Pairs” section on page 7-6.
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Protecting Access to Privileged EXEC Commands
•
If you want to use username and password pairs, but you want to store them centrally on a server
instead of locally, you can store them in a database on a security server. Multiple networking devices
can then use the same database to obtain user authentication (and, if necessary, authorization)
information. For more information, see the “Controlling Switch Access with TACACS+” section on
page 7-10.
Protecting Access to Privileged EXEC Commands
A simple way of providing terminal access control in your network is to use passwords and assign
privilege levels. Password protection restricts access to a network or network device. Privilege levels
define what commands users can enter after they have logged into a network device.
Note
For complete syntax and usage information for the commands used in this section, see the Cisco IOS
Security Command Reference, Release 12.2 from the Cisco.com page under Documentation > Cisco
IOS Software > 12.2 Mainline > Command References.
These sections contain this configuration information:
•
Default Password and Privilege Level Configuration, page 7-2
•
Setting or Changing a Static Enable Password, page 7-3
•
Protecting Enable and Enable Secret Passwords with Encryption, page 7-3
•
Disabling Password Recovery, page 7-5
•
Setting a Telnet Password for a Terminal Line, page 7-6
•
Configuring Username and Password Pairs, page 7-6
•
Configuring Multiple Privilege Levels, page 7-7
Default Password and Privilege Level Configuration
Table 7-1 shows the default password and privilege level configuration.
Table 7-1
Default Password and Privilege Levels
Feature
Default Setting
Enable password and privilege level
No password is defined. The default is level 15 (privileged EXEC level).
The password is not encrypted in the configuration file.
Enable secret password and privilege level
No password is defined. The default is level 15 (privileged EXEC level).
The password is encrypted before it is written to the configuration file.
Line password
No password is defined.
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Configuring Switch-Based Authentication
Protecting Access to Privileged EXEC Commands
Setting or Changing a Static Enable Password
The enable password controls access to the privileged EXEC mode. Beginning in privileged EXEC
mode, follow these steps to set or change a static enable password:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
enable password password
Define a new password or change an existing password for access to
privileged EXEC mode.
By default, no password is defined.
For password, specify a string from 1 to 25 alphanumeric characters. The
string cannot start with a number, is case sensitive, and allows spaces but
ignores leading spaces. It can contain the question mark (?) character if
you precede the question mark with the key combination Crtl-v when you
create the password; for example, to create the password abc?123, do this:
Enter abc.
Enter Crtl-v.
Enter ?123.
When the system prompts you to enter the enable password, you need not
precede the question mark with the Ctrl-v; you can simply enter abc?123
at the password prompt.
Step 3
end
Return to privileged EXEC mode.
Step 4
show running-config
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
The enable password is not encrypted and can be read in the switch
configuration file.
To remove the password, use the no enable password global configuration command.
This example shows how to change the enable password to l1u2c3k4y5. The password is not encrypted
and provides access to level 15 (traditional privileged EXEC mode access):
Switch(config)# enable password l1u2c3k4y5
Protecting Enable and Enable Secret Passwords with Encryption
To provide an additional layer of security, particularly for passwords that cross the network or that are
stored on a Trivial File Transfer Protocol (TFTP) server, you can use either the enable password or
enable secret global configuration commands. Both commands accomplish the same thing; that is, you
can establish an encrypted password that users must enter to access privileged EXEC mode (the default)
or any privilege level you specify.
We recommend that you use the enable secret command because it uses an improved encryption
algorithm.
If you configure the enable secret command, it takes precedence over the enable password command;
the two commands cannot be in effect simultaneously.
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Configuring Switch-Based Authentication
Protecting Access to Privileged EXEC Commands
Beginning in privileged EXEC mode, follow these steps to configure encryption for enable and enable
secret passwords:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
enable password [level level] {password |
encryption-type encrypted-password}
Define a new password or change an existing password for
access to privileged EXEC mode.
or
or
enable secret [level level] {password |
encryption-type encrypted-password}
Define a secret password, which is saved using a
nonreversible encryption method.
•
(Optional) For level, the range is from 0 to 15. Level 1 is
normal user EXEC mode privileges. The default level is
15 (privileged EXEC mode privileges).
•
For password, specify a string from 1 to 25
alphanumeric characters. The string cannot start with a
number, is case sensitive, and allows spaces but ignores
leading spaces. By default, no password is defined.
•
(Optional) For encryption-type, only type 5, a Cisco
proprietary encryption algorithm, is available. If you
specify an encryption type, you must provide an
encrypted password—an encrypted password that you
copy from another switch configuration.
Note
Step 3
service password-encryption
If you specify an encryption type and then enter a
clear text password, you can not re-enter privileged
EXEC mode. You cannot recover a lost encrypted
password by any method.
(Optional) Encrypt the password when the password is
defined or when the configuration is written.
Encryption prevents the password from being readable in the
configuration file.
Step 4
end
Return to privileged EXEC mode.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
If both the enable and enable secret passwords are defined, users must enter the enable secret password.
Use the level keyword to define a password for a specific privilege level. After you specify the level and
set a password, give the password only to users who need to have access at this level. Use the privilege
level global configuration command to specify commands accessible at various levels. For more
information, see the “Configuring Multiple Privilege Levels” section on page 7-7.
If you enable password encryption, it applies to all passwords including username passwords,
authentication key passwords, the privileged command password, and console and virtual terminal line
passwords.
To remove a password and level, use the no enable password [level level] or no enable secret [level
level] global configuration command. To disable password encryption, use the no service
password-encryption global configuration command.
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Configuring Switch-Based Authentication
Protecting Access to Privileged EXEC Commands
This example shows how to configure the encrypted password $1$FaD0$Xyti5Rkls3LoyxzS8 for
privilege level 2:
Switch(config)# enable secret level 2 5 $1$FaD0$Xyti5Rkls3LoyxzS8
Disabling Password Recovery
By default, any end user with physical access to the switch can recover from a lost password by
interrupting the bootup process while the switch is powering on and then by entering a new password.
The password-recovery disable feature protects access to the switch password by disabling part of this
functionality. When this feature is enabled, the end user can interrupt the bootup process only by
agreeing to set the system back to the default configuration. With password recovery disabled, you can
still interrupt the bootup process and change the password, but the configuration file (config.text) and
the VLAN database file (vlan.dat) are deleted.
Note
If you disable password recovery, we recommend that you keep a backup copy of the configuration file
on a secure server in case the end user interrupts the bootup process and sets the system back to default
values. Do not keep a backup copy of the configuration file on the switch. If the switch is operating in
VTP transparent mode, we recommend that you also keep a backup copy of the VLAN database file on
a secure server. When the switch is returned to the default system configuration, you can download the
saved files to the switch by using the Xmodem protocol. For more information, see the “Recovering from
a Lost or Forgotten Password” section on page 42-4.
Beginning in privileged EXEC mode, follow these steps to disable password recovery:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
no service password-recovery
Disable password recovery.
This setting is saved in an area of the flash memory that is accessible by
the bootloader and the Cisco IOS image, but it is not part of the file system
and is not accessible by any user.
Step 3
end
Return to privileged EXEC mode.
Step 4
show version
Verify the configuration by checking the last few lines of the command
output.
To re-enable password recovery, use the service password-recovery global configuration command.
Note
Disabling password recovery will not work if you have set the switch to boot up manually by using the
boot manual global configuration command. This command produces the bootloader prompt (switch:)
after the switch is power cycled.
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Protecting Access to Privileged EXEC Commands
Setting a Telnet Password for a Terminal Line
When you power-up your switch for the first time, an automatic setup program runs to assign IP
information and to create a default configuration for continued use. The setup program also prompts you
to configure your switch for Telnet access through a password. If you did not configure this password
during the setup program, you can configure it now through the command-line interface (CLI).
Beginning in privileged EXEC mode, follow these steps to configure your switch for Telnet access:
Command
Purpose
Step 1
Attach a PC or workstation with emulation software to the switch console
port.
The default data characteristics of the console port are 9600, 8, 1, no
parity. You might need to press the Return key several times to see the
command-line prompt.
Step 2
enable password password
Enter privileged EXEC mode.
Step 3
configure terminal
Enter global configuration mode.
Step 4
line vty 0 15
Configure the number of Telnet sessions (lines), and enter line
configuration mode.
There are 16 possible sessions on a command-capable switch. The 0
and 15 mean that you are configuring all 16 possible Telnet sessions.
Step 5
password password
Enter a Telnet password for the line or lines.
For password, specify a string from 1 to 25 alphanumeric characters. The
string cannot start with a number, is case sensitive, and allows spaces but
ignores leading spaces. By default, no password is defined.
Step 6
end
Return to privileged EXEC mode.
Step 7
show running-config
Verify your entries.
The password is listed under the command line vty 0 15.
Step 8
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To remove the password, use the no password global configuration command.
This example shows how to set the Telnet password to let45me67in89:
Switch(config)# line vty 10
Switch(config-line)# password let45me67in89
Configuring Username and Password Pairs
You can configure username and password pairs, which are locally stored on the switch. These pairs are
assigned to lines or ports and authenticate each user before that user can access the switch. If you have
defined privilege levels, you can also assign a specific privilege level (with associated rights and
privileges) to each username and password pair.
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Beginning in privileged EXEC mode, follow these steps to establish a username-based authentication
system that requests a login username and a password:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
username name [privilege level]
{password encryption-type password}
Enter the username, privilege level, and password for each user.
Step 3
•
For name, specify the user ID as one word. Spaces and quotation
marks are not allowed.
•
(Optional) For level, specify the privilege level the user has after
gaining access. The range is 0 to 15. Level 15 gives privileged EXEC
mode access. Level 1 gives user EXEC mode access.
•
For encryption-type, enter 0 to specify that an unencrypted password
will follow. Enter 7 to specify that a hidden password will follow.
•
For password, specify the password the user must enter to gain access
to the switch. The password must be from 1 to 25 characters, can
contain embedded spaces, and must be the last option specified in the
username command.
Enter line configuration mode, and configure the console port (line 0) or
the VTY lines (line 0 to 15).
line console 0
or
line vty 0 15
Step 4
login local
Enable local password checking at login time. Authentication is based on
the username specified in Step 2.
Step 5
end
Return to privileged EXEC mode.
Step 6
show running-config
Verify your entries.
Step 7
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To disable username authentication for a specific user, use the no username name global configuration
command. To disable password checking and allow connections without a password, use the no login
line configuration command.
Configuring Multiple Privilege Levels
By default, the Cisco IOS software has two modes of password security: user EXEC and privileged
EXEC. You can configure up to 16 hierarchical levels of commands for each mode. By configuring
multiple passwords, you can allow different sets of users to have access to specified commands.
For example, if you want many users to have access to the clear line command, you can assign it
level 2 security and distribute the level 2 password fairly widely. But if you want more restricted access
to the configure command, you can assign it level 3 security and distribute that password to a more
restricted group of users.
These sections contain this configuration information:
•
Setting the Privilege Level for a Command, page 7-8
•
Changing the Default Privilege Level for Lines, page 7-9
•
Logging into and Exiting a Privilege Level, page 7-9
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Protecting Access to Privileged EXEC Commands
Setting the Privilege Level for a Command
Beginning in privileged EXEC mode, follow these steps to set the privilege level for a command mode:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
privilege mode level level command
Set the privilege level for a command.
Step 3
enable password level level password
•
For mode, enter configure for global configuration mode, exec for
EXEC mode, interface for interface configuration mode, or line for
line configuration mode.
•
For level, the range is from 0 to 15. Level 1 is for normal user EXEC
mode privileges. Level 15 is the level of access permitted by the
enable password.
•
For command, specify the command to which you want to restrict
access.
Specify the enable password for the privilege level.
•
For level, the range is from 0 to 15. Level 1 is for normal user EXEC
mode privileges.
•
For password, specify a string from 1 to 25 alphanumeric characters.
The string cannot start with a number, is case sensitive, and allows
spaces but ignores leading spaces. By default, no password is
defined.
Step 4
end
Return to privileged EXEC mode.
Step 5
show running-config
Verify your entries.
or
show privilege
The first command shows the password and access level configuration.
The second command shows the privilege level configuration.
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Step 6
When you set a command to a privilege level, all commands whose syntax is a subset of that command
are also set to that level. For example, if you set the show ip traffic command to level 15, the show
commands and show ip commands are automatically set to privilege level 15 unless you set them
individually to different levels.
To return to the default privilege for a given command, use the no privilege mode level level command
global configuration command.
This example shows how to set the configure command to privilege level 14 and define SecretPswd14
as the password users must enter to use level 14 commands:
Switch(config)# privilege exec level 14 configure
Switch(config)# enable password level 14 SecretPswd14
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Changing the Default Privilege Level for Lines
Beginning in privileged EXEC mode, follow these steps to change the default privilege level for a line:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
line vty line
Select the virtual terminal line on which to restrict access.
Step 3
privilege level level
Change the default privilege level for the line.
For level, the range is from 0 to 15. Level 1 is for normal user EXEC mode
privileges. Level 15 is the level of access permitted by the enable
password.
Step 4
end
Return to privileged EXEC mode.
Step 5
show running-config
Verify your entries.
or
show privilege
The first command shows the password and access level configuration.
The second command shows the privilege level configuration.
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Step 6
Users can override the privilege level you set using the privilege level line configuration command by
logging in to the line and enabling a different privilege level. They can lower the privilege level by using
the disable command. If users know the password to a higher privilege level, they can use that password
to enable the higher privilege level. You might specify a high level or privilege level for your console
line to restrict line usage.
To return to the default line privilege level, use the no privilege level line configuration command.
Logging into and Exiting a Privilege Level
Beginning in privileged EXEC mode, follow these steps to log in to a specified privilege level and to exit
to a specified privilege level:
Step 1
Command
Purpose
enable level
Log in to a specified privilege level.
For level, the range is 0 to 15.
Step 2
disable level
Exit to a specified privilege level.
For level, the range is 0 to 15.
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Controlling Switch Access with TACACS+
Controlling Switch Access with TACACS+
This section describes how to enable and configure Terminal Access Controller Access Control System
Plus (TACACS+), which provides detailed accounting information and flexible administrative control
over authentication and authorization processes. TACACS+ is facilitated through authentication,
authorization, accounting (AAA) and can be enabled only through AAA commands.
Beginning with Cisco IOS Release 12.2(58)SE, the switch supports TACACS+ for IPv6. For information
about configuring this feature, see the “Implementing ADSL for IPv6” chapter in the Cisco IOS XE IPv6
Configuration Guide, Release 2.
Note
For complete syntax and usage information for the commands used in this section, see the Cisco IOS
Security Command Reference, Release 12.2.
These sections contain this configuration information:
•
Understanding TACACS+, page 7-10
•
TACACS+ Operation, page 7-12
•
Configuring TACACS+, page 7-12
•
Displaying the TACACS+ Configuration, page 7-17
Understanding TACACS+
TACACS+ is a security application that provides centralized validation of users attempting to gain access
to your switch. TACACS+ services are maintained in a database on a TACACS+ daemon typically
running on a UNIX or Windows NT workstation. You should have access to and should configure a
TACACS+ server before the configuring TACACS+ features on your switch.
TACACS+ provides for separate and modular authentication, authorization, and accounting facilities.
TACACS+ allows for a single access control server (the TACACS+ daemon) to provide each
service—authentication, authorization, and accounting—independently. Each service can be tied into its
own database to take advantage of other services available on that server or on the network, depending
on the capabilities of the daemon.
The goal of TACACS+ is to provide a method for managing multiple network access points from a single
management service. Your switch can be a network access server along with other Cisco routers and
access servers. A network access server provides connections to a single user, to a network or
subnetwork, and to interconnected networks as shown in Figure 7-1.
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Figure 7-1
Typical TACACS+ Network Configuration
UNIX workstation
(TACACS+
server 1)
Catalyst 6500
series switch
171.20.10.7
UNIX workstation
(TACACS+
server 2)
171.20.10.8
119942
Configure the Blade switches with the
TACACS+ server addresses.
Set an authentication key
(also configure the same key on
the TACACS+ servers).
Enable AAA.
Create a login authentication method list.
Apply the list to the terminal lines.
Create an authorization and accounting
Blade servers
method list as required.
Blade servers
TACACS+, administered through the AAA security services, can provide these services:
•
Authentication—Provides complete control of authentication through login and password dialog,
challenge and response, and messaging support.
The authentication facility can conduct a dialog with the user (for example, after a username and
password are provided, to challenge a user with several questions, such as home address, mother’s
maiden name, service type, and social security number). The TACACS+ authentication service can
also send messages to user screens. For example, a message could notify users that their passwords
must be changed because of the company’s password aging policy.
•
Authorization—Provides fine-grained control over user capabilities for the duration of the user’s
session, including but not limited to setting autocommands, access control, session duration, or
protocol support. You can also enforce restrictions on what commands a user can execute with the
TACACS+ authorization feature.
•
Accounting—Collects and sends information used for billing, auditing, and reporting to the
TACACS+ daemon. Network managers can use the accounting facility to track user activity for a
security audit or to provide information for user billing. Accounting records include user identities,
start and stop times, executed commands (such as PPP), number of packets, and number of bytes.
The TACACS+ protocol provides authentication between the switch and the TACACS+ daemon, and it
ensures confidentiality because all protocol exchanges between the switch and the TACACS+ daemon
are encrypted.
You need a system running the TACACS+ daemon software to use TACACS+ on your switch.
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TACACS+ Operation
When a user attempts a simple ASCII login by authenticating to a switch using TACACS+, this process
occurs:
1.
When the connection is established, the switch contacts the TACACS+ daemon to obtain a username
prompt to show to the user. The user enters a username, and the switch then contacts the TACACS+
daemon to obtain a password prompt. The switch displays the password prompt to the user, the user
enters a password, and the password is then sent to the TACACS+ daemon.
TACACS+ allows a dialog between the daemon and the user until the daemon receives enough
information to authenticate the user. The daemon prompts for a username and password
combination, but can include other items, such as the user’s mother’s maiden name.
2.
The switch eventually receives one of these responses from the TACACS+ daemon:
•
ACCEPT—The user is authenticated and service can begin. If the switch is configured to
require authorization, authorization begins at this time.
•
REJECT—The user is not authenticated. The user can be denied access or is prompted to retry
the login sequence, depending on the TACACS+ daemon.
•
ERROR—An error occurred at some time during authentication with the daemon or in the
network connection between the daemon and the switch. If an ERROR response is received, the
switch typically tries to use an alternative method for authenticating the user.
•
CONTINUE—The user is prompted for additional authentication information.
After authentication, the user undergoes an additional authorization phase if authorization has been
enabled on the switch. Users must first successfully complete TACACS+ authentication before
proceeding to TACACS+ authorization.
3.
If TACACS+ authorization is required, the TACACS+ daemon is again contacted, and it returns an
ACCEPT or REJECT authorization response. If an ACCEPT response is returned, the response
contains data in the form of attributes that direct the EXEC or NETWORK session for that user and
the services that the user can access:
•
Telnet, Secure Shell (SSH), rlogin, or privileged EXEC services
•
Connection parameters, including the host or client IP address, access list, and user timeouts
Configuring TACACS+
This section describes how to configure your switch to support TACACS+. At a minimum, you must
identify the host or hosts maintaining the TACACS+ daemon and define the method lists for TACACS+
authentication. You can optionally define method lists for TACACS+ authorization and accounting. A
method list defines the sequence and methods to be used to authenticate, to authorize, or to keep accounts
on a user. You can use method lists to designate one or more security protocols to be used, thus ensuring
a backup system if the initial method fails. The software uses the first method listed to authenticate, to
authorize, or to keep accounts on users; if that method does not respond, the software selects the next
method in the list. This process continues until there is successful communication with a listed method
or the method list is exhausted.
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These sections contain this configuration information:
•
Default TACACS+ Configuration, page 7-13
•
Identifying the TACACS+ Server Host and Setting the Authentication Key, page 7-13
•
Configuring TACACS+ Login Authentication, page 7-14
•
Configuring TACACS+ Authorization for Privileged EXEC Access and Network Services,
page 7-16
•
Starting TACACS+ Accounting, page 7-17
Default TACACS+ Configuration
TACACS+ and AAA are disabled by default.
To prevent a lapse in security, you cannot configure TACACS+ through a network management
application. When enabled, TACACS+ can authenticate users accessing the switch through the CLI.
Note
Although TACACS+ configuration is performed through the CLI, the TACACS+ server authenticates
HTTP connections that have been configured with a privilege level of 15.
Identifying the TACACS+ Server Host and Setting the Authentication Key
You can configure the switch to use a single server or AAA server groups to group existing server hosts
for authentication. You can group servers to select a subset of the configured server hosts and use them
for a particular service. The server group is used with a global server-host list and contains the list of IP
addresses of the selected server hosts.
Beginning in privileged EXEC mode, follow these steps to identify the IP host or host maintaining
TACACS+ server and optionally set the encryption key:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
tacacs-server host hostname [port
integer] [timeout integer] [key string]
Identify the IP host or hosts maintaining a TACACS+ server. Enter this
command multiple times to create a list of preferred hosts. The software
searches for hosts in the order in which you specify them.
Step 3
aaa new-model
•
For hostname, specify the name or IP address of the host.
•
(Optional) For port integer, specify a server port number. The default
is port 49. The range is 1 to 65535.
•
(Optional) For timeout integer, specify a time in seconds the switch
waits for a response from the daemon before it times out and declares
an error. The default is 5 seconds. The range is 1 to 1000 seconds.
•
(Optional) For key string, specify the encryption key for encrypting
and decrypting all traffic between the switch and the TACACS+
daemon. You must configure the same key on the TACACS+ daemon
for encryption to be successful.
Enable AAA.
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Step 4
Command
Purpose
aaa group server tacacs+ group-name
(Optional) Define the AAA server-group with a group name.
This command puts the switch in a server group subconfiguration mode.
Step 5
server ip-address
(Optional) Associate a particular TACACS+ server with the defined server
group. Repeat this step for each TACACS+ server in the AAA server
group.
Each server in the group must be previously defined in Step 2.
Step 6
end
Return to privileged EXEC mode.
Step 7
show tacacs
Verify your entries.
Step 8
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To remove the specified TACACS+ server name or address, use the no tacacs-server host hostname
global configuration command. To remove a server group from the configuration list, use the no aaa
group server tacacs+ group-name global configuration command. To remove the IP address of a
TACACS+ server, use the no server ip-address server group subconfiguration command.
Configuring TACACS+ Login Authentication
To configure AAA authentication, you define a named list of authentication methods and then apply that
list to various ports. The method list defines the types of authentication to be performed and the sequence
in which they are performed; it must be applied to a specific port before any of the defined authentication
methods are performed. The only exception is the default method list (which, by coincidence, is named
default). The default method list is automatically applied to all ports except those that have a named
method list explicitly defined. A defined method list overrides the default method list.
A method list describes the sequence and authentication methods to be queried to authenticate a user.
You can designate one or more security protocols to be used for authentication, thus ensuring a backup
system for authentication in case the initial method fails. The software uses the first method listed to
authenticate users; if that method fails to respond, the software selects the next authentication method in
the method list. This process continues until there is successful communication with a listed
authentication method or until all defined methods are exhausted. If authentication fails at any point in
this cycle—meaning that the security server or local username database responds by denying the user
access—the authentication process stops, and no other authentication methods are attempted.
Beginning in privileged EXEC mode, follow these steps to configure login authentication:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
aaa new-model
Enable AAA.
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Step 3
Command
Purpose
aaa authentication login {default |
list-name} method1 [method2...]
Create a login authentication method list.
•
To create a default list that is used when a named list is not specified
in the login authentication command, use the default keyword
followed by the methods that are to be used in default situations. The
default method list is automatically applied to all ports.
•
For list-name, specify a character string to name the list you are
creating.
•
For method1..., specify the actual method the authentication
algorithm tries. The additional methods of authentication are used
only if the previous method returns an error, not if it fails.
Select one of these methods:
•
enable—Use the enable password for authentication. Before you can
use this authentication method, you must define an enable password
by using the enable password global configuration command.
•
group tacacs+—Uses TACACS+ authentication. Before you can use
this authentication method, you must configure the TACACS+ server.
For more information, see the “Identifying the TACACS+ Server Host
and Setting the Authentication Key” section on page 7-13.
•
line—Use the line password for authentication. Before you can use
this authentication method, you must define a line password. Use the
password password line configuration command.
•
local—Use the local username database for authentication. You must
enter username information in the database. Use the username
password global configuration command.
•
local-case—Use a case-sensitive local username database for
authentication. You must enter username information in the database
by using the username name password global configuration
command.
•
none—Do not use any authentication for login.
Step 4
line [console | tty | vty] line-number
[ending-line-number]
Enter line configuration mode, and configure the lines to which you want
to apply the authentication list.
Step 5
login authentication {default |
list-name}
Apply the authentication list to a line or set of lines.
•
If you specify default, use the default list created with the aaa
authentication login command.
•
For list-name, specify the list created with the aaa authentication
login command.
Step 6
end
Return to privileged EXEC mode.
Step 7
show running-config
Verify your entries.
Step 8
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To disable AAA, use the no aaa new-model global configuration command. To disable AAA
authentication, use the no aaa authentication login {default | list-name} method1 [method2...] global
configuration command. To either disable TACACS+ authentication for logins or to return to the default
value, use the no login authentication {default | list-name} line configuration command.
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Controlling Switch Access with TACACS+
Note
To secure the switch for HTTP access by using AAA methods, you must configure the switch with the
ip http authentication aaa global configuration command. Configuring AAA authentication does not
secure the switch for HTTP access by using AAA methods.
For more information about the ip http authentication command, see the Cisco IOS Security Command
Reference, Release 12.2 from the Cisco.com page under Documentation > Cisco IOS Software > 12.2
Mainline > Command References.
Configuring TACACS+ Authorization for Privileged EXEC Access and Network Services
AAA authorization limits the services available to a user. When AAA authorization is enabled, the
switch uses information retrieved from the user’s profile, which is located either in the local user
database or on the security server, to configure the user’s session. The user is granted access to a
requested service only if the information in the user profile allows it.
You can use the aaa authorization global configuration command with the tacacs+ keyword to set
parameters that restrict a user’s network access to privileged EXEC mode.
The aaa authorization exec tacacs+ local command sets these authorization parameters:
Note
•
Use TACACS+ for privileged EXEC access authorization if authentication was performed by using
TACACS+.
•
Use the local database if authentication was not performed by using TACACS+.
Authorization is bypassed for authenticated users who log in through the CLI even if authorization has
been configured.
Beginning in privileged EXEC mode, follow these steps to specify TACACS+ authorization for
privileged EXEC access and network services:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
aaa authorization network tacacs+
Configure the switch for user TACACS+ authorization for all
network-related service requests.
Step 3
aaa authorization exec tacacs+
Configure the switch for user TACACS+ authorization if the user has
privileged EXEC access.
The exec keyword might return user profile information (such as
autocommand information).
Step 4
end
Return to privileged EXEC mode.
Step 5
show running-config
Verify your entries.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To disable authorization, use the no aaa authorization {network | exec} method1 global configuration
command.
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Starting TACACS+ Accounting
The AAA accounting feature tracks the services that users are accessing and the amount of network
resources that they are consuming. When AAA accounting is enabled, the switch reports user activity to
the TACACS+ security server in the form of accounting records. Each accounting record contains
accounting attribute-value (AV) pairs and is stored on the security server. This data can then be analyzed
for network management, client billing, or auditing.
Beginning in privileged EXEC mode, follow these steps to enable TACACS+ accounting for each Cisco
IOS privilege level and for network services:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
aaa accounting network start-stop
tacacs+
Enable TACACS+ accounting for all network-related service requests.
Step 3
aaa accounting exec start-stop tacacs+
Enable TACACS+ accounting to send a start-record accounting notice at
the beginning of a privileged EXEC process and a stop-record at the end.
Step 4
end
Return to privileged EXEC mode.
Step 5
show running-config
Verify your entries.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To disable accounting, use the no aaa accounting {network | exec} {start-stop} method1... global
configuration command.
Establishing a Session with a Router if the AAA Server is Unreachable
The aaa accounting system guarantee-first command guarantees system accounting as the first record,
which is the default condition. In some situations, users might be prevented from starting a session on
the console or terminal connection until after the system reloads, which can take more than 3 minutes.
To establish a console or Telnet session with the router if the AAA server is unreachable when the router
reloads, use the no aaa accounting system guarantee-first command.
Displaying the TACACS+ Configuration
To display TACACS+ server statistics, use the show tacacs privileged EXEC command.
Controlling Switch Access with RADIUS
This section describes how to enable and configure the RADIUS, which provides detailed accounting
information and flexible administrative control over authentication and authorization processes.
RADIUS is facilitated through AAA and can be enabled only through AAA commands.
Beginning with Cisco IOS Release 12.2(58)SE, the switch supports RADIUS for IPv6. For information
about configuring this feature, see the “Implementing ADSL for IPv6” chapter in the Cisco IOS XE IPv6
Configuration Guide, Release 2.
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Note
For complete syntax and usage information for the commands used in this section, see the Cisco IOS
Security Command Reference, Release 12.2.
These sections contain this configuration information:
•
Understanding RADIUS, page 7-18
•
RADIUS Operation, page 7-19
•
RADIUS Change of Authorization, page 7-20
•
Configuring RADIUS, page 7-25
•
Displaying the RADIUS Configuration, page 7-38
Understanding RADIUS
RADIUS is a distributed client/server system that secures networks against unauthorized access.
RADIUS clients run on supported Cisco routers and switches. Clients send authentication requests to a
central RADIUS server, which contains all user authentication and network service access information.
The RADIUS host is normally a multiuser system running RADIUS server software from Cisco (Cisco
Secure Access Control Server Version 3.0), Livingston, Merit, Microsoft, or another software provider.
For more information, see the RADIUS server documentation.
Use RADIUS in these network environments that require access security:
•
Networks with multiple-vendor access servers, each supporting RADIUS. For example, access
servers from several vendors use a single RADIUS server-based security database. In an IP-based
network with multiple vendors’ access servers, dial-in users are authenticated through a RADIUS
server that has been customized to work with the Kerberos security system.
•
Turnkey network security environments in which applications support the RADIUS protocol, such
as in an access environment that uses a smart card access control system. In one case, RADIUS has
been used with Enigma’s security cards to validates users and to grant access to network resources.
•
Networks already using RADIUS. You can add a Cisco switch containing a RADIUS client to the
network. This might be the first step when you make a transition to a TACACS+ server. See
Figure 7-2 on page 7-19.
•
Network in which the user must only access a single service. Using RADIUS, you can control user
access to a single host, to a single utility such as Telnet, or to the network through a protocol such
as IEEE 802.1x. For more information about this protocol, see Chapter 8, “Configuring IEEE 802.1x
Port-Based Authentication.”
•
Networks that require resource accounting. You can use RADIUS accounting independently of
RADIUS authentication or authorization. The RADIUS accounting functions allow data to be sent
at the start and end of services, showing the amount of resources (such as time, packets, bytes, and
so forth) used during the session. An Internet service provider might use a freeware-based version
of RADIUS access control and accounting software to meet special security and billing needs.
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RADIUS is not suitable in these network security situations:
•
Multiprotocol access environments. RADIUS does not support AppleTalk Remote Access (ARA),
NetBIOS Frame Control Protocol (NBFCP), NetWare Asynchronous Services Interface (NASI), or
X.25 PAD connections.
•
Switch-to-switch or router-to-router situations. RADIUS does not provide two-way authentication.
RADIUS can be used to authenticate from one device to a non-Cisco device if the non-Cisco device
requires authentication.
•
Networks using a variety of services. RADIUS generally binds a user to one service model.
Transitioning from RADIUS to TACACS+ Services
Remote
PC
R1
RADIUS
server
R2
RADIUS
server
T1
TACACS+
server
T2
TACACS+
server
Workstation
86891
Figure 7-2
RADIUS Operation
When a user attempts to log in and authenticate to a switch that is access controlled by a RADIUS server,
these events occur:
1.
The user is prompted to enter a username and password.
2.
The username and encrypted password are sent over the network to the RADIUS server.
3.
The user receives one of these responses from the RADIUS server:
a. ACCEPT—The user is authenticated.
b. REJECT—The user is either not authenticated and is prompted to re-enter the username and
password, or access is denied.
c. CHALLENGE—A challenge requires additional data from the user.
d. CHALLENGE PASSWORD—A response requests the user to select a new password.
The ACCEPT or REJECT response is bundled with additional data that is used for privileged EXEC or
network authorization. Users must first successfully complete RADIUS authentication before
proceeding to RADIUS authorization, if it is enabled. The additional data included with the ACCEPT or
REJECT packets includes these items:
•
Telnet, SSH, rlogin, or privileged EXEC services
•
Connection parameters, including the host or client IP address, access list, and user timeouts
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RADIUS Change of Authorization
This section provides an overview of the RADIUS interface including available primitives and how they
are used during a Change of Authorization (CoA).
•
Overview, page 7-20
•
Change-of-Authorization Requests, page 7-20
•
CoA Request Response Code, page 7-22
•
CoA Request Commands, page 7-23
•
Session Reauthentication, page 7-23
Overview
A standard RADIUS interface is typically used in a pulled model where the request originates from a
network attached device and the response come from the queried servers. Catalyst switches support the
RADIUS Change of Authorization (CoA) extensions defined in RFC 5176 that are typically used in a
pushed model and allow for the dynamic reconfiguring of sessions from external authentication,
authorization, and accounting (AAA) or policy servers.
Beginning with Cisco IOS Release 12.2(52)SE, the switch supports these per-session CoA requests:
•
Session reauthentication
•
Session termination
•
Session termination with port shutdown
•
Session termination with port bounce
This feature is integrated with the Cisco Secure Access Control Server (ACS) 5.1. For information about
ACS, refer to: http://www.cisco.com/en/US/products/sw/secursw/ps2086/index.html.
The RADIUS interface is enabled by default on Catalyst switches. However, some basic configuration
is required for the following attributes:
•
Security and Password—refer to the “Preventing Unauthorized Access to Your Switch” section in
the Configuring Switch-Based Authentication chapter in the Catalyst 3750 Switch Software
Configuration Guide, 12.2(50)SE.
•
Accounting—refer to the “Starting RADIUS Accounting” section in the Configuring Switch-Based
Authentication chapter in the Catalyst 3750 Switch Software Configuration Guide, 12.2(50)SE.
Change-of-Authorization Requests
Change of Authorization (CoA) requests, as described in RFC 5176, are used in a push model to allow
for session identification, host reauthentication, and session termination. The model is comprised of one
request (CoA-Request) and two possible response codes:
•
CoA acknowledgement (ACK) [CoA-ACK]
•
CoA non-acknowledgement (NAK) [CoA-NAK]
The request is initiated from a CoA client (typically a RADIUS or policy server) and directed to the
switch that acts as a listener.
This section includes these topics:
•
CoA Request Response Code
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•
CoA Request Commands
•
Session Reauthentication
RFC 5176 Compliance
The Disconnect Request message, which is also referred to as Packet of Disconnect (POD), is supported
by the switch for session termination.
Table 7-2 shows the IETF attributes are supported for this feature.
Table 7-2
Supported IETF Attributes
Attribute Number
Attribute Name
24
State
31
Calling-Station-ID
44
Acct-Session-ID
80
Message-Authenticator
101
Error-Cause
Table 7-3 shows the possible values for the Error-Cause attribute.
Table 7-3
Error-Cause Values
Value
Explanation
201
Residual Session Context Removed
202
Invalid EAP Packet (Ignored)
401
Unsupported Attribute
402
Missing Attribute
403
NAS Identification Mismatch
404
Invalid Request
405
Unsupported Service
406
Unsupported Extension
407
Invalid Attribute Value
501
Administratively Prohibited
502
Request Not Routable (Proxy)
503
Session Context Not Found
504
Session Context Not Removable
505
Other Proxy Processing Error
506
Resources Unavailable
507
Request Initiated
508
Multiple Session Selection Unsupported
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Preconditions
To use the CoA interface, a session must already exist on the switch. CoA can be used to identify a
session and enforce a disconnect request. The update affects only the specified session.
CoA Request Response Code
The CoA Request response code can be used to convey a command to the switch. The supported
commands are listed in Table 7-4 on page 7-23.
Session Identification
For disconnect and CoA requests targeted at a particular session, the switch locates the session based on
one or more of the following attributes:
•
Calling-Station-Id (IETF attribute #31 which contains the host MAC address)
•
Audit-Session-Id (Cisco VSA)
•
Acct-Session-Id (IETF attribute #44)
Unless all session identification attributes included in the CoA message match the session, the switch
returns a Disconnect-NAK or CoA-NAK with the “Invalid Attribute Value” error-code attribute.
For disconnect and CoA requests targeted to a particular session, any one of the following session
identifiers can be used:
•
Calling-Station-ID (IETF attribute #31, which should contain the MAC address)
•
Audit-Session-ID (Cisco vendor-specific attribute)
•
Accounting-Session-ID (IETF attribute #44).
If more than one session identification attribute is included in the message, all the attributes must match
the session or the switch returns a Disconnect- negative acknowledgement (NAK) or CoA-NAK with the
error code “Invalid Attribute Value.”
The packet format for a CoA Request code as defined in RFC 5176 consists of the fields: Code,
Identifier, Length, Authenticator, and Attributes in Type:Length:Value (TLV) format.
0
1
2
3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
Code
| Identifier
|
Length
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
|
|
Authenticator
|
|
|
|
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attributes ...
+-+-+-+-+-+-+-+-+-+-+-+-+-
The attributes field is used to carry Cisco VSAs.
CoA ACK Response Code
If the authorization state is changed successfully, a positive acknowledgement (ACK) is sent. The
attributes returned within CoA ACK will vary based on the CoA Request and are discussed in individual
CoA Commands.
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CoA NAK Response Code
A negative acknowledgement (NAK) indicates a failure to change the authorization state and can include
attributes that indicate the reason for the failure. Use show commands to verify a successful CoA.
CoA Request Commands
This section includes:
•
Session Reauthentication
•
Session Termination
•
CoA Disconnect-Request
•
CoA Request: Disable Host Port
•
CoA Request: Bounce-Port
Beginning with Cisco IOS Release 12.2(52)SE, the switch supports the commands shown in Table 7-4.
Table 7-4
CoA Commands Supported on the Switch
Command1
Cisco VSA
Reauthenticate host
Cisco:Avpair=“subscriber:command=reauthenticate”
Terminate session
This is a standard disconnect request that does not require a VSA.
Bounce host port
Cisco:Avpair=“subscriber:command=bounce-host-port”
Disable host port
Cisco:Avpair=“subscriber:command=disable-host-port”
1. All CoA commands must include the session identifier between the switch and the CoA client.
Session Reauthentication
The AAA server typically generates a session reauthentication request when a host with an unknown
identity or posture joins the network and is associated with a restricted access authorization profile (such
as a guest VLAN). A reauthentication request allows the host to be placed in the appropriate
authorization group when its credentials are known.
To initiate session authentication, the AAA server sends a standard CoA-Request message which
contains a Cisco vendor-specific attribute (VSA) in this form:
Cisco:Avpair=“subscriber:command=reauthenticate” and one or more session identification attributes.
The current session state determines the switch response to the message. If the session is currently
authenticated by IEEE 802.1x, the switch responds by sending an Extensible Authentication Protocol
over Lan (EAPoL)-RequestId message to the server.
If the session is currently authenticated by MAC authentication bypass (MAB), the switch sends an
access-request to the server, passing the same identity attributes used for the initial successful
authentication.
If session authentication is in progress when the switch receives the command, the switch terminates the
process, and restarts the authentication sequence, starting with the method configured to be attempted
first.
If the session is not yet authorized, or is authorized via guest VLAN, or critical VLAN, or similar
policies, the reauthentication message restarts the access control methods, beginning with the method
configured to be attempted first. The current authorization of the session is maintained until the
reauthentication leads to a different authorization result.
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Session Termination
There are three types of CoA requests that can trigger session termination. A CoA Disconnect-Request
terminates the session, without disabling the host port. This command causes re-initialization of the
authenticator state machine for the specified host, but does not restrict that host’s access to the network.
To restrict a host’s access to the network, use a CoA Request with the
Cisco:Avpair="subscriber:command=disable-host-port" VSA. This command is useful when a host is
known to be causing problems on the network, and you need to immediately block network access for
the host. When you want to restore network access on the port, re-enable it using a non-RADIUS
mechanism.
When a device with no supplicant, such as a printer, needs to acquire a new IP address (for example,
after a VLAN change), terminate the session on the host port with port-bounce (temporarily disable and
then re-enable the port).
CoA Disconnect-Request
This command is a standard Disconnect-Request. Because this command is session-oriented, it must be
accompanied by one or more of the session identification attributes described in the “Session
Identification” section on page 7-22. If the session cannot be located, the switch returns a
Disconnect-NAK message with the “Session Context Not Found” error-code attribute. If the session is
located, the switch terminates the session. After the session has been completely removed, the switch
returns a Disconnect-ACK.
If the switch fails-over to a standby switch before returning a Disconnect-ACK to the client, the process
is repeated on the new active switch when the request is re-sent from the client. If the session is not found
following re-sending, a Disconnect-ACK is sent with the “Session Context Not Found” error-code
attribute.
CoA Request: Disable Host Port
This command is carried in a standard CoA-Request message that has this new VSA:
Cisco:Avpair="subscriber:command=disable-host-port"
Because this command is session-oriented, it must be accompanied by one or more of the session
identification attributes described in the “Session Identification” section on page 7-22. If the session
cannot be located, the switch returns a CoA-NAK message with the “Session Context Not Found”
error-code attribute. If the session is located, the switch disables the hosting port and returns a CoA-ACK
message.
If the switch fails before returning a CoA-ACK to the client, the process is repeated on the new active
switch when the request is re-sent from the client. If the switch fails after returning a CoA-ACK message
to the client but before the operation has completed, the operation is restarted on the new active switch.
Note
A Disconnect-Request failure following command re-sending could be the result of either a successful
session termination before change-over (if the Disconnect-ACK was not sent) or a session termination
by other means (for example, a link failure) that occurred after the original command was issued and
before the standby switch became active.
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CoA Request: Bounce-Port
This command is carried in a standard CoA-Request message that contains the following new VSA:
Cisco:Avpair="subscriber:command=bounce-host-port"
Because this command is session-oriented, it must be accompanied by one or more of the session
identification attributes described in the “Session Identification” section on page 7-22. If the session
cannot be located, the switch returns a CoA-NAK message with the “Session Context Not Found”
error-code attribute. If the session is located, the switch disables the hosting port for a period of 10
seconds, re-enables it (port-bounce), and returns a CoA-ACK.
If the switch fails before returning a CoA-ACK to the client, the process is repeated on the new active
switch when the request is re-sent from the client. If the switch fails after returning a CoA-ACK message
to the client but before the operation has completed, the operation is re-started on the new active switch.
Configuring RADIUS
This section describes how to configure your switch to support RADIUS. At a minimum, you must
identify the host or hosts that run the RADIUS server software and define the method lists for RADIUS
authentication. You can optionally define method lists for RADIUS authorization and accounting.
A method list defines the sequence and methods to be used to authenticate, to authorize, or to keep
accounts on a user. You can use method lists to designate one or more security protocols to be used (such
as TACACS+ or local username lookup), thus ensuring a backup system if the initial method fails. The
software uses the first method listed to authenticate, to authorize, or to keep accounts on users; if that
method does not respond, the software selects the next method in the list. This process continues until
there is successful communication with a listed method or the method list is exhausted.
You should have access to and should configure a RADIUS server before configuring RADIUS features
on your switch.
These sections contain this configuration information:
•
Default RADIUS Configuration, page 7-26
•
Identifying the RADIUS Server Host, page 7-26 (required)
•
Configuring RADIUS Login Authentication, page 7-28 (required)
•
Defining AAA Server Groups, page 7-30 (optional)
•
Configuring RADIUS Authorization for User Privileged Access and Network Services, page 7-32
(optional)
•
Starting RADIUS Accounting, page 7-33 (optional)
•
Configuring Settings for All RADIUS Servers, page 7-34 (optional)
•
Configuring the Switch to Use Vendor-Specific RADIUS Attributes, page 7-34 (optional)
•
Configuring the Switch for Vendor-Proprietary RADIUS Server Communication, page 7-36
(optional)
•
Configuring CoA on the Switch, page 7-37
•
Monitoring and Troubleshooting CoA Functionality, page 7-38
•
Configuring RADIUS Server Load Balancing, page 7-38 (optional)
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Default RADIUS Configuration
RADIUS and AAA are disabled by default.
To prevent a lapse in security, you cannot configure RADIUS through a network management
application. When enabled, RADIUS can authenticate users accessing the switch through the CLI.
Identifying the RADIUS Server Host
Switch-to-RADIUS-server communication involves several components:
•
Hostname or IP address
•
Authentication destination port
•
Accounting destination port
•
Key string
•
Timeout period
•
Retransmission value
You identify RADIUS security servers by their hostname or IP address, hostname and specific UDP port
numbers, or their IP address and specific UDP port numbers. The combination of the IP address and the
UDP port number creates a unique identifier, allowing different ports to be individually defined as
RADIUS hosts providing a specific AAA service. This unique identifier enables RADIUS requests to be
sent to multiple UDP ports on a server at the same IP address.
If two different host entries on the same RADIUS server are configured for the same service—for
example, accounting—the second host entry configured acts as a fail-over backup to the first one. Using
this example, if the first host entry fails to provide accounting services, the %RADIUS-4-RADIUS_DEAD
message appears, and then the switch tries the second host entry configured on the same device for
accounting services. (The RADIUS host entries are tried in the order that they are configured.)
A RADIUS server and the switch use a shared secret text string to encrypt passwords and exchange
responses. To configure RADIUS to use the AAA security commands, you must specify the host running
the RADIUS server daemon and a secret text (key) string that it shares with the switch.
The timeout, retransmission, and encryption key values can be configured globally for all RADIUS
servers, on a per-server basis, or in some combination of global and per-server settings. To apply these
settings globally to all RADIUS servers communicating with the switch, use the three unique global
configuration commands: radius-server timeout, radius-server retransmit, and radius-server key. To
apply these values on a specific RADIUS server, use the radius-server host global configuration
command.
Note
If you configure both global and per-server functions (timeout, retransmission, and key commands) on
the switch, the per-server timer, retransmission, and key value commands override global timer,
retransmission, and key value commands. For information on configuring these settings on all RADIUS
servers, see the “Configuring Settings for All RADIUS Servers” section on page 7-34.
You can configure the switch to use AAA server groups to group existing server hosts for authentication.
For more information, see the “Defining AAA Server Groups” section on page 7-30.
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Beginning in privileged EXEC mode, follow these steps to configure per-server RADIUS server
communication. This procedure is required.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
radius-server host {hostname |
ip-address} [auth-port port-number]
[acct-port port-number] [timeout
seconds] [retransmit retries] [key
string]
Specify the IP address or hostname of the remote RADIUS server host.
•
(Optional) For auth-port port-number, specify the UDP destination
port for authentication requests.
•
(Optional) For acct-port port-number, specify the UDP destination
port for accounting requests.
•
(Optional) For timeout seconds, specify the time interval that the
switch waits for the RADIUS server to reply before resending. The
range is 1 to 1000. This setting overrides the radius-server timeout
global configuration command setting. If no timeout is set with the
radius-server host command, the setting of the radius-server
timeout command is used.
•
(Optional) For retransmit retries, specify the number of times a
RADIUS request is resent to a server if that server is not responding
or responding slowly. The range is 1 to 1000. If no retransmit value is
set with the radius-server host command, the setting of the
radius-server retransmit global configuration command is used.
•
(Optional) For key string, specify the authentication and encryption
key used between the switch and the RADIUS daemon running on the
RADIUS server.
Note
The key is a text string that must match the encryption key used
on the RADIUS server. Always configure the key as the last item
in the radius-server host command. Leading spaces are ignored,
but spaces within and at the end of the key are used. If you use
spaces in your key, do not enclose the key in quotation marks
unless the quotation marks are part of the key.
To configure the switch to recognize more than one host entry associated
with a single IP address, enter this command as many times as necessary,
making sure that each UDP port number is different. The switch software
searches for hosts in the order in which you specify them. Set the timeout,
retransmit, and encryption key values to use with the specific RADIUS
host.
Step 3
end
Return to privileged EXEC mode.
Step 4
show running-config
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To remove the specified RADIUS server, use the no radius-server host hostname | ip-address global
configuration command.
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This example shows how to configure one RADIUS server to be used for authentication and another to
be used for accounting:
Switch(config)# radius-server host 172.29.36.49 auth-port 6403 key rad1
Switch(config)# radius-server host 172.20.36.50 acct-port 6403 key rad2
This example shows how to configure host1 as the RADIUS server and to use the default ports for both
authentication and accounting:
Switch(config)# radius-server host host1
Note
You also need to configure some settings on the RADIUS server. These settings include the IP address
of the switch and the key string to be shared by both the server and the switch. For more information,
see the RADIUS server documentation.
Configuring RADIUS Login Authentication
To configure AAA authentication, you define a named list of authentication methods and then apply that
list to various ports. The method list defines the types of authentication to be performed and the sequence
in which they are performed; it must be applied to a specific port before any of the defined authentication
methods are performed. The only exception is the default method list (which, by coincidence, is named
default). The default method list is automatically applied to all ports except those that have a named
method list explicitly defined.
A method list describes the sequence and authentication methods to be queried to authenticate a user.
You can designate one or more security protocols to be used for authentication, thus ensuring a backup
system for authentication in case the initial method fails. The software uses the first method listed to
authenticate users; if that method fails to respond, the software selects the next authentication method in
the method list. This process continues until there is successful communication with a listed
authentication method or until all defined methods are exhausted. If authentication fails at any point in
this cycle—meaning that the security server or local username database responds by denying the user
access—the authentication process stops, and no other authentication methods are attempted.
Beginning in privileged EXEC mode, follow these steps to configure login authentication. This
procedure is required.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
aaa new-model
Enable AAA.
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Step 3
Command
Purpose
aaa authentication login {default |
list-name} method1 [method2...]
Create a login authentication method list.
•
To create a default list that is used when a named list is not specified
in the login authentication command, use the default keyword
followed by the methods that are to be used in default situations. The
default method list is automatically applied to all ports.
•
For list-name, specify a character string to name the list you are
creating.
•
For method1..., specify the actual method the authentication
algorithm tries. The additional methods of authentication are used
only if the previous method returns an error, not if it fails.
Select one of these methods:
– enable—Use the enable password for authentication. Before you
can use this authentication method, you must define an enable
password by using the enable password global configuration
command.
– group radius—Use RADIUS authentication. Before you can use
this authentication method, you must configure the RADIUS
server. For more information, see the “Identifying the RADIUS
Server Host” section on page 7-26.
– line—Use the line password for authentication. Before you can
use this authentication method, you must define a line password.
Use the password password line configuration command.
– local—Use the local username database for authentication. You
must enter username information in the database. Use the
username name password global configuration command.
– local-case—Use a case-sensitive local username database for
authentication. You must enter username information in the
database by using the username password global configuration
command.
– none—Do not use any authentication for login.
Step 4
line [console | tty | vty] line-number
[ending-line-number]
Enter line configuration mode, and configure the lines to which you want
to apply the authentication list.
Step 5
login authentication {default |
list-name}
Apply the authentication list to a line or set of lines.
•
If you specify default, use the default list created with the aaa
authentication login command.
•
For list-name, specify the list created with the aaa authentication
login command.
Step 6
end
Return to privileged EXEC mode.
Step 7
show running-config
Verify your entries.
Step 8
copy running-config startup-config
(Optional) Save your entries in the configuration file.
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To disable AAA, use the no aaa new-model global configuration command. To disable AAA
authentication, use the no aaa authentication login {default | list-name} method1 [method2...] global
configuration command. To either disable RADIUS authentication for logins or to return to the default
value, use the no login authentication {default | list-name} line configuration command.
Note
To secure the switch for HTTP access by using AAA methods, you must configure the switch with the
ip http authentication aaa global configuration command. Configuring AAA authentication does not
secure the switch for HTTP access by using AAA methods.
For more information about the ip http authentication command, see the Cisco IOS Security Command
Reference, Release 12.2 from the Cisco.com page under Documentation > Cisco IOS Software > 12.2
Mainline > Command References.
Defining AAA Server Groups
You can configure the switch to use AAA server groups to group existing server hosts for authentication.
You select a subset of the configured server hosts and use them for a particular service. The server group
is used with a global server-host list, which lists the IP addresses of the selected server hosts.
Server groups also can include multiple host entries for the same server if each entry has a unique
identifier (the combination of the IP address and UDP port number), allowing different ports to be
individually defined as RADIUS hosts providing a specific AAA service. If you configure two different
host entries on the same RADIUS server for the same service, (for example, accounting), the second
configured host entry acts as a fail-over backup to the first one.
You use the server group server configuration command to associate a particular server with a defined
group server. You can either identify the server by its IP address or identify multiple host instances or
entries by using the optional auth-port and acct-port keywords.
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Controlling Switch Access with RADIUS
Beginning in privileged EXEC mode, follow these steps to define the AAA server group and associate a
particular RADIUS server with it:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
radius-server host {hostname |
ip-address} [auth-port port-number]
[acct-port port-number] [timeout
seconds] [retransmit retries] [key
string]
Specify the IP address or hostname of the remote RADIUS server host.
•
(Optional) For auth-port port-number, specify the UDP destination
port for authentication requests.
•
(Optional) For acct-port port-number, specify the UDP destination
port for accounting requests.
•
(Optional) For timeout seconds, specify the time interval that the
switch waits for the RADIUS server to reply before resending. The
range is 1 to 1000. This setting overrides the radius-server timeout
global configuration command setting. If no timeout is set with the
radius-server host command, the setting of the radius-server
timeout command is used.
•
(Optional) For retransmit retries, specify the number of times a
RADIUS request is resent to a server if that server is not responding
or responding slowly. The range is 1 to 1000. If no retransmit value is
set with the radius-server host command, the setting of the
radius-server retransmit global configuration command is used.
•
(Optional) For key string, specify the authentication and encryption
key used between the switch and the RADIUS daemon running on the
RADIUS server.
Note
The key is a text string that must match the encryption key used
on the RADIUS server. Always configure the key as the last item
in the radius-server host command. Leading spaces are ignored,
but spaces within and at the end of the key are used. If you use
spaces in your key, do not enclose the key in quotation marks
unless the quotation marks are part of the key.
To configure the switch to recognize more than one host entry associated
with a single IP address, enter this command as many times as necessary,
making sure that each UDP port number is different. The switch software
searches for hosts in the order in which you specify them. Set the timeout,
retransmit, and encryption key values to use with the specific RADIUS
host.
Step 3
aaa new-model
Enable AAA.
Step 4
aaa group server radius group-name
Define the AAA server-group with a group name.
This command puts the switch in a server group configuration mode.
Step 5
server ip-address
Associate a particular RADIUS server with the defined server group.
Repeat this step for each RADIUS server in the AAA server group.
Each server in the group must be previously defined in Step 2.
Step 6
end
Return to privileged EXEC mode.
Step 7
show running-config
Verify your entries.
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Step 8
Command
Purpose
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Step 9
Enable RADIUS login authentication. See the “Configuring RADIUS
Login Authentication” section on page 7-28.
To remove the specified RADIUS server, use the no radius-server host hostname | ip-address global
configuration command. To remove a server group from the configuration list, use the no aaa group
server radius group-name global configuration command. To remove the IP address of a RADIUS
server, use the no server ip-address server group configuration command.
In this example, the switch is configured to recognize two different RADIUS group servers (group1 and
group2). Group1 has two different host entries on the same RADIUS server configured for the same
services. The second host entry acts as a fail-over backup to the first entry.
Switch(config)# radius-server host 172.20.0.1 auth-port 1000 acct-port 1001
Switch(config)# radius-server host 172.10.0.1 auth-port 1645 acct-port 1646
Switch(config)# aaa new-model
Switch(config)# aaa group server radius group1
Switch(config-sg-radius)# server 172.20.0.1 auth-port 1000 acct-port 1001
Switch(config-sg-radius)# exit
Switch(config)# aaa group server radius group2
Switch(config-sg-radius)# server 172.20.0.1 auth-port 2000 acct-port 2001
Switch(config-sg-radius)# exit
Configuring RADIUS Authorization for User Privileged Access and Network Services
AAA authorization limits the services available to a user. When AAA authorization is enabled, the
switch uses information retrieved from the user’s profile, which is in the local user database or on the
security server, to configure the user’s session. The user is granted access to a requested service only if
the information in the user profile allows it.
You can use the aaa authorization global configuration command with the radius keyword to set
parameters that restrict a user’s network access to privileged EXEC mode.
The aaa authorization exec radius local command sets these authorization parameters:
Note
•
Use RADIUS for privileged EXEC access authorization if authentication was performed by using
RADIUS.
•
Use the local database if authentication was not performed by using RADIUS.
Authorization is bypassed for authenticated users who log in through the CLI even if authorization has
been configured.
Beginning in privileged EXEC mode, follow these steps to specify RADIUS authorization for privileged
EXEC access and network services:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
aaa authorization network radius
Configure the switch for user RADIUS authorization for all
network-related service requests.
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Step 3
Command
Purpose
aaa authorization exec radius
Configure the switch for user RADIUS authorization if the user has
privileged EXEC access.
The exec keyword might return user profile information (such as
autocommand information).
Step 4
end
Return to privileged EXEC mode.
Step 5
show running-config
Verify your entries.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To disable authorization, use the no aaa authorization {network | exec} method1 global configuration
command.
Starting RADIUS Accounting
The AAA accounting feature tracks the services that users are accessing and the amount of network
resources that they are consuming. When AAA accounting is enabled, the switch reports user activity to
the RADIUS security server in the form of accounting records. Each accounting record contains
accounting attribute-value (AV) pairs and is stored on the security server. This data can then be analyzed
for network management, client billing, or auditing.
Beginning in privileged EXEC mode, follow these steps to enable RADIUS accounting for each Cisco
IOS privilege level and for network services:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
aaa accounting network start-stop
radius
Enable RADIUS accounting for all network-related service requests.
Step 3
aaa accounting exec start-stop radius
Enable RADIUS accounting to send a start-record accounting notice at
the beginning of a privileged EXEC process and a stop-record at the end.
Step 4
end
Return to privileged EXEC mode.
Step 5
show running-config
Verify your entries.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To disable accounting, use the no aaa accounting {network | exec} {start-stop} method1... global
configuration command.
Establishing a Session with a Router if the AAA Server is Unreachable
The aaa accounting system guarantee-first command guarantees system accounting as the first record,
which is the default condition. In some situations, users might be prevented from starting a session on
the console or terminal connection until after the system reloads, which can take more than 3 minutes.
To establish a console or Telnet session with the router if the AAA server is unreachable when the router
reloads, use the no aaa accounting system guarantee-first command.
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Controlling Switch Access with RADIUS
Configuring Settings for All RADIUS Servers
Beginning in privileged EXEC mode, follow these steps to configure global communication settings
between the switch and all RADIUS servers:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
radius-server key string
Specify the shared secret text string used between the switch and all
RADIUS servers.
Note
The key is a text string that must match the encryption key used on
the RADIUS server. Leading spaces are ignored, but spaces within
and at the end of the key are used. If you use spaces in your key, do
not enclose the key in quotation marks unless the quotation marks
are part of the key.
Step 3
radius-server retransmit retries
Specify the number of times the switch sends each RADIUS request to the
server before giving up. The default is 3; the range 1 to 1000.
Step 4
radius-server timeout seconds
Specify the number of seconds a switch waits for a reply to a RADIUS
request before resending the request. The default is 5 seconds; the range is
1 to 1000.
Step 5
radius-server deadtime minutes
Specify the number of minutes a RADIUS server, which is not responding
to authentication requests, to be skipped, thus avoiding the wait for the
request to timeout before trying the next configured server. The default is
0; the range is 1 to 1440 minutes.
Step 6
end
Return to privileged EXEC mode.
Step 7
show running-config
Verify your settings.
Step 8
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To return to the default setting for the retransmit, timeout, and deadtime, use the no forms of these
commands.
Configuring the Switch to Use Vendor-Specific RADIUS Attributes
The Internet Engineering Task Force (IETF) draft standard specifies a method for communicating
vendor-specific information between the switch and the RADIUS server by using the vendor-specific
attribute (attribute 26). Vendor-specific attributes (VSAs) allow vendors to support their own extended
attributes not suitable for general use. The Cisco RADIUS implementation supports one vendor-specific
option by using the format recommended in the specification. Cisco’s vendor-ID is 9, and the supported
option has vendor-type 1, which is named cisco-avpair. The value is a string with this format:
protocol : attribute sep value *
Protocol is a value of the Cisco protocol attribute for a particular type of authorization. Attribute and
value are an appropriate attribute-value (AV) pair defined in the Cisco TACACS+ specification, and sep
is = for mandatory attributes and is * for optional attributes. The full set of features available for
TACACS+ authorization can then be used for RADIUS.
For example, this AV pair activates Cisco’s multiple named ip address pools feature during IP
authorization (during PPP IPCP address assignment):
cisco-avpair= ”ip:addr-pool=first“
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This example shows how to provide a user logging in from a switch with immediate access to privileged
EXEC commands:
cisco-avpair= ”shell:priv-lvl=15“
This example shows how to specify an authorized VLAN in the RADIUS server database:
cisco-avpair= ”tunnel-type(#64)=VLAN(13)”
cisco-avpair= ”tunnel-medium-type(#65)=802 media(6)”
cisco-avpair= ”tunnel-private-group-id(#81)=vlanid”
This example shows how to apply an input ACL in ASCII format to an interface for the duration of this
connection:
cisco-avpair= “ip:inacl#1=deny ip 10.10.10.10 0.0.255.255 20.20.20.20 255.255.0.0”
cisco-avpair= “ip:inacl#2=deny ip 10.10.10.10 0.0.255.255 any”
cisco-avpair= “mac:inacl#3=deny any any decnet-iv”
This example shows how to apply an output ACL in ASCII format to an interface for the duration of this
connection:
cisco-avpair= “ip:outacl#2=deny ip 10.10.10.10 0.0.255.255 any”
Other vendors have their own unique vendor-IDs, options, and associated VSAs. For more information
about vendor-IDs and VSAs, see RFC 2138, “Remote Authentication Dial-In User Service (RADIUS).”
Beginning in privileged EXEC mode, follow these steps to configure the switch to recognize and use
VSAs:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
radius-server vsa send [accounting |
authentication]
Enable the switch to recognize and use VSAs as defined by RADIUS IETF
attribute 26.
•
(Optional) Use the accounting keyword to limit the set of recognized
vendor-specific attributes to only accounting attributes.
•
(Optional) Use the authentication keyword to limit the set of
recognized vendor-specific attributes to only authentication attributes.
If you enter this command without keywords, both accounting and
authentication vendor-specific attributes are used.
Step 3
end
Return to privileged EXEC mode.
Step 4
show running-config
Verify your settings.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
For a complete list of RADIUS attributes or more information about vendor-specific attribute 26, see the
“RADIUS Attributes” appendix in the Cisco IOS Security Configuration Guide, Release 12.2 from the
Cisco.com page under Documentation > Cisco IOS Software > 12.2 Mainline > Command
References.
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Controlling Switch Access with RADIUS
Configuring the Switch for Vendor-Proprietary RADIUS Server Communication
Although an IETF draft standard for RADIUS specifies a method for communicating vendor-proprietary
information between the switch and the RADIUS server, some vendors have extended the RADIUS
attribute set in a unique way. Cisco IOS software supports a subset of vendor-proprietary RADIUS
attributes.
As mentioned earlier, to configure RADIUS (whether vendor-proprietary or IETF draft-compliant), you
must specify the host running the RADIUS server daemon and the secret text string it shares with the
switch. You specify the RADIUS host and secret text string by using the radius-server global
configuration commands.
Beginning in privileged EXEC mode, follow these steps to specify a vendor-proprietary RADIUS server
host and a shared secret text string:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
radius-server host {hostname | ip-address} non-standard
Specify the IP address or hostname of the remote
RADIUS server host and identify that it is using a
vendor-proprietary implementation of RADIUS.
Step 3
radius-server key string
Specify the shared secret text string used between the
switch and the vendor-proprietary RADIUS server.
The switch and the RADIUS server use this text
string to encrypt passwords and exchange responses.
Note
The key is a text string that must match the
encryption key used on the RADIUS server.
Leading spaces are ignored, but spaces within
and at the end of the key are used. If you use
spaces in your key, do not enclose the key in
quotation marks unless the quotation marks
are part of the key.
Step 4
end
Return to privileged EXEC mode.
Step 5
show running-config
Verify your settings.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To delete the vendor-proprietary RADIUS host, use the no radius-server host {hostname | ip-address}
non-standard global configuration command. To disable the key, use the no radius-server key global
configuration command.
This example shows how to specify a vendor-proprietary RADIUS host and to use a secret key of rad124
between the switch and the server:
Switch(config)# radius-server host 172.20.30.15 nonstandard
Switch(config)# radius-server key rad124
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Controlling Switch Access with RADIUS
Configuring CoA on the Switch
Beginning in privileged EXEC mode, follow these steps to configure CoA on a switch. This procedure
is required.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
aaa new-model
Enable AAA.
Step 3
aaa server radius dynamic-author
Configure the switch as an authentication, authorization, and accounting
(AAA) server to facilitate interaction with an external policy server.
Step 4
client {ip-address | name} [vrf vrfname] Enter dynamic authorization local server configuration mode and specify
[server-key string]
a RADIUS client from which a device will accept CoA and disconnect
requests.
Step 5
server-key [0 | 7] string
Configure the RADIUS key to be shared between a device and RADIUS
clients.
Step 6
port port-number
Specify the port on which a device listens for RADIUS requests from
configured RADIUS clients.
Step 7
auth-type {any | all | session-key}
Specify the type of authorization the switch uses for RADIUS clients.
The client must match all the configured attributes for authorization.
Step 8
ignore session-key
(Optional) Configure the switch to ignore the session-key.
For more information about the ignore command, see the Cisco IOS
Intelligent Services Gateway Command Reference on Cisco.com.
Step 9
ignore server-key
(Optional) Configure the switch to ignore the server-key.
For more information about the ignore command, see the Cisco IOS
Intelligent Services Gateway Command Reference on Cisco.com.
Step 10
authentication command bounce-port (Optional) Configure the switch to ignore a CoA request to temporarily
ignore
disable the port hosting a session. The purpose of temporarily disabling
the port is to trigger a DHCP renegotiation from the host when a VLAN
change occurs and there is no supplicant on the endpoint to detect the
change.
Step 11
authentication command disable-port (Optional) Configure the switch to ignore a nonstandard command
ignore
requesting that the port hosting a session be administratively shut down.
Shutting down the port results in termination of the session.
Use standard CLI or SNMP commands to re-enable the port.
Step 12
end
Return to privileged EXEC mode.
Step 13
show running-config
Verify your entries.
Step 14
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To disable AAA, use the no aaa new-model global configuration command. To disable the AAA server
functionality on the switch, use the no aaa server radius dynamic authorization global configuration
command.
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Controlling Switch Access with Kerberos
Monitoring and Troubleshooting CoA Functionality
The following Cisco IOS commands can be used to monitor and troubleshoot CoA functionality on the
switch:
•
debug radius
•
debug aaa coa
•
debug aaa pod
•
debug aaa subsys
•
debug cmdhd [detail | error | events]
•
show aaa attributes protocol radius
Configuring RADIUS Server Load Balancing
This feature allows access and authentication requests to be evenly across all RADIUS servers in a server
group. For more information, see the “RADIUS Server Load Balancing” chapter of the “Cisco IOS
Security Configuration Guide”, Release 12.2:
http://www.ciscosystems.com/en/US/docs/ios/12_2sb/feature/guide/sbrdldbl.html
Displaying the RADIUS Configuration
To display the RADIUS configuration, use the show running-config privileged EXEC command.
Controlling Switch Access with Kerberos
This section describes how to enable and configure the Kerberos security system, which authenticates
requests for network resources by using a trusted third party. To use this feature, the cryptographic (that
is, supports encryption) versions of the switch software must be installed on your switch.
You must obtain authorization to use this feature and to download the cryptographic software files from
Cisco.com. For more information, see the release notes for this release.
•
Understanding Kerberos, page 7-39
•
Kerberos Operation, page 7-41
•
Configuring Kerberos, page 7-42
For Kerberos configuration examples, see the “Kerberos Configuration Examples” section in the
“Security Server Protocols” chapter of the Cisco IOS Security Configuration Guide, Release 12.2, at this
URL:
http://www.cisco.com/en/US/docs/ios/12_2/security/configuration/guide/fsecur_c.html
For complete syntax and usage information for the commands used in this section, see the “Kerberos
Commands” section in the “Security Server Protocols” chapter of the Cisco IOS Security Command
Reference, Release 12.2, at this URL:
http://www.cisco.com/en/US/docs/ios/12_2/security/command/reference/fsecur_r.html
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Note
In the Kerberos configuration examples and in the Cisco IOS Security Command Reference,
Release 12.2, the trusted third party can be a switch that supports Kerberos, that is configured as a
network security server, and that can authenticate users by using the Kerberos protocol.
Understanding Kerberos
Kerberos is a secret-key network authentication protocol, which was developed at the Massachusetts
Institute of Technology (MIT). It uses the Data Encryption Standard (DES) cryptographic algorithm for
encryption and authentication and authenticates requests for network resources. Kerberos uses the
concept of a trusted third party to perform secure verification of users and services. This trusted third
party is called the key distribution center (KDC).
Kerberos verifies that users are who they claim to be and the network services that they use are what the
services claim to be. To do this, a KDC or trusted Kerberos server issues tickets to users. These tickets,
which have a limited lifespan, are stored in user credential caches. The Kerberos server uses the tickets
instead of usernames and passwords to authenticate users and network services.
Note
A Kerberos server can be a switch that is configured as a network security server and that can
authenticate users by using the Kerberos protocol.
The Kerberos credential scheme uses a process called single logon. This process authenticates a user
once and then allows secure authentication (without encrypting another password) wherever that user
credential is accepted.
This software release supports Kerberos 5, which allows organizations that are already using Kerberos 5
to use the same Kerberos authentication database on the KDC that they are already using on their other
network hosts (such as UNIX servers and PCs).
In this software release, Kerberos supports these network services:
•
Telnet
•
rlogin
•
rsh (Remote Shell Protocol)
Table 7-5 lists the common Kerberos-related terms and definitions:
Table 7-5
Kerberos Terms
Term
Definition
Authentication
A process by which a user or service identifies itself to another service. For example, a client
can authenticate to a switch or a switch can authenticate to another switch.
Authorization
A means by which the switch identifies what privileges the user has in a network or on the
switch and what actions the user can perform.
Credential
A general term that refers to authentication tickets, such as TGTs1 and service credentials.
Kerberos credentials verify the identity of a user or service. If a network service decides to trust
the Kerberos server that issued a ticket, it can be used in place of re-entering a username and
password. Credentials have a default lifespan of eight hours.
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Table 7-5
Kerberos Terms (continued)
Term
Definition
Instance
An authorization level label for Kerberos principals. Most Kerberos principals are of the form
user@REALM (for example, [email protected]). A Kerberos principal with a Kerberos
instance has the form user/instance@REALM (for example, smith/[email protected]).
The Kerberos instance can be used to specify the authorization level for the user if
authentication is successful. The server of each network service might implement and enforce the
authorization mappings of Kerberos instances but is not required to do so.
Note
The Kerberos principal and instance names must be in all lowercase characters.The
Kerberos realm name must be in all uppercase characters.
KDC2
Key distribution center that consists of a Kerberos server and database program that is running
on a network host.
Kerberized
A term that describes applications and services that have been modified to support the Kerberos
credential infrastructure.
Kerberos realm
A domain consisting of users, hosts, and network services that are registered to a Kerberos
server. The Kerberos server is trusted to verify the identity of a user or network service to
another user or network service.
Note
The Kerberos realm name must be in all uppercase characters.
Kerberos server
A daemon that is running on a network host. Users and network services register their identity
with the Kerberos server. Network services query the Kerberos server to authenticate to other
network services.
KEYTAB3
A password that a network service shares with the KDC. In Kerberos 5 and later Kerberos
versions, the network service authenticates an encrypted service credential by using the
KEYTAB to decrypt it. In Kerberos versions earlier than Kerberos 5, KEYTAB is referred to as
SRVTAB4.
Principal
Also known as a Kerberos identity, this is who you are or what a service is according to the
Kerberos server.
Note
The Kerberos principal name must be in all lowercase characters.
Service credential
A credential for a network service. When issued from the KDC, this credential is encrypted with
the password shared by the network service and the KDC. The password is also shared with the
user TGT.
SRVTAB
A password that a network service shares with the KDC. In Kerberos 5 or later Kerberos
versions, SRVTAB is referred to as KEYTAB.
TGT
Ticket granting ticket that is a credential that the KDC issues to authenticated users. When users
receive a TGT, they can authenticate to network services within the Kerberos realm represented
by the KDC.
1. TGT = ticket granting ticket
2. KDC = key distribution center
3. KEYTAB = key table
4. SRVTAB = server table
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Kerberos Operation
A Kerberos server can be a switch that is configured as a network security server and that can
authenticate remote users by using the Kerberos protocol. Although you can customize Kerberos in a
number of ways, remote users attempting to access network services must pass through three layers of
security before they can access network services.
To authenticate to network services by using a switch as a Kerberos server, remote users must follow
these steps:
1.
Authenticating to a Boundary Switch, page 7-41
2.
Obtaining a TGT from a KDC, page 7-41
3.
Authenticating to Network Services, page 7-42
Authenticating to a Boundary Switch
This section describes the first layer of security through which a remote user must pass. The user must
first authenticate to the boundary switch. This process then occurs:
1.
The user opens an un-Kerberized Telnet connection to the boundary switch.
2.
The switch prompts the user for a username and password.
3.
The switch requests a TGT from the KDC for this user.
4.
The KDC sends an encrypted TGT that includes the user identity to the switch.
5.
The switch attempts to decrypt the TGT by using the password that the user entered.
•
If the decryption is successful, the user is authenticated to the switch.
•
If the decryption is not successful, the user repeats Step 2 either by re-entering the username
and password (noting if Caps Lock or Num Lock is on or off) or by entering a different username
and password.
A remote user who initiates a un-Kerberized Telnet session and authenticates to a boundary switch is
inside the firewall, but the user must still authenticate directly to the KDC before getting access to the
network services. The user must authenticate to the KDC because the TGT that the KDC issues is stored
on the switch and cannot be used for additional authentication until the user logs on to the switch.
Obtaining a TGT from a KDC
This section describes the second layer of security through which a remote user must pass. The user must
now authenticate to a KDC and obtain a TGT from the KDC to access network services.
For instructions about how to authenticate to a KDC, see the “Obtaining a TGT from a KDC” section in
the “Security Server Protocols” chapter of the Cisco IOS Security Configuration Guide, Release 12.2, at
this URL:
http://www.cisco.com/en/US/docs/ios/12_2/security/configuration/guide/scfkerb.html
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Configuring Switch-Based Authentication
Configuring the Switch for Local Authentication and Authorization
Authenticating to Network Services
This section describes the third layer of security through which a remote user must pass. The user with
a TGT must now authenticate to the network services in a Kerberos realm.
For instructions about how to authenticate to a network service, see the “Authenticating to Network
Services” section in the “Security Server Protocols” chapter of the Cisco IOS Security Configuration
Guide, Release 12.2, at this URL:
http://www.cisco.com/en/US/docs/ios/12_2/security/configuration/guide/scfkerb.html
Configuring Kerberos
So that remote users can authenticate to network services, you must configure the hosts and the KDC in
the Kerberos realm to communicate and mutually authenticate users and network services. To do this,
you must identify them to each other. You add entries for the hosts to the Kerberos database on the KDC
and add KEYTAB files generated by the KDC to all hosts in the Kerberos realm. You also create entries
for the users in the KDC database.
When you add or create entries for the hosts and users, follow these guidelines:
Note
•
The Kerberos principal name must be in all lowercase characters.
•
The Kerberos instance name must be in all lowercase characters.
•
The Kerberos realm name must be in all uppercase characters.
A Kerberos server can be a switch that is configured as a network security server and that can
authenticate users by using the Kerberos protocol.
To set up a Kerberos-authenticated server-client system, follow these steps:
•
Configure the KDC by using Kerberos commands.
•
Configure the switch to use the Kerberos protocol.
For instructions, see the “Kerberos Configuration Task List” section in the “Security Server Protocols”
chapter of the Cisco IOS Security Configuration Guide, Release 12.2, at this URL:
http://www.cisco.com/en/US/docs/ios/12_2/security/configuration/guide/scfkerb.html
Configuring the Switch for Local Authentication and
Authorization
You can configure AAA to operate without a server by setting the switch to implement AAA in local
mode. The switch then handles authentication and authorization. No accounting is available in this
configuration.
Beginning in privileged EXEC mode, follow these steps to configure the switch for local AAA:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
aaa new-model
Enable AAA.
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Command
Purpose
Step 3
aaa authentication login default local
Set the login authentication to use the local username database. The
default keyword applies the local user database authentication to all
ports.
Step 4
aaa authorization exec local
Configure user AAA authorization, check the local database, and allow
the user to run an EXEC shell.
Step 5
aaa authorization network local
Configure user AAA authorization for all network-related service
requests.
Step 6
username name [privilege level]
{password encryption-type password}
Enter the local database, and establish a username-based authentication
system.
Repeat this command for each user.
•
For name, specify the user ID as one word. Spaces and quotation
marks are not allowed.
•
(Optional) For level, specify the privilege level the user has after
gaining access. The range is 0 to 15. Level 15 gives privileged EXEC
mode access. Level 0 gives user EXEC mode access.
•
For encryption-type, enter 0 to specify that an unencrypted password
follows. Enter 7 to specify that a hidden password follows.
•
For password, specify the password the user must enter to gain access
to the switch. The password must be from 1 to 25 characters, can
contain embedded spaces, and must be the last option specified in the
username command.
Step 7
end
Return to privileged EXEC mode.
Step 8
show running-config
Verify your entries.
Step 9
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To disable AAA, use the no aaa new-model global configuration command. To disable authorization,
use the no aaa authorization {network | exec} method1 global configuration command.
Note
To secure the switch for HTTP access by using AAA methods, you must configure the switch with the
ip http authentication aaa global configuration command. Configuring AAA authentication does not
secure the switch for HTTP access by using AAA methods.
For more information about the ip http authentication command, see the Cisco IOS Security Command
Reference, Release 12.2.
Configuring the Switch for Secure Shell
This section describes how to configure the Secure Shell (SSH) feature. To use this feature, the
cryptographic (that is, supports encryption) versions of the switch software must be installed on your
switch. You must obtain authorization to use this feature and to download the cryptographic software
files from Cisco.com. For more information, see the release notes for this release.
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Configuring the Switch for Secure Shell
SSH in IPv6 functions the same and offers the same benefits as SSH in IPv4. IPv6 enhancements to SSH
consist of support for IPv6 addresses that enable a Cisco router to accept and establish secure, encrypted
connections with remote IPv6 nodes over an IPv6 transport.
These sections contain this information:
•
Understanding SSH, page 7-44
•
Configuring SSH, page 7-45
•
Displaying the SSH Configuration and Status, page 7-48
For SSH configuration examples, see the “SSH Configuration Examples” section in the “Configuring
Secure Shell” chapter of the Cisco IOS Security Configuration Guide, Cisco IOS Release 12.2, at
this URL:
http://www.cisco.com/en/US/docs/ios/12_2/security/configuration/guide/scfssh.html
Note
For complete syntax and usage information for the commands used in this section, see the command
reference for this release and the command reference for Cisco IOS Release 12.2 at this URL:
http://www.cisco.com/en/US/docs/ios/12_2/security/command/reference/fsecur_r.html
Understanding SSH
SSH is a protocol that provides a secure, remote connection to a device. SSH provides more security for
remote connections than Telnet does by providing strong encryption when a device is authenticated. This
software release supports SSH Version 1 (SSHv1) and SSH Version 2 (SSHv2).
This section consists of these topics:
•
SSH Servers, Integrated Clients, and Supported Versions, page 7-44
•
Limitations, page 7-45
SSH Servers, Integrated Clients, and Supported Versions
The SSH feature has an SSH server and an SSH integrated client, which are applications that run on the
switch. You can use an SSH client to connect to a switch running the SSH server. The SSH server works
with the SSH client supported in this release and with non-Cisco SSH clients. The SSH client also works
with the SSH server supported in this release and with non-Cisco SSH servers.
The switch supports an SSHv1 or an SSHv2 server.
The switch supports an SSHv1 client.
SSH supports the Data Encryption Standard (DES) encryption algorithm, the Triple DES (3DES)
encryption algorithm, and password-based user authentication.
SSH also supports these user authentication methods:
•
TACACS+ (for more information, see the “Controlling Switch Access with TACACS+” section on
page 7-10)
•
RADIUS (for more information, see the “Controlling Switch Access with RADIUS” section on
page 7-17)
•
Local authentication and authorization (for more information, see the “Configuring the Switch for
Local Authentication and Authorization” section on page 7-42)
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Note
This software release does not support IP Security (IPSec).
Limitations
These limitations apply to SSH:
•
The switch supports Rivest, Shamir, and Adelman (RSA) authentication.
•
SSH supports only the execution-shell application.
•
The SSH server and the SSH client are supported only on DES (56-bit) and 3DES (168-bit) data
encryption software.
•
The switch supports the Advanced Encryption Standard (AES) encryption algorithm with a 128-bit
key, 192-bit key, or 256-bit key. However, symmetric cipher AES to encrypt the keys is not
supported.
Configuring SSH
This section has this configuration information:
•
Configuration Guidelines, page 7-45
•
Setting Up the Switch to Run SSH, page 7-46 (required)
•
Configuring the SSH Server, page 7-47 (required only if you are configuring the switch as an SSH
server)
Configuration Guidelines
Follow these guidelines when configuring the switch as an SSH server or SSH client:
•
An RSA key pair generated by a SSHv1 server can be used by an SSHv2 server, and the reverse.
•
If you get CLI error messages after entering the crypto key generate rsa global configuration
command, an RSA key pair has not been generated. Reconfigure the hostname and domain, and then
enter the crypto key generate rsa command. For more information, see the “Setting Up the Switch
to Run SSH” section on page 7-46.
•
When generating the RSA key pair, the message No host name specified might appear. If it does,
you must configure a hostname by using the hostname global configuration command.
•
When generating the RSA key pair, the message No domain specified might appear. If it does, you
must configure an IP domain name by using the ip domain-name global configuration command.
•
When configuring the local authentication and authorization authentication method, make sure that
AAA is disabled on the console.
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Setting Up the Switch to Run SSH
Follow these steps to set up your switch to run SSH:
1.
Download the cryptographic software image from Cisco.com. This step is required. For more
information, see the release notes for this release.
2.
Configure a hostname and IP domain name for the switch. Follow this procedure only if you are
configuring the switch as an SSH server.
3.
Generate an RSA key pair for the switch, which automatically enables SSH. Follow this procedure
only if you are configuring the switch as an SSH server.
4.
Configure user authentication for local or remote access. This step is required. For more
information, see the “Configuring the Switch for Local Authentication and Authorization” section
on page 7-42.
Beginning in privileged EXEC mode, follow these steps to configure a hostname and an IP domain name
and to generate an RSA key pair. This procedure is required if you are configuring the switch as an SSH
server.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
hostname hostname
Configure a hostname for your switch.
Step 3
ip domain-name domain_name
Configure a host domain for your switch.
Step 4
crypto key generate rsa
Enable the SSH server for local and remote authentication on the switch
and generate an RSA key pair.
We recommend that a minimum modulus size of 1024 bits.
When you generate RSA keys, you are prompted to enter a modulus
length. A longer modulus length might be more secure, but it takes longer
to generate and to use.
Step 5
end
Return to privileged EXEC mode.
Step 6
show ip ssh
Show the version and configuration information for your SSH server.
or
Step 7
show ssh
Show the status of the SSH server on the switch.
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To delete the RSA key pair, use the crypto key zeroize rsa global configuration command. After the
RSA key pair is deleted, the SSH server is automatically disabled.
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Configuring the SSH Server
Beginning in privileged EXEC mode, follow these steps to configure the SSH server:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
ip ssh version [1 | 2]
(Optional) Configure the switch to run SSH Version 1 or SSH Version 2.
•
1—Configure the switch to run SSH Version 1.
•
2—Configure the switch to run SSH Version 2.
If you do not enter this command or do not specify a keyword, the SSH
server selects the latest SSH version supported by the SSH client. For
example, if the SSH client supports SSHv1 and SSHv2, the SSH server
selects SSHv2.
Step 3
ip ssh {timeout seconds |
authentication-retries number}
Configure the SSH control parameters:
•
Specify the time-out value in seconds; the default is 120 seconds. The
range is 0 to 120 seconds. This parameter applies to the SSH
negotiation phase. After the connection is established, the switch uses
the default time-out values of the CLI-based sessions.
By default, up to five simultaneous, encrypted SSH connections for
multiple CLI-based sessions over the network are available (session 0
to session 4). After the execution shell starts, the CLI-based session
time-out value returns to the default of 10 minutes.
•
Specify the number of times that a client can re-authenticate to the
server. The default is 3; the range is 0 to 5.
Repeat this step when configuring both parameters.
Step 4
line vty line_number
[ending_line_number]
(Optional) Configure the virtual terminal line settings.
•
Enter line configuration mode to configure the virtual terminal line
settings. For line_number and ending_line_number, specify a pair of
lines. The range is 0 to 15.
•
Specify that the switch prevent non-SSH Telnet connections. This
limits the router to only SSH connections.
transport input ssh
Step 5
end
Return to privileged EXEC mode.
Step 6
show ip ssh
Show the version and configuration information for your SSH server.
or
Step 7
show ssh
Show the status of the SSH server connections on the switch.
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To return to the default SSH control parameters, use the no ip ssh {timeout | authentication-retries}
global configuration command.
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Configuring the Switch for Secure Socket Layer HTTP
Displaying the SSH Configuration and Status
To display the SSH server configuration and status, use one or more of the privileged EXEC commands
in Table 7-6:
Table 7-6
Commands for Displaying the SSH Server Configuration and Status
Command
Purpose
show ip ssh
Shows the version and configuration information for the SSH server.
show ssh
Shows the status of the SSH server.
For more information about these commands, see the “Secure Shell Commands” section in the “Other
Security Features” chapter of the Cisco IOS Security Command Reference, Cisco IOS Release 12.2, at
this URL:
http://www.cisco.com/en/US/docs/ios/12_2/security/command/reference/fsecur_r.html
Configuring the Switch for Secure Socket Layer HTTP
This section describes how to configure Secure Socket Layer (SSL) version 3.0 support for the HTTP 1.1
server and client. SSL provides server authentication, encryption, and message integrity, as well as
HTTP client authentication, to allow secure HTTP communications. To use this feature, the
cryptographic (encrypted) software image must be installed on your switch. You must obtain
authorization to use this feature and to download the cryptographic software files from Cisco.com. For
more information about the crypto image, see the release notes for this release.
These sections contain this information:
•
Understanding Secure HTTP Servers and Clients, page 7-48
•
Configuring Secure HTTP Servers and Clients, page 7-51
•
Displaying Secure HTTP Server and Client Status, page 7-54
For configuration examples and complete syntax and usage information for the commands used in this
section, see the “HTTPS - HTTP Server and Client with SSL 3.0” feature description for Cisco IOS
Release 12.2T at this URL:
http://www.cisco.com/en/US/docs/ios/12_2t/12_2t15/feature/guide/ftsslsht.html
Understanding Secure HTTP Servers and Clients
On a secure HTTP connection, data to and from an HTTP server is encrypted before being sent over the
Internet. HTTP with SSL encryption provides a secure connection to allow such functions as configuring
a switch from a Web browser. Cisco's implementation of the secure HTTP server and secure HTTP client
uses an implementation of SSL Version 3.0 with application-layer encryption. HTTP over SSL is
abbreviated as HTTPS; the URL of a secure connection begins with https:// instead of http://.
The primary role of the HTTP secure server (the switch) is to listen for HTTPS requests on a designated
port (the default HTTPS port is 443) and pass the request to the HTTP 1.1 Web server. The HTTP 1.1
server processes requests and passes responses (pages) back to the HTTP secure server, which, in turn,
responds to the original request.
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The primary role of the HTTP secure client (the web browser) is to respond to Cisco IOS application
requests for HTTPS User Agent services, perform HTTPS User Agent services for the application, and
pass the response back to the application.
Certificate Authority Trustpoints
Certificate authorities (CAs) manage certificate requests and issue certificates to participating network
devices. These services provide centralized security key and certificate management for the participating
devices. Specific CA servers are referred to as trustpoints.
When a connection attempt is made, the HTTPS server provides a secure connection by issuing a
certified X.509v3 certificate, obtained from a specified CA trustpoint, to the client. The client (usually
a Web browser), in turn, has a public key that allows it to authenticate the certificate.
For secure HTTP connections, we highly recommend that you configure a CA trustpoint. If a CA
trustpoint is not configured for the device running the HTTPS server, the server certifies itself and
generates the needed RSA key pair. Because a self-certified (self-signed) certificate does not provide
adequate security, the connecting client generates a notification that the certificate is self-certified, and
the user has the opportunity to accept or reject the connection. This option is useful for internal network
topologies (such as testing).
If you do not configure a CA trustpoint, when you enable a secure HTTP connection, either a temporary
or a persistent self-signed certificate for the secure HTTP server (or client) is automatically generated.
Note
•
If the switch is not configured with a hostname and a domain name, a temporary self-signed
certificate is generated. If the switch reboots, any temporary self-signed certificate is lost, and a new
temporary new self-signed certificate is assigned.
•
If the switch has been configured with a host and domain name, a persistent self-signed certificate
is generated. This certificate remains active if you reboot the switch or if you disable the secure
HTTP server so that it will be there the next time you re-enable a secure HTTP connection.
The certificate authorities and trustpoints must be configured on each device individually. Copying them
from other devices makes them invalid on the switch.
If a self-signed certificate has been generated, this information is included in the output of the show
running-config privileged EXEC command. This is a partial sample output from that command
displaying a self-signed certificate.
Switch# show running-config
Building configuration...
<output truncated>
crypto pki trustpoint TP-self-signed-3080755072
enrollment selfsigned
subject-name cn=IOS-Self-Signed-Certificate-3080755072
revocation-check none
rsakeypair TP-self-signed-3080755072
!
crypto ca certificate chain TP-self-signed-3080755072
certificate self-signed 01
3082029F 30820208 A0030201 02020101 300D0609 2A864886
59312F30 2D060355 04031326 494F532D 53656C66 2D536967
69666963 6174652D 33303830 37353530 37323126 30240609
02161743 45322D33 3535302D 31332E73 756D6D30 342D3335
30333031 30303030 35395A17 0D323030 31303130 30303030
<output truncated>
F70D0101
6E65642D
2A864886
3530301E
305A3059
04050030
43657274
F70D0109
170D3933
312F302D
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You can remove this self-signed certificate by disabling the secure HTTP server and entering the no
crypto pki trustpoint TP-self-signed-30890755072 global configuration command. If you later
re-enable a secure HTTP server, a new self-signed certificate is generated.
Note
The values that follow TP self-signed depend on the serial number of the device.
You can use an optional command (ip http secure-client-auth) to allow the HTTPS server to request an
X.509v3 certificate from the client. Authenticating the client provides more security than server
authentication by itself.
For additional information on Certificate Authorities, see the “Configuring Certification Authority
Interoperability” chapter in the Cisco IOS Security Configuration Guide, Release 12.2 from the
Cisco.com page under Documentation > Cisco IOS Software > 12.2 Mainline > Command
References.
CipherSuites
A CipherSuite specifies the encryption algorithm and the digest algorithm to use on a SSL connection.
When connecting to the HTTPS server, the client Web browser offers a list of supported CipherSuites,
and the client and server negotiate the best encryption algorithm to use from those on the list that are
supported by both. For example, Netscape Communicator 4.76 supports U.S. security with RSA Public
Key Cryptography, MD2, MD5, RC2-CBC, RC4, DES-CBC, and DES-EDE3-CBC.
For the best possible encryption, you should use a client browser that supports 128-bit encryption, such
as Microsoft Internet Explorer Version 5.5 (or later) or Netscape Communicator Version 4.76 (or later).
The SSL_RSA_WITH_DES_CBC_SHA CipherSuite provides less security than the other CipherSuites,
as it does not offer 128-bit encryption.
The more secure and more complex CipherSuites require slightly more processing time. This list defines
the CipherSuites supported by the switch and ranks them from fastest to slowest in terms of router
processing load (speed):
1.
SSL_RSA_WITH_DES_CBC_SHA—RSA key exchange (RSA Public Key Cryptography) with
DES-CBC for message encryption and SHA for message digest
2.
SSL_RSA_WITH_RC4_128_MD5—RSA key exchange with RC4 128-bit encryption and MD5 for
message digest
3.
SSL_RSA_WITH_RC4_128_SHA—RSA key exchange with RC4 128-bit encryption and SHA for
message digest
4.
SSL_RSA_WITH_3DES_EDE_CBC_SHA—RSA key exchange with 3DES and DES-EDE3-CBC
for message encryption and SHA for message digest
RSA (in conjunction with the specified encryption and digest algorithm combinations) is used for both
key generation and authentication on SSL connections. This usage is independent of whether or not a
CA trustpoint is configured.
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Configuring the Switch for Secure Socket Layer HTTP
Configuring Secure HTTP Servers and Clients
These sections contain this configuration information:
•
Default SSL Configuration, page 7-51
•
SSL Configuration Guidelines, page 7-51
•
Configuring a CA Trustpoint, page 7-51
•
Configuring the Secure HTTP Server, page 7-52
•
Configuring the Secure HTTP Client, page 7-54
Default SSL Configuration
The standard HTTP server is enabled.
SSL is enabled.
No CA trustpoints are configured.
No self-signed certificates are generated.
SSL Configuration Guidelines
Before you configure a CA trustpoint, you should ensure that the system clock is set. If the clock is not
set, the certificate is rejected due to an incorrect date.
Configuring a CA Trustpoint
For secure HTTP connections, we recommend that you configure an official CA trustpoint.
A CA trustpoint is more secure than a self-signed certificate.
Beginning in privileged EXEC mode, follow these steps to configure a CA trustpoint:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
hostname hostname
Specify the hostname of the switch (required only if you have not
previously configured a hostname). The hostname is required for security
keys and certificates.
Step 3
ip domain-name domain-name
Specify the IP domain name of the switch (required only if you have not
previously configured an IP domain name). The domain name is required
for security keys and certificates.
Step 4
crypto key generate rsa
(Optional) Generate an RSA key pair. RSA key pairs are required before
you can obtain a certificate for the switch. RSA key pairs are generated
automatically. You can use this command to regenerate the keys, if
needed.
Step 5
crypto ca trustpoint name
Specify a local configuration name for the CA trustpoint and enter CA
trustpoint configuration mode.
Step 6
enrollment url url
Specify the URL to which the switch should send certificate requests.
Step 7
enrollment http-proxy host-name
port-number
(Optional) Configure the switch to obtain certificates from the CA
through an HTTP proxy server.
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Command
Purpose
Step 8
crl query url
Configure the switch to request a certificate revocation list (CRL) to
ensure that the certificate of the peer has not been revoked.
Step 9
primary
(Optional) Specify that the trustpoint should be used as the primary
(default) trustpoint for CA requests.
Step 10
exit
Exit CA trustpoint configuration mode and return to global configuration
mode.
Step 11
crypto ca authentication name
Authenticate the CA by getting the public key of the CA. Use the same
name used in Step 5.
Step 12
crypto ca enroll name
Obtain the certificate from the specified CA trustpoint. This command
requests a signed certificate for each RSA key pair.
Step 13
end
Return to privileged EXEC mode.
Step 14
show crypto ca trustpoints
Verify the configuration.
Step 15
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Use the no crypto ca trustpoint name global configuration command to delete all identity information
and certificates associated with the CA.
Configuring the Secure HTTP Server
If you are using a certificate authority for certification, you should use the previous procedure to
configure the CA trustpoint on the switch before enabling the HTTP server. If you have not configured
a CA trustpoint, a self-signed certificate is generated the first time that you enable the secure HTTP
server. After you have configured the server, you can configure options (path, access list to apply,
maximum number of connections, or timeout policy) that apply to both standard and secure HTTP
servers.
Beginning in privileged EXEC mode, follow these steps to configure a secure HTTP server:
Step 1
Command
Purpose
show ip http server status
(Optional) Display the status of the HTTP server to determine if the secure
HTTP server feature is supported in the software. You should see one of
these lines in the output:
HTTP secure server capability: Present
or
HTTP secure server capability: Not present
Step 2
configure terminal
Enter global configuration mode.
Step 3
ip http secure-server
Enable the HTTPS server if it has been disabled. The HTTPS server is
enabled by default.
Step 4
ip http secure-port port-number
(Optional) Specify the port number to be used for the HTTPS server. The
default port number is 443. Valid options are 443 or any number in the
range 1025 to 65535.
ip http secure-ciphersuite
{[3des-ede-cbc-sha] [rc4-128-md5]
[rc4-128-sha] [des-cbc-sha]}
(Optional) Specify the CipherSuites (encryption algorithms) to be used
for encryption over the HTTPS connection. If you do not have a reason to
specify a particularly CipherSuite, you should allow the server and client
to negotiate a CipherSuite that they both support. This is the default.
Step 5
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Step 6
Step 7
Command
Purpose
ip http secure-client-auth
(Optional) Configure the HTTP server to request an X.509v3 certificate
from the client for authentication during the connection process. The
default is for the client to request a certificate from the server, but the
server does not attempt to authenticate the client.
ip http secure-trustpoint name
Specify the CA trustpoint to use to get an X.509v3 security certificate and
to authenticate the client certificate connection.
Note
Use of this command assumes you have already configured a CA
trustpoint according to the previous procedure.
Step 8
ip http path path-name
(Optional) Set a base HTTP path for HTML files. The path specifies the
location of the HTTP server files on the local system (usually located in
system flash memory).
Step 9
ip http access-class access-list-number
(Optional) Specify an access list to use to allow access to the HTTP server.
Step 10
ip http max-connections value
(Optional) Set the maximum number of concurrent connections that are
allowed to the HTTP server. The range is 1 to 16; the default value is 5.
Step 11
ip http timeout-policy idle seconds life (Optional) Specify how long a connection to the HTTP server can remain
seconds requests value
open under the defined circumstances:
•
idle—the maximum time period when no data is received or response
data cannot be sent. The range is 1 to 600 seconds. The default is
180 seconds (3 minutes).
•
life—the maximum time period from the time that the connection is
established. The range is 1 to 86400 seconds (24 hours). The default
is 180 seconds.
•
requests—the maximum number of requests processed on a
persistent connection. The maximum value is 86400. The default is 1.
Step 12
end
Return to privileged EXEC mode.
Step 13
show ip http server secure status
Display the status of the HTTP secure server to verify the configuration.
Step 14
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Use the no ip http server global configuration command to disable the standard HTTP server. Use the
no ip http secure-server global configuration command to disable the secure HTTP server. Use the no
ip http secure-port and the no ip http secure-ciphersuite global configuration commands to return to
the default settings. Use the no ip http secure-client-auth global configuration command to remove the
requirement for client authentication.
To verify the secure HTTP connection by using a Web browser, enter https://URL, where the URL is the
IP address or hostname of the server switch. If you configure a port other than the default port, you must
also specify the port number after the URL. For example:
https://209.165.129:1026
or
https://host.domain.com:1026
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Configuring Switch-Based Authentication
Configuring the Switch for Secure Socket Layer HTTP
Configuring the Secure HTTP Client
The standard HTTP client and secure HTTP client are always enabled. A certificate authority is required
for secure HTTP client certification. This procedure assumes that you have previously configured a CA
trustpoint on the switch. If a CA trustpoint is not configured and the remote HTTPS server requires client
authentication, connections to the secure HTTP client fail.
Beginning in privileged EXEC mode, follow these steps to configure a secure HTTP client:
Command
Purpose
configure terminal
Enter global configuration mode.
ip http client secure-trustpoint name
(Optional) Specify the CA trustpoint to be used if the remote HTTP server
requests client authentication. Using this command assumes that you have
already configured a CA trustpoint by using the previous procedure. The
command is optional if client authentication is not needed or if a primary
trustpoint has been configured.
Step 3
ip http client secure-ciphersuite
{[3des-ede-cbc-sha] [rc4-128-md5]
[rc4-128-sha] [des-cbc-sha]}
(Optional) Specify the CipherSuites (encryption algorithms) to be used
for encryption over the HTTPS connection. If you do not have a reason to
specify a particular CipherSuite, you should allow the server and client to
negotiate a CipherSuite that they both support. This is the default.
Step 4
end
Return to privileged EXEC mode.
Step 5
show ip http client secure status
Display the status of the HTTP secure server to verify the configuration.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Step 1
Step 2
Use the no ip http client secure-trustpoint name to remove a client trustpoint configuration. Use the
no ip http client secure-ciphersuite to remove a previously configured CipherSuite specification for
the client.
Displaying Secure HTTP Server and Client Status
To display the SSL secure server and client status, use the privileged EXEC commands in Table 7-7:
Table 7-7
Commands for Displaying the SSL Secure Server and Client Status
Command
Purpose
show ip http client secure status
Shows the HTTP secure client configuration.
show ip http server secure status
Shows the HTTP secure server configuration.
show running-config
Shows the generated self-signed certificate for secure HTTP connections.
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Configuring Switch-Based Authentication
Configuring the Switch for Secure Copy Protocol
Configuring the Switch for Secure Copy Protocol
The Secure Copy Protocol (SCP) feature provides a secure and authenticated method for copying switch
configurations or switch image files. SCP relies on Secure Shell (SSH), an application and a protocol
that provides a secure replacement for the Berkeley r-tools.
For SSH to work, the switch needs an RSA public/private key pair. This is the same with SCP, which
relies on SSH for its secure transport.
Because SSH also relies on AAA authentication, and SCP relies further on AAA authorization, correct
configuration is necessary.
Note
•
Before enabling SCP, you must correctly configure SSH, authentication, and authorization on the
switch.
•
Because SCP relies on SSH for its secure transport, the router must have an Rivest, Shamir, and
Adelman (RSA) key pair.
When using SCP, you cannot enter the password into the copy command. You must enter the password
when prompted.
Information About Secure Copy
To configure the Secure Copy feature, you should understand these concepts.
The behavior of SCP is similar to that of remote copy (rcp), which comes from the Berkeley r-tools suite,
except that SCP relies on SSH for security. SCP also requires that authentication, authorization, and
accounting (AAA) authorization be configured so the router can determine whether the user has the
correct privilege level.
A user who has appropriate authorization can use SCP to copy any file in the Cisco IOS File System
(IFS) to and from a switch by using the copy command. An authorized administrator can also do this
from a workstation.
For information about how to configure and verify SCP, see the “Secure Copy Protocol” section in the
Cisco IOS Security Configuration Guide: Securing User Services, Release 12.4:
http://www.cisco.com/en/US/docs/ios/sec_user_services/configuration/guide/sec_secure_copy_ps6350
_TSD_Products_Configuration_Guide_Chapter.html
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Configuring Switch-Based Authentication
Configuring the Switch for Secure Copy Protocol
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CH A P T E R
8
Configuring IEEE 802.1x Port-Based
Authentication
This chapter describes how to configure IEEE 802.1x port-based authentication on the switch.
IEEE 802.1x authentication prevents unauthorized devices (clients) from gaining access to the network.
Note
For complete syntax and usage information for the commands used in this chapter, see the command
reference for this release and the “RADIUS Commands” section in the Cisco IOS Security Command
Reference, Release 12.2 from the Cisco.com page under Documentation > Cisco IOS Software > 12.2
Mainline > Command References
The switch also supports Cisco TrustSec Security Group Tag (SCT) Exchange Protocol (SXP). This
feature supports security group access control lists (SGACLs), which define ACL policies for a group of
devices instead of an IP address. The SXP control protocol allows tagging packets with SCTs without a
hardware upgrade, and runs between access layer devices at the Cisco TrustSec domain edge and
distribution layer devices within the Cisco TrustSec domain. The blade switches operate as access layer
switches in the Cisco TrustSec network.
For more information about Cisco TrustSec, see the “Cisco TrustSec Switch Configuration Guide” at this
URL:
http://www.cisco.com/en/US/docs/switches/lan/trustsec/configuration/guide/trustsec.html
The sections on SXP define the capabilities supported on the blade switches.
This chapter consists of these sections:
•
Understanding IEEE 802.1x Port-Based Authentication, page 8-1
•
Configuring 802.1x Authentication, page 8-33
•
Displaying 802.1x Statistics and Status, page 8-66
Understanding IEEE 802.1x Port-Based Authentication
The IEEE 802.1x standard defines a client-server-based access control and authentication protocol that
prevents unauthorized clients from connecting to a LAN through publicly accessible ports unless they
are properly authenticated. The authentication server authenticates each client connected to a switch port
before making available any services offered by the switch or the LAN.
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Configuring IEEE 802.1x Port-Based Authentication
Understanding IEEE 802.1x Port-Based Authentication
Until the client is authenticated, 802.1x access control allows only Extensible Authentication Protocol
over LAN (EAPOL), Cisco Discovery Protocol (CDP), and Spanning Tree Protocol (STP) traffic through
the port to which the client is connected. After authentication is successful, normal traffic can pass
through the port.
These sections describe IEEE 802.1x port-based authentication:
•
Device Roles, page 8-3
•
Authentication Process, page 8-4
•
Authentication Initiation and Message Exchange, page 8-6
•
Ports in Authorized and Unauthorized States, page 8-11
•
Authentication Manager, page 8-8
•
802.1x Host Mode, page 8-12
•
MAC Move, page 8-14
•
MAC Replace, page 8-14
•
802.1x Accounting, page 8-15
•
802.1x Accounting Attribute-Value Pairs, page 8-15
•
802.1x Readiness Check, page 8-16
•
802.1x Authentication with VLAN Assignment, page 8-16
•
802.1x Authentication with Per-User ACLs, page 8-18
•
•
802.1x Authentication with Restricted VLAN, page 8-23
•
802.1x Authentication with Inaccessible Authentication Bypass, page 8-24
•
802.1x User Distribution, page 8-25
•
802.1x Authentication with Voice VLAN Ports, page 8-26
•
802.1x Authentication with Port Security, page 8-26
•
802.1x Authentication with Downloadable ACLs and Redirect URLs, page 8-19
•
VLAN ID-based MAC Authentication, page 8-21
•
802.1x Authentication with Wake-on-LAN, page 8-27
•
802.1x Authentication with MAC Authentication Bypass, page 8-27
•
Flexible Authentication Ordering, page 8-29
•
Open1x Authentication, page 8-29
•
802.1x Supplicant and Authenticator Switches with Network Edge Access Topology (NEAT),
page 8-31
•
Common Session ID, page 8-32
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Understanding IEEE 802.1x Port-Based Authentication
Device Roles
With IEEE 802.1x port-based authentication, the devices in the network have specific roles as shown in
Figure 8-1.
Figure 8-1
IEEE 802.1x Device Roles
Authentication
server
(RADIUS)
101229
Workstations
(clients)
•
Client—the device (workstation) that requests access to the LAN and switch services and responds
to requests from the switch. The workstation must be running IEEE 802.1x-compliant client
software such as that offered in the Microsoft Windows XP operating system. (The client is the
supplicant in the IEEE 802.1x standard.)
Note
To resolve Windows XP network connectivity and IEEE 802.1x authentication issues, read
the Microsoft Knowledge Base article at this URL:
http://support.microsoft.com/support/kb/articles/Q303/5/97.ASP
•
Authentication server—performs the actual authentication of the client. The authentication server
validates the identity of the client and notifies the switch whether or not the client is authorized to
access the LAN and switch services. Because the switch acts as the proxy, the authentication service
is transparent to the client. In this release, the RADIUS security system with Extensible
Authentication Protocol (EAP) extensions is the only supported authentication server. It is available
in Cisco Secure Access Control Server Version 3.0 or later. RADIUS operates in a client/server
model in which secure authentication information is exchanged between the RADIUS server and
one or more RADIUS clients.
•
Switch (edge switch or wireless access point)—controls the physical access to the network based on
the authentication status of the client. The switch acts as an intermediary (proxy) between the client
and the authentication server, requesting identity information from the client, verifying that
information with the authentication server, and relaying a response to the client. The switch includes
the RADIUS client, which is responsible for encapsulating and decapsulating the EAP frames and
interacting with the authentication server. (The switch is the authenticator in the IEEE 802.1x
standard.)
When the switch receives EAPOL frames and relays them to the authentication server, the Ethernet
header is stripped, and the remaining EAP frame is re-encapsulated in the RADIUS format. The
EAP frames are not modified during encapsulation, and the authentication server must support EAP
within the native frame format. When the switch receives frames from the authentication server, the
server’s frame header is removed, leaving the EAP frame, which is then encapsulated for Ethernet
and sent to the client.
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Configuring IEEE 802.1x Port-Based Authentication
Understanding IEEE 802.1x Port-Based Authentication
The devices that can act as intermediaries include the Catalyst 3750-E, Catalyst 3560-E, Catalyst
3750, Catalyst 3560, Catalyst 3550, Catalyst 2970, Catalyst 2960, Cisco Catalyst Blade Switch 3030
for Dell, Catalyst 2955, Catalyst 2950, Catalyst 2940 switches, or a wireless access point. These
devices must be running software that supports the RADIUS client and IEEE 802.1x authentication.
Authentication Process
When IEEE 802.1x port-based authentication is enabled and the client supports IEEE 802.1x-compliant
client software, these events occur:
•
If the client identity is valid and the IEEE 802.1x authentication succeeds, the switch grants the
client access to the network.
•
If IEEE 802.1x authentication times out while waiting for an EAPOL message exchange and MAC
authentication bypass is enabled, the switch can use the client MAC address for authorization. If the
client MAC address is valid and the authorization succeeds, the switch grants the client access to the
network. If the client MAC address is invalid and the authorization fails, the switch assigns the client
to a guest VLAN that provides limited services if a guest VLAN is configured.
•
If the switch gets an invalid identity from an IEEE 802.1x-capable client and a restricted VLAN is
specified, the switch can assign the client to a restricted VLAN that provides limited services.
•
If the RADIUS authentication server is unavailable (down) and inaccessible authentication bypass
is enabled, the switch grants the client access to the network by putting the port in the
critical-authentication state in the RADIUS-configured or the user-specified access VLAN.
Note
Inaccessible authentication bypass is also referred to as critical authentication or the AAA fail
policy.
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Understanding IEEE 802.1x Port-Based Authentication
Figure 8-2 shows the authentication process.
If Multi Domain Authentication (MDA) is enabled on a port, this flow can be used with some exceptions
that are applicable to voice authorization. For more information on MDA, see “Using Multidomain
Authentication” section on page 8-30.
Figure 8-2
Authentication Flowchart
Start
User does not have a
certificate but the system
previously logged on to
the network using
a computer certificate.
No
Yes
The switch gets an
EAPOL message,
and the EAPOL
message
exchange begins.
Start IEEE 802.1x port-based
authentication.
Client
Client
identity is
identity is
invalid
valid
Assign the port to
a guest VLAN.
Assign the port to
a restricted VLAN.
Assign the port to
a VLAN.
Done
Done
Done
All authentication
servers are down.
Use inaccessible
authentication bypass
(critical authentication)
to assign the critical
port to a VLAN.
Is MAC authentication
bypass enabled? 1
IEEE 802.1x authentication
process times out.
No
Use MAC authentication
bypass.1
Client MAC
address
identity
is invalid.
Client MAC
address
identity
is valid.
Assign the port to
a VLAN.
Assign the port to
a guest VLAN. 1
Done
Done
All authentication
servers are down.
1 = This occurs if the switch does not
detect EAPOL packets from the client.
281594
Is the client IEEE
802.1x capable?
Yes
Done
The switch re-authenticates a client when one of these situations occurs:
•
Periodic re-authentication is enabled, and the re-authentication timer expires.
You can configure the re-authentication timer to use a switch-specific value or to be based on values
from the RADIUS server.
After IEEE 802.1x authentication using a RADIUS server is configured, the switch uses timers
based on the Session-Timeout RADIUS attribute (Attribute[27]) and the Termination-Action
RADIUS attribute (Attribute [29]).
The Session-Timeout RADIUS attribute (Attribute[27]) specifies the time after which
re-authentication occurs.
The Termination-Action RADIUS attribute (Attribute [29]) specifies the action to take during
re-authentication. The actions are Initialize and ReAuthenticate. When the Initialize action is set (the
attribute value is DEFAULT), the IEEE 802.1x session ends, and connectivity is lost during
re-authentication. When the ReAuthenticate action is set (the attribute value is RADIUS-Request),
the session is not affected during re-authentication.
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Understanding IEEE 802.1x Port-Based Authentication
•
You manually re-authenticate the client by entering the dot1x re-authenticate interface
interface-id privileged EXEC command.
Authentication Initiation and Message Exchange
During IEEE 802.1x authentication, the switch or the client can initiate authentication. If you enable
authentication on a port by using the authentication port-control auto or dot1x port-control auto
interface configuration command, the switch initiates authentication when the link state changes from
down to up or periodically as long as the port remains up and unauthenticated. The switch sends an
EAP-request/identity frame to the client to request its identity. Upon receipt of the frame, the client
responds with an EAP-response/identity frame.
However, if during bootup, the client does not receive an EAP-request/identity frame from the switch,
the client can initiate authentication by sending an EAPOL-start frame, which prompts the switch to
request the client’s identity.
Note
If IEEE 802.1x authentication is not enabled or supported on the network access device, any EAPOL
frames from the client are dropped. If the client does not receive an EAP-request/identity frame after
three attempts to start authentication, the client sends frames as if the port is in the authorized state. A
port in the authorized state effectively means that the client has been successfully authenticated. For
more information, see the “Ports in Authorized and Unauthorized States” section on page 8-11.
When the client supplies its identity, the switch begins its role as the intermediary, passing EAP frames
between the client and the authentication server until authentication succeeds or fails. If the
authentication succeeds, the switch port becomes authorized. If the authentication fails, authentication
can be retried, the port might be assigned to a VLAN that provides limited services, or network access
is not granted. For more information, see the “Ports in Authorized and Unauthorized States” section on
page 8-11.
The specific exchange of EAP frames depends on the authentication method being used. Figure 8-3
shows a message exchange initiated by the client when the client uses the One-Time-Password (OTP)
authentication method with a RADIUS server.
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Understanding IEEE 802.1x Port-Based Authentication
Figure 8-3
Message Exchange
Client
Blade Switch
Authentication
server
(RADIUS)
EAPOL-Start
EAP-Request/Identity
EAP-Response/Identity
RADIUS Access-Request
EAP-Request/OTP
RADIUS Access-Challenge
EAP-Response/OTP
RADIUS Access-Request
EAP-Success
RADIUS Access-Accept
Port Authorized
Port Unauthorized
119943
EAPOL-Logoff
If IEEE 802.1x authentication times out while waiting for an EAPOL message exchange and MAC
authentication bypass is enabled, the switch can authorize the client when the switch detects an Ethernet
packet from the client. The switch uses the MAC address of the client as its identity and includes this
information in the RADIUS-access/request frame that is sent to the RADIUS server. After the server
sends the switch the RADIUS-access/accept frame (authorization is successful), the port becomes
authorized. If authorization fails and a guest VLAN is specified, the switch assigns the port to the guest
VLAN. If the switch detects an EAPOL packet while waiting for an Ethernet packet, the switch stops
the MAC authentication bypass process and stops IEEE 802.1x authentication.
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Understanding IEEE 802.1x Port-Based Authentication
Figure 8-4 shows the message exchange during MAC authentication bypass.
Figure 8-4
Message Exchange During MAC Authentication Bypass
Client
Authentication
server
(RADIUS)
Switch
EAPOL Request/Identity
EAPOL Request/Identity
EAPOL Request/Identity
RADIUS Access/Request
RADIUS Access/Accept
141681
Ethernet packet
Authentication Manager
In Cisco IOS Release 12.2(46)SE and earlier, you could not use the same authorization methods, including
CLI commands and messages, on this switch and also on other network devices, such as a Catalyst 6000.
You had to use separate authentication configurations. Cisco IOS Release 12.2(50)SE and later supports
the same authorization methods on all Catalyst switches in a network.
Cisco IOS Release 12.2(55)SE supports filtering verbose system messages from the authentication
manager. For details, see the “Authentication Manager CLI Commands” section on page 8-10.
•
Port-Based Authentication Methods, page 8-9
•
Per-User ACLs and Filter-Ids, page 8-9
•
Authentication Manager CLI Commands, page 8-10
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Understanding IEEE 802.1x Port-Based Authentication
Port-Based Authentication Methods
Table 8-1
802.1x Features
Mode
Authentication method
Single host
Multiple host
MDA1
Multiple
Authentication22
802.1x
VLAN assignment
VLAN assignment
VLAN assignment
Per-user ACL2
Per-user ACL
Per-user ACL2
Filter-Id attribute2
Filter-ID attribute
Filter-Id attribute2
Downloadable
ACL3
Downloadable
ACL2
Downloadable
ACL2
Redirect URL 2
Redirect URL2
MAC authentication bypass
Redirect URL2
VLAN assignment
Per-user ACL2
Per-user ACL
Per-user ACL2
Filter-Id attribute2
Filter-ID attribute
Filter-Id attribute2
Downloadable
ACL2
Downloadable
ACL2
Downloadable
ACL2
Redirect URL2
Redirect URL2
VLAN assignment
VLAN assignment
Standalone web authentication4
Proxy ACL, Filter-Id attribute, downloadable ACL2
NAC Layer 2 IP validation
Filter-Id attribute2
Filter-Id attribute2
Filter-Id attribute2
Redirect URL2
Filter-Id attribute2
Downloadable ACL Downloadable ACL Downloadable ACL Downloadable
ACL2
Redirect URL
Redirect URL
Redirect URL
Redirect URL2
Web authentication as fallback
method4
Proxy ACL
Proxy ACL
Proxy ACL
Proxy ACL2
Filter-Id attribute2
Filter-Id attribute2
Filter-Id attribute2
Filter-Id attribute2
Downloadable
ACL2
Downloadable
ACL2
Downloadable
ACL2
Downloadable
ACL2
1. MDA = Multidomain authentication.
2. Also referred to as multiauth.
3. Supported in Cisco IOS Release 12.2(50)SE and later.
4. For clients that do not support 802.1x authentication.
Per-User ACLs and Filter-Ids
In releases earlier than Cisco IOS Release 12.2(50)SE, an ACL configured on the switch is not
compatible with an ACL configured on another device running Cisco IOS software, such as a
Catalyst 6000 switch.
In Cisco IOS Release 12.2(50)SE or later, the ACLs configured on the switch are compatible with other
devices running Cisco IOS release.
You can only set any as the source in the ACL.
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Understanding IEEE 802.1x Port-Based Authentication
Note
For any ACL configured for multiple-host mode, the source portion of statement must be any. (For
example, permit icmp any host 10.10.1.1.)
Authentication Manager CLI Commands
The authentication-manager interface-configuration commands control all the authentication methods,
such as 802.1x, MAC authentication bypass, and web authentication. The authentication manager
commands determine the priority and order of authentication methods applied to a connected host.
The authentication manager commands control generic authentication features, such as host-mode,
violation mode, and the authentication timer. Generic authentication commands include the
authentication host-mode, authentication violation, and authentication timer interface
configuration commands.
802.1x-specific commands begin with the dot1x keyword. For example, the authentication
port-control auto interface configuration command enables authentication on an interface. However,
the dot1x system-authentication control global configuration command only globally enables or
disables 802.1x authentication.
Note
If 802.1x authentication is globally disabled, other authentication methods are still enabled on that port,
such as web authentication.
The authentication manager commands provide the same functionality as earlier 802.1x commands.
Table 8-2
Authentication Manager Commands and Earlier 802.1x Commands
The authentication manager
commands in Cisco IOS
Release 12.2(50)SE or later
The equivalent 802.1x commands in
Cisco IOS Release 12.2(46)SE and
earlier
Description
authentication control-direction
{both | in}
dot1x control-direction {both |
in}
Enable 802.1x authentication with the
wake-on-LAN (WoL) feature, and configure the
port control as unidirectional or bidirectional.
authentication event
dot1x auth-fail vlan
Enable the restricted VLAN on a port.
dot1x critical (interface
configuration)
Enable the inaccessible-authentication-bypass
feature.
dot1x guest-vlan6
Specify an active VLAN as an 802.1x guest
VLAN.
authentication fallback
fallback-profile
dot1x fallback fallback-profile
Configure a port to use web authentication as a
fallback method for clients that do not support
802.1x authentication.
authentication host-mode
[multi-auth | multi-domain |
multi-host | single-host]
dot1x host-mode {single-host |
multi-host | multi-domain}
Allow a single host (client) or multiple hosts on
an 802.1x-authorized port.
authentication order
dot1x mac-auth-bypass
Enable the MAC authentication bypass feature.
authentication periodic
dot1x reauthentication
Enable periodic re-authentication of the client.
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Understanding IEEE 802.1x Port-Based Authentication
Table 8-2
Authentication Manager Commands and Earlier 802.1x Commands (continued)
The authentication manager
commands in Cisco IOS
Release 12.2(50)SE or later
The equivalent 802.1x commands in
Cisco IOS Release 12.2(46)SE and
earlier
Description
authentication port-control {auto dot1x port-control {auto |
| force-authorized | force-un
force-authorized |
authorized}
force-unauthorized}
Enable manual control of the authorization state of
the port.
authentication timer
Set the 802.1x timers.
dot1x timeout
authentication violation {protect | dot1x violation-mode {shutdown Configure the violation modes that occur when a
restrict | shutdown}
| restrict | protect}
new device connects to a port or when a new
device connects to a port after the maximum
number of devices are connected to that port.
show authentication
show dot1x
Display 802.1x statistics, administrative status,
and operational status for the switch or for the
specified port.
Beginning with Cisco IOS Release 12.2(55)SE, you can filter out verbose system messages generated
by the authentication manager. The filtered content typically relates to authentication success. You can
also filter verbose messages for 802.1x authentication and MAB authentication. There is a separate
command for each authentication method:
•
The no authentication logging verbose global configuration command filters verbose messages
from the authentication manager.
•
The no dot1x logging verbose global configuration command filters 802.1x authentication verbose
messages.
•
The no mab logging verbose global configuration command filters MAC authentication bypass
(MAB) verbose messages
For more information, see the command reference for this release.
Ports in Authorized and Unauthorized States
During IEEE 802.1x authentication, depending on the switch port state, the switch can grant a client
access to the network. The port starts in the unauthorized state. While in this state, the port that is not
configured as a voice VLAN port disallows all ingress and egress traffic except for IEEE 802.1x
authentication, CDP, and STP packets. When a client is successfully authenticated, the port changes to
the authorized state, allowing all traffic for the client to flow normally. If the port is configured as a voice
VLAN port, the port allows VoIP traffic and IEEE 802.1x protocol packets before the client is
successfully authenticated.
If a client that does not support IEEE 802.1x authentication connects to an unauthorized IEEE 802.1x
port, the switch requests the client’s identity. In this situation, the client does not respond to the request,
the port remains in the unauthorized state, and the client is not granted access to the network.
In contrast, when an IEEE 802.1x-enabled client connects to a port that is not running the IEEE 802.1x
standard, the client initiates the authentication process by sending the EAPOL-start frame. When no
response is received, the client sends the request for a fixed number of times. Because no response is
received, the client begins sending frames as if the port is in the authorized state.
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Understanding IEEE 802.1x Port-Based Authentication
You control the port authorization state by using the dot1x port-control interface configuration
command and these keywords:
•
force-authorized—disables IEEE 802.1x authentication and causes the port to change to the
authorized state without any authentication exchange required. The port sends and receives normal
traffic without IEEE 802.1x-based authentication of the client. This is the default setting.
•
force-unauthorized—causes the port to remain in the unauthorized state, ignoring all attempts by
the client to authenticate. The switch cannot provide authentication services to the client through the
port.
•
auto—enables IEEE 802.1x authentication and causes the port to begin in the unauthorized state,
allowing only EAPOL frames to be sent and received through the port. The authentication process
begins when the link state of the port changes from down to up or when an EAPOL-start frame is
received. The switch requests the identity of the client and begins relaying authentication messages
between the client and the authentication server. Each client attempting to access the network is
uniquely identified by the switch by using the client MAC address.
If the client is successfully authenticated (receives an Accept frame from the authentication server), the
port state changes to authorized, and all frames from the authenticated client are allowed through the
port. If the authentication fails, the port remains in the unauthorized state, but authentication can be
retried. If the authentication server cannot be reached, the switch can resend the request. If no response
is received from the server after the specified number of attempts, authentication fails, and network
access is not granted.
When a client logs off, it sends an EAPOL-logoff message, causing the switch port to change to the
unauthorized state.
If the link state of a port changes from up to down, or if an EAPOL-logoff frame is received, the port
returns to the unauthorized state.
802.1x Host Mode
You can configure an IEEE 802.1x port for single-host or for multiple-hosts mode. In single-host mode
(see Figure 8-1 on page 8-3), only one client can be connected to the IEEE 802.1x-enabled switch port.
The switch detects the client by sending an EAPOL frame when the port link state changes to the up
state. If a client leaves or is replaced with another client, the switch changes the port link state to down,
and the port returns to the unauthorized state.
In multiple-hosts mode, you can attach multiple hosts to a single IEEE 802.1x-enabled port. Figure 8-5
on page 8-13 shows IEEE 802.1x port-based authentication in a wireless LAN. In this mode, only one
of the attached clients must be authorized for all clients to be granted network access. If the port becomes
unauthorized (re-authentication fails or an EAPOL-logoff message is received), the switch denies
network access to all of the attached clients. In this topology, the wireless access point is responsible for
authenticating the clients attached to it, and it also acts as a client to the switch.
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Understanding IEEE 802.1x Port-Based Authentication
Figure 8-5
Multiple Host Mode Example
Access point
Authentication
server
(RADIUS)
101227
Wireless clients
Note
For all host modes, the line protocol stays up before authorization when port-based authentication is
configured.
802.1x Multiple Authentication Mode
Multiple-authentication (multiauth) mode allows one client on the voice VLAN and multiple
authenticated clients on the data VLAN. When a hub or access point is connected to an 802.1x-enabled
port, multiple-authentication mode provides enhanced security over multiple-hosts mode by requiring
authentication of each connected client. For non-802.1x devices, you can use MAC authentication
bypass or web authentication as the fallback method for individual host authentications to authenticate
different hosts through by different methods on a single port.
Multiple-authentication mode also supports MDA functionality on the voice VLAN by assigning
authenticated devices to either a data or voice VLAN, depending on the VSAs received from the
authentication server.
Note
When a port is in multiple-authentication mode, the guest VLAN and authentication-failed VLAN
features do not activate.
Beginning with Cisco IOS Release 12.2(55)SE, you can assign a RADIUS-server-supplied VLAN in
multi-auth mode, under these conditions:
•
The host is the first host authorized on the port, and the RADIUS server supplies VLAN information.
•
Subsequent hosts are authorized with a VLAN that matches the operational VLAN.
•
A host is authorized on the port with no VLAN assignment, and subsequent hosts either have no
VLAN assignment, or their VLAN information matches the operational VLAN.
•
The first host authorized on the port has a group VLAN assignment, and subsequent hosts either
have no VLAN assignment, or their group VLAN matches the group VLAN on the port. Subsequent
hosts must use the same VLAN from the VLAN group as the first host. If a VLAN list is used, all
hosts are subject to the conditions specified in the VLAN list.
•
Only one voice VLAN assignment is supported on a multi-auth port.
•
After a VLAN is assigned to a host on the port, subsequent hosts must have matching VLAN
information or be denied access to the port.
•
You cannot configure a guest VLAN or an auth-fail VLAN in multi-auth mode.
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Understanding IEEE 802.1x Port-Based Authentication
•
The behavior of the critical-auth VLAN is not changed for multi-auth mode. When a host tries to
authenticate and the server is not reachable, all authorized hosts are reinitialized in the configured
VLAN.
For more information about critical authentication mode and the critical VLAN, see the “802.1x
Authentication with Inaccessible Authentication Bypass” section on page 8-24.
For more information see the “Configuring the Host Mode” section on page 8-43.
MAC Move
When a MAC address is authenticated on one switch port, that address is not allowed on another
authentication manager-enabled port of the switch. If the switch detects that same MAC address on
another authentication manager-enabled port, the address is not allowed.
There are situations where a MAC address might need to move from one port to another on the same
switch. For example, when there is another device (for example a hub or an IP phone) between an
authenticated host and a switch port, you might want to disconnect the host from the device and connect
it directly to another port on the same switch.
You can globally enable MAC move so the device is reauthenticated on the new port. When a host moves
to a second port, the session on the first port is deleted, and the host is reauthenticated on the new port.
MAC move is supported on all host modes. (The authenticated host can move to any port on the switch,
no matter which host mode is enabled on the that port.)
When a MAC address moves from one port to another, the switch terminates the authenticated session
on the original port and initiates a new authentication sequence on the new port.
The MAC move feature applies to both voice and data hosts.
Note
In open authentication mode, a MAC address is immediately moved from the original port to the new
port, with no requirement for authorization on the new port.
For more information see the “Enabling MAC Move” section on page 8-44.
Multi-Domain Authentication (MDA) which allows both a data device and a voice device, such as an IP
Phone (Cisco or non-Cisco), to connect to the same switch port. For more information, see the “Using
Multidomain Authentication” section on page 8-30.
MAC Replace
Beginning with Cisco IOS Release 12.2(55)SE, the MAC replace feature can be configured to address
the violation that occurs when a host attempts to connect to a port where another host was previously
authenticated.
Note
This feature does not apply to ports in multi-auth mode, because violations are not triggered in that
mode. It does not apply to ports in multiple host mode, because in that mode, only the first host requires
authentication.
If you configure the authentication violation interface configuration command with the replace
keyword, the authentication process on a port in multi-domain mode is:
•
A new MAC address is received on a port with an existing authenticated MAC address.
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Understanding IEEE 802.1x Port-Based Authentication
•
The authentication manager replaces the MAC address of the current data host on the port with the
new MAC address.
•
The authentication manager initiates the authentication process for the new MAC address.
•
If the authentication manager determines that the new host is a voice host, the original voice host is
removed.
If a port is in open authentication mode, any new MAC address is immediately added to the MAC address
table.
For more information see the “Enabling MAC Replace” section on page 8-45.
802.1x Accounting
The 802.1x standard defines how users are authorized and authenticated for network access but does not
keep track of network usage. 802.1x accounting is disabled by default. You can enable 802.1x accounting
to monitor this activity on 802.1x-enabled ports:
•
User successfully authenticates.
•
User logs off.
•
Link-down occurs.
•
Re-authentication successfully occurs.
•
Re-authentication fails.
The switch does not log 802.1x accounting information. Instead, it sends this information to the
RADIUS server, which must be configured to log accounting messages.
802.1x Accounting Attribute-Value Pairs
The information sent to the RADIUS server is represented in the form of Attribute-Value (AV) pairs.
These AV pairs provide data for different applications. (For example, a billing application might require
information that is in the Acct-Input-Octets or the Acct-Output-Octets attributes of a RADIUS packet.)
AV pairs are automatically sent by a switch that is configured for 802.1x accounting. Three types of
RADIUS accounting packets are sent by a switch:
•
START–sent when a new user session starts
•
INTERIM–sent during an existing session for updates
•
STOP–sent when a session terminates
Table 8-3 lists the AV pairs and when they are sent by the switch:
Table 8-3
Accounting AV Pairs
Attribute Number
AV Pair Name
START
INTERIM
STOP
Attribute[1]
User-Name
Always
Always
Always
Attribute[4]
NAS-IP-Address
Always
Always
Always
Attribute[5]
NAS-Port
Always
Always
Attribute[8]
Framed-IP-Address
Never
Sometimes
Attribute[25]
Class
Always
Always
Always
1
Sometimes1
Always
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Understanding IEEE 802.1x Port-Based Authentication
Table 8-3
Accounting AV Pairs (continued)
Attribute Number
AV Pair Name
START
INTERIM
STOP
Attribute[30]
Called-Station-ID
Always
Always
Always
Attribute[31]
Calling-Station-ID
Always
Always
Always
Attribute[40]
Acct-Status-Type
Always
Always
Always
Attribute[41]
Acct-Delay-Time
Always
Always
Always
Attribute[42]
Acct-Input-Octets
Never
Always
Always
Attribute[43]
Acct-Output-Octets
Never
Always
Always
Attribute[44]
Acct-Session-ID
Always
Always
Always
Attribute[45]
Acct-Authentic
Always
Always
Always
Attribute[46]
Acct-Session-Time
Never
Always
Always
Attribute[49]
Acct-Terminate-Cause
Never
Never
Always
Attribute[61]
NAS-Port-Type
Always
Always
Always
1. The Framed-IP-Address AV pair is sent only if a valid Dynamic Host Control Protocol (DHCP) binding
exists for the host in the DHCP snooping bindings table.
You can view the AV pairs that are being sent by the switch by entering the debug radius accounting
privileged EXEC command. For more information about this command, see the Cisco IOS Debug
Command Reference, Release 12.2 at this URL:
http://www.cisco.com/en/US/docs/ios/12_2/debug/command/reference/122debug.html
For more information about AV pairs, see RFC 3580, “IEEE 802.1X Remote Authentication Dial In User
Service (RADIUS) Usage Guidelines.”
802.1x Readiness Check
The 802.1x readiness check monitors 802.1x activity on all the switch ports and displays information
about the devices connected to the ports that support 802.1x. You can use this feature to determine if the
devices connected to the switch ports are 802.1x-capable. You use an alternate authentication such as
MAC authentication bypass or web authentication for the devices that do not support 802.1x
functionality.
This feature only works if the supplicant on the client supports a query with the NOTIFY EAP
notification packet. The client must respond within the 802.1x timeout value.
For information on configuring the switch for the 802.1x readiness check, see the .
802.1x Authentication with VLAN Assignment
The RADIUS server sends the VLAN assignment to configure the switch port. The RADIUS server
database maintains the username-to-VLAN mappings, assigning the VLAN based on the username of
the client connected to the switch port. You can use this feature to limit network access for certain users.
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When a voice device is authorized and the RADIUS server returned an authorized VLAN, the voice
VLAN on the port is configured to send and receive packets on the assigned voice VLAN. Voice VLAN
assignment behaves the same as data VLAN assignment on multidomain authentication (MDA)-enabled
ports. For more information, see the “Using Multidomain Authentication” section on page 8-30.
When configured on the switch and the RADIUS server, 802.1x authentication with VLAN assignment
has these characteristics:
•
If no VLAN is supplied by the RADIUS server or if 802.1x authentication is disabled, the port is
configured in its access VLAN after successful authentication. Recall that an access VLAN is a
VLAN assigned to an access port. All packets sent from or received on this port belong to this
VLAN.
•
If 802.1x authentication is enabled but the VLAN information from the RADIUS server is not valid,
the port returns to the unauthorized state and remains in the configured access VLAN. This prevents
ports from appearing unexpectedly in an inappropriate VLAN because of a configuration error.
Configuration errors could include specifying a VLAN for a routed port, a malformed VLAN ID, a
nonexistent or internal (routed port) VLAN ID, or an attempted assignment to a voice VLAN ID.
Configuration errors could include specifying a VLAN for a routed port, a malformed VLAN ID, a
nonexistent or internal (routed port) VLAN ID, an RSPAN VLAN, a shut down or suspended VLAN. In
the case of a mutlidomain host port, configuration errors can also be due to an attempted assignment of
a data VLAN that matches the configured or assigned voice VLAN ID (or the reverse).
•
If 802.1x authentication is enabled and all information from the RADIUS server is valid, the port is
placed in the specified VLAN after authentication.
•
If the multiple-hosts mode is enabled on an 802.1x port, all hosts are placed in the same VLAN
(specified by the RADIUS server) as the first authenticated host.
•
Enabling port security does not impact the RADIUS server-assigned VLAN behavior.
•
If 802.1x authentication is disabled on the port, it is returned to the configured access VLAN.
•
If an IEEE 802.1x port is authenticated and put in the RADIUS server-assigned VLAN, any change
to the port access VLAN configuration does not take effect. In the case of a multidomain host, the
same applies to voice devices when the port is fully authorized with these exceptions:
– If the VLAN configuration change of one device results in matching the other device configured
or assigned VLAN, then authorization of all devices on the port is terminated and multidomain
host mode is disabled until a valid configuration is restored where data and voice device
configured VLANs no longer match.
– If a voice device is authorized and is using a downloaded voice VLAN, the removal of the voice
VLAN configuration, or modifying the configuration value to dot1p or untagged results in voice
device un-authorization and the disablement of multi-domain host mode.
When the port is in the force authorized, force unauthorized, unauthorized, or shutdown state, it is put
into the configured access VLAN.
The 802.1x authentication with VLAN assignment feature is not supported on trunk ports, dynamic
ports, or with dynamic-access port assignment through a VLAN Membership Policy Server (VMPS).
To configure VLAN assignment you need to perform these tasks:
•
Enable AAA authorization by using the network keyword to allow interface configuration from the
RADIUS server.
•
Enable 802.1x authentication. (The VLAN assignment feature is automatically enabled when you
configure 802.1x authentication on an access port).
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•
Assign vendor-specific tunnel attributes in the RADIUS server. The RADIUS server must return
these attributes to the switch:
– [64] Tunnel-Type = VLAN
– [65] Tunnel-Medium-Type = 802
– [81] Tunnel-Private-Group-ID = VLAN name or VLAN ID
Attribute [64] must contain the value VLAN (type 13). Attribute [65] must contain the value 802
(type 6). Attribute [81] specifies the VLAN name or VLAN ID assigned to the
IEEE 802.1x-authenticated user.
For examples of tunnel attributes, see the “Configuring the Switch to Use Vendor-Specific RADIUS
Attributes” section on page 7-34.
802.1x Authentication with Per-User ACLs
You can enable per-user access control lists (ACLs) to provide different levels of network access and
service to an 802.1x-authenticated user. When the RADIUS server authenticates a user connected to
an 802.1x port, it retrieves the ACL attributes based on the user identity and sends them to the switch.
The switch applies the attributes to the 802.1x port for the duration of the user session. The switch
removes the per-user ACL configuration when the session is over, if authentication fails, or if a
link-down condition occurs. The switch does not save RADIUS-specified ACLs in the running
configuration. When the port is unauthorized, the switch removes the ACL from the port.
You can configure router ACLs and input port ACLs on the same switch. However, a port ACL takes
precedence over a router ACL. If you apply input port ACL to an interface that belongs to a VLAN, the
port ACL takes precedence over an input router ACL applied to the VLAN interface. Incoming packets
received on the port to which a port ACL is applied are filtered by the port ACL. Incoming routed packets
received on other ports are filtered by the router ACL. Outgoing routed packets are filtered by the router
ACL. To avoid configuration conflicts, you should carefully plan the user profiles stored on the RADIUS
server.
RADIUS supports per-user attributes, including vendor-specific attributes. These vendor-specific
attributes (VSAs) are in octet-string format and are passed to the switch during the authentication
process. The VSAs used for per-user ACLs are inacl#<n> for the ingress direction and outacl#<n> for
the egress direction. MAC ACLs are supported only in the ingress direction. The switch supports VSAs
only in the ingress direction. It does not support port ACLs in the egress direction on Layer 2 ports. For
more information, see Chapter 33, “Configuring Network Security with ACLs.”
Use only the extended ACL syntax style to define the per-user configuration stored on the RADIUS
server. When the definitions are passed from the RADIUS server, they are created by using the extended
naming convention. However, if you use the Filter-Id attribute, it can point to a standard ACL.
You can use the Filter-Id attribute to specify an inbound or outbound ACL that is already configured on
the switch. The attribute contains the ACL number followed by .in for ingress filtering or .out for egress
filtering. If the RADIUS server does not allow the .in or .out syntax, the access list is applied to the
outbound ACL by default. Because of limited support of Cisco IOS access lists on the switch, the
Filter-Id attribute is supported only for IP ACLs numbered 1 to 199 and 1300 to 2699 (IP standard and
IP extended ACLs).
Only one 802.1x-authenticated user is supported on a port. If the multiple-hosts mode is enabled on the
port, the per-user ACL attribute is disabled for the associated port.
The maximum size of the per-user ACL is 4000 ASCII characters but is limited by the maximum size of
RADIUS-server per-user ACLs.
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For examples of vendor-specific attributes, see the “Configuring the Switch to Use Vendor-Specific
RADIUS Attributes” section on page 7-34. For more information about configuring ACLs, see
Chapter 33, “Configuring Network Security with ACLs.”
To configure per-user ACLs:
•
Enable AAA authentication.
•
Enable AAA authorization by using the network keyword to allow interface configuration from the
RADIUS server.
•
Enable 802.1x authentication.
•
Configure the user profile and VSAs on the RADIUS server.
•
Configure the 802.1x port for single-host mode.
Note
Per-user ACLs are supported only in single-host mode.
802.1x Authentication with Downloadable ACLs and Redirect URLs
You can download ACLs and redirect URLs from a RADIUS server to the switch during 802.1x
authentication or MAC authentication bypass of the host. You can also download ACLs during web
authentication.
Note
A downloadable ACL is also referred to as a dACL.
If more than one host is authenticated and the host is in single-host, MDA, or multiple-authentication
mode, the switch changes the source address of the ACL to the host IP address.
You can apply the ACLs and redirect URLs to all the devices connected to the 802.1x-enabled port.
If no ACLs are downloaded during 802.1x authentication, the switch applies the static default ACL on
the port to the host. On a voice VLAN port, the switch applies the ACL only to the phone.
Beginning with Cisco IOS Release 12.2(55)SE, if there is no static ACL on a port, a dynamic
auth-default ACL is created, and policies are enforced before dACLs are downloaded and applied.
Note
The auth-default-ACL does not appear in the running configuration.
The auth-default ACL is created when at least one host with an authorization policy is detected on the
port. The auth-default ACL is removed from the port when the last authenticated session ends. You can
configure the auth-default ACL by using the ip access-list extended auth-default-acl global
configuration command.
Note
The auth-default-ACL does not support Cisco Discovery Protocol (CDP) bypass in the single host mode.
You must configure a static ACL on the interface to support CDP bypass.
The 802.1x and MAB authentication methods support two authentication modes, open and closed. If
there is no static ACL on a port in closed authentication mode:
•
An auth-default-ACL is created.
•
The auth-default-ACL allows only DHCP traffic until policies are enforced.
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•
When the first host authenticates, the authorization policy is applied without IP address insertion.
•
When a second host is detected, the policies for the first host are refreshed, and policies for the first
and subsequent sessions are enforced with IP address insertion.
If there is no static ACL on a port in open authentication mode:
•
An auth-default-ACL-OPEN is created and allows all traffic.
•
Policies are enforced with IP address insertion to prevent security breaches.
•
Web authentication is subject to the auth-default-ACL-OPEN.
To control access for hosts with no authorization policy, you can configure a directive. The supported
values for the directive are open and default. When you configure the open directive, all traffic is
allowed. The default directive subjects traffic to the access provided by the port. You can configure the
directive either in the user profile on the AAA server or on the switch. To configure the directive on the
AAA server, use the authz-directive =<open/default> global command. To configure the directive on
the switch, use the epm access-control open global configuration command.
Note
The default value of the directive is default.
If a host falls back to web authentication on a port without a configured ACL:
•
If the port is in open authentication mode, the auth-default-ACL-OPEN is created.
•
If the port is in closed authentication mode, the auth-default-ACL is created.
The access control entries (ACEs) in the fallback ACL are converted to per-user entries. If the configured
fallback profile does not include a fallback ACL, the host is subject to the auth-default-ACL associated
with the port.
Note
If you use a custom logo with web authentication and it is stored on an external server, the port ACL
must allow access to the external server before authentication. You must either configure a static port
ACL or change the auth-default-ACL to provide appropriate access to the external server.
Cisco Secure ACS and Attribute-Value Pairs for the Redirect URL
The switch uses these cisco-av-pair VSAs:
•
url-redirect is the HTTP to HTTPS URL.
•
url-redirect-acl is the switch ACL name or number.
The switch uses the CiscoSecure-Defined-ACL AV pair to intercept an HTTP or HTTPS request from
the endpoint device. The switch then forwards the client web browser to the specified redirect address.
The url-redirect AV pair on the Cisco Secure ACS contains the URL to which the web browser is
redirected. The url-redirect-acl AV pair contains the name or number of an ACL that specifies the HTTP
or HTTPS traffic to redirect. Traffic that matches a permit ACE in the ACL is redirected.
Note
Define the URL redirect ACL and the default port ACL on the switch.
If a redirect URL configured for a client on the authentication server, a default port ACL on the
connected client switch port must also be configured
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Cisco Secure ACS and Attribute-Value Pairs for Downloadable ACLs
You can set the CiscoSecure-Defined-ACL Attribute-Value (AV) pair on the Cisco Secure ACS with the
RADIUS cisco-av-pair vendor-specific attributes (VSAs). This pair specifies the names of the
downloadable ACLs on the Cisco Secure ACS with the #ACL#-IP-name-number attribute.
•
The name is the ACL name.
•
The number is the version number (for example, 3f783768).
If a downloadable ACL is configured for a client on the authentication server, a default port ACL on the
connected client switch port must also be configured.
If the default ACL is configured on the switch and the Cisco Secure ACS sends a host-access-policy to
the switch, it applies the policy to traffic from the host connected to a switch port. If the policy does not
apply, the switch applies the default ACL. If the Cisco Secure ACS sends the switch a downloadable
ACL, this ACL takes precedence over the default ACL that is configured on the switch port. However,
if the switch receives an host access policy from the Cisco Secure ACS but the default ACL is not
configured, the authorization failure is declared.
For configuration details, see the ““Authentication Manager” section on page 8-8 and the “Configuring
802.1x Authentication with Downloadable ACLs and Redirect URLs” section on page 8-61.
VLAN ID-based MAC Authentication
You can use VLAN ID-based MAC authentication if you wish to authenticate hosts based on a static
VLAN ID instead of a downloadable VLAN. When you have a static VLAN policy configured on your
switch, VLAN information is sent to an IAS (Microsoft) RADIUS server along with the MAC address
of each host for authentication. The VLAN ID configured on the connected port is used for MAC
authentication. By using VLAN ID-based MAC authentication with an IAS server, you can have a fixed
number of VLANs in the network.
The feature also limits the number of VLANs monitored and handled by STP.The network can be
managed as a fixed VLAN.
Note
This feature is not supported on Cisco ACS Server. (The ACS server ignores the sent VLAN-IDs for new
hosts and only authenticates based on the MAC address.)
For configuration information, see the “Configuring VLAN ID-based MAC Authentication” section on
page 8-64. Additional configuration is similar MAC authentication bypass, as described in the
“Configuring MAC Authentication Bypass” section on page 8-57.
802.1x Authentication with Guest VLAN
You can configure a guest VLAN for each 802.1x port on the switch to provide limited services to
clients, such as downloading the 802.1x client. These clients might be upgrading their system for 802.1x
authentication, and some hosts, such as Windows 98 systems, might not be IEEE 802.1x-capable.
When you enable a guest VLAN on an 802.1x port, the switch assigns clients to a guest VLAN when the
switch does not receive a response to its EAP request/identity frame or when EAPOL packets are not
sent by the client. The port is automatically set to multi-host mode.
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The switch maintains the EAPOL packet history. If an EAPOL packet is detected on the interface during
the lifetime of the link, the switch determines that the device connected to that interface is an
IEEE 802.1x-capable supplicant, and the interface does not change to the guest VLAN state. EAPOL
history is cleared if the interface link status goes down. If no EAPOL packet is detected on the interface,
the interface changes to the guest VLAN state.
If the switch is trying to authorize an 802.1x-capable voice device and the AAA server is unavailable,
the authorization attempt fails, but the detection of the EAPOL packet is saved in the EAPOL history.
When the AAA server becomes available, the switch authorizes the voice device. However, the switch
no longer allows other devices access to the guest VLAN.
To prevent this situation, use one of these command sequences:
•
Enter the authentication event no-response action authorize vlan vlan-id interface configuration
command to allow access to the guest VLAN.
•
Enter the shutdown interface configuration command followed by the no shutdown interface
configuration command to restart the port.
If devices send EAPOL packets to the switch during the lifetime of the link, the switch does not allow
clients that fail authentication access to the guest VLAN.
Note
If an EAPOL packet is detected after the interface has changed to the guest VLAN, the interface reverts
to an unauthorized state, and 802.1x authentication restarts.
Any number of 802.1x-incapable clients are allowed access when the switch port is moved to the guest
VLAN. If an 802.1x-capable client joins the same port on which the guest VLAN is configured, the port
is put into the unauthorized state in the user-configured access VLAN, and authentication is restarted.
Guest VLANs are supported on 802.1x ports in single host, multiple host, or multi-domain modes.
You can configure any active VLAN except an RSPAN VLAN, a private VLAN, or a voice VLAN as an
802.1x guest VLAN. The guest VLAN feature is not supported on internal VLANs (routed ports) or
trunk ports; it is supported only on access ports.
The switch supports MAC authentication bypass in Cisco IOS Release 12.2(25)SEE and later. When
MAC authentication bypass is enabled on an 802.1x port, the switch can authorize clients based on the
client MAC address when IEEE 802.1x authentication times out while waiting for an EAPOL message
exchange. After detecting a client on an 802.1x port, the switch waits for an Ethernet packet from the
client. The switch sends the authentication server a RADIUS-access/request frame with a username and
password based on the MAC address. If authorization succeeds, the switch grants the client access to the
network. If authorization fails, the switch assigns the port to the guest VLAN if one is specified. For
more information, see the“802.1x Authentication with MAC Authentication Bypass” section on
page 8-27.
For more information, see the “Configuring a Guest VLAN” section on page 8-50.
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Configuring IEEE 802.1x Port-Based Authentication
Understanding IEEE 802.1x Port-Based Authentication
802.1x Authentication with Restricted VLAN
You can configure a restricted VLAN (also referred to as an authentication failed VLAN) for each
IEEE 802.1x port on a switch to provide limited services to clients that cannot access the guest VLAN.
These clients are 802.1x-compliant and cannot access another VLAN because they fail the
authentication process. A restricted VLAN allows users without valid credentials in an authentication
server (typically, visitors to an enterprise) to access a limited set of services. The administrator can
control the services available to the restricted VLAN.
Note
You can configure a VLAN to be both the guest VLAN and the restricted VLAN if you want to provide
the same services to both types of users.
Without this feature, the client attempts and fails authentication indefinitely, and the switch port remains
in the spanning-tree blocking state. With this feature, you can configure the switch port to be in the
restricted VLAN after a specified number of authentication attempts (the default value is 3 attempts).
The authenticator counts the failed authentication attempts for the client. When this count exceeds the
configured maximum number of authentication attempts, the port moves to the restricted VLAN. The
failed attempt count increments when the RADIUS server replies with either an EAP failure or an empty
response without an EAP packet. When the port moves into the restricted VLAN, the failed attempt
counter resets.
Users who fail authentication remain in the restricted VLAN until the next re-authentication attempt. A
port in the restricted VLAN tries to re-authenticate at configured intervals (the default is 60 seconds). If
re-authentication fails, the port remains in the restricted VLAN. If re-authentication is successful, the
port moves either to the configured VLAN or to a VLAN sent by the RADIUS server. You can disable
re-authentication. If you do this, the only way to restart the authentication process is for the port to
receive a link down or EAP logoff event. We recommend that you keep re-authentication enabled if a
client might connect through a hub. When a client disconnects from the hub, the port might not receive
the link down or EAP logoff event.
After a port moves to the restricted VLAN, a simulated EAP success message is sent to the client. This
prevents clients from indefinitely attempting authentication. Some clients (for example, devices running
Windows XP) cannot implement DHCP without EAP success.
Restricted VLANs are supported only on 802.1x ports in single-host mode and on Layer 2 ports.
You can configure any active VLAN except an RSPAN VLAN, a primary private VLAN, or a voice
VLAN as an 802.1x restricted VLAN. The restricted VLAN feature is not supported on internal VLANs
(routed ports) or trunk ports; it is supported only on access ports.
Other security features such as dynamic ARP Inspection, DHCP snooping, and IP source guard can be
configured independently on a restricted VLAN.
For more information, see the “Configuring a Restricted VLAN” section on page 8-51.
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Understanding IEEE 802.1x Port-Based Authentication
802.1x Authentication with Inaccessible Authentication Bypass
Use the inaccessible authentication bypass feature, also referred to as critical authentication or the AAA
fail policy, when the switch cannot reach the configured RADIUS servers and new hosts cannot be
authenticated. You can configure the switch to connect those hosts to critical ports.
When a new host tries to connect to the critical port, that host is moved to a user-specified access VLAN,
the critical VLAN. The administrator gives limited authentication to the hosts.
When the switch tries to authenticate a host connected to a critical port, the switch checks the status of
the configured RADIUS server. If a server is available, the switch can authenticate the host. However, if
all the RADIUS servers are unavailable, the switch grants network access to the host and puts the port
in the critical-authentication state, which is a special case of the authentication state.
Support on Multiple-Authentication Ports
When a port is configured on any host mode and the AAA server is unavailable, the port is then
configured to multi-host mode and moved to the critical VLAN. To support this inaccessible bypass on
multiple-authentication (multiauth) ports, use the authentication event server dead action reinitialize
vlan vlan-id command. When a new host tries to connect to the critical port, that port is reinitialized and
all the connected hosts are moved to the user-specified access VLAN.
This command is supported on all host modes.
Authentication Results
The behavior of the inaccessible authentication bypass feature depends on the authorization state of the
port:
•
If the port is unauthorized when a host connected to a critical port tries to authenticate and all servers
are unavailable, the switch puts the port in the critical-authentication state in the
RADIUS-configured or user-specified access VLAN.
•
If the port is already authorized and reauthentication occurs, the switch puts the critical port in the
critical-authentication state in the current VLAN, which might be the one previously assigned by
the RADIUS server.
•
If the RADIUS server becomes unavailable during an authentication exchange, the current exchange
times out, and the switch puts the critical port in the critical-authentication state during the next
authentication attempt.
You can configure the critical port to reinitialize hosts and move them out of the critical VLAN when
the RADIUS server is again available. When this is configured, all critical ports in the
critical-authentication state are automatically re-authenticated. For more information, see the command
reference for this release and the “Configuring the Inaccessible Authentication Bypass Feature” section
on page 8-53.
Feature Interactions
Inaccessible authentication bypass interacts with these features:
•
Guest VLAN—Inaccessible authentication bypass is compatible with guest VLAN. When a guest
VLAN is enabled on 8021.x port, the features interact as follows:
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Understanding IEEE 802.1x Port-Based Authentication
– If at least one RADIUS server is available, the switch assigns a client to a guest VLAN when
the switch does not receive a response to its EAP request/identity frame or when EAPOL
packets are not sent by the client.
– If all the RADIUS servers are not available and the client is connected to a critical port, the
switch authenticates the client and puts the critical port in the critical-authentication state in the
RADIUS-configured or user-specified access VLAN.
– If all the RADIUS servers are not available and the client is not connected to a critical port, the
switch might not assign clients to the guest VLAN if one is configured.
– If all the RADIUS servers are not available and if a client is connected to a critical port and was
previously assigned to a guest VLAN, the switch keeps the port in the guest VLAN.
•
Restricted VLAN—If the port is already authorized in a restricted VLAN and the RADIUS servers
are unavailable, the switch puts the critical port in the critical-authentication state in the restricted
VLAN.
•
802.1x accounting—Accounting is not affected if the RADIUS servers are unavailable.
•
Private VLAN—You can configure inaccessible authentication bypass on a private VLAN host port.
The access VLAN must be a secondary private VLAN.
•
Voice VLAN—Inaccessible authentication bypass is compatible with voice VLAN, but the
RADIUS-configured or user-specified access VLAN and the voice VLAN must be different.
•
Remote Switched Port Analyzer (RSPAN)—Do not configure an RSPAN VLAN as the
RADIUS-configured or user-specified access VLAN for inaccessible authentication bypass.
802.1x User Distribution
You can configure 802.1x user distribution to load-balance users with the same group name across
multiple different VLANs.
The VLANs are either supplied by the RADIUS server or configured through the switch CLI under a
VLAN group name.
•
Configure the RADIUS server to send more than one VLAN name for a user. The multiple VLAN
names can be sent as part of the response to the user. The 802.1x user distribution tracks all the users
in a particular VLAN and achieves load balancing by moving the authorized user to the least
populated VLAN.
•
Configure the RADIUS server to send a VLAN group name for a user. The VLAN group name can
be sent as part of the response to the user. You can search for the selected VLAN group name among
the VLAN group names that you configured by using the switch CLI. If the VLAN group name is
found, the corresponding VLANs under this VLAN group name are searched to find the least
populated VLAN. Load balancing is achieved by moving the corresponding authorized user to that
VLAN.
Note
The RADIUS server can send the VLAN information in any combination of VLAN-IDs, VLAN
names, or VLAN groups.
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802.1x User Distribution Configuration Guidelines
•
Confirm that at least one VLAN is mapped to the VLAN group.
•
You can map more than one VLAN to a VLAN group.
•
You can modify the VLAN group by adding or deleting a VLAN.
•
When you clear an existing VLAN from the VLAN group name, none of the authenticated ports in
the VLAN are cleared, but the mappings are removed from the existing VLAN group.
•
If you clear the last VLAN from the VLAN group name, the VLAN group is cleared.
•
You can clear a VLAN group even when the active VLANs are mapped to the group. When you clear
a VLAN group, none of the ports or users that are in the authenticated state in any VLAN within the
group are cleared, but the VLAN mappings to the VLAN group are cleared.
For more information, see the “Configuring 802.1x User Distribution” section on page 8-56.
802.1x Authentication with Voice VLAN Ports
A voice VLAN port is a special access port associated with two VLAN identifiers:
•
VVID to carry voice traffic to and from the IP phone. The VVID is used to configure the IP phone
connected to the port.
•
PVID to carry the data traffic to and from the workstation connected to the switch through the IP
phone. The PVID is the native VLAN of the port.
The IP phone uses the VVID for its voice traffic, regardless of the authorization state of the port. This
allows the phone to work independently of IEEE 802.1x authentication.
In single-host mode, only the IP phone is allowed on the voice VLAN. In multiple-hosts mode,
additional clients can send traffic on the voice VLAN after a supplicant is authenticated on the PVID.
When multiple-hosts mode is enabled, the supplicant authentication affects both the PVID and the
VVID.
A voice VLAN port becomes active when there is a link, and the device MAC address appears after the
first CDP message from the IP phone. Cisco IP phones do not relay CDP messages from other devices.
As a result, if several IP phones are connected in series, the switch recognizes only the one directly
connected to it. When 802.1x authentication is enabled on a voice VLAN port, the switch drops packets
from unrecognized IP phones more than one hop away.
When 802.1x authentication is enabled on a port, you cannot configure a port VLAN that is equal to a
voice VLAN.
Note
If you enable 802.1x authentication on an access port on which a voice VLAN is configured and to which
a Cisco IP Phone is connected, the Cisco IP phone loses connectivity to the switch for up to 30 seconds.
For more information about voice VLANs, see Chapter 14, “Configuring Voice VLAN.”
802.1x Authentication with Port Security
In general, Cisco does not recommend enabling port security when IEEE 802.1x is enabled. Since IEEE
802.1x enforces a single MAC address per port (or per VLAN when MDA is configured for IP
telephony), port security is redundant and in some cases may interfere with expected IEEE 802.1x
operations.
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Understanding IEEE 802.1x Port-Based Authentication
802.1x Authentication with Wake-on-LAN
The 802.1x authentication with wake-on-LAN (WoL) feature allows dormant PCs to be powered when
the switch receives a specific Ethernet frame, known as the magic packet. You can use this feature in
environments where administrators need to connect to systems that have been powered down.
When a host that uses WoL is attached through an 802.1x port and the host powers off, the IEEE 802.1x
port becomes unauthorized. The port can only receive and send EAPOL packets, and WoL magic packets
cannot reach the host. When the PC is powered off, it is not authorized, and the switch port is not opened.
When the switch uses 802.1x authentication with WoL, the switch forwards traffic to unauthorized
IEEE 802.1x ports, including magic packets. While the port is unauthorized, the switch continues to
block ingress traffic other than EAPOL packets. The host can receive packets but cannot send packets to
other devices in the network.
Note
If PortFast is not enabled on the port, the port is forced to the bidirectional state.
When you configure a port as unidirectional by using the dot1x control-direction in interface
configuration command, the port changes to the spanning-tree forwarding state. The port can send
packets to the host but cannot receive packets from the host.
When you configure a port as bidirectional by using the dot1x control-direction both interface
configuration command, the port is access-controlled in both directions. The port does not receive
packets from or send packets to the host.
802.1x Authentication with MAC Authentication Bypass
You can configure the switch to authorize clients based on the client MAC address (see Figure 8-2 on
page 8-5) by using the MAC authentication bypass feature. For example, you can enable this feature on
IEEE 802.1x ports connected to devices such as printers.
If 802.1x authentication times out while waiting for an EAPOL response from the client, the switch tries
to authorize the client by using MAC authentication bypass.
When the MAC authentication bypass feature is enabled on an 802.1x port, the switch uses the MAC
address as the client identity. The authentication server has a database of client MAC addresses that are
allowed network access. After detecting a client on an 802.1x port, the switch waits for an Ethernet
packet from the client. The switch sends the authentication server a RADIUS-access/request frame with
a username and password based on the MAC address. If authorization succeeds, the switch grants the
client access to the network. If authorization fails, the switch assigns the port to the guest VLAN if one
is configured.
If an EAPOL packet is detected on the interface during the lifetime of the link, the switch determines
that the device connected to that interface is an 802.1x-capable supplicant and uses 802.1x
authentication (not MAC authentication bypass) to authorize the interface. EAPOL history is cleared if
the interface link status goes down.
If the switch already authorized a port by using MAC authentication bypass and detects an 802.1x
supplicant, the switch does not unauthorize the client connected to the port. When re-authentication
occurs, the switch uses 802.1x authentication as the preferred re-authentication process if the previous
session ended because the Termination-Action RADIUS attribute value is DEFAULT.
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Clients that were authorized with MAC authentication bypass can be re-authenticated. The
re-authentication process is the same as that for clients that were authenticated with 802.1x. During
re-authentication, the port remains in the previously assigned VLAN. If re-authentication is successful,
the switch keeps the port in the same VLAN. If re-authentication fails, the switch assigns the port to the
guest VLAN, if one is configured.
If re-authentication is based on the Session-Timeout RADIUS attribute (Attribute[27]) and the
Termination-Action RADIUS attribute (Attribute [29]) and if the Termination-Action RADIUS attribute
(Attribute [29]) action is Initialize, (the attribute value is DEFAULT), the MAC authentication bypass
session ends, and connectivity is lost during re-authentication. If MAC authentication bypass is enabled
and the 802.1x authentication times out, the switch uses the MAC authentication bypass feature to
initiate re-authorization. For more information about these AV pairs, see RFC 3580, “802.1x Remote
Authentication Dial In User Service (RADIUS) Usage Guidelines.”
MAC authentication bypass interacts with the features:
•
802.1x authentication—You can enable MAC authentication bypass only if 802.1x authentication is
enabled on the port.
•
Guest VLAN—If a client has an invalid MAC address identity, the switch assigns the client to a
guest VLAN if one is configured.
•
Restricted VLAN—This feature is not supported when the client connected to an IEEE 802.lx port
is authenticated with MAC authentication bypass.
•
Port security—See the “802.1x Authentication with Port Security” section on page 8-26.
•
Voice VLAN—See the “802.1x Authentication with Voice VLAN Ports” section on page 8-26.
•
VLAN Membership Policy Server (VMPS)—IEEE802.1x and VMPS are mutually exclusive.
•
Private VLAN—You can assign a client to a private VLAN.
•
Network admission control (NAC) Layer 2 IP validation—This feature takes effect after an
IEEE 802.1x port is authenticated with MAC authentication bypass, including hosts in the exception
list.
•
Network Edge Access Topology (NEAT)—MAB and NEAT are mutually exclusive. You cannot
enable MAB when NEAT is enabled on an interface, and you cannot enable NEAT when MAB is
enabled on an interface.
For more configuration information, see the “Authentication Manager” section on page 8-8.
Cisco IOS Release 12.2(55)SE and later supports filtering of verbose MAB system messages. See the
“Authentication Manager CLI Commands” section on page 8-10.
Network Admission Control Layer 2 802.1x Validation
In Cisco IOS Release 12.2(44)SE and later, the switch supports the Network Admission Control (NAC)
Layer 2 802.1x validation, which checks the antivirus condition or posture of endpoint systems or clients
before granting the devices network access. With NAC Layer 2 802.1x validation, you can do these tasks:
•
Download the Session-Timeout RADIUS attribute (Attribute[27]) and the Termination-Action
RADIUS attribute (Attribute[29]) from the authentication server.
•
Set the number of seconds between re-authentication attempts as the value of the Session-Timeout
RADIUS attribute (Attribute[27]) and get an access policy against the client from the RADIUS
server.
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•
Set the action to be taken when the switch tries to re-authenticate the client by using the
Termination-Action RADIUS attribute (Attribute[29]). If the value is the DEFAULT or is not set, the
session ends. If the value is RADIUS-Request, the re-authentication process starts.
•
View the NAC posture token, which shows the posture of the client, by using the show dot1x
privileged EXEC command.
•
Configure secondary private VLANs as guest VLANs.
Configuring NAC Layer 2 802.1x validation is similar to configuring 802.1x port-based authentication
except that you must configure a posture token on the RADIUS server. For information about
configuring NAC Layer 2 802.1x validation, see the “Configuring NAC Layer 2 802.1x Validation”
section on page 8-58 and the “Configuring Periodic Re-Authentication” section on page 8-45.
For more information about NAC, see the Network Admission Control Software Configuration Guide.
For more configuration information, see the “Authentication Manager” section on page 8-8.
Flexible Authentication Ordering
You can use flexible authentication ordering to configure the order of methods that a port uses to
authenticate a new host. MAC authentication bypass and 802.1x can be the primary or secondary
authentication methods, and web authentication can be the fallback method if either or both of those
authentication attempts fail. For more information see the “Configuring Flexible Authentication
Ordering” section on page 8-64.
Open1x Authentication
Open1x authentication allows a device access to a port before that device is authenticated. When open
authentication is configured, a new host can pass traffic according to the access control list (ACL)
defined on the port. After the host is authenticated, the policies configured on the RADIUS server are
applied to that host.
You can configure open authentication with these scenarios:
•
Single-host mode with open authentication–Only one user is allowed network access before and
after authentication.
•
MDA mode with open authentication–Only one user in the voice domain and one user in the data
domain are allowed.
•
Multiple-hosts mode with open authentication–Any host can access the network.
•
Multiple-authentication mode with open authentication–Similar to MDA, except multiple hosts can
be authenticated.
For more information see the “Configuring the Host Mode” section on page 8-43.
Note
If open authentication is configured, it takes precedence over other authentication controls. This means
that if you use the authentication open interface configuration command, the port will grant access to
the host irrespective of the authentication port-control interface configuration command.
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Using Multidomain Authentication
The switch supports multidomain authentication (MDA), which allows both a data device and voice
device, such as an IP phone (Cisco or non-Cisco), to authenticate on the same switch port. The port is
divided into a data domain and a voice domain.
MDA does not enforce the order of device authentication. However, for best results, we recommend that
a voice device is authenticated before a data device on an MDA-enabled port.
Follow these guidelines for configuring MDA:
•
To configure a switch port for MDA, see the “Configuring the Host Mode” section on page 8-43.
•
You must configure the voice VLAN for the IP phone when the host mode is set to multidomain. For
more information, see Chapter 14, “Configuring Voice VLAN.”
•
Voice VLAN assignment on an MDA-enabled port is supported in Cisco IOS Release 12.2(40)SE
and later.
•
To authorize a voice device, the AAA server must be configured to send a Cisco Attribute-Value
(AV) pair attribute with a value of device-traffic-class=voice. Without this value, the switch
treats the voice device as a data device.
•
The guest VLAN and restricted VLAN features only apply to the data devices on an MDA-enabled
port. The switch treats a voice device that fails authorization as a data device.
•
If more than one device attempts authorization on either the voice or the data domain of a port, it is
error disabled.
•
Until a device is authorized, the port drops its traffic. Non-Cisco IP phones or voice devices are
allowed into both the data and voice VLANs. The data VLAN allows the voice device to contact a
DHCP server to obtain an IP address and acquire the voice VLAN information. After the voice
device starts sending on the voice VLAN, its access to the data VLAN is blocked.
•
A voice device MAC address that is binding on the data VLAN is not counted towards the port
security MAC address limit.
•
You can use dynamic VLAN assignment from a RADIUS server only for data devices.
•
MDA can use MAC authentication bypass as a fallback mechanism to allow the switch port to
connect to devices that do not support IEEE 802.1x authentication. For more information, see the
“MAC Authentication Bypass” section on page 8-37.
•
When a data or a voice device is detected on a port, its MAC address is blocked until authorization
succeeds. If the authorization fails, the MAC address remains blocked for 5 minutes.
•
If more than five devices are detected on the data VLAN or more than one voice device is detected
on the voice VLAN while a port is unauthorized, the port is error disabled.
•
When a port host mode is changed from single- or multihost to multidomain mode, an authorized
data device remains authorized on the port. However, a Cisco IP phone that has been allowed on the
port voice VLAN is automatically removed and must be reauthenticated on that port.
•
Active fallback mechanisms such as guest VLAN and restricted VLAN remain configured after a
port changes from single- or multihost mode to multidomain mode.
•
Switching a port host mode from multidomain to single- or multihost mode removes all authorized
devices from the port.
•
If a data domain is authorized first and placed in the guest VLAN, non-IEEE 802.1x-capable voice
devices need to tag their packets on the voice VLAN to trigger authentication.
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•
We do not recommend per-user ACLs with an MDA-enabled port. An authorized device with a
per-user ACL policy might impact traffic on both the voice and data VLANs of the port. If used,
only one device on the port should enforce per-user ACLs.
Voice Aware 802.1x Security
You use the voice aware 802.1x security feature to configure the switch to disable only the VLAN on
which a security violation occurs, whether it is a data or voice VLAN. In previous releases, when an
attempt to authenticate the data client caused a security violation, the entire port shut down, resulting in
a complete loss of connectivity.
You can use this feature in IP phone deployments where a PC is connected to the IP phone. A security
violation found on the data VLAN results in the shutdown of only the data VLAN. The traffic on the
voice VLAN flows through the switch without interruption.
For information on configuring voice aware 802.1x security, see the .
802.1x Supplicant and Authenticator Switches with Network Edge Access
Topology (NEAT)
The Network Edge Access Topology (NEAT) feature extends identity to areas outside the wiring closet
(such as conference rooms). This allows any type of device to authenticate on the port.
•
802.1x switch supplicant: You can configure a switch to act as a supplicant to another switch by
using the 802.1x supplicant feature. This configuration is helpful in a scenario, where, for example,
a switch is outside a wiring closet and is connected to an upstream switch through a trunk port. A
switch configured with the 802.1x switch supplicant feature authenticates with the upstream switch
for secure connectivity.
Once the supplicant switch authenticates successfully the port mode changes from access to trunk.
•
If the access VLAN is configured on the authenticator switch, it becomes the native VLAN for the
trunk port after successful authentication.
You can enable MDA or multiauth mode on the authenticator switch interface that connects to one more
supplicant switches. Multihost mode is not supported on the authenticator switch interface.
Use the dot1x supplicant force-multicast global configuration command on the supplicant switch for
Network Edge Access Topology (NEAT) to work in all host modes.
•
Host Authorization: Ensures that only traffic from authorized hosts (connecting to the switch with
supplicant) is allowed on the network. The switches use Client Information Signalling Protocol
(CISP) to send the MAC addresses connecting to the supplicant switch to the authenticator switch,
as shown in Figure 8-6.
•
Auto Enablement: Automatically enables trunk configuration on the authenticator switch, allowing
user traffic from multiple VLANs coming from supplicant switches. Configure the cisco-av-pair as
device-traffic-class=switch at the ACS. (You can configure this under the group or the user settings.)
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Figure 8-6
Authenticator and Supplicant Switch using CISP
2
4
3
1
205718
5
1
Workstations (clients)
2
Supplicant switch (outside wiring closet)
3
Authenticator switch
4
Access control server (ACS)
5
Trunk port
•
You can configure NEAT ports with the same configurations as the other authentication ports. When
the supplicant switch authenticates, the port mode is changed from access to trunk based on the
switch vendor-specific attributes (VSAs). (device-traffic-class=switch).
•
The VSA changes the authenticator switch port mode from access to trunk and enables 802.1x trunk
encapsulation and the access VLAN if any would be converted to a native trunk VLAN. VSA does
not change any of the port configurations on the supplicant
•
To change the host mode and the apply a standard port configuration on the authenticator switch
port, you can also use AutoSmart ports user-defined macros, instead of the switch VSA. This allows
you to remove unsupported configurations on the authenticator switch port and to change the port
mode from access to trunk. For more information, see Chapter 11, “Configuring Smartports
Macros”.
Guidelines
For more information, see the “Configuring an Authenticator and a Supplicant Switch with NEAT”
section on page 8-60.
Common Session ID
Authentication manager uses a single session ID (referred to as a common session ID) for a client no
matter which authentication method is used. This ID is used for all reporting purposes, such as the show
commands and MIBs. The session ID appears with all per-session syslog messages.
The session ID includes:
•
The IP address of the Network Access Device (NAD)
•
A monotonically increasing unique 32 bit integer
•
The session start time stamp (a 32 bit integer)
This example shows how the session ID appears in the output of the show authentication command. The
session ID in this example is 160000050000000B288508E5:
Switch# show authentication sessions
Interface MAC Address
Method
Domain
Status
Session ID
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Configuring 802.1x Authentication
Fa4/0/4
0000.0000.0203
mab
DATA
Authz Success
160000050000000B288508E5
This is an example of how the session ID appears in the syslog output. The session ID in this example
is also160000050000000B288508E5:
1w0d: %AUTHMGR-5-START: Starting 'mab' for client (0000.0000.0203) on Interface Fa4/0/4
AuditSessionID 160000050000000B288508E5
1w0d: %MAB-5-SUCCESS: Authentication successful for client (0000.0000.0203) on Interface
Fa4/0/4 AuditSessionID 160000050000000B288508E5
1w0d: %AUTHMGR-7-RESULT: Authentication result 'success' from 'mab' for client
(0000.0000.0203) on Interface Fa4/0/4 AuditSessionID 160000050000000B288508E5
The session ID is used by the NAD, the AAA server, and other report-analyzing applications to identify
the client. The ID appears automatically. No configuration is required.
Configuring 802.1x Authentication
These sections contain this configuration information:
•
Default 802.1x Authentication Configuration, page 8-34
•
802.1x Authentication Configuration Guidelines, page 8-35
•
Configuring 802.1x Authentication, page 8-41 (required)
•
Configuring the Switch-to-RADIUS-Server Communication, page 8-42 (required)
•
Configuring Voice Aware 802.1x Security, page 8-39
•
Configuring 802.1x Violation Modes, page 8-40
•
Configuring the Host Mode, page 8-43 (optional)
•
Enabling MAC Move, page 8-44 (optional)
•
Enabling MAC Replace, page 8-45 (optional)
•
Configuring Periodic Re-Authentication, page 8-45 (optional)
•
Manually Re-Authenticating a Client Connected to a Port, page 8-46 (optional)
•
Changing the Quiet Period, page 8-47 (optional)
•
Changing the Switch-to-Client Retransmission Time, page 8-47 (optional)
•
Setting the Switch-to-Client Frame-Retransmission Number, page 8-48 (optional)
•
Setting the Re-Authentication Number, page 8-49 (optional)
•
Configuring 802.1x Accounting, page 8-49 (optional)
•
Configuring a Guest VLAN, page 8-50 (optional)
•
Configuring a Restricted VLAN, page 8-51 (optional)
•
Configuring the Inaccessible Authentication Bypass Feature, page 8-53 (optional)
•
Configuring 802.1x User Distribution, page 8-56 (optional)
•
Configuring 802.1x Authentication with WoL, page 8-57 (optional)
•
Configuring MAC Authentication Bypass, page 8-57 (optional)
•
Configuring NAC Layer 2 802.1x Validation, page 8-58 (optional)
•
Configuring an Authenticator and a Supplicant Switch with NEAT, page 8-60 (optional)
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Configuring 802.1x Authentication
•
Configuring 802.1x Authentication with Downloadable ACLs and Redirect URLs, page 8-61
(optional)
•
Configuring VLAN ID-based MAC Authentication, page 8-64 (optional)
•
Configuring Flexible Authentication Ordering, page 8-64 (optional)
•
Configuring Open1x, page 8-65 (optional)
•
Disabling 802.1x Authentication on the Port, page 8-65 (optional)
•
Resetting the 802.1x Authentication Configuration to the Default Values, page 8-66 (optional)
Default 802.1x Authentication Configuration
Table 8-4 shows the default 802.1x authentication configuration.
Table 8-4
Default 802.1x Authentication Configuration
Feature
Default Setting
Switch 802.1x enable state
Disabled.
Per-port 802.1x enable state
Disabled (force-authorized).
The port sends and receives normal traffic without
802.1x-based authentication of the client.
AAA
Disabled.
RADIUS server
•
IP address
•
None specified.
•
UDP authentication port
•
1812.
•
Key
•
None specified.
Host mode
Single-host mode.
Control direction
Bidirectional control.
Periodic re-authentication
Disabled.
Number of seconds between
re-authentication attempts
3600 seconds.
Re-authentication number
2 times (number of times that the switch restarts the
authentication process before the port changes to the
unauthorized state).
Quiet period
60 seconds (number of seconds that the switch remains in
the quiet state following a failed authentication exchange
with the client).
Retransmission time
30 seconds (number of seconds that the switch should
wait for a response to an EAP request/identity frame
from the client before resending the request).
Maximum retransmission number
2 times (number of times that the switch will send an
EAP-request/identity frame before restarting the
authentication process).
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Configuring 802.1x Authentication
Table 8-4
Default 802.1x Authentication Configuration (continued)
Feature
Default Setting
Client timeout period
30 seconds (when relaying a request from the
authentication server to the client, the amount of time the
switch waits for a response before resending the request
to the client.)
Authentication server timeout period
30 seconds (when relaying a response from the client to
the authentication server, the amount of time the switch
waits for a reply before resending the response to the
server.)
You can change this timeout period by using the dot1x
timeout server-timeout interface configuration
command.
Inactivity timeout
Disabled.
Guest VLAN
None specified.
Inaccessible authentication bypass
Disabled.
Restricted VLAN
None specified.
Authenticator (switch) mode
None specified.
MAC authentication bypass
Disabled.
802.1x Authentication Configuration Guidelines
These section has configuration guidelines for these features:
•
802.1x Authentication, page 8-35
•
VLAN Assignment, Guest VLAN, Restricted VLAN, and Inaccessible Authentication Bypass,
page 8-36
•
MAC Authentication Bypass, page 8-37
•
Maximum Number of Allowed Devices Per Port, page 8-37
802.1x Authentication
These are the 802.1x authentication configuration guidelines:
•
When IEEE 802.1x authentication is enabled, ports are authenticated before any other Layer 2 or
Layer 3 features are enabled.
•
If the VLAN to which an 802.1x-enabled port is assigned changes, this change is transparent and
does not affect the switch. For example, this change occurs if a port is assigned to a RADIUS
server-assigned VLAN and is then assigned to a different VLAN after re-authentication.
If the VLAN to which an 802.1x port is assigned to shut down, disabled, or removed, the port
becomes unauthorized. For example, the port is unauthorized after the access VLAN to which a port
is assigned shuts down or is removed.
•
The 802.1x protocol is supported on Layer 2 static-access ports, voice VLAN ports, and Layer 3
routed ports, but it is not supported on these port types:
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Configuring 802.1x Authentication
– Trunk port—If you try to enable 802.1x authentication on a trunk port, an error message
appears, and 802.1x authentication is not enabled. If you try to change the mode of an
802.1x-enabled port to trunk, an error message appears, and the port mode is not changed.
– Dynamic ports—A port in dynamic mode can negotiate with its neighbor to become a trunk
port. If you try to enable 802.1x authentication on a dynamic port, an error message appears,
and 802.1x authentication is not enabled. If you try to change the mode of an 802.1x-enabled
port to dynamic, an error message appears, and the port mode is not changed.
– Dynamic-access ports—If you try to enable 802.1x authentication on a dynamic-access (VLAN
Query Protocol [VQP]) port, an error message appears, and 802.1x authentication is not
enabled. If you try to change an 802.1x-enabled port to dynamic VLAN assignment, an error
message appears, and the VLAN configuration is not changed.
– EtherChannel port—Do not configure a port that is an active or a not-yet-active member of an
EtherChannel as an 802.1x port. If you try to enable 802.1x authentication on an EtherChannel
port, an error message appears, and 802.1x authentication is not enabled.
– Switched Port Analyzer (SPAN) and Remote SPAN (RSPAN) destination ports—You can
enable 802.1x authentication on a port that is a SPAN or RSPAN destination port. However,
802.1x authentication is disabled until the port is removed as a SPAN or RSPAN destination
port. You can enable 802.1x authentication on a SPAN or RSPAN source port.
•
Before globally enabling 802.1x authentication on a switch by entering the dot1x
system-auth-control global configuration command, remove the EtherChannel configuration from
the interfaces on which 802.1x authentication and EtherChannel are configured.
•
Cisco IOS Release 12.2(55)SE and later supports filtering of system messages related to 802.1x
authentication. See the “Authentication Manager CLI Commands” section on page 8-10.
VLAN Assignment, Guest VLAN, Restricted VLAN, and Inaccessible Authentication Bypass
These are the configuration guidelines for VLAN assignment, guest VLAN, restricted VLAN, and
inaccessible authentication bypass:
•
When 802.1x authentication is enabled on a port, you cannot configure a port VLAN that is equal
to a voice VLAN.
•
The 802.1x authentication with VLAN assignment feature is not supported on trunk ports, dynamic
ports, or with dynamic-access port assignment through a VMPS.
•
You can configure 802.1x authentication on a private-VLAN port, but do not configure IEEE 802.1x
authentication with port security, a voice VLAN, a guest VLAN, a restricted VLAN, or a per-user
ACL on private-VLAN ports.
•
You can configure any VLAN except an RSPAN VLAN, private VLAN, or a voice VLAN as an
802.1x guest VLAN. The guest VLAN feature is not supported on internal VLANs (routed ports) or
trunk ports; it is supported only on access ports.
•
After you configure a guest VLAN for an 802.1x port to which a DHCP client is connected, you
might need to get a host IP address from a DHCP server. You can change the settings for restarting
the IEEE 802.1x authentication process on the switch before the DHCP process on the client times
out and tries to get a host IP address from the DHCP server. Decrease the settings for the 802.1x
authentication process (authentication timer inactivity and authentication timer
reauthentication interface configuration commands). The amount to decrease the settings depends
on the connected 802.1x client type.
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Configuring 802.1x Authentication
•
When configuring the inaccessible authentication bypass feature, follow these guidelines:
– The feature is supported on 802.1x port in single-host mode and multihosts mode.
– If the client is running Windows XP and the port to which the client is connected is in the
critical-authentication state, Windows XP might report that the interface is not authenticated.
– If the Windows XP client is configured for DHCP and has an IP address from the DHCP server,
receiving an EAP-Success message on a critical port might not re-initiate the DHCP
configuration process.
– You can configure the inaccessible authentication bypass feature and the restricted VLAN on
an 802.1x port. If the switch tries to re-authenticate a critical port in a restricted VLAN and all
the RADIUS servers are unavailable, the switch changes the port state to the critical
authentication state and remains in the restricted VLAN.
•
You can configure any VLAN except an RSPAN VLAN or a voice VLAN as an 802.1x restricted
VLAN. The restricted VLAN feature is not supported on internal VLANs (routed ports) or trunk
ports; it is supported only on access ports.
MAC Authentication Bypass
These are the MAC authentication bypass configuration guidelines:
•
Unless otherwise stated, the MAC authentication bypass guidelines are the same as the 802.1x
authentication guidelines. For more information, see the “802.1x Authentication” section on
page 8-35.
•
If you disable MAC authentication bypass from a port after the port has been authorized with its
MAC address, the port state is not affected.
•
If the port is in the unauthorized state and the client MAC address is not the authentication-server
database, the port remains in the unauthorized state. However, if the client MAC address is added to
the database, the switch can use MAC authentication bypass to re-authorize the port.
•
If the port is in the authorized state, the port remains in this state until re-authorization occurs.
•
You can configure a timeout period for hosts that are connected by MAC authentication bypass but
are inactive. The range is 1-65535 seconds.
Maximum Number of Allowed Devices Per Port
This is the maximum number of devices allowed on an 802.1x-enabled port:
•
In single-host mode, only one device is allowed on the access VLAN. If the port is also configured with
a voice VLAN, an unlimited number of Cisco IP phones can send and receive traffic through the voice
VLAN.
•
In multidomain authentication (MDA) mode, one device is allowed for the access VLAN, and one
IP phone is allowed for the voice VLAN.
•
In multihost mode, only one 802.1x supplicant is allowed on the port, but an unlimited number of
non-802.1x hosts are allowed on the access VLAN. An unlimited number of devices are allowed on
the voice VLAN.
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Configuring 802.1x Authentication
Configuring 802.1x Readiness Check
The 802.1x readiness check monitors 802.1x activity on all the switch ports and displays information
about the devices connected to the ports that support 802.1x. You can use this feature to determine if the
devices connected to the switch ports are 802.1x-capable.
The 802.1x readiness check is allowed on all ports that can be configured for 802.1x. The readiness
check is not available on a port that is configured as dot1x force-unauthorized.
Follow these guidelines to enable the readiness check on the switch:
•
The readiness check is typically used before 802.1x is enabled on the switch.
•
If you use the dot1x test eapol-capable privileged EXEC command without specifying an interface,
all the ports on the switch are tested.
•
When you configure the dot1x test eapol-capable command on an 802.1x-enabled port, and the link
comes up, the port queries the connected client about its 802.1x capability. When the client responds
with a notification packet, it is 802.1x-capable. A syslog message is generated if the client responds
within the timeout period. If the client does not respond to the query, the client is not
802.1x-capable. No syslog message is generated.
•
The readiness check can be sent on a port that handles multiple hosts (for example, a PC that is
connected to an IP phone). A syslog message is generated for each of the clients that respond to the
readiness check within the timer period.
Beginning in privileged EXEC mode, follow these steps to enable the 802.1x readiness check on the
switch:
Step 1
Command
Purpose
dot1x test eapol-capable [interface
interface-id]
Enable the 802.1x readiness check on the switch.
(Optional) For interface-id specify the port on which to check for
IEEE 802.1x readiness.
Note
If you omit the optional interface keyword, all interfaces on the
switch are tested.
Step 1
configure terminal
(Optional) Enter global configuration mode.
Step 2
dot1x test timeout timeout
(Optional) Configure the timeout used to wait for EAPOL response. The
range is from 1 to 65535 seconds. The default is 10 seconds.
Step 3
end
(Optional) Return to privileged EXEC mode.
Step 4
show running-config
(Optional) Verify your modified timeout values.
This example shows how to enable a readiness check on a switch to query a port. It also shows the
response received from the queried port verifying that the device connected to it is 802.1x-capable:
switch# dot1x test eapol-capable interface gigabitethernet1/0/13
DOT1X_PORT_EAPOL_CAPABLE:DOT1X: MAC 00-01-02-4b-f1-a3 on gigabitethernet1/0/13 is EAPOL
capable
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Configuring 802.1x Authentication
Configuring Voice Aware 802.1x Security
You use the voice aware 802.1x security feature on the switch to disable only the VLAN on which a
security violation occurs, whether it is a data or voice VLAN. You can use this feature in IP phone
deployments where a PC is connected to the IP phone. A security violation found on the data VLAN
results in the shutdown of only the data VLAN. The traffic on the voice VLAN flows through the switch
without interruption.
Follow these guidelines to configure voice aware 802.1x voice security on the switch:
•
Note
You enable voice aware 802.1x security by entering the errdisable detect cause security-violation
shutdown vlan global configuration command. You disable voice aware 802.1x security by entering
the no version of this command. This command applies to all 802.1x-configured ports in the switch.
If you do not include the shutdown vlan keywords, the entire port is shut down when it enters the
error-disabled state.
•
If you use the errdisable recovery cause security-violation global configuration command to
configure error-disabled recovery, the port is automatically re-enabled. If error-disabled recovery is
not configured for the port, you re-enable it by using the shutdown and no-shutdown interface
configuration commands.
•
You can re-enable individual VLANs by using the clear errdisable interface interface-id vlan
[vlan-list] privileged EXEC command. If you do not specify a range, all VLANs on the port are
enabled.
Beginning in privileged EXEC mode, follow these steps to enable voice aware 802.1x security:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
errdisable detect cause
security-violation shutdown vlan
Shut down any VLAN on which a security violation error occurs.
Step 3
errdisable recovery cause
security-violation
(Optional) Enable automatic per-VLAN error recovery.
Step 4
clear errdisable interface interface-id
vlan [vlan-list]
(Optional) Reenable individual VLANs that have been error disabled.
Step 5
shutdown
Note
If the shutdown vlan keywords are not included, the entire port
enters the error-disabled state and shuts down.
•
For interface-id specify the port on which to reenable individual
VLANs.
•
(Optional) For vlan-list specify a list of VLANs to be re-enabled. If
vlan-list is not specified, all VLANs are re-enabled.
no-shutdown
(Optional) Re-enable an error-disabled VLAN, and clear all error-disable
indications.
Step 6
end
Return to privileged EXEC mode.
Step 7
show errdisable detect
Verify your entries.
Step 8
copy running-config startup-config
(Optional) Save your entries in the configuration file.
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Configuring 802.1x Authentication
This example shows how to configure the switch to shut down any VLAN on which a security violation
error occurs:
Switch(config)# errdisable detect cause security-violation shutdown vlan
This example shows how to re-enable all VLANs that were error disabled on port Gi4/0/2.
Switch# clear errdisable interface GigabitEthernet4/0/2 vlan
You can verify your settings by entering the show errdisable detect privileged EXEC command.
Configuring 802.1x Violation Modes
You can configure an 802.1x port so that it shuts down, generates a syslog error, or discards packets from
a new device when:
•
a device connects to an 802.1x-enabled port
•
the maximum number of allowed about devices have been authenticated on the port
Beginning in privileged EXEC mode, follow these steps to configure the security violation actions on
the switch:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
aaa new-model
Enable AAA.
Step 3
aaa authentication dot1x {default}
method1
Create an 802.1x authentication method list.
To create a default list that is used when a named list is not specified in
the authentication command, use the default keyword followed by the
method that is to be used in default situations. The default method list is
automatically applied to all ports.
For method1, enter the group radius keywords to use the list of all
RADIUS servers for authentication.
Note
Though other keywords are visible in the command-line help
string, only the group radius keywords are supported.
Step 4
interface interface-id
Specify the port connected to the client that is to be enabled for
IEEE 802.1x authentication, and enter interface configuration mode.
Step 5
switchport mode access
Set the port to access mode.
Step 6
authentication violation shutdown |
restrict | protect | replace}
Configure the violation mode. The keywords have these meanings:
•
shutdown–Error disable the port.
•
restrict–Generate a syslog error.
•
protect–Drop packets from any new device that sends traffic to the
port.
•
replace–Removes the current session and authenticates with the new
host.
Step 7
end
Return to privileged EXEC mode.
Step 8
show authentication
Verify your entries.
Step 9
copy running-config startup-config
(Optional) Save your entries in the configuration file.
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Configuring 802.1x Authentication
Configuring 802.1x Authentication
To configure 802.1x port-based authentication, you must enable authentication, authorization, and
accounting (AAA) and specify the authentication method list. A method list describes the sequence and
authentication method to be queried to authenticate a user.
To allow per-user ACLs or VLAN assignment, you must enable AAA authorization to configure the
switch for all network-related service requests.
This is the 802.1x AAA process:
Step 1
A user connects to a port on the switch.
Step 2
Authentication is performed.
Step 3
VLAN assignment is enabled, as appropriate, based on the RADIUS server configuration.
Step 4
The switch sends a start message to an accounting server.
Step 5
Re-authentication is performed, as necessary.
Step 6
The switch sends an interim accounting update to the accounting server that is based on the result of
re-authentication.
Step 7
The user disconnects from the port.
Step 8
The switch sends a stop message to the accounting server.
Beginning in privileged EXEC mode, follow these steps to configure 802.1x port-based authentication:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
aaa new-model
Enable AAA.
Step 3
aaa authentication dot1x {default}
method1
Create an 802.1x authentication method list.
To create a default list that is used when a named list is not specified in
the authentication command, use the default keyword followed by the
method that is to be used in default situations. The default method list is
automatically applied to all ports.
For method1, enter the group radius keywords to use the list of all
RADIUS servers for authentication.
Note
Though other keywords are visible in the command-line help
string, only the group radius keywords are supported.
Step 4
dot1x system-auth-control
Enable 802.1x authentication globally on the switch.
Step 5
aaa authorization network {default}
group radius
(Optional) Configure the switch to use user-RADIUS authorization for all
network-related service requests, such as per-user ACLs or VLAN
assignment.
Note
For per-user ACLs, single-host mode must be configured. This
setting is the default.
Step 6
radius-server host ip-address
(Optional) Specify the IP address of the RADIUS server.
Step 7
radius-server key string
(Optional) Specify the authentication and encryption key used between
the switch and the RADIUS daemon running on the RADIUS server.
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Configuring 802.1x Authentication
Command
Purpose
Step 8
interface interface-id
Specify the port connected to the client that is to be enabled for
IEEE 802.1x authentication, and enter interface configuration mode.
Step 9
switchport mode access
(Optional) Set the port to access mode only if you configured the RADIUS
server in Step 6 and Step 7.
Step 10
authentication port-control auto
Enable 802.1x authentication on the port.
For feature interaction information, see the “802.1x Authentication
Configuration Guidelines” section on page 8-35.
Step 11
dot1x pae authenticator
Set the interface Port Access Entity to act only as an authenticator and
ignore messages meant for a supplicant.
Step 12
end
Return to privileged EXEC mode.
Step 13
show dot1x
Verify your entries.
Step 14
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Configuring the Switch-to-RADIUS-Server Communication
RADIUS security servers are identified by their hostname or IP address, hostname and specific UDP port
numbers, or IP address and specific UDP port numbers. The combination of the IP address and UDP port
number creates a unique identifier, which enables RADIUS requests to be sent to multiple UDP ports on
a server at the same IP address. If two different host entries on the same RADIUS server are configured
for the same service—for example, authentication—the second host entry configured acts as the fail-over
backup to the first one. The RADIUS host entries are tried in the order that they were configured.
Beginning in privileged EXEC mode, follow these steps to configure the RADIUS server parameters on
the switch. This procedure is required.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
radius-server host {hostname |
Configure the RADIUS server parameters.
ip-address} auth-port port-number key For hostname | ip-address, specify the hostname or IP address of the
string
remote RADIUS server.
For auth-port port-number, specify the UDP destination port for
authentication requests. The default is 1812. The range is 0 to 65536.
For key string, specify the authentication and encryption key used
between the switch and the RADIUS daemon running on the RADIUS
server. The key is a text string that must match the encryption key used on
the RADIUS server.
Note
Always configure the key as the last item in the radius-server
host command syntax because leading spaces are ignored, but
spaces within and at the end of the key are used. If you use spaces
in the key, do not enclose the key in quotation marks unless the
quotation marks are part of the key. This key must match the
encryption used on the RADIUS daemon.
If you want to use multiple RADIUS servers, re-enter this command.
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Configuring 802.1x Authentication
Command
Purpose
Step 3
end
Return to privileged EXEC mode.
Step 4
show running-config
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To delete the specified RADIUS server, use the no radius-server host {hostname | ip-address} global
configuration command.
This example shows how to specify the server with IP address 172.20.39.46 as the RADIUS server, to
use port 1612 as the authorization port, and to set the encryption key to rad123, matching the key on the
RADIUS server:
Switch(config)# radius-server host 172.l20.39.46 auth-port 6403 key rad123
You can globally configure the timeout, retransmission, and encryption key values for all RADIUS
servers by using the radius-server host global configuration command. If you want to configure these
options on a per-server basis, use the radius-server timeout, radius-server retransmit, and the
radius-server key global configuration commands. For more information, see the “Configuring Settings
for All RADIUS Servers” section on page 7-34.
You also need to configure some settings on the RADIUS server. These settings include the IP address
of the switch and the key string to be shared by both the server and the switch. For more information,
see the RADIUS server documentation.
Configuring the Host Mode
Beginning in privileged EXEC mode, follow these steps to allow multiple hosts (clients) on an
IEEE 802.1x-authorized port that has the dot1x port-control interface configuration command set to
auto. Use the multi-domain keyword to configure multidomain authentication (MDA) to enable
authentication of both a host and a voice device, such as an IP phone (Cisco or non-Cisco) on the same
switch port. This procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify the port to which multiple hosts are indirectly attached, and enter
interface configuration mode.
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Configuring 802.1x Authentication
Command
Step 3
Purpose
authentication host-mode [multi-auth | The keywords have these meanings:
multi-domain | multi-host |
• multi-auth–Allow one client on the voice VLAN and multiple
single-host]
authenticated clients on the data VLAN.
The multi-auth keyword is only available with the
authentication host-mode command.
Note
•
single-host–Allow a single host (client) on an
IEEE 802.1x-authorized port.
•
multi-host–Allow multiple hosts on an 802.1x-authorized port after
a single host has been authenticated.
•
single-host–Allow a single host (client) on an 802.1x-authorized
port.
•
multi-domain–Allow both a host and a voice device, such as an IP
phone (Cisco or non-Cisco), to be authenticated on an
IEEE 802.1x-authorized port.
Note
You must configure the voice VLAN for the IP phone when the
host mode is set to multi-domain. For more information, see
Chapter 14, “Configuring Voice VLAN.”
Make sure that the authentication port-control interface configuration
command set is set to auto for the specified interface.
Step 4
end
Return to privileged EXEC mode.
Step 5
show authentication interface
interface-id
Verify your entries.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To disable multiple hosts on the port, use the no authentication host-mode interface configuration
command.
This example shows how to enable 802.1x authentication and to allow multiple hosts:
Switch(config)# interface gigabitethernet0/1
Switch(config-if)# authentication port-control auto
Switch(config-if)# authentication host-mode multi-host
Enabling MAC Move
MAC move allows an authenticated host to move from one port on the switch to another.
Beginning in privileged EXEC mode, follow these steps to globally enable MAC move on the switch.
This procedure is optional.
Command
Purpose
configure terminal
Enter global configuration mode.
authentication mac-move permit
Enable
end
Return to privileged EXEC mode.
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Command
Purpose
show run
Verify your entries.
copy running-config startup-config
(Optional) Save your entries in the configuration file.
This example shows how to globally enable MAC move on a switch:
Switch(config)# authentication mac-move permit
Enabling MAC Replace
MAC replace allows a host to replace an authenticated host on a port.
Beginning in privileged EXEC mode, follow these steps to enable MAC replace on an interface. This
procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify the port to be configured, and enter interface configuration mode.
Step 3
authentication violation {protect |
replace | restrict | shutdown}
Use the replace keyword to enable MAC replace on the interface. The
port removes the current session and initiates authentication with the new
host.
The other keywords have these effects:
•
protect: the port drops packets with unexpected MAC addresses
without generating a system message.
•
restrict: violating packets are dropped by the CPU and a system
message is generated.
•
shutdown: the port is error disabled when it receives an unexpected
MAC address.
Step 4
end
Return to privileged EXEc mode.
Step 5
show running-config
Verify your entries.
Step 6
copy running-config startup-config
(Optional) Saves your entries in the configuration file.
This example shows how to enable MAC replace on an interface:
Switch(config)# interface gigabitethernet2/0/2
Switch(config-if)# authentication violation replace
Configuring Periodic Re-Authentication
You can enable periodic 802.1x client re-authentication and specify how often it occurs. If you do not
specify a time period before enabling re-authentication, the number of seconds between attempts
is 3600.
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Configuring 802.1x Authentication
Beginning in privileged EXEC mode, follow these steps to enable periodic re-authentication of the client
and to configure the number of seconds between re-authentication attempts. This procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify the port to be configured, and enter interface configuration mode.
Step 3
authentication periodic
Enable periodic re-authentication of the client, which is disabled by
default.
Note
Step 4
authentication timer {{[inactivity |
reauthenticate]} {restart value}}
The default value is 3600 seconds. To change the value of the
reauthentication timer or to have the switch use a
RADIUS-provided session timeout, enter the authentication
timer reauthenticate command.
Set the number of seconds between re-authentication attempts.
The authentication timer keywords have these meanings:
•
inactivity—Interval in seconds after which if there is no activity from
the client then it is unauthorized
•
reauthenticate—Time in seconds after which an automatic
re-authentication attempt is be initiated
•
restart value—Interval in seconds after which an attempt is made to
authenticate an unauthorized port
This command affects the behavior of the switch only if periodic
re-authentication is enabled.
Step 5
end
Return to privileged EXEC mode.
Step 6
show authentication interface
interface-id
Verify your entries.
Step 7
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To disable periodic re-authentication, use the no authentication periodic interface configuration
command. To return to the default number of seconds between re-authentication attempts, use the no
authentication timer interface configuration command.
This example shows how to enable periodic re-authentication and set the number of seconds between
re-authentication attempts to 4000:
Switch(config-if)# authentication periodic
Switch(config-if)# authentication timer reauthenticate 4000
Manually Re-Authenticating a Client Connected to a Port
You can manually re-authenticate the client connected to a specific port at any time by entering the dot1x
re-authenticate interface interface-id privileged EXEC command. This step is optional. If you want to
enable or disable periodic re-authentication, see the “Configuring Periodic Re-Authentication” section
on page 8-45.
This example shows how to manually re-authenticate the client connected to a port:
Switch# dot1x re-authenticate interface gigabitethernet0/1
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Configuring 802.1x Authentication
Changing the Quiet Period
When the switch cannot authenticate the client, the switch remains idle for a set period of time and then
tries again. The dot1x timeout quiet-period interface configuration command controls the idle period.
A failed authentication of the client might occur because the client provided an invalid password. You
can provide a faster response time to the user by entering a number smaller than the default.
Beginning in privileged EXEC mode, follow these steps to change the quiet period. This procedure is
optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify the port to be configured, and enter interface configuration mode.
Step 3
authentication timer inactivity seconds Set the number of seconds that the switch remains in the quiet state
following a failed authentication exchange with the client.
The range is 1 to 65535 seconds; the default is 60.
Step 4
end
Return to privileged EXEC mode.
Step 5
show authentication interface
interface-id
Verify your entries.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To return to the default quiet time, use the no authentication timer inactivity interface configuration
command.
This example shows how to set the quiet time on the switch to 30 seconds:
Switch(config-if)# authentication timer inactivity 30
Changing the Switch-to-Client Retransmission Time
The client responds to the EAP-request/identity frame from the switch with an EAP-response/identity
frame. If the switch does not receive this response, it waits a set period of time (known as the
retransmission time) and then resends the frame.
Note
You should change the default value of this command only to adjust for unusual circumstances such as
unreliable links or specific behavioral problems with certain clients and authentication servers.
Beginning in privileged EXEC mode, follow these steps to change the amount of time that the switch
waits for client notification. This procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify the port to be configured, and enter interface configuration mode.
Step 3
authentication timer reauthenticate
seconds
Set the number of seconds that the switch waits for a response to an
EAP-request/identity frame from the client before resending the request.
The range is 1 to 65535 seconds; the default is 5.
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Command
Purpose
Step 4
end
Return to privileged EXEC mode.
Step 5
show authentication interface
interface-id
Verify your entries.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To return to the default retransmission time, use the no authentication timer reauthenticate interface
configuration command.
This example shows how to set 60 as the number of seconds that the switch waits for a response to an
EAP-request/identity frame from the client before resending the request:
Switch(config-if)# authentication timer reauthenticate 60
Setting the Switch-to-Client Frame-Retransmission Number
In addition to changing the switch-to-client retransmission time, you can change the number of times
that the switch sends an EAP-request/identity frame (assuming no response is received) to the client
before restarting the authentication process.
Note
You should change the default value of this command only to adjust for unusual circumstances such as
unreliable links or specific behavioral problems with certain clients and authentication servers.
Beginning in privileged EXEC mode, follow these steps to set the switch-to-client frame-retransmission
number. This procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify the port to be configured, and enter interface configuration mode.
Step 3
dot1x max-reauth-req count
Set the number of times that the switch sends an EAP-request/identity
frame to the client before restarting the authentication process. The range
is 1 to 10; the default is 2.
Step 4
end
Return to privileged EXEC mode.
Step 5
show authentication interface
interface-id
Verify your entries.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To return to the default retransmission number, use the no dot1x max-req interface configuration
command.
This example shows how to set 5 as the number of times that the switch sends an EAP-request/identity
request before restarting the authentication process:
Switch(config-if)# dot1x max-reauth-req 5
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Setting the Re-Authentication Number
You can also change the number of times that the switch restarts the authentication process before the
port changes to the unauthorized state.
Note
You should change the default value of this command only to adjust for unusual circumstances such as
unreliable links or specific behavioral problems with certain clients and authentication servers.
Beginning in privileged EXEC mode, follow these steps to set the re-authentication number. This
procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify the port to be configured, and enter interface configuration mode.
Step 3
dot1x max-req count
Set the number of times that the switch restarts the authentication process
before the port changes to the unauthorized state. The range is 0 to 10; the
default is 2.
Step 4
end
Return to privileged EXEC mode.
Step 5
show authentication interface
interface-id
Verify your entries.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To return to the default re-authentication number, use the no dot1x max-reauth-req interface
configuration command.
This example shows how to set 4 as the number of times that the switch restarts the authentication
process before the port changes to the unauthorized state:
Switch(config-if)# dot1x max-reauth-req 4
Configuring 802.1x Accounting
Enabling AAA system accounting with 802.1x accounting allows system reload events to be sent to the
accounting RADIUS server for logging. The server can then infer that all active 802.1x sessions are
closed.
Because RADIUS uses the unreliable UDP transport protocol, accounting messages might be lost due to
poor network conditions. If the switch does not receive the accounting response message from the
RADIUS server after a configurable number of retransmissions of an accounting request, this system
message appears:
Accounting message %s for session %s failed to receive Accounting Response.
When the stop message is not sent successfully, this message appears:
00:09:55: %RADIUS-4-RADIUS_DEAD: RADIUS server 172.20.246.201:1645,1646 is not responding.
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Note
You must configure the RADIUS server to perform accounting tasks, such as logging start, stop, and
interim-update messages and time stamps. To turn on these functions, enable logging of
“Update/Watchdog packets from this AAA client” in your RADIUS server Network Configuration tab.
Next, enable “CVS RADIUS Accounting” in your RADIUS server System Configuration tab.
Beginning in privileged EXEC mode, follow these steps to configure 802.1x accounting after AAA is
enabled on your switch. This procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify the port to be configured, and enter interface configuration mode.
Step 3
aaa accounting dot1x default
start-stop group radius
Enable 802.1x accounting using the list of all RADIUS servers.
Step 4
aaa accounting system default
start-stop group radius
(Optional) Enables system accounting (using the list of all RADIUS
servers) and generates system accounting reload event messages when the
switch reloads.
Step 5
end
Return to privileged EXEc mode.
Step 6
show running-config
Verify your entries.
Step 7
copy running-config startup-config
(Optional) Saves your entries in the configuration file.
Use the show radius statistics privileged EXEC command to display the number of RADIUS messages
that do not receive the accounting response message.
This example shows how to configure 802.1x accounting. The first command configures the RADIUS
server, specifying 1813 as the UDP port for accounting:
Switch(config)# radius-server host 172.120.39.46 auth-port 1812 acct-port 1813 key rad123
Switch(config)# aaa accounting dot1x default start-stop group radius
Switch(config)# aaa accounting system default start-stop group radius
Configuring a Guest VLAN
When you configure a guest VLAN, clients that are not 802.1x-capable are put into the guest VLAN
when the server does not receive a response to its EAP request/identity frame. Clients that are
802.1x-capable but that fail authentication are not granted network access. The switch supports guest
VLANs in single-host or multiple-hosts mode.
Beginning in privileged EXEC mode, follow these steps to configure a guest VLAN. This procedure is
optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify the port to be configured, and enter interface configuration mode.
For the supported port types, see the “802.1x Authentication
Configuration Guidelines” section on page 8-35.
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Configuring 802.1x Authentication
Command
Purpose
switchport mode access
Set the port to access mode,
or
or
switchport mode private-vlan host
Configure the Layer 2 port as a private-VLAN host port.
Step 4
dot1x port-control auto
Enable 802.1x authentication on the port.
Step 5
authentication event no-response
action authorize vlan vlan-id
Specify an active VLAN as an 802.1x guest VLAN. The range is 1 to
4094.
Step 3
You can configure any active VLAN except an internal VLAN (routed
port), an RSPAN VLAN, a primary private VLAN, or a voice VLAN as
an 802.1x guest VLAN.
Step 6
end
Return to privileged EXEC mode.
Step 7
show authentication interface-id
Verify your entries.
Step 8
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To disable and remove the guest VLAN, use the no authentication event no-response action authorize
vlan vlan-id interface configuration command. The port returns to the unauthorized state.
This example shows how to enable VLAN 2 as an 802.1x guest VLAN:
Switch(config)# interface gigabitethernet0/2
Switch(config-if)# authentication event no-response action authorize vlan 2
This example shows how to set 3 as the quiet time on the switch, to set 15 as the number of seconds that
the switch waits for a response to an EAP-request/identity frame from the client before re-sending the
request, and to enable VLAN 2 as an 802.1x guest VLAN when an 802.1x port is connected to a DHCP
client:
Switch(config-if)# authentication timer inactivity 3
Switch(config-if)# authentication timer reauthenticate 15
Switch(config-if)# authentication event no-response action authorize vlan 2
Configuring a Restricted VLAN
When you configure a restricted VLAN on a switch, clients that are IEEE 802.1x-compliant are moved
into the restricted VLAN when the authentication server does not receive a valid username and
password. The switch supports restricted VLANs only in single-host mode.
Beginning in privileged EXEC mode, follow these steps to configure a restricted VLAN. This procedure
is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify the port to be configured, and enter interface configuration mode.
For the supported port types, see the “802.1x Authentication
Configuration Guidelines” section on page 8-35.
Step 3
switchport mode access
Set the port to access mode,
or
or
switchport mode private-vlan host
Configure the Layer 2 port as a private-VLAN host port.
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Command
Purpose
Step 4
authentication port-control auto
Enable 802.1x authentication on the port.
Step 5
dot1x auth-fail vlan vlan-id
Specify an active VLAN as an 802.1x restricted VLAN. The range is 1 to
4094.
You can configure any active VLAN except an internal VLAN (routed
port), an RSPAN VLAN, a primary private VLAN, or a voice VLAN as
an 802.1x restricted VLAN.
Step 6
end
Return to privileged EXEC mode.
Step 7
show authentication interface
interface-id
(Optional) Verify your entries.
Step 8
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To disable and remove the restricted VLAN, use the no authentication event fail action authorize
vlan-id interface configuration command. The port returns to the unauthorized state.
This example shows how to enable VLAN 2 as an 802.1x restricted VLAN:
Switch(config)# interface gigabitethernet0/2
Switch(config-if)# authentication event fail action authorize 2
You can configure the maximum number of authentication attempts allowed before a user is assigned to
the restricted VLAN by using the authentication event retry retry count interface configuration
command. The range of allowable authentication attempts is 1 to 3. The default is 3 attempts.
Beginning in privileged EXEC mode, follow these steps to configure the maximum number of allowed
authentication attempts. This procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify the port to be configured, and enter interface configuration mode.
For the supported port types, see the “802.1x Authentication
Configuration Guidelines” section on page 8-35.
Step 3
switchport mode access
Set the port to access mode,
or
or
switchport mode private-vlan host
Configure the Layer 2 port as a private-VLAN host port.
Step 4
authentication port-control auto
Enable 802.1x authentication on the port.
Step 5
authentication event fail action
authorize vlan-id
Specify an active VLAN as an 802.1x restricted VLAN. The range is 1 to
4094.
You can configure any active VLAN except an internal VLAN (routed
port), an RSPAN VLAN, a primary private VLAN, or a voice VLAN as
an 802.1x restricted VLAN.
Step 6
authentication event retry retry count
Specify a number of authentication attempts to allow before a port moves
to the restricted VLAN. The range is 1 to 3, and the default is 3.
Step 7
end
Return to privileged EXEC mode.
Step 8
show authentication interface
interface-id
(Optional) Verify your entries.
Step 9
copy running-config startup-config
(Optional) Save your entries in the configuration file.
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To return to the default value, use the no authentication event retry interface configuration command.
This example shows how to set 2 as the number of authentication attempts allowed before the port moves
to the restricted VLAN:
Switch(config-if)# authentication event retry 2
Configuring the Inaccessible Authentication Bypass Feature
You can configure the inaccessible bypass feature, also referred to as critical authentication or the AAA
fail policy.
Beginning in privileged EXEC mode, follow these steps to configure the port as a critical port and enable
the inaccessible authentication bypass feature. This procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
radius-server dead-criteria time time
tries tries
(Optional) Set the conditions that are used to decide when a RADIUS
server is considered unavailable or dead.
The range for time is from 1 to 120 seconds. The switch dynamically
determines the default seconds value that is 10 to 60 seconds.
The range for tries is from 1 to 100. The switch dynamically determines
the default tries parameter that is 10 to 100.
Step 3
radius-server deadtime minutes
(Optional) Set the number of minutes that a RADIUS server is not sent
requests. The range is from 0 to 1440 minutes (24 hours). The default is
0 minutes.
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Step 4
Command
Purpose
radius-server host ip-address
[acct-port udp-port] [auth-port
udp-port] [test username name
[idle-time time] [ignore-acct-port]
[ignore-auth-port]] [key string]
(Optional) Configure the RADIUS server parameters by using these
keywords:
•
acct-port udp-port—Specify the UDP port for the RADIUS
accounting server. The range for the UDP port number is from 0 to
65536. The default is 1646.
•
auth-port udp-port—Specify the UDP port for the RADIUS
authentication server. The range for the UDP port number is from 0
to 65536. The default is 1645.
Note
Step 5
dot1x critical {eapol | recovery delay
milliseconds}
You should configure the UDP port for the RADIUS accounting
server and the UDP port for the RADIUS authentication server to
nondefault values.
•
test username name—Enable automated testing of the RADIUS
server status, and specify the username to be used.
•
idle-time time—Set the interval of time in minutes after which the
switch sends test packets to the server. The range is from 1 to
35791 minutes. The default is 60 minutes (1 hour).
•
ignore-acct-port—Disable testing on the RADIUS-server
accounting port.
•
ignore-auth-port—Disable testing on the RADIUS-server
authentication port.
•
For key string, specify the authentication and encryption key used
between the switch and the RADIUS daemon running on the
RADIUS server. The key is a text string that must match the
encryption key used on the RADIUS server.
Note
Always configure the key as the last item in the radius-server
host command syntax because leading spaces are ignored, but
spaces within and at the end of the key are used. If you use spaces
in the key, do not enclose the key in quotation marks unless the
quotation marks are part of the key. This key must match the
encryption used on the RADIUS daemon.You can also configure
the authentication and encryption key by using the radius-server
key {0 string | 7 string | string} global configuration command.
Note
You can also configure the authentication and encryption key by
using the radius-server key {0 string | 7 string | string} global
configuration command.
(Optional) Configure the parameters for inaccessible authentication
bypass:
eapol—Specify that the switch sends an EAPOL-Success message when
the switch successfully authenticates the critical port.
recovery delay milliseconds—Set the recovery delay period during
which the switch waits to re-initialize a critical port when a RADIUS
server that was unavailable becomes available. The range is from 1 to
10000 milliseconds. The default is 1000 milliseconds (a port can be
re-initialized every second).
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Command
Purpose
Step 6
interface interface-id
Specify the port to be configured, and enter interface configuration mode.
For the supported port types, see the “802.1x Authentication
Configuration Guidelines” section on page 8-35.
Step 7
authentication event server dead
action [authorize | reinitialize] vlan
vlan-id
Use these keywords to move hosts on the port if the RADIUS server is
unreachable:
Step 8
authentication event server dead
action {authorize | reinitialize} vlan
vlan-id]
•
authorize–Move any new hosts trying to authenticate to the
user-specified critical VLAN.
•
reinitialize–Move all authorized hosts on the port to the
user-specified critical VLAN.
Enable the inaccessible authentication bypass feature, and use these
keywords to configure the feature:
•
authorize—Authorize the port.
•
reinitialize—Reinitialize all authorized clients.
Step 9
authentication server dead action
authorize [vlan]
Authorize the switch in access VLAN or configured VLAN (if the VLAN
is specified) when the ACS server is down.
Step 10
end
Return to privileged EXEC mode.
Step 11
show authentication interface
interface-id
(Optional) Verify your entries.
Step 12
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To return to the RADIUS server default settings, use the no radius-server dead-criteria, the no
radius-server deadtime, and the no radius-server host global configuration commands. To return to
the default settings of inaccessible authentication bypass, use the no authentication event server dead
action {authorize | reinitialize} global configuration command. To disable inaccessible authentication
bypass, use the no authentication event server dead action interface configuration command.
This example shows how to configure the inaccessible authentication bypass feature:
Switch(config)# radius-server dead-criteria time 30 tries 20
Switch(config)# radius-server deadtime 60
Switch(config)# radius-server host 1.1.1.2 acct-port 1550 auth-port 1560 test username
user1 idle-time 30 key abc1234
Switch(config)# dot1x critical eapol
Switch(config)# dot1x critical recovery delay 2000
Switch(config)# interface gigabitethernet0/1
Switch(config)# radius-server deadtime 60
Switch(config-if)# dot1x critical
Switch(config-if)# dot1x critical recovery action reinitialize
Switch(config-if)# dot1x critical vlan 20
Switch(config-if)# end
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Configuring 802.1x Authentication
Configuring 802.1x User Distribution
Beginning in global configuration, follow these steps to configure a VLAN group and to map a VLAN
to it:
Command
Purpose
Step 1
vlan group vlan-group-name vlan-list vlan-list
Configure a VLAN group, and map a single VLAN or a
range of VLANs to it.
Step 2
show vlan group all vlan-group-name
Verify the configuration.
Step 3
no vlan group vlan-group-name vlan-list vlan-list
Clear the VLAN group configuration or elements of the
VLAN group configuration.
This example shows how to configure the VLAN groups, to map the VLANs to the groups, to and verify
the VLAN group configurations and mapping to the specified VLANs:
switch(config)# vlan group eng-dept vlan-list 10
switch(config)# show vlan group group-name eng-dept
Group Name
Vlans Mapped
-------------------------eng-dept
10
switch# show dot1x vlan-group all
Group Name
Vlans Mapped
-------------------------eng-dept
10
hr-dept
20
This example shows how to add a VLAN to an existing VLAN group and to verify that the VLAN was
added:
switch(config)# vlan group eng-dept vlan-list 30
switch(config)# show vlan group eng-dept
Group Name
Vlans Mapped
-------------------------eng-dept
10,30
This example shows how to remove a VLAN from a VLAN group:
switch# no vlan group eng-dept vlan-list 10
This example shows that when all the VLANs are cleared from a VLAN group, the VLAN group is
cleared:
switch(config)# no vlan group eng-dept vlan-list 30
Vlan 30 is successfully cleared from vlan group eng-dept.
switch(config)# show vlan group group-name eng-dept
This example shows how to clear all the VLAN groups:
switch(config)# no vlan group end-dept vlan-list all
switch(config)# show vlan-group all
For more information about these commands, see the Cisco IOS Security Command Reference.
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Configuring IEEE 802.1x Port-Based Authentication
Configuring 802.1x Authentication
Configuring 802.1x Authentication with WoL
Beginning in privileged EXEC mode, follow these steps to enable 802.1x authentication with WoL. This
procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify the port to be configured, and enter interface configuration mode.
For the supported port types, see the “802.1x Authentication
Configuration Guidelines” section on page 8-35.
Step 3
authentication control-direction {both Enable 802.1x authentication with WoL on the port, and use these
| in}
keywords to configure the port as bidirectional or unidirectional.
•
both—Sets the port as bidirectional. The port cannot receive packets
from or send packets to the host. By default, the port is bidirectional.
•
in—Sets the port as unidirectional. The port can send packets to the
host but cannot receive packets from the host.
Step 4
end
Return to privileged EXEC mode.
Step 5
show authentication interface-id
Verify your entries.
or
show dot1x interface interface-id
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To disable 802.1x authentication with WoL, use the no dot1x control-direction interface configuration
command.
This example shows how to enable 802.1x authentication with WoL and set the port as bidirectional:
Switch(config-if)# authentication control-direction both
Configuring MAC Authentication Bypass
Beginning in privileged EXEC mode, follow these steps to enable MAC authentication bypass. This
procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify the port to be configured, and enter interface configuration mode.
For the supported port types, see the “802.1x Authentication
Configuration Guidelines” section on page 8-35.
Step 3
authentication port-control auto
Enable 802.1x authentication on the port.
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Configuring 802.1x Authentication
Command
Step 4
Purpose
authentication order [mab] {webauth} Set the order of authentication methods.
•
mab—Add MAC authentication bypass (MAB) to the order of
authentication methods.
•
webauth—Add web authentication to the order of authentication
methods.
Step 5
end
Return to privileged EXEC mode.
Step 6
show authentication interface
interface-id
Verify your entries.
Step 7
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To disable MAC authentication bypass, use the no authentication order interface configuration
command.
This example shows how to enable MAC authentication bypass:
Switch(config-if)# authentication order
Configuring NAC Layer 2 802.1x Validation
You can configure NAC Layer 2 802.1x validation, which is also referred to as 802.1x authentication
with a RADIUS server.
Beginning in privileged EXEC mode, follow these steps to configure NAC Layer 2 802.1x validation.
The procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify the port to be configured, and enter interface configuration mode.
Step 3
authentication event no-response
action authorize vlan vlan-id
Specify an active VLAN as an 802.1x guest VLAN. The range is 1
to 4094.
You can configure any active VLAN except an internal VLAN (routed
port), an RSPAN VLAN, or a voice VLAN as an 802.1x guest VLAN.
Step 4
authentication periodic
Enable periodic re-authentication of the client, which is disabled by
default.
Step 5
authentication timer reauthenticate
Set re-authentication attempt for the client (set to one hour).
This command affects the behavior of the switch only if periodic
re-authentication is enabled.
Step 6
end
Return to privileged EXEC mode.
Step 7
show authentication interface
interface-id
Verify your 802.1x authentication configuration.
Step 8
copy running-config startup-config
(Optional) Save your entries in the configuration file.
This example shows how to configure NAC Layer 2 802.1x validation:
Switch# configure terminal
Switch(config)# interface gigabitethernet0/1
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Configuring IEEE 802.1x Port-Based Authentication
Configuring 802.1x Authentication
Switch(config-if)# authentication periodic
Switch(config-if)# authentication timer reauthenticate
Configuring IEEE 802.1x Authentication Using a RADIUS Server
You can configure NAC Layer 2 802.1x validation, which is also referred to as 802.1x authentication
with a RADIUS server.
Beginning in privileged EXEC mode, follow these steps to configure NAC Layer 2 802.1x validation.
The procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify the port to be configured, and enter interface configuration mode.
Step 3
dot1x guest-vlan vlan-id
Specify an active VLAN as an 802.1x guest VLAN. The range is 1 to
4094.
You can configure any active VLAN except an internal VLAN (routed
port), an RSPAN VLAN, or a voice VLAN as an 802.1x guest VLAN.
Step 4
authentication periodic
Enable periodic re-authentication of the client, which is disabled by
default.
Step 5
authentication timer {{[inactivity |
reauthenticate]} {restart value}}
Set the number of seconds between re-authentication attempts.
The authentication timer keywords have these meanings:
•
inactivity—Interval in seconds after which if there is no activity from
the client then it is unauthorized
•
reauthenticate—Time in seconds after which an automatic
re-authentication attempt is be initiated
•
restart value—Interval in seconds after which an attempt is made to
authenticate an unauthorized port
This command affects the behavior of the switch only if periodic
re-authentication is enabled.
Step 6
end
Return to privileged EXEC mode.
Step 7
show authentication interface
interface-id
Verify your 802.1x authentication configuration.
Step 8
copy running-config startup-config
(Optional) Save your entries in the configuration file.
This example shows how to configure NAC Layer 2 802.1x validation:
Switch# configure terminal
Switch(config)# interface gigabitethernet0/1
Switch(config-if)# authentication periodic
Switch(config-if)# authentication timer reauthenticate 4000
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Configuring IEEE 802.1x Port-Based Authentication
Configuring 802.1x Authentication
Configuring an Authenticator and a Supplicant Switch with NEAT
Configuring this feature requires that one switch outside a wiring closet is configured as a supplicant and
is connected to an authenticator switch.
For overview information, see the “802.1x Supplicant and Authenticator Switches with Network Edge
Access Topology (NEAT)” section on page 8-31.
Note
The cisco-av-pairs must be configured as device-traffic-class=switch on the ACS, which sets the
interface as a trunk after the supplicant is successfully authenticated.
Beginning in privileged EXEC mode, follow these steps to configure a switch as an authenticator:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
cisp enable
Enable CISP.
Step 3
interface interface-id
Specify the port to be configured, and enter interface configuration
mode.
Step 4
switchport mode access
Set the port mode to access.
Step 5
authentication port-control auto
Set the port-authentication mode to auto.
Step 6
dot1x pae authenticator
Configure the interface as a port access entity (PAE) authenticator.
Step 7
spanning-tree portfast
Enable Port Fast on an access port connected to a single workstation or
server.
Step 8
end
Return to privileged EXEC mode.
Step 9
show running-config interface
interface-id
Verify your configuration.
Step 10
copy running-config startup-config
(Optional) Save your entries in the configuration file.
This example shows how to configure a switch as an 802.1x authenticator:
Switch# configure terminal
Switch(config)# cisp enable
Switch(config)# interface gigabitethernet2/0/1
Switch(config-if)# switchport mode access
Switch(config-if)# authentication port-control auto
Switch(config-if)# dot1x pae authenticator
Switch(config-if)# spanning-tree portfast trunk
Beginning in privileged EXEC mode, follow these steps to configure a switch as a supplicant:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
cisp enable
Enable CISP.
Step 3
dot1x credentials profile
Create 802.1x credentials profile. This must be attached to the port that
is configured as supplicant.
Step 4
username suppswitch
Create a username.
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Configuring 802.1x Authentication
Command
Purpose
Step 5
password password
Create a password for the new username.
Step 6
dot1x supplicant force-multicast
Force the switch to send only multicast EAPOL packets when it receives
either unicast or multicast packets.
This also allows NEAT to work on the supplicant switch in all host
modes.
Step 7
interface interface-id
Specify the port to be configured, and enter interface configuration
mode.
Step 8
switchport trunk encapsulation
dot1q
Set the port to trunk mode.
Step 9
switchport mode trunk
Configure the interface as a VLAN trunk port.
Step 10
dot1x pae supplicant
Configure the interface as a port access entity (PAE) supplicant.
Step 11
dot1x credentials profile-name
Attach the 802.1x credentials profile to the interface.
Step 12
end
Return to privileged EXEC mode.
Step 13
show running-config interface
interface-id
Verify your configuration.
Step 14
copy running-config startup-config
(Optional) Save your entries in the configuration file.
This example shows how to configure a switch as a supplicant:
Switch# configure terminal
Switch(config)# cisp enable
Switch(config)# dot1x credentials test
Switch(config)# username suppswitch
Switch(config)# password myswitch
Switch(config)# dot1x supplicant force-multicast
Switch(config)# interface gigabitethernet1/0/1
Switch(config-if)# switchport trunk encapsulation dot1q
Switch(config-if)# switchport mode trunk
Switch(config-if)# dot1x pae supplicant
Switch(config-if)# dot1x credentials test
Switch(config-if)# end
Configuring NEAT with ASP
You can also use an AutoSmart Ports user-defined macro instead of the switch VSA to configure the
authenticator switch. For more information, see the Chapter 11, “Configuring Smartports Macros.”
Configuring 802.1x Authentication with Downloadable ACLs and Redirect URLs
In addition to configuring 802.1x authentication on the switch, you need to configure the ACS. For more
information, see the Cisco Secure ACS configuration guides.
Note
You must configure a downloadable ACL on the ACS before downloading it to the switch.
After authentication on the port, you can use the show ip access-list privileged EXEC command to
display the downloaded ACLs on the port.
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Configuring IEEE 802.1x Port-Based Authentication
Configuring a Downloadable Policy
Configuring Downloadable ACLs
The policies take effect after client authentication and the client IP address addition to the IP device
tracking table. The switch then applies the downloadable ACL to the port.
Beginning in privileged EXEC mode:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
ip device tracking
Configure the ip device tracking table.
Step 3
aaa new-model
Enables AAA.
Step 4
aaa authorization network default group
radius
Sets the authorization method to local. To remove the
authorization method, use the no aaa authorization network
default group radius command.
Step 5
radius-server vsa send authentication
Configure the radius vsa send authentication.
Step 6
interface interface-id
Specify the port to be configured, and enter interface
configuration mode.
Step 7
ip access-group acl-id in
Configure the default ACL on the port in the input direction.
Note
The acl-id is an access list name or number.
Step 8
show running-config interface interface-id
Verify your configuration.
Step 9
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Configuring a Downloadable Policy
Beginning in privileged EXEC mode:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
access-list access-list-number
deny source source-wildcard log
Defines the default port ACL by using a source address and wildcard.
The access-list-number is a decimal number from 1 to 99 or 1300 to 1999.
Enter deny or permit to specify whether to deny or permit access if conditions
are matched.
The source is the source address of the network or host that sends a packet, such
as this:
•
The 32-bit quantity in dotted-decimal format.
•
The keyword any as an abbreviation for source and source-wildcard value of
0.0.0.0 255.255.255.255. You do not need to enter a source-wildcard value.
•
The keyword host as an abbreviation for source and source-wildcard of
source 0.0.0.0.
(Optional) Applies the source-wildcard wildcard bits to the source.
(Optional) Enters log to cause an informational logging message about the packet
that matches the entry to be sent to the console.
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Configuring IEEE 802.1x Port-Based Authentication
Configuring a Downloadable Policy
Command
Purpose
Step 3
interface interface-id
Enter interface configuration mode.
Step 4
ip access-group acl-id in
Configure the default ACL on the port in the input direction.
Note
The acl-id is an access list name or number.
Step 5
exit
Returns to global configuration mode.
Step 6
aaa new-model
Enables AAA.
Step 7
aaa authorization network
default group radius
Sets the authorization method to local. To remove the authorization method, use
the no aaa authorization network default group radius command.
Step 8
ip device tracking
Enables the IP device tracking table.
To disable the IP device tracking table, use the no ip device tracking global
configuration commands.
Step 9
ip device tracking probe [count | (Optional) Configures the IP device tracking table:
interval | use-svi]
• count count—Sets the number of times that the switch sends the ARP probe.
The range is from 1 to 5. The default is 3.
Step 10 radius-server vsa send
authentication
•
interval interval—Sets the number of seconds that the switch waits for a
response before resending the ARP probe. The range is from 30 to 300
seconds. The default is 30 seconds.
•
use-svi—Uses the switch virtual interface (SVI) IP address as source of ARP
probes.
Configures the network access server to recognize and use vendor-specific
attributes.
Note
The downloadable ACL must be operational.
Step 11 end
Returns to privileged EXEC mode.
Step 12 show ip device tracking all
Displays information about the entries in the IP device tracking table.
Step 13 copy running-config
(Optional) Saves your entries in the configuration file.
startup-config
This example shows how to configure a switch for a downloadable policy:
Switch# config terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# aaa new-model
Switch(config)# aaa authorization network default group radius
Switch(config)# ip device tracking
Switch(config)# ip access-list extended default_acl
Switch(config-ext-nacl)# permit ip any any
Switch(config-ext-nacl)# exit
Switch(config)# radius-server vsa send authentication
Switch(config)# int fastEthernet 2/13
Switch(config-if)# ip access-group default_acl in
Switch(config-if)# exit
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Configuring IEEE 802.1x Port-Based Authentication
Configuring a Downloadable Policy
Configuring VLAN ID-based MAC Authentication
Beginning in privileged EXEC mode, follow these steps:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
mab request format attribute 32 vlan access-vlan
Enable VLAN ID-based MAC authentication.
Step 3
copy running-config startup-config
(Optional) Save your entries in the configuration
file.
There is no show command to confirm the status of VLAN ID-based MAC authentication. You can use
the debug radius accounting privileged EXEC command to confirm the RADIUS attribute 32. For more
information about this command, see the Cisco IOS Debug Command Reference, Release 12.2 at this
URL:
http://www.cisco.com/en/US/docs/ios/debug/command/reference/db_q1.html#wp1123741
This example shows how to globally enable VLAN ID-based MAC authentication on a switch:
Switch# config terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# mab request format attribute 32 vlan access-vlan
Switch(config-if)# exit
Configuring Flexible Authentication Ordering
Beginning in privileged EXEC mode, follow these steps:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify the port to be configured, and enter interface
configuration mode.
Step 3
authentication order dot1x | mab {webauth}
(Optional) Set the order of authentication methods used on a port.
Step 4
authentication priority dot1x | mab
{webauth}
(Optional) Add an authentication method to the port-priority list.
Step 5
show authentication
(Optional) Verify your entries.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
This example shows how to configure a port attempt 802.1x authentication first, followed by web
authentication as fallback method:
Switch# configure terminal
Switch(config)# interface gigabitethernet 1/0/1
Switch(config)# authentication order dot1x webauth
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Configuring IEEE 802.1x Port-Based Authentication
Configuring a Downloadable Policy
Configuring Open1x
Beginning in privileged EXEC mode:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify the port to be configured, and enter interface
configuration mode.
Step 3
authentication control-direction {both | in}
(Optional) Configure the port control as unidirectional or
bidirectional.
Step 4
authentication fallback name
(Optional) Configure a port to use web authentication as a
fallback method for clients that do not support 802.1x
authentication.
Step 5
authentication host-mode [multi-auth |
multi-domain | multi-host | single-host]
(Optional) Set the authorization manager mode on a port.
Step 6
authentication open
(Optional) Enable or disable open access on a port.
Step 7
authentication order [dot1x | mab] |
{webauth}
(Optional) Set the order of authentication methods used on a port.
Step 8
authentication periodic
(Optional) Enable or disable reauthentication on a port.
Step 9
authentication port-control {auto |
force-authorized | force-un authorized}
(Optional) Enable manual control of the port authorization state.
Step 10
show authentication
(Optional) Verify your entries.
Step 11
copy running-config startup-config
(Optional) Save your entries in the configuration file.
This example shows how to configure open 1x on a port:
Switch# configure terminal
Switch(config)# interface gigabitethernet 1/0/1
Switch(config)# authentication control-direction both
Switch(config)# authentication fallback profile1
Switch(config)# authentication host-mode multi-auth
Switch(config)# authentication open
Switch(config)# authentication order dot1x webauth
Switch(config)# authentication periodic
Switch(config)# authentication port-control auto
Disabling 802.1x Authentication on the Port
You can disable 802.1x authentication on the port by using the no dot1x pae interface configuration
command.
Beginning in privileged EXEC mode, follow these steps to disable 802.1x authentication on the port.
This procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify the port to be configured, and enter interface configuration mode.
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Displaying 802.1x Statistics and Status
Command
Purpose
Step 3
no dot1x pae
Disable 802.1x authentication on the port.
Step 4
end
Return to privileged EXEC mode.
Step 5
show authentication interface
interface-id
Verify your entries.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To configure the port as an 802.1x port access entity (PAE) authenticator, which enables IEEE 802.1x
on the port but does not allow clients connected to the port to be authorized, use the dot1x pae
authenticator interface configuration command.
This example shows how to disable 802.1x authentication on the port:
Switch(config)# interface gigabitethernet0/1
Switch(config-if)# no dot1x pae authenticator
Resetting the 802.1x Authentication Configuration to the Default Values
Beginning in privileged EXEC mode, follow these steps to reset the 802.1x authentication configuration
to the default values. This procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Enter interface configuration mode, and specify the port to be configured.
Step 3
dot1x default
Reset the 802.1x parameters to the default values.
Step 4
end
Return to privileged EXEC mode.
Step 5
show authentication interface
interface-id
Verify your entries.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Displaying 802.1x Statistics and Status
To display 802.1x statistics for all ports, use the show dot1x all statistics privileged EXEC command.
To display 802.1x statistics for a specific port, use the show dot1x statistics interface interface-id
privileged EXEC command.
To display the 802.1x administrative and operational status for the switch, use the show dot1x all
[details | statistics | summary] privileged EXEC command. To display the 802.1x administrative and
operational status for a specific port, use the show dot1x interface interface-id privileged EXEC
command.
Beginning with Cisco IOS Release 12.2(55)SE, you can use the no dot1x logging verbose global
configuration command to filter verbose 802.1x authentication messages. See the “Authentication
Manager CLI Commands” section on page 8-10.
For detailed information about the fields in these displays, see the command reference for this release.
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9
Configuring Web-Based Authentication
This chapter describes how to configure web-based authentication. It contains these sections:
Note
•
Understanding Web-Based Authentication, page 9-1
•
Configuring Web-Based Authentication, page 9-9
•
Displaying Web-Based Authentication Status, page 9-17
For complete syntax and usage information for the switch commands used in this chapter, refer to the
command reference for this release.
Understanding Web-Based Authentication
Use the web-based authentication feature, known as web authentication proxy, to authenticate end users
on host systems that do not run the IEEE 802.1x supplicant.
Note
You can configure web-based authentication on Layer 2 and Layer 3 interfaces.
When you initiate an HTTP session, web-based authentication intercepts ingress HTTP packets from the
host and sends an HTML login page to the users. The users enter their credentials, which the web-based
authentication feature sends to the authentication, authorization, and accounting (AAA) server for
authentication.
If authentication succeeds, web-based authentication sends a Login-Successful HTML page to the host
and applies the access policies returned by the AAA server.
If authentication fails, web-based authentication forwards a Login-Fail HTML page to the user,
prompting the user to retry the login. If the user exceeds the maximum number of attempts, web-based
authentication forwards a Login-Expired HTML page to the host, and the user is placed on a watch list
for a waiting period.
These sections describe the role of web-based authentication as part of AAA:
•
Device Roles, page 9-2
•
Host Detection, page 9-2
•
Session Creation, page 9-3
•
Authentication Process, page 9-3
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Configuring Web-Based Authentication
Understanding Web-Based Authentication
•
Web Authentication Customizable Web Pages, page 9-6
•
Web-based Authentication Interactions with Other Features, page 9-7
Device Roles
With web-based authentication, the devices in the network have these specific roles:
•
Client—The device (workstation) that requests access to the LAN and the services and responds to
requests from the switch. The workstation must be running an HTML browser with Java Script
enabled.
•
Authentication server—Authenticates the client. The authentication server validates the identity of
the client and notifies the switch that the client is authorized to access the LAN and the switch
services or that the client is denied.
•
Switch—Controls the physical access to the network based on the authentication status of the client.
The switch acts as an intermediary (proxy) between the client and the authentication server,
requesting identity information from the client, verifying that information with the authentication
server, and relaying a response to the client.
Figure 9-1 shows the roles of these devices in a network:
Figure 9-1
Web-Based Authentication Device Roles
Catalyst switch
or
Cisco Router
Authentication
server
(RADIUS)
79549
Workstations
(clients)
Host Detection
The switch maintains an IP device tracking table to store information about detected hosts.
Note
By default, the IP device tracking feature is disabled on a switch. You must enable the IP device tracking
feature to use web-based authentication.
For Layer 2 interfaces, web-based authentication detects IP hosts by using these mechanisms:
•
ARP based trigger—ARP redirect ACL allows web-based authentication to detect hosts with a static
IP address or a dynamic IP address.
•
Dynamic ARP inspection
•
DHCP snooping—Web-based authentication is notified when the switch creates a DHCP-binding
entry for the host.
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Configuring Web-Based Authentication
Understanding Web-Based Authentication
Session Creation
When web-based authentication detects a new host, it creates a session as follows:
•
Reviews the exception list.
If the host IP is included in the exception list, the policy from the exception list entry is applied, and
the session is established.
•
Reviews for authorization bypass
If the host IP is not on the exception list, web-based authentication sends a nonresponsive-host
(NRH) request to the server.
If the server response is access accepted, authorization is bypassed for this host. The session is
established.
•
Sets up the HTTP intercept ACL
If the server response to the NRH request is access rejected, the HTTP intercept ACL is activated,
and the session waits for HTTP traffic from the host.
Authentication Process
When you enable web-based authentication, these events occur:
•
The user initiates an HTTP session.
•
The HTTP traffic is intercepted, and authorization is initiated. The switch sends the login page to
the user. The user enters a username and password, and the switch sends the entries to the
authentication server.
•
If the authentication succeeds, the switch downloads and activates the user’s access policy from the
authentication server. The login success page is sent to the user.
•
If the authentication fails, the switch sends the login fail page. The user retries the login. If the
maximum number of attempts fails, the switch sends the login expired page, and the host is placed
in a watch list. After the watch list times out, the user can retry the authentication process.
•
If the authentication server does not respond to the switch, and if an AAA fail policy is configured,
the switch applies the failure access policy to the host. The login success page is sent to the user.
(See the “Local Web Authentication Banner” section on page 9-4.)
•
The switch reauthenticates a client when the host does not respond to an ARP probe on a Layer 2
interface, or when the host does not send any traffic within the idle timeout on a Layer 3 interface.
•
The feature applies the downloaded timeout or the locally configured session timeout.
•
If the terminate action is RADIUS, the feature sends a nonresponsive host (NRH) request to the
server. The terminate action is included in the response from the server.
•
If the terminate action is default, the session is dismantled, and the applied policy is removed.
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Local Web Authentication Banner
You can create a banner that will appear when you log in to a switch by using web authentication.
The banner appears on both the login page and the authentication-result pop-up pages.
•
Authentication Successful
•
Authentication Failed
•
Authentication Expired
You create a banner by using the ip admission auth-proxy-banner http global configuration command.
The default banner Cisco Systems and Switch host-name Authentication appear on the Login Page. Cisco
Systems appears on the authentication result pop-up page, as shown in Figure 9-2.
Figure 9-2
Authentication Successful Banner
You can also customize the banner, as shown in Figure 9-3.
•
Add a switch, router, or company name to the banner by using the ip admission auth-proxy-banner
http banner-text global configuration command.
•
Add a logo or text file to the banner by using the ip admission auth-proxy-banner http file-path
global configuration command.
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Figure 9-3
Customized Web Banner
If you do not enable a banner, only the username and password dialog boxes appear in the web
authentication login screen, and no banner appears when you log into the switch, as shown in Figure 9-4.
Figure 9-4
Login Screen With No Banner
For more information, see the Cisco IOS Security Command Reference and the “Configuring a Web
Authentication Local Banner” section on page 9-16.
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Web Authentication Customizable Web Pages
During the web-based authentication process, the switch internal HTTP server hosts four HTML pages
to deliver to an authenticating client. The server uses these pages to notify you of these
four-authentication process states:
•
Login—Your credentials are requested.
•
Success—The login was successful.
•
Fail—The login failed.
•
Expire—The login session has expired because of excessive login failures.
•
You can substitute your own HTML pages for the default internal HTML pages.
•
You can use a logo or specify text in the login, success, failure, and expire web pages.
•
On the banner page, you can specify text in the login page.
•
The pages are in HTML.
•
You must include an HTML redirect command in the success page to access a specific URL.
•
The URL string must be a valid URL (for example, http://www.cisco.com). An incomplete URL
might cause page not found or similar errors on a web browser.
•
If you configure web pages for HTTP authentication, they must include the appropriate HTML
commands (for example, to set the page time out, to set a hidden password, or to confirm that the
same page is not submitted twice).
•
The CLI command to redirect users to a specific URL is not available when the configured login
form is enabled. The administrator should ensure that the redirection is configured in the web page.
•
If the CLI command redirecting users to specific URL after authentication occurs is entered and then
the command configuring web pages is entered, the CLI command redirecting users to a specific
URL does not take effect.
•
Configured web pages can be copied to the switch boot flash or flash.
•
The login page can be on one flash, and the success and failure pages can be another flash (for
example, the flash on the stack master or a member).
•
You must configure all four pages.
•
The banner page has no effect if it is configured with the web page.
•
All of the logo files (image, flash, audio, video, and so on) that are stored in the system directory
(for example, flash, disk0, or disk) and that must be displayed on the login page must use
web_auth_<filename> as the file name.
•
The configured authentication proxy feature supports both HTTP and SSL.
Guidelines
You can substitute your HTML pages, as shown inFigure 9-5 on page 9-7, for the default internal HTML
pages. You can also specify a URL to which users are redirected after authentication occurs, which
replaces the internal Success page.
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Figure 9-5
Customizeable Authentication Page
For more information, see the “Customizing the Authentication Proxy Web Pages” section on page 9-14.
Web-based Authentication Interactions with Other Features
•
Port Security, page 9-7
•
LAN Port IP, page 9-8
•
Gateway IP, page 9-8
•
ACLs, page 9-8
•
Context-Based Access Control, page 9-8
•
802.1x Authentication, page 9-8
•
EtherChannel, page 9-8
Port Security
You can configure web-based authentication and port security on the same port. Web-based
authentication authenticates the port, and port security manages network access for all MAC addresses,
including that of the client. You can then limit the number or group of clients that can access the network
through the port.
For more information about enabling port security, see “Configuring Port Security” section on
page 24-8.
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LAN Port IP
You can configure LAN port IP (LPIP) and Layer 2 web-based authentication on the same port. The host
is authenticated by using web-based authentication first, followed by LPIP posture validation. The LPIP
host policy overrides the web-based authentication host policy.
If the web-based authentication idle timer expires, the NAC policy is removed. The host is authenticated,
and posture is validated again.
Gateway IP
You cannot configure Gateway IP (GWIP) on a Layer 3 VLAN interface if web-based authentication is
configured on any of the switch ports in the VLAN.
You can configure web-based authentication on the same Layer 3 interface as Gateway IP. The host
policies for both features are applied in software. The GWIP policy overrides the web-based
authentication host policy.
ACLs
If you configure a VLAN ACL or a Cisco IOS ACL on an interface, the ACL is applied to the host traffic
only after the web-based authentication host policy is applied.
For Layer 2 web-based authentication, you must configure a port ACL (PACL) as the default access
policy for ingress traffic from hosts connected to the port. After authentication, the web-based
authentication host policy overrides the PACL.
Note
When a proxy ACL is configured for a web-based authentication client, the proxy ACL is downloaded
and applied as part of the authorization process. Hence, the PACL displays the proxy ACL access control
entry (ACE).
You cannot configure a MAC ACL and web-based authentication on the same interface.
You cannot configure web-based authentication on a port whose access VLAN is configured for VACL
capture.
Context-Based Access Control
Web-based authentication cannot be configured on a Layer 2 port if context-based access control
(CBAC) is configured on the Layer 3 VLAN interface of the port VLAN.
802.1x Authentication
We recommend that you not configure web-based authentication on the same port as 802.1x
authentication except as a fallback authentication method.
EtherChannel
You can configure web-based authentication on a Layer 2 EtherChannel interface. The web-based
authentication configuration applies to all member channels.
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Configuring Web-Based Authentication
Configuring Web-Based Authentication
•
Default Web-Based Authentication Configuration, page 9-9
•
Web-Based Authentication Configuration Guidelines and Restrictions, page 9-9
•
Web-Based Authentication Configuration Task List, page 9-10
•
Configuring the Authentication Rule and Interfaces, page 9-10
•
Configuring AAA Authentication, page 9-11
•
Configuring Switch-to-RADIUS-Server Communication, page 9-12
•
Configuring the HTTP Server, page 9-13
•
Configuring the Web-Based Authentication Parameters, page 9-16
•
Removing Web-Based Authentication Cache Entries, page 9-17
Default Web-Based Authentication Configuration
Table 9-1 shows the default web-based authentication configuration.
Table 9-1
Default Web-based Authentication Configuration
Feature
Default Setting
AAA
Disabled
RADIUS server
•
IP address
•
None specified
•
UDP authentication port
•
1812
•
Key
•
None specified
Default value of inactivity timeout
3600 seconds
Inactivity timeout
Enabled
Web-Based Authentication Configuration Guidelines and Restrictions
•
Web-based authentication is an ingress-only feature.
•
You can configure web-based authentication only on access ports. Web-based authentication is not
supported on trunk ports, EtherChannel member ports, or dynamic trunk ports.
•
You must configure the default ACL on the interface before configuring web-based authentication.
Configure a port ACL for a Layer 2 interface or a Cisco IOS ACL for a Layer 3 interface.
•
You cannot authenticate hosts on Layer 2 interfaces with static ARP cache assignment. These hosts
are not detected by the web-based authentication feature because they do not send ARP messages.
•
By default, the IP device tracking feature is disabled on a switch. You must enable the IP device
tracking feature to use web-based authentication.
•
You must configure at least one IP address to run the switch HTTP server. You must also configure
routes to reach each host IP address. The HTTP server sends the HTTP login page to the host.
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•
Hosts that are more than one hop away might experience traffic disruption if an STP topology
change results in the host traffic arriving on a different port. This occurs because the ARP and DHCP
updates might not be sent after a Layer 2 (STP) topology change.
•
Web-based authentication does not support VLAN assignment as a downloadable-host policy.
•
Web-based authentication is not supported for IPv6 traffic.
•
Web-based authentication and Network Edge Access Topology (NEAT) are mutually exclusive. You
cannot use web-based authentication when NEAT is enabled on an interface, and you cannot use
NEAT when web-based authentication is running on an interface.
•
Web-based authentication supports only RADIUS authorization servers. You cannot use TACACS+
servers or local authorization.
Web-Based Authentication Configuration Task List
•
Configuring the Authentication Rule and Interfaces, page 9-10
•
Configuring AAA Authentication, page 9-11
•
Configuring Switch-to-RADIUS-Server Communication, page 9-12
•
Configuring the HTTP Server, page 9-13
•
Configuring the Web-Based Authentication Parameters, page 9-16
•
Configuring a Web Authentication Local Banner, page 9-16
•
Removing Web-Based Authentication Cache Entries, page 9-17
Configuring the Authentication Rule and Interfaces
Command
Purpose
Step 1
ip admission name name proxy http
Configure an authentication rule for web-based authorization.
Step 2
interface type slot/port
Enter interface configuration mode and specifies the ingress Layer 2 or
Layer 3 interface to be enabled for web-based authentication.
type can be fastethernet, gigabit ethernet, or tengigabitethernet.
Step 3
ip access-group name
Apply the default ACL.
Step 4
ip admission name
Configure web-based authentication on the specified interface.
Step 5
exit
Return to configuration mode.
Step 6
ip device tracking
Enable the IP device tracking table.
Step 7
end
Return to privileged EXEC mode.
Step 8
show ip admission configuration
Display the configuration.
Step 9
copy running-config startup-config
(Optional) Save your entries in the configuration file.
This example shows how to enable web-based authentication on Fast Ethernet port 5/1:
Switch(config)# ip admission name webauth1 proxy http
Switch(config)# interface fastethernet 5/1
Switch(config-if)# ip admission webauth1
Switch(config-if)# exit
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Switch(config)# ip device tracking
This example shows how to verify the configuration:
Switch# show ip admission configuration
Authentication Proxy Banner not configured
Authentication global cache time is 60 minutes
Authentication global absolute time is 0 minutes
Authentication global init state time is 2 minutes
Authentication Proxy Watch-list is disabled
Authentication Proxy Rule Configuration
Auth-proxy name webauth1
http list not specified inactivity-time 60 minutes
Authentication Proxy Auditing is disabled
Max Login attempts per user is 5
Configuring AAA Authentication
Command
Purpose
Step 1
aaa new-model
Enables AAA functionality.
Step 2
aaa authentication login default group {tacacs+ Defines the list of authentication methods at login.
| radius}
Step 3
aaa authorization auth-proxy default group
{tacacs+ | radius}
Create an authorization method list for web-based
authorization.
Step 4
radius-server host {hostname | ip-address} test
username username
Specify an AAA server.
Specify the host name or IP address of the remote RADIUS
server.
The test username username option enables automated testing
of the RADIUS server connection. The specified username does
not need to be a valid user name.
Step 5
Step 6
radius-server key string
Configure the authorization and encryption key used between
the switch and the RADIUS daemon running on the RADIUS
server. To use multiple RADIUS servers, reenter this command
for each server.
copy running-config startup-config
(Optional) Save your entries in the configuration file.
This example shows how to enable AAA:
Switch(config)# aaa new-model
Switch(config)# aaa authentication login default group radius
Switch(config)# aaa authorization auth-proxy default group radius
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Configuring Switch-to-RADIUS-Server Communication
RADIUS security servers identification:
•
Host name
•
Host IP address
•
Host name and specific UDP port numbers
•
IP address and specific UDP port numbers
The combination of the IP address and UDP port number creates a unique identifier, that enables
RADIUS requests to be sent to multiple UDP ports on a server at the same IP address. If two different
host entries on the same RADIUS server are configured for the same service (for example,
authentication) the second host entry that is configured functions as the failover backup to the first one.
The RADIUS host entries are chosen in the order that they were configured.
To configure the RADIUS server parameters, perform this task:
Command
Purpose
Step 1
ip radius source-interface interface_name
Specify that the RADIUS packets have the IP address of
the indicated interface.
Step 2
radius-server host {hostname | ip-address} test
username username
Specify the host name or IP address of the remote
RADIUS server.
The test username username option enables automated
testing of the RADIUS server connection. The specified
username does not need to be a valid user name.
The key option specifies an authentication and encryption
key to use between the switch and the RADIUS server.
To use multiple RADIUS servers, reenter this command
for each server.
Step 3
radius-server key string
Configure the authorization and encryption key used
between the switch and the RADIUS daemon running on
the RADIUS server.
Step 4
radius-server vsa send authentication
Enable downloading of an ACL from the RADIUS server.
This feature is supported in
Cisco IOS Release 12.2(50)SG.
Step 5
radius-server dead-criteria tries num-tries
Specify the number of unanswered sent messages to a
RADIUS server before considering the server to be
inactive. The range of num-tries is 1 to 100.
When you configure the RADIUS server parameters:
•
Specify the key string on a separate command line.
•
For key string, specify the authentication and encryption key used between the switch and the
RADIUS daemon running on the RADIUS server. The key is a text string that must match the
encryption key used on the RADIUS server.
•
When you specify the key string, use spaces within and at the end of the key. If you use spaces in
the key, do not enclose the key in quotation marks unless the quotation marks are part of the key.
This key must match the encryption used on the RADIUS daemon.
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•
You can globally configure the timeout, retransmission, and encryption key values for all RADIUS
servers by using with the radius-server host global configuration command. If you want to
configure these options on a per-server basis, use the radius-server timeout, radius-server
retransmit, and the radius-server key global configuration commands. For more information, see
the
Cisco IOS Security Configuration Guide, Release 12.2 and the
Cisco IOS Security Command Reference, Release 12.2 at this URL:
http://www.cisco.com/en/US/docs/ios/12_2/security/command/reference/fsecur_r.html
Note
You need to configure some settings on the RADIUS server, including: the switch IP address, the key
string to be shared by both the server and the switch, and the downloadable ACL (DACL). For more
information, see the RADIUS server documentation.
This example shows how to configure the RADIUS server parameters on a switch:
Switch(config)#
Switch(config)#
Switch(config)#
Switch(config)#
ip radius source-interface Vlan80
radius-server host 172.l20.39.46 test username user1
radius-server key rad123
radius-server dead-criteria tries 2
Configuring the HTTP Server
To use web-based authentication, you must enable the HTTP server within the switch. You can enable
the server for either HTTP or HTTPS.
Command
Purpose
Step 1
ip http server
Enable the HTTP server. The web-based authentication feature uses the HTTP server
to communicate with the hosts for user authentication.
Step 2
ip http secure-server
Enable HTTPS.
You can configure custom authentication proxy web pages or specify a redirection URL for successful
login.
Note
To ensure secure authentication when you enter the ip http secure-secure command, the login page is
always in HTTPS (secure HTTP) even if the user sends an HTTP request.
•
Customizing the Authentication Proxy Web Pages
•
Specifying a Redirection URL for Successful Login
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Customizing the Authentication Proxy Web Pages
You can configure web authentication to display four substitute HTML pages to the user in place of the
switch default HTML pages during web-based authentication.
To specify the use of your custom authentication proxy web pages, first store your custom HTML files
on the switch flash memory, then perform this task in global configuration mode:
Command
Purpose
Step 1
ip admission proxy http login page file
device:login-filename
Specify the location in the switch memory file system of
the custom HTML file to use in place of the default login
page. The device: is flash memory.
Step 2
ip admission proxy http success page file
device:success-filename
Specify the location of the custom HTML file to use in
place of the default login success page.
Step 3
ip admission proxy http failure page file
device:fail-filename
Specify the location of the custom HTML file to use in
place of the default login failure page.
Step 4
ip admission proxy http login expired page file
device:expired-filename
Specify the location of the custom HTML file to use in
place of the default login expired page.
When configuring customized authentication proxy web pages, follow these guidelines:
•
To enable the custom web pages feature, specify all four custom HTML files. If you specify fewer
than four files, the internal default HTML pages are used.
•
The four custom HTML files must be present on the flash memory of the switch. The maximum size
of each HTML file is 8 KB.
•
Any images on the custom pages must be on an accessible HTTP server. Configure an intercept ACL
within the admission rule.
•
Any external link from a custom page requires configuration of an intercept ACL within the
admission rule.
•
T o access a valid DNS server, any name resolution required for external links or images requires
configuration of an intercept ACL within the admission rule.
•
If the custom web pages feature is enabled, a configured auth-proxy-banner is not used.
•
If the custom web pages feature is enabled, the redirection URL for successful login feature is not
available.
•
To remove the specification of a custom file, use the no form of the command.
Because the custom login page is a public web form, consider these guidelines for the page:
•
The login form must accept user entries for the username and password and must show them as
uname and pwd.
•
The custom login page should follow best practices for a web form, such as page timeout, hidden
password, and prevention of redundant submissions.
This example shows how to configure custom authentication proxy web pages:
Switch(config)#
Switch(config)#
Switch(config)#
Switch(config)#
ip
ip
ip
ip
admission
admission
admission
admission
proxy
proxy
proxy
proxy
http
http
http
http
login page file flash:login.htm
success page file flash:success.htm
fail page file flash:fail.htm
login expired page flash flash:expired.htm
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This example shows how to verify the configuration of a custom authentication proxy web pages:
Switch# show ip admission configuration
Authentication proxy webpage
Login page
: flash:login.htm
Success page
: flash:success.htm
Fail Page
: flash:fail.htm
Login expired Page
: flash:expired.htm
Authentication global cache time is 60 minutes
Authentication global absolute time is 0 minutes
Authentication global init state time is 2 minutes
Authentication Proxy Session ratelimit is 100
Authentication Proxy Watch-list is disabled
Authentication Proxy Auditing is disabled
Max Login attempts per user is 5
Specifying a Redirection URL for Successful Login
You can specify a URL to which the user is redirected after authentication, effectively replacing the
internal Success HTML page.
Command
Purpose
ip admission proxy http success redirect url-string
Specify a URL for redirection of the user in place of the
default login success page.
When configuring a redirection URL for successful login, consider these guidelines:
•
If the custom authentication proxy web pages feature is enabled, the redirection URL feature is
disabled and is not available in the CLI. You can perform redirection in the custom-login success
page.
•
If the redirection URL feature is enabled, a configured auth-proxy-banner is not used.
•
To remove the specification of a redirection URL, use the no form of the command.
This example shows how to configure a redirection URL for successful login:
Switch(config)# ip admission proxy http success redirect www.cisco.com
This example shows how to verify the redirection URL for successful login:
Switch# show ip admission configuration
Authentication Proxy Banner not configured
Customizable Authentication Proxy webpage not configured
HTTP Authentication success redirect to URL: http://www.cisco.com
Authentication global cache time is 60 minutes
Authentication global absolute time is 0 minutes
Authentication global init state time is 2 minutes
Authentication Proxy Watch-list is disabled
Authentication Proxy Max HTTP process is 7
Authentication Proxy Auditing is disabled
Max Login attempts per user is 5
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Configuring the Web-Based Authentication Parameters
You can configure the maximum number of failed login attempts before the client is placed in a watch
list for a waiting period.
Command
Purpose
Step 1
ip admission max-login-attempts number
Set the maximum number of failed login attempts. The
range is 1 to 2147483647 attempts. The default is 5.
Step 2
end
Returns to privileged EXEC mode.
Step 3
show ip admission configuration
Display the authentication proxy configuration.
Step 4
show ip admission cache
Display the list of authentication entries.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
This example shows how to set the maximum number of failed login attempts to 10:
Switch(config)# ip admission max-login-attempts 10
Configuring a Web Authentication Local Banner
Beginning in privileged EXEC mode, follow these steps to configure a local banner on a switch that has
web authentication configured.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
ip admission auth-proxy-banner http
[banner-text | file-path]
Enable the local banner.
Step 3
end
Return to privileged EXEC mode.
Step 4
copy running-config startup-config
(Optional) Save your entries in the configuration file.
(Optional) Create a custom banner by entering C banner-text C, where
C is a delimiting character or a file-path indicates a file (for example, a
logo or text file) that appears in the banner.
This example shows how to configure a local banner with the custom message My Switch:
Switch(config) configure terminal
Switch(config)# aaa new-model
Switch(config)# aaa ip auth-proxy auth-proxy-banner C My Switch C
Switch(config) end
For more information about the ip auth-proxy auth-proxy-banner command, see the “Authentication
Proxy Commands” section of the Cisco IOS Security Command Reference on Cisco.com.
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Removing Web-Based Authentication Cache Entries
Command
Purpose
clear ip auth-proxy cache {* | host ip address}
Delete authentication proxy entries. Use an asterisk to
delete all cache entries. Enter a specific IP address to
delete the entry for a single host.
clear ip admission cache {* | host ip address}
Delete authentication proxy entries. Use an asterisk to
delete all cache entries. Enter a specific IP address to
delete the entry for a single host.
This example shows how to remove the web-based authentication session for the client at the IP
address 209.165.201.1:
Switch# clear ip auth-proxy cache 209.165.201.1
Displaying Web-Based Authentication Status
Perform this task to display the web-based authentication settings for all interfaces or for specific ports:
Step 1
Command
Purpose
show authentication sessions
[interface type slot/port]
Displays the web-based authentication settings.
type = fastethernet, gigabitethernet, or tengigabitethernet
(Optional) Use the interface keyword to display the
web-based authentication settings for a specific interface.
This example shows how to view only the global web-based authentication status:
Switch# show authentication sessions
This example shows how to view the web-based authentication settings for gigabit interface 3/27:
Switch# show authentication sessions interface gigabitethernet 3/2
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10
Configuring Interface Characteristics
This chapter defines the types of interfaces on the switch and describes how to configure them. The
chapter consists of these sections:
Note
•
Understanding Interface Types, page 10-1
•
Using Interface Configuration Mode, page 10-7
•
Configuring Ethernet Interfaces, page 10-11
•
Configuring Layer 3 Interfaces, page 10-17
•
Configuring the System MTU, page 10-20
•
Monitoring and Maintaining the Interfaces, page 10-21
For complete syntax and usage information for the commands used in this chapter, see the switch
command reference for this release and the online Cisco IOS Interface Command Reference,
Release 12.2.
Understanding Interface Types
This section describes the different types of interfaces supported by the switch with references to
chapters that contain more detailed information about configuring these interface types. The rest of the
chapter describes configuration procedures for physical interface characteristics.
These sections describe the interface types:
•
Port-Based VLANs, page 10-2
•
Switch Ports, page 10-2
•
Routed Ports, page 10-4
•
Switch Virtual Interfaces, page 10-4
•
EtherChannel Port Groups, page 10-6
•
Connecting Interfaces, page 10-6
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Understanding Interface Types
Port-Based VLANs
A VLAN is a switched network that is logically segmented by function, team, or application, without
regard to the physical location of the users. For more information about VLANs, see Chapter 12,
“Configuring VLANs.” Packets received on a port are forwarded only to ports that belong to the same
VLAN as the receiving port. Network devices in different VLANs cannot communicate with one another
without a Layer 3 device to route traffic between the VLANs.
VLAN partitions provide hard firewalls for traffic in the VLAN, and each VLAN has its own MAC
address table. A VLAN comes into existence when a local port is configured to be associated with the
VLAN, when the VLAN Trunking Protocol (VTP) learns of its existence from a neighbor on a trunk, or
when a user creates a VLAN.
To configure VLANs, use the vlan vlan-id global configuration command to enter VLAN configuration
mode. The VLAN configurations for normal-range VLANs (VLAN IDs 1 to 1005) are saved in the
VLAN database. If VTP is version 1 or 2, to configure extended-range VLANs (VLAN IDs 1006 to
4094), you must first set VTP mode to transparent. Extended-range VLANs created in transparent mode
are not added to the VLAN database but are saved in the switch running configuration. With VTP
version 3, you can create extended-range VLANs in client or server mode. These VLANs are saved in
the VLAN database.
Add ports to a VLAN by using the switchport interface configuration commands:
•
Identify the interface.
•
For a trunk port, set trunk characteristics, and if desired, define the VLANs to which it can belong.
•
For an access port, set and define the VLAN to which it belongs.
•
For a tunnel port, set and define the VLAN ID for the customer-specific VLAN tag. See Chapter 16,
“Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling.”
Switch Ports
Switch ports are Layer 2-only interfaces associated with a physical port. Switch ports belong to one or
more VLANs. A switch port can be an access port, a trunk port, or a tunnel port. You can configure a port
as an access port or trunk port or let the Dynamic Trunking Protocol (DTP) operate on a per-port basis
to set the switchport mode by negotiating with the port on the other end of the link. You must manually
configure tunnel ports as part of an asymmetric link connected to an IEEE 802.1Q trunk port. Switch
ports are used for managing the physical interface and associated Layer 2 protocols and do not handle
routing.
Configure switch ports by using the switchport interface configuration commands. Use the switchport
command with no keywords to put an interface that is in Layer 3 mode into Layer 2 mode.
Note
When you put an interface that is in Layer 3 mode into Layer 2 mode, the previous configuration
information related to the affected interface might be lost, and the interface is returned to its default
configuration.
For detailed information about configuring access port and trunk port characteristics, see Chapter 12,
“Configuring VLANs.” For more information about tunnel ports, see Chapter 16, “Configuring IEEE
802.1Q and Layer 2 Protocol Tunneling.”
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Access Ports
An access port belongs to and carries the traffic of only one VLAN (unless it is configured as a voice
VLAN port). Traffic is received and sent in native formats with no VLAN tagging. Traffic arriving on
an access port is assumed to belong to the VLAN assigned to the port. If an access port receives a tagged
packet (Inter-Switch Link [ISL] or IEEE 802.1Q tagged), the packet is dropped, and the source address
is not learned.
Two types of access ports are supported:
•
Static access ports are manually assigned to a VLAN (or through a RADIUS server for use with
IEEE 802.1x. For more information, see the “802.1x Authentication with VLAN Assignment”
section on page 8-16.)
•
VLAN membership of dynamic access ports is learned through incoming packets. By default, a
dynamic access port is not a member of any VLAN, and forwarding to and from the port is enabled
only when the VLAN membership of the port is discovered. Dynamic access ports on the switch are
assigned to a VLAN by a VLAN Membership Policy Server (VMPS). The VMPS can be a
Catalyst 6500 series switch; the Cisco Catalyst Blade Switch 3030 for Dell cannot be a VMPS
server.
You can also configure an access port with an attached Cisco IP Phone to use one VLAN for voice traffic
and another VLAN for data traffic from a device attached to the phone. For more information about voice
VLAN ports, see Chapter 14, “Configuring Voice VLAN.”
Trunk Ports
A trunk port carries the traffic of multiple VLANs and by default is a member of all VLANs in the VLAN
database. These trunk port types are supported:
•
In an ISL trunk port, all received packets are expected to be encapsulated with an ISL header, and
all transmitted packets are sent with an ISL header. Native (non-tagged) frames received from an
ISL trunk port are dropped.
•
An IEEE 802.1Q trunk port supports simultaneous tagged and untagged traffic. An IEEE 802.1Q
trunk port is assigned a default port VLAN ID (PVID), and all untagged traffic travels on the port
default PVID. All untagged traffic and tagged traffic with a NULL VLAN ID are assumed to belong
to the port default PVID. A packet with a VLAN ID equal to the outgoing port default PVID is sent
untagged. All other traffic is sent with a VLAN tag.
Although by default, a trunk port is a member of every VLAN known to the VTP, you can limit VLAN
membership by configuring an allowed list of VLANs for each trunk port. The list of allowed VLANs
does not affect any other port but the associated trunk port. By default, all possible VLANs (VLAN ID 1
to 4094) are in the allowed list. A trunk port can become a member of a VLAN only if VTP knows of
the VLAN and if the VLAN is in the enabled state. If VTP learns of a new, enabled VLAN and the VLAN
is in the allowed list for a trunk port, the trunk port automatically becomes a member of that VLAN and
traffic is forwarded to and from the trunk port for that VLAN. If VTP learns of a new, enabled VLAN
that is not in the allowed list for a trunk port, the port does not become a member of the VLAN, and no
traffic for the VLAN is forwarded to or from the port.
For more information about trunk ports, see Chapter 12, “Configuring VLANs.”
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Tunnel Ports
Tunnel ports are used in IEEE 802.1Q tunneling to segregate the traffic of customers in a
service-provider network from other customers who are using the same VLAN number. You configure
an asymmetric link from a tunnel port on a service-provider edge switch to an IEEE 802.1Q trunk port
on the customer switch. Packets entering the tunnel port on the edge switch, already
IEEE 802.1Q-tagged with the customer VLANs, are encapsulated with another layer of an IEEE 802.1Q
tag (called the metro tag), containing a VLAN ID unique in the service-provider network, for each
customer. The double-tagged packets go through the service-provider network keeping the original
customer VLANs separate from those of other customers. At the outbound interface, also a tunnel port,
the metro tag is removed, and the original VLAN numbers from the customer network are retrieved.
Tunnel ports cannot be trunk ports or access ports and must belong to a VLAN unique to each customer.
For more information about tunnel ports, see Chapter 16, “Configuring IEEE 802.1Q and Layer 2
Protocol Tunneling.”
Routed Ports
A routed port is a physical port that acts like a port on a router; it does not have to be connected to a
router. A routed port is not associated with a particular VLAN, as is an access port. A routed port behaves
like a regular router interface, except that it does not support VLAN subinterfaces. Routed ports can be
configured with a Layer 3 routing protocol. A routed port is a Layer 3 interface only and does not support
Layer 2 protocols, such as DTP and STP.
Configure routed ports by putting the interface into Layer 3 mode with the no switchport interface
configuration command. Then assign an IP address to the port, enable routing, and assign routing
protocol characteristics by using the ip routing and router protocol global configuration commands.
Note
Entering a no switchport interface configuration command shuts down the interface and then re-enables
it, which might generate messages on the device to which the interface is connected. When you put an
interface that is in Layer 2 mode into Layer 3 mode, the previous configuration information related to
the affected interface might be lost.
The number of routed ports that you can configure is not limited by software. However, the
interrelationship between this number and the number of other features being configured might impact
CPU performance because of hardware limitations. See the “Configuring Layer 3 Interfaces” section on
page 10-17 for information about what happens when hardware resource limitations are reached.
For more information about IP unicast routing and routing protocols, see Chapter 36, “Configuring IP
Unicast Routing.”
Switch Virtual Interfaces
A switch virtual interface (SVI) represents a VLAN of switch ports as one interface to the routing or
bridging function in the system. Only one SVI can be associated with a VLAN, but you need to configure
an SVI for a VLAN only when you wish to route between VLANs, to fallback-bridge nonroutable
protocols between VLANs, or to provide IP host connectivity to the switch. By default, an SVI is created
for the default VLAN (VLAN 1) to permit remote switch administration. Additional SVIs must be
explicitly configured.
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Note
You cannot delete interface VLAN 1.
SVIs provide IP host connectivity only to the system; in Layer 3 mode, you can configure routing across
SVIs.
Although the switch supports a total or 1005 VLANs (and SVIs), the interrelationship between the
number of SVIs and routed ports and the number of other features being configured might impact CPU
performance because of hardware limitations. See the “Configuring Layer 3 Interfaces” section on
page 10-17 for information about what happens when hardware resource limitations are reached.
SVIs are created the first time that you enter the vlan interface configuration command for a VLAN
interface. The VLAN corresponds to the VLAN tag associated with data frames on an ISL or
IEEE 802.1Q encapsulated trunk or the VLAN ID configured for an access port. Configure a VLAN
interface for each VLAN for which you want to route traffic, and assign it an IP address. For more
information, see the “Manually Assigning IP Information” section on page 3-14.
Note
When you create an SVI, it does not become active until it is associated with a physical port.
SVIs support routing protocols and bridging configurations. For more information about configuring IP
routing, see Chapter 36, “Configuring IP Unicast Routing.”
SVI Autostate Exclude
The line state of an SVI with multiple ports on a VLAN is in the up state when it meets these conditions:
Note
•
The VLAN exists and is active in the VLAN database on the switch.
•
The VLAN interface exists and is not administratively down.
•
At least one Layer 2 (access or trunk) port exists, has a link in the up state on this VLAN, and is in
the spanning-tree forwarding state on the VLAN.
The protocol link state for VLAN interfaces come up when the first switchport belonging to the
corresponding VLAN link comes up and is in STP forwarding state.
The default action, when a VLAN has multiple ports, is that the SVI goes down when all ports in the
VLAN go down. You can use the SVI autostate exclude feature to configure a port so that it is not
included in the SVI line-state up-an- down calculation. For example, if the only active port on the VLAN
is a monitoring port, you might configure autostate exclude on that port so that the VLAN goes down
when all other ports go down. When enabled on a port, autostate exclude applies to all VLANs that are
enabled on that port.
The VLAN interface is brought up when one Layer 2 port in the VLAN has had time to converge
(transition from STP listening-learning state to forwarding state). This prevents features such as routing
protocols from using the VLAN interface as if it were fully operational and minimizes other problems,
such as routing black holes. For information about configuring autostate exclude, see the “Configuring
SVI Autostate Exclude” section on page 10-19.
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EtherChannel Port Groups
EtherChannel port groups treat multiple switch ports as one switch port. These port groups act as a single
logical port for high-bandwidth connections between switches or between switches and servers. An
EtherChannel balances the traffic load across the links in the channel. If a link within the EtherChannel
fails, traffic previously carried over the failed link changes to the remaining links. You can group
multiple trunk ports into one logical trunk port or multiple access ports into one logical access port.
Most protocols operate over either single ports or aggregated switch ports and do not recognize the
physical ports within the port group. Exceptions are the DTP, the Cisco Discovery Protocol (CDP), and
the Port Aggregation Protocol (PAgP), which operate only on physical ports.
When you configure an EtherChannel, you create a port-channel logical interface and assign an interface
to the EtherChannel. For Layer 3 interfaces, you manually create the logical interface by using the
interface port-channel global configuration command. Then you manually assign an interface to the
EtherChannel by using the channel-group interface configuration command. For Layer 2 interfaces, use
the channel-group interface configuration command to dynamically create the port-channel logical
interface. This command binds the physical and logical ports together. For more information, see
Chapter 35, “Configuring EtherChannels and Layer 2 Trunk Failover.”
Connecting Interfaces
Devices within a single VLAN can communicate directly through any switch. Ports in different VLANs
cannot exchange data without going through a routing device. In the configuration shown in Figure 10-1,
when Blade Server A in VLAN 20 sends data to Blade Server B in VLAN 30, the data must go from
Blade Server A to the switch, to the router, back to the switch, and then to Blade Server B.
Figure 10-1
Connecting VLANs with Layer 2 Switches
Cisco router
Blade Switch
Blade
Server A
VLAN 30
119645
VLAN 20
Blade
Server B
By using the switch with routing enabled, when you configure both VLAN 20 and VLAN 30 with an
SVI to which an IP address is assigned, packets can be sent from Host A to Host B directly through the
switch with no need for an external router.
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Using Interface Configuration Mode
The switch supports basic routing (static routing and RIP). Whenever possible, to maintain high
performance, forwarding is done by the switch hardware. However, only IP Version 4 packets with
Ethernet II encapsulation can be routed in hardware. Non-IP traffic and traffic with other encapsulation
methods can be fallback-bridged by hardware.
The routing function can be enabled on all SVIs and routed ports. The switch routes only IP traffic. When
IP routing protocol parameters and address configuration are added to an SVI or routed port, any IP
traffic received from these ports is routed. For more information, see Chapter 36, “Configuring IP
Unicast Routing.”
Using Interface Configuration Mode
The switch supports these interface types:
•
Physical ports—switch ports and routed ports
•
VLANs—switch virtual interfaces
•
Port channels—EtherChannel interfaces
You can also configure a range of interfaces (see the “Configuring a Range of Interfaces” section on
page 10-8).
To configure a physical interface (port), specify the interface type, module number, and switch port number,
and enter interface configuration mode.
•
Type—Gigabit Ethernet (gigabitethernet or gi) for 10/100/1000 Mb/s Ethernet port or small
form-factor pluggable (SFP) module Gigabit Ethernet interfaces.
•
Module number—The module or slot number on the switch (always 0 on the Cisco Catalyst Blade
Switch 3030 for Dell).
•
Port number—The interface number of the switch port. The port numbers of the internal Gigabit
Ethernet ports are from 1 to 10 (for example, gigabitethernet 0/6). The port numbers of the two
10/100/1000 ports on the front of the switch are 11 and 12 (for example, gigabitethernet 0/11). The
port numbers of the SFP module ports are from 13 to16 (for example, gigabitethernet 0/14).
You can identify physical interfaces by physically checking the interface location on the switch. You can
also use the show privileged EXEC commands to display information about a specific interface or all
the interfaces on the switch. The remainder of this chapter primarily provides physical interface
configuration procedures.
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Procedures for Configuring Interfaces
These general instructions apply to all interface configuration processes.
Step 1
Enter the configure terminal command at the privileged EXEC prompt:
Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)#
Step 2
Enter the interface global configuration command. Identify the interface type and the number of the
connector. In this example, Gigabit Ethernet port 1 is selected:
Switch(config)# interface gigabitethernet0/1
Switch(config-if)#
Note
Step 3
You do not need to add a space between the interface type and interface number. For example,
in the preceding line, you can specify either gigabitethernet 0/1, gigabitethernet0/1, gi 0/1, or
gi0/1.
Follow each interface command with the interface configuration commands that the interface requires.
The commands that you enter define the protocols and applications that will run on the interface. The
commands are collected and applied to the interface when you enter another interface command or enter
end to return to privileged EXEC mode.
You can also configure a range of interfaces by using the interface range or interface range macro
global configuration commands. Interfaces configured in a range must be the same type and must be
configured with the same feature options.
Step 4
After you configure an interface, verify its status by using the show privileged EXEC commands listed
in the “Monitoring and Maintaining the Interfaces” section on page 10-21.
Enter the show interfaces privileged EXEC command to see a list of all interfaces on or configured for
the switch. A report is provided for each interface that the device supports or for the specified interface.
Configuring a Range of Interfaces
You can use the interface range global configuration command to configure multiple interfaces with the
same configuration parameters. When you enter the interface-range configuration mode, all command
parameters that you enter are attributed to all interfaces within that range until you exit this mode.
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Beginning in privileged EXEC mode, follow these steps to configure a range of interfaces with the
same parameters:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface range {port-range | macro
macro_name}
Specify the range of interfaces (VLANs or physical ports) to be
configured, and enter interface-range configuration mode.
Step 3
•
You can use the interface range command to configure up to five
port ranges or a previously defined macro.
•
The macro variable is explained in the “Configuring and Using
Interface Range Macros” section on page 10-10.
•
In a comma-separated port-range, you must enter the interface
type for each entry and enter spaces before and after the comma.
•
In a hyphen-separated port-range, you do not need to re-enter the
interface type, but you must enter a space before the hyphen.
Use the normal configuration commands to apply the configuration
parameters to all interfaces in the range. Each command is executed
as it is entered.
Step 4
end
Return to privileged EXEC mode.
Step 5
show interfaces [interface-id]
Verify the configuration of the interfaces in the range.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
When using the interface range global configuration command, note these guidelines:
•
Valid entries for port-range:
– vlan vlan-ID - vlan-ID, where the VLAN ID is 1 to 4094
– gigabitethernet module/{first port} - {last port}, where the module is always 0
– port-channel port-channel-number - port-channel-number, where the port-channel-number
is 1 to 48
Note
When you use the interface range command with port channels, the first and last
port-channel number must be active port channels.
•
You must add a space between the first interface number and the hyphen when using the
interface range command. For example, the command interface range gigabitethernet0/1 - 4 is a
valid range; the command interface range gigabitethernet0/1-4 is not a valid range.
•
The interface range command only works with VLAN interfaces that have been configured with
the interface vlan command. The show running-config privileged EXEC command displays the
configured VLAN interfaces. VLAN interfaces not displayed by the show running-config
command cannot be used with the interface range command.
•
All interfaces defined in a range must be the same type (all Gigabit Ethernet ports, all EtherChannel
ports, or all VLANs), but you can enter multiple ranges in a command.
This example shows how to use the interface range global configuration command to set the speed on
ports 1 to 4 to 100 Mb/s:
Switch# configure terminal
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Switch(config)# interface range gigabitethernet0/1 - 4
Switch(config-if-range)# speed 100
If you enter multiple configuration commands while you are in interface-range mode, each command is
executed as it is entered. The commands are not batched and executed after you exit interface-range
mode. If you exit interface-range configuration mode while the commands are being executed, some
commands might not be executed on all interfaces in the range. Wait until the command prompt
reappears before exiting interface-range configuration mode.
Configuring and Using Interface Range Macros
You can create an interface range macro to automatically select a range of interfaces for configuration.
Before you can use the macro keyword in the interface range macro global configuration command
string, you must use the define interface-range global configuration command to define the macro.
Beginning in privileged EXEC mode, follow these steps to define an interface range macro:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
define interface-range macro_name
interface-range
Define the interface-range macro, and save it in NVRAM.
Step 3
interface range macro macro_name
•
The macro_name is a 32-character maximum character string.
•
A macro can contain up to five comma-separated interface ranges.
•
Each interface-range must consist of the same port type.
Select the interface range to be configured using the values saved in
the interface-range macro called macro_name.
You can now use the normal configuration commands to apply the
configuration to all interfaces in the defined macro.
Step 4
end
Return to privileged EXEC mode.
Step 5
show running-config | include define
Show the defined interface range macro configuration.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Use the no define interface-range macro_name global configuration command to delete a macro.
When using the define interface-range global configuration command, note these guidelines:
•
Valid entries for interface-range:
– vlan vlan-ID- vlan-ID, where the VLAN ID is 1 to 4094
– gigabitethernet module/{first port} - {last port}, where the module is always 0
– port-channel port-channel-number - port-channel-number, where the port-channel-number
is 1 to 48.
Note
•
When you use the interface ranges with port channels, the first and last port-channel
number must be active port channels.
You must add a space between the first interface number and the hyphen when entering an
interface-range. For example, gigabitethernet0/1 - 4 is a valid range; gigabitethernet0/1-4 is not
a valid range.
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Configuring Ethernet Interfaces
•
The VLAN interfaces must have been configured with the interface vlan command. The show
running-config privileged EXEC command displays the configured VLAN interfaces. VLAN
interfaces not displayed by the show running-config command cannot be used as interface-ranges.
•
All interfaces defined as in a range must be the same type (all Gigabit Ethernet ports, all
EtherChannel ports, or all VLANs), but you can combine multiple interface types in a macro.
This example shows how to define an interface-range named enet_list to include ports 1 and 2 and to
verify the macro configuration:
Switch# configure terminal
Switch(config)# define interface-range enet_list gigabitethernet0/1 - 2
Switch(config)# end
Switch# show running-config | include define
define interface-range enet_list GigabitEthernet0/1 - 2
This example shows how to create a multiple-interface macro named macro1:
Switch# configure terminal
Switch(config)# define interface-range macro1 gigabitethernet0/1 - 2, gigabitethernet0/11
- 16
Switch(config)# end
This example shows how to enter interface-range configuration mode for the interface-range
macro enet_list:
Switch# configure terminal
Switch(config)# interface range macro enet_list
Switch(config-if-range)#
This example shows how to delete the interface-range macro enet_list and to verify that it was deleted.
Switch# configure terminal
Switch(config)# no define interface-range enet_list
Switch(config)# end
Switch# show run | include define
Switch#
Configuring Ethernet Interfaces
These sections contain this configuration information:
•
Default Ethernet Interface Configuration, page 10-12
•
Configuring Interface Speed and Duplex Mode, page 10-13
•
Configuring IEEE 802.3x Flow Control, page 10-15
•
Configuring Auto-MDIX on an Interface, page 10-16
•
Adding a Description for an Interface, page 10-17
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Default Ethernet Interface Configuration
Table 10-1 shows the Ethernet interface default configuration, including some features that apply only
to Layer 2 interfaces. For more details on the VLAN parameters listed in the table, see Chapter 12,
“Configuring VLANs.” For details on controlling traffic to the port, see Chapter 24, “Configuring
Port-Based Traffic Control.”
Note
To configure Layer 2 parameters, if the interface is in Layer 3 mode, you must enter the switchport
interface configuration command without any parameters to put the interface into Layer 2 mode. This
shuts down the interface and then re-enables it, which might generate messages on the device to which
the interface is connected. When you put an interface that is in Layer 3 mode into Layer 2 mode, the
previous configuration information related to the affected interface might be lost, and the interface is
returned to its default configuration.
Table 10-1
Default Layer 2 Ethernet Interface Configuration
Feature
Default Setting
Operating mode
Layer 2 or switching mode (switchport command).
Allowed VLAN range
VLANs 1 to 4094.
Default VLAN (for access ports)
VLAN 1 (Layer 2 interfaces only).
Native VLAN (for IEEE 802.1Q
trunks)
VLAN 1 (Layer 2 interfaces only).
VLAN trunking
Switchport mode dynamic auto (supports DTP) (Layer 2 interfaces
only).
Port enable state
All ports are enabled.
Port description
None defined.
Speed
Autonegotiate.
Duplex mode
Autonegotiate.
Flow control
Flow control is set to receive: off. It is always off for sent packets.
EtherChannel (PAgP)
Disabled on all Ethernet ports. See Chapter 35, “Configuring
EtherChannels and Layer 2 Trunk Failover.”
Port blocking (unknown multicast Disabled (not blocked) (Layer 2 interfaces only). See the
and unknown unicast traffic)
“Configuring Port Blocking” section on page 24-7.
Broadcast, multicast, and unicast
storm control
Disabled. See the “Default Storm Control Configuration” section
on page 24-3.
Protected port
Disabled (Layer 2 interfaces only). See the “Configuring Protected
Ports” section on page 24-6.
Port security
Disabled (Layer 2 interfaces only). See the “Default Port Security
Configuration” section on page 24-11.
Port Fast
Disabled. See the “Default Optional Spanning-Tree
Configuration” section on page 19-9.
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Table 10-1
Default Layer 2 Ethernet Interface Configuration (continued)
Feature
Default Setting
Auto-MDIX
Enabled.
Note
Keepalive messages
The switch might not support a pre-standard powered
device—such as Cisco IP phones and access points that do
not fully support IEEE 802.3af—if that powered device is
connected to the switch through a crossover cable. This is
regardless of whether auto-MIDX is enabled on the switch
port.
Disabled on SFP module ports; enabled on all other ports.
Configuring Interface Speed and Duplex Mode
Ethernet interfaces on the switch operate at 10, 100, or 1000 Mb/s and in either full- or half-duplex mode.
In full-duplex mode, two stations can send and receive traffic at the same time. Normally, 10-Mb/s ports
operate in half-duplex mode, which means that stations can either receive or send traffic.
Switch models include Gigabit Ethernet (10/100/1000-Mb/s) ports and small form-factor pluggable
(SFP) module slots supporting SFP modules.
These sections describe how to configure the interface speed and duplex mode:
•
Speed and Duplex Configuration Guidelines, page 10-13
•
Setting the Interface Speed and Duplex Parameters, page 10-14
Speed and Duplex Configuration Guidelines
When configuring an interface speed and duplex mode, note these guidelines:
•
Gigabit Ethernet (10/100/1000-Mb/s) ports support all speed options and all duplex options (auto,
half, and full). However, Gigabit Ethernet ports operating at 1000 Mb/s do not support half-duplex
mode.
•
For SFP module ports, the speed and duplex CLI options change depending on the SFP module type:
– The 1000BASE-x (where -x is -BX, -CWDM, -LX, -SX, and -ZX) SFP module ports support
the nonegotiate keyword in the speed interface configuration command. Duplex options are not
supported.
– The 1000BASE-T SFP module ports support the same speed and duplex options as the
10/100/1000-Mbps ports.
– The 100BASE-x (where -x is -BX, -CWDM, -LX, -SX, and -ZX) SFP module ports support only
100 Mbps. These modules support full- and half- duplex options but do not support
autonegotiation.
For information about which SFP modules are supported on your switch, see the product
release notes.
•
You cannot configure duplex mode on SFP module ports; they operate in full-duplex mode except
in these situations:
– You can configure Cisco 1000BASE-T SFP modules for auto, full, or half-duplex mode.
– Cisco 1000BASE-SX SFP modules can operate only in full-duplex mode.
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Configuring Ethernet Interfaces
Caution
•
If you are connected to a device that does not support autonegotiation, you can configure speed on
copper SFP module ports; however, you can only configure fiber SFP module ports to not negotiate
(nonegotiate).
•
If both ends of the line support autonegotiation, we highly recommend the default setting of auto
negotiation.
•
If one interface supports autonegotiation and the other end does not, configure duplex and speed on
both interfaces; do not use the auto setting on the supported side.
•
When STP is enabled and a port is reconfigured, the switch can take up to 30 seconds to check for
loops. The port LED is amber while STP reconfigures.
Changing the interface speed and duplex mode configuration might shut down and re-enable the
interface during the reconfiguration.
Setting the Interface Speed and Duplex Parameters
Beginning in privileged EXEC mode, follow these steps to set the speed and duplex mode for a physical
interface:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify the physical interface to be configured, and enter interface
configuration mode.
Step 3
speed {10 | 100 | 1000 | auto [10 | 100 |
1000] | nonegotiate}
Enter the appropriate speed parameter for the interface:
•
Enter 10, 100, or 1000 to set a specific speed for the interface.
The 1000 keyword is available only for 10/100/1000 Mb/s ports.
•
Enter auto to enable the interface to autonegotiate speed with the
connected device. If you use the 10, 100, or the 1000 keywords
with the auto keyword, the port autonegotiates only at the
specified speeds.
•
The nonegotiate keyword is available only for SFP module ports.
SFP module ports operate only at 1000 Mb/s but can be
configured to not negotiate if connected to a device that does not
support autonegotiation.
For more information about speed settings, see the “Speed and Duplex
Configuration Guidelines” section on page 10-13.
Step 4
duplex {auto | full | half}
Enter the duplex parameter for the interface.
Enable half-duplex mode (for interfaces operating only at 10 or
100 Mb/s). You cannot configure half-duplex mode for interfaces
operating at 1000 Mb/s.
For more information about duplex settings, see the “Speed and
Duplex Configuration Guidelines” section on page 10-13.
Step 5
Step 6
Step 7
end
Return to privileged EXEC mode.
show interfaces interface-id
Display the interface speed and duplex mode configuration.
copy running-config startup-config
(Optional) Save your entries in the configuration file.
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Configuring Ethernet Interfaces
Use the no speed and no duplex interface configuration commands to return the interface to the default
speed and duplex settings (autonegotiate). To return all interface settings to the defaults, use the default
interface interface-id interface configuration command.
This example shows how to set the interface speed to 100 Mb/s on a 10/100/1000 Mb/s port:
Switch# configure terminal
Switch(config)# interface gigabitethernet0/2
Switch(config-if)# speed 100
Configuring IEEE 802.3x Flow Control
Flow control enables connected Ethernet ports to control traffic rates during congestion by allowing
congested nodes to pause link operation at the other end. If one port experiences congestion and cannot
receive any more traffic, it notifies the other port by sending a pause frame to stop sending until the
condition clears. Upon receipt of a pause frame, the sending device stops sending any data packets,
which prevents any loss of data packets during the congestion period.
Note
Cisco Catalyst Blade Switch 3030 for Dellports can receive, but not send, pause frames.
You use the flowcontrol interface configuration command to set the interface’s ability to receive pause
frames to on, off, or desired. The default state is off.
When set to desired, an interface can operate with an attached device that is required to send
flow-control packets or with an attached device that is not required to but can send flow-control packets.
These rules apply to flow control settings on the device:
Note
•
receive on (or desired): The port cannot send pause frames but can operate with an attached device
that is required to or can send pause frames; the port can receive pause frames.
•
receive off: Flow control does not operate in either direction. In case of congestion, no indication is
given to the link partner, and no pause frames are sent or received by either device.
For details on the command settings and the resulting flow control resolution on local and remote ports,
see the flowcontrol interface configuration command in the command reference for this release.
Beginning in privileged EXEC mode, follow these steps to configure flow control on an interface:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode
Step 2
interface interface-id
Specify the physical interface to be configured, and enter
interface configuration mode.
Step 3
flowcontrol {receive} {on | off | desired}
Configure the flow control mode for the port.
Step 4
end
Return to privileged EXEC mode.
Step 5
show interfaces interface-id
Verify the interface flow control settings.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
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Configuring Ethernet Interfaces
To disable flow control, use the flowcontrol receive off interface configuration command.
This example shows how to turn on flow control on a port:
Switch# configure terminal
Switch(config)# interface gigabitethernet0/1
Switch(config-if)# flowcontrol receive on
Switch(config-if)# end
Configuring Auto-MDIX on an Interface
When automatic medium-dependent interface crossover (auto-MDIX) is enabled on an interface, the
interface automatically detects the required cable connection type (straight through or crossover) and
configures the connection appropriately. When connecting switches without the auto-MDIX feature, you
must use straight-through cables to connect to devices such as servers, workstations, or routers and
crossover cables to connect to other switches or repeaters. With auto-MDIX enabled, you can use either
type of cable to connect to other devices, and the interface automatically corrects for any incorrect
cabling. For more information about cabling requirements, see the hardware installation guide.
Auto-MDIX is enabled by default. When you enable auto-MDIX, you must also set the interface speed
and duplex to auto so that the feature operates correctly. Auto-MDIX is supported on all
10/100/1000-Mb/s interfaces and on 10/100/1000BASE-T SFP-module interfaces. It is not supported on
1000BASE-SX or -LX SFP module interfaces.
Table 10-2 shows the link states that result from auto-MDIX settings and correct and incorrect cabling.
Table 10-2
Link Conditions and Auto-MDIX Settings
Local Side Auto-MDIX
Remote Side Auto-MDIX With Correct Cabling
With Incorrect Cabling
On
On
Link up
Link up
On
Off
Link up
Link up
Off
On
Link up
Link up
Off
Off
Link up
Link down
Beginning in privileged EXEC mode, follow these steps to configure auto-MDIX on an interface:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode
Step 2
interface interface-id
Specify the physical interface to be configured, and enter interface
configuration mode.
Step 3
speed auto
Configure the interface to autonegotiate speed with the connected device.
Step 4
duplex auto
Configure the interface to autonegotiate duplex mode with the connected
device.
Step 5
mdix auto
Enable auto-MDIX on the interface.
Step 6
end
Return to privileged EXEC mode.
Step 7
show controllers ethernet-controller Verify the operational state of the auto-MDIX feature on the interface.
interface-id phy
Step 8
copy running-config startup-config
(Optional) Save your entries in the configuration file.
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Configuring Layer 3 Interfaces
To disable auto-MDIX, use the no mdix auto interface configuration command.
This example shows how to enable auto-MDIX on a port:
Switch# configure terminal
Switch(config)# interface gigabitethernet0/1
Switch(config-if)# speed auto
Switch(config-if)# duplex auto
Switch(config-if)# mdix auto
Switch(config-if)# end
Adding a Description for an Interface
You can add a description about an interface to help you remember its function. The description appears
in the output of these privileged EXEC commands: show configuration, show running-config, and
show interfaces.
Beginning in privileged EXEC mode, follow these steps to add a description for an interface:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify the interface for which you are adding a description, and enter
interface configuration mode.
Step 3
description string
Add a description (up to 240 characters) for an interface.
Step 4
end
Return to privileged EXEC mode.
Step 5
show interfaces interface-id description Verify your entry.
or
show running-config
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Use the no description interface configuration command to delete the description.
This example shows how to add a description on a port and how to verify the description:
Switch# config terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# interface gigabitethernet0/2
Switch(config-if)# description Connects to Marketing
Switch(config-if)# end
Switch# show interfaces gigabitethernet0/2 description
Interface Status
Protocol Description
Gi0/2
admin down
down
Connects to Marketing
Configuring Layer 3 Interfaces
The switch supports these types of Layer 3 interfaces:
•
SVIs: You should configure SVIs for any VLANs for which you want to route traffic. SVIs are
created when you enter a VLAN ID following the interface vlan global configuration command. To
delete an SVI, use the no interface vlan global configuration command. You cannot delete interface
VLAN 1.
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Configuring Layer 3 Interfaces
Note
When you create an SVI, it does not become active until it is associated with a physical port.
For information about assigning Layer 2 ports to VLANs, see Chapter 12, “Configuring
VLANs.”
When configuring SVIs, you can also configure SVI autostate exclude on a port in the SVI to
exclude that port from being included in determining SVI line-state status. See the “Configuring SVI
Autostate Exclude” section on page 10-19.
•
Routed ports: Routed ports are physical ports configured to be in Layer 3 mode by using the no
switchport interface configuration command.
•
Layer 3 EtherChannel ports: EtherChannel interfaces made up of routed ports.
EtherChannel port interfaces are described in Chapter 35, “Configuring EtherChannels and Layer 2
Trunk Failover.”
A Layer 3 switch can have an IP address assigned to each routed port and SVI.
There is no defined limit to the number of SVIs and routed ports that can be configured in a switch stack.
However, the interrelationship between the number of SVIs and routed ports and the number of other
features being configured might have an impact on CPU usage because of hardware limitations. If the
switch is using maximum hardware resources, attempts to create a routed port or SVI have these results:
•
If you try to create a new routed port, the switch generates a message that there are not enough
resources to convert the interface to a routed port, and the interface remains as a switchport.
•
If you try to create an extended-range VLAN, an error message is generated, and the extended-range
VLAN is rejected.
•
If the switch is notified by VLAN Trunking Protocol (VTP) of a new VLAN, it sends a message that
there are not enough hardware resources available and shuts down the VLAN. The output of the
show vlan user EXEC command shows the VLAN in a suspended state.
•
If the switch attempts to boot up with a configuration that has more VLANs and routed ports than
hardware can support, the VLANs are created, but the routed ports are shut down, and the switch
sends a message that this was due to insufficient hardware resources.
All Layer 3 interfaces require an IP address to route traffic. This procedure shows how to configure an
interface as a Layer 3 interface and how to assign an IP address to an interface.
Note
If the physical port is in Layer 2 mode (the default), you must enter the no switchport interface
configuration command to put the interface into Layer 3 mode. Entering a no switchport command
disables and then re-enables the interface, which might generate messages on the device to which the
interface is connected. Furthermore, when you put an interface that is in Layer 2 mode into Layer 3
mode, the previous configuration information related to the affected interface might be lost, and the
interface is returned to its default configuration
Beginning in privileged EXEC mode, follow these steps to configure a Layer 3 interface:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface {{fastethernet | gigabitethernet} interface-id} Specify the interface to be configured as a Layer 3
| {vlan vlan-id} | {port-channel port-channel-number}
interface, and enter interface configuration mode.
Step 3
no switchport
For physical ports only, enter Layer 3 mode.
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Command
Purpose
Step 4
ip address ip_address subnet_mask
Configure the IP address and IP subnet.
Step 5
no shutdown
Enable the interface.
Step 6
end
Return to privileged EXEC mode.
Step 7
show interfaces [interface-id]
Verify the configuration.
show ip interface [interface-id]
show running-config interface [interface-id]
Step 8
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To remove an IP address from an interface, use the no ip address interface configuration command.
This example shows how to configure a port as a routed port and to assign it an IP address:
Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# interface gigabitethernet0/2
Switch(config-if)# no switchport
Switch(config-if)# ip address 192.20.135.21 255.255.255.0
Switch(config-if)# no shutdown
Configuring SVI Autostate Exclude
Configuring SVI autostate exclude on an access or trunk port in an SVI excludes that port in the
calculation of the status of the SVI line state (up or down) even if it belongs to the same VLAN. When
the excluded port is in the up state, and all other ports in the VLAN are in the down state, the SVI state
is changed to down.
At least one port in the VLAN should be up and not excluded to keep the SVI state up. You can use this
command to exclude the monitoring port status when determining the status of the SVI.
Beginning in privileged EXEC mode, follow these steps to exclude a port from SVI state-change
calculations:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify a Layer 2 interface (physical port or port
channel), and enter interface configuration mode.
Step 3
switchport autostate exclude
Exclude the access or trunk port when defining the
status of an SVI line state (up or down)
Step 4
end
Return to privileged EXEC mode.
Step 5
show running config interface interface-id
(Optional) Show the running configuration.
show interface interface-id switchport
Verify the configuration.
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Step 6
This example shows how to configure an access or trunk port in an SVI to be excluded from the status
calculation:
Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
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Configuring the System MTU
Switch(config)# interface gigabitethernet0/2
Switch(config-if)# switchport autostate exclude
Switch(config-if)# exit
Configuring the System MTU
The default maximum transmission unit (MTU) size for frames received and transmitted on all interfaces
on the switch is 1500 bytes. You can increase the MTU size for all interfaces operating at 10 or 100 Mb/s
by using the system mtu global configuration command. You can increase the MTU size to support
jumbo frames on all Gigabit Ethernet interfaces by using the system mtu jumbo global configuration
command. You can change the MTU size for routed ports by using the system mtu routing global
configuration command.
Note
You cannot configure a routing MTU size that exceeds the system MTU size. If you change the system
MTU size to a value smaller than the currently configured routing MTU size, the configuration change
is accepted, but not applied until the next switch reset. When the configuration change takes effect, the
routing MTU size automatically defaults to the new system MTU size.
Gigabit Ethernet ports are not affected by the system mtu command; 10/100 ports are not affected by
the system mtu jumbo command. If you do not configure the system mtu jumbo command, the setting
of the system mtu command applies to all Gigabit Ethernet interfaces.
You cannot set the MTU size for an individual interface; you set it for all 10/100 or all Gigabit Ethernet
interfaces on the switch. When you change the system or jumbo MTU size, you must reset the switch
before the new configuration takes effect.The system mtu routing command does not require a switch
reset to take effect.
Frames sizes that can be received by the switch CPU are limited to 1998 bytes, no matter what value was
entered with the system mtu or system mtu jumbo commands. Although frames that are forwarded or
routed are typically not received by the CPU, in some cases packets are sent to the CPU, such as traffic
sent to control traffic, SNMP, or Telnet, or routing protocols.
Routed packets are subjected to MTU checks on the output ports. The MTU value used for routed ports
is derived from the applied system mtu value (not the system mtu jumbo value). That is, the routed
MTU is never greater than the system MTU for any VLAN. The routing protocols use the system MTU
value when negotiating adjacencies and the MTU of the link. To view the MTU value for routed packets
for a specific VLAN, use the show platform port-asic mvid privileged EXEC command.
Note
If Layer 2 Gigabit Ethernet interfaces are configured to accept frames greater than the 10/100 interfaces,
jumbo frames received on a Layer 2 Gigabit Ethernet interface and sent on a Layer 2 10/100 interface
are dropped.
Beginning in privileged EXEC mode, follow these steps to change MTU size for all 10/100 or Gigabit
Ethernet interfaces:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
system mtu bytes
(Optional) Change the MTU size for all interfaces on
the switch that are operating at 10 or 100 Mb/s. The
range is 1500 to 1998 bytes; the default is 1500 bytes.
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Command
Purpose
Step 3
system mtu jumbo bytes
(Optional) Change the MTU size for all Gigabit
Ethernet interfaces on the switch. The range is 1500 to
9000 bytes; the default is 1500 bytes.
Step 4
system mtu routing bytes
(Optional) Change the system MTU for routed ports.
The range is 1500 to the system MTU value, the
maximum MTU that can be routed for all ports.
Although larger packets can be accepted, they cannot be
routed.
Step 5
end
Return to privileged EXEC mode.
Step 6
copy running-config startup-config
Save your entries in the configuration file.
Step 7
reload
Reload the operating system.
If you enter a value that is outside the allowed range for the specific type of interface, the value is not
accepted.
Once the switch reloads, you can verify your settings by entering the show system mtu privileged EXEC
command.
This example shows how to set the maximum packet size for a Gigabit Ethernet port to 1800 bytes:
Switch(config)# system mtu jumbo 1800
Switch(config)# exit
Switch# reload
This example shows the response when you try to set Gigabit Ethernet interfaces to an out-of-range
number:
Switch(config)# system mtu jumbo 25000
^
% Invalid input detected at '^' marker.
Monitoring and Maintaining the Interfaces
These sections contain interface monitoring and maintenance information:
•
Monitoring Interface Status, page 10-22
•
Clearing and Resetting Interfaces and Counters, page 10-22
•
Shutting Down and Restarting the Interface, page 10-23
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Monitoring and Maintaining the Interfaces
Monitoring Interface Status
Commands entered at the privileged EXEC prompt display information about the interface, including
the versions of the software and the hardware, the configuration, and statistics about the interfaces.
Table 10-3 lists some of these interface monitoring commands. (You can display the full list of show
commands by using the show ? command at the privileged EXEC prompt.) These commands are fully
described in the Cisco IOS Interface Command Reference, Release 12.2.
Table 10-3
Show Commands for Interfaces
Command
Purpose
show interfaces [interface-id]
Display the status and configuration of all interfaces or a specific
interface.
show interfaces interface-id status [err-disabled]
Display interface status or a list of interfaces in an error-disabled state.
show interfaces [interface-id] switchport
Display administrative and operational status of switching
(nonrouting) ports. You can use this command to find out if a port is in
routing or in switching mode.
show interfaces [interface-id] description
Display the description configured on an interface or all interfaces and
the interface status.
show ip interface [interface-id]
Display the usability status of all interfaces configured for IP routing
or the specified interface.
show interface [interface-id] stats
Display the input and output packets by the switching path for the
interface.
show interfaces transceiver properties
(Optional) Display speed and duplex settings on the interface.
show interfaces [interface-id] [{transceiver
properties | detail}] module number]
Display physical and operational status about an SFP module.
show running-config interface [interface-id]
Display the running configuration in RAM for the interface.
show version
Display the hardware configuration, software version, the names and
sources of configuration files, and the bootup images.
show controllers ethernet-controller interface-id
phy
Display the operational state of the auto-MDIX feature on the
interface.
Clearing and Resetting Interfaces and Counters
Table 10-4 lists the privileged EXEC mode clear commands that you can use to clear counters and reset
interfaces.
Table 10-4
Clear Commands for Interfaces
Command
Purpose
clear counters [interface-id]
Clear interface counters.
clear interface interface-id
Reset the hardware logic on an interface.
clear line [number | console 0 | vty number]
Reset the hardware logic on an asynchronous serial line.
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Monitoring and Maintaining the Interfaces
To clear the interface counters shown by the show interfaces privileged EXEC command, use the clear
counters privileged EXEC command. The clear counters command clears all current interface counters
from the interface unless you specify optional arguments that clear only a specific interface type from a
specific interface number.
Note
The clear counters privileged EXEC command does not clear counters retrieved by using Simple
Network Management Protocol (SNMP), but only those seen with the show interface privileged EXEC
command.
Shutting Down and Restarting the Interface
Shutting down an interface disables all functions on the specified interface and marks the interface as
unavailable on all monitoring command displays. This information is communicated to other network
servers through all dynamic routing protocols. The interface is not mentioned in any routing updates.
Beginning in privileged EXEC mode, follow these steps to shut down an interface:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface {vlan vlan-id} | {{gigabitethernet} interface-id} | Select the interface to be configured.
{port-channel port-channel-number}
Step 3
shutdown
Shut down an interface.
Step 4
end
Return to privileged EXEC mode.
Step 5
show running-config
Verify your entry.
Use the no shutdown interface configuration command to restart the interface.
To verify that an interface is disabled, enter the show interfaces privileged EXEC command. A disabled
interface is shown as administratively down in the display.
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11
Configuring Smartports Macros
This chapter describes how to configure and apply Smartports macros on the switch.
Note
For complete syntax and usage information for the commands used in this chapter, see the command
reference for this release.
This chapter consists of these sections:
•
Understanding Smartports Macros, page 11-1
•
Configuring Smartports Macros, page 11-2
•
Displaying Smartports Macros, page 11-8
Understanding Smartports Macros
Smartports macros provide a convenient way to save and share common configurations. You can use
Smartports macros to enable features and settings based on the location of a switch in the network and
for mass configuration deployments across the network.
Each Smartports macro is a set of command-line interface (CLI) commands that you define. Smartports
macros do not contain new CLI commands; they are simply a group of existing CLI commands.
When you apply a Smartports macro on an interface, the CLI commands within the macro are configured
on the interface. When the macro is applied to an interface, the existing interface configurations are not
lost. The new commands are added to the interface and are saved in the running configuration file.
There are Cisco-default Smartports macros embedded in the switch software (see Table 11-1). You can
display these macros and the commands they contain by using the show parser macro user EXEC
command.
Table 11-1
Cisco-Default Smartports Macros
Macro Name1
Description
cisco-global
Use this global configuration macro to enable rapid PVST+, loop guard, and dynamic
port error recovery for link state failures.
cisco-desktop
Use this interface configuration macro for increased network security and reliability
when connecting a desktop device, such as a PC, to a switch port.
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Configuring Smartports Macros
Table 11-1
Cisco-Default Smartports Macros (continued)
Macro Name1
Description
cisco-phone
Use this interface configuration macro when connecting a desktop device such as a
PC with a Cisco IP Phone to a switch port. This macro is an extension of the
cisco-desktop macro and provides the same security and resiliency features, but with
the addition of dedicated voice VLANs to ensure proper treatment of delay-sensitive
voice traffic.
cisco-switch
Use this interface configuration macro when connecting an access switch and a
distribution switch or between access switches connected using small form-factor
pluggable (SFP) modules.
cisco-router
Use this interface configuration macro when connecting the switch and a WAN
router.
cisco-wireless
Use this interface configuration macro when connecting the switch and a wireless
access point.
1. Cisco-default Smartports macros vary depending on the software version running on your switch.
Configuring Smartports Macros
You can create a new Smartports macro or use an existing macro as a template to create a new macro
that is specific to your application. After you create the macro, you can apply it globally to a switch or
to a switch interface or range of interfaces.
These sections contain this configuration information:
•
Default Smartports Macro Configuration, page 11-2
•
Smartports Macro Configuration Guidelines, page 11-2
•
Creating Smartports Macros, page 11-4
•
Applying Smartports Macros, page 11-5
•
Applying Cisco-Default Smartports Macros, page 11-6
Default Smartports Macro Configuration
There are no Smartports macros enabled.
Smartports Macro Configuration Guidelines
Follow these guidelines when configuring macros on your switch:
•
When creating a macro, do not use the exit or end commands or change the command mode by using
interface interface-id. This could cause commands that follow exit, end, or interface interface-id
to execute in a different command mode.
•
When creating a macro, all CLI commands should be in the same configuration mode.
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Configuring Smartports Macros
•
When creating a macro that requires the assignment of unique values, use the parameter value
keywords to designate values specific to the interface. Keyword matching is case sensitive. All
matching occurrences of the keyword are replaced with the corresponding value. Any full match of
a keyword, even if it is part of a larger string, is considered a match and is replaced by the
corresponding value.
•
Macro names are case sensitive. For example, the commands macro name Sample-Macro and
macro name sample-macro will result in two separate macros.
•
Some macros might contain keywords that require a parameter value. You can use the macro global
apply macro-name ? global configuration command or the macro apply macro-name ? interface
configuration command to display a list of any required values in the macro. If you apply a macro
without entering the keyword values, the commands are invalid and are not applied.
•
When a macro is applied globally to a switch or to a switch interface, all existing configuration on
the interface is retained. This is helpful when applying an incremental configuration.
•
If you modify a macro definition by adding or deleting commands, the changes are not reflected on
the interface where the original macro was applied. You need to reapply the updated macro on the
interface to apply the new or changed commands.
•
You can use the macro global trace macro-name global configuration command or the macro trace
macro-name interface configuration command to apply and debug a macro to find any syntax or
configuration errors. If a command fails because of a syntax error or a configuration error, the macro
continues to apply the remaining commands.
•
Some CLI commands are specific to certain interface types. If a macro is applied to an interface that
does not accept the configuration, the macro will fail the syntax check or the configuration check,
and the switch will return an error message.
•
Applying a macro to an interface range is the same as applying a macro to a single interface. When
you use an interface range, the macro is applied sequentially to each interface within the range. If a
macro command fails on one interface, it is still applied to the remaining interfaces.
•
When you apply a macro to a switch or a switch interface, the macro name is automatically added
to the switch or interface. You can display the applied commands and macro names by using the
show running-config user EXEC command.
There are Cisco-default Smartports macros embedded in the switch software (see Table 11-1). You can
display these macros and the commands they contain by using the show parser macro user EXEC
command.
Follow these guidelines when you apply a Cisco-default Smartports macro on an interface:
•
Display all macros on the switch by using the show parser macro user EXEC command. Display
the contents of a specific macro by using the show parser macro macro-name user EXEC
command.
•
Keywords that begin with $ mean that a unique parameter value is required. Append the
Cisco-default macro with the required values by using the parameter value keywords.
The Cisco-default macros use the $ character to help identify required keywords. There is no
restriction on using the $ character to define keywords when you create a macro.
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Chapter 11
Configuring Smartports Macros
Configuring Smartports Macros
Creating Smartports Macros
Beginning in privileged EXEC mode, follow these steps to create a Smartports macro:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
macro name macro-name
Create a macro definition, and enter a macro name. A macro definition
can contain up to 3000 characters.
Enter the macro commands with one command per line. Use the @
character to end the macro. Use the # character at the beginning of a line
to enter comment text within the macro.
(Optional) You can define keywords within a macro by using a help
string to specify the keywords. Enter # macro keywords word to define
the keywords that are available for use with the macro. Separated by a
space, you can enter up to three help string keywords in a macro.
Macro names are case sensitive. For example, the commands macro
name Sample-Macro and macro name sample-macro will result in
two separate macros.
We recommend that you do not use the exit or end commands or change
the command mode by using interface interface-id in a macro. This
could cause any commands following exit, end, or interface
interface-id to execute in a different command mode. For best results,
all commands in a macro should be in the same configuration mode.
Step 3
end
Return to privileged EXEC mode.
Step 4
show parser macro name macro-name
Verify that the macro was created.
The no form of the macro name global configuration command only deletes the macro definition. It
does not affect the configuration of those interfaces on which the macro is already applied.
This example shows how to create a macro that defines the switchport access VLAN and the number of
secure MAC addresses and also includes two help string keywords by using # macro keywords:
Switch(config)# macro name test
switchport access vlan $VLANID
switchport port-security maximum $MAX
#macro keywords $VLANID $MAX
@
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Chapter 11
Configuring Smartports Macros
Configuring Smartports Macros
Applying Smartports Macros
Beginning in privileged EXEC mode, follow these steps to apply a Smartports macro:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
macro global {apply | trace}
macro-name [parameter {value}]
[parameter {value}] [parameter
{value}]
Apply each individual command defined in the macro to the switch by
entering macro global apply macro-name. Specify macro global trace
macro-name to apply and debug a macro to find any syntax or
configuration errors.
(Optional) Specify unique parameter values that are specific to the
switch. You can enter up to three keyword-value pairs. Parameter
keyword matching is case sensitive. All matching occurrences of the
keyword are replaced with the corresponding value.
Some macros might contain keywords that require a parameter value.
You can use the macro global apply macro-name ? command to display
a list of any required values in the macro. If you apply a macro without
entering the keyword values, the commands are invalid and are not
applied.
Step 3
macro global description text
(Optional) Enter a description about the macro that is applied to the
switch.
Step 4
interface interface-id
(Optional) Enter interface configuration mode, and specify the interface
on which to apply the macro.
Step 5
default interface interface-id
(Optional) Clear all configuration from the specified interface.
Step 6
macro {apply | trace} macro-name
[parameter {value}] [parameter
{value}] [parameter {value}]
Apply each individual command defined in the macro to the interface by
entering macro apply macro-name. Specify macro trace macro-name
to apply and debug a macro to find any syntax or configuration errors.
(Optional) Specify unique parameter values that are specific to the
interface. You can enter up to three keyword-value pairs. Parameter
keyword matching is case sensitive. All matching occurrences of the
keyword are replaced with the corresponding value.
Some macros might contain keywords that require a parameter value.
You can use the macro apply macro-name ? command to display a list
of any required values in the macro. If you apply a macro without
entering the keyword values, the commands are invalid and are not
applied.
Step 7
macro description text
(Optional) Enter a description about the macro that is applied to the
interface.
Step 8
end
Return to privileged EXEC mode.
Step 9
show parser macro description
[interface interface-id]
Verify that the macro is applied to the interface.
Step 10
copy running-config startup-config
(Optional) Save your entries in the configuration file.
You can delete a global macro-applied configuration on a switch only by entering the no version of each
command that is in the macro. You can delete a macro-applied configuration on an interface by entering
the default interface interface-id interface configuration command.
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Configuring Smartports Macros
Configuring Smartports Macros
This example shows how to apply the user-created macro called snmp, to set the hostname address to
test-server, and to set the IP precedence value to 7:
Switch(config)# macro global apply snmp ADDRESS test-server VALUE 7
This example shows how to debug the user-created macro called snmp by using the macro global trace
global configuration command to find any syntax or configuration errors in the macro when it is applied
to the switch.
Switch(config)# macro global trace snmp VALUE 7
Applying command...‘snmp-server enable traps port-security’
Applying command...‘snmp-server enable traps linkup’
Applying command...‘snmp-server enable traps linkdown’
Applying command...‘snmp-server host’
%Error Unknown error.
Applying command...‘snmp-server ip precedence 7’
This example shows how to apply the user-created macro called desktop-config and to verify the
configuration.
Switch(config)# interface gigabitethernet0/2
Switch(config-if)# macro apply desktop-config
Switch(config-if)# end
Switch# show parser macro description
Interface
Macro Description
-------------------------------------------------------------Gi0/2
desktop-config
--------------------------------------------------------------
This example shows how to apply the user-created macro called desktop-config and to replace all
occurrences of VLAN 1 with VLAN 25:
Switch(config-if)# macro apply desktop-config vlan 25
Applying Cisco-Default Smartports Macros
Beginning in privileged EXEC mode, follow these steps to apply a Smartports macro:
Command
Purpose
Step 1
show parser macro
Display the Cisco-default Smartports macros embedded in the switch
software.
Step 2
show parser macro macro-name
Display the specific macro that you want to apply.
Step 3
configure terminal
Enter global configuration mode.
Step 4
macro global {apply | trace}
macro-name [parameter {value}]
[parameter {value}] [parameter
{value}]
Append the Cisco-default macro with the required values by using the
parameter value keywords and apply the macro to the switch.
Keywords that begin with $ mean that a unique parameter value is
required.
You can use the macro global apply macro-name ? command to display
a list of any required values in the macro. If you apply a macro without
entering the keyword values, the commands are invalid and are not
applied.
Step 5
interface interface-id
(Optional) Enter interface configuration mode, and specify the interface
on which to apply the macro.
Step 6
default interface interface-id
(Optional) Clear all configuration from the specified interface.
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Configuring Smartports Macros
Configuring Smartports Macros
Step 7
Command
Purpose
macro {apply | trace} macro-name
[parameter {value}] [parameter
{value}] [parameter {value}]
Append the Cisco-default macro with the required values by using the
parameter value keywords, and apply the macro to the interface.
Keywords that begin with $ mean that a unique parameter value is
required.
You can use the macro apply macro-name ? command to display a list
of any required values in the macro. If you apply a macro without
entering the keyword values, the commands are invalid and are not
applied.
Step 8
end
Return to privileged EXEC mode.
Step 9
show running-config interface
interface-id
Verify that the macro is applied to an interface.
Step 10
copy running-config startup-config
(Optional) Save your entries in the configuration file.
You can delete a global macro-applied configuration on a switch only by entering the no version of each
command that is in the macro. You can delete a macro-applied configuration on an interface by entering
the default interface interface-id interface configuration command.
This example shows how to display the cisco-desktop macro, how to apply the macro, and to set the
access VLAN ID to 25 on an interface:
Switch# show parser macro cisco-desktop
-------------------------------------------------------------Macro name : cisco-desktop
Macro type : default
# Basic interface - Enable data VLAN only
# Recommended value for access vlan (AVID) should not be 1
switchport access vlan $AVID
switchport mode access
# Enable port security limiting port to a single
# MAC address -- that of desktop
switchport port-security
switchport port-security maximum 1
# Ensure port-security age is greater than one minute
# and use inactivity timer
switchport port-security violation restrict
switchport port-security aging time 2
switchport port-security aging type inactivity
# Configure port as an edge network port
spanning-tree portfast
spanning-tree bpduguard enable
-------------------------------------------------------------Switch#
Switch# configure terminal
Switch(config)# gigabitethernet0/4
Switch(config-if)# macro apply cisco-desktop $AVID 25
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Configuring Smartports Macros
Displaying Smartports Macros
Displaying Smartports Macros
To display the Smartports macros, use one or more of the privileged EXEC commands in Table 11-2.
Table 11-2
Commands for Displaying Smartports Macros
Command
Purpose
show parser macro
Displays all configured macros.
show parser macro name macro-name
Displays a specific macro.
show parser macro brief
Displays the configured macro names.
show parser macro description [interface
interface-id]
Displays the macro description for all interfaces or for a specified
interface.
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CH A P T E R
12
Configuring VLANs
This chapter describes how to configure normal-range VLANs (VLAN IDs 1 to 1005) and
extended-range VLANs (VLAN IDs 1006 to 4094) on the switch. It includes information about VLAN
membership modes, VLAN configuration modes, VLAN trunks, and dynamic VLAN assignment from
a VLAN Membership Policy Server (VMPS).
Note
For complete syntax and usage information for the commands used in this chapter, see the command
reference for this release.
The chapter consists of these sections:
•
Understanding VLANs, page 12-1
•
Configuring Normal-Range VLANs, page 12-4
•
Configuring Extended-Range VLANs, page 12-11
•
Displaying VLANs, page 12-14
•
Configuring VLAN Trunks, page 12-15
•
Configuring VMPS, page 12-26
Understanding VLANs
A VLAN is a switched network that is logically segmented by function, project team, or application,
without regard to the physical locations of the users. VLANs have the same attributes as physical LANs,
but you can group end stations even if they are not physically located on the same LAN segment. Any
switch port can belong to a VLAN, and unicast, broadcast, and multicast packets are forwarded and
flooded only to end stations in the VLAN. Each VLAN is considered a logical network, and packets
destined for stations that do not belong to the VLAN must be forwarded through a router or a switch
supporting fallback bridging, as shown in Figure 12-1. Because a VLAN is considered a separate logical
network, it contains its own bridge Management Information Base (MIB) information and can support
its own implementation of spanning tree. See Chapter 17, “Configuring STP.”
Note
Before you create VLANs, you must decide whether to use VLAN Trunking Protocol (VTP) to maintain
global VLAN configuration for your network. For more information on VTP, see Chapter 13,
“Configuring VTP.”
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Configuring VLANs
Understanding VLANs
Figure 12-1 shows an example of VLANs segmented into logically defined networks.
Figure 12-1
VLANs as Logically Defined Networks
Engineering
VLAN
Marketing
VLAN
Accounting
VLAN
Cisco router
Floor 3
Gigabit
Ethernet
Floor 2
90571
Floor 1
VLANs are often associated with IP subnetworks. For example, all the end stations in a particular IP
subnet belong to the same VLAN. Interface VLAN membership on the switch is assigned manually on
an interface-by-interface basis. When you assign switch interfaces to VLANs by using this method, it is
known as interface-based, or static, VLAN membership.
Traffic between VLANs must be routed or fallback bridged. The switch can route traffic between
VLANs by using switch virtual interfaces (SVIs). An SVI must be explicitly configured and assigned an
IP address to route traffic between VLANs. For more information, see the “Switch Virtual Interfaces”
section on page 10-4 and the “Configuring Layer 3 Interfaces” section on page 10-17.
Note
If you plan to configure many VLANs on the switch and to not enable routing, you can use the sdm
prefer vlan global configuration command to set the Switch Database Management (sdm) feature to the
VLAN template, which configures system resources to support the maximum number of unicast MAC
addresses. For more information on the SDM templates, see Chapter 6, “Configuring SDM Templates,”
or see the sdm prefer command in the command reference for this release.
Supported VLANs
The switch supports VLANs in VTP client, server, and transparent modes. VLANs are identified by a
number from 1 to 4094. VLAN IDs 1002 through 1005 are reserved for Token Ring and FDDI VLANs.
VTP version 1 and version 2 support only normal-range VLANs (VLAN IDs 1 to 1005). In these
versions, the switch must be in VTP transparent mode when you create VLAN IDs from 1006 to 4094.
Cisco IOS Release 12.2(52)SE and later support VTP version 3. VTP version 3 supports the entire
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Configuring VLANs
Understanding VLANs
VLAN range (VLANs 1 to 4094). Extended range VLANs (VLANs 1006 to 4094) are supported only in
VTP version 3. You cannot convert from VTP version 3 to VTP version 2 if extended VLANs are
configured in the domain.
Although the switch supports a total of 1005 (normal range and extended range) VLANs, the number of
routed ports, SVIs, and other configured features affects the use of the switch hardware.
The switch supports per-VLAN spanning-tree plus (PVST+) or rapid PVST+ with a maximum of 128
spanning-tree instances. One spanning-tree instance is allowed per VLAN. See the “Normal-Range
VLAN Configuration Guidelines” section on page 12-6 for more information about the number of
spanning-tree instances and the number of VLANs. The switch supports both Inter-Switch Link (ISL)
and IEEE 802.1Q trunking methods for sending VLAN traffic over Ethernet ports.
VLAN Port Membership Modes
You configure a port to belong to a VLAN by assigning a membership mode that specifies the kind of
traffic the port carries and the number of VLANs to which it can belong. Table 12-1 lists the membership
modes and membership and VTP characteristics.
Table 12-1
Port Membership Modes and Characteristics
Membership Mode
VLAN Membership Characteristics
VTP Characteristics
Static-access
A static-access port can belong to one VLAN and is
manually assigned to that VLAN.
VTP is not required. If you do not want
VTP to globally propagate information, set
the VTP mode to transparent. To
participate in VTP, there must be at least
one trunk port on the switch connected to a
trunk port of a second switch.
For more information, see the “Assigning Static-Access
Ports to a VLAN” section on page 12-10.
Trunk (ISL or
IEEE 802.1Q)
A trunk port is a member of all VLANs by default,
including extended-range VLANs, but membership can be
limited by configuring the allowed-VLAN list. You can
also modify the pruning-eligible list to block flooded
traffic to VLANs on trunk ports that are included in the
list.
For information about configuring trunk ports, see the
“Configuring an Ethernet Interface as a Trunk Port”
section on page 12-18.
Dynamic access
A dynamic-access port can belong to one VLAN (VLAN
ID 1 to 4094) and is dynamically assigned by a VMPS. The
VMPS can be a Catalyst 5000 or Catalyst 6500 series
switch, for example, but never a Cisco Catalyst Blade
Switch 3030 for Dell, which is a VMPS client.
VTP is recommended but not required.
VTP maintains VLAN configuration
consistency by managing the addition,
deletion, and renaming of VLANs on a
network-wide basis. VTP exchanges
VLAN configuration messages with other
switches over trunk links.
VTP is required.
Configure the VMPS and the client with the
same VTP domain name.
To participate in VTP, at least one trunk
port on the switch.
You can have dynamic-access ports and trunk ports on the
must be connected to a trunk port of a
same switch, but you must connect the dynamic-access
second switch.
port to an end station or hub and not to another switch.
For configuration information, see the “Configuring
Dynamic-Access Ports on VMPS Clients” section on
page 12-29.
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Configuring VLANs
Configuring Normal-Range VLANs
Membership Mode
VLAN Membership Characteristics
VTP Characteristics
Voice VLAN
A voice VLAN port is an access port attached to a Cisco VTP is not required; it has no effect on a
voice VLAN.
IP Phone, configured to use one VLAN for voice traffic
and another VLAN for data traffic from a device attached
to the phone.
For more information about voice VLAN ports, see
Chapter 14, “Configuring Voice VLAN.”
Private VLAN
A private VLAN port is a host or promiscuous port that
belongs to a private VLAN primary or secondary VLAN.
For information about private VLANs, see Chapter 15,
“Configuring Private VLANs.”
Tunnel
(dot1q-tunnel)
Tunnel ports are used for IEEE 802.1Q tunneling to
maintain customer VLAN integrity across a
service-provider network. You configure a tunnel port on
an edge switch in the service-provider network and
connect it to an IEEE 802.1Q trunk port on a customer
interface, creating an asymetric link. A tunnel port belongs
to a single VLAN that is dedicated to tunneling.
n VTP versions 1 and 2, the switch must be
in VTP transparent mode when you
configure private VLANs. When private
VLANs are configured on the switch, do
not change VTP mode from transparent to
client or server mode. VTP version 3
supports private VLANs in any mode.
VTP is not required. You manually assign
the tunnel port to a VLAN by using the
switchport access vlan interface
configuration command.
For more information about tunnel ports, see Chapter 16,
“Configuring IEEE 802.1Q and Layer 2 Protocol
Tunneling.”
For more detailed definitions of access and trunk modes and their functions, see Table 12-4 on
page 12-16.
When a port belongs to a VLAN, the switch learns and manages the addresses associated with the port
on a per-VLAN basis. For more information, see the “Managing the MAC Address Table” section on
page 5-12.
Configuring Normal-Range VLANs
Normal-range VLANs are VLANs with VLAN IDs 1 to 1005. If the switch is in VTP server or
VTP transparent mode, you can add, modify or remove configurations for VLANs 2 to 1001 in the
VLAN database. (VLAN IDs 1 and 1002 to 1005 are automatically created and cannot be removed.)
In VTP versions 1 and 2, the switch must be in VTP transparent mode when you create extended-range
VLANs (VLANs with IDs from 1006 to 4094), but these VLANs are not saved in the VLAN database.
VTP version 3 supports extended-range VLANs in VTP server and transparent mode and saves them in
the VLAN database. See the “Configuring Extended-Range VLANs” section on page 12-11.
Configurations for VLAN IDs 1 to 1005 are written to the file vlan.dat (VLAN database), and you can
display them by entering the show vlan privileged EXEC command. The vlan.dat file is stored in flash
memory.
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Configuring VLANs
Configuring Normal-Range VLANs
Caution
You can cause inconsistency in the VLAN database if you attempt to manually delete the vlan.dat file.
If you want to modify the VLAN configuration, use the commands described in these sections and in the
command reference for this release. To change the VTP configuration, see Chapter 13, “Configuring
VTP.”
You use the interface configuration mode to define the port membership mode and to add and remove
ports from VLANs. The results of these commands are written to the running-configuration file, and you
can display the file by entering the show running-config privileged EXEC command.
You can set these parameters when you create a new normal-range VLAN or modify an existing VLAN
in the VLAN database:
Note
•
VLAN ID
•
VLAN name
•
VLAN type (Ethernet, Fiber Distributed Data Interface [FDDI], FDDI network entity title [NET],
TrBRF, or TrCRF, Token Ring, Token Ring-Net)
•
VLAN state (active or suspended)
•
Maximum transmission unit (MTU) for the VLAN
•
Security Association Identifier (SAID)
•
Bridge identification number for TrBRF VLANs
•
Ring number for FDDI and TrCRF VLANs
•
Parent VLAN number for TrCRF VLANs
•
Spanning Tree Protocol (STP) type for TrCRF VLANs
•
VLAN number to use when translating from one VLAN type to another
This section does not provide configuration details for most of these parameters. For complete
information on the commands and parameters that control VLAN configuration, see the command
reference for this release.
These sections contain normal-range VLAN configuration information:
•
Token Ring VLANs, page 12-6
•
Normal-Range VLAN Configuration Guidelines, page 12-6
•
Creating Normal-Range VLANs, page 12-7
•
Default Ethernet VLAN Configuration, page 12-7
•
Creating or Modifying an Ethernet VLAN, page 12-8
•
Deleting a VLAN, page 12-9
•
Assigning Static-Access Ports to a VLAN, page 12-10
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Configuring VLANs
Configuring Normal-Range VLANs
Token Ring VLANs
Although the switch does not support Token Ring connections, a remote device such as a Catalyst 5000
series switch with Token Ring connections could be managed from one of the supported switches.
Switches running VTP version 2 advertise information about these Token Ring VLANs:
•
Token Ring TrBRF VLANs
•
Token Ring TrCRF VLANs
For more information on configuring Token Ring VLANs, see the Catalyst 5000 Series Software
Configuration Guide.
Normal-Range VLAN Configuration Guidelines
Follow these guidelines when creating and modifying normal-range VLANs in your network:
•
The switch supports 1005 VLANs in VTP client, server, and transparent modes.
•
Normal-range VLANs are identified with a number between 1 and 1001. VLAN numbers 1002
through 1005 are reserved for Token Ring and FDDI VLANs.
•
VLAN configuration for VLANs 1 to 1005 are always saved in the VLAN database. If the VTP mode
is transparent, VTP and VLAN configuration are also saved in the switch running configuration file.
•
With VTP versions 1 and 2, the switch supports extended-range VLANs (VLAN IDs 1006 through
4094) only in VTP transparent mode (VTP disabled). Extended-range VLANs created in VTP
transparent mode are not saved in the VLAN database and are not propagated. VTP version 3
supports extended-range VLAN configuration and database propagation. If extended VLANs are
configured, you cannot convert from VTP version 3 to version 1 or 2. See the “Configuring
Extended-Range VLANs” section on page 12-11.
•
Before you can create a VLAN, the switch must be in VTP server mode or VTP transparent mode.
If the switch is a VTP server, you must define a VTP domain or VTP will not function.
•
The switch does not support Token Ring or FDDI media. The switch does not forward FDDI,
FDDI-Net, TrCRF, or TrBRF traffic, but it does propagate the VLAN configuration through VTP.
•
The switch supports 128 spanning-tree instances. If a switch has more active VLANs than supported
spanning-tree instances, spanning tree can be enabled on 128 VLANs and is disabled on the
remaining VLANs. If you have already used all available spanning-tree instances on a switch,
adding another VLAN anywhere in the VTP domain creates a VLAN on that switch that is not
running spanning-tree. If you have the default allowed list on the trunk ports of that switch (which
is to allow all VLANs), the new VLAN is carried on all trunk ports. Depending on the topology of
the network, this could create a loop in the new VLAN that would not be broken, particularly if there
are several adjacent switches that all have run out of spanning-tree instances. You can prevent this
possibility by setting allowed lists on the trunk ports of switches that have used up their allocation
of spanning-tree instances.
If the number of VLANs on the switch exceeds the number of supported spanning-tree instances,
we recommend that you configure the IEEE 802.1s Multiple STP (MSTP) on your switch to map
multiple VLANs to a single spanning-tree instance. For more information about MSTP, see
Chapter 18, “Configuring MSTP.”
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Configuring VLANs
Configuring Normal-Range VLANs
Creating Normal-Range VLANs
You configure normal-range VLANs in VLAN configuration mode by entering the vlan global
configuration command with a VLAN ID. Enter a new VLAN ID to create a VLAN, or enter an existing
VLAN ID to modify that VLAN. You can use the default VLAN configuration (Table 12-2) or enter
multiple commands to configure the VLAN. For more information about commands available in this
mode, see the vlan global configuration command description in the command reference for this release.
When you have finished the configuration, you must exit VLAN configuration mode for the
configuration to take effect. To display the VLAN configuration, enter the show vlan privileged EXEC
command.
The configurations of VLAN IDs 1 to 1005 are always saved in the VLAN database (vlan.dat file). If the
VTP mode is transparent, they are also saved in the switch running configuration file. You can enter the
copy running-config startup-config privileged EXEC command to save the configuration in the startup
configuration file. To display the VLAN configuration, enter the show vlan privileged EXEC command.
When you save VLAN and VTP information (including extended-range VLAN configuration
information) in the startup configuration file and reboot the switch, the switch configuration is selected
as follows:
Caution
•
If the VTP mode is transparent in the startup configuration, and the VLAN database and the VTP
domain name from the VLAN database matches that in the startup configuration file, the VLAN
database is ignored (cleared), and the VTP and VLAN configurations in the startup configuration
file are used. The VLAN database revision number remains unchanged in the VLAN database.
•
If the VTP mode or domain name in the startup configuration does not match the VLAN database,
the domain name and VTP mode and configuration for the first 1005 VLANs use the VLAN
database information.
•
In VTP versions 1 and 2, if VTP mode is server, the domain name and VLAN configuration for only
the first 1005 VLANs use the VLAN database information. VTP version 3 also supports VLANs
1006 to 4094.
If the VLAN database configuration is used at startup and the startup configuration file contains
extended-range VLAN configuration, this information is lost when the system boots up.
Default Ethernet VLAN Configuration
Table 12-2 shows the default configuration for Ethernet VLANs.
Note
The switch supports Ethernet interfaces exclusively. Because FDDI and Token Ring VLANs are not
locally supported, you only configure FDDI and Token Ring media-specific characteristics for VTP
global advertisements to other switches.
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Chapter 12
Configuring VLANs
Configuring Normal-Range VLANs
Table 12-2
Ethernet VLAN Defaults and Ranges
Parameter
Default
Range
VLAN ID
1
1 to 4094.
Note
Extended-range VLANs (VLAN
IDs 1006 to 4094) are only saved in
the VLAN database in VTP
version 3.
VLAN name
No range
VLANxxxx, where xxxx
represents four numeric digits
(including leading zeros) equal
to the VLAN ID number
IEEE 802.10 SAID
100001 (100000 plus the
VLAN ID)
1 to 4294967294
MTU size
1500
1500 to 18190
Translational bridge 1
0
0 to 1005
Translational bridge 2
0
0 to 1005
VLAN state
active
active, suspend
Remote SPAN
disabled
enabled, disabled
Private VLANs
none configured
2 to 1001, 1006 to 4094.
Creating or Modifying an Ethernet VLAN
Each Ethernet VLAN in the VLAN database has a unique, 4-digit ID that can be a number from 1 to
1001. VLAN IDs 1002 to 1005 are reserved for Token Ring and FDDI VLANs. To create a normal-range
VLAN to be added to the VLAN database, assign a number and name to the VLAN.
Note
With VTP version 1 and 2, if the switch is in VTP transparent mode, you can assign VLAN IDs greater
than 1006, but they are not added to the VLAN database. See the “Configuring Extended-Range
VLANs” section on page 12-11.
For the list of default parameters that are assigned when you add a VLAN, see the “Configuring
Normal-Range VLANs” section on page 12-4.
Beginning in privileged EXEC mode, follow these steps to create or modify an Ethernet VLAN:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
vlan vlan-id
Enter a VLAN ID, and enter VLAN configuration mode. Enter a new
VLAN ID to create a VLAN, or enter an existing VLAN ID to modify
that VLAN.
Note
The available VLAN ID range for this command is 1 to 4094.
For information about adding VLAN IDs greater than 1005
(extended-range VLANs), see the “Configuring
Extended-Range VLANs” section on page 12-11.
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Configuring VLANs
Configuring Normal-Range VLANs
Command
Purpose
Step 3
name vlan-name
(Optional) Enter a name for the VLAN. If no name is entered for the
VLAN, the default is to append the vlan-id with leading zeros to the
word VLAN. For example, VLAN0004 is a default VLAN name for
VLAN 4.
Step 4
mtu mtu-size
(Optional) Change the MTU size (or other VLAN characteristic).
Step 5
remote-span
(Optional) Configure the VLAN as the RSPAN VLAN for a remote
SPAN session. For more information on remote SPAN, see Chapter 28,
“Configuring SPAN and RSPAN.”
Step 6
end
Return to privileged EXEC mode.
Step 7
show vlan {name vlan-name | id vlan-id} Verify your entries.
Step 8
copy running-config startup config
(Optional) If the switch is in VTP transparent mode, the VLAN
configuration is saved in the running configuration file as well as in the
VLAN database. This saves the configuration in the switch startup
configuration file.
To return the VLAN name to the default settings, use the no name, no mtu, or no remote-span VLAN
configuration commands.
This example shows how to use VLAN configuration mode to create Ethernet VLAN 20, name it test20,
and add it to the VLAN database:
Switch# configure terminal
Switch(config)# vlan 20
Switch(config-vlan)# name test20
Switch(config-vlan)# end
Deleting a VLAN
When you delete a VLAN from a switch that is in VTP server mode, the VLAN is removed from the
VLAN database for all switches in the VTP domain. When you delete a VLAN from a switch that is in
VTP transparent mode, the VLAN is deleted only on that specific switch.
You cannot delete the default VLANs for the different media types: Ethernet VLAN 1 and FDDI or
Token Ring VLANs 1002 to 1005.
Caution
When you delete a VLAN, any ports assigned to that VLAN become inactive. They remain associated
with the VLAN (and thus inactive) until you assign them to a new VLAN.
Beginning in privileged EXEC mode, follow these steps to delete a VLAN on the switch:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
no vlan vlan-id
Remove the VLAN by entering the VLAN ID.
Step 3
end
Return to privileged EXEC mode.
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Configuring VLANs
Configuring Normal-Range VLANs
Command
Purpose
Step 4
show vlan brief
Verify the VLAN removal.
Step 5
copy running-config startup config
(Optional) If the switch is in VTP transparent mode, the VLAN
configuration is saved in the running configuration file as well as in
the VLAN database. This saves the configuration in the switch startup
configuration file.
Assigning Static-Access Ports to a VLAN
You can assign a static-access port to a VLAN without having VTP globally propagate VLAN
configuration information by disabling VTP (VTP transparent mode).
Note
If you assign an interface to a VLAN that does not exist, the new VLAN is created. (See the “Creating
or Modifying an Ethernet VLAN” section on page 12-8.)
Beginning in privileged EXEC mode, follow these steps to assign a port to a VLAN in the VLAN
database:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode
Step 2
interface interface-id
Enter the interface to be added to the VLAN.
Step 3
switchport mode access
Define the VLAN membership mode for the port (Layer 2 access
port).
Step 4
switchport access vlan vlan-id
Assign the port to a VLAN. Valid VLAN IDs are 1 to 4094.
Step 5
end
Return to privileged EXEC mode.
Step 6
show running-config interface interface-id
Verify the VLAN membership mode of the interface.
Step 7
show interfaces interface-id switchport
Verify your entries in the Administrative Mode and the Access Mode
VLAN fields of the display.
Step 8
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To return an interface to its default configuration, use the default interface interface-id interface
configuration command.
This example shows how to configure a port as an access port in VLAN 2:
Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# interface gigabitethernet0/1
Switch(config-if)# switchport mode access
Switch(config-if)# switchport access vlan 2
Switch(config-if)# end
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Configuring VLANs
Configuring Extended-Range VLANs
Configuring Extended-Range VLANs
With VTP version 1 and version 2, when the switch is in VTP transparent mode (VTP disabled), you can
create extended-range VLANs (in the range 1006 to 4094). VTP version supports extended-range
VLANs in server or transparent move. Extended-range VLANs enable service providers to extend their
infrastructure to a greater number of customers. The extended-range VLAN IDs are allowed for any
switchport commands that allow VLAN IDs.
With VTP version 1 or 2, extended-range VLAN configurations are not stored in the VLAN database,
but because VTP mode is transparent, they are stored in the switch running configuration file, and you
can save the configuration in the startup configuration file by using the copy running-config
startup-config privileged EXEC command. Extended-range VLANs created in VTP version 3 are stored
in the VLAN database.
Note
Although the switch supports 4094 VLAN IDs, see the “Supported VLANs” section on page 12-2 for
the actual number of VLANs supported.
These sections contain extended-range VLAN configuration information:
•
Default VLAN Configuration, page 12-11
•
Extended-Range VLAN Configuration Guidelines, page 12-11
•
Creating an Extended-Range VLAN, page 12-12
•
Creating an Extended-Range VLAN with an Internal VLAN ID, page 12-13
Default VLAN Configuration
See Table 12-2 on page 12-8 for the default configuration for Ethernet VLANs. You can change only the
MTU size, private VLAN, and the remote SPAN configuration state on extended-range VLANs; all other
characteristics must remain at the default state.
Extended-Range VLAN Configuration Guidelines
Follow these guidelines when creating extended-range VLANs:
•
VLAN IDs in the extended range are not saved in the VLAN database and are not recognized by
VTP unless the switch is running VTP version 3.
•
You cannot include extended-range VLANs in the pruning eligible range.
•
In VTP version 1 and 2, a switch must be in VTP transparent mode when you create extended-range
VLANs. If VTP mode is server or client, an error message is generated, and the extended-range
VLAN is rejected. VTP version 3 supports extended VLANs in server and transparent modes.
•
For VTP version 1 or 2, you can set the VTP mode to transparent in global configuration mode. See
the “Configuring VTP Mode” section on page 13-10. You should save this configuration to the
startup configuration so that the switch boots up in VTP transparent mode. Otherwise, you lose the
extended-range VLAN configuration if the switch resets. If you create extended-range VLANs in
VTP version 3, you cannot convert to VTP version 1 or 2.
•
STP is enabled by default on extended-range VLANs, but you can disable it by using the no
spanning-tree vlan vlan-id global configuration command. When the maximum number of
spanning-tree instances are on the switch, spanning tree is disabled on any newly created VLANs.
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Configuring VLANs
Configuring Extended-Range VLANs
If the number of VLANs on the switch exceeds the maximum number of spanning-tree instances,
we recommend that you configure the IEEE 802.1s Multiple STP (MSTP) on your switch to map
multiple VLANs to a single spanning-tree instance. For more information about MSTP, see
Chapter 18, “Configuring MSTP.”
•
Each routed port on the switch creates an internal VLAN for its use. These internal VLANs use
extended-range VLAN numbers, and the internal VLAN ID cannot be used for an extended-range
VLAN. If you try to create an extended-range VLAN with a VLAN ID that is already allocated as
an internal VLAN, an error message is generated, and the command is rejected.
– Because internal VLAN IDs are in the lower part of the extended range, we recommend that you
create extended-range VLANs beginning from the highest number (4094) and moving to the
lowest (1006) to reduce the possibility of using an internal VLAN ID.
– Before configuring extended-range VLANs, enter the show vlan internal usage privileged
EXEC command to see which VLANs have been allocated as internal VLANs.
– If necessary, you can shut down the routed port assigned to the internal VLAN, which frees up
the internal VLAN, and then create the extended-range VLAN and re-enable the port, which
then uses another VLAN as its internal VLAN. See the “Creating an Extended-Range VLAN
with an Internal VLAN ID” section on page 12-13.
•
Although the switch supports a total of 1005 (normal-range and extended-range) VLANs, the
number of routed ports, SVIs, and other configured features affects the use of the switch hardware.
If you try to create an extended-range VLAN and there are not enough hardware resources available,
an error message is generated, and the extended-range VLAN is rejected.
Creating an Extended-Range VLAN
You create an extended-range VLAN in global configuration mode by entering the vlan global
configuration command with a VLAN ID from 1006 to 4094. This command accesses VLAN
configuration mode. The extended-range VLAN has the default Ethernet VLAN characteristics (see
Table 12-2) and the MTU size, private VLAN, and RSPAN configuration are the only parameters you
can change. See the description of the vlan global configuration command in the command reference for
the default settings of all parameters. In VTP version 1 or 2, if you enter an extended-range VLAN ID
when the switch is not in VTP transparent mode, an error message is generated when you exit VLAN
configuration mode, and the extended-range VLAN is not created.
In VTP version 1 and 2, extended-range VLANs are not saved in the VLAN database; they are saved in
the switch running configuration file. You can save the extended-range VLAN configuration in the
switch startup configuration file by using the copy running-config startup-config privileged EXEC
command. VTP version 3 saves extended-range VLANs in the VLAN database.
Note
Before you create an extended-range VLAN, you can verify that the VLAN ID is not used internally by
entering the show vlan internal usage privileged EXEC command. If the VLAN ID is used internally
and you want to free it up, go to the“Creating an Extended-Range VLAN with an Internal VLAN ID”
section on page 12-13 before creating the extended-range VLAN.
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Configuring VLANs
Configuring Extended-Range VLANs
Beginning in privileged EXEC mode, follow these steps to create an extended-range VLAN:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
vtp mode transparent
Configure the switch for VTP transparent mode, disabling VTP.
Note
This step is not required for VTP version 3.
Step 3
vlan vlan-id
Enter an extended-range VLAN ID and enter VLAN configuration mode.
The range is 1006 to 4094.
Step 4
mtu mtu-size
(Optional) Modify the VLAN by changing the MTU size.
Note
Although all VLAN commands appear in the CLI help in VLAN
configuration mode, only the mtu mtu-size, private-vlan, and
remote-span commands are supported for extended-range
VLANs.
Step 5
remote-span
(Optional) Configure the VLAN as the RSPAN VLAN. See the
“Configuring a VLAN as an RSPAN VLAN” section on page 28-16.
Step 6
end
Return to privileged EXEC mode.
Step 7
show vlan id vlan-id
Verify that the VLAN has been created.
Step 8
copy running-config startup config
Save your entries in the switch startup configuration file. To save
extended-range VLAN configurations, you need to save the VTP
transparent mode configuration and the extended-range VLAN
configuration in the switch startup configuration file. Otherwise, if the
switch resets, it will default to VTP server mode, and the extended-range
VLAN IDs will not be saved.
Note
With VTP version 3, the VLAN configuration is also saved in the
VLAN database.
To delete an extended-range VLAN, use the no vlan vlan-id global configuration command.
The procedure for assigning static-access ports to an extended-range VLAN is the same as for
normal-range VLANs. See the “Assigning Static-Access Ports to a VLAN” section on page 12-10.
This example shows how to create a new extended-range VLAN with all default characteristics, enter
VLAN configuration mode, and save the new VLAN in the switch startup configuration file:
Switch(config)# vtp mode transparent
Switch(config)# vlan 2000
Switch(config-vlan)# end
Switch# copy running-config startup config
Creating an Extended-Range VLAN with an Internal VLAN ID
If you enter an extended-range VLAN ID that is already assigned to an internal VLAN, an error message
is generated, and the extended-range VLAN is rejected. To manually free an internal VLAN ID, you
must temporarily shut down the routed port that is using the internal VLAN ID.
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Configuring VLANs
Displaying VLANs
Beginning in privileged EXEC mode, follow these steps to release a VLAN ID that is assigned to an
internal VLAN and to create an extended-range VLAN with that ID:
Command
Purpose
Step 1
show vlan internal usage
Display the VLAN IDs being used internally by the switch. If the VLAN
ID that you want to use is an internal VLAN, the display shows the routed
port that is using the VLAN ID. Enter that port number in Step 3.
Step 2
configure terminal
Enter global configuration mode.
Step 3
interface interface-id
Specify the interface ID for the routed port that is using the VLAN ID,
and enter interface configuration mode.
Step 4
shutdown
Shut down the port to free the internal VLAN ID.
Step 5
exit
Return to global configuration mode.
Step 6
vtp mode transparent
Set the VTP mode to transparent for creating extended-range VLANs.
Note
This step is not required for VTP version 3.
Step 7
vlan vlan-id
Enter the new extended-range VLAN ID, and enter VLAN configuration
mode.
Step 8
exit
Exit from VLAN configuration mode, and return to global configuration
mode.
Step 9
interface interface-id
Specify the interface ID for the routed port that you shut down in Step 4,
and enter interface configuration mode.
Step 10
no shutdown
Re-enable the routed port. It will be assigned a new internal VLAN ID.
Step 11
end
Return to privileged EXEC mode.
Step 12
copy running-config startup config
Save your entries in the switch startup configuration file. To save an
extended-range VLAN configuration, you need to save the VTP
transparent mode configuration and the extended-range VLAN
configuration in the switch startup configuration file. Otherwise, if the
switch resets, it will default to VTP server mode, and the extended-range
VLAN IDs will not be saved.
Note
This step is not required for VTP version 3 because VLANs are
saved in the VLAN database.
Displaying VLANs
Use the show vlan privileged EXEC command to display a list of all VLANs on the switch, including
extended-range VLANs. The display includes VLAN status, ports, and configuration information.
Table 12-3 lists the commands for monitoring VLANs.
Table 12-3
VLAN Monitoring Commands
Command
Purpose
show interfaces [vlan
vlan-id]
Display characteristics for all interfaces or for the specified VLAN
configured on the switch.
show vlan [id vlan-id]
Display parameters for all VLANs or the specified VLAN on the
switch.
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Configuring VLANs
Configuring VLAN Trunks
For more details about the show command options and explanations of output fields, see the command
reference for this release.
Configuring VLAN Trunks
These sections contain this conceptual information:
•
Trunking Overview, page 12-15
•
Encapsulation Types, page 12-17
•
Default Layer 2 Ethernet Interface VLAN Configuration, page 12-18
•
Configuring an Ethernet Interface as a Trunk Port, page 12-18
•
Configuring Trunk Ports for Load Sharing, page 12-22
Trunking Overview
A trunk is a point-to-point link between one or more Ethernet switch interfaces and another networking device
such as a router or a switch. Ethernet trunks carry the traffic of multiple VLANs over a single link, and you
can extend the VLANs across an entire network.
Two trunking encapsulations are available on all Ethernet interfaces:
•
Inter-Switch Link (ISL)—Cisco-proprietary trunking encapsulation.
•
IEEE 802.1Q— industry-standard trunking encapsulation.
Figure 12-2 shows a network of blade switches that are connected by ISL trunks.
Figure 12-2
Blade Switches in an ISL Trunking Environment
Catalyst 6500 series
switch
ISL
trunk
ISL
trunk
ISL
trunk
ISL
trunk
Blade
switch
Blade
switch
VLAN1
Blade
switch
VLAN3
VLAN2
VLAN2
VLAN1
VLAN3
119945
Blade
switch
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Configuring VLANs
Configuring VLAN Trunks
You can configure a trunk on a single Ethernet interface or on an EtherChannel bundle. For more
information about EtherChannel, see Chapter 35, “Configuring EtherChannels and Layer 2 Trunk
Failover.”
Ethernet trunk interfaces support different trunking modes (see Table 12-4). You can set an interface as
trunking or nontrunking or to negotiate trunking with the neighboring interface. To autonegotiate
trunking, the interfaces must be in the same VTP domain.
Trunk negotiation is managed by the Dynamic Trunking Protocol (DTP), which is a Point-to-Point
Protocol. However, some internetworking devices might forward DTP frames improperly, which could
cause misconfigurations.
To avoid this, you should configure interfaces connected to devices that do not support DTP to not
forward DTP frames, that is, to turn off DTP.
•
If you do not intend to trunk across those links, use the switchport mode access interface
configuration command to disable trunking.
•
To enable trunking to a device that does not support DTP, use the switchport mode trunk and
switchport nonegotiate interface configuration commands to cause the interface to become a trunk
but to not generate DTP frames. Use the switchport trunk encapsulation isl or switchport trunk
encapsulation dot1q interface to select the encapsulation type on the trunk port.
You can also specify on DTP interfaces whether the trunk uses ISL or IEEE 802.1Q encapsulation or if
the encapsulation type is autonegotiated. The DTP supports autonegotiation of both ISL and
IEEE 802.1Q trunks.
Note
Table 12-4
DTP is not supported on private-VLAN ports or tunnel ports.
Layer 2 Interface Modes
Mode
Function
switchport mode access
Puts the interface (access port) into permanent nontrunking mode and negotiates to
convert the link into a nontrunk link. The interface becomes a nontrunk interface
regardless of whether or not the neighboring interface is a trunk interface.
switchport mode dynamic auto
Makes the interface able to convert the link to a trunk link. The interface becomes a trunk
interface if the neighboring interface is set to trunk or desirable mode. The default
switchport mode for all Ethernet interfaces is dynamic auto.
switchport mode dynamic
desirable
Makes the interface actively attempt to convert the link to a trunk link. The interface
becomes a trunk interface if the neighboring interface is set to trunk, desirable, or auto
mode.
switchport mode trunk
Puts the interface into permanent trunking mode and negotiates to convert the
neighboring link into a trunk link. The interface becomes a trunk interface even if the
neighboring interface is not a trunk interface.
switchport nonegotiate
Prevents the interface from generating DTP frames. You can use this command only when
the interface switchport mode is access or trunk. You must manually configure the
neighboring interface as a trunk interface to establish a trunk link.
switchport mode dot1q-tunnel
Configures the interface as a tunnel (nontrunking) port to be connected in an asymmetric
link with an IEEE 802.1Q trunk port. The IEEE 802.1Q tunneling is used to maintain
customer VLAN integrity across a service provider network. See Chapter 16,
“Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling,” for more information on
tunnel ports.
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Configuring VLANs
Configuring VLAN Trunks
Encapsulation Types
Table 12-5 lists the Ethernet trunk encapsulation types and keywords.
Table 12-5
Ethernet Trunk Encapsulation Types
Encapsulation
Function
switchport trunk encapsulation isl
Specifies ISL encapsulation on the trunk link.
switchport trunk encapsulation dot1q
Specifies IEEE 802.1Q encapsulation on the trunk link.
switchport trunk encapsulation negotiate Specifies that the interface negotiate with the neighboring interface to become
an ISL (preferred) or IEEE 802.1Q trunk, depending on the configuration and
capabilities of the neighboring interface. This is the default for the switch.
Note
The switch does not support Layer 3 trunks; you cannot configure subinterfaces or use the encapsulation
keyword on Layer 3 interfaces. The switch does support Layer 2 trunks and Layer 3 VLAN interfaces,
which provide equivalent capabilities.
The trunking mode, the trunk encapsulation type, and the hardware capabilities of the two connected
interfaces decide whether a link becomes an ISL or IEEE 802.1Q trunk.
IEEE 802.1Q Configuration Considerations
The IEEE 802.1Q trunks impose these limitations on the trunking strategy for a network:
•
In a network of Cisco switches connected through IEEE 802.1Q trunks, the switches maintain one
spanning-tree instance for each VLAN allowed on the trunks. Non-Cisco devices might support one
spanning-tree instance for all VLANs.
When you connect a Cisco switch to a non-Cisco device through an IEEE 802.1Q trunk, the Cisco
switch combines the spanning-tree instance of the VLAN of the trunk with the spanning-tree
instance of the non-Cisco IEEE 802.1Q switch. However, spanning-tree information for each VLAN
is maintained by Cisco switches separated by a cloud of non-Cisco IEEE 802.1Q switches. The
non-Cisco IEEE 802.1Q cloud separating the Cisco switches is treated as a single trunk link between
the switches.
•
Make sure the native VLAN for an IEEE 802.1Q trunk is the same on both ends of the trunk link. If
the native VLAN on one end of the trunk is different from the native VLAN on the other end,
spanning-tree loops might result.
•
Disabling spanning tree on the native VLAN of an IEEE 802.1Q trunk without disabling spanning
tree on every VLAN in the network can potentially cause spanning-tree loops. We recommend that
you leave spanning tree enabled on the native VLAN of an IEEE 802.1Q trunk or disable spanning
tree on every VLAN in the network. Make sure your network is loop-free before disabling spanning
tree.
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Configuring VLANs
Configuring VLAN Trunks
Default Layer 2 Ethernet Interface VLAN Configuration
Table 12-6 shows the default Layer 2 Ethernet interface VLAN configuration.
Table 12-6
Default Layer 2 Ethernet Interface VLAN Configuration
Feature
Default Setting
Interface mode
switchport mode dynamic auto
Trunk encapsulation
switchport trunk encapsulation negotiate
Allowed VLAN range
VLANs 1 to 4094
VLAN range eligible for pruning
VLANs 2 to 1001
Default VLAN (for access ports)
VLAN 1
Native VLAN (for IEEE 802.1Q trunks) VLAN 1
Configuring an Ethernet Interface as a Trunk Port
Because trunk ports send and receive VTP advertisements, to use VTP you must ensure that at least one
trunk port is configured on the switch and that this trunk port is connected to the trunk port of a second
switch. Otherwise, the switch cannot receive any VTP advertisements.
These sections contain this configuration information:
Note
•
Interaction with Other Features, page 12-18
•
Defining the Allowed VLANs on a Trunk, page 12-20
•
Changing the Pruning-Eligible List, page 12-21
•
Configuring the Native VLAN for Untagged Traffic, page 12-22
By default, an interface is in Layer 2 mode. The default mode for Layer 2 interfaces is switchport mode
dynamic auto. If the neighboring interface supports trunking and is configured to allow trunking, the
link is a Layer 2 trunk or, if the interface is in Layer 3 mode, it becomes a Layer 2 trunk when you enter
the switchport interface configuration command. By default, trunks negotiate encapsulation. If the
neighboring interface supports ISL and IEEE 802.1Q encapsulation and both interfaces are set to
negotiate the encapsulation type, the trunk uses ISL encapsulation.
Interaction with Other Features
Trunking interacts with other features in these ways:
•
A trunk port cannot be a secure port.
•
A trunk port cannot be a tunnel port.
•
Trunk ports can be grouped into EtherChannel port groups, but all trunks in the group must have the
same configuration. When a group is first created, all ports follow the parameters set for the first
port to be added to the group. If you change the configuration of one of these parameters, the switch
propagates the setting you entered to all ports in the group:
– allowed-VLAN list.
– STP port priority for each VLAN.
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Configuring VLAN Trunks
– STP Port Fast setting.
– trunk status: if one port in a port group ceases to be a trunk, all ports cease to be trunks.
•
We recommend that you configure no more than 24 trunk ports in PVST mode and no more than 40
trunk ports in MST mode.
•
If you try to enable IEEE 802.1x on a trunk port, an error message appears, and IEEE 802.1x is not
enabled. If you try to change the mode of an IEEE 802.1x-enabled port to trunk, the port mode is
not changed.
•
A port in dynamic mode can negotiate with its neighbor to become a trunk port. If you try to enable
IEEE 802.1x on a dynamic port, an error message appears, and IEEE 802.1x is not enabled. If you
try to change the mode of an IEEE 802.1x-enabled port to dynamic, the port mode is not changed.
Configuring a Trunk Port
Beginning in privileged EXEC mode, follow these steps to configure a port as a trunk port:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify the port to be configured for trunking, and enter interface
configuration mode.
Step 3
switchport trunk encapsulation {isl |
dot1q | negotiate}
Configure the port to support ISL or IEEE 802.1Q encapsulation or to
negotiate (the default) with the neighboring interface for encapsulation
type.
You must configure each end of the link with the same encapsulation type.
Step 4
switchport mode {dynamic {auto |
desirable} | trunk}
Configure the interface as a Layer 2 trunk (required only if the interface
is a Layer 2 access port or tunnel port or to specify the trunking mode).
•
dynamic auto—Set the interface to a trunk link if the neighboring
interface is set to trunk or desirable mode. This is the default.
•
dynamic desirable—Set the interface to a trunk link if the
neighboring interface is set to trunk, desirable, or auto mode.
•
trunk—Set the interface in permanent trunking mode and negotiate
to convert the link to a trunk link even if the neighboring interface is
not a trunk interface.
Step 5
switchport access vlan vlan-id
(Optional) Specify the default VLAN, which is used if the interface stops
trunking.
Step 6
switchport trunk native vlan vlan-id
Specify the native VLAN for IEEE 802.1Q trunks.
Step 7
end
Return to privileged EXEC mode.
Step 8
show interfaces interface-id switchport Display the switchport configuration of the interface in the Administrative
Mode and the Administrative Trunking Encapsulation fields of the
display.
Step 9
show interfaces interface-id trunk
Display the trunk configuration of the interface.
Step 10
copy running-config startup-config
(Optional) Save your entries in the configuration file.
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Configuring VLANs
Configuring VLAN Trunks
To return an interface to its default configuration, use the default interface interface-id interface
configuration command. To reset all trunking characteristics of a trunking interface to the defaults, use
the no switchport trunk interface configuration command. To disable trunking, use the switchport
mode access interface configuration command to configure the port as a static-access port.
This example shows how to configure a port as an IEEE 802.1Q trunk. The example assumes that the
neighbor interface is configured to support IEEE 802.1Q trunking.
Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# interface gigabitethernet0/2
Switch(config-if)# switchport mode dynamic desirable
Switch(config-if)# switchport trunk encapsulation dot1q
Switch(config-if)# end
Defining the Allowed VLANs on a Trunk
By default, a trunk port sends traffic to and receives traffic from all VLANs. All VLAN IDs, 1 to 4094,
are allowed on each trunk. However, you can remove VLANs from the allowed list, preventing traffic
from those VLANs from passing over the trunk. To restrict the traffic a trunk carries, use the switchport
trunk allowed vlan remove vlan-list interface configuration command to remove specific VLANs from
the allowed list.
Note
VLAN 1 is the default VLAN on all trunk ports in all Cisco switches, and it has previously been a
requirement that VLAN 1 always be enabled on every trunk link. You can use the VLAN 1 minimization
feature to disable VLAN 1 on any individual VLAN trunk link so that no user traffic (including
spanning-tree advertisements) is sent or received on VLAN 1.
To reduce the risk of spanning-tree loops or storms, you can disable VLAN 1 on any individual VLAN
trunk port by removing VLAN 1 from the allowed list. When you remove VLAN 1 from a trunk port,
the interface continues to sent and receive management traffic, for example, Cisco Discovery Protocol
(CDP), Port Aggregation Protocol (PAgP), Link Aggregation Control Protocol (LACP), DTP, and VTP
in VLAN 1.
If a trunk port with VLAN 1 disabled is converted to a nontrunk port, it is added to the access VLAN. If
the access VLAN is set to 1, the port will be added to VLAN 1, regardless of the switchport trunk
allowed setting. The same is true for any VLAN that has been disabled on the port.
A trunk port can become a member of a VLAN if the VLAN is enabled, if VTP knows of the VLAN,
and if the VLAN is in the allowed list for the port. When VTP detects a newly enabled VLAN and the
VLAN is in the allowed list for a trunk port, the trunk port automatically becomes a member of the
enabled VLAN. When VTP detects a new VLAN and the VLAN is not in the allowed list for a trunk
port, the trunk port does not become a member of the new VLAN.
Beginning in privileged EXEC mode, follow these steps to modify the allowed list of a trunk:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify the port to be configured, and enter interface configuration
mode.
Step 3
switchport mode trunk
Configure the interface as a VLAN trunk port.
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Configuring VLANs
Configuring VLAN Trunks
Step 4
Command
Purpose
switchport trunk allowed vlan {add |
all | except | remove} vlan-list
(Optional) Configure the list of VLANs allowed on the trunk.
For explanations about using the add, all, except, and remove keywords,
see the command reference for this release.
The vlan-list parameter is either a single VLAN number from 1 to 4094
or a range of VLANs described by two VLAN numbers, the lower one
first, separated by a hyphen. Do not enter any spaces between
comma-separated VLAN parameters or in hyphen-specified ranges.
All VLANs are allowed by default.
Step 5
end
Step 6
show interfaces interface-id switchport Verify your entries in the Trunking VLANs Enabled field of the display.
Step 7
copy running-config startup-config
Return to privileged EXEC mode.
(Optional) Save your entries in the configuration file.
To return to the default allowed VLAN list of all VLANs, use the no switchport trunk allowed vlan
interface configuration command.
This example shows how to remove VLAN 2 from the allowed VLAN list on a port:
Switch(config)# interface gigabitethernett0/1
Switch(config-if)# switchport trunk allowed vlan remove 2
Switch(config-if)# end
Changing the Pruning-Eligible List
The pruning-eligible list applies only to trunk ports. Each trunk port has its own eligibility list. VTP
pruning must be enabled for this procedure to take effect. The “Enabling VTP Pruning” section on
page 13-14 describes how to enable VTP pruning.
Beginning in privileged EXEC mode, follow these steps to remove VLANs from the pruning-eligible list
on a trunk port:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Select the trunk port for which VLANs should be pruned, and enter
interface configuration mode.
Step 3
switchport trunk pruning vlan {add |
except | none | remove} vlan-list
[,vlan[,vlan[,,,]]
Configure the list of VLANs allowed to be pruned from the trunk. (See
the “VTP Pruning” section on page 13-5).
For explanations about using the add, except, none, and remove
keywords, see the command reference for this release.
Separate nonconsecutive VLAN IDs with a comma and no spaces; use a
hyphen to designate a range of IDs. Valid IDs are 2 to 1001.
Extended-range VLANs (VLAN IDs 1006 to 4094) cannot be pruned.
VLANs that are pruning-ineligible receive flooded traffic.
The default list of VLANs allowed to be pruned contains VLANs 2 to
1001.
Step 4
end
Return to privileged EXEC mode.
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Configuring VLANs
Configuring VLAN Trunks
Command
Purpose
Step 5
show interfaces interface-id switchport Verify your entries in the Pruning VLANs Enabled field of the display.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To return to the default pruning-eligible list of all VLANs, use the no switchport trunk pruning vlan
interface configuration command.
Configuring the Native VLAN for Untagged Traffic
A trunk port configured with IEEE 802.1Q tagging can receive both tagged and untagged traffic. By
default, the switch forwards untagged traffic in the native VLAN configured for the port. The native
VLAN is VLAN 1 by default.
Note
The native VLAN can be assigned any VLAN ID.
For information about IEEE 802.1Q configuration issues, see the “IEEE 802.1Q Configuration
Considerations” section on page 12-17.
Beginning in privileged EXEC mode, follow these steps to configure the native VLAN on an
IEEE 802.1Q trunk:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Define the interface that is configured as the IEEE 802.1Q trunk, and
enter interface configuration mode.
Step 3
switchport trunk native vlan vlan-id
Configure the VLAN that is sending and receiving untagged traffic
on the trunk port.
For vlan-id, the range is 1 to 4094.
Step 4
end
Return to privileged EXEC mode.
Step 5
show interfaces interface-id switchport
Verify your entries in the Trunking Native Mode VLAN field.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To return to the default native VLAN, VLAN 1, use the no switchport trunk native vlan interface
configuration command.
If a packet has a VLAN ID that is the same as the outgoing port native VLAN ID, the packet is sent
untagged; otherwise, the switch sends the packet with a tag.
Configuring Trunk Ports for Load Sharing
Load sharing divides the bandwidth supplied by parallel trunks connecting switches. To avoid loops,
STP normally blocks all but one parallel link between switches. Using load sharing, you divide the traffic
between the links according to which VLAN the traffic belongs.
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Configuring VLANs
Configuring VLAN Trunks
You configure load sharing on trunk ports by using STP port priorities or STP path costs. For load
sharing using STP port priorities, both load-sharing links must be connected to the same switch. For load
sharing using STP path costs, each load-sharing link can be connected to the same switch or to two
different switches. For more information about STP, see Chapter 17, “Configuring STP.”
Load Sharing Using STP Port Priorities
When two ports on the same switch form a loop, the switch uses the STP port priority to decide which
port is enabled and which port is in a blocking state. You can set the priorities on a parallel trunk port so
that the port carries all the traffic for a given VLAN. The trunk port with the higher priority (lower
values) for a VLAN is forwarding traffic for that VLAN. The trunk port with the lower priority (higher
values) for the same VLAN remains in a blocking state for that VLAN. One trunk port sends or receives
all traffic for the VLAN.
Figure 12-3 shows two trunks connecting supported switches. In this example, the switches are
configured as follows:
•
VLANs 8 through 10 are assigned a port priority of 16 on Trunk 1.
•
VLANs 3 through 6 retain the default port priority of 128 on Trunk 1.
•
VLANs 3 through 6 are assigned a port priority of 16 on Trunk 2.
•
VLANs 8 through 10 retain the default port priority of 128 on Trunk 2.
In this way, Trunk 1 carries traffic for VLANs 8 through 10, and Trunk 2 carries traffic for VLANs 3
through 6. If the active trunk fails, the trunk with the lower priority takes over and carries the traffic for
all of the VLANs. No duplication of traffic occurs over any trunk port.
Figure 12-3
Load Sharing by Using STP Port Priorities
Switch A
Switch B
93370
Trunk 2
VLANs 3 – 6 (priority 16)
VLANs 8 – 10 (priority 128)
Trunk 1
VLANs 8 – 10 (priority 16)
VLANs 3 – 6 (priority 128)
Beginning in privileged EXEC mode, follow these steps to configure the network shown in Figure 12-3.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode on Switch A.
Step 2
vtp domain domain-name
Configure a VTP administrative domain.
The domain name can be 1 to 32 characters.
Step 3
vtp mode server
Configure Switch A as the VTP server.
Step 4
end
Return to privileged EXEC mode.
Step 5
show vtp status
Verify the VTP configuration on both Switch A and Switch B.
In the display, check the VTP Operating Mode and the VTP Domain
Name fields.
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Configuring VLANs
Configuring VLAN Trunks
Command
Purpose
Step 6
show vlan
Verify that the VLANs exist in the database on Switch A.
Step 7
configure terminal
Enter global configuration mode.
Step 8
interface gigabitethernet0/1
Define the interface to be configured as a trunk, and enter interface
configuration mode.
Step 9
switchport trunk encapsulation {isl |
dot1q | negotiate}
Configure the port to support ISL or IEEE 802.1Q encapsulation or to
negotiate with the neighboring interface. You must configure each end
of the link with the same encapsulation type.
Step 10
switchport mode trunk
Configure the port as a trunk port.
Step 11
end
Return to privileged EXEC mode.
Step 12
show interfaces gigabitethernet0/1
switchport
Verify the VLAN configuration.
Step 13
Repeat Steps 7 through 11 on Switch A for a second port in the switch.
Step 14
Repeat Steps 7 through 11 on Switch B to configure the trunk ports
that connect to the trunk ports configured on Switch A.
Step 15
show vlan
When the trunk links come up, VTP passes the VTP and VLAN
information to Switch B. Verify that Switch B has learned the VLAN
configuration.
Step 16
configure terminal
Enter global configuration mode on Switch A.
Step 17
interface gigabitethernet 0/1
Define the interface to set the STP port priority, and enter interface
configuration mode.
Step 18
spanning-tree vlan 8-10 port-priority 16
Assign the port priority of 16 for VLANs 8 through 10.
Step 19
exit
Return to global configuration mode.
Step 20
interface gigabitethernet0/2
Define the interface to set the STP port priority, and enter interface
configuration mode.
Step 21
spanning-tree vlan 3-6 port-priority 16
Assign the port priority of 16 for VLANs 3 through 6.
Step 22
end
Return to privileged EXEC mode.
Step 23
show running-config
Verify your entries.
Step 24
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Load Sharing Using STP Path Cost
You can configure parallel trunks to share VLAN traffic by setting different path costs on a trunk and
associating the path costs with different sets of VLANs, blocking different ports for different VLANs.
The VLANs keep the traffic separate and maintain redundancy in the event of a lost link.
In Figure 12-4, Trunk ports 1 and 2 are configured as 100BASE-T ports. These VLAN path costs are
assigned:
•
VLANs 2 through 4 are assigned a path cost of 30 on Trunk port 1.
•
VLANs 8 through 10 retain the default 100BASE-T path cost on Trunk port 1 of 19.
•
VLANs 8 through 10 are assigned a path cost of 30 on Trunk port 2.
•
VLANs 2 through 4 retain the default 100BASE-T path cost on Trunk port 2 of 19.
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Configuring VLANs
Configuring VLAN Trunks
Figure 12-4
Load-Sharing Trunks with Traffic Distributed by Path Cost
Switch A
Trunk port 2
VLANs 8 – 10 (path cost 30)
VLANs 2 – 4 (path cost 19)
90573
Trunk port 1
VLANs 2 – 4 (path cost 30)
VLANs 8 – 10 (path cost 19)
Switch B
Beginning in privileged EXEC mode, follow these steps to configure the network shown in Figure 12-4:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode on Switch A.
Step 2
interface gigabitethernet0/1
Define the interface to be configured as a trunk, and enter interface
configuration mode.
Step 3
switchport trunk encapsulation
{isl | dot1q | negotiate}
Configure the port to support ISL or IEEE 802.1Q encapsulation. You
must configure each end of the link with the same encapsulation type.
Step 4
switchport mode trunk
Configure the port as a trunk port. The trunk defaults to ISL trunking.
Step 5
exit
Return to global configuration mode.
Step 6
Repeat Steps 2 through 5 on a second interface in Switch A.
Step 7
end
Return to privileged EXEC mode.
Step 8
show running-config
Verify your entries. In the display, make sure that the interfaces are
configured as trunk ports.
Step 9
show vlan
When the trunk links come up, Switch A receives the VTP information
from the other switches. Verify that Switch A has learned the VLAN
configuration.
Step 10
configure terminal
Enter global configuration mode.
Step 11
interface gigabitethernet0/1
Define the interface on which to set the STP cost, and enter interface
configuration mode.
Step 12
spanning-tree vlan 2-4 cost 30
Set the spanning-tree path cost to 30 for VLANs 2 through 4.
Step 13
end
Return to global configuration mode.
Step 14
Repeat Steps 9 through 13 on the other configured trunk interface on
Switch A, and set the spanning-tree path cost to 30 for VLANs 8, 9, and
10.
Step 15
exit
Return to privileged EXEC mode.
Step 16
show running-config
Verify your entries. In the display, verify that the path costs are set
correctly for both trunk interfaces.
Step 17
copy running-config startup-config
(Optional) Save your entries in the configuration file.
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Configuring VLANs
Configuring VMPS
Configuring VMPS
The VLAN Query Protocol (VQP) is used to support dynamic-access ports, which are not permanently
assigned to a VLAN, but give VLAN assignments based on the MAC source addresses seen on the port.
Each time an unknown MAC address is seen, the switch sends a VQP query to a remote VMPS; the query
includes the newly seen MAC address and the port on which it was seen. The VMPS responds with a
VLAN assignment for the port. The switch cannot be a VMPS server but can act as a client to the VMPS
and communicate with it through VQP.
These sections contain this information:
•
“Understanding VMPS” section on page 12-26
•
“Default VMPS Client Configuration” section on page 12-27
•
“VMPS Configuration Guidelines” section on page 12-27
•
“Configuring the VMPS Client” section on page 12-28
•
“Monitoring the VMPS” section on page 12-30
•
“Troubleshooting Dynamic-Access Port VLAN Membership” section on page 12-31
•
“VMPS Configuration Example” section on page 12-31
Understanding VMPS
Each time the client switch receives the MAC address of a new host, it sends a VQP query to the VMPS.
When the VMPS receives this query, it searches its database for a MAC-address-to-VLAN mapping. The
server response is based on this mapping and whether or not the server is in open or secure mode. In
secure mode, the server shuts down the port when an illegal host is detected. In open mode, the server
simply denies the host access to the port.
If the port is currently unassigned (that is, it does not yet have a VLAN assignment), the VMPS provides
one of these responses:
•
If the host is allowed on the port, the VMPS sends the client a vlan-assignment response containing
the assigned VLAN name and allowing access to the host.
•
If the host is not allowed on the port and the VMPS is in open mode, the VMPS sends an
access-denied response.
•
If the VLAN is not allowed on the port and the VMPS is in secure mode, the VMPS sends a
port-shutdown response.
If the port already has a VLAN assignment, the VMPS provides one of these responses:
•
If the VLAN in the database matches the current VLAN on the port, the VMPS sends an success
response, allowing access to the host.
•
If the VLAN in the database does not match the current VLAN on the port and active hosts exist on
the port, the VMPS sends an access-denied or a port-shutdown response, depending on the secure
mode of the VMPS.
If the switch receives an access-denied response from the VMPS, it continues to block traffic to and from
the host MAC address. The switch continues to monitor the packets directed to the port and sends a query
to the VMPS when it identifies a new host address. If the switch receives a port-shutdown response from
the VMPS, it disables the port. The port must be manually re-enabled by using the CLI or SNMP.
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Configuring VLANs
Configuring VMPS
Dynamic-Access Port VLAN Membership
A dynamic-access port can belong to only one VLAN with an ID from 1 to 4094. When the link comes
up, the switch does not forward traffic to or from this port until the VMPS provides the VLAN
assignment. The VMPS receives the source MAC address from the first packet of a new host connected
to the dynamic-access port and attempts to match the MAC address to a VLAN in the VMPS database.
If there is a match, the VMPS sends the VLAN number for that port. If the client switch was not
previously configured, it uses the domain name from the first VTP packet it receives on its trunk port
from the VMPS. If the client switch was previously configured, it includes its domain name in the query
packet to the VMPS to obtain its VLAN number. The VMPS verifies that the domain name in the packet
matches its own domain name before accepting the request and responds to the client with the assigned
VLAN number for the client. If there is no match, the VMPS either denies the request or shuts down the
port (depending on the VMPS secure mode setting).
Multiple hosts (MAC addresses) can be active on a dynamic-access port if they are all in the same
VLAN; however, the VMPS shuts down a dynamic-access port if more than 20 hosts are active on the
port.
If the link goes down on a dynamic-access port, the port returns to an isolated state and does not belong
to a VLAN. Any hosts that come online through the port are checked again through the VQP with the
VMPS before the port is assigned to a VLAN.
Dynamic-access ports can be used for direct host connections, or they can connect to a network. A
maximum of 20 MAC addresses are allowed per port on the switch. A dynamic-access port can belong
to only one VLAN at a time, but the VLAN can change over time, depending on the MAC addresses seen.
Default VMPS Client Configuration
Table 12-7 shows the default VMPS and dynamic-access port configuration on client switches.
Table 12-7
Default VMPS Client and Dynamic-Access Port Configuration
Feature
Default Setting
VMPS domain server
None
VMPS reconfirm interval
60 minutes
VMPS server retry count
3
Dynamic-access ports
None configured
VMPS Configuration Guidelines
These guidelines and restrictions apply to dynamic-access port VLAN membership:
•
You should configure the VMPS before you configure ports as dynamic-access ports.
•
When you configure a port as a dynamic-access port, the spanning-tree Port Fast feature is
automatically enabled for that port. The Port Fast mode accelerates the process of bringing the port
into the forwarding state.
•
IEEE 802.1x ports cannot be configured as dynamic-access ports. If you try to enable IEEE 802.1x
on a dynamic-access (VQP) port, an error message appears, and IEEE 802.1x is not enabled. If you
try to change an IEEE 802.1x-enabled port to dynamic VLAN assignment, an error message appears,
and the VLAN configuration is not changed.
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Configuring VMPS
•
Trunk ports cannot be dynamic-access ports, but you can enter the switchport access vlan dynamic
interface configuration command for a trunk port. In this case, the switch retains the setting and
applies it if the port is later configured as an access port.
You must turn off trunking on the port before the dynamic-access setting takes effect.
•
Dynamic-access ports cannot be monitor ports.
•
Secure ports cannot be dynamic-access ports. You must disable port security on a port before it
becomes dynamic.
•
Private VLAN ports cannot be dynamic-access ports.
•
Dynamic-access ports cannot be members of an EtherChannel group.
•
Port channels cannot be configured as dynamic-access ports.
•
The VTP management domain of the VMPS client and the VMPS server must be the same.
•
The VLAN configured on the VMPS server should not be a voice VLAN.
Configuring the VMPS Client
You configure dynamic VLANs by using the VMPS (server). The switch can be a VMPS client; it cannot
be a VMPS server.
Entering the IP Address of the VMPS
You must first enter the IP address of the server to configure the switch as a client.
Beginning in privileged EXEC mode, follow these steps to enter the IP address of the VMPS:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
vmps server ipaddress primary
Enter the IP address of the switch acting as the primary VMPS server.
Step 3
vmps server ipaddress
(Optional) Enter the IP address of the switch acting as a secondary VMPS
server.
You can enter up to three secondary server addresses.
Step 4
end
Return to privileged EXEC mode.
Step 5
show vmps
Verify your entries in the VMPS Domain Server field of the display.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Note
You must have IP connectivity to the VMPS for dynamic-access ports to work. You can test for IP
connectivity by pinging the IP address of the VMPS and verifying that you get a response.
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Configuring VLANs
Configuring VMPS
Configuring Dynamic-Access Ports on VMPS Clients
Caution
Dynamic-access port VLAN membership is for end stations or hubs connected to end stations.
Connecting dynamic-access ports to other switches can cause a loss of connectivity.
Beginning in privileged EXEC mode, follow these steps to configure a dynamic-access port on a VMPS
client switch:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify the switch port that is connected to the end station, and enter
interface configuration mode.
Step 3
switchport mode access
Set the port to access mode.
Step 4
switchport access vlan dynamic
Configure the port as eligible for dynamic VLAN membership.
The dynamic-access port must be connected to an end station.
Step 5
end
Return to privileged EXEC mode.
Step 6
show interfaces interface-id switchport
Verify your entries in the Operational Mode field of the display.
Step 7
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To return an interface to its default configuration, use the default interface interface-id interface
configuration command. To return an interface to its default switchport mode (dynamic auto), use the no
switchport mode interface configuration command. To reset the access mode to the default VLAN for
the switch, use the no switchport access vlan interface configuration command.
Reconfirming VLAN Memberships
Beginning in privileged EXEC mode, follow these steps to confirm the dynamic-access port VLAN
membership assignments that the switch has received from the VMPS:
Command
Purpose
Step 1
vmps reconfirm
Reconfirm dynamic-access port VLAN membership.
Step 2
show vmps
Verify the dynamic VLAN reconfirmation status.
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Configuring VLANs
Configuring VMPS
Changing the Reconfirmation Interval
VMPS clients periodically reconfirm the VLAN membership information received from the VMPS.You
can set the number of minutes after which reconfirmation occurs.
Beginning in privileged EXEC mode, follow these steps to change the reconfirmation interval:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
vmps reconfirm minutes
Enter the number of minutes between reconfirmations of the dynamic
VLAN membership. The range is 1 to 120. The default is 60 minutes.
Step 3
end
Return to privileged EXEC mode.
Step 4
show vmps
Verify the dynamic VLAN reconfirmation status in the Reconfirm Interval
field of the display.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To return the switch to its default setting, use the no vmps reconfirm global configuration command.
Changing the Retry Count
Beginning in privileged EXEC mode, follow these steps to change the number of times that the switch
attempts to contact the VMPS before querying the next server:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
vmps retry count
Change the retry count. The retry range is 1 to 10; the default is 3.
Step 3
end
Return to privileged EXEC mode.
Step 4
show vmps
Verify your entry in the Server Retry Count field of the display.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To return the switch to its default setting, use the no vmps retry global configuration command.
Monitoring the VMPS
You can display information about the VMPS by using the show vmps privileged EXEC command. The
switch displays this information about the VMPS:
•
VMPS VQP Version—the version of VQP used to communicate with the VMPS. The switch queries
the VMPS that is using VQP version 1.
•
Reconfirm Interval—the number of minutes the switch waits before reconfirming the
VLAN-to-MAC-address assignments.
•
Server Retry Count—the number of times VQP resends a query to the VMPS. If no response is
received after this many tries, the switch starts to query the secondary VMPS.
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Configuring VMPS
•
VMPS domain server—the IP address of the configured VLAN membership policy servers. The
switch sends queries to the one marked current. The one marked primary is the primary server.
•
VMPS Action—the result of the most recent reconfirmation attempt. A reconfirmation attempt can
occur automatically when the reconfirmation interval expires, or you can force it by entering the
vmps reconfirm privileged EXEC command or its SNMP equivalent.
This is an example of output for the show vmps privileged EXEC command:
Switch# show vmps
VQP Client Status:
-------------------VMPS VQP Version:
1
Reconfirm Interval: 60 min
Server Retry Count: 3
VMPS domain server: 172.20.128.86 (primary, current)
172.20.128.87
Reconfirmation status
--------------------VMPS Action:
other
Troubleshooting Dynamic-Access Port VLAN Membership
The VMPS shuts down a dynamic-access port under these conditions:
•
The VMPS is in secure mode, and it does not allow the host to connect to the port. The VMPS shuts
down the port to prevent the host from connecting to the network.
•
More than 20 active hosts reside on a dynamic-access port.
To re-enable a disabled dynamic-access port, enter the shutdown interface configuration command
followed by the no shutdown interface configuration command.
VMPS Configuration Example
Figure 12-5 shows a network with a VMPS server switch and VMPS client switches with
dynamic-access ports. In this example, these assumptions apply:
•
The VMPS server and the VMPS client are separate switches.
•
The Catalyst 6500 series Switch A is the primary VMPS server.
•
The Catalyst 6500 series Switch C and Switch J are secondary VMPS servers.
•
End stations are connected to the clients, Switch B and Switch I.
•
The database configuration file is stored on the TFTP server with the IP address 172.20.22.7.
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Configuring VMPS
Figure 12-5
Dynamic Port VLAN Membership Configuration
TFTP server
Catalyst 6500 series switch A
Primary VMPS
Server 1
Router
172.20.26.150
172.20.22.7
Client switch B
End
station 1
Dynamic-access port
172.20.26.151
Trunk port
Switch C
172.20.26.152
Switch D
172.20.26.153
Switch E
172.20.26.154
Switch F
172.20.26.155
Switch G
172.20.26.156
Switch H
172.20.26.157
Dynamic-access port
Ethernet segment
(Trunk link)
End
station 2
Catalyst 6500 series
Secondary VMPS
Server 2
Client switch I
172.20.26.158
172.20.26.159
Catalyst 6500 series
Secondary VMPS
Server 3
101363t
Trunk port
Switch J
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13
Configuring VTP
This chapter describes how to use the VLAN Trunking Protocol (VTP) and the VLAN database for
managing VLANs with the switch.
Note
For complete syntax and usage information for the commands used in this chapter, see the command
reference for this release.
The chapter consists of these sections:
•
Understanding VTP, page 13-1
•
Configuring VTP, page 13-7
•
Monitoring VTP, page 13-16
Understanding VTP
VTP is a Layer 2 messaging protocol that maintains VLAN configuration consistency by managing the
addition, deletion, and renaming of VLANs on a network-wide basis. VTP minimizes misconfigurations
and configuration inconsistencies that can cause several problems, such as duplicate VLAN names,
incorrect VLAN-type specifications, and security violations.
Before you create VLANs, you must decide whether to use VTP in your network. Using VTP, you can
make configuration changes centrally on one or more switches and have those changes automatically
communicated to all the other switches in the network. Without VTP, you cannot send information about
VLANs to other switches.
VTP is designed to work in an environment where updates are made on a single switch and are sent
through VTP to other switches in the domain. It does not work well in a situation where multiple updates
to the VLAN database occur simultaneously on switches in the same domain, which would result in an
inconsistency in the VLAN database.
The switch supports 1005 VLANs, but the number of routed ports, SVIs, and other configured features
affects the usage of the switch hardware. If the switch is notified by VTP of a new VLAN and the switch
is already using the maximum available hardware resources, it sends a message that there are not enough
hardware resources available and shuts down the VLAN. The output of the show vlan user EXEC
command shows the VLAN in a suspended state.
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Understanding VTP
VTP version 1 and version 2 support only normal-range VLANs (VLAN IDs 1 to 1005). Cisco IOS
Release 12.2(52)SE and later support VTP version 3. VTP version 3 supports the entire VLAN range
(VLANs 1 to 4094). Extended range VLANs (VLANs 1006 to 4094) are supported only in VTP
version 3. You cannot convert from VTP version 3 to VTP version 2 if extended VLANs are configured
in the domain.
These sections contain this conceptual information:
•
The VTP Domain, page 13-2
•
VTP Modes, page 13-3
•
VTP Advertisements, page 13-3
•
VTP Version 2, page 13-4
•
VTP Version 3, page 13-5
•
VTP Pruning, page 13-5
The VTP Domain
A VTP domain (also called a VLAN management domain) consists of one switch or several
interconnected switches under the same administrative responsibility sharing the same VTP domain
name. A switch can be in only one VTP domain. You make global VLAN configuration changes for the
domain.
By default, the switch is in the VTP no-management-domain state until it receives an advertisement for
a domain over a trunk link (a link that carries the traffic of multiple VLANs) or until you configure a
domain name. Until the management domain name is specified or learned, you cannot create or modify
VLANs on a VTP server, and VLAN information is not propagated over the network.
If the switch receives a VTP advertisement over a trunk link, it inherits the management domain name
and the VTP configuration revision number. The switch then ignores advertisements with a different
domain name or an earlier configuration revision number.
Caution
Before adding a VTP client switch to a VTP domain, always verify that its VTP configuration revision
number is lower than the configuration revision number of the other switches in the VTP domain.
Switches in a VTP domain always use the VLAN configuration of the switch with the highest VTP
configuration revision number. If you add a switch that has a revision number higher than the revision
number in the VTP domain, it can erase all VLAN information from the VTP server and VTP domain.
See the “Adding a VTP Client Switch to a VTP Domain” section on page 13-15 for the procedure for
verifying and resetting the VTP configuration revision number.
When you make a change to the VLAN configuration on a VTP server, the change is propagated to all
switches in the VTP domain. VTP advertisements are sent over all IEEE trunk connections, including
Inter-Switch Link (ISL) and IEEE 802.1Q. VTP dynamically maps VLANs with unique names and
internal index associates across multiple LAN types. Mapping eliminates excessive device
administration required from network administrators.
If you configure a switch for VTP transparent mode, you can create and modify VLANs, but the changes
are not sent to other switches in the domain, and they affect only the individual switch. However,
configuration changes made when the switch is in this mode are saved in the switch running
configuration and can be saved to the switch startup configuration file.
For domain name and password configuration guidelines, see the “VTP Configuration Guidelines”
section on page 13-8.
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Configuring VTP
Understanding VTP
VTP Modes
You can configure a supported switch to be in one of the VTP modes listed in Table 13-1.
Table 13-1
VTP Modes
VTP Mode
Description
VTP server
In VTP server mode, you can create, modify, and delete VLANs, and specify other configuration
parameters (such as the VTP version) for the entire VTP domain. VTP servers advertise their VLAN
configurations to other switches in the same VTP domain and synchronize their VLAN configurations with
other switches based on advertisements received over trunk links.
VTP server is the default mode.
Note
VTP client
In VTP server mode, VLAN configurations are saved in NVRAM. If the switch detects a failure
while writing a configuration to NVRAM, VTP mode automatically changes from server mode to
client mode. If this happens, the switch cannot be returned to VTP server mode until the NVRAM
is functioning.
A VTP client behaves like a VTP server and transmits and receives VTP updates on its trunks, but you
cannot create, change, or delete VLANs on a VTP client. VLANs are configured on another switch in the
domain that is in server mode.
In VTP versions 1 and 2, in VTP client mode, VLAN configurations are not saved in NVRAM. In VTP
version 3, VLAN configurations are saved in NVRAM in client mode.
VTP transparent VTP transparent switches do not participate in VTP. A VTP transparent switch does not advertise its VLAN
configuration and does not synchronize its VLAN configuration based on received advertisements.
However, in VTP version 2 or version 3, transparent switches do forward VTP advertisements that they
receive from other switches through their trunk interfaces. You can create, modify, and delete VLANs on
a switch in VTP transparent mode.
In VTP versions 1 and 2, the switch must be in VTP transparent mode when you create extended-range
VLANs. VTP version 3 also supports creating extended-range VLANs in client or server mode. See the
“Configuring Extended-Range VLANs” section on page 12-11.
In VTP versions 1 and 2, the switch must be in VTP transparent mode when you create private VLANs and
when they are configured, you should not change the VTP mode from transparent to client or server mode.
VTP version 3 also supports private VLANs in client and server modes. See Chapter 15, “Configuring
Private VLANs.”
When the switch is in VTP transparent mode, the VTP and VLAN configurations are saved in NVRAM,
but they are not advertised to other switches. In this mode, VTP mode and domain name are saved in the
switch running configuration, and you can save this information in the switch startup configuration file by
using the copy running-config startup-config privileged EXEC command.
VTP off
A switch in VTP off mode functions in the same manner as a VTP transparent switch, except that it does
not forward VTP advertisements on trunks.
VTP Advertisements
Each switch in the VTP domain sends periodic global configuration advertisements from each trunk port
to a reserved multicast address. Neighboring switches receive these advertisements and update their VTP
and VLAN configurations as necessary.
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Understanding VTP
Note
Because trunk ports send and receive VTP advertisements, you must ensure that at least one trunk port
is configured on the switch and that this trunk port is connected to the trunk port of another switch.
Otherwise, the switch cannot receive any VTP advertisements. For more information on trunk ports, see
the “Configuring VLAN Trunks” section on page 12-15.
VTP advertisements distribute this global domain information:
•
VTP domain name
•
VTP configuration revision number
•
Update identity and update timestamp
•
MD5 digest VLAN configuration, including maximum transmission unit (MTU) size for each
VLAN.
•
Frame format
VTP advertisements distribute this VLAN information for each configured VLAN:
•
VLAN IDs (ISL and IEEE 802.1Q)
•
VLAN name
•
VLAN type
•
VLAN state
•
Additional VLAN configuration information specific to the VLAN type
In VTP version 3, VTP advertisements also include the primary server ID, an instance number, and a
start index.
VTP Version 2
If you use VTP in your network, you must decide which version of VTP to use. By default, VTP operates
in version 1.
VTP version 2 supports these features that are not supported in version 1:
•
Token Ring support—VTP version 2 supports Token Ring Bridge Relay Function (TrBRF) and
Token Ring Concentrator Relay Function (TrCRF) VLANs. For more information about Token Ring
VLANs, see the “Configuring Normal-Range VLANs” section on page 12-4.
•
Unrecognized Type-Length-Value (TLV) support—A VTP server or client propagates configuration
changes to its other trunks, even for TLVs it is not able to parse. The unrecognized TLV is saved in
NVRAM when the switch is operating in VTP server mode.
•
Version-Dependent Transparent Mode—In VTP version 1, a VTP transparent switch inspects VTP
messages for the domain name and version and forwards a message only if the version and domain
name match. Although VTP version 2 supports only one domain, a VTP version 2 transparent switch
forwards a message only when the domain name matches.
•
Consistency Checks—In VTP version 2, VLAN consistency checks (such as VLAN names and
values) are performed only when you enter new information through the CLI or SNMP. Consistency
checks are not performed when new information is obtained from a VTP message or when
information is read from NVRAM. If the MD5 digest on a received VTP message is correct, its
information is accepted.
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Understanding VTP
VTP Version 3
VTP version 3 supports these features that are not supported in version 1 or version 2:
•
Enhanced authentication—You can configure the authentication as hidden or secret. When hidden,
the secret key from the password string is saved in the VLAN database file, but it does not appear
in plain text in the configuration. Instead, the key associated with the password is saved in
hexadecimal format in the running configuration. You must reenter the password if you enter a
takeover command in the domain. When you enter the secret keyword, you can directly configure
the password secret key.
•
Support for extended range VLAN (VLANs 1006 to 4094) database propagation. VTP versions 1
and 2 propagate only VLANs 1 to 1005. If extended VLANs are configured, you cannot convert
from VTP version 3 to version 1 or 2.
Note
VTP pruning still applies only to VLANs 1 to 1005, and VLANs 1002 to 1005 are still
reserved and cannot be modified.
•
Private VLAN support.
•
Support for any database in a domain. In addition to propagating VTP information, version 3 can
propagate Multiple Spanning Tree (MST) protocol database information. A separate instance of the
VTP protocol runs for each application that uses VTP.
•
VTP primary server and VTP secondary servers. A VTP primary server updates the database
information and sends updates that are honored by all devices in the system. A VTP secondary server
can only back up the updated VTP configurations received from the primary server to its NVRAM.
By default, all devices come up as secondary servers. You can enter the vtp primary privileged
EXEC command to specify a primary server. Primary server status is only needed for database
updates when the administrator issues a takeover message in the domain. You can have a working
VTP domain without any primary servers. Primary server status is lost if the device reloads or
domain parameters change, even when a password is configured on the switch.
•
The option to turn VTP on or off on a per-trunk (per-port) basis. You can enable or disable VTP per
port by entering the [no] vtp interface configuration command. When you disable VTP on trunking
ports, all VTP instances for that port are disabled. You cannot set VTP to off for the MST database
and on for the VLAN database on the same port.
When you globally set VTP mode to off, it applies to all the trunking ports in the system. However,
you can specify on or off on a per-VTP instance basis. For example, you can configure the switch
as a VTP server for the VLAN database but with VTP off for the MST database.
VTP Pruning
VTP pruning increases network available bandwidth by restricting flooded traffic to those trunk links
that the traffic must use to reach the destination devices. Without VTP pruning, a switch floods
broadcast, multicast, and unknown unicast traffic across all trunk links within a VTP domain even
though receiving switches might discard them. VTP pruning is disabled by default.
VTP pruning blocks unneeded flooded traffic to VLANs on trunk ports that are included in the
pruning-eligible list. Only VLANs included in the pruning-eligible list can be pruned. By default,
VLANs 2 through 1001 are pruning eligible switch trunk ports. If the VLANs are configured as
pruning-ineligible, the flooding continues. VTP pruning is supported in all VTP versions.
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Understanding VTP
Figure 13-1 shows a switched network without VTP pruning enabled. Port 1 on Switch A and Port 2 on
Switch D are assigned to the Red VLAN. If a broadcast is sent from the host connected to Switch A,
Switch A floods the broadcast and every switch in the network receives it, even though Switches C, E,
and F have no ports in the Red VLAN.
Figure 13-1
Flooding Traffic without VTP Pruning
Switch D
Port 2
Switch E
Switch B
Red
VLAN
Switch F
Switch C
89240
Port 1
Switch A
Figure 13-2 shows a switched network with VTP pruning enabled. The broadcast traffic from Switch A
is not forwarded to Switches C, E, and F because traffic for the Red VLAN has been pruned on the links
shown (Port 5 on Switch B and Port 4 on Switch D).
Figure 13-2
Optimized Flooded Traffic with VTP Pruning
Switch D
Port 2
Flooded traffic
is pruned.
Port
4
Switch B
Red
VLAN
Switch E
Flooded traffic
is pruned.
Port
5
Switch F
Switch C
Switch A
89241
Port 1
Enabling VTP pruning on a VTP server enables pruning for the entire management domain. Making
VLANs pruning-eligible or pruning-ineligible affects pruning eligibility for those VLANs on that trunk
only (not on all switches in the VTP domain).
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Configuring VTP
See the “Enabling VTP Pruning” section on page 13-14. VTP pruning takes effect several seconds after
you enable it. VTP pruning does not prune traffic from VLANs that are pruning-ineligible. VLAN 1 and
VLANs 1002 to 1005 are always pruning-ineligible; traffic from these VLANs cannot be pruned.
Extended-range VLANs (VLAN IDs higher than 1005) are also pruning-ineligible.
VTP pruning is not designed to function in VTP transparent mode. If one or more switches in the
network are in VTP transparent mode, you should do one of these:
•
Turn off VTP pruning in the entire network.
•
Turn off VTP pruning by making all VLANs on the trunk of the switch upstream to the VTP
transparent switch pruning ineligible.
To configure VTP pruning on an interface, use the switchport trunk pruning vlan interface
configuration command (see the “Changing the Pruning-Eligible List” section on page 12-21). VTP
pruning operates when an interface is trunking. You can set VLAN pruning-eligibility, whether or not
VTP pruning is enabled for the VTP domain, whether or not any given VLAN exists, and whether or not
the interface is currently trunking.
Configuring VTP
These sections contain this configuration information:
•
Default VTP Configuration, page 13-7
•
VTP Configuration Guidelines, page 13-8
•
Configuring VTP Mode, page 13-10
•
Enabling the VTP Version, page 13-13
•
Enabling VTP Pruning, page 13-14
•
Configuring VTP on a Per-Port Basis, page 13-15
•
Adding a VTP Client Switch to a VTP Domain, page 13-15
Default VTP Configuration
Table 13-2 shows the default VTP configuration.
Table 13-2
Default VTP Configuration
Feature
Default Setting
VTP domain name
Null.
VTP mode (VTP version 1
and version 2)
Server.
VTP mode (VTP version 3)
The mode is the same as the mode in VTP version 1 or 2 before
conversion to version 3.
VTP version
Version 1 (Version 2 is disabled).
MST database mode
Transparent.
VTP version 3 server type
Secondary.
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Configuring VTP
Table 13-2
Default VTP Configuration (continued)
Feature
Default Setting
VTP password
None.
VTP pruning
Disabled.
VTP Configuration Guidelines
You can use the vtp global configuration command to set the VTP password, the version, the VTP file
name, the interface providing updated VTP information, the domain name, and the mode, and to disable
or enable pruning. For more information about available keywords, see the command descriptions in the
command reference for this release. The VTP information is saved in the VTP VLAN database. When
VTP mode is transparent, the VTP domain name and mode are also saved in the switch running
configuration file, and you can save it in the switch startup configuration file by entering the copy
running-config startup-config privileged EXEC command. You must use this command if you want to
save VTP mode as transparent, even if the switch resets.
When you save VTP information in the switch startup configuration file and reboot the switch, the switch
configuration is selected as follows:
•
If the VTP mode is transparent in the startup configuration and the VLAN database and the VTP
domain name from the VLAN database matches that in the startup configuration file, the VLAN
database is ignored (cleared), and the VTP and VLAN configurations in the startup configuration
file are used. The VLAN database revision number remains unchanged in the VLAN database.
•
If the VTP mode or domain name in the startup configuration do not match the VLAN database, the
domain name and VTP mode and configuration for the first 1005 VLANs use the VLAN database
information.
Domain Names
When configuring VTP for the first time, you must always assign a domain name. You must configure
all switches in the VTP domain with the same domain name. Switches in VTP transparent mode do not
exchange VTP messages with other switches, and you do not need to configure a VTP domain name
for them.
Note
Caution
If NVRAM and DRAM storage is sufficient, all switches in a VTP domain should be in VTP server
mode.
Do not configure a VTP domain if all switches are operating in VTP client mode. If you configure the
domain, it is impossible to make changes to the VLAN configuration of that domain. Make sure that you
configure at least one switch in the VTP domain for VTP server mode.
Passwords
You can configure a password for the VTP domain, but it is not required. If you do configure a domain
password, all domain switches must share the same password and you must configure the password on
each switch in the management domain. Switches without a password or with the wrong password reject
VTP advertisements.
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Configuring VTP
If you configure a VTP password for a domain, a switch that is booted without a VTP configuration does
not accept VTP advertisements until you configure it with the correct password. After the configuration,
the switch accepts the next VTP advertisement that uses the same password and domain name in the
advertisement.
If you are adding a new switch to an existing network with VTP capability, the new switch learns the
domain name only after the applicable password has been configured on it.
Caution
When you configure a VTP domain password, the management domain does not function properly if you
do not assign a management domain password to each switch in the domain.
VTP Version
Follow these guidelines when deciding which VTP version to implement:
•
All switches in a VTP domain must have the same domain name, but they do not need to run the
same VTP version.
•
A VTP version 2-capable switch can operate in the same VTP domain as a switch running VTP
version 1 if version 2 is disabled on the version 2-capable switch (version 2 is disabled by default).
•
If a switch running VTP version 1 but capable of running VTP version 2 receives VTP version 3
advertisements, it automatically moves to VTP version 2.
•
If a switch running VTP version 3 is connected to a switch running VTP version 1, the VTP version
1 switch moves to VTP version 2, and the VTP version 3 switch sends scaled-down versions of the
VTP packets so that the VTP version 2 switch can update its database.
•
A switch running VTP version 3 cannot move to version 1 or 2 if it has extended VLANs.
•
Do not enable VTP version 2 on a switch unless all of the switches in the same VTP domain are
version-2-capable. When you enable version 2 on a switch, all of the version-2-capable switches in
the domain enable version 2. If there is a version 1-only switch, it does not exchange VTP
information with switches that have version 2 enabled.
•
Cisco recommends placing VTP version 1 and 2 switches at the edge of the network because they
do not forward VTP version 3 advertisements.
•
If there are TrBRF and TrCRF Token Ring networks in your environment, you must enable VTP
version 2 or version 3 for Token Ring VLAN switching to function properly. To run Token Ring and
Token Ring-Net, disable VTP version 2 or 3.
•
VTP version 1 and version 2 do not propagate configuration information for extended range VLANs
(VLANs 1006 to 4094). You must configure these VLANs manually on each device. VTP version 3
supports extended-range VLANs. You cannot convert from VTP version 3 to VTP version 2 if
extended VLANs are configured.
•
When a VTP version 3 device trunk port receives messages from a VTP version 2 device, it sends a
scaled-down version of the VLAN database on that particular trunk in VTP version 2 format. A VTP
version 3 device does not send VTP version 2-formatted packets on a trunk unless it first receives
VTP version 2 packets on that trunk port.
•
When a VTP version 3 device detects a VTP version 2 device on a trunk port, it continues to send
VTP version 3 packets, in addition to VTP version 2 packets, to allow both kinds of neighbors to
coexist on the same trunk.
•
A VTP version 3 device does not accept configuration information from a VTP version 2 or version
1 device.
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Configuring VTP
•
Two VTP version 3 regions can only communicate in transparent mode over a VTP version 1 or
version 2 region.
•
Devices that are only VTP version 1 capable cannot interoperate with VTP version 3 devices.
Configuration Requirements
When you configure VTP, you must configure a trunk port so that the switch can send and receive VTP
advertisements to and from other switches in the domain.
For more information, see the “Configuring VLAN Trunks” section on page 12-15.
In VTP versions 1 and 2, when you configure extended-range VLANs on the switch, the switch must be
in VTP transparent mode. VTP version 3 also supports creating extended-range VLANs in client or
server mode.
VTP versions 1 and 2 do not support private VLANs. If you configure private VLANs in VTP version 1
or version 2, the switch must be in VTP transparent mode. When private VLANs are configured on the
switch, do not change the VTP mode from transparent to client or server mode. VTP version 3 supports
private VLANs.
Configuring VTP Mode
You can configure VTP mode as one of these:
•
When a switch is in VTP server mode, you can change the VLAN configuration and have it
propagated throughout the network.
•
When a switch is in VTP client mode, you cannot change its VLAN configuration. The client switch
receives VTP updates from a VTP server in the VTP domain and then modifies its configuration
accordingly.
•
When you configure the switch for VTP transparent mode, VTP is disabled on the switch. The
switch does not send VTP updates and does not act on VTP updates received from other switches.
However, a VTP transparent switch running VTP version 2 does forward received VTP
advertisements on its trunk links.
•
VTP off mode is the same as VTP transparent mode except that VTP advertisements are not
forwarded.
Follow these guidelines:
•
Note
For VTP version 1 and version 2, if extended-range VLANs are configured on the switch, you cannot
change VTP mode to client or server. You receive an error message, and the configuration is not
allowed. VTP version 1 and version 2 do not propagate configuration information for extended range
VLANs (VLANs 1006 to 4094). You must manually configure these VLANs on each device.
For VTP version 1 and 2, before you create extended-range VLANs (VLAN IDs 1006 to 4094),
you must set VTP mode to transparent by using the vtp mode transparent global configuration
command. Save this configuration to the startup configuration so that the switch starts in VTP
transparent mode. Otherwise, you lose the extended-range VLAN configuration if the switch
resets and boots up in VTP server mode (the default).
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Configuring VTP
Caution
•
VTP version 3 supports extended-range VLANs. If extended VLANs are configured, you cannot
convert from VTP version 3 to VTP version 2.
•
If you configure the switch for VTP client mode, the switch does not create the VLAN database file
(vlan.dat). If the switch is then powered off, it resets the VTP configuration to the default. To keep
the VTP configuration with VTP client mode after the switch restarts, you must first configure the
VTP domain name before the VTP mode.
If all switches are operating in VTP client mode, do not configure a VTP domain name. If you do, it is
impossible to make changes to the VLAN configuration of that domain. Therefore, make sure you
configure at least one switch as a VTP server.
Beginning in privileged EXEC mode, follow these steps to configure the VTP mode:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
vtp domain domain-name
Configure the VTP administrative-domain name. The name can be 1 to 32
characters. All switches operating in VTP server or client mode under the
same administrative responsibility must be configured with the same
domain name.
This command is optional for modes other than server mode. VTP server
mode requires a domain name. If the switch has a trunk connection to a
VTP domain, the switch learns the domain name from the VTP server in the
domain.
You should configure the VTP domain before configuring other VTP
parameters.
Step 3
Step 4
vtp mode {client | server |
transparent | off} {vlan | mst |
unknown}
vtp password password
Configure the switch for VTP mode (client, server, transparent or off).
(Optional) Configure the database:
•
vlan—the VLAN database is the default if none are configured.
•
mst—the multiple spanning tree (MST) database.
•
unknown—an unknown database type.
(Optional) Set the password for the VTP domain. The password can be 8 to
64 characters. If you configure a VTP password, the VTP domain does not
function properly if you do not assign the same password to each switch in
the domain.
See the “Configuring a VTP Version 3 Password” section on page 13-12 for
options available with VTP version 3.
Step 5
end
Return to privileged EXEC mode.
Step 6
show vtp status
Verify your entries in the VTP Operating Mode and the VTP Domain Name
fields of the display.
Step 7
copy running-config startup-config
(Optional) Save the configuration in the startup configuration file.
Note
Only VTP mode and domain name are saved in the switch running
configuration and can be copied to the startup configuration file.
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Configuring VTP
Configuring VTP
When you configure a domain name, it cannot be removed; you can only reassign a switch to a different
domain.
To return the switch to a no-password state, use the no vtp password global configuration command.
This example shows how to use global configuration mode to configure the switch as a VTP server with
the domain name eng_group and the password mypassword:
Switch(config)# vtp domain eng_group
Setting VTP domain name to eng_group.
Switch(config)# vtp mode server
Setting device to VTP Server mode for VLANS.
Switch(config)# vtp password mypassword
Setting device VLAN database password to mypassword.
Switch(config)# end
Use the no vtp mode global configuration command to return the switch to VTP server mode. To return
the switch to a no-password state, use the no vtp password privileged EXEC command. When you
configure a domain name, it cannot be removed; you can only reassign a switch to a different domain.
Configuring a VTP Version 3 Password
Beginning in privileged EXEC mode, follow these steps to configure the password when using VTP
version 3:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
vtp password password [hidden |
secret]
(Optional) Set the password for the VTP domain. The password can be 8 to
64 characters.
•
(Optional) hidden—Enter hidden to ensure that the secret key
generated from the password string is saved in the nvam:vlan.dat file.
If you configure a takeover by configuring a VTP primary server, you
are prompted to reenter the password.
•
(Optional) secret—Enter secret to directly configure the password.
The secret password must contain 32 hexadecimal characters.
Step 3
end
Return to privileged EXEC mode.
Step 4
show vtp password
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save the configuration in the startup configuration file.
To clear the password, enter the no vtp password global configuration command.
This example shows how to configure a hidden password and how it appears.
Switch(config)# vtp password mypassword hidden
Generating the secret associated to the password.
Switch(config)# end
Switch# show vtp password
VTP password: 89914640C8D90868B6A0D8103847A733
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Configuring VTP
Configuring VTP
Configuring a VTP Version 3 Primary Server
Beginning in privileged EXEC mode, follow these steps on a VTP server to configure it as a VTP
primary server (version 3 only), which starts a takeover operation:
Step 1
Command
Purpose
vtp primary-server [vlan | mst]
[force]
Change the operational state of a switch from a secondary server (the
default) to a primary server and advertise the configuration to the domain.
If the switch password is configured as hidden, you are prompted to reenter
the password.
•
(Optional) vlan—Select the VLAN database as the takeover feature.
This is the default.
•
(Optional) mst—Select the multiple spanning tree (MST) database as
the takeover feature.
•
(Optional) force—Entering force overwrites the configuration of any
conflicting servers. If you do not enter force, you are prompted for
confirmation before the takeover.
This example shows how to configure a switch as the primary server for the VLAN database (the default)
when a hidden or secret password was configured:
Switch# vtp primary vlan
Enter VTP password: mypassword
This switch is becoming Primary server for vlan feature in the VTP
domain
VTP Database Conf Switch ID
Primary Server Revision System Name
------------ ---- -------------- -------------- -------- -------------------VLANDB
Yes 00d0.00b8.1400=00d0.00b8.1400 1
stp7
Do you want to continue (y/n) [n]? y
Enabling the VTP Version
VTP version 2 and version 3 are disabled by default.
Caution
•
When you enable VTP version 2 on a switch, every VTP version 2-capable switch in the VTP
domain enables version 2. To enable VTP version 3, you must manually configure it on each switch.
•
With VTP versions 1 and 2, you can configure the version only on switches in VTP server or
transparent mode. If a switch is running VTP version 3, you can change to version 2 when the switch
is in client mode if no extended VLANs exist, no private VLANs exist, and no hidden password was
configured.
VTP version 1 and VTP version 2 are not interoperable on switches in the same VTP domain. Do not
enable VTP version 2 unless every switch in the VTP domain supports version 2.
•
In TrCRF and TrBRF Token ring environments, you must enable VTP version 2 or VTP version 3
for Token Ring VLAN switching to function properly. For Token Ring and Token Ring-Net media,
disable VTP version 2 must be disabled.
•
VTP version 3 is supported on switches running Cisco IOS Release 12.2(52) SE or later.
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Configuring VTP
Caution
In VTP version 3, both the primary and secondary servers can exist on an instance in the domain.
For more information on VTP version configuration guidelines, see the “VTP Version” section on
page 13-9
Beginning in privileged EXEC mode, follow these steps to configure the VTP version:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
vtp version {1 | 2 | 3}
Enable the VTP version on the switch. The default is VTP version 1.
Step 3
end
Return to privileged EXEC mode.
Step 4
show vtp status
Verify that the configured VTP version is enabled.
Step 5
copy running-config
startup-config
(Optional) Save the configuration in the startup configuration file.
To return to the default VTP version 1, use the no vtp version global configuration command.
Enabling VTP Pruning
Pruning increases available bandwidth by restricting flooded traffic to those trunk links that the traffic
must use to access the destination devices. You can only enable VTP pruning on a switch in VTP server
mode.
Beginning in privileged EXEC mode, follow these steps to enable VTP pruning in the VTP domain:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
vtp pruning
Enable pruning in the VTP administrative domain.
By default, pruning is disabled. You need to enable pruning on only one switch
in VTP server mode.
Step 3
end
Return to privileged EXEC mode.
Step 4
show vtp status
Verify your entries in the VTP Pruning Mode field of the display.
To disable VTP pruning, use the no vtp pruning global configuration command.
With VTP versions 1 and 2, when you enable pruning on the VTP server, it is enabled for the entire VTP
domain. In VTP version 3, you must manually enable pruning on each switch in the domain.
Only VLANs included in the pruning-eligible list can be pruned. By default, VLANs 2 through 1001 are
pruning-eligible on trunk ports. Reserved VLANs and extended-range VLANs cannot be pruned. To
change the pruning-eligible VLANs, see the “Changing the Pruning-Eligible List” section on
page 12-21.
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Configuring VTP
Configuring VTP
Configuring VTP on a Per-Port Basis
With VTP version 3, you can enable or disable VTP on a per-port basis. You can enable VTP only on
ports that are in trunk mode. Incoming and outgoing VTP traffic are blocked, not forwarded.
Beginning in privileged EXEC mode, follow these steps to enable VTP on a port:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Identify an interface, and enter interface configuration mode.
Step 3
vtp
Enable VTP on the specified port.
Step 4
end
Return to privileged EXEC mode.
Step 5
show running-config interface
interface-id
Verify the change to the port.
Step 6
show vtp status
Verify the configuration.
Adding a VTP Client Switch to a VTP Domain
Before adding a VTP client to a VTP domain, always verify that its VTP configuration revision number
is lower than the configuration revision number of the other switches in the VTP domain. Switches in a
VTP domain always use the VLAN configuration of the switch with the highest VTP configuration
revision number. With VTP versions 1 and 2, adding a switch that has a revision number higher than the
revision number in the VTP domain can erase all VLAN information from the VTP server and VTP
domain. With VTP version 3, the VLAN information is not erased.
Beginning in privileged EXEC mode, follow these steps to verify and reset the VTP configuration
revision number on a switch before adding it to a VTP domain:
Step 1
Command
Purpose
show vtp status
Check the VTP configuration revision number.
If the number is 0, add the switch to the VTP domain.
If the number is greater than 0, follow these steps:
a.
Write down the domain name.
b.
Write down the configuration revision number.
c.
Continue with the next steps to reset the switch configuration revision number.
Step 2
configure terminal
Enter global configuration mode.
Step 3
vtp domain domain-name
Change the domain name from the original one displayed in Step 1 to a new name.
Step 4
end
The VLAN information on the switch is updated and the configuration revision
number is reset to 0. You return to privileged EXEC mode.
Step 5
show vtp status
Verify that the configuration revision number has been reset to 0.
Step 6
configure terminal
Enter global configuration mode.
Step 7
vtp domain domain-name
Enter the original domain name on the switch.
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Monitoring VTP
Command
Purpose
Step 8
end
The VLAN information on the switch is updated, and you return to privileged EXEC
mode.
Step 9
show vtp status
(Optional) Verify that the domain name is the same as in Step 1 and that the
configuration revision number is 0.
After resetting the configuration revision number, add the switch to the VTP domain.
Note
You can use the vtp mode transparent global configuration command to disable VTP on the switch and
then to change its VLAN information without affecting the other switches in the VTP domain.
Monitoring VTP
You monitor VTP by displaying VTP configuration information: the domain name, the current VTP
revision, and the number of VLANs. You can also display statistics about the advertisements sent and
received by the switch.
Table 13-3 shows the privileged EXEC commands for monitoring VTP activity.
Table 13-3
VTP Monitoring Commands
Command
Purpose
show vtp counters
Display counters about VTP messages that have been sent and received.
show vtp devices [conflict] Display information about all VTP version 3 devices in the domain.
Conflicts are VTP version 3 devices with conflicting primary servers.
The show vtp devices command does not display information when the
switch is in transparent or off mode.
show vtp interface
[interface-id]
Display VTP status and configuration for all interfaces or the specified
interface.
show vtp password
Display the VTP password. The form of the password displayed depends
on whether or not the hidden keyword was entered and if encryption is
enabled on the switch.
show vtp status
Display the VTP switch configuration information.
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14
Configuring Voice VLAN
This chapter describes how to configure the voice VLAN feature on the switch. Voice VLAN is referred
to as an auxiliary VLAN in some Catalyst 6500 family switch documentation.
Note
For complete syntax and usage information for the commands used in this chapter, see the command
reference for this release.
This chapter consists of these sections:
•
Understanding Voice VLAN, page 14-1
•
Configuring Voice VLAN, page 14-3
•
Displaying Voice VLAN, page 14-7
Understanding Voice VLAN
The voice VLAN feature enables access ports to carry IP voice traffic from an IP phone. When the switch
is connected to a Cisco 7960 IP Phone, the phone sends voice traffic with Layer 3 IP precedence and
Layer 2 class of service (CoS) values, which are both set to 5 by default. Because the sound quality of
an IP phone call can deteriorate if the data is unevenly sent, the switch supports quality of service (QoS)
based on IEEE 802.1p CoS. QoS uses classification and scheduling to send network traffic from the
switch in a predictable manner. For more information on QoS, see Chapter 34, “Configuring QoS.”
The Cisco 7960 IP Phone is a configurable device, and you can configure it to forward traffic with an
IEEE 802.1p priority. You can configure the switch to trust or override the traffic priority assigned by a
Cisco IP Phone.
The Cisco IP Phone contains an integrated three-port 10/100 switch as shown in Figure 14-1. The ports
provide dedicated connections to these devices:
•
Port 1 connects to the switch or other voice-over-IP (VoIP) device.
•
Port 2 is an internal 10/100 interface that carries the IP Phone traffic.
•
Port 3 (access port) connects to a PC or other device.
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Configuring Voice VLAN
Understanding Voice VLAN
Figure 14-1 shows one way to connect a Cisco 7960 IP Phone.
Figure 14-1
Cisco 7960 IP Phone Connected to a Switch
Cisco IP Phone 7960
Phone
ASIC
P2
3-port
switch
P3
Access
port
101351
P1
PC
Cisco IP Phone Voice Traffic
You can configure an access port with an attached Cisco IP Phone to use one VLAN for voice traffic and
another VLAN for data traffic from a device attached to the phone. You can configure access ports on
the switch to send Cisco Discovery Protocol (CDP) packets that instruct an attached phone to send voice
traffic to the switch in any of these ways:
Note
•
In the voice VLAN tagged with a Layer 2 CoS priority value
•
In the access VLAN tagged with a Layer 2 CoS priority value
•
In the access VLAN, untagged (no Layer 2 CoS priority value)
In all configurations, the voice traffic carries a Layer 3 IP precedence value (the default is 5 for voice
traffic and 3 for voice control traffic).
Cisco IP Phone Data Traffic
The switch can also process tagged data traffic (traffic in IEEE 802.1Q or IEEE 802.1p frame types) from
the device attached to the access port on the Cisco IP Phone (see Figure 14-1). You can configure Layer 2
access ports on the switch to send CDP packets that instruct the attached phone to configure the phone
access port in one of these modes:
•
In trusted mode, all traffic received through the access port on the Cisco IP Phone passes through
the phone unchanged.
•
In untrusted mode, all traffic in IEEE 802.1Q or IEEE 802.1p frames received through the access
port on the Cisco IP Phone receive a configured Layer 2 CoS value. The default Layer 2 CoS value
is 0. Untrusted mode is the default.
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Configuring Voice VLAN
Note
Untagged traffic from the device attached to the Cisco IP Phone passes through the phone unchanged,
regardless of the trust state of the access port on the phone.
Configuring Voice VLAN
These sections contain this configuration information:
•
Default Voice VLAN Configuration, page 14-3
•
Voice VLAN Configuration Guidelines, page 14-3
•
Configuring a Port Connected to a Cisco 7960 IP Phone, page 14-4
Default Voice VLAN Configuration
The voice VLAN feature is disabled by default.
When the voice VLAN feature is enabled, all untagged traffic is sent according to the default CoS
priority of the port.
The CoS value is not trusted for IEEE 802.1p or IEEE 802.1Q tagged traffic.
Voice VLAN Configuration Guidelines
These are the voice VLAN configuration guidelines:
•
Note
You should configure voice VLAN on switch access ports; voice VLAN is not supported on
trunk ports. You can configure a voice VLAN only on Layer 2 ports.
Trunk ports can carry any number of voice VLANs, similar to regular VLANs. The configuration of
voice VLANs is not required on trunk ports.
•
The voice VLAN should be present and active on the switch for the IP phone to correctly
communicate on the voice VLAN. Use the show vlan privileged EXEC command to see if the
VLAN is present (listed in the display). If the VLAN is not listed, see Chapter 12, “Configuring
VLANs,” for information on how to create the voice VLAN.
•
Do not configure voice VLAN on private VLAN ports.
•
Before you enable voice VLAN, we recommend that you enable QoS on the switch by entering the
mls qos global configuration command and configure the port trust state to trust by entering the mls
qos trust cos interface configuration command. If you use the auto-QoS feature, these settings are
automatically configured. For more information, see Chapter 34, “Configuring QoS.”
•
You must enable CDP on the switch port connected to the Cisco IP Phone to send the configuration
to the phone. (CDP is globally enabled by default on all switch interfaces.)
•
The Port Fast feature is automatically enabled when voice VLAN is configured. When you disable
voice VLAN, the Port Fast feature is not automatically disabled.
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Configuring Voice VLAN
•
If the Cisco IP Phone and a device attached to the phone are in the same VLAN, they must be in the
same IP subnet. These conditions indicate that they are in the same VLAN:
– They both use IEEE 802.1p or untagged frames.
– The Cisco IP Phone uses IEEE 802.1p frames, and the device uses untagged frames.
– The Cisco IP Phone uses untagged frames, and the device uses IEEE 802.1p frames.
– The Cisco IP Phone uses IEEE 802.1Q frames, and the voice VLAN is the same as the access
VLAN.
•
The Cisco IP Phone and a device attached to the phone cannot communicate if they are in the same
VLAN and subnet but use different frame types because traffic in the same subnet is not routed
(routing would eliminate the frame type difference).
•
You cannot configure static secure MAC addresses in the voice VLAN.
•
Voice VLAN ports can also be these port types:
– Dynamic access port. See the “Configuring Dynamic-Access Ports on VMPS Clients” section
on page 12-29 for more information.
– IEEE 802.1x authenticated port. See the “Configuring 802.1x Authentication” section on
page 8-41 for more information.
Note
If you enable IEEE 802.1x on an access port on which a voice VLAN is configured and
to which a Cisco IP Phone is connected, the phone loses connectivity to the switch for
up to 30 seconds.
– Protected port. See the “Configuring Protected Ports” section on page 24-6 for more
information.
– A source or destination port for a SPAN or RSPAN session.
– Secure port. See the “Configuring Port Security” section on page 24-8 for more information.
Note
When you enable port security on an interface that is also configured with a voice
VLAN, you must set the maximum allowed secure addresses on the port to two plus the
maximum number of secure addresses allowed on the access VLAN. When the port is
connected to a Cisco IP Phone, the phone requires up to two MAC addresses. The phone
address is learned on the voice VLAN and might also be learned on the access VLAN.
Connecting a PC to the phone requires additional MAC addresses.
Configuring a Port Connected to a Cisco 7960 IP Phone
Because a Cisco 7960 IP Phone also supports a connection to a PC or other device, a port connecting the
switch to a Cisco IP Phone can carry mixed traffic. You can configure a port to decide how the Cisco IP
Phone carries voice traffic and data traffic.
These sections contain this configuration information:
•
Configuring Cisco IP Phone Voice Traffic, page 14-5
•
Configuring the Priority of Incoming Data Frames, page 14-6
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Configuring Voice VLAN
Configuring Cisco IP Phone Voice Traffic
You can configure a port connected to the Cisco IP Phone to send CDP packets to the phone to configure
the way in which the phone sends voice traffic. The phone can carry voice traffic in IEEE 802.1Q frames
for a specified voice VLAN with a Layer 2 CoS value. It can use IEEE 802.1p priority tagging to give
voice traffic a higher priority and forward all voice traffic through the native (access) VLAN. The Cisco
IP Phone can also send untagged voice traffic or use its own configuration to send voice traffic in the
access VLAN. In all configurations, the voice traffic carries a Layer 3 IP precedence value (the default
is 5).
Beginning in privileged EXEC mode, follow these steps to configure voice traffic on a port:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify the interface connected to the phone, and enter interface
configuration mode.
Step 3
mls qos trust cos
Configure the interface to classify incoming traffic packets by using the
packet CoS value. For untagged packets, the port default CoS value is used.
Note
Step 4
Before configuring the port trust state, you must first globally enable
QoS by using the mls qos global configuration command.
switchport voice {detect
Configure how the Cisco IP Phone carries voice traffic:
cisco-phone [full-duplex] | vlan
• detect—Configure the interface to detect and recognize a Cisco IP
{vlan-id | dot1p | none | untagged}}
phone.
•
cisco-phone—When you initially implement the switchport voice detect
command, this is the only allowed option. The default is no switchport
voice detect cisco-phone [full-duplex].
•
full-duplex—(Optional) Configure the switch to only accept a
full-duplex Cisco IP phone.
•
vlan-id—Configure the phone to forward all voice traffic through the
specified VLAN. By default, the Cisco IP Phone forwards the voice
traffic with an IEEE 802.1Q priority of 5. Valid VLAN IDs are 1 to
4094.
•
dot1p—Configure the phone to use IEEE 802.1p priority tagging for
voice traffic and to use the default native VLAN (VLAN 0) to carry all
traffic. By default, the Cisco IP Phone forwards the voice traffic with an
IEEE 802.1p priority of 5.
•
none—Allow the phone to use its own configuration to send untagged
voice traffic.
•
untagged—Configure the phone to send untagged voice traffic.
Step 5
end
Return to privileged EXEC mode.
Step 6
show interfaces interface-id
switchport or
Verify your voice VLAN entries.
show running-config interface
interface-id
Verify your QoS and voice VLAN entries.
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Step 7
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Configuring Voice VLAN
This example shows how to configure a port connected to a Cisco IP Phone to use the CoS value to
classify incoming traffic, to use IEEE 802.1p priority tagging for voice traffic, and to use the default
native VLAN (VLAN 0) to carry all traffic:
Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# interface gigabitethernet0/1
Switch(config-if)# mls qos trust cos
Switch(config-if)# switchport voice vlan dot1p
Switch(config-if)# end
To return the port to its default setting, use the no switchport voice vlan interface configuration
command.
This example shows how to enable switchport voice detect on a Cisco IP Phone:
Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# interface gigabithernet 0/1
Switch(config-if)# switchport voice?
detect
detection enhancement keyword
vlan
VLAN for voice traffic
Switch(config-if)# switchport voice detect?
cisco-phone
Cisco IP Phone
Switch(config-if)# switchport voice detect cisco-phone?
full-duplex
Cisco IP Phone
Switch(config-if)# switchport voice detect cisco-phone full-duplex
full-duplex
full duplex keyword
Switch(config-if)# end
This example shows how to disable switchport voice detect on a Cisco IP Phone:
Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# interface gigabithernet 0/1
Switch(config-if)# no switchport voice detect cisco-phone
Switch(config-if)# no switchport voice detect cisco-phone full-duplex
Configuring the Priority of Incoming Data Frames
You can connect a PC or other data device to a Cisco IP Phone port. To process tagged data traffic (in
IEEE 802.1Q or IEEE 802.1p frames), you can configure the switch to send CDP packets to instruct the
phone how to send data packets from the device attached to the access port on the Cisco IP Phone. The
PC can generate packets with an assigned CoS value. You can configure the phone to not change (trust)
or to override (not trust) the priority of frames arriving on the phone port from connected devices.
Beginning in privileged EXEC mode, follow these steps to set the priority of data traffic received from
the nonvoice port on the Cisco IP Phone:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify the interface connected to the Cisco IP Phone, and enter interface
configuration mode.
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Displaying Voice VLAN
Step 3
Command
Purpose
switchport priority extend
{cos value | trust}
Set the priority of data traffic received from the Cisco IP Phone access port:
•
cos value—Configure the phone to override the priority received from the
PC or the attached device with the specified CoS value. The value is a
number from 0 to 7, with 7 as the highest priority. The default priority is
cos 0.
•
trust—Configure the phone access port to trust the priority received from
the PC or the attached device.
Step 4
end
Return to privileged EXEC mode.
Step 5
show interfaces interface-id
switchport
Verify your entries.
Step 6
copy running-config
startup-config
(Optional) Save your entries in the configuration file.
This example shows how to configure a port connected to a Cisco IP Phone to not change the priority of
frames received from the PC or the attached device:
Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# interface gigabitethernet0/1
Switch(config-if)# switchport priority extend trust
Switch(config-if)# end
To return the port to its default setting, use the no switchport priority extend interface configuration
command.
Displaying Voice VLAN
To display voice VLAN configuration for an interface, use the show interfaces interface-id switchport
privileged EXEC command.
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Displaying Voice VLAN
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15
Configuring Private VLANs
This chapter describes how to configure private VLANs on the Cisco Blade Switch.
Note
For complete syntax and usage information for the commands used in this chapter, see the command
reference for this release.
The chapter consists of these sections:
Note
•
Understanding Private VLANs, page 15-1
•
Configuring Private VLANs, page 15-5
•
Monitoring Private VLANs, page 15-14
When you configure private VLANs, the switch must be in VTP transparent mode. See Chapter 13,
“Configuring VTP.”
Understanding Private VLANs
The private-VLAN feature addresses two problems that service providers face when using VLANs:
•
Scalability: The switch supports up to 1005 active VLANs. If a service provider assigns one VLAN
per customer, this limits the numbers of customers the service provider can support.
•
To enable IP routing, each VLAN is assigned a subnet address space or a block of addresses, which
can result in wasting the unused IP addresses, and cause IP address management problems.
Using private VLANs addresses the scalability problem and provides IP address management benefits
for service providers and Layer 2 security for customers.
Private VLANs partition a regular VLAN domain into subdomains and can have multiple VLAN
pairs—one for each subdomain. A subdomain is represented by a primary VLAN and a secondary
VLAN.
All VLAN pairs in a private VLAN share the same primary VLAN. The secondary VLAN ID
differentiates one subdomain from another. See Figure 15-1.
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Configuring Private VLANs
Understanding Private VLANs
Figure 15-1
Private-VLAN Domain
Private
VLAN
domain
Subdomain
Subdomain
Secondary
isolated VLAN
116083
Secondary
community VLAN
Primary
VLAN
There are two types of secondary VLANs:
•
Isolated VLANs—Ports within an isolated VLAN cannot communicate with each other at the
Layer 2 level.
•
Community VLANs—Ports within a community VLAN can communicate with each other but
cannot communicate with ports in other communities at the Layer 2 level.
Private VLANs provide Layer 2 isolation between ports within the same private VLAN. Private-VLAN
ports are access ports that are one of these types:
Note
•
Promiscuous—A promiscuous port belongs to the primary VLAN and can communicate with all
interfaces, including the community and isolated host ports that belong to the secondary VLANs
associated with the primary VLAN.
•
Isolated—An isolated port is a host port that belongs to an isolated secondary VLAN. It has
complete Layer 2 separation from other ports within the same private VLAN, except for the
promiscuous ports. Private VLANs block all traffic to isolated ports except traffic from promiscuous
ports. Traffic received from an isolated port is forwarded only to promiscuous ports.
•
Community—A community port is a host port that belongs to a community secondary VLAN.
Community ports communicate with other ports in the same community VLAN and with
promiscuous ports. These interfaces are isolated at Layer 2 from all other interfaces in other
communities and from isolated ports within their private VLAN.
Trunk ports carry traffic from regular VLANs and also from primary, isolated, and community VLANs.
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Understanding Private VLANs
Primary and secondary VLANs have these characteristics:
•
Primary VLAN—A private VLAN has only one primary VLAN. Every port in a private VLAN is a
member of the primary VLAN. The primary VLAN carries unidirectional traffic downstream from
the promiscuous ports to the (isolated and community) host ports and to other promiscuous ports.
•
Isolated VLAN—A private VLAN has only one isolated VLAN. An isolated VLAN is a secondary
VLAN that carries unidirectional traffic upstream from the hosts toward the promiscuous ports and
the gateway.
•
Community VLAN—A community VLAN is a secondary VLAN that carries upstream traffic from
the community ports to the promiscuous port gateways and to other host ports in the same
community. You can configure multiple community VLANs in a private VLAN.
A promiscuous port can serve only one primary VLAN, one isolated VLAN, and multiple community
VLANs. Layer 3 gateways are typically connected to the switch through a promiscuous port. With a
promiscuous port, you can connect a wide range of devices as access points to a private VLAN. For
example, you can use a promiscuous port to monitor or back up all the private-VLAN servers from an
administration workstation.
In a switched environment, you can assign an individual private VLAN and an associated IP subnet to
each individual or common group of end stations. The end stations need to communicate with only a
default gateway to communicate outside the private VLAN.
You can use private VLANs to control access to end stations in these ways:
•
Configure selected interfaces connected to end stations as isolated ports to prevent any
communication at Layer 2. For example, if the end stations are servers, this configuration prevents
Layer 2 communication between the servers.
•
Configure interfaces connected to default gateways and selected end stations (for example, backup
servers) as promiscuous ports to allow all end stations access to a default gateway.
You can extend private VLANs across multiple devices by trunking the primary, isolated, and
community VLANs to other devices that support private VLANs. To maintain the security of your
private-VLAN configuration and to avoid other use of the VLANs configured as private VLANs,
configure private VLANs on all intermediate devices, including devices that have no private-VLAN
ports.
IP Addressing Scheme with Private VLANs
Assigning a separate VLAN to each customer creates an inefficient IP addressing scheme:
•
Assigning a block of addresses to a customer VLAN can result in unused IP addresses.
•
If the number of devices in the VLAN increases, the number of assigned address might not be large
enough to accommodate them.
These problems are reduced by using private VLANs, where all members in the private VLAN share a
common address space, which is allocated to the primary VLAN. Hosts are connected to secondary
VLANs, and the DHCP server assigns them IP addresses from the block of addresses allocated to the
primary VLAN. Subsequent IP addresses can be assigned to customer devices in different secondary
VLANs, but in the same primary VLAN. When new devices are added, the DHCP server assigns them
the next available address from a large pool of subnet addresses.
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Understanding Private VLANs
Private VLANs across Multiple Switches
As with regular VLANs, private VLANs can span multiple switches. A trunk port carries the primary
VLAN and secondary VLANs to a neighboring switch. The trunk port treats the private VLAN as any
other VLAN. A feature of private VLANs across multiple switches is that traffic from an isolated port
in switch A does not reach an isolated port on Switch B. See Figure 15-2.
Figure 15-2
Private VLANs across Switches
Trunk ports
VLAN 100
VLAN 100
Switch B
VLAN 201
VLAN 202
VLAN 201
VLAN 202
Carries VLAN 100,
201, and 202 traffic
116084
Switch A
VLAN 100 = Primary VLAN
VLAN 201 = Secondary isolated VLAN
VLAN 202 = Secondary community VLAN
Because VTP does not support private VLANs, you must manually configure private VLANs on all
switches in the Layer 2 network. If you do not configure the primary and secondary VLAN association
in some switches in the network, the Layer 2 databases in these switches are not merged. This can result
in unnecessary flooding of private-VLAN traffic on those switches.
Note
When configuring private VLANs on the switch, always use the default Switch Database Management
(SDM) template to balance system resources between unicast routes and Layer 2 entries. If another SDM
template is configured, use the sdm prefer default global configuration command to set the default
template. See Chapter 6, “Configuring SDM Templates.”
Private-VLAN Interaction with Other Features
Private VLANs have specific interaction with some other features, described in these sections:
•
Private VLANs and Unicast, Broadcast, and Multicast Traffic, page 15-5
•
Private VLANs and SVIs, page 15-5
You should also see the “Secondary and Primary VLAN Configuration” section on page 15-7 under the
“Private-VLAN Configuration Guidelines” section.
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Private VLANs and Unicast, Broadcast, and Multicast Traffic
In regular VLANs, devices in the same VLAN can communicate with each other at the Layer 2 level, but
devices connected to interfaces in different VLANs must communicate at the Layer 3 level. In private
VLANs, the promiscuous ports are members of the primary VLAN, while the host ports belong to
secondary VLANs. Because the secondary VLAN is associated to the primary VLAN, members of the
these VLANs can communicate with each other at the Layer 2 level.
In a regular VLAN, broadcasts are forwarded to all ports in that VLAN. Private VLAN broadcast
forwarding depends on the port sending the broadcast:
•
An isolated port sends a broadcast only to the promiscuous ports or trunk ports.
•
A community port sends a broadcast to all promiscuous ports, trunk ports, and ports in the same
community VLAN.
•
A promiscuous port sends a broadcast to all ports in the private VLAN (other promiscuous ports,
trunk ports, isolated ports, and community ports).
Multicast traffic is routed or bridged across private-VLAN boundaries and within a single community
VLAN. Multicast traffic is not forwarded between ports in the same isolated VLAN or between ports in
different secondary VLANs.
Private VLANs and SVIs
In a Layer 3 switch, a switch virtual interface (SVI) represents the Layer 3 interface of a VLAN. Layer 3
devices communicate with a private VLAN only through the primary VLAN and not through secondary
VLANs. Configure Layer 3 VLAN interfaces (SVIs) only for primary VLANs. You cannot configure
Layer 3 VLAN interfaces for secondary VLANs. SVIs for secondary VLANs are inactive while the
VLAN is configured as a secondary VLAN.
•
If you try to configure a VLAN with an active SVI as a secondary VLAN, the configuration is not
allowed until you disable the SVI.
•
If you try to create an SVI on a VLAN that is configured as a secondary VLAN and the secondary
VLAN is already mapped at Layer 3, the SVI is not created, and an error is returned. If the SVI is
not mapped at Layer 3, the SVI is created, but it is automatically shut down.
When the primary VLAN is associated with and mapped to the secondary VLAN, any configuration on
the primary VLAN is propagated to the secondary VLAN SVIs. For example, if you assign an IP subnet
to the primary VLAN SVI, this subnet is the IP subnet address of the entire private VLAN.
Configuring Private VLANs
These sections contain this configuration information:
•
Tasks for Configuring Private VLANs, page 15-6
•
Default Private-VLAN Configuration, page 15-6
•
Private-VLAN Configuration Guidelines, page 15-6
•
Configuring and Associating VLANs in a Private VLAN, page 15-9
•
Configuring a Layer 2 Interface as a Private-VLAN Host Port, page 15-11
•
Configuring a Layer 2 Interface as a Private-VLAN Promiscuous Port, page 15-12
•
Mapping Secondary VLANs to a Primary VLAN Layer 3 VLAN Interface, page 15-13
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Configuring Private VLANs
Tasks for Configuring Private VLANs
To configure a private VLAN, perform these steps:
Step 1
Set VTP mode to transparent.
Step 2
Create the primary and secondary VLANs and associate them. See the “Configuring and Associating
VLANs in a Private VLAN” section on page 15-9.
Note
If the VLAN is not created already, the private-VLAN configuration process creates it.
Step 3
Configure interfaces to be isolated or community host ports, and assign VLAN membership to the host
port. See the “Configuring a Layer 2 Interface as a Private-VLAN Host Port” section on page 15-11.
Step 4
Configure interfaces as promiscuous ports, and map the promiscuous ports to the primary-secondary
VLAN pair. See the “Configuring a Layer 2 Interface as a Private-VLAN Promiscuous Port” section on
page 15-12.
Step 5
If inter-VLAN routing will be used, configure the primary SVI, and map secondary VLANs to the
primary. See the “Mapping Secondary VLANs to a Primary VLAN Layer 3 VLAN Interface” section on
page 15-13.
Step 6
Verify private-VLAN configuration.
Default Private-VLAN Configuration
No private VLANs are configured.
Private-VLAN Configuration Guidelines
Guidelines for configuring private VLANs fall into these categories:
•
Secondary and Primary VLAN Configuration, page 15-7
•
Private-VLAN Port Configuration, page 15-8
•
Limitations with Other Features, page 15-8
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Configuring Private VLANs
Secondary and Primary VLAN Configuration
Follow these guidelines when configuring private VLANs:
•
If the switch is running VTP version 1 or 2, you must set VTP to transparent mode. After you
configure a private VLAN, you should not change the VTP mode to client or server. For information
about VTP, see Chapter 13, “Configuring VTP.” VTP version 3 supports private VLANs in all
modes.
•
With VTP version 1 or 2, after you have configured private VLANs, use the copy running-config
startup config privileged EXEC command to save the VTP transparent mode configuration and
private-VLAN configuration in the switch startup configuration file. Otherwise, if the switch resets,
it defaults to VTP server mode, which does not support private VLANs. VTP version 3 does support
private VLANs.
•
VTP version 1 and 2 do not propagate private-VLAN configuration. You must configure private
VLANs on each device where you want private-VLAN ports unless the devices are running VTP
version 3.
•
You cannot configure VLAN 1 or VLANs 1002 to 1005 as primary or secondary VLANs. Extended
VLANs (VLAN IDs 1006 to 4094) can belong to private VLANs
•
A primary VLAN can have one isolated VLAN and multiple community VLANs associated with it.
An isolated or community VLAN can have only one primary VLAN associated with it.
•
Although a private VLAN contains more than one VLAN, only one Spanning Tree Protocol (STP)
instance runs for the entire private VLAN. When a secondary VLAN is associated with the primary
VLAN, the STP parameters of the primary VLAN are propagated to the secondary VLAN.
•
You can enable DHCP snooping on private VLANs. When you enable DHCP snooping on the
primary VLAN, it is propagated to the secondary VLANs. If you configure DHCP on a secondary
VLAN, the configuration does not take effect if the primary VLAN is already configured.
•
When you enable IP source guard on private-VLAN ports, you must enable DHCP snooping on the
primary VLAN.
•
We recommend that you prune the private VLANs from the trunks on devices that carry no traffic
in the private VLANs.
•
You can apply different quality of service (QoS) configurations to primary, isolated, and community
VLANs.
•
Sticky ARP
– Sticky ARP entries are those learned on SVIs and Layer 3 interfaces. They entries do not age
out.
– The ip sticky-arp global configuration command is supported only on SVIs belonging to
private VLANs.
– The ip sticky-arp interface configuration command is only supported on
Layer 3 interfaces
SVIs belonging to normal VLANs
SVIs belonging to private VLANs
For more information about using the ip sticky-arp global configuration and the ip sticky-arp
interface configuration commands, see the command reference for this release.
•
You can configure VLAN maps on primary and secondary VLANs (see the “Configuring VLAN
Maps” section on page 33-29). However, we recommend that you configure the same VLAN maps
on private-VLAN primary and secondary VLANs.
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Configuring Private VLANs
•
When a frame is Layer-2 forwarded within a private VLAN, the same VLAN map is applied at the
ingress side and at the egress side. When a frame is routed from inside a private VLAN to an external
port, the private-VLAN map is applied at the ingress side.
– For frames going upstream from a host port to a promiscuous port, the VLAN map configured
on the secondary VLAN is applied.
– For frames going downstream from a promiscuous port to a host port, the VLAN map
configured on the primary VLAN is applied.
To filter out specific IP traffic for a private VLAN, you should apply the VLAN map to both the
primary and secondary VLANs.
•
You can apply router ACLs only on the primary-VLAN SVIs. The ACL is applied to both primary
and secondary VLAN Layer 3 traffic.
•
Although private VLANs provide host isolation at Layer 2, hosts can communicate with each other
at Layer 3.
•
Private VLANs support these Switched Port Analyzer (SPAN) features:
– You can configure a private-VLAN port as a SPAN source port.
– You can use VLAN-based SPAN (VSPAN) on primary, isolated, and community VLANs or use
SPAN on only one VLAN to separately monitor egress or ingress traffic.
Private-VLAN Port Configuration
Follow these guidelines when configuring private-VLAN ports:
•
Use only the private-VLAN configuration commands to assign ports to primary, isolated, or
community VLANs. Layer 2 access ports assigned to the VLANs that you configure as primary,
isolated, or community VLANs are inactive while the VLAN is part of the private-VLAN
configuration. Layer 2 trunk interfaces remain in the STP forwarding state.
•
Do not configure ports that belong to a PAgP or LACP EtherChannel as private-VLAN ports. While
a port is part of the private-VLAN configuration, any EtherChannel configuration for it is inactive.
•
Enable Port Fast and BPDU guard on isolated and community host ports to prevent STP loops due
to misconfigurations and to speed up STP convergence (see Chapter 19, “Configuring Optional
Spanning-Tree Features”). When enabled, STP applies the BPDU guard feature to all Port
Fast-configured Layer 2 LAN ports. Do not enable Port Fast and BPDU guard on promiscuous ports.
•
If you delete a VLAN used in the private-VLAN configuration, the private-VLAN ports associated
with the VLAN become inactive.
•
Private-VLAN ports can be on different network devices if the devices are trunk-connected and the
primary and secondary VLANs have not been removed from the trunk.
Limitations with Other Features
When configuring private VLANs, remember these limitations with other features:
Note
In some cases, the configuration is accepted with no error messages, but the commands have no effect.
•
When IGMP snooping is enabled on the switch (the default), the switch supports no more than 20
private-VLAN domains.
•
Do not configure a remote SPAN (RSPAN) VLAN as a private-VLAN primary or secondary VLAN.
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For more information about SPAN, see Chapter 28, “Configuring SPAN and RSPAN.”
•
Do not configure private-VLAN ports on interfaces configured for these other features:
– dynamic-access port VLAN membership
– Dynamic Trunking Protocol (DTP)
– Port Aggregation Protocol (PAgP)
– Link Aggregation Control Protocol (LACP)
– Multicast VLAN Registration (MVR)
– voice VLAN
•
You can configure IEEE 802.1x port-based authentication on a private-VLAN port, but do not
configure 802.1x with port security, voice VLAN, or per-user ACL on private-VLAN ports.
•
A private-VLAN host or promiscuous port cannot be a SPAN destination port. If you configure a
SPAN destination port as a private-VLAN port, the port becomes inactive.
•
If you configure a static MAC address on a promiscuous port in the primary VLAN, you must add
the same static address to all associated secondary VLANs. If you configure a static MAC address
on a host port in a secondary VLAN, you must add the same static MAC address to the associated
primary VLAN. When you delete a static MAC address from a private-VLAN port, you must remove
all instances of the configured MAC address from the private VLAN.
Note
•
Dynamic MAC addresses learned in one VLAN of a private VLAN are replicated in the
associated VLANs. For example, a MAC address learned in a secondary VLAN is replicated
in the primary VLAN. When the original dynamic MAC address is deleted or aged out, the
replicated addresses are removed from the MAC address table.
Configure Layer 3 VLAN interfaces (SVIs) only for primary VLANs.
Configuring and Associating VLANs in a Private VLAN
Beginning in privileged EXEC mode, follow these steps to configure a private VLAN:
Note
The private-vlan commands do not take effect until you exit VLAN configuration mode.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
vtp mode transparent
Set VTP mode to transparent (disable VTP).
Step 3
vlan vlan-id
Enter VLAN configuration mode and designate or create a VLAN that
will be the primary VLAN. The VLAN ID range is 2 to 1001 and 1006
to 4094.
Step 4
private-vlan primary
Designate the VLAN as the primary VLAN.
Step 5
exit
Return to global configuration mode.
Step 6
vlan vlan-id
(Optional) Enter VLAN configuration mode and designate or create a
VLAN that will be an isolated VLAN. The VLAN ID range is 2 to 1001
and 1006 to 4094.
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Configuring Private VLANs
Command
Purpose
Step 7
private-vlan isolated
Designate the VLAN as an isolated VLAN.
Step 8
exit
Return to global configuration mode.
Step 9
vlan vlan-id
(Optional) Enter VLAN configuration mode and designate or create a
VLAN that will be a community VLAN. The VLAN ID range is 2 to
1001 and 1006 to 4094.
Step 10 private-vlan community
Designate the VLAN as a community VLAN.
Step 11 exit
Return to global configuration mode.
Step 12 vlan vlan-id
Enter VLAN configuration mode for the primary VLAN designated in
Step 2.
Step 13 private-vlan association [add | remove]
Associate the secondary VLANs with the primary VLAN.
secondary_vlan_list
Step 14 end
Return to privileged EXEC mode.
Step 15 show vlan private-vlan [type]
Verify the configuration.
or
show interfaces status
Step 16 copy running-config startup config
Save your entries in the switch startup configuration file. To save the
private-VLAN configuration, you need to save the VTP transparent
mode configuration and private-VLAN configuration in the switch
startup configuration file. Otherwise, if the switch resets, it defaults to
VTP server mode, which does not support private VLANs.
When you associate secondary VLANs with a primary VLAN, note this syntax information:
•
The secondary_vlan_list parameter cannot contain spaces. It can contain multiple comma-separated
items. Each item can be a single private-VLAN ID or a hyphenated range of private-VLAN IDs.
•
The secondary_vlan_list parameter can contain multiple community VLAN IDs but only one
isolated VLAN ID.
•
Enter a secondary_vlan_list, or use the add keyword with a secondary_vlan_list to associate
secondary VLANs with a primary VLAN.
•
Use the remove keyword with a secondary_vlan_list to clear the association between secondary
VLANs and a primary VLAN.
•
The command does not take effect until you exit VLAN configuration mode.
This example shows how to configure VLAN 20 as a primary VLAN, VLAN 501 as an isolated VLAN,
and VLANs 502 and 503 as community VLANs, to associate them in a private VLAN, and to verify the
configuration:
Switch# configure terminal
Switch(config)# vlan 20
Switch(config-vlan)# private-vlan
Switch(config-vlan)# exit
Switch(config)# vlan 501
Switch(config-vlan)# private-vlan
Switch(config-vlan)# exit
Switch(config)# vlan 502
Switch(config-vlan)# private-vlan
Switch(config-vlan)# exit
Switch(config)# vlan 503
Switch(config-vlan)# private-vlan
primary
isolated
community
community
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Switch(config-vlan)# exit
Switch(config)# vlan 20
Switch(config-vlan)# private-vlan association 501-503
Switch(config-vlan)# end
Switch(config)# show vlan private vlan
Primary Secondary Type
Ports
------- --------- ----------------- -----------------------------------------20
501
isolated
20
502
community
20
503
community
20
504
non-operational
Configuring a Layer 2 Interface as a Private-VLAN Host Port
Beginning in privileged EXEC mode, follow these steps to configure a Layer 2 interface as a
private-VLAN host port and to associate it with primary and secondary VLANs:
Note
Isolated and community VLANs are both secondary VLANs.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Enter interface configuration mode for the Layer 2 interface to be
configured.
Step 3
switchport mode private-vlan host
Configure the Layer 2 port as a private-VLAN host port.
Step 4
switchport private-vlan host-association
primary_vlan_id secondary_vlan_id
Associate the Layer 2 port with a private VLAN.
Step 5
end
Return to privileged EXEC mode.
Step 6
show interfaces [interface-id] switchport
Verify the configuration.
Step 7
copy running-config startup config
(Optional) Save your entries in the switch startup configuration file.
This example shows how to configure an interface as a private-VLAN host port, associate it with a
private-VLAN pair, and verify the configuration:
Switch# configure terminal
Switch(config)# interface gigabitethernet0/22
Switch(config-if)# switchport mode private-vlan host
Switch(config-if)# switchport private-vlan host-association 20 25
Switch(config-if)# end
Switch# show interfaces gigabitethernet0/22 switchport
Name: Gi1/0/22
Switchport: Enabled
Administrative Mode: private-vlan host
Operational Mode: private-vlan host
Administrative Trunking Encapsulation: negotiate
Operational Trunking Encapsulation: native
Negotiation of Trunking: Off
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: 20 (VLAN0020) 25 (VLAN0025)
Administrative private-vlan mapping: none
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Configuring Private VLANs
Administrative private-vlan
Administrative private-vlan
Administrative private-vlan
Administrative private-vlan
Administrative private-vlan
Operational private-vlan:
20 (VLAN0020) 25 (VLAN0025)
trunk
trunk
trunk
trunk
trunk
native VLAN: none
Native VLAN tagging: enabled
encapsulation: dot1q
normal VLANs: none
private VLANs: none
<output truncated>
Configuring a Layer 2 Interface as a Private-VLAN Promiscuous Port
Beginning in privileged EXEC mode, follow these steps to configure a Layer 2 interface as a
private-VLAN promiscuous port and map it to primary and secondary VLANs:
Note
Isolated and community VLANs are both secondary VLANs.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Enter interface configuration mode for the Layer 2
interface to be configured.
Step 3
switchport mode private-vlan promiscuous
Configure the Layer 2 port as a private-VLAN
promiscuous port.
Step 4
switchport private-vlan mapping primary_vlan_id
{add | remove} secondary_vlan_list
Map the private-VLAN promiscuous port to a primary
VLAN and to selected secondary VLANs.
Step 5
end
Return to privileged EXEC mode.
Step 6
show interfaces [interface-id] switchport
Verify the configuration.
Step 7
copy running-config startup config
(Optional) Save your entries in the switch startup
configuration file.
When you configure a Layer 2 interface as a private-VLAN promiscuous port, note this syntax
information:
•
The secondary_vlan_list parameter cannot contain spaces. It can contain multiple comma-separated
items. Each item can be a single private-VLAN ID or a hyphenated range of private-VLAN IDs.
•
Enter a secondary_vlan_list, or use the add keyword with a secondary_vlan_list to map the
secondary VLANs to the private-VLAN promiscuous port.
•
Use the remove keyword with a secondary_vlan_list to clear the mapping between secondary
VLANs and the private-VLAN promiscuous port.
This example shows how to configure an interface as a private-VLAN promiscuous port and map it to a
private VLAN. The interface is a member of primary VLAN 20 and secondary VLANs 501 to 503 are
mapped to it.
Switch# configure terminal
Switch(config)# interface gigabitethernet0/2
Switch(config-if)# switchport mode private-vlan promiscuous
Switch(config-if)# switchport private-vlan mapping 20 add 501-503
Switch(config-if)# end
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Configuring Private VLANs
Use the show vlan private-vlan or the show interface status privileged EXEC command to display
primary and secondary VLANs and private-VLAN ports on the switch.
Mapping Secondary VLANs to a Primary VLAN Layer 3 VLAN Interface
If you use the private VLAN for inter-VLAN routing, you must configure an SVI for the primary VLAN
and map secondary VLANs to the SVI.
Note
Isolated and community VLANs are both secondary VLANs.
Beginning in privileged EXEC mode, follow these steps to map secondary VLANs to the SVI of a
primary VLAN to allow Layer 3 switching of private-VLAN traffic:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface vlan primary_vlan_id
Enter interface configuration mode for the primary
VLAN, and configure the VLAN as an SVI. The VLAN
ID range is 2 to 1001 and 1006 to 4094.
Step 3
private-vlan mapping [add | remove]
secondary_vlan_list
Map the secondary VLANs to the Layer 3 VLAN
interface of a primary VLAN to allow Layer 3 switching
of private-VLAN ingress traffic.
end
Return to privileged EXEC mode.
Step 5
show interface private-vlan mapping
Verify the configuration.
Step 6
copy running-config startup config
(Optional) Save your entries in the switch startup
configuration file.
Step 4
Note
The private-vlan mapping interface configuration command only affects private-VLAN traffic that is
Layer 3 switched.
When you map secondary VLANs to the Layer 3 VLAN interface of a primary VLAN, note this syntax
information:
•
The secondary_vlan_list parameter cannot contain spaces. It can contain multiple comma-separated
items. Each item can be a single private-VLAN ID or a hyphenated range of private-VLAN IDs.
•
Enter a secondary_vlan_list, or use the add keyword with a secondary_vlan_list to map the
secondary VLANs to the primary VLAN.
•
Use the remove keyword with a secondary_vlan_list to clear the mapping between secondary
VLANs and the primary VLAN.
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Configuring Private VLANs
Monitoring Private VLANs
This example shows how to map the interfaces of VLANs 501and 502 to primary VLAN 10, which
permits routing of secondary VLAN ingress traffic from private VLANs 501 to 502:
Switch# configure terminal
Switch(config)# interface vlan 10
Switch(config-if)# private-vlan mapping 501-502
Switch(config-if)# end
Switch# show interfaces private-vlan mapping
Interface Secondary VLAN Type
--------- -------------- ----------------vlan10
501
isolated
vlan10
502
community
Monitoring Private VLANs
Table 15-1 shows the privileged EXEC commands for monitoring private-VLAN activity.
Table 15-1
Private VLAN Monitoring Commands
Command
Purpose
show interfaces status
Displays the status of interfaces, including the VLANs to which they belongs.
show vlan private-vlan [type]
Display the private-VLAN information for the switch.
show interface switchport
Display private-VLAN configuration on interfaces.
show interface private-vlan mapping
Display information about the private-VLAN mapping for VLAN SVIs.
This is an example of the output from the show vlan private-vlan command:
Switch(config)# show vlan private-vlan
Primary Secondary Type
Ports
------- --------- ----------------- -----------------------------------------10
501
isolated
Gi0/1, Gi0/2, Gi0/3
10
502
community
Gi0/1, Gi0/2, Gi0/4
10
503
non-operational
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16
Configuring IEEE 802.1Q and Layer 2 Protocol
Tunneling
Virtual private networks (VPNs) provide enterprise-scale connectivity on a shared infrastructure, often
Ethernet-based, with the same security, prioritization, reliability, and manageability requirements of
private networks. Tunneling is a feature designed for service providers who carry traffic of multiple
customers across their networks and are required to maintain the VLAN and Layer 2 protocol
configurations of each customer without impacting the traffic of other customers. The switch supports
IEEE 802.1Q tunneling and Layer 2 protocol tunneling.
Note
For complete syntax and usage information for the commands used in this chapter, see the command
reference for this release.
This chapter contains these sections:
•
Understanding IEEE 802.1Q Tunneling, page 16-1
•
Configuring IEEE 802.1Q Tunneling, page 16-4
•
Understanding Layer 2 Protocol Tunneling, page 16-7
•
Configuring Layer 2 Protocol Tunneling, page 16-10
•
Monitoring and Maintaining Tunneling Status, page 16-18
Understanding IEEE 802.1Q Tunneling
Business customers of service providers often have specific requirements for VLAN IDs and the number
of VLANs to be supported. The VLAN ranges required by different customers in the same
service-provider network might overlap, and traffic of customers through the infrastructure might be
mixed. Assigning a unique range of VLAN IDs to each customer would restrict customer configurations
and could easily exceed the VLAN limit (4096) of the IEEE 802.1Q specification.
Using the IEEE 802.1Q tunneling feature, service providers can use a single VLAN to support customers
who have multiple VLANs. Customer VLAN IDs are preserved, and traffic from different customers is
segregated within the service-provider network, even when they appear to be in the same VLAN. Using
IEEE 802.1Q tunneling expands VLAN space by using a VLAN-in-VLAN hierarchy and retagging the
tagged packets. A port configured to support IEEE 802.1Q tunneling is called a tunnel port. When you
configure tunneling, you assign a tunnel port to a VLAN ID that is dedicated to tunneling. Each customer
requires a separate service-provider VLAN ID, but that VLAN ID supports all of the customer’s VLANs.
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Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling
Understanding IEEE 802.1Q Tunneling
Customer traffic tagged in the normal way with appropriate VLAN IDs comes from an IEEE 802.1Q
trunk port on the customer device and into a tunnel port on the service-provider edge switch. The link
between the customer device and the edge switch is asymmetric because one end is configured as an
IEEE 802.1Q trunk port, and the other end is configured as a tunnel port. You assign the tunnel port
interface to an access VLAN ID that is unique to each customer. See Figure 16-1.
Figure 16-1
IEEE 802.1Q Tunnel Ports in a Service-Provider Network
Customer A
VLANs 1 to 100
Customer A
VLANs 1 to 100
802.1Q
802.1Qtrunk
trunkport
port
Service
provider
802.1Q
802.1Q trunk
trunk port
port
Tunnel port
VLAN 30
Tunnel port
VLAN 30
802.1Q
802.1Qtrunk
trunkport
port
Tunnel port
VLAN 30
Trunk
ports
Trunk
ports
Tunnel port
VLAN 40
Tunnel port
VLAN 40
802.1Q
802.1Qtrunk
trunkport
port
74016
802.1Q trunk port
Customer B
VLANs 1 to 200
Trunk
Asymmetric link
Customer B
VLANs 1 to 200
Packets coming from the customer trunk port into the tunnel port on the service-provider edge switch
are normally IEEE 802.1Q-tagged with the appropriate VLAN ID. The the tagged packets remain intact
inside the switch and when they exit the trunk port into the service-provider network, they are
encapsulated with another layer of an IEEE 802.1Q tag (called the metro tag) that contains the VLAN
ID that is unique to the customer. The original customer IEEE 802.1Q tag is preserved in the
encapsulated packet. Therefore, packets entering the service-provider network are double-tagged, with
the outer (metro) tag containing the customer’s access VLAN ID, and the inner VLAN ID being that of
the incoming traffic.
When the double-tagged packet enters another trunk port in a service-provider core switch, the outer tag
is stripped as the switch processes the packet. When the packet exits another trunk port on the same core
switch, the same metro tag is again added to the packet. Figure 16-2 shows the tag structures of the
double-tagged packets.
Note
Remove the Layer 2 protocol configuration from a trunk port because incoming encapsulated packets
change that trunk port to error disabled. The outgoing encapsulated VTP (CDP and STP) packets are
dropped on that trunk.
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Understanding IEEE 802.1Q Tunneling
Original (Normal), IEEE 802.1Q, and Double-Tagged Ethernet Packet Formats
Source
address
Destination
Length/
address
EtherType
DA
SA
Len/Etype
DA
SA
Etype
DA
SA
Etype
Frame Check
Sequence
Data
Tag
Tag
FCS
Len/Etype
Etype
Tag
Original Ethernet frame
Data
Len/Etype
FCS
IEE 802.1Q frame from
customer network
Data
FCS
74072
Figure 16-2
Double-tagged
frame in service
provider
infrastructure
When the packet enters the trunk port of the service-provider egress switch, the outer tag is again
stripped as the switch internally processes the packet. However, the metro tag is not added when the
packet is sent out the tunnel port on the edge switch into the customer network. The packet is sent as a
normal IEEE 802.1Q-tagged frame to preserve the original VLAN numbers in the customer network.
In Figure 16-1, Customer A was assigned VLAN 30, and Customer B was assigned VLAN 40. Packets
entering the edge switch tunnel ports with IEEE 802.1Q tags are double-tagged when they enter the
service-provider network, with the outer tag containing VLAN ID 30 or 40, appropriately, and the inner
tag containing the original VLAN number, for example, VLAN 100. Even if both Customers A and B
have VLAN 100 in their networks, the traffic remains segregated within the service-provider network
because the outer tag is different. Each customer controls its own VLAN numbering space, which is
independent of the VLAN numbering space used by other customers and the VLAN numbering space
used by the service-provider network.
At the outbound tunnel port, the original VLAN numbers on the customer’s network are recovered. It is
possible to have multiple levels of tunneling and tagging, but the switch supports only one level in this
release.
If traffic coming from a customer network is not tagged (native VLAN frames), these packets are bridged
or routed as normal packets. All packets entering the service-provider network through a tunnel port on
an edge switch are treated as untagged packets, whether they are untagged or already tagged with IEEE
802.1Q headers. The packets are encapsulated with the metro tag VLAN ID (set to the access VLAN of
the tunnel port) when they are sent through the service-provider network on an IEEE 802.1Q trunk port.
The priority field on the metro tag is set to the interface class of service (CoS) priority configured on the
tunnel port. (The default is zero if none is configured.)
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Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling
Configuring IEEE 802.1Q Tunneling
Configuring IEEE 802.1Q Tunneling
These sections contain this configuration information:
•
Default IEEE 802.1Q Tunneling Configuration, page 16-4
•
IEEE 802.1Q Tunneling Configuration Guidelines, page 16-4
•
IEEE 802.1Q Tunneling and Other Features, page 16-6
•
Configuring an IEEE 802.1Q Tunneling Port, page 16-6
Default IEEE 802.1Q Tunneling Configuration
By default, IEEE 802.1Q tunneling is disabled because the default switchport mode is dynamic auto.
Tagging of IEEE 802.1Q native VLAN packets on all IEEE 802.1Q trunk ports is also disabled.
IEEE 802.1Q Tunneling Configuration Guidelines
When you configure IEEE 802.1Q tunneling, you should always use an asymmetrical link between the
customer device and the edge switch, with the customer device port configured as an IEEE 802.1Q trunk
port and the edge switch port configured as a tunnel port.
Assign tunnel ports only to VLANs that are used for tunneling.
Configuration requirements for native VLANs and for and maximum transmission units (MTUs) are
explained in these next sections.
Native VLANs
When configuring IEEE 802.1Q tunneling on an edge switch, you must use IEEE 802.1Q trunk ports for
sending packets into the service-provider network. However, packets going through the core of the
service-provider network can be carried through IEEE 802.1Q trunks, ISL trunks, or nontrunking links.
When IEEE 802.1Q trunks are used in these core switches, the native VLANs of the IEEE 802.1Q trunks
must not match any native VLAN of the nontrunking (tunneling) port on the same switch because traffic
on the native VLAN would not be tagged on the IEEE 802.1Q sending trunk port.
See Figure 16-3. VLAN 40 is configured as the native VLAN for the IEEE 802.1Q trunk port from
Customer X at the ingress edge switch in the service-provider network (Switch B). Switch A of
Customer X sends a tagged packet on VLAN 30 to the ingress tunnel port of Switch B in the
service-provider network, which belongs to access VLAN 40. Because the access VLAN of the tunnel
port (VLAN 40) is the same as the native VLAN of the edge-switch trunk port (VLAN 40), the metro
tag is not added to tagged packets received from the tunnel port. The packet carries only the VLAN 30
tag through the service-provider network to the trunk port of the egress-edge switch (Switch C) and is
misdirected through the egress switch tunnel port to Customer Y.
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Configuring IEEE 802.1Q Tunneling
These are some ways to solve this problem:
•
Use ISL trunks between core switches in the service-provider network. Although customer
interfaces connected to edge switches must be IEEE 802.1Q trunks, we recommend using ISL trunks
for connecting switches in the core layer.
•
Use the vlan dot1q tag native global configuration command to configure the edge switch so that
all packets going out an IEEE 802.1Q trunk, including the native VLAN, are tagged. If the switch
is configured to tag native VLAN packets on all IEEE 802.1Q trunks, the switch accepts untagged
packets, but sends only tagged packets.
•
Ensure that the native VLAN ID on the edge-switch trunk port is not within the customer VLAN
range. For example, if the trunk port carries traffic of VLANs 100 to 200, assign the native VLAN
a number outside that range.
Figure 16-3
Potential Problem with IEEE 802.1Q Tunneling and Native VLANs
Tag not added
for VLAN 40
Tag
removed
Switch D
Customer X
VLANs 30-40
Native VLAN 40
Service
provider
Tunnel port
Packet tagged
for VLAN 30
Switch A
Customer X
Q
Tunnel port
Access VLAN 40
VLANs 5-50
Native
VLAN 40
Switch C VLAN 40
Q
Tunnel port
Access VLAN 30
802.1Q
trunk port
VLANs 30-40
Native VLAN 40
Trunk
Asymmetric link
Correct path for traffic
Incorrect path for traffic due to
misconfiguration of native VLAN
by sending port on Switch B
Q = 802.1Q trunk ports
Switch E
Customer Y
101820
Switch B
System MTU
The default system MTU for traffic on the switch is 1500 bytes. You can configure Fast Ethernet ports
to support frames larger than 1500 bytes by using the system mtu global configuration command. You
can configure Gigabit Ethernet ports to support frames larger than 1500 bytes by using the system mtu
jumbo global configuration command. Because the IEEE 802.1Q tunneling feature increases the frame
size by 4 bytes when the metro tag is added, you must configure all switches in the service-provider
network to be able to process maximum frames by increasing the switch system MTU size to at least
1504 bytes. The maximum allowable system MTU for Gigabit Ethernet interfaces is 9000 bytes; the
maximum system MTU for Fast Ethernet interfaces is 1998 bytes.
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Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling
Configuring IEEE 802.1Q Tunneling
IEEE 802.1Q Tunneling and Other Features
Although IEEE 802.1Q tunneling works well for Layer 2 packet switching, there are incompatibilities
between some Layer 2 features and Layer 3 switching.
•
A tunnel port cannot be a routed port.
•
IP routing is not supported on a VLAN that includes IEEE 802.1Q ports. Packets received from a
tunnel port are forwarded based only on Layer 2 information. If routing is enabled on a switch
virtual interface (SVI) that includes tunnel ports, untagged IP packets received from the tunnel port
are recognized and routed by the switch. Customer can access the internet through its native VLAN.
If this access is not needed, you should not configure SVIs on VLANs that include tunnel ports.
•
Fallback bridging is not supported on tunnel ports. Because all IEEE 802.1Q-tagged packets
received from a tunnel port are treated as non-IP packets, if fallback bridging is enabled on VLANs
that have tunnel ports configured, IP packets would be improperly bridged across VLANs.
Therefore, you must not enable fallback bridging on VLANs with tunnel ports.
•
Tunnel ports do not support IP access control lists (ACLs).
•
Layer 3 quality of service (QoS) ACLs and other QoS features related to Layer 3 information are
not supported on tunnel ports. MAC-based QoS is supported on tunnel ports.
•
EtherChannel port groups are compatible with tunnel ports as long as the IEEE 802.1Q
configuration is consistent within an EtherChannel port group.
•
Port Aggregation Protocol (PAgP), Link Aggregation Control Protocol (LACP), and UniDirectional
Link Detection (UDLD) are supported on IEEE 802.1Q tunnel ports.
•
Dynamic Trunking Protocol (DTP) is not compatible with IEEE 802.1Q tunneling because you must
manually configure asymmetric links with tunnel ports and trunk ports.
•
VLAN Trunking Protocol (VTP) does not work between devices that are connected by an
asymmetrical link or devices that communicate through a tunnel.
•
Loopback detection is supported on IEEE 802.1Q tunnel ports.
•
When a port is configured as an IEEE 802.1Q tunnel port, spanning-tree bridge protocol data unit
(BPDU) filtering is automatically enabled on the interface. Cisco Discovery Protocol (CDP) and the
Layer Link Discovery Protocol (LLDP) are automatically disabled on the interface.
Configuring an IEEE 802.1Q Tunneling Port
Beginning in privileged EXEC mode, follow these steps to configure a port as an IEEE 802.1Q tunnel
port:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Enter interface configuration mode for the interface to be configured as a
tunnel port. This should be the edge port in the service-provider network
that connects to the customer switch. Valid interfaces include physical
interfaces and port-channel logical interfaces (port channels 1 to 48).
Step 3
switchport access vlan vlan-id
Specify the default VLAN, which is used if the interface stops trunking.
This VLAN ID is specific to the particular customer.
Step 4
switchport mode dot1q-tunnel
Set the interface as an IEEE 802.1Q tunnel port.
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Understanding Layer 2 Protocol Tunneling
Command
Purpose
Step 5
exit
Return to global configuration mode.
Step 6
vlan dot1q tag native
(Optional) Set the switch to enable tagging of native VLAN packets on all
IEEE 802.1Q trunk ports. When not set, and a customer VLAN ID is the
same as the native VLAN, the trunk port does not apply a metro tag, and
packets could be sent to the wrong destination.
Step 7
end
Return to privileged EXEC mode.
Step 8
show running-config
Display the ports configured for IEEE 802.1Q tunneling.
show dot1q-tunnel
Display the ports that are in tunnel mode.
Step 9
show vlan dot1q tag native
Display IEEE 802.1Q native VLAN tagging status.
Step 10
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Use the no switchport mode dot1q-tunnel interface configuration command to return the port to the
default state of dynamic desirable. Use the no vlan dot1q tag native global configuration command to
disable tagging of native VLAN packets.
This example shows how to configure an interface as a tunnel port, enable tagging of native VLAN
packets, and verify the configuration. In this configuration, the VLAN ID for the customer connected to
Gigabit Ethernet interface 7 is VLAN 22.
Switch(config)# interface gigabitethernet0/7
Switch(config-if)# switchport access vlan 22
% Access VLAN does not exist. Creating vlan 22
Switch(config-if)# switchport mode dot1q-tunnel
Switch(config-if)# exit
Switch(config)# vlan dot1q tag native
Switch(config)# end
Switch# show dot1q-tunnel interface gigabitethernet0/7
Port
----Gi0/1Port
----Switch# show vlan dot1q tag native
dot1q native vlan tagging is enabled
Understanding Layer 2 Protocol Tunneling
Customers at different sites connected across a service-provider network need to use various Layer 2
protocols to scale their topologies to include all remote sites, as well as the local sites. STP must run
properly, and every VLAN should build a proper spanning tree that includes the local site and all remote
sites across the service-provider network. Cisco Discovery Protocol (CDP) must discover neighboring
Cisco devices from local and remote sites. VLAN Trunking Protocol (VTP) must provide consistent
VLAN configuration throughout all sites in the customer network.
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Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling
Understanding Layer 2 Protocol Tunneling
When protocol tunneling is enabled, edge switches on the inbound side of the service-provider network
encapsulate Layer 2 protocol packets with a special MAC address and send them across the
service-provider network. Core switches in the network do not process these packets but forward them
as normal packets. Layer 2 protocol data units (PDUs) for CDP, STP, or VTP cross the service-provider
network and are delivered to customer switches on the outbound side of the service-provider network.
Identical packets are received by all customer ports on the same VLANs with these results:
Note
•
Users on each of a customer’s sites can properly run STP, and every VLAN can build a correct
spanning tree based on parameters from all sites and not just from the local site.
•
CDP discovers and shows information about the other Cisco devices connected through the
service-provider network.
•
VTP provides consistent VLAN configuration throughout the customer network, propagating to all
switches through the service provider.
To provide interoperability with third-party vendors, you can use the Layer 2 protocol-tunnel bypass
feature. Bypass mode transparently forwards control PDUs to vendor switches that have different ways
of controlling protocol tunneling. You implement bypass mode by enabling Layer 2 protocol tunneling
on the egress trunk port. When Layer 2 protocol tunneling is enabled on the trunk port, the encapsulated
tunnel MAC address is removed and the protocol packets have their normal MAC address.
Layer 2 protocol tunneling can be used independently or can enhance IEEE 802.1Q tunneling. If protocol
tunneling is not enabled on IEEE 802.1Q tunneling ports, remote switches at the receiving end of the
service-provider network do not receive the PDUs and cannot properly run STP, CDP, and VTP. When
protocol tunneling is enabled, Layer 2 protocols within each customer’s network are totally separate
from those running within the service-provider network. Customer switches on different sites that send
traffic through the service-provider network with IEEE 802.1Q tunneling achieve complete knowledge
of the customer’s VLAN. If IEEE 802.1Q tunneling is not used, you can still enable Layer 2 protocol
tunneling by connecting to the customer switch through access ports and by enabling tunneling on the
service-provider access port.
For example, in Figure 16-4, Customer X has four switches in the same VLAN, that are connected
through the service-provider network. If the network does not tunnel PDUs, switches on the far ends of
the network cannot properly run STP, CDP, and VTP. For example, STP for a VLAN on a switch in
Customer X, Site 1, will build a spanning tree on the switches at that site without considering
convergence parameters based on Customer X’s switch in Site 2. This could result in the topology shown
in Figure 16-5.
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Understanding Layer 2 Protocol Tunneling
Figure 16-4
Layer 2 Protocol Tunneling
Customer X Site 1
VLANs 1ot 100
Customer X Site 2
Figure 16-5
Layer 2 Network Topology without Proper Convergence
101821
Customer X
virtual network
VLANs 1 to 100
In an SP network, you can use Layer 2 protocol tunneling to enhance the creation of EtherChannels by
emulating a point-to-point network topology. When you enable protocol tunneling (PAgP or LACP) on
the SP switch, remote customer switches receive the PDUs and can negotiate the automatic creation of
EtherChannels.
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Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling
Configuring Layer 2 Protocol Tunneling
For example, in Figure 16-6, Customer A has two switches in the same VLAN that are connected
through the SP network. When the network tunnels PDUs, switches on the far ends of the network can
negotiate the automatic creation of EtherChannels without needing dedicated lines. See the “Configuring
Layer 2 Tunneling for EtherChannels” section on page 16-14 for instructions.
Figure 16-6
Layer 2 Protocol Tunneling for EtherChannels
Configuring Layer 2 Protocol Tunneling
You can enable Layer 2 protocol tunneling (by protocol) on the ports that are connected to the customer
in the edge switches of the service-provider network. The service-provider edge switches connected to
the customer switch perform the tunneling process. Edge-switch tunnel ports are connected to customer
IEEE 802.1Q trunk ports. Edge-switch access ports are connected to customer access ports. The edge
switches connected to the customer switch perform the tunneling process.
You can enable Layer 2 protocol tunneling on ports that are configured as access ports or tunnel ports.
You cannot enable Layer 2 protocol tunneling on ports configured in either switchport mode dynamic
auto (the default mode) or switchport mode dynamic desirable.
The switch supports Layer 2 protocol tunneling for CDP, STP, and VTP. For emulated point-to-point
network topologies, it also supports PAgP, LACP, and UDLD protocols. The switch does not support
Layer 2 protocol tunneling for LLDP.
Caution
PAgP, LACP, and UDLD protocol tunneling is only intended to emulate a point-to-point topology. An
erroneous configuration that sends tunneled packets to many ports could lead to a network failure.
When the Layer 2 PDUs that entered the service-provider inbound edge switch through a Layer 2
protocol-enabled port exit through the trunk port into the service-provider network, the switch
overwrites the customer PDU-destination MAC address with a well-known Cisco proprietary multicast
address (01-00-0c-cd-cd-d0). If IEEE 802.1Q tunneling is enabled, packets are also double-tagged; the
outer tag is the customer metro tag, and the inner tag is the customer’s VLAN tag. The core switches
ignore the inner tags and forward the packet to all trunk ports in the same metro VLAN. The edge
switches on the outbound side restore the proper Layer 2 protocol and MAC address information and
forward the packets to all tunnel or access ports in the same metro VLAN. Therefore, the Layer 2 PDUs
remain intact and are delivered across the service-provider infrastructure to the other side of the
customer network.
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Configuring Layer 2 Protocol Tunneling
See Figure 16-4, with Customer X and Customer Y in access VLANs 30 and 40, respectively.
Asymmetric links connect the customers in Site 1 to edge switches in the service-provider network. The
Layer 2 PDUs (for example, BPDUs) coming into Switch 2 from Customer Y in Site 1 are forwarded to
the infrastructure as double-tagged packets with the well-known MAC address as the destination MAC
address. These double-tagged packets have the metro VLAN tag of 40, as well as an inner VLAN tag
(for example, VLAN 100). When the double-tagged packets enter Switch D, the outer VLAN tag 40 is
removed, the well-known MAC address is replaced with the respective Layer 2 protocol MAC address,
and the packet is sent to Customer Y on Site 2 as a single-tagged frame in VLAN 100.
You can also enable Layer 2 protocol tunneling on access ports on the edge switch connected to access
or trunk ports on the customer switch. In this case, the encapsulation and decapsulation process is the
same as described in the previous paragraph, except that the packets are not double-tagged in the
service-provider network. The single tag is the customer-specific access VLAN tag.
These sections contain this configuration information:
•
Default Layer 2 Protocol Tunneling Configuration, page 16-11
•
Layer 2 Protocol Tunneling Configuration Guidelines, page 16-11
•
Configuring Layer 2 Protocol Tunneling, page 16-13
•
Configuring Layer 2 Tunneling for EtherChannels, page 16-14
Default Layer 2 Protocol Tunneling Configuration
Table 16-1 shows the default Layer 2 protocol tunneling configuration.
Table 16-1
Default Layer 2 Ethernet Interface VLAN Configuration
Feature
Default Setting
Layer 2 protocol tunneling
Disabled.
Shutdown threshold
None set.
Drop threshold
None set.
CoS value
If a CoS value is configured on the interface, that value is used to
set the BPDU CoS value for Layer 2 protocol tunneling. If no CoS
value is configured at the interface level, the default value for CoS
marking of L2 protocol tunneling BPDUs is 5. This does not apply
to data traffic.
Layer 2 Protocol Tunneling Configuration Guidelines
These are some configuration guidelines and operating characteristics of Layer 2 protocol tunneling:
•
The switch supports tunneling of CDP, STP, including multiple STP (MSTP), and VTP. Protocol
tunneling is disabled by default but can be enabled for the individual protocols on IEEE 802.1Q
tunnel ports or access ports.
•
The switch does not support Layer 2 protocol tunneling on ports with switchport mode dynamic
auto or dynamic desirable.
•
DTP is not compatible with layer 2 protocol tunneling.
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Configuring Layer 2 Protocol Tunneling
•
The edge switches on the outbound side of the service-provider network restore the proper Layer 2
protocol and MAC address information and forward the packets to all tunnel and access ports in the
same metro VLAN.
•
For interoperability with third-party vendor switches, the switch supports a Layer 2 protocol-tunnel
bypass feature. Bypass mode transparently forwards control PDUs to vendor switches that have
different ways of controlling protocol tunneling.When Layer 2 protocol tunneling is enabled on
ingress ports on a switch, egress trunk ports forward the tunneled packets with a special
encapsulation. If you also enable Layer 2 protocol tunneling on the egress trunk port, this behavior
is bypassed, and the switch forwards control PDUs without any processing or modification.
•
The switch supports PAgP, LACP, and UDLD tunneling for emulated point-to-point network
topologies. Protocol tunneling is disabled by default but can be enabled for the individual protocols
on IEEE 802.1Q tunnel ports or on access ports.
•
If you enable PAgP or LACP tunneling, we recommend that you also enable UDLD on the interface
for faster link-failure detection.
•
Loopback detection is not supported on Layer 2 protocol tunneling of PAgP, LACP, or UDLD
packets.
•
EtherChannel port groups are compatible with tunnel ports when the IEEE 802.1Q configuration is
consistent within an EtherChannel port group.
•
If an encapsulated PDU (with the proprietary destination MAC address) is received from a tunnel
port or an access port with Layer 2 tunneling enabled, the tunnel port is shut down to prevent loops.
The port also shuts down when a configured shutdown threshold for the protocol is reached. You can
manually re-enable the port (by entering a shutdown and a no shutdown command sequence). If
errdisable recovery is enabled, the operation is retried after a specified time interval.
•
Only decapsulated PDUs are forwarded to the customer network. The spanning-tree instance
running on the service-provider network does not forward BPDUs to tunnel ports. CDP packets are
not forwarded from tunnel ports.
•
When protocol tunneling is enabled on an interface, you can set a per-protocol, per-port, shutdown
threshold for the PDUs generated by the customer network. If the limit is exceeded, the port shuts
down. You can also limit BPDU rate by using QoS ACLs and policy maps on a tunnel port.
•
When protocol tunneling is enabled on an interface, you can set a per-protocol, per-port, drop
threshold for the PDUs generated by the customer network. If the limit is exceeded, the port drops
PDUs until the rate at which it receives them is below the drop threshold.
•
Because tunneled PDUs (especially STP BPDUs) must be delivered to all remote sites so that the
customer virtual network operates properly, you can give PDUs higher priority within the
service-provider network than data packets received from the same tunnel port. By default, the
PDUs use the same CoS value as data packets.
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Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling
Configuring Layer 2 Protocol Tunneling
Configuring Layer 2 Protocol Tunneling
Beginning in privileged EXEC mode, follow these steps to configure a port for Layer 2 protocol
tunneling:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Enter interface configuration mode, and enter the interface to be configured
as a tunnel port. This should be the edge port in the service-provider
network that connects to the customer switch. Valid interfaces can be
physical interfaces and port-channel logical interfaces (port channels 1 to
48).
Step 3
switchport mode access
or
switchport mode dot1q-tunnel
Configure the interface as an access port or an IEEE 802.1Q tunnel port.
Step 4
l2protocol-tunnel [cdp | stp | vtp]
Enable protocol tunneling for the desired protocol. If no keyword is entered,
tunneling is enabled for all three Layer 2 protocols.
Step 5
l2protocol-tunnel
shutdown-threshold [cdp | stp | vtp]
value
(Optional) Configure the threshold for packets-per-second accepted for
encapsulation. The interface is disabled if the configured threshold is
exceeded. If no protocol option is specified, the threshold applies to each of
the tunneled Layer 2 protocol types. The range is 1 to 4096. The default is
to have no threshold configured.
Note
Step 6
l2protocol-tunnel drop-threshold
[cdp | stp | vtp] value
If you also set a drop threshold on this interface, the
shutdown-threshold value must be greater than or equal to the
drop-threshold value.
(Optional) Configure the threshold for packets-per-second accepted for
encapsulation. The interface drops packets if the configured threshold is
exceeded. If no protocol option is specified, the threshold applies to each of
the tunneled Layer 2 protocol types. The range is 1 to 4096. The default is
to have no threshold configured.
If you also set a shutdown threshold on this interface, the drop-threshold
value must be less than or equal to the shutdown-threshold value.
Step 7
exit
Step 8
errdisable recovery cause l2ptguard (Optional) Configure the recovery mechanism from a Layer 2
maximum-rate error so that the interface is re-enabled and can try again.
Errdisable recovery is disabled by default; when enabled, the default time
interval is 300 seconds.
Step 9
l2protocol-tunnel cos value
(Optional) Configure the CoS value for all tunneled Layer 2 PDUs. The
range is 0 to 7; the default is the default CoS value for the interface. If none
is configured, the default is 5.
Step 10
end
Return to privileged EXEC mode.
Step 11
show l2protocol
Display the Layer 2 tunnel ports on the switch, including the protocols
configured, the thresholds, and the counters.
Step 12
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Return to global configuration mode.
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Chapter 16
Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling
Configuring Layer 2 Protocol Tunneling
Use the no l2protocol-tunnel [cdp | stp | vtp] interface configuration command to disable protocol
tunneling for one of the Layer 2 protocols or for all three. Use the no l2protocol-tunnel
shutdown-threshold [cdp | stp | vtp] and the no l2protocol-tunnel drop-threshold [cdp | stp | vtp]
commands to return the shutdown and drop thresholds to the default settings.
This example shows how to configure Layer 2 protocol tunneling for CDP, STP, and VTP and to verify
the configuration.
Switch(config)# interface gigabitethernet0/11
Switch(config-if)# l2protocol-tunnel cdp
Switch(config-if)# l2protocol-tunnel stp
Switch(config-if)# l2protocol-tunnel vtp
Switch(config-if)# l2protocol-tunnel shutdown-threshold 1500
Switch(config-if)# l2protocol-tunnel drop-threshold 1000
Switch(config-if)# exit
Switch(config)# l2protocol-tunnel cos 7
Switch(config)# end
Switch# show l2protocol
COS for Encapsulated Packets: 7
Port
Protocol Shutdown Drop
Encapsulation Decapsulation
Threshold Threshold Counter
Counter
-------------- --------- --------- ------------- ------------Gi 0/11 cdp
1500
1000 2288
2282
stp
1500
1000 116
13
vtp
1500
1000 3
67
pagp
------- 0
0
lacp
------- 0
0
udld
------- 0
0
Drop
Counter
------------0
0
0
0
0
0
Configuring Layer 2 Tunneling for EtherChannels
To configure Layer 2 point-to-point tunneling to facilitate the automatic creation of EtherChannels, you
need to configure both the SP edge switch and the customer switch.
Configuring the SP Edge Switch
Beginning in privileged EXEC mode, follow these steps to configure a SP edge switch for Layer 2
protocol tunneling for EtherChannels:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Enter interface configuration mode, and enter the interface to be configured
as a tunnel port. This should be the edge port in the SP network that
connects to the customer switch. Valid interfaces are physical interfaces.
Step 3
switchport mode dot1q-tunnel
Configure the interface as an IEEE 802.1Q tunnel port.
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Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling
Configuring Layer 2 Protocol Tunneling
Step 4
Command
Purpose
l2protocol-tunnel point-to-point
[pagp | lacp | udld]
(Optional) Enable point-to-point protocol tunneling for the desired
protocol. If no keyword is entered, tunneling is enabled for all three
protocols.
Caution
Step 5
l2protocol-tunnel
shutdown-threshold [point-to-point
[pagp | lacp | udld]] value
(Optional) Configure the threshold for packets-per-second accepted for
encapsulation. The interface is disabled if the configured threshold is
exceeded. If no protocol option is specified, the threshold applies to each of
the tunneled Layer 2 protocol types. The range is 1 to 4096. The default is
to have no threshold configured.
Note
Step 6
l2protocol-tunnel drop-threshold
[point-to-point [pagp | lacp | udld]]
value
To avoid a network failure, make sure that the network is a
point-to-point topology before you enable tunneling for PAgP,
LACP, or UDLD packets.
If you also set a drop threshold on this interface, the
shutdown-threshold value must be greater than or equal to the
drop-threshold value.
(Optional) Configure the threshold for packets-per-second accepted for
encapsulation. The interface drops packets if the configured threshold is
exceeded. If no protocol option is specified, the threshold applies to each of
the tunneled Layer 2 protocol types. The range is 1 to 4096. The default is
to have no threshold configured.
Note
If you also set a shutdown threshold on this interface, the
drop-threshold value must be less than or equal to the
shutdown-threshold value.
Step 7
no cdp enable
Disable CDP on the interface.
Step 8
spanning-tree bpdufilter enable
Enable BPDU filtering on the interface.
Step 9
exit
Return to global configuration mode.
Step 10
errdisable recovery cause l2ptguard (Optional) Configure the recovery mechanism from a Layer 2
maximum-rate error so that the interface is re-enabled and can try again.
Errdisable recovery is disabled by default; when enabled, the default time
interval is 300 seconds.
Step 11
l2protocol-tunnel cos value
(Optional) Configure the CoS value for all tunneled Layer 2 PDUs. The
range is 0 to 7; the default is the default CoS value for the interface. If none
is configured, the default is 5.
Step 12
end
Return to privileged EXEC mode.
Step 13
show l2protocol
Display the Layer 2 tunnel ports on the switch, including the protocols
configured, the thresholds, and the counters.
Step 14
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Use the no l2protocol-tunnel [point-to-point [pagp | lacp | udld]] interface configuration command to
disable point-to-point protocol tunneling for one of the Layer 2 protocols or for all three. Use the no
l2protocol-tunnel shutdown-threshold [point-to-point [pagp | lacp | udld]] and the no
l2protocol-tunnel drop-threshold [[point-to-point [pagp | lacp | udld]] commands to return the
shutdown and drop thresholds to the default settings.
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Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling
Configuring Layer 2 Protocol Tunneling
Configuring the Customer Switch
After configuring the SP edge switch, begin in privileged EXEC mode and follow these steps to
configure a customer switch for Layer 2 protocol tunneling for EtherChannels:
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Enter the interface configuration mode. This should be the customer switch
port.
Step 3
switchport trunk encapsulation
dot1q
Set the trunking encapsulation format to IEEE 802.1Q.
Step 4
switchport mode trunk
Enable trunking on the interface.
Step 5
udld enable
Enable UDLD in normal mode on the interface.
Step 6
channel-group channel-group-number Assign the interface to a channel group, and specify desirable for the PAgP
mode desirable
mode. For more information about configuring EtherChannels, see
Chapter 35, “Configuring EtherChannels and Layer 2 Trunk Failover.”
Step 7
exit
Return to global configuration mode.
Step 8
interface port-channel port-channel
number
Enter port-channel interface mode.
Step 9
shutdown
Shut down the interface.
Step 10
no shutdown
Enable the interface.
Step 11
end
Return to privileged EXEC mode.
Step 12
show l2protocol
Display the Layer 2 tunnel ports on the switch, including the protocols
configured, the thresholds, and the counters.
Step 13
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Use the no switchport mode trunk, the no udld enable, and the no channel group
channel-group-number mode desirable interface configuration commands to return the interface to the
default settings.
For EtherChannels, you need to configure both the SP edge switches and the customer switches for
Layer 2 protocol tunneling. (See Figure 16-6 on page 16-10.)
This example shows how to configure the SP edge switch 1 and edge switch 2. VLANs 17, 18, 19, and
20 are the access VLANs, Gigabit Ethernet interfaces 1 and 2 are point-to-point tunnel ports with PAgP
and UDLD enabled, the drop threshold is 1000, and Gigabit Ethernet interface 3 is a trunk port.
SP edge switch 1 configuration:
Switch(config)# interface gigabitethernet0/1
Switch(config-if)# switchport access vlan 17
Switch(config-if)# switchport mode dot1q-tunnel
Switch(config-if)# l2protocol-tunnel point-to-point
Switch(config-if)# l2protocol-tunnel point-to-point
Switch(config-if)# l2protocol-tunnel drop-threshold
Switch(config-if)# exit
Switch(config)# interface gigabitethernet0/2
Switch(config-if)# switchport access vlan 18
Switch(config-if)# switchport mode dot1q-tunnel
Switch(config-if)# l2protocol-tunnel point-to-point
Switch(config-if)# l2protocol-tunnel point-to-point
pagp
udld
point-to-point pagp 1000
pagp
udld
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Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling
Configuring Layer 2 Protocol Tunneling
Switch(config-if)# l2protocol-tunnel drop-threshold point-to-point pagp 1000
Switch(config-if)# exit
Switch(config)# interface gigabitethernet0/3
Switch(config-if)# switchport trunk encapsulation isl
Switch(config-if)# switchport mode trunk
SP edge switch 2 configuration:
Switch(config)# interface fgigabitethernet0/1
Switch(config-if)# switchport access vlan 19
Switch(config-if)# switchport mode dot1q-tunnel
Switch(config-if)# l2protocol-tunnel point-to-point pagp
Switch(config-if)# l2protocol-tunnel point-to-point udld
Switch(config-if)# l2protocol-tunnel drop-threshold point-to-point pagp 1000
Switch(config-if)# exit
Switch(config)# interface gigabitethernet0/2
Switch(config-if)# switchport access vlan 20
Switch(config-if)# switchport mode dot1q-tunnel
Switch(config-if)# l2protocol-tunnel point-to-point pagp
Switch(config-if)# l2protocol-tunnel point-to-point udld
Switch(config-if)# l2protocol-tunnel drop-threshold point-to-point pagp 1000
Switch(config-if)# exit
Switch(config)# interface gigabitethernet0/3
Switch(config-if)# switchport trunk encapsulation isl
Switch(config-if)# switchport mode trunk
This example shows how to configure the customer switch at Site 1. Gigabit Ethernet interfaces 1, 2, 3,
and 4 are set for IEEE 802.1Q trunking, UDLD is enabled, EtherChannel group 1 is enabled, and the port
channel is shut down and then enabled to activate the EtherChannel configuration.
Switch(config)# interface gigabitethernet0/1
Switch(config-if)# switchport trunk encapsulation
Switch(config-if)# switchport mode trunk
Switch(config-if)# udld enable
Switch(config-if)# channel-group 1 mode desirable
Switch(config-if)# exit
Switch(config)# interface gigabitethernet0/2
Switch(config-if)# switchport trunk encapsulation
Switch(config-if)# switchport mode trunk
Switch(config-if)# udld enable
Switch(config-if)# channel-group 1 mode desirable
Switch(config-if)# exit
Switch(config)# interface gigabitethernet0/3
Switch(config-if)# switchport trunk encapsulation
Switch(config-if)# switchport mode trunk
Switch(config-if)# udld enable
Switch(config-if)# channel-group 1 mode desirable
Switch(config-if)# exit
Switch(config)# interface gigabitethernet0/4
Switch(config-if)# switchport trunk encapsulation
Switch(config-if)# switchport mode trunk
Switch(config-if)# udld enable
Switch(config-if)# channel-group 1 mode desirable
Switch(config-if)# exit
Switch(config)# interface port-channel 1
Switch(config-if)# shutdown
Switch(config-if)# no shutdown
Switch(config-if)# exit
dot1q
dot1q
dot1q
dot1q
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Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling
Monitoring and Maintaining Tunneling Status
Monitoring and Maintaining Tunneling Status
Table 16-2 shows the privileged EXEC commands for monitoring and maintaining IEEE 802.1Q and
Layer 2 protocol tunneling.
Table 16-2
Commands for Monitoring and Maintaining Tunneling
Command
Purpose
clear l2protocol-tunnel counters
Clear the protocol counters on Layer 2 protocol tunneling ports.
show dot1q-tunnel
Display IEEE 802.1Q tunnel ports on the switch.
show dot1q-tunnel interface interface-id
Verify if a specific interface is a tunnel port.
show l2protocol-tunnel
Display information about Layer 2 protocol tunneling ports.
show errdisable recovery
Verify if the recovery timer from a Layer 2 protocol-tunnel error disable
state is enabled.
show l2protocol-tunnel interface interface-id
Display information about a specific Layer 2 protocol tunneling port.
show l2protocol-tunnel summary
Display only Layer 2 protocol summary information.
show vlan dot1q tag native
Display the status of native VLAN tagging on the switch.
For detailed information about these displays, see the command reference for this release.
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17
Configuring STP
This chapter describes how to configure the Spanning Tree Protocol (STP) on port-based VLANs on the
switch. The switch can use either the per-VLAN spanning-tree plus (PVST+) protocol based on the IEEE
802.1D standard and Cisco proprietary extensions, or the rapid per-VLAN spanning-tree plus
(rapid-PVST+) protocol based on the IEEE 802.1w standard.
For information about the Multiple Spanning Tree Protocol (MSTP) and how to map multiple VLANs
to the same spanning-tree instance, see Chapter 18, “Configuring MSTP.” For information about other
spanning-tree features such as Port Fast, UplinkFast, root guard, and so forth, see Chapter 19,
“Configuring Optional Spanning-Tree Features.”
Note
For complete syntax and usage information for the commands used in this chapter, see the command
reference for this release.
This chapter consists of these sections:
•
Understanding Spanning-Tree Features, page 17-1
•
Configuring Spanning-Tree Features, page 17-10
•
Displaying the Spanning-Tree Status, page 17-22
Understanding Spanning-Tree Features
These sections contain this conceptual information:
•
STP Overview, page 17-2
•
Spanning-Tree Topology and BPDUs, page 17-3
•
Bridge ID, Switch Priority, and Extended System ID, page 17-4
•
Spanning-Tree Interface States, page 17-4
•
How a Switch or Port Becomes the Root Switch or Root Port, page 17-7
•
Spanning Tree and Redundant Connectivity, page 17-8
•
Spanning-Tree Address Management, page 17-8
•
Accelerated Aging to Retain Connectivity, page 17-8
•
Spanning-Tree Modes and Protocols, page 17-9
•
Supported Spanning-Tree Instances, page 17-9
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Configuring STP
Understanding Spanning-Tree Features
•
Spanning-Tree Interoperability and Backward Compatibility, page 17-10
•
STP and IEEE 802.1Q Trunks, page 17-10
For configuration information, see the “Configuring Spanning-Tree Features” section on page 17-10.
For information about optional spanning-tree features, see Chapter 19, “Configuring Optional
Spanning-Tree Features”.
STP Overview
STP is a Layer 2 link management protocol that provides path redundancy while preventing loops in the
network. For a Layer 2 Ethernet network to function properly, only one active path can exist between
any two stations. Multiple active paths among end stations cause loops in the network. If a loop exists
in the network, end stations might receive duplicate messages. Switches might also learn end-station
MAC addresses on multiple Layer 2 interfaces. These conditions result in an unstable network.
Spanning-tree operation is transparent to end stations, which cannot detect whether they are connected
to a single LAN segment or a switched LAN of multiple segments.
The STP uses a spanning-tree algorithm to select one switch of a redundantly connected network as the
root of the spanning tree. The algorithm calculates the best loop-free path through a switched Layer 2
network by assigning a role to each port based on the role of the port in the active topology:
•
Root—A forwarding port elected for the spanning-tree topology
•
Designated—A forwarding port elected for every switched LAN segment
•
Alternate—A blocked port providing an alternate path to the root bridge in the spanning tree
•
Backup—A blocked port in a loopback configuration
The switch that has all of its ports as the designated role or as the backup role is the root switch. The
switch that has at least one of its ports in the designated role is called the designated switch.
Spanning tree forces redundant data paths into a standby (blocked) state. If a network segment in the
spanning tree fails and a redundant path exists, the spanning-tree algorithm recalculates the
spanning-tree topology and activates the standby path. Switches send and receive spanning-tree frames,
called bridge protocol data units (BPDUs), at regular intervals. The switches do not forward these frames
but use them to construct a loop-free path. BPDUs contain information about the sending switch and its
ports, including switch and MAC addresses, switch priority, port priority, and path cost. Spanning tree
uses this information to elect the root switch and root port for the switched network and the root port and
designated port for each switched segment.
When two ports on a switch are part of a loop, the spanning-tree port priority and path cost settings
control which port is put in the forwarding state and which is put in the blocking state. The spanning-tree
port priority value represents the location of a port in the network topology and how well it is located to
pass traffic. The path cost value represents the media speed.
Note
The switch sends keepalive messages (to ensure the connection is up) only on interfaces that do not have
small form-factor pluggable (SFP) modules.
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Configuring STP
Understanding Spanning-Tree Features
Spanning-Tree Topology and BPDUs
The stable, active spanning-tree topology of a switched network is controlled by these elements:
•
The unique bridge ID (switch priority and MAC address) associated with each VLAN on each
switch.
•
The spanning-tree path cost to the root switch.
•
The port identifier (port priority and MAC address) associated with each Layer 2 interface.
When the switches in a network are powered up, each functions as the root switch. Each switch sends a
configuration BPDU through all of its ports. The BPDUs communicate and compute the spanning-tree
topology. Each configuration BPDU contains this information:
•
The unique bridge ID of the switch that the sending switch identifies as the root switch
•
The spanning-tree path cost to the root
•
The bridge ID of the sending switch
•
Message age
•
The identifier of the sending interface
•
Values for the hello, forward delay, and max-age protocol timers
When a switch receives a configuration BPDU that contains superior information (lower bridge ID,
lower path cost, and so forth), it stores the information for that port. If this BPDU is received on the root
port of the switch, the switch also forwards it with an updated message to all attached LANs for which
it is the designated switch.
If a switch receives a configuration BPDU that contains inferior information to that currently stored for
that port, it discards the BPDU. If the switch is a designated switch for the LAN from which the inferior
BPDU was received, it sends that LAN a BPDU containing the up-to-date information stored for that
port. In this way, inferior information is discarded, and superior information is propagated on the
network.
A BPDU exchange results in these actions:
•
One switch in the network is elected as the root switch (the logical center of the spanning-tree
topology in a switched network).
For each VLAN, the switch with the highest switch priority (the lowest numerical priority value) is
elected as the root switch. If all switches are configured with the default priority (32768), the switch
with the lowest MAC address in the VLAN becomes the root switch. The switch priority value
occupies the most significant bits of the bridge ID, as shown in Table 17-1 on page 17-4.
•
A root port is selected for each switch (except the root switch). This port provides the best path
(lowest cost) when the switch forwards packets to the root switch.
•
The shortest distance to the root switch is calculated for each switch based on the path cost.
•
A designated switch for each LAN segment is selected. The designated switch incurs the lowest path
cost when forwarding packets from that LAN to the root switch. The port through which the
designated switch is attached to the LAN is called the designated port.
All paths that are not needed to reach the root switch from anywhere in the switched network are placed
in the spanning-tree blocking mode.
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Configuring STP
Understanding Spanning-Tree Features
Bridge ID, Switch Priority, and Extended System ID
The IEEE 802.1D standard requires that each switch has an unique bridge identifier (bridge ID), which
controls the selection of the root switch. Because each VLAN is considered as a different logical bridge
with PVST+ and rapid PVST+, the same switch must have a different bridge IDs for each configured
VLAN. Each VLAN on the switch has a unique 8-byte bridge ID. The 2 most-significant bytes are used
for the switch priority, and the remaining 6 bytes are derived from the switch MAC address.
The switch supports the IEEE 802.1t spanning-tree extensions, and some of the bits previously used for
the switch priority are now used as the VLAN identifier. The result is that fewer MAC addresses are
reserved for the switch, and a larger range of VLAN IDs can be supported, all while maintaining the
uniqueness of the bridge ID. As shown in Table 17-1, the 2 bytes previously used for the switch priority
are reallocated into a 4-bit priority value and a 12-bit extended system ID value equal to the VLAN ID.
Table 17-1
Switch Priority Value and Extended System ID
Switch Priority Value
Extended System ID (Set Equal to the VLAN ID)
Bit 16
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
32768
16384
8192
4096
2048
1024
512
256
128
64
32
16
8
4
2
1
Spanning tree uses the extended system ID, the switch priority, and the allocated spanning-tree MAC
address to make the bridge ID unique for each VLAN.
Support for the extended system ID affects how you manually configure the root switch, the secondary
root switch, and the switch priority of a VLAN. For example, when you change the switch priority value,
you change the probability that the switch will be elected as the root switch. Configuring a higher value
decreases the probability; a lower value increases the probability. For more information, see the
“Configuring the Root Switch” section on page 17-14, the “Configuring a Secondary Root Switch”
section on page 17-16, and the “Configuring the Switch Priority of a VLAN” section on page 17-19.
Spanning-Tree Interface States
Propagation delays can occur when protocol information passes through a switched LAN. As a result,
topology changes can take place at different times and at different places in a switched network. When
an interface transitions directly from nonparticipation in the spanning-tree topology to the forwarding
state, it can create temporary data loops. Interfaces must wait for new topology information to propagate
through the switched LAN before starting to forward frames. They must allow the frame lifetime to
expire for forwarded frames that have used the old topology.
Each Layer 2 interface on a switch using spanning tree exists in one of these states:
•
Blocking—The interface does not participate in frame forwarding.
•
Listening—The first transitional state after the blocking state when the spanning tree decides that
the interface should participate in frame forwarding.
•
Learning—The interface prepares to participate in frame forwarding.
•
Forwarding—The interface forwards frames.
•
Disabled—The interface is not participating in spanning tree because of a shutdown port, no link on
the port, or no spanning-tree instance running on the port.
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Configuring STP
Understanding Spanning-Tree Features
An interface moves through these states:
•
From initialization to blocking
•
From blocking to listening or to disabled
•
From listening to learning or to disabled
•
From learning to forwarding or to disabled
•
From forwarding to disabled
Figure 17-1 illustrates how an interface moves through the states.
Figure 17-1
Spanning-Tree Interface States
Power-on
initialization
Blocking
state
Listening
state
Disabled
state
Forwarding
state
43569
Learning
state
When you power up the switch, spanning tree is enabled by default, and every interface in the switch,
VLAN, or network goes through the blocking state and the transitory states of listening and learning.
Spanning tree stabilizes each interface at the forwarding or blocking state.
When the spanning-tree algorithm places a Layer 2 interface in the forwarding state, this process occurs:
1.
The interface is in the listening state while spanning tree waits for protocol information to move the
interface to the blocking state.
2.
While spanning tree waits the forward-delay timer to expire, it moves the interface to the learning
state and resets the forward-delay timer.
3.
In the learning state, the interface continues to block frame forwarding as the switch learns
end-station location information for the forwarding database.
4.
When the forward-delay timer expires, spanning tree moves the interface to the forwarding state,
where both learning and frame forwarding are enabled.
Blocking State
A Layer 2 interface in the blocking state does not participate in frame forwarding. After initialization, a
BPDU is sent to each switch interface. A switch initially functions as the root until it exchanges BPDUs
with other switches. This exchange establishes which switch in the network is the root or root switch. If
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there is only one switch in the network, no exchange occurs, the forward-delay timer expires, and the
interface moves to the listening state. An interface always enters the blocking state after switch
initialization.
An interface in the blocking state performs these functions:
•
Discards frames received on the interface
•
Discards frames switched from another interface for forwarding
•
Does not learn addresses
•
Receives BPDUs
Listening State
The listening state is the first state a Layer 2 interface enters after the blocking state. The interface enters
this state when the spanning tree decides that the interface should participate in frame forwarding.
An interface in the listening state performs these functions:
•
Discards frames received on the interface
•
Discards frames switched from another interface for forwarding
•
Does not learn addresses
•
Receives BPDUs
Learning State
A Layer 2 interface in the learning state prepares to participate in frame forwarding. The interface enters
the learning state from the listening state.
An interface in the learning state performs these functions:
•
Discards frames received on the interface
•
Discards frames switched from another interface for forwarding
•
Learns addresses
•
Receives BPDUs
Forwarding State
A Layer 2 interface in the forwarding state forwards frames. The interface enters the forwarding state
from the learning state.
An interface in the forwarding state performs these functions:
•
Receives and forwards frames received on the interface
•
Forwards frames switched from another interface
•
Learns addresses
•
Receives BPDUs
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Disabled State
A Layer 2 interface in the disabled state does not participate in frame forwarding or in the spanning tree.
An interface in the disabled state is nonoperational.
A disabled interface performs these functions:
•
Discards frames received on the interface
•
Discards frames switched from another interface for forwarding
•
Does not learn addresses
•
Does not receive BPDUs
How a Switch or Port Becomes the Root Switch or Root Port
If all switches in a network are enabled with default spanning-tree settings, the switch with the lowest
MAC address becomes the root switch. In Figure 17-2, Switch A is elected as the root switch because
the switch priority of all the switches is set to the default (32768) and Switch A has the lowest MAC
address. However, because of traffic patterns, number of forwarding interfaces, or link types, Switch A
might not be the ideal root switch. By increasing the priority (lowering the numerical value) of the ideal
switch so that it becomes the root switch, you force a spanning-tree recalculation to form a new topology
with the ideal switch as the root.
Figure 17-2
Spanning-Tree Topology
DP
A
DP
D
RP
DP
RP
B
DP
RP
C
86475
DP
RP = Root Port
DP = Designated Port
When the spanning-tree topology is calculated based on default parameters, the path between source and
destination end stations in a switched network might not be ideal. For instance, connecting higher-speed
links to an interface that has a higher number than the root port can cause a root-port change. The goal
is to make the fastest link the root port.
For example, assume that one port on Switch B is a Gigabit Ethernet link and that another port on
Switch B (a 10/100 link) is the root port. Network traffic might be more efficient over the Gigabit
Ethernet link. By changing the spanning-tree port priority on the Gigabit Ethernet port to a higher
priority (lower numerical value) than the root port, the Gigabit Ethernet port becomes the new root port.
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Spanning Tree and Redundant Connectivity
You can create a redundant backbone with spanning tree by connecting two switch interfaces to another
device or to two different devices, as shown in Figure 17-3. Spanning tree automatically disables one
interface but enables it if the other one fails. If one link is high-speed and the other is low-speed, the
low-speed link is always disabled. If the speeds are the same, the port priority and port ID are added
together, and spanning tree disables the link with the lowest value.
Spanning Tree and Redundant Connectivity
119766
Figure 17-3
Active link
Blocked link
Blade Servers
You can also create redundant links between switches by using EtherChannel groups. For more
information, see Chapter 35, “Configuring EtherChannels and Layer 2 Trunk Failover.”
Spanning-Tree Address Management
IEEE 802.1D specifies 17 multicast addresses, ranging from 0x00180C2000000 to 0x0180C2000010, to
be used by different bridge protocols. These addresses are static addresses that cannot be removed.
Regardless of the spanning-tree state, each switch receives but does not forward packets destined for
addresses between 0x0180C2000000 and 0x0180C200000F.
If spanning tree is enabled, the CPU on the switch receives packets destined for 0x0180C2000000 and
0x0180C2000010. If spanning tree is disabled, the switch forwards those packets as unknown multicast
addresses.
Accelerated Aging to Retain Connectivity
The default for aging dynamic addresses is 5 minutes, the default setting of the mac address-table
aging-time global configuration command. However, a spanning-tree reconfiguration can cause many
station locations to change. Because these stations could be unreachable for 5 minutes or more during a
reconfiguration, the address-aging time is accelerated so that station addresses can be dropped from the
address table and then relearned. The accelerated aging is the same as the forward-delay parameter value
(spanning-tree vlan vlan-id forward-time seconds global configuration command) when the spanning
tree reconfigures.
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Because each VLAN is a separate spanning-tree instance, the switch accelerates aging on a per-VLAN
basis. A spanning-tree reconfiguration on one VLAN can cause the dynamic addresses learned on that
VLAN to be subject to accelerated aging. Dynamic addresses on other VLANs can be unaffected and
remain subject to the aging interval entered for the switch.
Spanning-Tree Modes and Protocols
The switch supports these spanning-tree modes and protocols:
•
PVST+—This spanning-tree mode is based on the IEEE 802.1D standard and Cisco proprietary
extensions. It is the default spanning-tree mode used on all Ethernet port-based VLANs. The PVST+
runs on each VLAN on the switch up to the maximum supported, ensuring that each has a loop-free
path through the network.
The PVST+ provides Layer 2 load balancing for the VLAN on which it runs. You can create different
logical topologies by using the VLANs on your network to ensure that all of your links are used but
that no one link is oversubscribed. Each instance of PVST+ on a VLAN has a single root switch.
This root switch propagates the spanning-tree information associated with that VLAN to all other
switches in the network. Because each switch has the same information about the network, this
process ensures that the network topology is maintained.
•
Rapid PVST+—This spanning-tree mode is the same as PVST+ except that is uses a rapid
convergence based on the IEEE 802.1w standard. To provide rapid convergence, the rapid PVST+
immediately deletes dynamically learned MAC address entries on a per-port basis upon receiving a
topology change. By contrast, PVST+ uses a short aging time for dynamically learned MAC address
entries.
The rapid PVST+ uses the same configuration as PVST+ (except where noted), and the switch needs
only minimal extra configuration. The benefit of rapid PVST+ is that you can migrate a large PVST+
install base to rapid PVST+ without having to learn the complexities of the MSTP configuration and
without having to reprovision your network. In rapid-PVST+ mode, each VLAN runs its own
spanning-tree instance up to the maximum supported.
•
MSTP—This spanning-tree mode is based on the IEEE 802.1s standard. You can map multiple
VLANs to the same spanning-tree instance, which reduces the number of spanning-tree instances
required to support a large number of VLANs. The MSTP runs on top of the RSTP (based on
IEEE 802.1w), which provides for rapid convergence of the spanning tree by eliminating the
forward delay and by quickly transitioning root ports and designated ports to the forwarding state.
You cannot run MSTP without RSTP or CSRT.
The most common initial deployment of MSTP is in the backbone and distribution layers of a
Layer 2 switched network. For more information, see Chapter 18, “Configuring MSTP.”
For information about the number of supported spanning-tree instances, see the next section.
Supported Spanning-Tree Instances
In PVST+ or rapid-PVST+ mode, the switch supports up to 128 spanning-tree instances.
In MSTP mode, the switch supports up to 65 MST instances. The number of VLANs that can be mapped
to a particular MST instance is unlimited.
For information about how spanning tree interoperates with the VLAN Trunking Protocol (VTP), see the
“Spanning-Tree Configuration Guidelines” section on page 17-12.
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Spanning-Tree Interoperability and Backward Compatibility
Table 17-2 lists the interoperability and compatibility among the supported spanning-tree modes in a
network.
Table 17-2
PVST+, MSTP, and Rapid-PVST+ Interoperability
PVST+
MSTP
Rapid PVST+
PVST+
Yes
Yes (with restrictions)
Yes (reverts to PVST+)
MSTP
Yes (with restrictions)
Yes
Yes (reverts to PVST+)
Rapid PVST+
Yes (reverts to PVST+)
Yes (reverts to PVST+)
Yes
In a mixed MSTP and PVST+ network, the common spanning-tree (CST) root must be inside the MST
backbone, and a PVST+ switch cannot connect to multiple MST regions.
When a network contains switches running rapid PVST+ and switches running PVST+, we recommend
that the rapid-PVST+ switches and PVST+ switches be configured for different spanning-tree instances.
In the rapid-PVST+ spanning-tree instances, the root switch must be a rapid-PVST+ switch. In the
PVST+ instances, the root switch must be a PVST+ switch. The PVST+ switches should be at the edge
of the network.
STP and IEEE 802.1Q Trunks
The IEEE 802.1Q standard for VLAN trunks imposes some limitations on the spanning-tree strategy for
a network. The standard requires only one spanning-tree instance for all VLANs allowed on the trunks.
However, in a network of Cisco switches connected through IEEE 802.1Q trunks, the switches maintain
one spanning-tree instance for each VLAN allowed on the trunks.
When you connect a Cisco switch to a non-Cisco device through an IEEE 802.1Q trunk, the Cisco switch
uses PVST+ to provide spanning-tree interoperability. If rapid PVST+ is enabled, the switch uses it
instead of PVST+. The switch combines the spanning-tree instance of the IEEE 802.1Q VLAN of the
trunk with the spanning-tree instance of the non-Cisco IEEE 802.1Q switch.
However, all PVST+ or rapid-PVST+ information is maintained by Cisco switches separated by a cloud
of non-Cisco IEEE 802.1Q switches. The non-Cisco IEEE 802.1Q cloud separating the Cisco switches
is treated as a single trunk link between the switches.
PVST+ is automatically enabled on IEEE 802.1Q trunks, and no user configuration is required. The
external spanning-tree behavior on access ports and Inter-Switch Link (ISL) trunk ports is not affected
by PVST+.
For more information on IEEE 802.1Q trunks, see Chapter 12, “Configuring VLANs”.
Configuring Spanning-Tree Features
These sections contain this configuration information:
•
Default Spanning-Tree Configuration, page 17-11
•
Spanning-Tree Configuration Guidelines, page 17-12
•
Changing the Spanning-Tree Mode., page 17-13 (required)
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•
Disabling Spanning Tree, page 17-14 (optional)
•
Configuring the Root Switch, page 17-14 (optional)
•
Configuring a Secondary Root Switch, page 17-16 (optional)
•
Configuring Port Priority, page 17-16 (optional)
•
Configuring Path Cost, page 17-18 (optional)
•
Configuring the Switch Priority of a VLAN, page 17-19 (optional)
•
Configuring Spanning-Tree Timers, page 17-20 (optional)
Default Spanning-Tree Configuration
Table 17-3 shows the default spanning-tree configuration.
Table 17-3
Default Spanning-Tree Configuration
Feature
Default Setting
Enable state
Enabled on VLAN 1.
For more information, see the “Supported
Spanning-Tree Instances” section on
page 17-9.
Spanning-tree mode
PVST+. (Rapid PVST+ and MSTP are
disabled.)
Switch priority
32768.
Spanning-tree port priority (configurable on a per-interface basis)
128.
Spanning-tree port cost (configurable on a per-interface basis)
1000 Mb/s: 4.
100 Mb/s: 19.
10 Mb/s: 100.
Spanning-tree VLAN port priority (configurable on a per-VLAN basis)
128.
Spanning-tree VLAN port cost (configurable on a per-VLAN basis)
1000 Mb/s: 4.
100 Mb/s: 19.
10 Mb/s: 100.
Spanning-tree timers
Hello time: 2 seconds.
Forward-delay time: 15 seconds.
Maximum-aging time: 20 seconds.
Transmit hold count: 6 BPDUs
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Spanning-Tree Configuration Guidelines
If more VLANs are defined in the VTP than there are spanning-tree instances, you can enable PVST+
or rapid PVST+ on only 128 VLANs on the switch. The remaining VLANs operate with spanning tree
disabled. However, you can map multiple VLANs to the same spanning-tree instances by using MSTP.
For more information, see Chapter 18, “Configuring MSTP.”
If 128 instances of spanning tree are already in use, you can disable spanning tree on one of the VLANs
and then enable it on the VLAN where you want it to run. Use the no spanning-tree vlan vlan-id global
configuration command to disable spanning tree on a specific VLAN, and use the spanning-tree vlan
vlan-id global configuration command to enable spanning tree on the desired VLAN.
Caution
Switches that are not running spanning tree still forward BPDUs that they receive so that the other
switches on the VLAN that have a running spanning-tree instance can break loops. Therefore, spanning
tree must be running on enough switches to break all the loops in the network; for example, at least one
switch on each loop in the VLAN must be running spanning tree. It is not absolutely necessary to run
spanning tree on all switches in the VLAN. However, if you are running spanning tree only on a minimal
set of switches, an incautious change to the network that introduces another loop into the VLAN can
result in a broadcast storm.
Note
If you have already used all available spanning-tree instances on your switch, adding another VLAN
anywhere in the VTP domain creates a VLAN that is not running spanning tree on that switch. If you
have the default allowed list on the trunk ports of that switch, the new VLAN is carried on all trunk ports.
Depending on the topology of the network, this could create a loop in the new VLAN that will not be
broken, particularly if there are several adjacent switches that have all run out of spanning-tree instances.
You can prevent this possibility by setting up allowed lists on the trunk ports of switches that have used
up their allocation of spanning-tree instances. Setting up allowed lists is not necessary in many cases and
can make it more labor-intensive to add another VLAN to the network.
Spanning-tree commands control the configuration of VLAN spanning-tree instances. You create a
spanning-tree instance when you assign an interface to a VLAN. The spanning-tree instance is removed
when the last interface is moved to another VLAN. You can configure switch and port parameters before
a spanning-tree instance is created; these parameters are applied when the spanning-tree instance is
created.
The switch supports PVST+, rapid PVST+, and MSTP, but only one version can be active at any time.
(For example, all VLANs run PVST+, all VLANs run rapid PVST+, or all VLANs run MSTP.) For
information about the different spanning-tree modes and how they interoperate, see the “Spanning-Tree
Interoperability and Backward Compatibility” section on page 17-10.
For configuration guidelines about UplinkFast and BackboneFast, see the “Optional Spanning-Tree
Configuration Guidelines” section on page 19-10.
Caution
Loop guard works only on point-to-point links. We recommend that each end of the link has a directly
connected device that is running STP.
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Changing the Spanning-Tree Mode.
The switch supports three spanning-tree modes: PVST+, rapid PVST+, or MSTP. By default, the switch
runs the PVST+ protocol.
Beginning in privileged EXEC mode, follow these steps to change the spanning-tree mode. If you want
to enable a mode that is different from the default mode, this procedure is required.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
spanning-tree mode {pvst | mst |
rapid-pvst}
Configure a spanning-tree mode.
•
Select pvst to enable PVST+ (the default setting).
•
Select mst to enable MSTP (and RSTP). For more configuration
steps, see Chapter 18, “Configuring MSTP”.
•
Select rapid-pvst to enable rapid PVST+.
Step 3
interface interface-id
(Recommended for rapid-PVST+ mode only) Specify an interface to
configure, and enter interface configuration mode. Valid interfaces
include physical ports, VLANs, and port channels. The VLAN ID range
is 1 to 4094. The port-channel range is 1 to 48.
Step 4
spanning-tree link-type point-to-point
(Recommended for rapid-PVST+ mode only) Specify that the link type
for this port is point-to-point.
If you connect this port (local port) to a remote port through a
point-to-point link and the local port becomes a designated port, the
switch negotiates with the remote port and rapidly changes the local
port to the forwarding state.
Step 5
end
Return to privileged EXEC mode.
Step 6
clear spanning-tree detected-protocols
(Recommended for rapid-PVST+ mode only) If any port on the switch
is connected to a port on a legacy IEEE 802.1D switch, restart the
protocol migration process on the entire switch.
This step is optional if the designated switch detects that this switch is
running rapid PVST+.
Step 7
show spanning-tree summary
Verify your entries.
and
show spanning-tree interface
interface-id
Step 8
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To return to the default setting, use the no spanning-tree mode global configuration command. To return
the port to its default setting, use the no spanning-tree link-type interface configuration command.
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Disabling Spanning Tree
Spanning tree is enabled by default on VLAN 1 and on all newly created VLANs up to the spanning-tree
limit specified in the “Supported Spanning-Tree Instances” section on page 17-9. Disable spanning tree
only if you are sure there are no loops in the network topology.
Caution
When spanning tree is disabled and loops are present in the topology, excessive traffic and indefinite
packet duplication can drastically reduce network performance.
Beginning in privileged EXEC mode, follow these steps to disable spanning-tree on a per-VLAN basis.
This procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
no spanning-tree vlan vlan-id
For vlan-id, the range is 1 to 4094.
Step 3
end
Return to privileged EXEC mode.
Step 4
show spanning-tree vlan vlan-id
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To re-enable spanning-tree, use the spanning-tree vlan vlan-id global configuration command.
Configuring the Root Switch
The switch maintains a separate spanning-tree instance for each active VLAN configured on it. A bridge
ID, consisting of the switch priority and the switch MAC address, is associated with each instance. For
each VLAN, the switch with the lowest bridge ID becomes the root switch for that VLAN.
To configure a switch to become the root for the specified VLAN, use the spanning-tree vlan vlan-id
root global configuration command to modify the switch priority from the default value (32768) to a
significantly lower value. When you enter this command, the software checks the switch priority of the
root switches for each VLAN. Because of the extended system ID support, the switch sets its own
priority for the specified VLAN to 24576 if this value will cause this switch to become the root for the
specified VLAN.
If any root switch for the specified VLAN has a switch priority lower than 24576, the switch sets its own
priority for the specified VLAN to 4096 less than the lowest switch priority. (4096 is the value of the
least-significant bit of a 4-bit switch priority value as shown in Table 17-1 on page 17-4.)
Note
The spanning-tree vlan vlan-id root global configuration command fails if the value necessary to be the
root switch is less than 1.
Note
If your network consists of switches that both do and do not support the extended system ID, it is unlikely
that the switch with the extended system ID support will become the root switch. The extended system
ID increases the switch priority value every time the VLAN number is greater than the priority of the
connected switches running older software.
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Note
The root switch for each spanning-tree instance should be a backbone or distribution switch. Do not
configure an access switch as the spanning-tree primary root.
Use the diameter keyword to specify the Layer 2 network diameter (that is, the maximum number of
switch hops between any two end stations in the Layer 2 network). When you specify the network
diameter, the switch automatically sets an optimal hello time, forward-delay time, and maximum-age
time for a network of that diameter, which can significantly reduce the convergence time. You can use
the hello keyword to override the automatically calculated hello time.
Note
After configuring the switch as the root switch, we recommend that you avoid manually configuring the
hello time, forward-delay time, and maximum-age time through the spanning-tree vlan vlan-id
hello-time, spanning-tree vlan vlan-id forward-time, and the spanning-tree vlan vlan-id max-age
global configuration commands.
Beginning in privileged EXEC mode, follow these steps to configure a switch to become the root for the
specified VLAN. This procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
spanning-tree vlan vlan-id root primary
[diameter net-diameter [hello-time seconds]]
Configure a switch to become the root for the specified VLAN.
•
For vlan-id, you can specify a single VLAN identified by
VLAN ID number, a range of VLANs separated by a
hyphen, or a series of VLANs separated by a comma. The
range is 1 to 4094.
•
(Optional) For diameter net-diameter, specify the
maximum number of switches between any two end
stations. The range is 2 to 7.
•
(Optional) For hello-time seconds, specify the interval in
seconds between the generation of configuration messages
by the root switch. The range is 1 to 10; the default is 2.
Step 3
end
Return to privileged EXEC mode.
Step 4
show spanning-tree detail
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To return to the default setting, use the no spanning-tree vlan vlan-id root global configuration
command.
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Configuring a Secondary Root Switch
When you configure a switch as the secondary root, the switch priority is modified from the default value
(32768) to 28672. The switch is then likely to become the root switch for the specified VLAN if the
primary root switch fails. This is assuming that the other network switches use the default switch priority
of 32768 and therefore are unlikely to become the root switch.
You can execute this command on more than one switch to configure multiple backup root switches. Use
the same network diameter and hello-time values that you used when you configured the primary root
switch with the spanning-tree vlan vlan-id root primary global configuration command.
Beginning in privileged EXEC mode, follow these steps to configure a switch to become the secondary
root for the specified VLAN. This procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
spanning-tree vlan vlan-id root secondary
[diameter net-diameter [hello-time
seconds]]
Configure a switch to become the secondary root for the specified
VLAN.
•
For vlan-id, you can specify a single VLAN identified by VLAN
ID number, a range of VLANs separated by a hyphen, or a series
of VLANs separated by a comma. The range is 1 to 4094.
•
(Optional) For diameter net-diameter, specify the maximum
number of switches between any two end stations. The range is
2 to 7.
•
(Optional) For hello-time seconds, specify the interval in
seconds between the generation of configuration messages by
the root switch. The range is 1 to 10; the default is 2.
Use the same network diameter and hello-time values that you used
when configuring the primary root switch. See the “Configuring the
Root Switch” section on page 17-14.
Step 3
end
Return to privileged EXEC mode.
Step 4
show spanning-tree detail
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To return to the default setting, use the no spanning-tree vlan vlan-id root global configuration
command.
Configuring Port Priority
If a loop occurs, spanning tree uses the port priority when selecting an interface to put into the
forwarding state. You can assign higher priority values (lower numerical values) to interfaces that you
want selected first and lower priority values (higher numerical values) that you want selected last. If all
interfaces have the same priority value, spanning tree puts the interface with the lowest interface number
in the forwarding state and blocks the other interfaces.
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Beginning in privileged EXEC mode, follow these steps to configure the port priority of an interface.
This procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify an interface to configure, and enter interface
configuration mode.
Valid interfaces include physical ports and port-channel
logical interfaces (port-channel port-channel-number).
Step 3
spanning-tree port-priority priority
Configure the port priority for an interface.
For priority, the range is 0 to 240, in increments of 16; the
default is 128. Valid values are 0, 16, 32, 48, 64, 80, 96,
112, 128, 144, 160, 176, 192, 208, 224, and 240. All other
values are rejected. The lower the number, the higher the
priority.
Step 4
spanning-tree vlan vlan-id port-priority priority
Configure the port priority for a VLAN.
•
For vlan-id, you can specify a single VLAN identified
by VLAN ID number, a range of VLANs separated by
a hyphen, or a series of VLANs separated by a comma.
The range is 1 to 4094.
•
For priority, the range is 0 to 240, in increments of 16;
the default is 128. Valid values are 0, 16, 32, 48, 64, 80,
96, 112, 128, 144, 160, 176, 192, 208, 224, and 240.
All other values are rejected. The lower the number,
the higher the priority.
Step 5
end
Return to privileged EXEC mode.
Step 6
show spanning-tree interface interface-id
Verify your entries.
or
show spanning-tree vlan vlan-id
Step 7
copy running-config startup-config
Note
(Optional) Save your entries in the configuration file.
The show spanning-tree interface interface-id privileged EXEC command displays information only
if the port is in a link-up operative state. Otherwise, you can use the show running-config interface
privileged EXEC command to confirm the configuration.
To return to the default setting, use the no spanning-tree [vlan vlan-id] port-priority interface
configuration command. For information on how to configure load sharing on trunk ports by using
spanning-tree port priorities, see the “Configuring Trunk Ports for Load Sharing” section on page 12-22.
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Configuring STP
Configuring Spanning-Tree Features
Configuring Path Cost
The spanning-tree path cost default value is derived from the media speed of an interface. If a loop
occurs, spanning tree uses cost when selecting an interface to put in the forwarding state. You can assign
lower cost values to interfaces that you want selected first and higher cost values that you want selected
last. If all interfaces have the same cost value, spanning tree puts the interface with the lowest interface
number in the forwarding state and blocks the other interfaces.
Beginning in privileged EXEC mode, follow these steps to configure the cost of an interface. This
procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Specify an interface to configure, and enter interface
configuration mode. Valid interfaces include physical ports and
port-channel logical interfaces (port-channel
port-channel-number).
Step 3
spanning-tree cost cost
Configure the cost for an interface.
If a loop occurs, spanning tree uses the path cost when selecting
an interface to place into the forwarding state. A lower path cost
represents higher-speed transmission.
For cost, the range is 1 to 200000000; the default value is derived
from the media speed of the interface.
Step 4
spanning-tree vlan vlan-id cost cost
Configure the cost for a VLAN.
If a loop occurs, spanning tree uses the path cost when selecting
an interface to place into the forwarding state. A lower path cost
represents higher-speed transmission.
•
For vlan-id, you can specify a single VLAN identified by
VLAN ID number, a range of VLANs separated by a hyphen,
or a series of VLANs separated by a comma. The range is 1
to 4094.
•
For cost, the range is 1 to 200000000; the default value is
derived from the media speed of the interface.
Step 5
end
Return to privileged EXEC mode.
Step 6
show spanning-tree interface interface-id
Verify your entries.
or
show spanning-tree vlan vlan-id
Step 7
copy running-config startup-config
Note
(Optional) Save your entries in the configuration file.
The show spanning-tree interface interface-id privileged EXEC command displays information only
for ports that are in a link-up operative state. Otherwise, you can use the show running-config privileged
EXEC command to confirm the configuration.
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Configuring Spanning-Tree Features
To return to the default setting, use the no spanning-tree [vlan vlan-id] cost interface configuration
command. For information on how to configure load sharing on trunk ports by using spanning-tree path
costs, see the “Configuring Trunk Ports for Load Sharing” section on page 12-22.
Configuring the Switch Priority of a VLAN
You can configure the switch priority and make it more likely that the switch will be chosen as the
root switch.
Note
Exercise care when using this command. For most situations, we recommend that you use the
spanning-tree vlan vlan-id root primary and the spanning-tree vlan vlan-id root secondary global
configuration commands to modify the switch priority.
Beginning in privileged EXEC mode, follow these steps to configure the switch priority of a VLAN. This
procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
spanning-tree vlan vlan-id priority priority
Configure the switch priority of a VLAN.
•
For vlan-id, you can specify a single VLAN identified by
VLAN ID number, a range of VLANs separated by a
hyphen, or a series of VLANs separated by a comma. The
range is 1 to 4094.
•
For priority, the range is 0 to 61440 in increments of
4096; the default is 32768. The lower the number, the
more likely the switch will be chosen as the root switch.
Valid priority values are 4096, 8192, 12288, 16384,
20480, 24576, 28672, 32768, 36864, 40960, 45056,
49152, 53248, 57344, and 61440. All other values are
rejected.
Step 3
end
Return to privileged EXEC mode.
Step 4
show spanning-tree vlan vlan-id
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To return to the default setting, use the no spanning-tree vlan vlan-id priority global configuration
command.
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Configuring Spanning-Tree Features
Configuring Spanning-Tree Timers
Table 17-4 describes the timers that affect the entire spanning-tree performance.
Table 17-4
Spanning-Tree Timers
Variable
Description
Hello timer
Controls how often the switch broadcasts hello messages to other switches.
Forward-delay timer
Controls how long each of the listening and learning states last before the interface begins
forwarding.
Maximum-age timer
Controls the amount of time the switch stores protocol information received on an interface.
Transmit hold count
Controls the number of BPDUs that can be sent before pausing for 1 second.
The sections that follow provide the configuration steps.
Configuring the Hello Time
You can configure the interval between the generation of configuration messages by the root switch by
changing the hello time.
Note
Exercise care when using this command. For most situations, we recommend that you use the
spanning-tree vlan vlan-id root primary and the spanning-tree vlan vlan-id root secondary global
configuration commands to modify the hello time.
Beginning in privileged EXEC mode, follow these steps to configure the hello time of a VLAN. This
procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
spanning-tree vlan vlan-id hello-time seconds
Configure the hello time of a VLAN. The hello time is the
interval between the generation of configuration messages by
the root switch. These messages mean that the switch is alive.
•
For vlan-id, you can specify a single VLAN identified by
VLAN ID number, a range of VLANs separated by a
hyphen, or a series of VLANs separated by a comma. The
range is 1 to 4094.
•
For seconds, the range is 1 to 10; the default is 2.
Step 3
end
Return to privileged EXEC mode.
Step 4
show spanning-tree vlan vlan-id
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To return to the default setting, use the no spanning-tree vlan vlan-id hello-time global configuration
command.
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Configuring STP
Configuring Spanning-Tree Features
Configuring the Forwarding-Delay Time for a VLAN
Beginning in privileged EXEC mode, follow these steps to configure the forwarding-delay time for a
VLAN. This procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
spanning-tree vlan vlan-id forward-time
seconds
Configure the forward time of a VLAN. The forward delay is the
number of seconds an interface waits before changing from its
spanning-tree learning and listening states to the forwarding state.
•
For vlan-id, you can specify a single VLAN identified by
VLAN ID number, a range of VLANs separated by a hyphen,
or a series of VLANs separated by a comma. The range is 1 to
4094.
•
For seconds, the range is 4 to 30; the default is 15.
Step 3
end
Return to privileged EXEC mode.
Step 4
show spanning-tree vlan vlan-id
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To return to the default setting, use the no spanning-tree vlan vlan-id forward-time global
configuration command.
Configuring the Maximum-Aging Time for a VLAN
Beginning in privileged EXEC mode, follow these steps to configure the maximum-aging time for a
VLAN. This procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
spanning-tree vlan vlan-id max-age seconds
Configure the maximum-aging time of a VLAN. The
maximum-aging time is the number of seconds a switch waits
without receiving spanning-tree configuration messages before
attempting a reconfiguration.
•
For vlan-id, you can specify a single VLAN identified by
VLAN ID number, a range of VLANs separated by a
hyphen, or a series of VLANs separated by a comma. The
range is 1 to 4094.
•
For seconds, the range is 6 to 40; the default is 20.
Step 3
end
Return to privileged EXEC mode.
Step 4
show spanning-tree vlan vlan-id
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To return to the default setting, use the no spanning-tree vlan vlan-id max-age global configuration
command.
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Displaying the Spanning-Tree Status
Configuring the Transmit Hold-Count
You can configure the BPDU burst size by changing the transmit hold count value.
Note
Changing this parameter to a higher value can have a significant impact on CPU utilization, especially
in Rapid-PVST mode. Lowering this value can slow down convergence in certain scenarios. We
recommend that you maintain the default setting.
Beginning in privileged EXEC mode, follow these steps to configure the transmit hold-count. This
procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
spanning-tree transmit hold-count value
Configure the number of BPDUs that can be sent before pausing
for 1 second.
For value, the range is 1 to 20; the default is 6.
Step 3
end
Return to privileged EXEC mode.
Step 4
show spanning-tree detail
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To return to the default setting, use the no spanning-tree transmit hold-count value global
configuration command.
Displaying the Spanning-Tree Status
To display the spanning-tree status, use one or more of the privileged EXEC commands in Table 17-5:
Table 17-5
Commands for Displaying Spanning-Tree Status
Command
Purpose
show spanning-tree active
Displays spanning-tree information on active interfaces only.
show spanning-tree detail
Displays a detailed summary of interface information.
show spanning-tree interface interface-id
Displays spanning-tree information for the specified interface.
show spanning-tree summary [totals]
Displays a summary of interface states or displays the total lines of the STP
state section.
You can clear spanning-tree counters by using the clear spanning-tree [interface interface-id]
privileged EXEC command.
For information about other keywords for the show spanning-tree privileged EXEC command, see the
command reference for this release.
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18
Configuring MSTP
This chapter describes how to configure the Cisco implementation of the IEEE 802.1s Multiple
STP (MSTP) on the switch.
Note
The multiple spanning-tree (MST) implementation in Cisco IOS Release 12.2(37)SE is based on the
IEEE 802.1s standard.
The MSTP enables multiple VLANs to be mapped to the same spanning-tree instance, reducing the
number of spanning-tree instances needed to support a large number of VLANs. The MSTP provides for
multiple forwarding paths for data traffic and enables load balancing. It improves the fault tolerance of
the network because a failure in one instance (forwarding path) does not affect other instances
(forwarding paths). The most common initial deployment of MSTP is in the backbone and distribution
layers of a Layer 2 switched network. This deployment provides the highly available network required
in a service-provider environment.
When the switch is in the MST mode, the Rapid Spanning Tree Protocol (RSTP), which is based on
IEEE 802.1w, is automatically enabled. The RSTP provides rapid convergence of the spanning tree
through explicit handshaking that eliminates the IEEE 802.1D forwarding delay and quickly transitions
root ports and designated ports to the forwarding state.
Both MSTP and RSTP improve the spanning-tree operation and maintain backward compatibility with
equipment that is based on the (original) IEEE 802.1D spanning tree, with existing Cisco-proprietary
Multiple Instance STP (MISTP), and with existing Cisco per-VLAN spanning-tree plus (PVST+) and
rapid per-VLAN spanning-tree plus (rapid PVST+). For information about PVST+ and rapid PVST+,
see Chapter 17, “Configuring STP.” For information about other spanning-tree features such as Port Fast,
UplinkFast, root guard, and so forth, see Chapter 19, “Configuring Optional Spanning-Tree Features.”
Note
For complete syntax and usage information for the commands used in this chapter, see the command
reference for this release.
This chapter consists of these sections:
•
Understanding MSTP, page 18-2
•
Understanding RSTP, page 18-8
•
Configuring MSTP Features, page 18-14
•
Displaying the MST Configuration and Status, page 18-26
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Understanding MSTP
Understanding MSTP
MSTP, which uses RSTP for rapid convergence, enables VLANs to be grouped into a spanning-tree
instance, with each instance having a spanning-tree topology independent of other spanning-tree
instances. This architecture provides multiple forwarding paths for data traffic, enables load balancing,
and reduces the number of spanning-tree instances required to support a large number of VLANs.
These sections describe how the MSTP works:
•
Multiple Spanning-Tree Regions, page 18-2
•
IST, CIST, and CST, page 18-3
•
Hop Count, page 18-5
•
Boundary Ports, page 18-6
•
IEEE 802.1s Implementation, page 18-6
•
Interoperability with IEEE 802.1D STP, page 18-8
For configuration information, see the “Configuring MSTP Features” section on page 18-14.
Multiple Spanning-Tree Regions
For switches to participate in multiple spanning-tree (MST) instances, you must consistently configure
the switches with the same MST configuration information. A collection of interconnected switches that
have the same MST configuration comprises an MST region as shown in Figure 18-1 on page 18-4.
The MST configuration controls to which MST region each switch belongs. The configuration includes
the name of the region, the revision number, and the MST VLAN-to-instance assignment map. You
configure the switch for a region by using the spanning-tree mst configuration global configuration
command, after which the switch enters the MST configuration mode. From this mode, you can map
VLANs to an MST instance by using the instance MST configuration command, specify the region name
by using the name MST configuration command, and set the revision number by using the revision MST
configuration command.
A region can have one or multiple members with the same MST configuration. Each member must be
capable of processing RSTP bridge protocol data units (BPDUs). There is no limit to the number of MST
regions in a network, but each region can support up to 65 spanning-tree instances. Instances can be
identified by any number in the range from 0 to 4094. You can assign a VLAN to only one spanning-tree
instance at a time.
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Understanding MSTP
IST, CIST, and CST
Unlike PVST+ and rapid PVST+ in which all the spanning-tree instances are independent, the MSTP
establishes and maintains two types of spanning trees:
•
An internal spanning tree (IST), which is the spanning tree that runs in an MST region.
Within each MST region, the MSTP maintains multiple spanning-tree instances. Instance 0 is a
special instance for a region, known as the internal spanning tree (IST). All other MST instances are
numbered from 1 to 4094.
The IST is the only spanning-tree instance that sends and receives BPDUs. All of the other
spanning-tree instance information is contained in M-records, which are encapsulated within MSTP
BPDUs. Because the MSTP BPDU carries information for all instances, the number of BPDUs that
need to be processed to support multiple spanning-tree instances is significantly reduced.
All MST instances within the same region share the same protocol timers, but each MST instance
has its own topology parameters, such as root switch ID, root path cost, and so forth. By default, all
VLANs are assigned to the IST.
An MST instance is local to the region; for example, MST instance 1 in region A is independent of
MST instance 1 in region B, even if regions A and B are interconnected.
•
A common and internal spanning tree (CIST), which is a collection of the ISTs in each MST region,
and the common spanning tree (CST) that interconnects the MST regions and single spanning trees.
The spanning tree computed in a region appears as a subtree in the CST that encompasses the entire
switched domain. The CIST is formed by the spanning-tree algorithm running among switches that
support the IEEE 802.1w, IEEE 802.1s, and IEEE 802.1D standards. The CIST inside an MST
region is the same as the CST outside a region.
For more information, see the “Operations Within an MST Region” section on page 18-3 and the
“Operations Between MST Regions” section on page 18-4.
Note
The implementation of the IEEE 802.1s standard, changes some of the terminology associated with MST
implementations. For a summary of these changes, see Table 17-1 on page 17-4.
Operations Within an MST Region
The IST connects all the MSTP switches in a region. When the IST converges, the root of the IST
becomes the CIST regional root (called the IST master before the implementation of the IEEE 802.1s
standard) as shown in Figure 18-1 on page 18-4. It is the switch within the region with the lowest switch
ID and path cost to the CIST root. The CIST regional root is also the CIST root if there is only one region
in the network. If the CIST root is outside the region, one of the MSTP switches at the boundary of the
region is selected as the CIST regional root.
When an MSTP switch initializes, it sends BPDUs claiming itself as the root of the CIST and the CIST
regional root, with both of the path costs to the CIST root and to the CIST regional root set to zero. The
switch also initializes all of its MST instances and claims to be the root for all of them. If the switch
receives superior MST root information (lower switch ID, lower path cost, and so forth) than currently
stored for the port, it relinquishes its claim as the CIST regional root.
During initialization, a region might have many subregions, each with its own CIST regional root. As
switches receive superior IST information, they leave their old subregions and join the new subregion
that contains the true CIST regional root. Thus all subregions shrink, except for the one that contains the
true CIST regional root.
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For correct operation, all switches in the MST region must agree on the same CIST regional root.
Therefore, any two switches in the region only synchronize their port roles for an MST instance if they
converge to a common CIST regional root.
Operations Between MST Regions
If there are multiple regions or legacy IEEE 802.1D switches within the network, MSTP establishes and
maintains the CST, which includes all MST regions and all legacy STP switches in the network. The
MST instances combine with the IST at the boundary of the region to become the CST.
The IST connects all the MSTP switches in the region and appears as a subtree in the CIST that
encompasses the entire switched domain. The root of the subtree is the CIST regional root. The MST
region appears as a virtual switch to adjacent STP switches and MST regions.
Figure 18-1 shows a network with three MST regions and a legacy IEEE 802.1D switch (D). The CIST
regional root for region 1 (A) is also the CIST root. The CIST regional root for region 2 (B) and the CIST
regional root for region 3 (C) are the roots for their respective subtrees within the CIST. The RSTP runs
in all regions.
Figure 18-1
MST Regions, CIST Masters, and CST Root
A IST master
and CST root
D
Legacy IEEE 802.1D
MST Region 1
IST master
MST Region 2
C
IST master
MST Region 3
92983
B
Only the CST instance sends and receives BPDUs, and MST instances add their spanning-tree
information into the BPDUs to interact with neighboring switches and compute the final spanning-tree
topology. Because of this, the spanning-tree parameters related to BPDU transmission (for example,
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hello time, forward time, max-age, and max-hops) are configured only on the CST instance but affect all
MST instances. Parameters related to the spanning-tree topology (for example, switch priority, port
VLAN cost, and port VLAN priority) can be configured on both the CST instance and the MST instance.
MSTP switches use Version 3 RSTP BPDUs or IEEE 802.1D STP BPDUs to communicate with legacy
IEEE 802.1D switches. MSTP switches use MSTP BPDUs to communicate with MSTP switches.
IEEE 802.1s Terminology
Some MST naming conventions used in Cisco’s prestandard implementation have been changed to
identify some internal or regional parameters. These parameters are significant only within an MST
region, as opposed to external parameters that are relevant to the whole network. Because the CIST is
the only spanning-tree instance that spans the whole network, only the CIST parameters require the
external rather than the internal or regional qualifiers.
•
The CIST root is the root switch for the unique instance that spans the whole network, the CIST.
•
The CIST external root path cost is the cost to the CIST root. This cost is left unchanged within an
MST region. Remember that an MST region looks like a single switch for the CIST. The CIST
external root path cost is the root path cost calculated between these virtual switches and switches
that do not belong to any region.
•
The CIST regional root was called the IST master in the prestandard implementation. If the CIST
root is in the region, the CIST regional root is the CIST root. Otherwise, the CIST regional root is
the closest switch to the CIST root in the region. The CIST regional root acts as a root switch for
the IST.
•
The CIST internal root path cost is the cost to the CIST regional root in a region. This cost is only
relevant to the IST, instance 0.
Table 18-1 on page 18-5 compares the IEEE standard and the Cisco prestandard terminology.
Table 18-1
Prestandard and Standard Terminology
IEEE Standard
Cisco Prestandard
Cisco Standard
CIST regional root
IST master
CIST regional root
CIST internal root path cost
IST master path cost
CIST internal path cost
CIST external root path cost
Root path cost
Root path cost
MSTI regional root
Instance root
Instance root
MSTI internal root path cost
Root path cost
Root path cost
Hop Count
The IST and MST instances do not use the message-age and maximum-age information in the
configuration BPDU to compute the spanning-tree topology. Instead, they use the path cost to the root
and a hop-count mechanism similar to the IP time-to-live (TTL) mechanism.
By using the spanning-tree mst max-hops global configuration command, you can configure the
maximum hops inside the region and apply it to the IST and all MST instances in that region. The hop
count achieves the same result as the message-age information (triggers a reconfiguration). The root
switch of the instance always sends a BPDU (or M-record) with a cost of 0 and the hop count set to the
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maximum value. When a switch receives this BPDU, it decrements the received remaining hop count by
one and propagates this value as the remaining hop count in the BPDUs it generates. When the count
reaches zero, the switch discards the BPDU and ages the information held for the port.
The message-age and maximum-age information in the RSTP portion of the BPDU remain the same
throughout the region, and the same values are propagated by the region designated ports at the
boundary.
Boundary Ports
In the Cisco prestandard implementation, a boundary port connects an MST region to a single
spanning-tree region running RSTP, to a single spanning-tree region running PVST+ or rapid PVST+,
or to another MST region with a different MST configuration. A boundary port also connects to a LAN,
the designated switch of which is either a single spanning-tree switch or a switch with a different MST
configuration.
There is no definition of a boundary port in the IEEE 802.1s standard. The IEEE 802.1Q-2002 standard
identifies two kinds of messages that a port can receive: internal (coming from the same region) and
external. When a message is external, it is received only by the CIST. If the CIST role is root or alternate,
or if the external BPDU is a topology change, it could have an impact on the MST instances. When a
message is internal, the CIST part is received by the CIST, and each MST instance receives its respective
M-record. The Cisco prestandard implementation treats a port that receives an external message as a
boundary port. This means a port cannot receive a mix of internal and external messages.
An MST region includes both switches and LANs. A segment belongs to the region of its designated
port. Therefore, a port in a different region than the designated port for a segment is a boundary port.
This definition allows two ports internal to a region to share a segment with a port belonging to a
different region, creating the possibility of receiving both internal and external messages on a port.
The primary change from the Cisco prestandard implementation is that a designated port is not defined
as boundary, unless it is running in an STP-compatible mode.
Note
If there is a legacy STP switch on the segment, messages are always considered external.
The other change from the prestandard implementation is that the CIST regional root switch ID field is
now inserted where an RSTP or legacy IEEE 802.1Q switch has the sender switch ID. The whole region
performs like a single virtual switch by sending a consistent sender switch ID to neighboring switches.
In this example, switch C would receive a BPDU with the same consistent sender switch ID of root,
whether or not A or B is designated for the segment.
IEEE 802.1s Implementation
The Cisco implementation of the IEEE MST standard includes features required to meet the standard, as
well as some of the desirable prestandard functionality that is not yet incorporated into the published
standard.
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Port Role Naming Change
The boundary role is no longer in the final MST standard, but this boundary concept is maintained in
Cisco’s implementation. However, an MST instance port at a boundary of the region might not follow
the state of the corresponding CIST port. Two cases exist now:
•
The boundary port is the root port of the CIST regional root—When the CIST instance port is
proposed and is in sync, it can send back an agreement and move to the forwarding state only after
all the corresponding MSTI ports are in sync (and thus forwarding). The MSTI ports now have a
special master role.
•
The boundary port is not the root port of the CIST regional root—The MSTI ports follow the state
and role of the CIST port. The standard provides less information, and it might be difficult to
understand why an MSTI port can be alternately blocking when it receives no BPDUs (MRecords).
In this case, although the boundary role no longer exists, the show commands identify a port as
boundary in the type column of the output.
Interoperation Between Legacy and Standard Switches
Because automatic detection of prestandard switches can fail, you can use an interface configuration
command to identify prestandard ports. A region cannot be formed between a standard and a prestandard
switch, but they can interoperate by using the CIST. Only the capability of load balancing over different
instances is lost in that particular case. The CLI displays different flags depending on the port
configuration when a port receives prestandard BPDUs. A syslog message also appears the first time a
switch receives a prestandard BPDU on a port that has not been configured for prestandard BPDU
transmission.
Figure 18-2 illustrates this scenario. Assume that A is a standard switch and B a prestandard switch, both
configured to be in the same region. A is the root switch for the CIST, and thus B has a root port (BX)
on segment X and an alternate port (BY) on segment Y. If segment Y flaps, and the port on BY becomes
the alternate before sending out a single prestandard BPDU, AY cannot detect that a prestandard switch
is connected to Y and continues to send standard BPDUs. The port BY is thus fixed in a boundary, and
no load balancing is possible between A and B. The same problem exists on segment X, but B might
transmit topology changes.
Figure 18-2
Standard and Prestandard Switch Interoperation
Segment X
MST
Region
Switch A
Segment Y
Note
92721
Switch B
We recommend that you minimize the interaction between standard and prestandard MST
implementations.
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Detecting Unidirectional Link Failure
This feature is not yet present in the IEEE MST standard, but it is included in this Cisco IOS release.
The software checks the consistency of the port role and state in the received BPDUs to detect
unidirectional link failures that could cause bridging loops.
When a designated port detects a conflict, it keeps its role, but reverts to discarding state because
disrupting connectivity in case of inconsistency is preferable to opening a bridging loop.
Figure 18-3 illustrates a unidirectional link failure that typically creates a bridging loop. Switch A is the
root switch, and its BPDUs are lost on the link leading to switch B. RSTP and MST BPDUs include the
role and state of the sending port. With this information, switch A can detect that switch B does not react
to the superior BPDUs it sends and that switch B is the designated, not root switch. As a result, switch
A blocks (or keeps blocking) its port, thus preventing the bridging loop.
Switch
A
Detecting Unidirectional Link Failure
Superior
BPDU
Switch
B
Inferior BPDU,
Designated + Learning bit set
92722
Figure 18-3
Interoperability with IEEE 802.1D STP
A switch running MSTP supports a built-in protocol migration mechanism that enables it to interoperate
with legacy IEEE 802.1D switches. If this switch receives a legacy IEEE 802.1D configuration BPDU
(a BPDU with the protocol version set to 0), it sends only IEEE 802.1D BPDUs on that port. An MSTP
switch also can detect that a port is at the boundary of a region when it receives a legacy BPDU, an MSTP
BPDU (Version 3) associated with a different region, or an RSTP BPDU (Version 2).
However, the switch does not automatically revert to the MSTP mode if it no longer receives
IEEE 802.1D BPDUs because it cannot detect whether the legacy switch has been removed from the link
unless the legacy switch is the designated switch. A switch might also continue to assign a boundary role
to a port when the switch to which this switch is connected has joined the region. To restart the protocol
migration process (force the renegotiation with neighboring switches), use the clear spanning-tree
detected-protocols privileged EXEC command.
If all the legacy switches on the link are RSTP switches, they can process MSTP BPDUs as if they are
RSTP BPDUs. Therefore, MSTP switches send either a Version 0 configuration and TCN BPDUs or
Version 3 MSTP BPDUs on a boundary port. A boundary port connects to a LAN, the designated switch
of which is either a single spanning-tree switch or a switch with a different MST configuration.
Understanding RSTP
The RSTP takes advantage of point-to-point wiring and provides rapid convergence of the spanning tree.
Reconfiguration of the spanning tree can occur in less than 1 second (in contrast to 50 seconds with the
default settings in the IEEE 802.1D spanning tree).
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These sections describe how the RSTP works:
•
Port Roles and the Active Topology, page 18-9
•
Rapid Convergence, page 18-10
•
Synchronization of Port Roles, page 18-11
•
Bridge Protocol Data Unit Format and Processing, page 18-12
For configuration information, see the “Configuring MSTP Features” section on page 18-14.
Port Roles and the Active Topology
The RSTP provides rapid convergence of the spanning tree by assigning port roles and by learning the
active topology. The RSTP builds upon the IEEE 802.1D STP to select the switch with the highest switch
priority (lowest numerical priority value) as the root switch as described in the “Spanning-Tree Topology
and BPDUs” section on page 17-3. Then the RSTP assigns one of these port roles to individual ports:
•
Root port—Provides the best path (lowest cost) when the switch forwards packets to the root switch.
•
Designated port—Connects to the designated switch, which incurs the lowest path cost when
forwarding packets from that LAN to the root switch. The port through which the designated switch
is attached to the LAN is called the designated port.
•
Alternate port—Offers an alternate path toward the root switch to that provided by the current root
port.
•
Backup port—Acts as a backup for the path provided by a designated port toward the leaves of the
spanning tree. A backup port can exist only when two ports are connected in a loopback by a
point-to-point link or when a switch has two or more connections to a shared LAN segment.
•
Disabled port—Has no role within the operation of the spanning tree.
A port with the root or a designated port role is included in the active topology. A port with the alternate
or backup port role is excluded from the active topology.
In a stable topology with consistent port roles throughout the network, the RSTP ensures that every root
port and designated port immediately transition to the forwarding state while all alternate and backup
ports are always in the discarding state (equivalent to blocking in IEEE 802.1D). The port state controls
the operation of the forwarding and learning processes. Table 18-2 provides a comparison of
IEEE 802.1D and RSTP port states.
Table 18-2
Port State Comparison
Operational Status
STP Port State
(IEEE 802.1D)
RSTP Port State
Is Port Included in the
Active Topology?
Enabled
Blocking
Discarding
No
Enabled
Listening
Discarding
No
Enabled
Learning
Learning
Yes
Enabled
Forwarding
Forwarding
Yes
Disabled
Disabled
Discarding
No
To be consistent with Cisco STP implementations, this guide defines the port state as blocking instead
of discarding. Designated ports start in the listening state.
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Understanding RSTP
Rapid Convergence
The RSTP provides for rapid recovery of connectivity following the failure of a switch, a switch port, or
a LAN. It provides rapid convergence for edge ports, new root ports, and ports connected through
point-to-point links as follows:
•
Edge ports—If you configure a port as an edge port on an RSTP switch by using the spanning-tree
portfast interface configuration command, the edge port immediately transitions to the forwarding
state. An edge port is the same as a Port Fast-enabled port, and you should enable it only on ports
that connect to a single end station.
•
Root ports—If the RSTP selects a new root port, it blocks the old root port and immediately
transitions the new root port to the forwarding state.
•
Point-to-point links—If you connect a port to another port through a point-to-point link and the local
port becomes a designated port, it negotiates a rapid transition with the other port by using the
proposal-agreement handshake to ensure a loop-free topology.
As shown in Figure 18-4, Switch A is connected to Switch B through a point-to-point link, and all
of the ports are in the blocking state. Assume that the priority of Switch A is a smaller numerical
value than the priority of Switch B. Switch A sends a proposal message (a configuration BPDU with
the proposal flag set) to Switch B, proposing itself as the designated switch.
After receiving the proposal message, Switch B selects as its new root port the port from which the
proposal message was received, forces all nonedge ports to the blocking state, and sends an
agreement message (a BPDU with the agreement flag set) through its new root port.
After receiving Switch B’s agreement message, Switch A also immediately transitions its designated
port to the forwarding state. No loops in the network are formed because Switch B blocked all of its
nonedge ports and because there is a point-to-point link between Switches A and B.
When Switch C is connected to Switch B, a similar set of handshaking messages are exchanged.
Switch C selects the port connected to Switch B as its root port, and both ends immediately
transition to the forwarding state. With each iteration of this handshaking process, one more switch
joins the active topology. As the network converges, this proposal-agreement handshaking
progresses from the root toward the leaves of the spanning tree.
The switch learns the link type from the port duplex mode: a full-duplex port is considered to have
a point-to-point connection; a half-duplex port is considered to have a shared connection. You can
override the default setting that is controlled by the duplex setting by using the spanning-tree
link-type interface configuration command.
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Figure 18-4
Proposal and Agreement Handshaking for Rapid Convergence
Switch A
Proposal
Switch B
Root
Agreement
Designated
switch
F
DP
F
RP
Root
F
DP
Proposal
Designated
switch
Agreement
F
RP
Root
F
DP
Designated
switch
F
RP
F
DP
Switch C
F
RP
88760
DP = designated port
RP = root port
F = forwarding
Synchronization of Port Roles
When the switch receives a proposal message on one of its ports and that port is selected as the new root
port, the RSTP forces all other ports to synchronize with the new root information.
The switch is synchronized with superior root information received on the root port if all other ports are
synchronized. An individual port on the switch is synchronized if
•
That port is in the blocking state.
•
It is an edge port (a port configured to be at the edge of the network).
If a designated port is in the forwarding state and is not configured as an edge port, it transitions to the
blocking state when the RSTP forces it to synchronize with new root information. In general, when the
RSTP forces a port to synchronize with root information and the port does not satisfy any of the above
conditions, its port state is set to blocking.
After ensuring that all of the ports are synchronized, the switch sends an agreement message to the
designated switch corresponding to its root port. When the switches connected by a point-to-point link
are in agreement about their port roles, the RSTP immediately transitions the port states to forwarding.
The sequence of events is shown in Figure 18-5.
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Figure 18-5
Sequence of Events During Rapid Convergence
4. Agreement
1. Proposal
5. Forward
Edge port
3. Block
11. Forward
8. Agreement
7. Proposal
6. Proposal
10. Agreement
Root port
Designated port
88761
2. Block
9. Forward
Bridge Protocol Data Unit Format and Processing
The RSTP BPDU format is the same as the IEEE 802.1D BPDU format except that the protocol version
is set to 2. A new 1-byte Version 1 Length field is set to zero, which means that no version 1 protocol
information is present. Table 18-3 shows the RSTP flag fields.
Table 18-3
RSTP BPDU Flags
Bit
Function
0
Topology change (TC)
1
Proposal
2–3:
Port role:
00
Unknown
01
Alternate port
10
Root port
11
Designated port
4
Learning
5
Forwarding
6
Agreement
7
Topology change acknowledgement (TCA)
The sending switch sets the proposal flag in the RSTP BPDU to propose itself as the designated switch
on that LAN. The port role in the proposal message is always set to the designated port.
The sending switch sets the agreement flag in the RSTP BPDU to accept the previous proposal. The port
role in the agreement message is always set to the root port.
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The RSTP does not have a separate topology change notification (TCN) BPDU. It uses the topology
change (TC) flag to show the topology changes. However, for interoperability with IEEE 802.1D
switches, the RSTP switch processes and generates TCN BPDUs.
The learning and forwarding flags are set according to the state of the sending port.
Processing Superior BPDU Information
If a port receives superior root information (lower switch ID, lower path cost, and so forth) than currently
stored for the port, the RSTP triggers a reconfiguration. If the port is proposed and is selected as the new
root port, RSTP forces all the other ports to synchronize.
If the BPDU received is an RSTP BPDU with the proposal flag set, the switch sends an agreement
message after all of the other ports are synchronized. If the BPDU is an IEEE 802.1D BPDU, the switch
does not set the proposal flag and starts the forward-delay timer for the port. The new root port requires
twice the forward-delay time to transition to the forwarding state.
If the superior information received on the port causes the port to become a backup or alternate port,
RSTP sets the port to the blocking state but does not send the agreement message. The designated port
continues sending BPDUs with the proposal flag set until the forward-delay timer expires, at which time
the port transitions to the forwarding state.
Processing Inferior BPDU Information
If a designated port receives an inferior BPDU (higher switch ID, higher path cost, and so forth than
currently stored for the port) with a designated port role, it immediately replies with its own information.
Topology Changes
This section describes the differences between the RSTP and the IEEE 802.1D in handling spanning-tree
topology changes.
•
Detection—Unlike IEEE 802.1D in which any transition between the blocking and the forwarding
state causes a topology change, only transitions from the blocking to the forwarding state cause a
topology change with RSTP (only an increase in connectivity is considered a topology change).
State changes on an edge port do not cause a topology change. When an RSTP switch detects a
topology change, it deletes the learned information on all of its nonedge ports except on those from
which it received the TC notification.
•
Notification—Unlike IEEE 802.1D, which uses TCN BPDUs, the RSTP does not use them.
However, for IEEE 802.1D interoperability, an RSTP switch processes and generates TCN BPDUs.
•
Acknowledgement—When an RSTP switch receives a TCN message on a designated port from an
IEEE 802.1D switch, it replies with an IEEE 802.1D configuration BPDU with the TCA bit set.
However, if the TC-while timer (the same as the topology-change timer in IEEE 802.1D) is active
on a root port connected to an IEEE 802.1D switch and a configuration BPDU with the TCA bit set
is received, the TC-while timer is reset.
This behavior is only required to support IEEE 802.1D switches. The RSTP BPDUs never have the
TCA bit set.
•
Propagation—When an RSTP switch receives a TC message from another switch through a
designated or root port, it propagates the change to all of its nonedge, designated ports and to the
root port (excluding the port on which it is received). The switch starts the TC-while timer for all
such ports and flushes the information learned on them.
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•
Protocol migration—For backward compatibility with IEEE 802.1D switches, RSTP selectively
sends IEEE 802.1D configuration BPDUs and TCN BPDUs on a per-port basis.
When a port is initialized, the migrate-delay timer is started (specifies the minimum time during
which RSTP BPDUs are sent), and RSTP BPDUs are sent. While this timer is active, the switch
processes all BPDUs received on that port and ignores the protocol type.
If the switch receives an IEEE 802.1D BPDU after the port migration-delay timer has expired, it
assumes that it is connected to an IEEE 802.1D switch and starts using only IEEE 802.1D BPDUs.
However, if the RSTP switch is using IEEE 802.1D BPDUs on a port and receives an RSTP BPDU
after the timer has expired, it restarts the timer and starts using RSTP BPDUs on that port.
Configuring MSTP Features
•
Default MSTP Configuration, page 18-14
•
MSTP Configuration Guidelines, page 18-15
•
Specifying the MST Region Configuration and Enabling MSTP, page 18-16 (required)
•
Configuring the Root Switch, page 18-17 (optional)
•
Configuring a Secondary Root Switch, page 18-19 (optional)
•
Configuring Port Priority, page 18-19 (optional)
•
Configuring Path Cost, page 18-20 (optional)
•
Configuring the Switch Priority, page 18-21 (optional)
•
Configuring the Hello Time, page 18-22 (optional)
•
Configuring the Forwarding-Delay Time, page 18-23 (optional)
•
Configuring the Maximum-Aging Time, page 18-23 (optional)
•
Configuring the Maximum-Hop Count, page 18-24 (optional)
•
Specifying the Link Type to Ensure Rapid Transitions, page 18-24 (optional)
•
Designating the Neighbor Type, page 18-25 (optional)
•
Restarting the Protocol Migration Process, page 18-25 (optional)
Default MSTP Configuration
Table 18-4
Default MSTP Configuration
Feature
Default Setting
Spanning-tree mode
PVST+ (Rapid PVST+ and MSTP are disabled).
Switch priority (configurable on a per-CIST port basis)
32768.
Spanning-tree port priority (configurable on a per-CIST port basis)
128.
Spanning-tree port cost (configurable on a per-CIST port basis)
1000 Mb/s: 4.
100 Mb/s: 19.
10 Mb/s: 100.
Hello time
2 seconds.
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Table 18-4
Default MSTP Configuration (continued)
Feature
Default Setting
Forward-delay time
15 seconds.
Maximum-aging time
20 seconds.
Maximum hop count
20 hops.
For information about the supported number of spanning-tree instances, see the “Supported
Spanning-Tree Instances” section on page 17-9.
MSTP Configuration Guidelines
•
When you enable MST by using the spanning-tree mode mst global configuration command, RSTP
is automatically enabled.
•
For two or more switches to be in the same MST region, they must have the same VLAN-to-instance
map, the same configuration revision number, and the same name.
•
The switch supports up to 65 MST instances. The number of VLANs that can be mapped to a
particular MST instance is unlimited.
•
PVST+, rapid PVST+, and MSTP are supported, but only one version can be active at any time. (For
example, all VLANs run PVST+, all VLANs run rapid PVST+, or all VLANs run MSTP.) For more
information, see the “Spanning-Tree Interoperability and Backward Compatibility” section on
page 17-10. For information on the recommended trunk port configuration, see the “Interaction with
Other Features” section on page 12-18.
•
VTP propagation of the MST configuration is not supported. However, you can manually configure
the MST configuration (region name, revision number, and VLAN-to-instance mapping) on each
switch within the MST region by using the command-line interface (CLI) or through the SNMP
support.
•
For load balancing across redundant paths in the network to work, all VLAN-to-instance mapping
assignments must match; otherwise, all traffic flows on a single link.
•
All MST boundary ports must be forwarding for load balancing between a PVST+ and an MST
cloud or between a rapid-PVST+ and an MST cloud. For this to occur, the IST master of the MST
cloud should also be the root of the CST. If the MST cloud consists of multiple MST regions, one
of the MST regions must contain the CST root, and all of the other MST regions must have a better
path to the root contained within the MST cloud than a path through the PVST+ or rapid-PVST+
cloud. You might have to manually configure the switches in the clouds.
•
Partitioning the network into a large number of regions is not recommended. However, if this
situation is unavoidable, we recommend that you partition the switched LAN into smaller LANs
interconnected by routers or non-Layer 2 devices.
•
For configuration guidelines about UplinkFast and BackboneFast, see the “Optional Spanning-Tree
Configuration Guidelines” section on page 19-10.
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•
When the switch is in MST mode, it uses the long path-cost calculation method (32 bits) to compute
the path cost values. With the long path-cost calculation method, these path cost values are
supported:
Speed
Path Cost Value
10 Mb/s
2,000,000
100 Mb/s
200,000
1 Gb/s
20,000
10 Gb/s
2,000
100 Gb/s
200
Specifying the MST Region Configuration and Enabling MSTP
For two or more switches to be in the same MST region, they must have the same VLAN-to-instance
mapping, the same configuration revision number, and the same name.
A region can have one member or multiple members with the same MST configuration; each member
must be capable of processing RSTP BPDUs. There is no limit to the number of MST regions in a
network, but each region can only support up to 65 spanning-tree instances. You can assign a VLAN to
only one spanning-tree instance at a time.
Beginning in privileged EXEC mode, follow these steps to specify the MST region configuration and
enable MSTP. This procedure is required.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
spanning-tree mst configuration
Enter MST configuration mode.
Step 3
instance instance-id vlan vlan-range
Map VLANs to an MST instance.
•
For instance-id, the range is 0 to 4094.
•
For vlan vlan-range, the range is 1 to 4094.
When you map VLANs to an MST instance, the mapping is
incremental, and the VLANs specified in the command are added to
or removed from the VLANs that were previously mapped.
To specify a VLAN range, use a hyphen; for example, instance 1 vlan
1-63 maps VLANs 1 through 63 to MST instance 1.
To specify a VLAN series, use a comma; for example, instance 1 vlan 10,
20, 30 maps VLANs 10, 20, and 30 to MST instance 1.
Step 4
name name
Specify the configuration name. The name string has a maximum length
of 32 characters and is case sensitive.
Step 5
revision version
Specify the configuration revision number. The range is 0 to 65535.
Step 6
show pending
Verify your configuration by displaying the pending configuration.
Step 7
exit
Apply all changes, and return to global configuration mode.
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Step 8
Command
Purpose
spanning-tree mode mst
Enable MSTP. RSTP is also enabled.
Caution
Changing spanning-tree modes can disrupt traffic because all
spanning-tree instances are stopped for the previous mode and
restarted in the new mode.
You cannot run both MSTP and PVST+ or both MSTP and rapid PVST+
at the same time.
Step 9
end
Return to privileged EXEC mode.
Step 10
show running-config
Verify your entries.
Step 11
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To return to the default MST region configuration, use the no spanning-tree mst configuration global
configuration command. To return to the default VLAN-to-instance map, use the no instance instance-id
[vlan vlan-range] MST configuration command. To return to the default name, use the no name MST
configuration command. To return to the default revision number, use the no revision MST configuration
command. To re-enable PVST+, use the no spanning-tree mode or the spanning-tree mode pvst global
configuration command.
This example shows how to enter MST configuration mode, map VLANs 10 to 20 to MST instance 1,
name the region region1, set the configuration revision to 1, display the pending configuration, apply the
changes, and return to global configuration mode:
Switch(config)# spanning-tree mst configuration
Switch(config-mst)# instance 1 vlan 10-20
Switch(config-mst)# name region1
Switch(config-mst)# revision 1
Switch(config-mst)# show pending
Pending MST configuration
Name
[region1]
Revision 1
Instance Vlans Mapped
-------- --------------------0
1-9,21-4094
1
10-20
------------------------------Switch(config-mst)# exit
Switch(config)#
Configuring the Root Switch
The switch maintains a spanning-tree instance for the group of VLANs mapped to it. A switch ID,
consisting of the switch priority and the switch MAC address, is associated with each instance. For a
group of VLANs, the switch with the lowest switch ID becomes the root switch.
To configure a switch to become the root, use the spanning-tree mst instance-id root global
configuration command to modify the switch priority from the default value (32768) to a significantly
lower value so that the switch becomes the root switch for the specified spanning-tree instance. When
you enter this command, the switch checks the switch priorities of the root switches. Because of the
extended system ID support, the switch sets its own priority for the specified instance to 24576 if this
value will cause this switch to become the root for the specified spanning-tree instance.
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If any root switch for the specified instance has a switch priority lower than 24576, the switch sets its
own priority to 4096 less than the lowest switch priority. (4096 is the value of the least-significant bit of
a 4-bit switch priority value as shown in Table 17-1 on page 17-4.)
If your network consists of switches that both do and do not support the extended system ID, it is unlikely
that the switch with the extended system ID support will become the root switch. The extended system
ID increases the switch priority value every time the VLAN number is greater than the priority of the
connected switches running older software.
The root switch for each spanning-tree instance should be a backbone or distribution switch. Do not
configure an access switch as the spanning-tree primary root.
Use the diameter keyword, which is available only for MST instance 0, to specify the Layer 2 network
diameter (that is, the maximum number of switch hops between any two end stations in the Layer 2
network). When you specify the network diameter, the switch automatically sets an optimal hello time,
forward-delay time, and maximum-age time for a network of that diameter, which can significantly
reduce the convergence time. You can use the hello keyword to override the automatically calculated
hello time.
Note
After configuring the switch as the root switch, we recommend that you avoid manually configuring the
hello time, forward-delay time, and maximum-age time through the spanning-tree mst hello-time,
spanning-tree mst forward-time, and the spanning-tree mst max-age global configuration
commands.
Beginning in privileged EXEC mode, follow these steps to configure a switch as the root switch. This
procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
spanning-tree mst instance-id root primary
[diameter net-diameter [hello-time seconds]]
Configure a switch as the root switch.
•
For instance-id, you can specify a single instance, a range
of instances separated by a hyphen, or a series of instances
separated by a comma. The range is 0 to 4094.
•
(Optional) For diameter net-diameter, specify the
maximum number of switches between any two end
stations. The range is 2 to 7. This keyword is available
only for MST instance 0.
•
(Optional) For hello-time seconds, specify the interval in
seconds between the generation of configuration messages
by the root switch. The range is 1 to 10 seconds; the
default is 2 seconds.
Step 3
end
Return to privileged EXEC mode.
Step 4
show spanning-tree mst instance-id
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To return the switch to its default setting, use the no spanning-tree mst instance-id root global
configuration command.
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Configuring a Secondary Root Switch
When you configure a switch with the extended system ID support as the secondary root, the switch
priority is modified from the default value (32768) to 28672. The switch is then likely to become the root
switch for the specified instance if the primary root switch fails. This is assuming that the other network
switches use the default switch priority of 32768 and therefore are unlikely to become the root switch.
You can execute this command on more than one switch to configure multiple backup root switches. Use
the same network diameter and hello-time values that you used when you configured the primary root
switch with the spanning-tree mst instance-id root primary global configuration command.
Beginning in privileged EXEC mode, follow these steps to configure a switch as the secondary root
switch. This procedure is optional.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
spanning-tree mst instance-id root
secondary [diameter net-diameter
[hello-time seconds]]
Configure a switch as the secondary root switch.
•
For instance-id, you can specify a single instance, a range of
instances separated by a hyphen, or a series of instances
separated by a comma. The range is 0 to 4094.
•
(Optional) For diameter net-diameter, specify the maximum
number of switches between any two end stations. The range is 2
to 7. This keyword is available only for MST instance 0.
•
(Optional) For hello-time seconds, specify the interval in
seconds between the generation of configuration messages by
the root switch. The range is 1 to 10 seconds; the default
is 2 seconds.
Use the same network diameter and hello-time values that you used
when configuring the primary root switch. See the “Configuring the
Root Switch” section on page 18-17.
Step 3
end
Return to privileged EXEC mode.
Step 4
show spanning-tree mst instance-id
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save your entries