null  null
Cisco Security Appliance Command Line
Configuration Guide
For the Cisco ASA 5500 Series and Cisco PIX 500 Series
Software Version 7.2
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Text Part Number: OL-10088-02
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Cisco Security Appliance Command Line Configuration Guide
Copyright © 2008 Cisco Systems, Inc. All rights reserved.
C O N T E N T S
About This Guide
xxxv
Document Objectives
Audience
xxxv
xxxv
Related Documentation
xxxvi
Document Organization
xxxvi
Document Conventions
xxxix
Obtaining Documentation and Submitting a Service Request
PART
Getting Started and General Information
1
CHAPTER
xxxix
1
Introduction to the Security Appliance
1-1
Firewall Functional Overview 1-1
Security Policy Overview 1-2
Permitting or Denying Traffic with Access Lists 1-2
Applying NAT 1-2
Using AAA for Through Traffic 1-2
Applying HTTP, HTTPS, or FTP Filtering 1-3
Applying Application Inspection 1-3
Sending Traffic to the Advanced Inspection and Prevention Security Services Module
Sending Traffic to the Content Security and Control Security Services Module 1-3
Applying QoS Policies 1-3
Applying Connection Limits and TCP Normalization 1-3
Firewall Mode Overview 1-3
Stateful Inspection Overview 1-4
VPN Functional Overview
1-5
Intrusion Prevention Services Functional Overview
Security Context Overview
CHAPTER
2
Getting Started
1-3
1-5
1-6
2-1
Getting Started with Your Platform Model
2-1
Factory Default Configurations 2-1
Restoring the Factory Default Configuration
ASA 5505 Default Configuration 2-2
2-2
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ASA 5510 and Higher Default Configuration
PIX 515/515E Default Configuration 2-4
Accessing the Command-Line Interface
2-3
2-4
Setting Transparent or Routed Firewall Mode
2-5
Working with the Configuration 2-6
Saving Configuration Changes 2-6
Saving Configuration Changes in Single Context Mode 2-7
Saving Configuration Changes in Multiple Context Mode 2-7
Copying the Startup Configuration to the Running Configuration 2-8
Viewing the Configuration 2-8
Clearing and Removing Configuration Settings 2-9
Creating Text Configuration Files Offline 2-9
CHAPTER
3
Enabling Multiple Context Mode
3-1
Security Context Overview 3-1
Common Uses for Security Contexts 3-1
Unsupported Features 3-2
Context Configuration Files 3-2
Context Configurations 3-2
System Configuration 3-2
Admin Context Configuration 3-2
How the Security Appliance Classifies Packets 3-3
Valid Classifier Criteria 3-3
Invalid Classifier Criteria 3-4
Classification Examples 3-5
Cascading Security Contexts 3-8
Management Access to Security Contexts 3-9
System Administrator Access 3-9
Context Administrator Access 3-10
Enabling or Disabling Multiple Context Mode 3-10
Backing Up the Single Mode Configuration 3-10
Enabling Multiple Context Mode 3-10
Restoring Single Context Mode 3-11
CHAPTER
4
Configuring Switch Ports and VLAN Interfaces for the Cisco ASA 5505 Adaptive Security
Appliance 4-1
Interface Overview 4-1
Understanding ASA 5505 Ports and Interfaces 4-2
Maximum Active VLAN Interfaces for Your License 4-2
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Default Interface Configuration
VLAN MAC Addresses 4-4
Power Over Ethernet 4-4
Monitoring Traffic Using SPAN
Security Level Overview 4-5
Configuring VLAN Interfaces
4-4
4-4
4-5
Configuring Switch Ports as Access Ports
4-9
Configuring a Switch Port as a Trunk Port
4-11
Allowing Communication Between VLAN Interfaces on the Same Security Level
CHAPTER
5
Configuring Ethernet Settings and Subinterfaces
Configuring and Enabling RJ-45 Interfaces
Configuring and Enabling Fiber Interfaces
5-1
5-1
5-2
Configuring and Enabling VLAN Subinterfaces and 802.1Q Trunking
CHAPTER
6
Adding and Managing Security Contexts
Configuring Resource Management 6-1
Classes and Class Members Overview
Resource Limits 6-2
Default Class 6-3
Class Members 6-4
Configuring a Class 6-4
Configuring a Security Context
4-13
5-3
6-1
6-1
6-7
Automatically Assigning MAC Addresses to Context Interfaces
Changing Between Contexts and the System Execution Space
Managing Security Contexts 6-12
Removing a Security Context 6-12
Changing the Admin Context 6-13
Changing the Security Context URL 6-13
Reloading a Security Context 6-14
Reloading by Clearing the Configuration 6-14
Reloading by Removing and Re-adding the Context
Monitoring Security Contexts 6-15
Viewing Context Information 6-15
Viewing Resource Allocation 6-16
Viewing Resource Usage 6-19
Monitoring SYN Attacks in Contexts 6-20
6-11
6-11
6-15
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CHAPTER
7
Configuring Interface Parameters
Security Level Overview
7-1
7-1
Configuring the Interface
7-2
Allowing Communication Between Interfaces on the Same Security Level
CHAPTER
8
Configuring Basic Settings
8-1
Changing the Login Password
Changing the Enable Password
Setting the Hostname
8-1
8-1
8-2
Setting the Domain Name
8-2
Setting the Date and Time 8-2
Setting the Time Zone and Daylight Saving Time Date Range
Setting the Date and Time Using an NTP Server 8-4
Setting the Date and Time Manually 8-4
Setting the Management IP Address for a Transparent Firewall
CHAPTER
9
Configuring IP Routing
7-6
8-3
8-5
9-1
How Routing Behaves Within the ASA Security Appliance
Egress Interface Selection Process 9-1
Next Hop Selection Process 9-2
9-1
Configuring Static and Default Routes 9-2
Configuring a Static Route 9-3
Configuring a Default Route 9-4
Configuring Static Route Tracking 9-5
Defining Route Maps
9-7
Configuring OSPF 9-8
OSPF Overview 9-9
Enabling OSPF 9-9
Redistributing Routes Into OSPF 9-10
Configuring OSPF Interface Parameters 9-11
Configuring OSPF Area Parameters 9-13
Configuring OSPF NSSA 9-14
Configuring Route Summarization Between OSPF Areas 9-15
Configuring Route Summarization When Redistributing Routes into OSPF
Defining Static OSPF Neighbors 9-16
Generating a Default Route 9-17
Configuring Route Calculation Timers 9-17
Logging Neighbors Going Up or Down 9-18
9-16
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Displaying OSPF Update Packet Pacing
Monitoring OSPF 9-19
Restarting the OSPF Process 9-20
9-18
Configuring RIP 9-20
Enabling and Configuring RIP 9-20
Redistributing Routes into the RIP Routing Process 9-21
Configuring RIP Send/Receive Version on an Interface 9-22
Enabling RIP Authentication 9-23
Monitoring RIP 9-23
The Routing Table 9-23
Displaying the Routing Table 9-24
How the Routing Table is Populated 9-24
Backup Routes 9-25
How Forwarding Decisions are Made 9-26
Dynamic Routing and Failover
CHAPTER
10
9-26
Configuring DHCP, DDNS, and WCCP Services
10-1
Configuring a DHCP Server 10-1
Enabling the DHCP Server 10-2
Configuring DHCP Options 10-3
Using Cisco IP Phones with a DHCP Server
10-4
Configuring DHCP Relay Services
10-5
Configuring Dynamic DNS 10-6
Example 1: Client Updates Both A and PTR RRs for Static IP Addresses 10-7
Example 2: Client Updates Both A and PTR RRs; DHCP Server Honors Client Update Request; FQDN
Provided Through Configuration 10-7
Example 3: Client Includes FQDN Option Instructing Server Not to Update Either RR; Server Overrides
Client and Updates Both RRs. 10-8
Example 4: Client Asks Server To Perform Both Updates; Server Configured to Update PTR RR Only;
Honors Client Request and Updates Both A and PTR RR 10-8
Example 5: Client Updates A RR; Server Updates PTR RR 10-9
Configuring Web Cache Services Using WCCP 10-9
WCCP Feature Support 10-9
WCCP Interaction With Other Features 10-10
Enabling WCCP Redirection 10-10
CHAPTER
11
Configuring Multicast Routing
Multicast Routing Overview
Enabling Multicast Routing
11-13
11-13
11-14
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Configuring IGMP Features 11-14
Disabling IGMP on an Interface 11-15
Configuring Group Membership 11-15
Configuring a Statically Joined Group 11-15
Controlling Access to Multicast Groups 11-15
Limiting the Number of IGMP States on an Interface 11-16
Modifying the Query Interval and Query Timeout 11-16
Changing the Query Response Time 11-17
Changing the IGMP Version 11-17
Configuring Stub Multicast Routing
Configuring a Static Multicast Route
11-17
11-17
Configuring PIM Features 11-18
Disabling PIM on an Interface 11-18
Configuring a Static Rendezvous Point Address 11-19
Configuring the Designated Router Priority 11-19
Filtering PIM Register Messages 11-19
Configuring PIM Message Intervals 11-20
Configuring a Multicast Boundary 11-20
Filtering PIM Neighbors 11-20
Supporting Mixed Bidirectional/Sparse-Mode PIM Networks
For More Information about Multicast Routing
CHAPTER
12
Configuring IPv6
11-21
11-22
12-1
IPv6-enabled Commands
12-1
Configuring IPv6 12-2
Configuring IPv6 on an Interface 12-3
Configuring a Dual IP Stack on an Interface 12-4
Enforcing the Use of Modified EUI-64 Interface IDs in IPv6 Addresses
Configuring IPv6 Duplicate Address Detection 12-4
Configuring IPv6 Default and Static Routes 12-5
Configuring IPv6 Access Lists 12-6
Configuring IPv6 Neighbor Discovery 12-7
Configuring Neighbor Solicitation Messages 12-7
Configuring Router Advertisement Messages 12-9
Multicast Listener Discovery Support 12-11
Configuring a Static IPv6 Neighbor 12-11
12-4
Verifying the IPv6 Configuration 12-11
The show ipv6 interface Command 12-12
The show ipv6 route Command 12-12
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The show ipv6 mld traffic Command
CHAPTER
13
12-13
Configuring AAA Servers and the Local Database
13-1
AAA Overview 13-1
About Authentication 13-1
About Authorization 13-2
About Accounting 13-2
AAA Server and Local Database Support 13-2
Summary of Support 13-3
RADIUS Server Support 13-3
Authentication Methods 13-4
Attribute Support 13-4
RADIUS Authorization Functions 13-4
TACACS+ Server Support 13-4
SDI Server Support 13-4
SDI Version Support 13-5
Two-step Authentication Process 13-5
SDI Primary and Replica Servers 13-5
NT Server Support 13-5
Kerberos Server Support 13-5
LDAP Server Support 13-6
Authentication with LDAP 13-6
Authorization with LDAP for VPN 13-7
LDAP Attribute Mapping 13-8
SSO Support for WebVPN with HTTP Forms 13-9
Local Database Support 13-9
User Profiles 13-10
Fallback Support 13-10
Configuring the Local Database
13-10
Identifying AAA Server Groups and Servers
Using Certificates and User Login Credentials
Using User Login Credentials 13-15
Using certificates 13-16
13-12
13-15
Supporting a Zone Labs Integrity Server 13-16
Overview of Integrity Server and Security Appliance Interaction
Configuring Integrity Server Support 13-17
CHAPTER
14
Configuring Failover
13-17
14-1
Understanding Failover
14-1
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Failover System Requirements 14-2
Hardware Requirements 14-2
Software Requirements 14-2
License Requirements 14-2
The Failover and Stateful Failover Links 14-3
Failover Link 14-3
Stateful Failover Link 14-5
Active/Active and Active/Standby Failover 14-6
Active/Standby Failover 14-6
Active/Active Failover 14-9
Determining Which Type of Failover to Use 14-14
Regular and Stateful Failover 14-15
Regular Failover 14-15
Stateful Failover 14-15
Failover Health Monitoring 14-16
Unit Health Monitoring 14-16
Interface Monitoring 14-17
Failover Feature/Platform Matrix 14-17
Failover Times by Platform 14-18
Configuring Failover 14-18
Failover Configuration Limitations 14-19
Configuring Active/Standby Failover 14-19
Prerequisites 14-19
Configuring Cable-Based Active/Standby Failover (PIX Security Appliance Only)
Configuring LAN-Based Active/Standby Failover 14-21
Configuring Optional Active/Standby Failover Settings 14-24
Configuring Active/Active Failover 14-26
Prerequisites 14-27
Configuring Cable-Based Active/Active Failover (PIX security appliance) 14-27
Configuring LAN-Based Active/Active Failover 14-29
Configuring Optional Active/Active Failover Settings 14-32
Configuring Unit Health Monitoring 14-38
Configuring Failover Communication Authentication/Encryption 14-39
Verifying the Failover Configuration 14-39
Using the show failover Command 14-40
Viewing Monitored Interfaces 14-48
Displaying the Failover Commands in the Running Configuration 14-48
Testing the Failover Functionality 14-48
Controlling and Monitoring Failover
Forcing Failover 14-49
14-19
14-49
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Disabling Failover 14-49
Restoring a Failed Unit or Failover Group
Monitoring Failover 14-50
Failover System Messages 14-50
Debug Messages 14-50
SNMP 14-51
PART
Configuring the Firewall
2
CHAPTER
14-50
15
Firewall Mode Overview
15-1
Routed Mode Overview 15-1
IP Routing Support 15-1
Network Address Translation 15-2
How Data Moves Through the Security Appliance in Routed Firewall Mode
An Inside User Visits a Web Server 15-3
An Outside User Visits a Web Server on the DMZ 15-4
An Inside User Visits a Web Server on the DMZ 15-6
An Outside User Attempts to Access an Inside Host 15-7
A DMZ User Attempts to Access an Inside Host 15-8
Transparent Mode Overview 15-8
Transparent Firewall Network 15-9
Allowing Layer 3 Traffic 15-9
Allowed MAC Addresses 15-9
Passing Traffic Not Allowed in Routed Mode 15-9
MAC Address Lookups 15-10
Using the Transparent Firewall in Your Network 15-10
Transparent Firewall Guidelines 15-10
Unsupported Features in Transparent Mode 15-11
How Data Moves Through the Transparent Firewall 15-13
An Inside User Visits a Web Server 15-14
An Outside User Visits a Web Server on the Inside Network
An Outside User Attempts to Access an Inside Host 15-16
CHAPTER
16
Identifying Traffic with Access Lists
15-3
15-15
16-1
Access List Overview 16-1
Access List Types 16-2
Access Control Entry Order 16-2
Access Control Implicit Deny 16-3
IP Addresses Used for Access Lists When You Use NAT
16-3
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Adding an Extended Access List 16-5
Extended Access List Overview 16-5
Allowing Broadcast and Multicast Traffic through the Transparent Firewall
Adding an Extended ACE 16-6
Adding an EtherType Access List 16-8
EtherType Access List Overview 16-8
Supported EtherTypes 16-8
Implicit Permit of IP and ARPs Only 16-9
Implicit and Explicit Deny ACE at the End of an Access List 16-9
IPv6 Unsupported 16-9
Using Extended and EtherType Access Lists on the Same Interface
Allowing MPLS 16-9
Adding an EtherType ACE 16-10
Adding a Standard Access List
16-10
Adding a Webtype Access List
16-11
16-6
16-9
Simplifying Access Lists with Object Grouping 16-11
How Object Grouping Works 16-11
Adding Object Groups 16-12
Adding a Protocol Object Group 16-12
Adding a Network Object Group 16-13
Adding a Service Object Group 16-13
Adding an ICMP Type Object Group 16-14
Nesting Object Groups 16-15
Using Object Groups with an Access List 16-16
Displaying Object Groups 16-17
Removing Object Groups 16-17
Adding Remarks to Access Lists
16-17
Scheduling Extended Access List Activation 16-18
Adding a Time Range 16-18
Applying the Time Range to an ACE 16-19
Logging Access List Activity 16-19
Access List Logging Overview 16-19
Configuring Logging for an Access Control Entry
Managing Deny Flows 16-21
CHAPTER
17
Applying NAT
16-20
17-1
NAT Overview 17-1
Introduction to NAT
NAT Control 17-3
17-2
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NAT Types 17-5
Dynamic NAT 17-5
PAT 17-7
Static NAT 17-7
Static PAT 17-8
Bypassing NAT When NAT Control is Enabled 17-9
Policy NAT 17-9
NAT and Same Security Level Interfaces 17-12
Order of NAT Commands Used to Match Real Addresses 17-13
Mapped Address Guidelines 17-13
DNS and NAT 17-14
Configuring NAT Control
17-15
Using Dynamic NAT and PAT 17-16
Dynamic NAT and PAT Implementation 17-16
Configuring Dynamic NAT or PAT 17-22
Using Static NAT
17-25
Using Static PAT
17-26
Bypassing NAT 17-28
Configuring Identity NAT 17-29
Configuring Static Identity NAT 17-29
Configuring NAT Exemption 17-31
NAT Examples 17-32
Overlapping Networks 17-33
Redirecting Ports 17-34
CHAPTER
18
Permitting or Denying Network Access
18-1
Inbound and Outbound Access List Overview
Applying an Access List to an Interface
CHAPTER
19
Applying AAA for Network Access
AAA Performance
18-1
18-2
19-1
19-1
Configuring Authentication for Network Access 19-1
Authentication Overview 19-2
One-Time Authentication 19-2
Applications Required to Receive an Authentication Challenge
Security Appliance Authentication Prompts 19-2
Static PAT and HTTP 19-3
Enabling Network Access Authentication 19-3
19-2
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Enabling Secure Authentication of Web Clients 19-5
Authenticating Directly with the Security Appliance 19-6
Enabling Direct Authentication Using HTTP and HTTPS
Enabling Direct Authentication Using Telnet 19-6
19-6
Configuring Authorization for Network Access 19-6
Configuring TACACS+ Authorization 19-7
Configuring RADIUS Authorization 19-8
Configuring a RADIUS Server to Send Downloadable Access Control Lists 19-9
Configuring a RADIUS Server to Download Per-User Access Control List Names 19-12
Configuring Accounting for Network Access
19-13
Using MAC Addresses to Exempt Traffic from Authentication and Authorization
CHAPTER
20
Applying Filtering Services
Filtering Overview
19-14
20-1
20-1
Filtering ActiveX Objects 20-2
ActiveX Filtering Overview 20-2
Enabling ActiveX Filtering 20-2
Filtering Java Applets
20-3
Filtering URLs and FTP Requests with an External Server
URL Filtering Overview 20-4
Identifying the Filtering Server 20-4
Buffering the Content Server Response 20-6
Caching Server Addresses 20-6
Filtering HTTP URLs 20-7
Configuring HTTP Filtering 20-7
Enabling Filtering of Long HTTP URLs 20-7
Truncating Long HTTP URLs 20-7
Exempting Traffic from Filtering 20-8
Filtering HTTPS URLs 20-8
Filtering FTP Requests 20-9
20-4
Viewing Filtering Statistics and Configuration 20-9
Viewing Filtering Server Statistics 20-10
Viewing Buffer Configuration and Statistics 20-11
Viewing Caching Statistics 20-11
Viewing Filtering Performance Statistics 20-11
Viewing Filtering Configuration 20-12
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CHAPTER
21
Using Modular Policy Framework
21-1
Modular Policy Framework Overview 21-1
Modular Policy Framework Features 21-1
Modular Policy Framework Configuration Overview
Default Global Policy 21-3
21-2
Identifying Traffic (Layer 3/4 Class Map) 21-4
Default Class Maps 21-4
Creating a Layer 3/4 Class Map for Through Traffic 21-5
Creating a Layer 3/4 Class Map for Management Traffic 21-7
Configuring Special Actions for Application Inspections (Inspection Policy Map)
Inspection Policy Map Overview 21-8
Defining Actions in an Inspection Policy Map 21-8
Identifying Traffic in an Inspection Class Map 21-11
Creating a Regular Expression 21-12
Creating a Regular Expression Class Map 21-14
21-7
Defining Actions (Layer 3/4 Policy Map) 21-15
Layer 3/4 Policy Map Overview 21-15
Policy Map Guidelines 21-16
Supported Feature Types 21-16
Hierarchical Policy Maps 21-16
Feature Directionality 21-17
Feature Matching Guidelines within a Policy Map 21-17
Feature Matching Guidelines for multiple Policy Maps 21-18
Order in Which Multiple Feature Actions are Applied 21-18
Default Layer 3/4 Policy Map 21-18
Adding a Layer 3/4 Policy Map 21-19
Applying Actions to an Interface (Service Policy)
21-21
Modular Policy Framework Examples 21-21
Applying Inspection and QoS Policing to HTTP Traffic 21-22
Applying Inspection to HTTP Traffic Globally 21-22
Applying Inspection and Connection Limits to HTTP Traffic to Specific Servers
Applying Inspection to HTTP Traffic with NAT 21-24
CHAPTER
22
Managing AIP SSM and CSC SSM
21-23
22-1
Managing the AIP SSM 22-1
About the AIP SSM 22-1
Getting Started with the AIP SSM 22-2
Diverting Traffic to the AIP SSM 22-2
Sessioning to the AIP SSM and Running Setup
22-4
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Managing the CSC SSM 22-5
About the CSC SSM 22-5
Getting Started with the CSC SSM 22-7
Determining What Traffic to Scan 22-9
Limiting Connections Through the CSC SSM
Diverting Traffic to the CSC SSM 22-11
Checking SSM Status
22-13
Transferring an Image onto an SSM
CHAPTER
23
22-11
Preventing Network Attacks
22-14
23-1
Configuring TCP Normalization 23-1
TCP Normalization Overview 23-1
Enabling the TCP Normalizer 23-2
Configuring Connection Limits and Timeouts 23-6
Connection Limit Overview 23-7
TCP Intercept Overview 23-7
Disabling TCP Intercept for Management Packets for Clientless SSL Compatibility
Dead Connection Detection (DCD) Overview 23-7
TCP Sequence Randomization Overview 23-8
Enabling Connection Limits and Timeouts 23-8
Preventing IP Spoofing
23-10
Configuring the Fragment Size
Blocking Unwanted Connections
23-11
23-11
Configuring IP Audit for Basic IPS Support
CHAPTER
24
Configuring QoS
23-7
23-12
24-1
QoS Overview 24-1
Supported QoS Features 24-2
What is a Token Bucket? 24-2
Policing Overview 24-3
Priority Queueing Overview 24-3
Traffic Shaping Overview 24-4
How QoS Features Interact 24-4
DSCP and DiffServ Preservation 24-5
Creating the Standard Priority Queue for an Interface
Identifying Traffic for QoS Using Class Maps
Creating a QoS Class Map 24-6
QoS Class Map Examples 24-7
24-5
24-6
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Creating a Policy for Standard Priority Queueing and/or Policing
24-8
Creating a Policy for Traffic Shaping and Hierarchical Priority Queueing
24-10
Viewing QoS Statistics 24-12
Viewing QoS Police Statistics 24-12
Viewing QoS Standard Priority Statistics 24-12
Viewing QoS Shaping Statistics 24-13
Viewing QoS Standard Priority Queue Statistics 24-14
CHAPTER
25
Configuring Application Layer Protocol Inspection
Inspection Engine Overview 25-2
When to Use Application Protocol Inspection
Inspection Limitations 25-2
Default Inspection Policy 25-3
Configuring Application Inspection
25-1
25-2
25-5
CTIQBE Inspection 25-9
CTIQBE Inspection Overview 25-9
Limitations and Restrictions 25-10
Verifying and Monitoring CTIQBE Inspection
25-10
DCERPC Inspection 25-11
DCERPC Overview 25-11
Configuring a DCERPC Inspection Policy Map for Additional Inspection Control
DNS Inspection 25-13
How DNS Application Inspection Works 25-13
How DNS Rewrite Works 25-14
Configuring DNS Rewrite 25-15
Using the Static Command for DNS Rewrite 25-15
Using the Alias Command for DNS Rewrite 25-16
Configuring DNS Rewrite with Two NAT Zones 25-16
DNS Rewrite with Three NAT Zones 25-17
Configuring DNS Rewrite with Three NAT Zones 25-19
Verifying and Monitoring DNS Inspection 25-20
Configuring a DNS Inspection Policy Map for Additional Inspection Control
25-20
ESMTP Inspection 25-23
Configuring an ESMTP Inspection Policy Map for Additional Inspection Control
FTP Inspection 25-26
FTP Inspection Overview 25-27
Using the strict Option 25-27
Configuring an FTP Inspection Policy Map for Additional Inspection Control
Verifying and Monitoring FTP Inspection 25-31
25-12
25-24
25-28
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GTP Inspection 25-32
GTP Inspection Overview 25-32
Configuring a GTP Inspection Policy Map for Additional Inspection Control
Verifying and Monitoring GTP Inspection 25-37
25-33
H.323 Inspection 25-38
H.323 Inspection Overview 25-38
How H.323 Works 25-38
Limitations and Restrictions 25-39
Configuring an H.323 Inspection Policy Map for Additional Inspection Control
Configuring H.323 and H.225 Timeout Values 25-42
Verifying and Monitoring H.323 Inspection 25-43
Monitoring H.225 Sessions 25-43
Monitoring H.245 Sessions 25-43
Monitoring H.323 RAS Sessions 25-44
HTTP Inspection 25-44
HTTP Inspection Overview 25-44
Configuring an HTTP Inspection Policy Map for Additional Inspection Control
25-40
25-45
Instant Messaging Inspection 25-49
IM Inspection Overview 25-49
Configuring an Instant Messaging Inspection Policy Map for Additional Inspection Control
ICMP Inspection
25-52
ICMP Error Inspection
ILS Inspection
25-52
25-53
IPSec Pass Through Inspection 25-54
IPSec Pass Through Inspection Overview 25-54
Configuring an IPSec Pass Through Inspection Policy Map for Additional Inspection Control
MGCP Inspection 25-56
MGCP Inspection Overview 25-56
Configuring an MGCP Inspection Policy Map for Additional Inspection Control
Configuring MGCP Timeout Values 25-59
Verifying and Monitoring MGCP Inspection 25-59
NetBIOS Inspection 25-60
Configuring a NetBIOS Inspection Policy Map for Additional Inspection Control
PPTP Inspection
RTSP Inspection
25-54
25-58
25-60
25-62
RADIUS Accounting Inspection 25-62
Configuring a RADIUS Inspection Policy Map for Additional Inspection Control
RSH Inspection
25-49
25-63
25-63
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RTSP Inspection Overview 25-63
Using RealPlayer 25-64
Restrictions and Limitations 25-64
SIP Inspection 25-65
SIP Inspection Overview 25-65
SIP Instant Messaging 25-65
Configuring a SIP Inspection Policy Map for Additional Inspection Control
Configuring SIP Timeout Values 25-70
Verifying and Monitoring SIP Inspection 25-70
25-66
Skinny (SCCP) Inspection 25-71
SCCP Inspection Overview 25-71
Supporting Cisco IP Phones 25-71
Restrictions and Limitations 25-72
Verifying and Monitoring SCCP Inspection 25-72
Configuring a Skinny (SCCP) Inspection Policy Map for Additional Inspection Control
SMTP and Extended SMTP Inspection
SNMP Inspection
25-74
25-76
SQL*Net Inspection
25-76
Sun RPC Inspection 25-77
Sun RPC Inspection Overview 25-77
Managing Sun RPC Services 25-77
Verifying and Monitoring Sun RPC Inspection
TFTP Inspection
XDMCP Inspection
CHAPTER
26
25-73
25-78
25-79
25-80
Configuring ARP Inspection and Bridging Parameters
26-1
Configuring ARP Inspection 26-1
ARP Inspection Overview 26-1
Adding a Static ARP Entry 26-2
Enabling ARP Inspection 26-2
Customizing the MAC Address Table 26-3
MAC Address Table Overview 26-3
Adding a Static MAC Address 26-3
Setting the MAC Address Timeout 26-4
Disabling MAC Address Learning 26-4
Viewing the MAC Address Table 26-4
PART
3
Configuring VPN
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CHAPTER
27
Configuring IPSec and ISAKMP
Tunneling Overview
IPSec Overview
27-1
27-1
27-2
Configuring ISAKMP 27-2
ISAKMP Overview 27-2
Configuring ISAKMP Policies 27-5
Enabling ISAKMP on the Outside Interface 27-6
Disabling ISAKMP in Aggressive Mode 27-6
Determining an ID Method for ISAKMP Peers 27-6
Enabling IPSec over NAT-T 27-7
Using NAT-T 27-7
Enabling IPSec over TCP 27-8
Waiting for Active Sessions to Terminate Before Rebooting
Alerting Peers Before Disconnecting 27-9
27-9
Configuring Certificate Group Matching 27-9
Creating a Certificate Group Matching Rule and Policy 27-10
Using the Tunnel-group-map default-group Command 27-11
Configuring IPSec 27-11
Understanding IPSec Tunnels 27-11
Understanding Transform Sets 27-12
Defining Crypto Maps 27-12
Applying Crypto Maps to Interfaces 27-20
Using Interface Access Lists 27-20
Changing IPSec SA Lifetimes 27-22
Creating a Basic IPSec Configuration 27-22
Using Dynamic Crypto Maps 27-24
Providing Site-to-Site Redundancy 27-26
Viewing an IPSec Configuration 27-26
Clearing Security Associations
27-27
Clearing Crypto Map Configurations
Supporting the Nokia VPN Client
CHAPTER
28
Configuring L2TP over IPSec
27-27
27-28
28-1
L2TP Overview 28-1
IPSec Transport and Tunnel Modes
Configuring L2TP over IPSec Connections
Tunnel Group Switching 28-5
28-2
28-2
Viewing L2TP over IPSec Connection Information
28-5
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Using L2TP Debug Commands 28-7
Enabling IPSec Debug 28-7
Getting Additional Information 28-8
CHAPTER
29
Setting General IPSec VPN Parameters
29-1
Configuring VPNs in Single, Routed Mode
Configuring IPSec to Bypass ACLs
29-1
29-1
Permitting Intra-Interface Traffic 29-2
NAT Considerations for Intra-Interface Traffic
Setting Maximum Active IPSec VPN Sessions
29-3
29-3
Using Client Update to Ensure Acceptable Client Revision Levels
29-3
Understanding Load Balancing 29-5
Implementing Load Balancing 29-6
Prerequisites 29-6
Eligible Platforms 29-7
Eligible Clients 29-7
VPN Load-Balancing Cluster Configurations 29-7
Some Typical Mixed Cluster Scenarios 29-8
Scenario 1: Mixed Cluster with No WebVPN Connections 29-8
Scenario 2: Mixed Cluster Handling WebVPN Connections 29-8
Configuring Load Balancing 29-9
Configuring the Public and Private Interfaces for Load Balancing
Configuring the Load Balancing Cluster Attributes 29-10
Configuring VPN Session Limits
CHAPTER
30
29-9
29-11
Configuring Tunnel Groups, Group Policies, and Users
Overview of Tunnel Groups, Group Policies, and Users
30-1
30-1
Tunnel Groups 30-2
General Tunnel-Group Connection Parameters 30-2
IPSec Tunnel-Group Connection Parameters 30-3
WebVPN Tunnel-Group Connection Parameters 30-4
Configuring Tunnel Groups 30-5
Default IPSec Remote Access Tunnel Group Configuration 30-5
Configuring IPSec Tunnel-Group General Attributes 30-6
Configuring IPSec Remote-Access Tunnel Groups 30-6
Specifying a Name and Type for the IPSec Remote Access Tunnel Group 30-6
Configuring IPSec Remote-Access Tunnel Group General Attributes 30-6
Configuring IPSec Remote-Access Tunnel Group IPSec Attributes 30-10
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Configuring IPSec Remote-Access Tunnel Group PPP Attributes 30-12
Configuring LAN-to-LAN Tunnel Groups 30-13
Default LAN-to-LAN Tunnel Group Configuration 30-13
Specifying a Name and Type for a LAN-to-LAN Tunnel Group 30-13
Configuring LAN-to-LAN Tunnel Group General Attributes 30-14
Configuring LAN-to-LAN IPSec Attributes 30-14
Configuring WebVPN Tunnel Groups 30-16
Specifying a Name and Type for a WebVPN Tunnel Group 30-16
Configuring WebVPN Tunnel-Group General Attributes 30-17
Configuring WebVPN Tunnel-Group WebVPN Attributes 30-20
Customizing Login Windows for WebVPN Users 30-23
Configuring Microsoft Active Directory Settings for Password Management 30-24
Using Active Directory to Force the User to Change Password at Next Logon 30-24
Using Active Directory to Specify Maximum Password Age 30-26
Using Active Directory to Override an Account Disabled AAA Indicator 30-27
Using Active Directory to Enforce Minimum Password Length 30-28
Using Active Directory to Enforce Password Complexity 30-29
Group Policies 30-30
Default Group Policy 30-31
Configuring Group Policies 30-33
Configuring an External Group Policy 30-33
Configuring an Internal Group Policy 30-34
Configuring Group Policy Attributes 30-34
Configuring WINS and DNS Servers 30-34
Configuring VPN-Specific Attributes 30-35
Configuring Security Attributes 30-38
Configuring the Banner Message 30-40
Configuring IPSec-UDP Attributes 30-40
Configuring Split-Tunneling Attributes 30-41
Configuring Domain Attributes for Tunneling 30-42
Configuring Attributes for VPN Hardware Clients 30-44
Configuring Backup Server Attributes 30-47
Configuring Microsoft Internet Explorer Client Parameters 30-48
Configuring Network Admission Control Parameters 30-50
Configuring Address Pools 30-53
Configuring Firewall Policies 30-54
Configuring Client Access Rules 30-57
Configuring Group-Policy WebVPN Attributes 30-58
Configuring User Attributes 30-69
Viewing the Username Configuration
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Configuring Attributes for Specific Users 30-70
Setting a User Password and Privilege Level 30-70
Configuring User Attributes 30-71
Configuring VPN User Attributes 30-71
Configuring WebVPN for Specific Users 30-75
CHAPTER
31
Configuring IP Addresses for VPNs
31-1
Configuring an IP Address Assignment Method
Configuring Local IP Address Pools 31-2
Configuring AAA Addressing 31-2
Configuring DHCP Addressing 31-3
CHAPTER
32
Configuring Remote Access IPSec VPNs
Summary of the Configuration
Configuring Interfaces
31-1
32-1
32-1
32-2
Configuring ISAKMP Policy and Enabling ISAKMP on the Outside Interface
Configuring an Address Pool
Adding a User
32-4
32-4
Creating a Transform Set
Defining a Tunnel Group
32-4
32-5
Creating a Dynamic Crypto Map
32-6
Creating a Crypto Map Entry to Use the Dynamic Crypto Map
CHAPTER
33
32-3
Configuring Network Admission Control
Uses, Requirements, and Limitations
32-7
33-1
33-1
Configuring Basic Settings 33-1
Specifying the Access Control Server Group
Enabling NAC 33-2
Configuring the Default ACL for NAC 33-3
Configuring Exemptions from NAC 33-4
33-2
Changing Advanced Settings 33-5
Changing Clientless Authentication Settings 33-5
Enabling and Disabling Clientless Authentication 33-5
Changing the Login Credentials Used for Clientless Authentication
Configuring NAC Session Attributes 33-7
Setting the Query-for-Posture-Changes Timer 33-8
Setting the Revalidation Timer 33-9
33-6
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CHAPTER
34
Configuring Easy VPN Services on the ASA 5505
34-1
Specifying the Client/Server Role of the Cisco ASA 5505
Specifying the Primary and Secondary Servers
Specifying the Mode 34-3
NEM with Multiple Interfaces
34-2
34-3
Configuring Automatic Xauth Authentication
Configuring IPSec Over TCP
34-1
34-4
34-4
Comparing Tunneling Options
34-5
Specifying the Tunnel Group or Trustpoint
Specifying the Tunnel Group 34-6
Specifying the Trustpoint 34-7
Configuring Split Tunneling
34-6
34-7
Configuring Device Pass-Through
34-8
Configuring Remote Management
34-8
Guidelines for Configuring the Easy VPN Server 34-9
Group Policy and User Attributes Pushed to the Client
Authentication Options 34-11
CHAPTER
35
Configuring the PPPoE Client
PPPoE Client Overview
35-1
35-1
Configuring the PPPoE Client Username and Password
Enabling PPPoE
35-3
Monitoring and Debugging the PPPoE Client
36
35-2
35-3
Using PPPoE with a Fixed IP Address
CHAPTER
34-9
Clearing the Configuration
35-5
Using Related Commands
35-5
Configuring LAN-to-LAN IPSec VPNs
Summary of the Configuration
Configuring Interfaces
35-4
36-1
36-1
36-2
Configuring ISAKMP Policy and Enabling ISAKMP on the Outside Interface
Creating a Transform Set
Configuring an ACL
36-2
36-4
36-4
Defining a Tunnel Group
36-5
Creating a Crypto Map and Applying It To an Interface
Applying Crypto Maps to Interfaces 36-7
36-6
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CHAPTER
37
Configuring WebVPN
37-1
Getting Started with WebVPN 37-1
Observing WebVPN Security Precautions 37-2
Understanding Features Not Supported for WebVPN 37-2
Using SSL to Access the Central Site 37-3
Using HT4TPS for WebVPN Sessions 37-3
Configuring WebVPN and ASDM on the Same Interface 37-3
Setting WebVPN HTTP/HTTPS Proxy 37-4
Configuring SSL/TLS Encryption Protocols 37-4
Authenticating with Digital Certificates 37-5
Enabling Cookies on Browsers for WebVPN 37-5
Managing Passwords 37-5
Using Single Sign-on with WebVPN 37-6
Configuring SSO with HTTP Basic or NTLM Authentication 37-6
Configuring SSO Authentication Using SiteMinder 37-7
Configuring SSO with the HTTP Form Protocol 37-9
Authenticating with Digital Certificates 37-15
Creating and Applying WebVPN Policies 37-15
Creating Port Forwarding, URL, and Access Lists in Global Configuration Mode 37-16
Assigning Lists to Group Policies and Users in Group-Policy or User Mode 37-16
Enabling Features for Group Policies and Users 37-16
Assigning Users to Group Policies 37-16
Using the Security Appliance Authentication Server 37-16
Using a RADIUS Server 37-16
Configuring WebVPN Tunnel Group Attributes
37-17
Configuring WebVPN Group Policy and User Attributes
37-17
Configuring Application Access 37-18
Downloading the Port-Forwarding Applet Automatically 37-18
Closing Application Access to Prevent hosts File Errors 37-18
Recovering from hosts File Errors When Using Application Access
Understanding the hosts File 37-19
Stopping Application Access Improperly 37-19
Reconfiguring a hosts File 37-20
Configuring File Access
37-18
37-22
Configuring Access to Citrix MetaFrame Services
Using WebVPN with PDAs
37-24
37-25
Using E-Mail over WebVPN 37-26
Configuring E-mail Proxies 37-26
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E-mail Proxy Certificate Authentication 37-27
Configuring MAPI 37-27
Configuring Web E-mail: MS Outlook Web Access 37-27
Optimizing WebVPN Performance 37-28
Configuring Caching 37-28
Configuring Content Transformation 37-28
Configuring a Certificate for Signing Rewritten Java Content 37-29
Disabling Content Rewrite 37-29
Using Proxy Bypass 37-29
Configuring Application Profile Customization Framework 37-30
APCF Syntax 37-30
APCF Example 37-32
WebVPN End User Setup 37-32
Defining the End User Interface 37-32
Viewing the WebVPN Home Page 37-33
Viewing the WebVPN Application Access Panel 37-33
Viewing the Floating Toolbar 37-34
Customizing WebVPN Pages 37-35
Using Cascading Style Sheet Parameters 37-35
Customizing the WebVPN Login Page 37-36
Customizing the WebVPN Logout Page 37-37
Customizing the WebVPN Home Page 37-38
Customizing the Application Access Window 37-40
Customizing the Prompt Dialogs 37-41
Applying Customizations to Tunnel Groups, Groups and Users
Requiring Usernames and Passwords 37-43
Communicating Security Tips 37-44
Configuring Remote Systems to Use WebVPN Features 37-44
Capturing WebVPN Data 37-50
Creating a Capture File 37-51
Using a Browser to Display Capture Data
CHAPTER
38
Configuring SSL VPN Client
37-42
37-51
38-1
Installing SVC 38-1
Platform Requirements 38-1
Installing the SVC Software 38-2
Enabling SVC
38-3
Enabling Permanent SVC Installation
Enabling Rekey
38-4
38-5
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Enabling and Adjusting Dead Peer Detection
Enabling Keepalive
38-6
Using SVC Compression
Viewing SVC Sessions
38-6
38-7
Logging Off SVC Sessions
Updating SVCs
CHAPTER
39
38-5
38-8
38-8
Configuring Certificates
39-1
Public Key Cryptography 39-1
About Public Key Cryptography 39-1
Certificate Scalability 39-2
About Key Pairs 39-2
About Trustpoints 39-3
About Revocation Checking 39-3
About CRLs 39-3
About OCSP 39-4
Supported CA Servers 39-5
Certificate Configuration 39-5
Preparing for Certificates 39-5
Configuring Key Pairs 39-6
Generating Key Pairs 39-6
Removing Key Pairs 39-7
Configuring Trustpoints 39-7
Obtaining Certificates 39-9
Obtaining Certificates with SCEP 39-9
Obtaining Certificates Manually 39-11
Configuring CRLs for a Trustpoint 39-13
Exporting and Importing Trustpoints 39-14
Exporting a Trustpoint Configuration 39-15
Importing a Trustpoint Configuration 39-15
Configuring CA Certificate Map Rules 39-15
PART
System Administration
4
CHAPTER
40
Managing System Access
Allowing Telnet Access
40-1
40-1
Allowing SSH Access 40-2
Configuring SSH Access
40-2
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Using an SSH Client
40-3
Allowing HTTPS Access for ASDM
40-3
Configuring ASDM and WebVPN on the Same Interface
40-4
Configuring AAA for System Administrators 40-5
Configuring Authentication for CLI Access 40-5
Configuring Authentication To Access Privileged EXEC Mode 40-6
Configuring Authentication for the Enable Command 40-6
Authenticating Users Using the Login Command 40-6
Configuring Command Authorization 40-7
Command Authorization Overview 40-7
Configuring Local Command Authorization 40-8
Configuring TACACS+ Command Authorization 40-11
Configuring Command Accounting 40-14
Viewing the Current Logged-In User 40-14
Recovering from a Lockout 40-15
Configuring a Login Banner
CHAPTER
41
40-16
Managing Software, Licenses, and Configurations
41-1
Managing Licenses 41-1
Obtaining an Activation Key 41-1
Entering a New Activation Key 41-2
Viewing Files in Flash Memory
41-2
Downloading Software or Configuration Files to Flash Memory 41-3
Downloading a File to a Specific Location 41-3
Downloading a File to the Startup or Running Configuration 41-4
Configuring the Application Image and ASDM Image to Boot
Configuring the File to Boot as the Startup Configuration
41-5
41-5
Performing Zero Downtime Upgrades for Failover Pairs 41-6
Upgrading an Active/Standby Failover Configuration 41-6
Upgrading and Active/Active Failover Configuration 41-7
Backing Up Configuration Files 41-8
Backing up the Single Mode Configuration or Multiple Mode System Configuration
Backing Up a Context Configuration in Flash Memory 41-8
Backing Up a Context Configuration within a Context 41-9
Copying the Configuration from the Terminal Display 41-9
41-8
Configuring Auto Update Support 41-9
Configuring Communication with an Auto Update Server 41-9
Configuring Client Updates as an Auto Update Server 41-11
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Viewing Auto Update Status
CHAPTER
42
Monitoring the Security Appliance
41-12
42-1
Using SNMP 42-1
SNMP Overview 42-1
Enabling SNMP 42-3
Configuring and Managing Logs 42-5
Logging Overview 42-5
Logging in Multiple Context Mode 42-5
Enabling and Disabling Logging 42-6
Enabling Logging to All Configured Output Destinations 42-6
Disabling Logging to All Configured Output Destinations 42-6
Viewing the Log Configuration 42-6
Configuring Log Output Destinations 42-7
Sending System Log Messages to a Syslog Server 42-7
Sending System Log Messages to the Console Port 42-8
Sending System Log Messages to an E-mail Address 42-9
Sending System Log Messages to ASDM 42-10
Sending System Log Messages to a Telnet or SSH Session 42-11
Sending System Log Messages to the Log Buffer 42-12
Filtering System Log Messages 42-14
Message Filtering Overview 42-15
Filtering System Log Messages by Class 42-15
Filtering System Log Messages with Custom Message Lists 42-17
Customizing the Log Configuration 42-18
Customizing the Log Configuration 42-18
Configuring the Logging Queue 42-19
Including the Date and Time in System Log Messages 42-19
Including the Device ID in System Log Messages 42-19
Generating System Log Messages in EMBLEM Format 42-20
Disabling a System Log Message 42-20
Changing the Severity Level of a System Log Message 42-21
Changing the Amount of Internal Flash Memory Available for Logs 42-22
Understanding System Log Messages 42-23
System Log Message Format 42-23
Severity Levels 42-23
CHAPTER
43
Troubleshooting the Security Appliance
Testing Your Configuration
43-1
43-1
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Enabling ICMP Debug Messages and System Messages
Pinging Security Appliance Interfaces 43-2
Pinging Through the Security Appliance 43-4
Disabling the Test Configuration 43-5
Traceroute 43-6
Packet Tracer 43-6
Reloading the Security Appliance
43-1
43-6
Performing Password Recovery 43-6
Performing Password Recovery for the ASA 5500 Series Adaptive Security Appliance
Password Recovery for the PIX 500 Series Security Appliance 43-8
Disabling Password Recovery 43-9
Resetting the Password on the SSM Hardware Module 43-10
43-7
Other Troubleshooting Tools 43-10
Viewing Debug Messages 43-10
Capturing Packets 43-11
Viewing the Crash Dump 43-11
Common Problems
PART
2
43-11
Reference
Supported Platforms and Feature Licenses
Security Services Module Support
A-1
A-9
VPN Specifications A-10
Cisco VPN Client Support A-11
Cisco Secure Desktop Support A-11
Site-to-Site VPN Compatibility A-11
Cryptographic Standards A-12
Example 1: Multiple Mode Firewall With Outside Access
Example 1: System Configuration B-2
Example 1: Admin Context Configuration B-4
Example 1: Customer A Context Configuration B-4
Example 1: Customer B Context Configuration B-4
Example 1: Customer C Context Configuration B-5
B-1
Example 2: Single Mode Firewall Using Same Security Level
B-6
Example 3: Shared Resources for Multiple Contexts B-8
Example 3: System Configuration B-9
Example 3: Admin Context Configuration B-9
Example 3: Department 1 Context Configuration B-10
Example 3: Department 2 Context Configuration B-11
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Example 4: Multiple Mode, Transparent Firewall with Outside Access
Example 4: System Configuration B-13
Example 4: Admin Context Configuration B-14
Example 4: Customer A Context Configuration B-15
Example 4: Customer B Context Configuration B-15
Example 4: Customer C Context Configuration B-16
Example 5: WebVPN Configuration
Example 6: IPv6 Configuration
B-12
B-16
B-18
Example 7: Cable-Based Active/Standby Failover (Routed Mode)
Example 8: LAN-Based Active/Standby Failover (Routed Mode)
Example 8: Primary Unit Configuration B-21
Example 8: Secondary Unit Configuration B-22
B-20
B-21
Example 9: LAN-Based Active/Active Failover (Routed Mode) B-22
Example 9: Primary Unit Configuration B-23
Example 9: Primary System Configuration B-23
Example 9: Primary admin Context Configuration B-24
Example 9: Primary ctx1 Context Configuration B-25
Example 9: Secondary Unit Configuration B-25
Example 10: Cable-Based Active/Standby Failover (Transparent Mode)
Example 11: LAN-Based Active/Standby Failover (Transparent Mode)
Example 11: Primary Unit Configuration B-27
Example 11: Secondary Unit Configuration B-28
Example 12: LAN-Based Active/Active Failover (Transparent Mode)
Example 12: Primary Unit Configuration B-29
Example 12: Primary System Configuration B-29
Example 12: Primary admin Context Configuration B-30
Example 12: Primary ctx1 Context Configuration B-31
Example 12: Secondary Unit Configuration B-31
Example 13: Dual ISP Support Using Static Route Tracking
Example 14: ASA 5505 Base License
B-26
B-27
B-28
B-31
B-33
Example 15: ASA 5505 Security Plus License with Failover and Dual-ISP Backup
Example 15: Primary Unit Configuration B-35
Example 15: Secondary Unit Configuration B-37
B-35
Example 16: Network Traffic Diversion B-37
Inspecting All Traffic with the AIP SSM B-43
Inspecting Specific Traffic with the AIP SSM B-44
Verifying the Recording of Alert Events B-45
Troubleshooting the Configuration B-47
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Firewall Mode and Security Context Mode
Command Modes and Prompts
Syntax Formatting
C-2
C-3
Abbreviating Commands
C-3
Command-Line Editing
C-3
Command Completion
C-4
Command Help
C-1
C-4
Filtering show Command Output
Command Output Paging
Adding Comments
C-4
C-5
C-6
Text Configuration Files C-6
How Commands Correspond with Lines in the Text File C-6
Command-Specific Configuration Mode Commands C-6
Automatic Text Entries C-7
Line Order C-7
Commands Not Included in the Text Configuration C-7
Passwords C-7
Multiple Security Context Files C-7
IPv4 Addresses and Subnet Masks D-1
Classes D-1
Private Networks D-2
Subnet Masks D-2
Determining the Subnet Mask D-3
Determining the Address to Use with the Subnet Mask
D-3
IPv6 Addresses D-5
IPv6 Address Format D-5
IPv6 Address Types D-6
Unicast Addresses D-6
Multicast Address D-8
Anycast Address D-9
Required Addresses D-10
IPv6 Address Prefixes D-10
Protocols and Applications
TCP and UDP Ports
D-11
Local Ports and Protocols
ICMP Types
D-11
D-14
D-15
Selecting LDAP, RADIUS, or Local Authentication and Authorization
Understanding Policy Enforcement of Permissions and Attributes
E-1
E-2
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Configuring an External LDAP Server E-2
Reviewing the LDAP Directory Structure and Configuration Procedure E-3
Organizing the Security Appliance LDAP Schema E-3
Searching the Hierarchy E-4
Binding the Security Appliance to the LDAP Server E-5
Defining the Security Appliance LDAP Schema E-5
Cisco -AV-Pair Attribute Syntax E-14
Example Security Appliance Authorization Schema E-15
Loading the Schema in the LDAP Server E-18
Defining User Permissions E-18
Example User File E-18
Reviewing Examples of Active Directory Configurations E-19
Example 1: Configuring LDAP Authorization with Microsoft Active Directory (ASA/PIX) E-19
Example 2: Configuring LDAP Authentication with Microsoft Active Directory E-20
Example 3: LDAP Authentication and LDAP Authorization with Microsoft Active Directory E-22
Configuring an External RADIUS Server E-24
Reviewing the RADIUS Configuration Procedure E-24
Security Appliance RADIUS Authorization Attributes E-25
Security Appliance TACACS+ Attributes E-32
GLOSSARY
INDEX
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About This Guide
This preface introduce the Cisco Security Appliance Command Line Configuration Guide, and includes
the following sections:
•
Document Objectives, page xxxv
•
Audience, page xxxv
•
Related Documentation, page xxxvi
•
Document Organization, page xxxvi
•
Document Conventions, page xxxix
•
Obtaining Documentation and Submitting a Service Request, page xxxix
Document Objectives
The purpose of this guide is to help you configure the security appliance using the command-line
interface. This guide does not cover every feature, but describes only the most common configuration
scenarios.
You can also configure and monitor the security appliance by using ASDM, a web-based GUI
application. ASDM includes configuration wizards to guide you through some common configuration
scenarios, and online Help for less common scenarios. For more information, see:
http://www.cisco.com/univercd/cc/td/doc/product/netsec/secmgmt/asdm/index.htm
This guide applies to the Cisco PIX 500 series security appliances (PIX 515E, PIX 525, and PIX 535)
and the Cisco ASA 5500 series security appliances (ASA 5505, ASA 5510, ASA 5520, ASA 5540, and
ASA 5550). Throughout this guide, the term “security appliance” applies generically to all supported
models, unless specified otherwise. The PIX 501, PIX 506E, and PIX 520 security appliances are not
supported.
Audience
This guide is for network managers who perform any of the following tasks:
•
Manage network security
•
Install and configure firewalls/security appliances
•
Configure VPNs
•
Configure intrusion detection software
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Related Documentation
For more information, refer to the following documentation:
•
Cisco PIX Security Appliance Release Notes
•
Cisco ASDM Release Notes
•
Cisco PIX 515E Quick Start Guide
•
Guide for Cisco PIX 6.2 and 6.3 Users Upgrading to Cisco PIX Software Version 7.0
•
Migrating to ASA for VPN 3000 Series Concentrator Administrators
•
Cisco Security Appliance Command Reference
•
Cisco ASA 5500 Series Adaptive Security Appliance Getting Started Guide
•
Cisco ASA 5500 Series Release Notes
•
Cisco Security Appliance Logging Configuration and System Log Messages
•
Cisco Secure Desktop Configuration Guide for Cisco ASA 5500 Series Administrators
Document Organization
This guide includes the chapters and appendixes described in Table 1.
Table 1
Document Organization
Chapter/Appendix
Definition
Part 1: Getting Started and General Information
Chapter 1, “Introduction to the
Security Appliance”
Provides a high-level overview of the security appliance.
Chapter 2, “Getting Started”
Describes how to access the command-line interface, configure the firewall mode, and
work with the configuration.
Chapter 3, “Enabling Multiple
Context Mode”
Describes how to use security contexts and enable multiple context mode.
Chapter 4, “Configuring Switch
Ports and VLAN Interfaces for
the Cisco ASA 5505 Adaptive
Security Appliance”
Describes how to configure switch ports and VLAN interfaces for the ASA 5505 adaptive
security appliance.
Chapter 5, “Configuring
Ethernet Settings and
Subinterfaces”
Describes how to configure Ethernet settings for physical interfaces and add subinterfaces.
Chapter 6, “Adding and
Managing Security Contexts”
Describes how to configure multiple security contexts on the security appliance.
Chapter 7, “Configuring
Interface Parameters”
Describes how to configure each interface and subinterface for a name, security, level, and
IP address.
Chapter 8, “Configuring Basic
Settings”
Describes how to configure basic settings that are typically required for a functioning
configuration.
Chapter 9, “Configuring IP
Routing”
Describes how to configure IP routing.
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Table 1
Document Organization (continued)
Chapter/Appendix
Definition
Chapter 10, “Configuring
DHCP, DDNS, and WCCP
Services”
Describes how to configure the DHCP server and DHCP relay.
Chapter 11, “Configuring
Multicast Routing”
Describes how to configure multicast routing.
Chapter 12, “Configuring IPv6”
Describes how to enable and configure IPv6.
Chapter 13, “Configuring AAA Describes how to configure AAA servers and the local database.
Servers and the Local Database”
Chapter 14, “Configuring
Failover”
Describes the failover feature, which lets you configure two security appliances so that one
will take over operation if the other one fails.
Part 2: Configuring the Firewall
Chapter 15, “Firewall Mode
Overview”
Describes in detail the two operation modes of the security appliance, routed and
transparent mode, and how data is handled differently with each mode.
Chapter 16, “Identifying Traffic
with Access Lists”
Describes how to identify traffic with access lists.
Chapter 17, “Applying NAT”
Describes how address translation is performed.
Chapter 18, “Permitting or
Denying Network Access”
Describes how to control network access through the security appliance using access lists.
Chapter 19, “Applying AAA for Describes how to enable AAA for network access.
Network Access”
Chapter 20, “Applying Filtering
Services”
Describes ways to filter web traffic to reduce security risks or prevent inappropriate use.
Chapter 21, “Using Modular
Policy Framework”
Describes how to use the Modular Policy Framework to create security policies for TCP,
general connection settings, inspection, and QoS.
Chapter 22, “Managing AIP
SSM and CSC SSM”
Describes how to configure the security appliance to send traffic to an AIP SSM or a CSC
SSM, how to check the status of an SSM, and how to update the software image on an
intelligent SSM.
Chapter 23, “Preventing
Network Attacks”
Describes how to configure protection features to intercept and respond to network attacks.
Chapter 24, “Configuring QoS”
Describes how to configure the network to provide better service to selected network
traffic over various technologies, including Frame Relay, Asynchronous Transfer Mode
(ATM), Ethernet and 802.1 networks, SONET, and IP routed networks.
Chapter 25, “Configuring
Application Layer Protocol
Inspection”
Describes how to use and configure application inspection.
Chapter 26, “Configuring
ARP Inspection and Bridging
Parameters”
Describes how to enable ARP inspection and how to customize bridging operations.
Part 3: Configuring VPN
Chapter 27, “Configuring IPSec
and ISAKMP”
Describes how to configure ISAKMP and IPSec tunneling to build and manage VPN
“tunnels,” or secure connections between remote users and a private corporate network.
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Table 1
Document Organization (continued)
Chapter/Appendix
Definition
Chapter 28, “Configuring L2TP
over IPSec”
Describes how to configure IPSec over L2TP on the security appliance.
Chapter 29, “Setting General
IPSec VPN Parameters”
Describes miscellaneous VPN configuration procedures.
Chapter 30, “Configuring
Tunnel Groups, Group Policies,
and Users”
Describes how to configure VPN tunnel groups, group policies, and users.
Chapter 31, “Configuring IP
Addresses for VPNs”
Describes how to configure IP addresses in your private network addressing scheme, which
let the client function as a tunnel endpoint.
Chapter 32, “Configuring
Remote Access IPSec VPNs”
Describes how to configure a remote access VPN connection.
Chapter 33, “Configuring
Network Admission Control”
Describes how to configure Network Admission Control (NAC).
Chapter 34, “Configuring Easy Describes how to configure Easy VPN on the ASA 5505 adaptive security appliance.
VPN Services on the ASA 5505”
Chapter 35, “Configuring the
PPPoE Client”
Describes how to configure the PPPoE client provided with the security appliance.
Chapter 36, “Configuring
LAN-to-LAN IPSec VPNs”
Describes how to build a LAN-to-LAN VPN connection.
Chapter 37, “Configuring
WebVPN”
Describes how to establish a secure, remote-access VPN tunnel to a security appliance
using a web browser.
Chapter 38, “Configuring SSL
VPN Client”
Describes how to install and configure the SSL VPN Client.
Chapter 39, “Configuring
Certificates”
Describes how to configure a digital certificates, which contains information that identifies
a user or device. Such information can include a name, serial number, company,
department, or IP address. A digital certificate also contains a copy of the public key for
the user or device.
Part 4: System Administration
Chapter 40, “Managing System
Access”
Describes how to access the security appliance for system management through Telnet,
SSH, and HTTPS.
Chapter 41, “Managing
Software, Licenses, and
Configurations”
Describes how to enter license keys and download software and configurations files.
Chapter 42, “Monitoring the
Security Appliance”
Describes how to monitor the security appliance.
Chapter 43, “Troubleshooting
the Security Appliance”
Describes how to troubleshoot the security appliance.
Part 4: Reference
Appendix A, “Feature Licenses
and Specifications”
Describes the feature licenses and specifications.
Appendix B, “Sample
Configurations”
Describes a number of common ways to implement the security appliance.
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Table 1
Document Organization (continued)
Chapter/Appendix
Definition
Appendix C, “Using the
Command-Line Interface”
Describes how to use the CLI to configure the the security appliance.
Appendix D, “Addresses,
Protocols, and Ports”
Provides a quick reference for IP addresses, protocols, and applications.
Appendix E, “Configuring an
External Server for
Authorization and
Authentication”
Provides information about configuring LDAP and RADIUS authorization servers.
“Glossary”
Provides a handy reference for commonly-used terms and acronyms.
“Index”
Provides an index for the guide.
Document Conventions
Command descriptions use these conventions:
•
Braces ({ }) indicate a required choice.
•
Square brackets ([ ]) indicate optional elements.
•
Vertical bars ( | ) separate alternative, mutually exclusive elements.
•
Boldface indicates commands and keywords that are entered literally as shown.
•
Italics indicate arguments for which you supply values.
Examples use these conventions:
Note
•
Examples depict screen displays and the command line in screen font.
•
Information you need to enter in examples is shown in boldface screen font.
•
Variables for which you must supply a value are shown in italic screen font.
Means reader take note. Notes contain helpful suggestions or references to material not covered in the
manual.
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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A R T
1
Getting Started and General Information
CH A P T E R
1
Introduction to the Security Appliance
The security appliance combines advanced stateful firewall and VPN concentrator functionality in one
device, and for some models, an integrated intrusion prevention module called the AIP SSM or an
integrated content security and control module called the CSC SSM. The security appliance includes
many advanced features, such as multiple security contexts (similar to virtualized firewalls), transparent
(Layer 2) firewall or routed (Layer 3) firewall operation, advanced inspection engines, IPSec and
WebVPN support, and many more features. See Appendix A, “Feature Licenses and Specifications,” for
a list of supported platforms and features. For a list of new features, see the Cisco ASA 5500 Series
Release Notes or the Cisco PIX Security Appliance Release Notes.
Note
The Cisco PIX 501 and PIX 506E security appliances are not supported.
This chapter includes the following sections:
•
Firewall Functional Overview, page 1-1
•
VPN Functional Overview, page 1-5
•
Intrusion Prevention Services Functional Overview, page 1-5
•
Security Context Overview, page 1-6
Firewall Functional Overview
Firewalls protect inside networks from unauthorized access by users on an outside network. A firewall
can also protect inside networks from each other, for example, by keeping a human resources network
separate from a user network. If you have network resources that need to be available to an outside user,
such as a web or FTP server, you can place these resources on a separate network behind the firewall,
called a demilitarized zone (DMZ). The firewall allows limited access to the DMZ, but because the DMZ
only includes the public servers, an attack there only affects the servers and does not affect the other
inside networks. You can also control when inside users access outside networks (for example, access to
the Internet), by allowing only certain addresses out, by requiring authentication or authorization, or by
coordinating with an external URL filtering server.
When discussing networks connected to a firewall, the outside network is in front of the firewall, the
inside network is protected and behind the firewall, and a DMZ, while behind the firewall, allows limited
access to outside users. Because the security appliance lets you configure many interfaces with varied
security policies, including many inside interfaces, many DMZs, and even many outside interfaces if
desired, these terms are used in a general sense only.
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Firewall Functional Overview
This section includes the following topics:
•
Security Policy Overview, page 1-2
•
Firewall Mode Overview, page 1-3
•
Stateful Inspection Overview, page 1-4
Security Policy Overview
A security policy determines which traffic is allowed to pass through the firewall to access another
network. By default, the security appliance allows traffic to flow freely from an inside network (higher
security level) to an outside network (lower security level). You can apply actions to traffic to customize
the security policy. This section includes the following topics:
•
Permitting or Denying Traffic with Access Lists, page 1-2
•
Applying NAT, page 1-2
•
Using AAA for Through Traffic, page 1-2
•
Applying HTTP, HTTPS, or FTP Filtering, page 1-3
•
Applying Application Inspection, page 1-3
•
Sending Traffic to the Advanced Inspection and Prevention Security Services Module, page 1-3
•
Sending Traffic to the Content Security and Control Security Services Module, page 1-3
•
Applying QoS Policies, page 1-3
•
Applying Connection Limits and TCP Normalization, page 1-3
Permitting or Denying Traffic with Access Lists
You can apply an access list to limit traffic from inside to outside, or allow traffic from outside to inside.
For transparent firewall mode, you can also apply an EtherType access list to allow non-IP traffic.
Applying NAT
Some of the benefits of NAT include the following:
•
You can use private addresses on your inside networks. Private addresses are not routable on the
Internet.
•
NAT hides the local addresses from other networks, so attackers cannot learn the real address of a
host.
•
NAT can resolve IP routing problems by supporting overlapping IP addresses.
Using AAA for Through Traffic
You can require authentication and/or authorization for certain types of traffic, for example, for HTTP.
The security appliance also sends accounting information to a RADIUS or TACACS+ server.
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Firewall Functional Overview
Applying HTTP, HTTPS, or FTP Filtering
Although you can use access lists to prevent outbound access to specific websites or FTP servers,
configuring and managing web usage this way is not practical because of the size and dynamic nature of
the Internet. We recommend that you use the security appliance in conjunction with a separate server
running one of the following Internet filtering products:
•
Websense Enterprise
•
Secure Computing SmartFilter
Applying Application Inspection
Inspection engines are required for services that embed IP addressing information in the user data packet
or that open secondary channels on dynamically assigned ports. These protocols require the security
appliance to do a deep packet inspection.
Sending Traffic to the Advanced Inspection and Prevention Security Services Module
If your model supports the AIP SSM for intrusion prevention, then you can send traffic to the AIP SSM
for inspection.
Sending Traffic to the Content Security and Control Security Services Module
If your model supports it, the CSC SSM provides protection against viruses, spyware, spam, and other
unwanted traffic. It accomplishes this by scanning the FTP, HTTP, POP3, and SMTP traffic that you
configure the adaptive security appliance to send to it.
Applying QoS Policies
Some network traffic, such as voice and streaming video, cannot tolerate long latency times. QoS is a
network feature that lets you give priority to these types of traffic. QoS refers to the capability of a
network to provide better service to selected network traffic.
Applying Connection Limits and TCP Normalization
You can limit TCP and UDP connections and embryonic connections. Limiting the number of
connections and embryonic connections protects you from a DoS attack. The security appliance uses the
embryonic limit to trigger TCP Intercept, which protects inside systems from a DoS attack perpetrated
by flooding an interface with TCP SYN packets. An embryonic connection is a connection request that
has not finished the necessary handshake between source and destination.
TCP normalization is a feature consisting of advanced TCP connection settings designed to drop packets
that do not appear normal.
Firewall Mode Overview
The security appliance runs in two different firewall modes:
•
Routed
•
Transparent
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Firewall Functional Overview
In routed mode, the security appliance is considered to be a router hop in the network.
In transparent mode, the security appliance acts like a “bump in the wire,” or a “stealth firewall,” and is
not considered a router hop. The security appliance connects to the same network on its inside and
outside interfaces.
You might use a transparent firewall to simplify your network configuration. Transparent mode is also
useful if you want the firewall to be invisible to attackers. You can also use a transparent firewall for
traffic that would otherwise be blocked in routed mode. For example, a transparent firewall can allow
multicast streams using an EtherType access list.
Stateful Inspection Overview
All traffic that goes through the security appliance is inspected using the Adaptive Security Algorithm
and either allowed through or dropped. A simple packet filter can check for the correct source address,
destination address, and ports, but it does not check that the packet sequence or flags are correct. A filter
also checks every packet against the filter, which can be a slow process.
A stateful firewall like the security appliance, however, takes into consideration the state of a packet:
•
Is this a new connection?
If it is a new connection, the security appliance has to check the packet against access lists and
perform other tasks to determine if the packet is allowed or denied. To perform this check, the first
packet of the session goes through the “session management path,” and depending on the type of
traffic, it might also pass through the “control plane path.”
The session management path is responsible for the following tasks:
– Performing the access list checks
– Performing route lookups
– Allocating NAT translations (xlates)
– Establishing sessions in the “fast path”
Note
The session management path and the fast path make up the “accelerated security path.”
Some packets that require Layer 7 inspection (the packet payload must be inspected or altered) are
passed on to the control plane path. Layer 7 inspection engines are required for protocols that have
two or more channels: a data channel, which uses well-known port numbers, and a control channel,
which uses different port numbers for each session. These protocols include FTP, H.323, and SNMP.
•
Is this an established connection?
If the connection is already established, the security appliance does not need to re-check packets;
most matching packets can go through the fast path in both directions. The fast path is responsible
for the following tasks:
– IP checksum verification
– Session lookup
– TCP sequence number check
– NAT translations based on existing sessions
– Layer 3 and Layer 4 header adjustments
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VPN Functional Overview
For UDP or other connectionless protocols, the security appliance creates connection state
information so that it can also use the fast path.
Data packets for protocols that require Layer 7 inspection can also go through the fast path.
Some established session packets must continue to go through the session management path or the
control plane path. Packets that go through the session management path include HTTP packets that
require inspection or content filtering. Packets that go through the control plane path include the
control packets for protocols that require Layer 7 inspection.
VPN Functional Overview
A VPN is a secure connection across a TCP/IP network (such as the Internet) that appears as a private
connection. This secure connection is called a tunnel. The security appliance uses tunneling protocols to
negotiate security parameters, create and manage tunnels, encapsulate packets, transmit or receive them
through the tunnel, and unencapsulate them. The security appliance functions as a bidirectional tunnel
endpoint: it can receive plain packets, encapsulate them, and send them to the other end of the tunnel
where they are unencapsulated and sent to their final destination. It can also receive encapsulated
packets, unencapsulate them, and send them to their final destination. The security appliance invokes
various standard protocols to accomplish these functions.
The security appliance performs the following functions:
•
Establishes tunnels
•
Negotiates tunnel parameters
•
Authenticates users
•
Assigns user addresses
•
Encrypts and decrypts data
•
Manages security keys
•
Manages data transfer across the tunnel
•
Manages data transfer inbound and outbound as a tunnel endpoint or router
The security appliance invokes various standard protocols to accomplish these functions.
Intrusion Prevention Services Functional Overview
The Cisco ASA 5500 series adaptive security appliance supports the AIP SSM, an intrusion prevention
services module that monitors and performs real-time analysis of network traffic by looking for
anomalies and misuse based on an extensive, embedded signature library. When the system detects
unauthorized activity, it can terminate the specific connection, permanently block the attacking host, log
the incident, and send an alert to the device manager. Other legitimate connections continue to operate
independently without interruption. For more information, see Configuring the Cisco Intrusion
Prevention System Sensor Using the Command Line Interface.
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Security Context Overview
Security Context Overview
You can partition a single security appliance into multiple virtual devices, known as security contexts.
Each context is an independent device, with its own security policy, interfaces, and administrators.
Multiple contexts are similar to having multiple standalone devices. Many features are supported in
multiple context mode, including routing tables, firewall features, IPS, and management. Some features
are not supported, including VPN and dynamic routing protocols.
In multiple context mode, the security appliance includes a configuration for each context that identifies
the security policy, interfaces, and almost all the options you can configure on a standalone device. The
system administrator adds and manages contexts by configuring them in the system configuration,
which, like a single mode configuration, is the startup configuration. The system configuration identifies
basic settings for the security appliance. The system configuration does not include any network
interfaces or network settings for itself; rather, when the system needs to access network resources (such
as downloading the contexts from the server), it uses one of the contexts that is designated as the admin
context.
The admin context is just like any other context, except that when a user logs into the admin context,
then that user has system administrator rights and can access the system and all other contexts.
Note
You can run all your contexts in routed mode or transparent mode; you cannot run some contexts in one
mode and others in another.
Multiple context mode supports static routing only.
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CH A P T E R
2
Getting Started
This chapter describes how to access the command-line interface, configure the firewall mode, and work
with the configuration. This chapter includes the following sections:
•
Getting Started with Your Platform Model, page 2-1
•
Factory Default Configurations, page 2-1
•
Accessing the Command-Line Interface, page 2-4
•
Setting Transparent or Routed Firewall Mode, page 2-5
•
Working with the Configuration, page 2-6
Getting Started with Your Platform Model
This guide applies to multiple security appliance platforms and models: the PIX 500 series security
appliances and the ASA 5500 series adaptive security appliances. There are some hardware differences
between the PIX and the ASA security appliance. Moreover, the ASA 5505 includes a built-in switch,
and requires some special configuration. For these hardware-based differences, the platforms or models
supported are noted directly in each section.
Some models do not support all features covered in this guide. For example, the ASA 5505 adaptive
security appliance does not support security contexts. This guide might not list each supported model
when discussing a feature. To determine the features that are supported for your model before you start
your configuration, see the “Supported Platforms and Feature Licenses” section on page A-1 for a
detailed list of the features supported for each model.
Factory Default Configurations
The factory default configuration is the configuration applied by Cisco to new security appliances. The
factory default configuration is supported on all models except for the PIX 525 and PIX 535 security
appliances.
For the PIX 515/515E and the ASA 5510 and higher security appliances, the factory default
configuration configures an interface for management so you can connect to it using ASDM, with which
you can then complete your configuration.
For the ASA 5505 adaptive security appliance, the factory default configuration configures interfaces
and NAT so that the security appliance is ready to use in your network immediately.
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Factory Default Configurations
The factory default configuration is available only for routed firewall mode and single context mode. See
Chapter 3, “Enabling Multiple Context Mode,” for more information about multiple context mode. See
the “Setting Transparent or Routed Firewall Mode” section on page 2-5 for more information about
routed and transparent firewall mode.
This section includes the following topics:
•
Restoring the Factory Default Configuration, page 2-2
•
ASA 5505 Default Configuration, page 2-2
•
ASA 5510 and Higher Default Configuration, page 2-3
•
PIX 515/515E Default Configuration, page 2-4
Restoring the Factory Default Configuration
To restore the factory default configuration, enter the following command:
hostname(config)# configure factory-default [ip_address [mask]]
If you specify the ip_address, then you set the inside or management interface IP address, depending on
your model, instead of using the default IP address of 192.168.1.1. The http command uses the subnet
you specify. Similarly, the dhcpd address command range consists of addresses within the subnet that
you specify.
After you restore the factory default configuration, save it to internal Flash memory using the write
memory command. The write memory command saves the running configuration to the default location
for the startup configuration, even if you previously configured the boot config command to set a
different location; when the configuration was cleared, this path was also cleared.
Note
This command also clears the boot system command, if present, along with the rest of the configuration.
The boot system command lets you boot from a specific image, including an image on the external Flash
memory card. The next time you reload the security appliance after restoring the factory configuration,
it boots from the first image in internal Flash memory; if you do not have an image in internal Flash
memory, the security appliance does not boot.
To configure additional settings that are useful for a full configuration, see the setup command.
ASA 5505 Default Configuration
The default factory configuration for the ASA 5505 adaptive security appliance configures the
following:
•
An inside VLAN 1 interface that includes the Ethernet 0/1 through 0/7 switch ports. If you did not
set the IP address in the configure factory-default command, then the VLAN 1 IP address and mask
are 192.168.1.1 and 255.255.255.0.
•
An outside VLAN 2 interface that includes the Ethernet 0/0 switch port. VLAN 2 derives its IP
address using DHCP.
•
The default route is also derived from DHCP.
•
All inside IP addresses are translated when accessing the outside using interface PAT.
•
By default, inside users can access the outside with an access list, and outside users are prevented
from accessing the inside.
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Factory Default Configurations
•
The DHCP server is enabled on the security appliance, so a PC connecting to the VLAN 1 interface
receives an address between 192.168.1.2 and 192.168.1.254.
•
The HTTP server is enabled for ASDM and is accessible to users on the 192.168.1.0 network.
The configuration consists of the following commands:
interface Ethernet 0/0
switchport access vlan 2
no shutdown
interface Ethernet 0/1
switchport access vlan 1
no shutdown
interface Ethernet 0/2
switchport access vlan 1
no shutdown
interface Ethernet 0/3
switchport access vlan 1
no shutdown
interface Ethernet 0/4
switchport access vlan 1
no shutdown
interface Ethernet 0/5
switchport access vlan 1
no shutdown
interface Ethernet 0/6
switchport access vlan 1
no shutdown
interface Ethernet 0/7
switchport access vlan 1
no shutdown
interface vlan2
nameif outside
no shutdown
ip address dhcp setroute
interface vlan1
nameif inside
ip address 192.168.1.1 255.255.255.0
security-level 100
no shutdown
global (outside) 1 interface
nat (inside) 1 0 0
http server enable
http 192.168.1.0 255.255.255.0 inside
dhcpd address 192.168.1.2-192.168.1.254 inside
dhcpd auto_config outside
dhcpd enable inside
logging asdm informational
ASA 5510 and Higher Default Configuration
The default factory configuration for the ASA 5510 and higher adaptive security appliance configures
the following:
•
The management interface, Management 0/0. If you did not set the IP address in the configure
factory-default command, then the IP address and mask are 192.168.1.1 and 255.255.255.0.
•
The DHCP server is enabled on the security appliance, so a PC connecting to the interface receives
an address between 192.168.1.2 and 192.168.1.254.
•
The HTTP server is enabled for ASDM and is accessible to users on the 192.168.1.0 network.
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Accessing the Command-Line Interface
The configuration consists of the following commands:
interface management 0/0
ip address 192.168.1.1 255.255.255.0
nameif management
security-level 100
no shutdown
asdm logging informational 100
asdm history enable
http server enable
http 192.168.1.0 255.255.255.0 management
dhcpd address 192.168.1.2-192.168.1.254 management
dhcpd lease 3600
dhcpd ping_timeout 750
dhcpd enable management
PIX 515/515E Default Configuration
The default factory configuration for the PIX 515/515E security appliance configures the following:
•
The inside Ethernet1 interface. If you did not set the IP address in the configure factory-default
command, then the IP address and mask are 192.168.1.1 and 255.255.255.0.
•
The DHCP server is enabled on the security appliance, so a PC connecting to the interface receives
an address between 192.168.1.2 and 192.168.1.254.
•
The HTTP server is enabled for ASDM and is accessible to users on the 192.168.1.0 network.
The configuration consists of the following commands:
interface ethernet 1
ip address 192.168.1.1 255.255.255.0
nameif management
security-level 100
no shutdown
asdm logging informational 100
asdm history enable
http server enable
http 192.168.1.0 255.255.255.0 management
dhcpd address 192.168.1.2-192.168.1.254 management
dhcpd lease 3600
dhcpd ping_timeout 750
dhcpd enable management
Accessing the Command-Line Interface
For initial configuration, access the command-line interface directly from the console port. Later, you
can configure remote access using Telnet or SSH according to Chapter 40, “Managing System Access.”
If your system is already in multiple context mode, then accessing the console port places you in the
system execution space. See Chapter 3, “Enabling Multiple Context Mode,” for more information about
multiple context mode.
Note
If you want to use ASDM to configure the security appliance instead of the command-line interface, you
can connect to the default management address of 192.168.1.1 (if your security appliance includes a
factory default configuration. See the “Factory Default Configurations” section on page 2-1.). On the
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Setting Transparent or Routed Firewall Mode
ASA 5510 and higher adaptive security appliances, the interface to which you connect with ASDM is
Management 0/0. For the ASA 5505 adaptive security appliance, the switch port to which you connect
with ASDM is any port, except for Ethernet 0/0. For the PIX 515/515E security appliance, the interface
to which you connect with ASDM is Ethernet 1. If you do not have a factory default configuration, follow
the steps in this section to access the command-line interface. You can then configure the minimum
parameters to access ASDM by entering the setup command.
To access the command-line interface, perform the following steps:
Step 1
Connect a PC to the console port using the provided console cable, and connect to the console using a
terminal emulator set for 9600 baud, 8 data bits, no parity, 1 stop bit, no flow control.
See the hardware guide that came with your security appliance for more information about the console
cable.
Step 2
Press the Enter key to see the following prompt:
hostname>
This prompt indicates that you are in user EXEC mode.
Step 3
To access privileged EXEC mode, enter the following command:
hostname> enable
The following prompt appears:
Password:
Step 4
Enter the enable password at the prompt.
By default, the password is blank, and you can press the Enter key to continue. See the “Changing the
Enable Password” section on page 8-1 to change the enable password.
The prompt changes to:
hostname#
To exit privileged mode, enter the disable, exit, or quit command.
Step 5
To access global configuration mode, enter the following command:
hostname# configure terminal
The prompt changes to the following:
hostname(config)#
To exit global configuration mode, enter the exit, quit, or end command.
Setting Transparent or Routed Firewall Mode
You can set the security appliance to run in routed firewall mode (the default) or transparent firewall
mode.
For multiple context mode, you can use only one firewall mode for all contexts. You must set the mode
in the system execution space.
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Working with the Configuration
When you change modes, the security appliance clears the configuration because many commands are
not supported for both modes. If you already have a populated configuration, be sure to back up your
configuration before changing the mode; you can use this backup for reference when creating your new
configuration. See the “Backing Up Configuration Files” section on page 41-8. For multiple context
mode, the system configuration is erased. This action removes any contexts from running. If you then
re-add a context that has an existing configuration that was created for the wrong mode, the context
configuration will not work correctly. Be sure to recreate your context configurations for the correct
mode before you re-add them, or add new contexts with new paths for the new configurations.
If you download a text configuration to the security appliance that changes the mode with the
firewall transparent command, be sure to put the command at the top of the configuration; the security
appliance changes the mode as soon as it reads the command and then continues reading the
configuration you downloaded. If the command is later in the configuration, the security appliance clears
all the preceding lines in the configuration. See the “Downloading Software or Configuration Files to
Flash Memory” section on page 41-3 for information about downloading text files.
•
To set the mode to transparent, enter the following command in the system execution space:
hostname(config)# firewall transparent
This command also appears in each context configuration for informational purposes only; you
cannot enter this command in a context.
•
To set the mode to routed, enter the following command in the system execution space:
hostname(config)# no firewall transparent
Working with the Configuration
This section describes how to work with the configuration. The security appliance loads the
configuration from a text file, called the startup configuration. This file resides by default as a hidden
file in internal Flash memory. You can, however, specify a different path for the startup configuration.
(For more information, see Chapter 41, “Managing Software, Licenses, and Configurations.”)
When you enter a command, the change is made only to the running configuration in memory. You must
manually save the running configuration to the startup configuration for your changes to remain after a
reboot.
The information in this section applies to both single and multiple security contexts, except where noted.
Additional information about contexts is in Chapter 3, “Enabling Multiple Context Mode.”
This section includes the following topics:
•
Saving Configuration Changes, page 2-6
•
Copying the Startup Configuration to the Running Configuration, page 2-8
•
Viewing the Configuration, page 2-8
•
Clearing and Removing Configuration Settings, page 2-9
•
Creating Text Configuration Files Offline, page 2-9
Saving Configuration Changes
This section describes how to save your configuration, and includes the following topics:
•
Saving Configuration Changes in Single Context Mode, page 2-7
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•
Saving Configuration Changes in Multiple Context Mode, page 2-7
Saving Configuration Changes in Single Context Mode
To save the running configuration to the startup configuration, enter the following command:
hostname# write memory
Note
The copy running-config startup-config command is equivalent to the write memory command.
Saving Configuration Changes in Multiple Context Mode
You can save each context (and system) configuration separately, or you can save all context
configurations at the same time. This section includes the following topics:
•
Saving Each Context and System Separately, page 2-7
•
Saving All Context Configurations at the Same Time, page 2-7
Saving Each Context and System Separately
To save the system or context configuration, enter the following command within the system or context:
hostname# write memory
Note
The copy running-config startup-config command is equivalent to the write memory command.
For multiple context mode, context startup configurations can reside on external servers. In this case, the
security appliance saves the configuration back to the server you identified in the context URL, except
for an HTTP or HTTPS URL, which do not let you save the configuration to the server.
Saving All Context Configurations at the Same Time
To save all context configurations at the same time, as well as the system configuration, enter the
following command in the system execution space:
hostname# write memory all [/noconfirm]
If you do not enter the /noconfirm keyword, you see the following prompt:
Are you sure [Y/N]:
After you enter Y, the security appliance saves the system configuration and each context. Context
startup configurations can reside on external servers. In this case, the security appliance saves the
configuration back to the server you identified in the context URL, except for an HTTP or HTTPS URL,
which do not let you save the configuration to the server.
After the security appliance saves each context, the following message appears:
‘Saving context ‘b’ ... ( 1/3 contexts saved ) ’
Sometimes, a context is not saved because of an error. See the following information for errors:
•
For contexts that are not saved because of low memory, the following message appears:
The context 'context a' could not be saved due to Unavailability of resources
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•
For contexts that are not saved because the remote destination is unreachable, the following message
appears:
The context 'context a' could not be saved due to non-reachability of destination
•
For contexts that are not saved because the context is locked, the following message appears:
Unable to save the configuration for the following contexts as these contexts are
locked.
context ‘a’ , context ‘x’ , context ‘z’ .
A context is only locked if another user is already saving the configuration or in the process of
deleting the context.
•
For contexts that are not saved because the startup configuration is read-only (for example, on an
HTTP server), the following message report is printed at the end of all other messages:
Unable to save the configuration for the following contexts as these contexts have
read-only config-urls:
context ‘a’ , context ‘b’ , context ‘c’ .
•
For contexts that are not saved because of bad sectors in the Flash memory, the following message
appears:
The context 'context a' could not be saved due to Unknown errors
Copying the Startup Configuration to the Running Configuration
Copy a new startup configuration to the running configuration using one of these options:
•
To merge the startup configuration with the running configuration, enter the following command:
hostname(config)# copy startup-config running-config
A merge adds any new commands from the new configuration to the running configuration. If the
configurations are the same, no changes occur. If commands conflict or if commands affect the
running of the context, then the effect of the merge depends on the command. You might get errors,
or you might have unexpected results.
•
To load the startup configuration and discard the running configuration, restart the security
appliance by entering the following command:
hostname# reload
Alternatively, you can use the following commands to load the startup configuration and discard the
running configuration without requiring a reboot:
hostname/contexta(config)# clear configure all
hostname/contexta(config)# copy startup-config running-config
Viewing the Configuration
The following commands let you view the running and startup configurations.
•
To view the running configuration, enter the following command:
hostname# show running-config
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•
To view the running configuration of a specific command, enter the following command:
hostname# show running-config command
•
To view the startup configuration, enter the following command:
hostname# show startup-config
Clearing and Removing Configuration Settings
To erase settings, enter one of the following commands.
•
To clear all the configuration for a specified command, enter the following command:
hostname(config)# clear configure configurationcommand [level2configurationcommand]
This command clears all the current configuration for the specified configuration command. If you
only want to clear the configuration for a specific version of the command, you can enter a value for
level2configurationcommand.
For example, to clear the configuration for all aaa commands, enter the following command:
hostname(config)# clear configure aaa
To clear the configuration for only aaa authentication commands, enter the following command:
hostname(config)# clear configure aaa authentication
•
To disable the specific parameters or options of a command, enter the following command:
hostname(config)# no configurationcommand [level2configurationcommand] qualifier
In this case, you use the no command to remove the specific configuration identified by qualifier.
For example, to remove a specific nat command, enter enough of the command to identify it
uniquely as follows:
hostname(config)# no nat (inside) 1
•
To erase the startup configuration, enter the following command:
hostname(config)# write erase
•
To erase the running configuration, enter the following command:
hostname(config)# clear configure all
Note
In multiple context mode, if you enter clear configure all from the system configuration, you
also remove all contexts and stop them from running.
Creating Text Configuration Files Offline
This guide describes how to use the CLI to configure the security appliance; when you save commands,
the changes are written to a text file. Instead of using the CLI, however, you can edit a text file directly
on your PC and paste a configuration at the configuration mode command-line prompt in its entirety, or
line by line. Alternatively, you can download a text file to the security appliance internal Flash memory.
See Chapter 41, “Managing Software, Licenses, and Configurations,” for information on downloading
the configuration file to the security appliance.
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Working with the Configuration
In most cases, commands described in this guide are preceded by a CLI prompt. The prompt in the
following example is “hostname(config)#”:
hostname(config)# context a
In the text configuration file you are not prompted to enter commands, so the prompt is omitted as
follows:
context a
For additional information about formatting the file, see Appendix C, “Using the Command-Line
Interface.”
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3
Enabling Multiple Context Mode
This chapter describes how to use security contexts and enable multiple context mode. This chapter
includes the following sections:
•
Security Context Overview, page 3-1
•
Enabling or Disabling Multiple Context Mode, page 3-10
Security Context Overview
You can partition a single security appliance into multiple virtual devices, known as security contexts.
Each context is an independent device, with its own security policy, interfaces, and administrators.
Multiple contexts are similar to having multiple standalone devices. Many features are supported in
multiple context mode, including routing tables, firewall features, IPS, and management. Some features
are not supported, including VPN and dynamic routing protocols.
This section provides an overview of security contexts, and includes the following topics:
•
Common Uses for Security Contexts, page 3-1
•
Unsupported Features, page 3-2
•
Context Configuration Files, page 3-2
•
How the Security Appliance Classifies Packets, page 3-3
•
Cascading Security Contexts, page 3-8
•
Management Access to Security Contexts, page 3-9
Common Uses for Security Contexts
You might want to use multiple security contexts in the following situations:
•
You are a service provider and want to sell security services to many customers. By enabling
multiple security contexts on the security appliance, you can implement a cost-effective,
space-saving solution that keeps all customer traffic separate and secure, and also eases
configuration.
•
You are a large enterprise or a college campus and want to keep departments completely separate.
•
You are an enterprise that wants to provide distinct security policies to different departments.
•
You have any network that requires more than one security appliance.
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Unsupported Features
Multiple context mode does not support the following features:
•
Dynamic routing protocols
Security contexts support only static routes. You cannot enable OSPF or RIP in multiple context
mode.
•
VPN
•
Multicast
Context Configuration Files
This section describes how the security appliance implements multiple context mode configurations and
includes the following sections:
•
Context Configurations, page 3-2
•
System Configuration, page 3-2
•
Admin Context Configuration, page 3-2
Context Configurations
The security appliance includes a configuration for each context that identifies the security policy,
interfaces, and almost all the options you can configure on a standalone device. You can store context
configurations on the internal Flash memory or the external Flash memory card, or you can download
them from a TFTP, FTP, or HTTP(S) server.
System Configuration
The system administrator adds and manages contexts by configuring each context configuration location,
allocated interfaces, and other context operating parameters in the system configuration, which, like a
single mode configuration, is the startup configuration. The system configuration identifies basic
settings for the security appliance. The system configuration does not include any network interfaces or
network settings for itself; rather, when the system needs to access network resources (such as
downloading the contexts from the server), it uses one of the contexts that is designated as the admin
context. The system configuration does include a specialized failover interface for failover traffic only.
Admin Context Configuration
The admin context is just like any other context, except that when a user logs in to the admin context,
then that user has system administrator rights and can access the system and all other contexts. The
admin context is not restricted in any way, and can be used as a regular context. However, because
logging into the admin context grants you administrator privileges over all contexts, you might need to
restrict access to the admin context to appropriate users. The admin context must reside on Flash
memory, and not remotely.
If your system is already in multiple context mode, or if you convert from single mode, the admin context
is created automatically as a file on the internal Flash memory called admin.cfg. This context is named
“admin.” If you do not want to use admin.cfg as the admin context, you can change the admin context.
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How the Security Appliance Classifies Packets
Each packet that enters the security appliance must be classified, so that the security appliance can
determine to which context to send a packet. This section includes the following topics:
Note
•
Valid Classifier Criteria, page 3-3
•
Invalid Classifier Criteria, page 3-4
•
Classification Examples, page 3-5
If the destination MAC address is a multicast or broadcast MAC address, the packet is duplicated and
delivered to each context.
Valid Classifier Criteria
This section describes the criteria used by the classifier, and includes the following topics:
•
Unique Interfaces, page 3-3
•
Unique MAC Addresses, page 3-3
•
NAT Configuration, page 3-3
Unique Interfaces
If only one context is associated with the ingress interface, the security appliance classifies the packet
into that context. In transparent firewall mode, unique interfaces for contexts are required, so this method
is used to classify packets at all times.
Unique MAC Addresses
If multiple contexts share an interface, then the classifier uses the interface MAC address. The security
appliance lets you assign a different MAC address in each context to the same shared interface, whether
it is a shared physical interface or a shared subinterface. By default, shared interfaces do not have unique
MAC addresses; the interface uses the physical interface burned-in MAC address in every context. An
upstream router cannot route directly to a context without unique MAC addresses. You can set the MAC
addresses manually when you configure each interface (see the “Configuring the Interface” section on
page 7-2), or you can automatically generate MAC addresses (see the “Automatically Assigning MAC
Addresses to Context Interfaces” section on page 6-11).
NAT Configuration
If you do not have unique MAC addresses, then the classifier intercepts the packet and performs a
destination IP address lookup. All other fields are ignored; only the destination IP address is used. To
use the destination address for classification, the classifier must have knowledge about the subnets
located behind each security context. The classifier relies on the NAT configuration to determine the
subnets in each context. The classifier matches the destination IP address to either a static command or
a global command. In the case of the global command, the classifier does not need a matching nat
command or an active NAT session to classify the packet. Whether the packet can communicate with the
destination IP address after classification depends on how you configure NAT and NAT control.
For example, the classifier gains knowledge about subnets 10.10.10.0, 10.20.10.0 and 10.30.10.0 when
the context administrators configure static commands in each context:
•
Context A:
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static (inside,shared) 10.10.10.0 10.10.10.0 netmask 255.255.255.0
•
Context B:
static (inside,shared) 10.20.10.0 10.20.10.0 netmask 255.255.255.0
•
Context C:
static (inside,shared) 10.30.10.0 10.30.10.0 netmask 255.255.255.0
Note
For management traffic destined for an interface, the interface IP address is used for classification.
Invalid Classifier Criteria
The following configurations are not used for packet classification:
•
NAT exemption—The classifier does not use a NAT exemption configuration for classification
purposes because NAT exemption does not identify a mapped interface.
•
Routing table—If a context includes a static route that points to an external router as the next-hop
to a subnet, and a different context includes a static command for the same subnet, then the classifier
uses the static command to classify packets destined for that subnet and ignores the static route.
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Classification Examples
Figure 3-2 shows multiple contexts sharing an outside interface. The classifier assigns the packet to
Context B because Context B includes the MAC address to which the router sends the packet.
Figure 3-1
Packet Classification with a Shared Interface using MAC Addresses
Internet
Packet Destination:
209.165.201.1 via MAC 000C.F142.4CDC
GE 0/0.1 (Shared Interface)
Classifier
Admin
Context
MAC 000C.F142.4CDB
Context A
GE 0/1.1
MAC 000C.F142.4CDC
Context B
GE 0/1.2
GE 0/1.3
Admin
Network
Inside
Customer A
Inside
Customer B
Host
209.165.202.129
Host
209.165.200.225
Host
209.165.201.1
153367
MAC 000C.F142.4CDA
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Figure 3-2 shows multiple contexts sharing an outside interface without MAC addresses assigned. The
classifier assigns the packet to Context B because Context B includes the address translation that
matches the destination address.
Figure 3-2
Packet Classification with a Shared Interface using NAT
Internet
Packet Destination:
209.165.201.3
GE 0/0.1 (Shared Interface)
Classifier
Admin
Context
Context A
Context B
Dest Addr Translation
209.165.201.3 10.1.1.13
GE 0/1.1
GE 0/1.2
GE 0/1.3
Inside
Customer A
Inside
Customer B
Host
10.1.1.13
Host
10.1.1.13
Host
10.1.1.13
92399
Admin
Network
Note that all new incoming traffic must be classified, even from inside networks. Figure 3-3 shows a host
on the Context B inside network accessing the Internet. The classifier assigns the packet to Context B
because the ingress interface is Gigabit Ethernet 0/1.3, which is assigned to Context B.
Note
If you share an inside interface and do not use unique MAC addresses, the classifier imposes some major
restrictions. The classifier relies on the address translation configuration to classify the packet within a
context, and you must translate the destination addresses of the traffic. Because you do not usually
perform NAT on outside addresses, sending packets from inside to outside on a shared interface is not
always possible; the outside network is large, (the Web, for example), and addresses are not predictable
for an outside NAT configuration. If you share an inside interface, we suggest you use unique MAC
addresses.
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Figure 3-3
Incoming Traffic from Inside Networks
Internet
GE 0/0.1
Admin
Context
Context A
Context B
Classifier
GE 0/1.1
GE 0/1.2
GE 0/1.3
Inside
Customer A
Inside
Customer B
Host
10.1.1.13
Host
10.1.1.13
Host
10.1.1.13
92395
Admin
Network
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For transparent firewalls, you must use unique interfaces. Figure 3-4 shows a host on the Context B
inside network accessing the Internet. The classifier assigns the packet to Context B because the ingress
interface is Gigabit Ethernet 1/0.3, which is assigned to Context B.
Figure 3-4
Transparent Firewall Contexts
Internet
Classifier
GE 0/0.2
GE 0/0.1
GE 0/0.3
Admin
Context
Context A
Context B
GE 1/0.1
GE 1/0.2
GE 1/0.3
Inside
Customer A
Inside
Customer B
Host
10.1.1.13
Host
10.1.2.13
Host
10.1.3.13
92401
Admin
Network
Cascading Security Contexts
Placing a context directly in front of another context is called cascading contexts; the outside interface
of one context is the same interface as the inside interface of another context. You might want to cascade
contexts if you want to simplify the configuration of some contexts by configuring shared parameters in
the top context.
Note
Cascading contexts requires that you configure unique MAC addresses for each context interface.
Because of the limitations of classifying packets on shared interfaces without MAC addresses, we do not
recommend using cascading contexts without unique MAC addresses.
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Figure 3-5 shows a gateway context with two contexts behind the gateway.
Figure 3-5
Cascading Contexts
Internet
GE 0/0.2
Outside
Gateway
Context
Inside
GE 0/0.1
(Shared Interface)
Outside
Outside
Admin
Context
Context A
Inside
GE 1/1.43
Inside
153366
GE 1/1.8
Management Access to Security Contexts
The security appliance provides system administrator access in multiple context mode as well as access
for individual context administrators. The following sections describe logging in as a system
administrator or as a a context administrator:
•
System Administrator Access, page 3-9
•
Context Administrator Access, page 3-10
System Administrator Access
You can access the security appliance as a system administrator in two ways:
•
Access the security appliance console.
From the console, you access the system execution space.
•
Access the admin context using Telnet, SSH, or ASDM.
See Chapter 40, “Managing System Access,” to enable Telnet, SSH, and SDM access.
As the system administrator, you can access all contexts.
When you change to a context from admin or the system, your username changes to the default
“enable_15” username. If you configured command authorization in that context, you need to either
configure authorization privileges for the “enable_15” user, or you can log in as a different name for
which you provide sufficient privileges in the command authorization configuration for the context. To
log in with a username, enter the login command. For example, you log in to the admin context with the
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username “admin.” The admin context does not have any command authorization configuration, but all
other contexts include command authorization. For convenience, each context configuration includes a
user “admin” with maximum privileges. When you change from the admin context to context A, your
username is altered, so you must log in again as “admin” by entering the login command. When you
change to context B, you must again enter the login command to log in as “admin.”
The system execution space does not support any AAA commands, but you can configure its own enable
password, as well as usernames in the local database to provide individual logins.
Context Administrator Access
You can access a context using Telnet, SSH, or ASDM. If you log in to a non-admin context, you can
only access the configuration for that context. You can provide individual logins to the context. See See
Chapter 40, “Managing System Access,” to enable Telnet, SSH, and SDM access and to configure
management authentication.
Enabling or Disabling Multiple Context Mode
Your security appliance might already be configured for multiple security contexts depending on how
you ordered it from Cisco. If you are upgrading, however, you might need to convert from single mode
to multiple mode by following the procedures in this section. ASDM does not support changing modes,
so you need to change modes using the CLI.
This section includes the following topics:
•
Backing Up the Single Mode Configuration, page 3-10
•
Enabling Multiple Context Mode, page 3-10
•
Restoring Single Context Mode, page 3-11
Backing Up the Single Mode Configuration
When you convert from single mode to multiple mode, the security appliance converts the running
configuration into two files. The original startup configuration is not saved, so if it differs from the
running configuration, you should back it up before proceeding.
Enabling Multiple Context Mode
The context mode (single or multiple) is not stored in the configuration file, even though it does endure
reboots. If you need to copy your configuration to another device, set the mode on the new device to
match using the mode command.
When you convert from single mode to multiple mode, the security appliance converts the running
configuration into two files: a new startup configuration that comprises the system configuration, and
admin.cfg that comprises the admin context (in the root directory of the internal Flash memory). The
original running configuration is saved as old_running.cfg (in the root directory of the internal Flash
memory). The original startup configuration is not saved. The security appliance automatically adds an
entry for the admin context to the system configuration with the name “admin.”
To enable multiple mode, enter the following command:
hostname(config)# mode multiple
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You are prompted to reboot the security appliance.
Restoring Single Context Mode
If you convert from multiple mode to single mode, you might want to first copy a full startup
configuration (if available) to the security appliance; the system configuration inherited from multiple
mode is not a complete functioning configuration for a single mode device. Because the system
configuration does not have any network interfaces as part of its configuration, you must access the
security appliance from the console to perform the copy.
To copy the old running configuration to the startup configuration and to change the mode to single
mode, perform the following steps in the system execution space:
Step 1
To copy the backup version of your original running configuration to the current startup configuration,
enter the following command in the system execution space:
hostname(config)# copy flash:old_running.cfg startup-config
Step 2
To set the mode to single mode, enter the following command in the system execution space:
hostname(config)# mode single
The security appliance reboots.
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Enabling Multiple Context Mode
Enabling or Disabling Multiple Context Mode
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4
Configuring Switch Ports and VLAN Interfaces
for the Cisco ASA 5505 Adaptive Security
Appliance
This chapter describes how to configure the switch ports and VLAN interfaces of the ASA 5505 adaptive
security appliance.
Note
To configure interfaces of other models, see Chapter 5, “Configuring Ethernet Settings and
Subinterfaces,” and Chapter 7, “Configuring Interface Parameters.”
This chapter includes the following sections:
•
Interface Overview, page 4-1
•
Configuring VLAN Interfaces, page 4-5
•
Configuring Switch Ports as Access Ports, page 4-9
•
Configuring a Switch Port as a Trunk Port, page 4-11
•
Allowing Communication Between VLAN Interfaces on the Same Security Level, page 4-13
Interface Overview
This section describes the ports and interfaces of the ASA 5505 adaptive security appliance, and includes
the following topics:
•
Understanding ASA 5505 Ports and Interfaces, page 4-2
•
Maximum Active VLAN Interfaces for Your License, page 4-2
•
Default Interface Configuration, page 4-4
•
VLAN MAC Addresses, page 4-4
•
Power Over Ethernet, page 4-4
•
Security Level Overview, page 4-5
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Interface Overview
Understanding ASA 5505 Ports and Interfaces
The ASA 5505 adaptive security appliance supports a built-in switch. There are two kinds of ports and
interfaces that you need to configure:
•
Physical switch ports—The adaptive security appliance has eight Fast Ethernet switch ports that
forward traffic at Layer 2, using the switching function in hardware. Two of these ports are PoE
ports. See the “Power Over Ethernet” section on page 4-4 for more information. You can connect
these interfaces directly to user equipment such as PCs, IP phones, or a DSL modem. Or you can
connect to another switch.
•
Logical VLAN interfaces—In routed mode, these interfaces forward traffic between VLAN
networks at Layer 3, using the configured security policy to apply firewall and VPN services. In
transparent mode, these interfaces forward traffic between the VLANs on the same network at Layer
2, using the configured security policy to apply firewall services. See the “Maximum Active VLAN
Interfaces for Your License” section for more information about the maximum VLAN interfaces.
VLAN interfaces let you divide your equipment into separate VLANs, for example, home, business,
and Internet VLANs.
To segregate the switch ports into separate VLANs, you assign each switch port to a VLAN interface.
Switch ports on the same VLAN can communicate with each other using hardware switching. But when
a switch port on VLAN 1 wants to communicate with a switch port on VLAN 2, then the adaptive
security appliance applies the security policy to the traffic and routes or bridges between the two
VLANs.
Note
Subinterfaces are not available for the ASA 5505 adaptive security appliance.
Maximum Active VLAN Interfaces for Your License
In transparent firewall mode, you can configure two active VLANs in the Base license and three active
VLANs in the Security Plus license, one of which must be for failover.
In routed mode, you can configure up to three active VLANs with the Base license, and up to 20 active
VLANs with the Security Plus license.
An active VLAN is a VLAN with a nameif command configured.
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Interface Overview
With the Base license, the third VLAN can only be configured to initiate traffic to one other VLAN. See
Figure 4-1 for an example network where the Home VLAN can communicate with the Internet, but
cannot initiate contact with Business.
Figure 4-1
ASA 5505 Adaptive Security Appliance with Base License
Internet
Home
153364
ASA 5505
with Base License
Business
With the Security Plus license, you can configure 20 VLAN interfaces. You can configure trunk ports to
accomodate multiple VLANs per port.
Note
The ASA 5505 adaptive security appliance supports Active/Standby failover, but not Stateful failover.
See Figure 4-2 for an example network.
Figure 4-2
ASA 5505 Adaptive Security Appliance with Security Plus License
Backup ISP
Primary ISP
ASA 5505
with Security Plus
License
Failover
ASA 5505
DMZ
Inside
153365
Failover Link
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Interface Overview
Default Interface Configuration
If your adaptive security appliance includes the default factory configuration, your interfaces are
configured as follows:
•
The outside interface (security level 0) is VLAN 2.
Ethernet0/0 is assigned to VLAN 2 and is enabled.
The VLAN 2 IP address is obtained from the DHCP server.
•
The inside interface (security level 100) is VLAN 1
Ethernet 0/1 through Ethernet 0/7 are assigned to VLAN 1 and is enabled.
VLAN 1 has IP address 192.168.1.1.
Restore the default factory configuration using the configure factory-default command.
Use the procedures in this chapter to modify the default configuration, for example, to add VLAN
interfaces.
If you do not have a factory default configuration, all switch ports are in VLAN 1, but no other
parameters are configured.
VLAN MAC Addresses
In routed firewall mode, all VLAN interfaces share a MAC address. Ensure that any connected switches
can support this scenario. If the connected switches require unique MAC addresses, you can manually
assign MAC addresses.
In transparent firewall mode, each VLAN has a unique MAC address. You can override the generated
MAC addresses if desired by manually assigning MAC addresses.
Power Over Ethernet
Ethernet 0/6 and Ethernet 0/7 support PoE for devices such as IP phones or wireless access points. If you
install a non-PoE device or do not connect to these switch ports, the adaptive security appliance does not
supply power to the switch ports.
If you shut down the switch port using the shutdown command, you disable power to the device. Power
is restored when you enter no shutdown. See the “Configuring Switch Ports as Access Ports” section on
page 4-9 for more information about shutting down a switch port.
To view the status of PoE switch ports, including the type of device connected (Cisco or IEEE 802.3af),
use the show power inline command.
Monitoring Traffic Using SPAN
If you want to monitor traffic that enters or exits one or more switch ports, you can enable SPAN, also
known as switch port monitoring. The port for which you enable SPAN (called the destination port)
receives a copy of every packet transmitted or received on a specified source port. The SPAN feature lets
you attach a sniffer to the destination port so you can monitor all traffic; without SPAN, you would have
to attach a sniffer to every port you want to monitor. You can only enable SPAN for one destination port.
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Configuring VLAN Interfaces
See the switchport monitor command in the Cisco Security Appliance Command Reference for more
information.
Security Level Overview
Each VLAN interface must have a security level in the range 0 to 100 (from lowest to highest). For
example, you should assign your most secure network, such as the inside business network, to level 100.
The outside network connected to the Internet can be level 0. Other networks, such as a home network
can be in between. You can assign interfaces to the same security level. See the “Allowing
Communication Between VLAN Interfaces on the Same Security Level” section on page 4-13 for more
information.
The level controls the following behavior:
•
Network access—By default, there is an implicit permit from a higher security interface to a lower
security interface (outbound). Hosts on the higher security interface can access any host on a lower
security interface. You can limit access by applying an access list to the interface.
For same security interfaces, there is an implicit permit for interfaces to access other interfaces on
the same security level or lower.
•
Inspection engines—Some application inspection engines are dependent on the security level. For
same security interfaces, inspection engines apply to traffic in either direction.
– NetBIOS inspection engine—Applied only for outbound connections.
– SQL*Net inspection engine—If a control connection for the SQL*Net (formerly OraServ) port
exists between a pair of hosts, then only an inbound data connection is permitted through the
adaptive security appliance.
•
Filtering—HTTP(S) and FTP filtering applies only for outbound connections (from a higher level
to a lower level).
For same security interfaces, you can filter traffic in either direction.
•
NAT control—When you enable NAT control, you must configure NAT for hosts on a higher security
interface (inside) when they access hosts on a lower security interface (outside).
Without NAT control, or for same security interfaces, you can choose to use NAT between any
interface, or you can choose not to use NAT. Keep in mind that configuring NAT for an outside
interface might require a special keyword.
•
established command—This command allows return connections from a lower security host to a
higher security host if there is already an established connection from the higher level host to the
lower level host.
For same security interfaces, you can configure established commands for both directions.
Configuring VLAN Interfaces
For each VLAN to pass traffic, you need to configure an interface name (the nameif command), and for
routed mode, an IP address. You should also change the security level from the default, which is 0. If
you name an interface “inside” and you do not set the security level explicitly, then the adaptive security
appliance sets the security level to 100.
For information about how many VLANs you can configure, see the “Maximum Active VLAN
Interfaces for Your License” section on page 4-2.
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Configuring VLAN Interfaces
Note
If you are using failover, do not use this procedure to name interfaces that you are reserving for failover
communications. See Chapter 14, “Configuring Failover,” to configure the failover link.
If you change the security level of an interface, and you do not want to wait for existing connections to
time out before the new security information is used, you can clear the connections using the
clear local-host command.
To configure a VLAN interface, perform the following steps:
Step 1
To specify the VLAN ID, enter the following command:
hostname(config)# interface vlan number
Where the number is between 1 and 4090.
For example, enter the following command:
hostname(config)# interface vlan 100
To remove this VLAN interface and all associated configuration, enter the no interface vlan command.
Because this interface also includes the interface name configuration, and the name is used in other
commands, those commands are also removed.
Step 2
(Optional) For the Base license, allow this interface to be the third VLAN by limiting it from initiating
contact to one other VLAN using the following command:
hostname(config-if)# no forward interface vlan number
Where number specifies the VLAN ID to which this VLAN interface cannot initiate traffic.
With the Base license, you can only configure a third VLAN if you use this command to limit it.
For example, you have one VLAN assigned to the outside for Internet access, one VLAN assigned to an
inside business network, and a third VLAN assigned to your home network. The home network does not
need to access the business network, so you can use the no forward interface command on the home
VLAN; the business network can access the home network, but the home network cannot access the
business network.
If you already have two VLAN interfaces configured with a nameif command, be sure to enter the no
forward interface command before the nameif command on the third interface; the adaptive security
appliance does not allow three fully functioning VLAN interfaces with the Base license on the ASA 5505
adaptive security appliance.
Note
Step 3
If you upgrade to the Security Plus license, you can remove this command and achieve full
functionality for this interface. If you leave this command in place, this interface continues to be
limited even after upgrading.
To name the interface, enter the following command:
hostname(config-if)# nameif name
The name is a text string up to 48 characters, and is not case-sensitive. You can change the name by
reentering this command with a new value. Do not enter the no form, because that command causes all
commands that refer to that name to be deleted.
Step 4
To set the security level, enter the following command:
hostname(config-if)# security-level number
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Where number is an integer between 0 (lowest) and 100 (highest).
Step 5
(Routed mode only) To set the IP address, enter one of the following commands.
Note
To set an IPv6 address, see the “Configuring IPv6 on an Interface” section on page 12-3.
To set the management IP address for transparent firewall mode, see the “Setting the
Management IP Address for a Transparent Firewall” section on page 8-5. In transparent mode,
you do not set the IP address for each interface, but rather for the whole adaptive security
appliance or context.
For failover, you must set the IP address an standby address manually; DHCP and PPPoE are not
supported.
•
To set the IP address manually, enter the following command:
hostname(config-if)# ip address ip_address [mask] [standby ip_address]
The standby keyword and address is used for failover. See Chapter 14, “Configuring Failover,” for
more information.
•
To obtain an IP address from a DHCP server, enter the following command:
hostname(config-if)# ip address dhcp [setroute]
Reenter this command to reset the DHCP lease and request a new lease.
If you do not enable the interface using the no shutdown command before you enter the ip address
dhcp command, some DHCP requests might not be sent.
•
Step 6
To obtain an IP address from a PPPoE server, see Chapter 35, “Configuring the PPPoE Client.”
(Optional) To assign a private MAC address to this interface, enter the following command:
hostname(config-if)# mac-address mac_address [standby mac_address]
By default in routed mode, all VLANs use the same MAC address. In transparent mode, the VLANs use
unique MAC addresses. You might want to set unique VLANs or change the generated VLANs if your
switch requires it, or for access control purposes.
Step 7
(Optional) To set an interface to management-only mode, so that it does not allow through traffic, enter
the following command:
hostname(config-if)# management-only
Step 8
By default, VLAN interfaces are enabled. To enable the interface, if it is not already enabled, enter the
following command:
hostname(config-if)# no shutdown
To disable the interface, enter the shutdown command.
The following example configures seven VLAN interfaces, including the failover interface which is
configured separately using the failover lan command:
hostname(config)# interface vlan 100
hostname(config-if)# nameif outside
hostname(config-if)# security-level 0
hostname(config-if)# ip address 10.1.1.1 255.255.255.0
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hostname(config-if)# no shutdown
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
interface vlan 200
nameif inside
security-level 100
ip address 10.2.1.1 255.255.255.0
no shutdown
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
interface vlan 201
nameif dept1
security-level 90
ip address 10.2.2.1 255.255.255.0
no shutdown
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
interface vlan 202
nameif dept2
security-level 90
ip address 10.2.3.1 255.255.255.0
no shutdown
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
interface vlan 300
nameif dmz
security-level 50
ip address 10.3.1.1 255.255.255.0
no shutdown
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
interface vlan 400
nameif backup-isp
security-level 50
ip address 10.1.2.1 255.255.255.0
no shutdown
hostname(config-if)# failover lan faillink vlan500
hostname(config)# failover interface ip faillink 10.4.1.1 255.255.255.0 standby 10.4.1.2
255.255.255.0
The following example configures three VLAN interfaces for the Base license. The third home interface
cannot forward traffic to the business interface.
hostname(config)# interface vlan 100
hostname(config-if)# nameif outside
hostname(config-if)# security-level 0
hostname(config-if)# ip address dhcp
hostname(config-if)# no shutdown
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
interface vlan 200
nameif business
security-level 100
ip address 10.1.1.1 255.255.255.0
no shutdown
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
interface vlan 300
no forward interface vlan 200
nameif home
security-level 50
ip address 10.2.1.1 255.255.255.0
no shutdown
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Configuring Switch Ports as Access Ports
Configuring Switch Ports as Access Ports
By default, all switch ports are shut down. To assign a switch port to one VLAN, configure it as an access
port. To create a trunk port to carry multiple VLANs, see the “Configuring a Switch Port as a Trunk Port”
section on page 4-11.
By default, the speed and duplex for switch ports are set to auto-negotiate. The default auto-negotiation
setting also includes the Auto-MDI/MDIX feature. Auto-MDI/MDIX eliminates the need for crossover
cabling by performing an internal crossover when a straight cable is detected during the auto-negotiation
phase. Either the speed or duplex must be set to auto-negotiate to enable Auto-MDI/MDIX for the
interface. If you explicitly set both the speed and duplex to a fixed value, thus disabling auto-negotiation
for both settings, then Auto-MDI/MDIX is also disabled.
Caution
The ASA 5505 adaptive security appliance does not support Spanning Tree Protocol for loop detection
in the network. Therefore you must ensure that any connection with the adaptive security appliance does
not end up in a network loop.
To configure a switch port, perform the following steps:
Step 1
To specify the switch port you want to configure, enter the following command:
hostname(config)# interface ethernet0/port
Where port is 0 through 7. For example, enter the following command:
hostname(config)# interface ethernet0/1
Step 2
To assign this switch port to a VLAN, enter the following command:
hostname(config-if)# switchport access vlan number
Where number is the VLAN ID, between 1 and 4090.
Note
Step 3
You might assign multiple switch ports to the primary or backup VLANs if the Internet access device
includes Layer 2 redundancy.
(Optional) To prevent the switch port from communicating with other protected switch ports on the same
VLAN, enter the following command:
hostname(config-if)# switchport protected
You might want to prevent switch ports from communicating with each other if the devices on those
switch ports are primarily accessed from other VLANs, you do not need to allow intra-VLAN access,
and you want to isolate the devices from each other in case of infection or other security breach. For
example, if you have a DMZ that hosts three web servers, you can isolate the web servers from each other
if you apply the switchport protected command to each switch port. The inside and outside networks
can both communicate with all three web servers, and vice versa, but the web servers cannot
communicate with each other.
Step 4
(Optional) To set the speed, enter the following command:
hostname(config-if)# speed {auto | 10 | 100}
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The auto setting is the default. If you set the speed to anything other than auto on PoE ports Ethernet
0/6 or 0/7, then Cisco IP phones and Cisco wireless access points that do not support IEEE 802.3af will
not be detected and supplied with power.
Step 5
(Optional) To set the duplex, enter the following command:
hostname(config-if)# duplex {auto | full | half}
The auto setting is the default. If you set the duplex to anything other than auto on PoE ports Ethernet
0/6 or 0/7, then Cisco IP phones and Cisco wireless access points that do not support IEEE 802.3af will
not be detected and supplied with power.
Step 6
To enable the switch port, if it is not already enabled, enter the following command:
hostname(config-if)# no shutdown
To disable the switch port, enter the shutdown command.
The following example configures five VLAN interfaces, including the failover interface which is
configured using the failover lan command:
hostname(config)# interface vlan 100
hostname(config-if)# nameif outside
hostname(config-if)# security-level 0
hostname(config-if)# ip address 10.1.1.1 255.255.255.0
hostname(config-if)# no shutdown
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
interface vlan 200
nameif inside
security-level 100
ip address 10.2.1.1 255.255.255.0
no shutdown
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
interface vlan 300
nameif dmz
security-level 50
ip address 10.3.1.1 255.255.255.0
no shutdown
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
interface vlan 400
nameif backup-isp
security-level 50
ip address 10.1.2.1 255.255.255.0
no shutdown
hostname(config-if)# failover lan faillink vlan500
hostname(config)# failover interface ip faillink 10.4.1.1 255.255.255.0 standby 10.4.1.2
255.255.255.0
hostname(config)# interface ethernet 0/0
hostname(config-if)# switchport access vlan 100
hostname(config-if)# no shutdown
hostname(config-if)# interface ethernet 0/1
hostname(config-if)# switchport access vlan 200
hostname(config-if)# no shutdown
hostname(config-if)# interface ethernet 0/2
hostname(config-if)# switchport access vlan 300
hostname(config-if)# no shutdown
hostname(config-if)# interface ethernet 0/3
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Configuring a Switch Port as a Trunk Port
hostname(config-if)# switchport access vlan 400
hostname(config-if)# no shutdown
hostname(config-if)# interface ethernet 0/4
hostname(config-if)# switchport access vlan 500
hostname(config-if)# no shutdown
Configuring a Switch Port as a Trunk Port
By default, all switch ports are shut down. This procedure tells how to create a trunk port that can carry
multiple VLANs using 802.1Q tagging. Trunk mode is available only with the Security Plus license.
To create an access port, where an interface is assigned to only one VLAN, see the “Configuring Switch
Ports as Access Ports” section on page 4-9.
By default, the speed and duplex for switch ports are set to auto-negotiate. The default auto-negotiation
setting also includes the Auto-MDI/MDIX feature. Auto-MDI/MDIX eliminates the need for crossover
cabling by performing an internal crossover when a straight cable is detected during the auto-negotiation
phase. Either the speed or duplex must be set to auto-negotiate to enable Auto-MDI/MDIX for the
interface. If you explicitly set both the speed and duplex to a fixed value, thus disabling auto-negotiation
for both settings, then Auto-MDI/MDIX is also disabled.
To configure a trunk port, perform the following steps:
Step 1
To specify the switch port you want to configure, enter the following command:
hostname(config)# interface ethernet0/port
Where port is 0 through 7. For example, enter the following command:
hostname(config)# interface ethernet0/1
Step 2
To assign VLANs to this trunk, enter one or more of the following commands.
•
To assign native VLANs, enter the following command:
hostname(config-if)# switchport trunk native vlan vlan_id
where the vlan_id is a single VLAN ID between 1 and 4090.
Packets on the native VLAN are not modified when sent over the trunk. For example, if a port has
VLANs 2, 3 and 4 assigned to it, and VLAN 2 is the native VLAN, then packets on VLAN 2 that
egress the port are not modified with an 802.1Q header. Frames which ingress (enter) this port and
have no 802.1Q header are put into VLAN 2.
Each port can only have one native VLAN, but every port can have either the same or a different
native VLAN.
•
To assign VLANs, enter the following command:
hostname(config-if)# switchport trunk allowed vlan vlan_range
where the vlan_range (with VLANs between 1 and 4090) can be identified in one of the following
ways:
A single number (n)
A range (n-x)
Separate numbers and ranges by commas, for example:
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5,7-10,13,45-100
You can enter spaces instead of commas, but the command is saved to the configuration with
commas.
You can include the native VLAN in this command, but it is not required; the native VLAN is passed
whether it is included in this command or not.
This switch port cannot pass traffic until you assign at least one VLAN to it, native or non-native.
Step 3
To make this switch port a trunk port, enter the following command:
hostname(config-if)# switchport mode trunk
To restore this port to access mode, enter the switchport mode access command.
Step 4
(Optional) To prevent the switch port from communicating with other protected switch ports on the same
VLAN, enter the following command:
hostname(config-if)# switchport protected
You might want to prevent switch ports from communicating with each other if the devices on those
switch ports are primarily accessed from other VLANs, you do not need to allow intra-VLAN access,
and you want to isolate the devices from each other in case of infection or other security breach. For
example, if you have a DMZ that hosts three web servers, you can isolate the web servers from each other
if you apply the switchport protected command to each switch port. The inside and outside networks
can both communicate with all three web servers, and vice versa, but the web servers cannot
communicate with each other.
Step 5
(Optional) To set the speed, enter the following command:
hostname(config-if)# speed {auto | 10 | 100}
The auto setting is the default.
Step 6
(Optional) To set the duplex, enter the following command:
hostname(config-if)# duplex {auto | full | half}
The auto setting is the default.
Step 7
To enable the switch port, if it is not already enabled, enter the following command:
hostname(config-if)# no shutdown
To disable the switch port, enter the shutdown command.
The following example configures seven VLAN interfaces, including the failover interface which is
configured using the failover lan command. VLANs 200, 201, and 202 are trunked on Ethernet 0/1.
hostname(config)# interface vlan 100
hostname(config-if)# nameif outside
hostname(config-if)# security-level 0
hostname(config-if)# ip address 10.1.1.1 255.255.255.0
hostname(config-if)# no shutdown
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
interface vlan 200
nameif inside
security-level 100
ip address 10.2.1.1 255.255.255.0
no shutdown
hostname(config-if)# interface vlan 201
hostname(config-if)# nameif dept1
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Allowing Communication Between VLAN Interfaces on the Same Security Level
hostname(config-if)# security-level 90
hostname(config-if)# ip address 10.2.2.1 255.255.255.0
hostname(config-if)# no shutdown
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
interface vlan 202
nameif dept2
security-level 90
ip address 10.2.3.1 255.255.255.0
no shutdown
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
interface vlan 300
nameif dmz
security-level 50
ip address 10.3.1.1 255.255.255.0
no shutdown
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
interface vlan 400
nameif backup-isp
security-level 50
ip address 10.1.2.1 255.255.255.0
no shutdown
hostname(config-if)# failover lan faillink vlan500
hostname(config)# failover interface ip faillink 10.4.1.1 255.255.255.0 standby 10.4.1.2
255.255.255.0
hostname(config)# interface ethernet 0/0
hostname(config-if)# switchport access vlan 100
hostname(config-if)# no shutdown
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
interface ethernet 0/1
switchport mode trunk
switchport trunk allowed vlan 200-202
switchport trunk native vlan 5
no shutdown
hostname(config-if)# interface ethernet 0/2
hostname(config-if)# switchport access vlan 300
hostname(config-if)# no shutdown
hostname(config-if)# interface ethernet 0/3
hostname(config-if)# switchport access vlan 400
hostname(config-if)# no shutdown
hostname(config-if)# interface ethernet 0/4
hostname(config-if)# switchport access vlan 500
hostname(config-if)# no shutdown
Allowing Communication Between VLAN Interfaces on the
Same Security Level
By default, interfaces on the same security level cannot communicate with each other. Allowing
communication between same security interfaces lets traffic flow freely between all same security
interfaces without access lists.
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Allowing Communication Between VLAN Interfaces on the Same Security Level
Note
If you enable NAT control, you do not need to configure NAT between same security level interfaces.
See the “NAT and Same Security Level Interfaces” section on page 17-12 for more information on NAT
and same security level interfaces.
If you enable same security interface communication, you can still configure interfaces at different
security levels as usual.
To enable interfaces on the same security level so that they can communicate with each other, enter the
following command:
hostname(config)# same-security-traffic permit inter-interface
To disable this setting, use the no form of this command.
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5
Configuring Ethernet Settings and Subinterfaces
This chapter describes how to configure and enable physical Ethernet interfaces and how to add
subinterfaces. If you have both fiber and copper Ethernet ports (for example, on the 4GE SSM for the
ASA 5510 and higher series adaptive security appliance), this chapter describes how to configure the
inteface media type.
In single context mode, complete the procedures in this chapter and then continue your interface
configuration in Chapter 7, “Configuring Interface Parameters.” In multiple context mode, complete the
procedures in this chapter in the system execution space, then assign interfaces and subinterfaces to
contexts according to Chapter 6, “Adding and Managing Security Contexts,” and finally configure the
interface parameters within each context according to Chapter 7, “Configuring Interface Parameters.”
Note
To configure interfaces for the ASA 5505 adaptive security appliance, see Chapter 4, “Configuring
Switch Ports and VLAN Interfaces for the Cisco ASA 5505 Adaptive Security Appliance.”
This chapter includes the following sections:
•
Configuring and Enabling RJ-45 Interfaces, page 5-1
•
Configuring and Enabling Fiber Interfaces, page 5-2
•
Configuring and Enabling VLAN Subinterfaces and 802.1Q Trunking, page 5-3
Configuring and Enabling RJ-45 Interfaces
This section describes how to configure Ethernet settings for physical interfaces, and how to enable the
interface. By default, all physical interfaces are shut down. You must enable the physical interface before
any traffic can pass through it or through a subinterface. For multiple context mode, if you allocate a
physical interface or subinterface to a context, the interfaces are enabled by default in the context.
However, before traffic can pass through the context interface, you must also enable the interface in the
system configuration according to this procedure.
By default, the speed and duplex for copper (RJ-45) interfaces are set to auto-negotiate.
The ASA 5550 adaptive security appliance and the 4GE SSM for the ASA 5510 and higher adaptive
security appliance includes two connector types: copper RJ-45 and fiber SFP. RJ-45 is the default. If you
want to configure the security appliance to use the fiber SFP connectors, see the “Configuring and
Enabling Fiber Interfaces” section on page 5-2.
For RJ-45 interfaces on the ASA 5500 series adaptive security appliance, the default auto-negotiation
setting also includes the Auto-MDI/MDIX feature. Auto-MDI/MDIX eliminates the need for crossover
cabling by performing an internal crossover when a straight cable is detected during the auto-negotiation
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Configuring Ethernet Settings and Subinterfaces
Configuring and Enabling Fiber Interfaces
phase. Either the speed or duplex must be set to auto-negotiate to enable Auto-MDI/MDIX for the
interface. If you explicitly set both the speed and duplex to a fixed value, thus disabling auto-negotiation
for both settings, then Auto-MDI/MDIX is also disabled.
To enable the interface, or to set a specific speed and duplex, perform the following steps:
Step 1
To specify the interface you want to configure, enter the following command:
hostname(config)# interface physical_interface
The physical_interface ID includes the type, slot, and port number as type[slot/]port.
The physical interface types include the following:
•
ethernet
•
gigabitethernet
For the PIX 500 series security appliance, enter the type followed by the port number, for example,
ethernet0.
For the ASA 5500 series adaptive security appliance, enter the type followed by slot/port, for example,
gigabitethernet0/1. Interfaces that are built into the chassis are assigned to slot 0, while interfaces on
the 4GE SSM are assigned to slot 1.
The ASA 5500 series adaptive security appliance also includes the following type:
•
management
The management interface is a Fast Ethernet interface designed for management traffic only, and is
specified as management0/0. You can, however, use it for through traffic if desired (see the
management-only command). In transparent firewall mode, you can use the management interface
in addition to the two interfaces allowed for through traffic. You can also add subinterfaces to the
management interface to provide management in each security context for multiple context mode.
Step 2
(Optional) To set the speed, enter the following command:
hostname(config-if)# speed {auto | 10 | 100 | 1000 | nonegotiate}
The auto setting is the default. The speed nonegotiate command disables link negotiation.
Step 3
(Optional) To set the duplex, enter the following command:
hostname(config-if)# duplex {auto | full | half}
The auto setting is the default.
Step 4
To enable the interface, enter the following command:
hostname(config-if)# no shutdown
To disable the interface, enter the shutdown command. If you enter the shutdown command for a
physical interface, you also shut down all subinterfaces. If you shut down an interface in the system
execution space, then that interface is shut down in all contexts that share it.
Configuring and Enabling Fiber Interfaces
This section describes how to configure Ethernet settings for physical interfaces, and how to enable the
interface. By default, all physical interfaces are shut down. You must enable the physical interface before
any traffic can pass through it or through a subinterface. For multiple context mode, if you allocate a
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Configuring Ethernet Settings and Subinterfaces
Configuring and Enabling VLAN Subinterfaces and 802.1Q Trunking
physical interface or subinterface to a context, the interfaces are enabled by default in the context.
However, before traffic can pass through the context interface, you must also enable the interface in the
system configuration according to this procedure.
By default, the connectors used on the 4GE SSM or for built-in interfaces in slot 1 on the ASA 5550
adaptive security appliance are the RJ-45 connectors. To use the fiber SFP connectors, you must set the
media type to SFP. The fiber interface has a fixed speed and does not support duplex, but you can set the
interface to negotiate link parameters (the default) or not to negotiate.
To enable the interface, set the media type, or to set negotiation settings, perform the following steps:
Step 1
To specify the interface you want to configure, enter the following command:
hostname(config)# interface gigabitethernet 1/port
The 4GE SSM interfaces are assigned to slot 1, as shown in the interface ID in the syntax (the interfaces
built into the chassis are assigned to slot 0).
Step 2
To set the media type to SFP, enter the following command:
hostname(config-if)# media-type sfp
To restore the defaukt RJ-45, enter the media-type rj45 command.
Step 3
(Optional) To disable link negotiation, enter the following command:
hostname(config-if)# speed nonegotiate
For fiber Gigabit Ethernet interfaces, the default is no speed nonegotiate, which sets the speed to 1000
Mbps and enables link negotiation for flow-control parameters and remote fault information. The speed
nonegotiate command disables link negotiation.
Step 4
To enable the interface, enter the following command:
hostname(config-if)# no shutdown
To disable the interface, enter the shutdown command. If you enter the shutdown command for a
physical interface, you also shut down all subinterfaces. If you shut down an interface in the system
execution space, then that interface is shut down in all contexts that share it.
Configuring and Enabling VLAN Subinterfaces and 802.1Q
Trunking
This section describes how to configure and enable a VLAN subinterface. An interface with one or more
VLAN subinterfaces is automatically configured as an 802.1Q trunk.
You must enable the physical interface before any traffic can pass through an enabled subinterface (see
the “Configuring and Enabling RJ-45 Interfaces” section on page 5-1 or the “Configuring and Enabling
Fiber Interfaces” section on page 5-2). For multiple context mode, if you allocate a subinterface to a
context, the interfaces are enabled by default in the context. However, before traffic can pass through the
context interface, you must also enable the interface in the system configuration with this procedure.
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Configuring Ethernet Settings and Subinterfaces
Configuring and Enabling VLAN Subinterfaces and 802.1Q Trunking
Subinterfaces let you divide a physical interface into multiple logical interfaces that are tagged with
different VLAN IDs. Because VLANs allow you to keep traffic separate on a given physical interface,
you can increase the number of interfaces available to your network without adding additional physical
interfaces or security appliances. This feature is particularly useful in multiple context mode so you can
assign unique interfaces to each context.
To determine how many subinterfaces are allowed for your platform, see Appendix A, “Feature Licenses
and Specifications.”
Note
If you use subinterfaces, you typically do not also want the physical interface to pass traffic, because the
physical interface passes untagged packets. Because the physical interface must be enabled for the
subinterface to pass traffic, ensure that the physical interface does not pass traffic by leaving out the
nameif command. If you want to let the physical interface pass untagged packets, you can configure the
nameif command as usual. See the “Configuring Interface Parameters” section on page 7-1 for more
information about completing the interface configuration.
To add a subinterface and assign a VLAN to it, perform the following steps:
Step 1
To specify the new subinterface, enter the following command:
hostname(config)# interface physical_interface.subinterface
See the “Configuring and Enabling RJ-45 Interfaces” section for a description of the physical interface
ID.
The subinterface ID is an integer between 1 and 4294967293.
For example, enter the following command:
hostname(config)# interface gigabitethernet0/1.100
Step 2
To specify the VLAN for the subinterface, enter the following command:
hostname(config-subif)# vlan vlan_id
The vlan_id is an integer between 1 and 4094. Some VLAN IDs might be reserved on connected
switches, so check the switch documentation for more information.
You can only assign a single VLAN to a subinterface, and not to the physical interface. Each subinterface
must have a VLAN ID before it can pass traffic. To change a VLAN ID, you do not need to remove the
old VLAN ID with the no option; you can enter the vlan command with a different VLAN ID, and the
security appliance changes the old ID.
Step 3
To enable the subinterface, enter the following command:
hostname(config-subif)# no shutdown
To disable the interface, enter the shutdown command. If you shut down an interface in the system
execution space, then that interface is shut down in all contexts that share it.
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6
Adding and Managing Security Contexts
This chapter describes how to configure multiple security contexts on the security appliance, and
includes the following sections:
•
Configuring Resource Management, page 6-1
•
Configuring a Security Context, page 6-7
•
Automatically Assigning MAC Addresses to Context Interfaces, page 6-11
•
Changing Between Contexts and the System Execution Space, page 6-11
•
Managing Security Contexts, page 6-12
For information about how contexts work and how to enable multiple context mode, see Chapter 3,
“Enabling Multiple Context Mode.”
Configuring Resource Management
By default, all security contexts have unlimited access to the resources of the security appliance, except
where maximum limits per context are enforced. However, if you find that one or more contexts use too
many resources, and they cause other contexts to be denied connections, for example, then you can
configure resource management to limit the use of resources per context.
This section includes the following topics:
•
Classes and Class Members Overview, page 6-1
•
Configuring a Class, page 6-4
Classes and Class Members Overview
The security appliance manages resources by assigning contexts to resource classes. Each context uses
the resource limits set by the class. This section includes the following topics:
•
Resource Limits, page 6-2
•
Default Class, page 6-3
•
Class Members, page 6-4
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Configuring Resource Management
Resource Limits
When you create a class, the security appliance does not set aside a portion of the resources for each
context assigned to the class; rather, the security appliance sets the maximum limit for a context. If you
oversubscribe resources, or allow some resources to be unlimited, a few contexts can “use up” those
resources, potentially affecting service to other contexts.
You can set the limit for individual resources, as a percentage (if there is a hard system limit) or as an
absolute value.
You can oversubscribe the security appliance by assigning more than 100 percent of a resource across
all contexts. For example, you can set the Bronze class to limit connections to 20 percent per context,
and then assign 10 contexts to the class for a total of 200 percent. If contexts concurrently use more than
the system limit, then each context gets less than the 20 percent you intended. (See Figure 6-1.)
Figure 6-1
Resource Oversubscription
Total Number of System Connections = 999,900
Max. 20%
(199,800)
Maximum connections
allowed.
16%
(159,984)
Connections in use.
12%
(119,988)
4%
(39,996)
1
2
3
4
5
6
Contexts in Class
7
8
9
10
104895
Connections denied
because system limit
was reached.
8%
(79,992)
If you assign an absolute value to a resource across all contexts that exceeds the practical limit of the
security appliance, then the performance of the security appliance might be impaired.
The security appliance lets you assign unlimited access to one or more resources in a class, instead of a
percentage or absolute number. When a resource is unlimited, contexts can use as much of the resource
as the system has available or that is practically available. For example, Context A, B, and C are in the
Silver Class, which limits each class member to 1 percent of the connections, for a total of 3 percent; but
the three contexts are currently only using 2 percent combined. Gold Class has unlimited access to
connections. The contexts in the Gold Class can use more than the 97 percent of “unassigned”
connections; they can also use the 1 percent of connections not currently in use by Context A, B, and C,
even if that means that Context A, B, and C are unable to reach their 3 percent combined limit. (See
Figure 6-2.) Setting unlimited access is similar to oversubscribing the security appliance, except that you
have less control over how much you oversubscribe the system.
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Figure 6-2
Unlimited Resources
50% 43%
5%
Maximum connections
allowed.
4%
Connections in use.
3%
Connections denied
because system limit
was reached.
2%
A
B
C
Contexts Silver Class
1
2
3
Contexts Gold Class
153211
1%
Default Class
All contexts belong to the default class if they are not assigned to another class; you do not have to
actively assign a context to the default class.
If a context belongs to a class other than the default class, those class settings always override the default
class settings. However, if the other class has any settings that are not defined, then the member context
uses the default class for those limits. For example, if you create a class with a 2 percent limit for all
concurrent connections, but no other limits, then all other limits are inherited from the default class.
Conversely, if you create a class with a limit for all resources, the class uses no settings from the default
class.
By default, the default class provides unlimited access to resources for all contexts, except for the
following limits, which are by default set to the maximum allowed per context:
•
Telnet sessions—5 sessions.
•
SSH sessions—5 sessions.
•
IPSec sessions—5 sessions.
•
MAC addresses—65,535 entries.
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Figure 6-3 shows the relationship between the default class and other classes. Contexts A and C belong
to classes with some limits set; other limits are inherited from the default class. Context B inherits no
limits from default because all limits are set in its class, the Gold class. Context D was not assigned to
a class, and is by default a member of the default class.
Figure 6-3
Class
Bronze
(Some
Limits
Set)
Context A
Resource Classes
Default Class
Context D
Class Silver
(Some Limits
Set)
Class Gold
(All Limits
Set)
Context B
104689
Context C
Class Members
To use the settings of a class, assign the context to the class when you define the context. All contexts
belong to the default class if they are not assigned to another class; you do not have to actively assign a
context to default. You can only assign a context to one resource class. The exception to this rule is that
limits that are undefined in the member class are inherited from the default class; so in effect, a context
could be a member of default plus another class.
Configuring a Class
To configure a class in the system configuration, perform the following steps. You can change the value
of a particular resource limit by reentering the command with a new value.
Step 1
To specify the class name and enter the class configuration mode, enter the following command in the
system execution space:
hostname(config)# class name
The name is a string up to 20 characters long. To set the limits for the default class, enter default for the
name.
Step 2
To set the resource limits, see the following options:
•
To set all resource limits (shown in Table 6-1) to be unlimited, enter the following command:
hostname(config-resmgmt)# limit-resource all 0
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For example, you might want to create a class that includes the admin context that has no limitations.
The default class has all resources set to unlimited by default.
•
To set a particular resource limit, enter the following command:
hostname(config-resmgmt)# limit-resource [rate] resource_name number[%]
For this particular resource, the limit overrides the limit set for all. Enter the rate argument to set
the rate per second for certain resources. For resources that do not have a system limit, you cannot
set the percentage (%) between 1 and 100; you can only set an absolute value. See Table 6-1 for
resources for which you can set the rate per second and which to not have a system limit.
Table 6-1 lists the resource types and the limits. See also the show resource types command.
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Table 6-1
Resource Names and Limits
Rate or
Resource Name Concurrent
Minimum and
Maximum Number
per Context
System Limit1
Description
mac-addresses Concurrent
N/A
65,535
For transparent firewall mode, the number of
MAC addresses allowed in the MAC address
table.
conns
N/A
Concurrent connections: TCP or UDP connections between any two
hosts, including connections between one
See the “Supported
host and multiple other hosts.
Platforms and Feature
Licenses” section on
page A-1 for the
connection limit for your
platform.
Concurrent
or Rate
Rate: N/A
inspects
Rate
N/A
N/A
Application inspections.
hosts
Concurrent
N/A
N/A
Hosts that can connect through the security
appliance.
asdm
Concurrent
1 minimum
32
ASDM management sessions.
5 maximum
ssh
Concurrent
1 minimum
Note
ASDM sessions use two HTTPS
connections: one for monitoring that
is always present, and one for making
configuration changes that is present
only when you make changes. For
example, the system limit of 32
ASDM sessions represents a limit of
64 HTTPS sessions.
100
SSH sessions.
5 maximum
syslogs
Rate
N/A
N/A
System log messages.
telnet
Concurrent
1 minimum
100
Telnet sessions.
N/A
Address translations.
5 maximum
xlates
Concurrent
N/A
1. If this column value is N/A, then you cannot set a percentage of the resource because there is no hard system limit for the resource.
For example, to set the default class limit for conns to 10 percent instead of unlimited, enter the
following commands:
hostname(config)# class default
hostname(config-class)# limit-resource conns 10%
All other resources remain at unlimited.
To add a class called gold, enter the following commands:
hostname(config)# class gold
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hostname(config-class)#
hostname(config-class)#
hostname(config-class)#
hostname(config-class)#
hostname(config-class)#
hostname(config-class)#
hostname(config-class)#
hostname(config-class)#
hostname(config-class)#
hostname(config-class)#
limit-resource
limit-resource
limit-resource
limit-resource
limit-resource
limit-resource
limit-resource
limit-resource
limit-resource
limit-resource
mac-addresses 10000
conns 15%
rate conns 1000
rate inspects 500
hosts 9000
asdm 5
ssh 5
rate syslogs 5000
telnet 5
xlates 36000
Configuring a Security Context
The security context definition in the system configuration identifies the context name, configuration file
URL, and interfaces that a context can use.
Note
If you do not have an admin context (for example, if you clear the configuration) then you must first
specify the admin context name by entering the following command:
hostname(config)# admin-context name
Although this context name does not exist yet in your configuration, you can subsequently enter the
context name command to match the specified name to continue the admin context configuration.
To add or change a context in the system configuration, perform the following steps:
Step 1
To add or modify a context, enter the following command in the system execution space:
hostname(config)# context name
The name is a string up to 32 characters long. This name is case sensitive, so you can have two contexts
named “customerA” and “CustomerA,” for example. You can use letters, digits, or hyphens, but you
cannot start or end the name with a hyphen.
“System” or “Null” (in upper or lower case letters) are reserved names, and cannot be used.
Step 2
(Optional) To add a description for this context, enter the following command:
hostname(config-ctx)# description text
Step 3
To specify the interfaces you can use in the context, enter the command appropriate for a physical
interface or for one or more subinterfaces.
•
To allocate a physical interface, enter the following command:
hostname(config-ctx)# allocate-interface physical_interface [map_name]
[visible | invisible]
•
To allocate one or more subinterfaces, enter the following command:
hostname(config-ctx)# allocate-interface
physical_interface.subinterface[-physical_interface.subinterface]
[map_name[-map_name]] [visible | invisible]
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You can enter these commands multiple times to specify different ranges. If you remove an allocation
with the no form of this command, then any context commands that include this interface are removed
from the running configuration.
Transparent firewall mode allows only two interfaces to pass through traffic; however, on the ASA
adaptive security appliance, you can use the dedicated management interface, Management 0/0, (either
the physical interface or a subinterface) as a third interface for management traffic.
Note
The management interface for transparent mode does not flood a packet out the interface when that
packet is not in the MAC address table.
You can assign the same interfaces to multiple contexts in routed mode, if desired. Transparent mode
does not allow shared interfaces.
The map_name is an alphanumeric alias for the interface that can be used within the context instead of
the interface ID. If you do not specify a mapped name, the interface ID is used within the context. For
security purposes, you might not want the context administrator to know which interfaces are being used
by the context.
A mapped name must start with a letter, end with a letter or digit, and have as interior characters only
letters, digits, or an underscore. For example, you can use the following names:
int0
inta
int_0
For subinterfaces, you can specify a range of mapped names.
If you specify a range of subinterfaces, you can specify a matching range of mapped names. Follow these
guidelines for ranges:
•
The mapped name must consist of an alphabetic portion followed by a numeric portion. The
alphabetic portion of the mapped name must match for both ends of the range. For example, enter
the following range:
int0-int10
If you enter gigabitethernet0/1.1-gigabitethernet0/1.5 happy1-sad5, for example, the command
fails.
•
The numeric portion of the mapped name must include the same quantity of numbers as the
subinterface range. For example, both ranges include 100 interfaces:
gigabitethernet0/0.100-gigabitethernet0/0.199 int1-int100
If you enter gigabitethernet0/0.100-gigabitethernet0/0.199 int1-int15, for example, the command
fails.
Specify visible to see physical interface properties in the show interface command even if you set a
mapped name. The default invisible keyword specifies to only show the mapped name.
The following example shows gigabitethernet0/1.100, gigabitethernet0/1.200, and
gigabitethernet0/2.300 through gigabitethernet0/1.305 assigned to the context. The mapped names are
int1 through int8.
hostname(config-ctx)# allocate-interface gigabitethernet0/1.100 int1
hostname(config-ctx)# allocate-interface gigabitethernet0/1.200 int2
hostname(config-ctx)# allocate-interface gigabitethernet0/2.300-gigabitethernet0/2.305
int3-int8
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Configuring a Security Context
Step 4
To identify the URL from which the system downloads the context configuration, enter the following
command:
hostname(config-ctx)# config-url url
When you add a context URL, the system immediately loads the context so that it is running, if the
configuration is available.
Note
Enter the allocate-interface command(s) before you enter the config-url command. The security
appliance must assign interfaces to the context before it loads the context configuration; the context
configuration might include commands that refer to interfaces (interface, nat, global...). If you enter the
config-url command first, the security appliance loads the context configuration immediately. If the
context contains any commands that refer to interfaces, those commands fail.
See the following URL syntax:
•
disk:/[path/]filename
This URL indicates the internal Flash memory. The filename does not require a file extension,
although we recommend using “.cfg”. If the configuration file is not available, you see the following
message:
WARNING: Could not fetch the URL disk:/url
INFO: Creating context with default config
You can then change to the context, configure it at the CLI, and enter the write memory command
to write the file to Flash memory.
Note
•
The admin context file must be stored on the internal Flash memory.
ftp://[user[:password]@]server[:port]/[path/]filename[;type=xx]
The type can be one of the following keywords:
– ap—ASCII passive mode
– an—ASCII normal mode
– ip—(Default) Binary passive mode
– in—Binary normal mode
The server must be accessible from the admin context. The filename does not require a file
extension, although we recommend using “.cfg”. If the configuration file is not available, you see
the following message:
WARNING: Could not fetch the URL ftp://url
INFO: Creating context with default config
You can then change to the context, configure it at the CLI, and enter the write memory command
to write the file to the FTP server.
•
http[s]://[user[:password]@]server[:port]/[path/]filename
The server must be accessible from the admin context. The filename does not require a file
extension, although we recommend using “.cfg”. If the configuration file is not available, you see
the following message:
WARNING: Could not fetch the URL http://url
INFO: Creating context with default config
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If you change to the context and configure the context at the CLI, you cannot save changes back to
HTTP or HTTPS servers using the write memory command. You can, however, use the copy tftp
command to copy the running configuration to a TFTP server.
•
tftp://[user[:password]@]server[:port]/[path/]filename[;int=interface_name]
The server must be accessible from the admin context. Specify the interface name if you want to
override the route to the server address. The filename does not require a file extension, although we
recommend using “.cfg”. If the configuration file is not available, you see the following message:
WARNING: Could not fetch the URL tftp://url
INFO: Creating context with default config
You can then change to the context, configure it at the CLI, and enter the write memory command
to write the file to the TFTP server.
To change the URL, reenter the config-url command with a new URL.
See the “Changing the Security Context URL” section on page 6-13 for more information about
changing the URL.
For example, enter the following command:
hostname(config-ctx)# config-url ftp://joe:[email protected]/configlets/test.cfg
Step 5
(Optional) To assign the context to a resource class, enter the following command:
hostname(config-ctx)# member class_name
If you do not specify a class, the context belongs to the default class. You can only assign a context to
one resource class.
For example, to assign the context to the gold class, enter the following command:
hostname(config-ctx)# member gold
Step 6
To view context information, see the show context command in the Cisco Security Appliance Command
Reference.
The following example sets the admin context to be “administrator,” creates a context called
“administrator” on the internal Flash memory, and then adds two contexts from an FTP server:
hostname(config)# admin-context administrator
hostname(config)# context administrator
hostname(config-ctx)# allocate-interface gigabitethernet0/0.1
hostname(config-ctx)# allocate-interface gigabitethernet0/1.1
hostname(config-ctx)# config-url flash:/admin.cfg
hostname(config-ctx)#
hostname(config-ctx)#
hostname(config-ctx)#
hostname(config-ctx)#
int3-int8
hostname(config-ctx)#
hostname(config-ctx)#
context test
allocate-interface gigabitethernet0/0.100 int1
allocate-interface gigabitethernet0/0.102 int2
allocate-interface gigabitethernet0/0.110-gigabitethernet0/0.115
hostname(config-ctx)#
hostname(config-ctx)#
hostname(config-ctx)#
hostname(config-ctx)#
int3-int8
context sample
allocate-interface gigabitethernet0/1.200 int1
allocate-interface gigabitethernet0/1.212 int2
allocate-interface gigabitethernet0/1.230-gigabitethernet0/1.235
config-url ftp://user1:[email protected]/configlets/test.cfg
member gold
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Automatically Assigning MAC Addresses to Context Interfaces
hostname(config-ctx)# config-url ftp://user1:[email protected]/configlets/sample.cfg
hostname(config-ctx)# member silver
Automatically Assigning MAC Addresses to Context Interfaces
To allow contexts to share interfaces, we suggest that you assign unique MAC addresses to each context
interface. The MAC address is used to classify packets within a context. If you share an interface, but do
not have unique MAC addresses for the interface in each context, then the destination IP address is used
to classify packets. The destination address is matched with the context NAT configuration, and this
method has some limitations compared to the MAC address method. See the “How the Security
Appliance Classifies Packets” section on page 3-3 for information about classifying packets.
By default, the physical interface uses the burned-in MAC address, and all subinterfaces of a physical
interface use the same burned-in MAC address.
You can automatically assign private MAC addresses to each shared context interface by entering the
following command in the system configuration:
hostname(config)# mac-address auto
For use with failover, the security appliance generates both an active and standby MAC address for each
interface. If the active unit fails over and the standby unit becomes active, the new active unit starts using
the active MAC addresses to minimize network disruption.
When you assign an interface to a context, the new MAC address is generated immediately. If you enable
this command after you create context interfaces, then MAC addresses are generated for all interfaces
immediately after you enter the command. If you use the no mac-address auto command, the MAC
address for each interface reverts to the default MAC address. For example, subinterfaces of
GigabitEthernet 0/1 revert to using the MAC address of GigabitEthernet 0/1.
The MAC address is generated using the following format:
•
Active unit MAC address: 12_slot.port_subid.contextid.
•
Standby unit MAC address: 02_slot.port_subid.contextid.
For platforms with no interface slots, the slot is always 0. The port is the interface port. The subid is an
internal ID for the subinterface, which is not viewable. The contextid is an internal ID for the context,
viewable with the show context detail command. For example, the interface GigabitEthernet 0/1.200 in
the context with the ID 1 has the following generated MAC addresses, where the internal ID for
subinterface 200 is 31:
•
Active: 1200.0131.0001
•
Standby: 0200.0131.0001
In the rare circumstance that the generated MAC address conflicts with another private MAC address in
your network, you can manually set the MAC address for the interface within the context. See the
“Configuring the Interface” section on page 7-2 to manually set the MAC address.
Changing Between Contexts and the System Execution Space
If you log in to the system execution space (or the admin context using Telnet or SSH), you can change
between contexts and perform configuration and monitoring tasks within each context. The running
configuration that you edit in a configuration mode, or that is used in the copy or write commands,
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Managing Security Contexts
depends on your location. When you are in the system execution space, the running configuration
consists only of the system configuration; when you are in a context, the running configuration consists
only of that context. For example, you cannot view all running configurations (system plus all contexts)
by entering the show running-config command. Only the current configuration displays.
To change between the system execution space and a context, or between contexts, see the following
commands:
•
To change to a context, enter the following command:
hostname# changeto context name
The prompt changes to the following:
hostname/name#
•
To change to the system execution space, enter the following command:
hostname/admin# changeto system
The prompt changes to the following:
hostname#
Managing Security Contexts
This section describes how to manage security contexts, and includes the following topics:
•
Removing a Security Context, page 6-12
•
Changing the Admin Context, page 6-13
•
Changing the Security Context URL, page 6-13
•
Reloading a Security Context, page 6-14
•
Monitoring Security Contexts, page 6-15
Removing a Security Context
You can only remove a context by editing the system configuration. You cannot remove the current
admin context, unless you remove all contexts using the clear context command.
Note
If you use failover, there is a delay between when you remove the context on the active unit and when
the context is removed on the standby unit. You might see an error message indicating that the number
of interfaces on the active and standby units are not consistent; this error is temporary and can be
ignored.
Use the following commands for removing contexts:
•
To remove a single context, enter the following command in the system execution space:
hostname(config)# no context name
All context commands are also removed.
•
To remove all contexts (including the admin context), enter the following command in the system
execution space:
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hostname(config)# clear context
Changing the Admin Context
The system configuration does not include any network interfaces or network settings for itself; rather,
when the system needs to access network resources (such as downloading the contexts from the server),
it uses one of the contexts that is designated as the admin context.
The admin context is just like any other context, except that when a user logs in to the admin context,
then that user has system administrator rights and can access the system and all other contexts. The
admin context is not restricted in any way, and can be used as a regular context. However, because
logging into the admin context grants you administrator privileges over all contexts, you might need to
restrict access to the admin context to appropriate users.
You can set any context to be the admin context, as long as the configuration file is stored in the internal
Flash memory. To set the admin context, enter the following command in the system execution space:
hostname(config)# admin-context context_name
Any remote management sessions, such as Telnet, SSH, or HTTPS, that are connected to the admin
context are terminated. You must reconnect to the new admin context.
Note
A few system commands, including ntp server, identify an interface name that belongs to the admin
context. If you change the admin context, and that interface name does not exist in the new admin
context, be sure to update any system commands that refer to the interface.
Changing the Security Context URL
You cannot change the security context URL without reloading the configuration from the new URL.
The security appliance merges the new configuration with the current running configuration. Reentering
the same URL also merges the saved configuration with the running configuration. A merge adds any
new commands from the new configuration to the running configuration. If the configurations are the
same, no changes occur. If commands conflict or if commands affect the running of the context, then the
effect of the merge depends on the command. You might get errors, or you might have unexpected
results. If the running configuration is blank (for example, if the server was unavailable and the
configuration was never downloaded), then the new configuration is used. If you do not want to merge
the configurations, you can clear the running configuration, which disrupts any communications through
the context, and then reload the configuration from the new URL.
To change the URL for a context, perform the following steps:
Step 1
If you do not want to merge the configuration, change to the context and clear its configuration by
entering the following commands. If you want to perform a merge, skip to Step 2.
hostname# changeto context name
hostname/name# configure terminal
hostname/name(config)# clear configure all
Step 2
If required, change to the system execution space by entering the following command:
hostname/name(config)# changeto system
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Step 3
To enter the context configuration mode for the context you want to change, enter the following
command:
hostname(config)# context name
Step 4
To enter the new URL, enter the following command:
hostname(config)# config-url new_url
The system immediately loads the context so that it is running.
Reloading a Security Context
You can reload the context in two ways:
•
Clear the running configuration and then import the startup configuration.
This action clears most attributes associated with the context, such as connections and NAT tables.
•
Remove the context from the system configuration.
This action clears additional attributes, such as memory allocation, which might be useful for
troubleshooting. However, to add the context back to the system requires you to respecify the URL
and interfaces.
This section includes the following topics:
•
Reloading by Clearing the Configuration, page 6-14
•
Reloading by Removing and Re-adding the Context, page 6-15
Reloading by Clearing the Configuration
To reload the context by clearing the context configuration, and reloading the configuration from the
URL, perform the following steps:
Step 1
To change to the context that you want to reload, enter the following command:
hostname# changeto context name
Step 2
To access configuration mode, enter the following command:
hostname/name# configure terminal
Step 3
To clear the running configuration, enter the following command:
hostname/name(config)# clear configure all
This command clears all connections.
Step 4
To reload the configuration, enter the following command:
hostname/name(config)# copy startup-config running-config
The security appliance copies the configuration from the URL specified in the system configuration. You
cannot change the URL from within a context.
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Reloading by Removing and Re-adding the Context
To reload the context by removing the context and then re-adding it, perform the steps in the following
sections:
1.
“Automatically Assigning MAC Addresses to Context Interfaces” section on page 6-11
2.
“Configuring a Security Context” section on page 6-7
Monitoring Security Contexts
This section describes how to view and monitor context information, and includes the following topics:
•
Viewing Context Information, page 6-15
•
Viewing Resource Allocation, page 6-16
•
Viewing Resource Usage, page 6-19
•
Monitoring SYN Attacks in Contexts, page 6-20
Viewing Context Information
From the system execution space, you can view a list of contexts including the name, allocated
interfaces, and configuration file URL.
From the system execution space, view all contexts by entering the following command:
hostname# show context [name | detail| count]
The detail option shows additional information. See the following sample displays below for more
information.
If you want to show information for a particular context, specify the name.
The count option shows the total number of contexts.
The following is sample output from the show context command. The following sample display shows
three contexts:
hostname# show context
Context Name
*admin
Interfaces
GigabitEthernet0/1.100
GigabitEthernet0/1.101
contexta
GigabitEthernet0/1.200
GigabitEthernet0/1.201
contextb
GigabitEthernet0/1.300
GigabitEthernet0/1.301
Total active Security Contexts: 3
URL
disk0:/admin.cfg
disk0:/contexta.cfg
disk0:/contextb.cfg
Table 6-2 shows each field description.
Table 6-2
show context Fields
Field
Description
Context Name
Lists all context names. The context name with the asterisk (*) is the admin context.
Interfaces
The interfaces assigned to the context.
URL
The URL from which the security appliance loads the context configuration.
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The following is sample output from the show context detail command:
hostname# show context detail
Context "admin", has been created, but initial ACL rules not complete
Config URL: disk0:/admin.cfg
Real Interfaces: Management0/0
Mapped Interfaces: Management0/0
Flags: 0x00000013, ID: 1
Context "ctx", has been created, but initial ACL rules not complete
Config URL: ctx.cfg
Real Interfaces: GigabitEthernet0/0.10, GigabitEthernet0/1.20,
GigabitEthernet0/2.30
Mapped Interfaces: int1, int2, int3
Flags: 0x00000011, ID: 2
Context "system", is a system resource
Config URL: startup-config
Real Interfaces:
Mapped Interfaces: Control0/0, GigabitEthernet0/0,
GigabitEthernet0/0.10, GigabitEthernet0/1, GigabitEthernet0/1.10,
GigabitEthernet0/1.20, GigabitEthernet0/2, GigabitEthernet0/2.30,
GigabitEthernet0/3, Management0/0, Management0/0.1
Flags: 0x00000019, ID: 257
Context "null", is a system resource
Config URL: ... null ...
Real Interfaces:
Mapped Interfaces:
Flags: 0x00000009, ID: 258
See the Cisco Security Appliance Command Reference for more information about the detail output.
The following is sample output from the show context count command:
hostname# show context count
Total active contexts: 2
Viewing Resource Allocation
From the system execution space, you can view the allocation for each resource across all classes and
class members.
To view the resource allocation, enter the following command:
hostname# show resource allocation [detail]
This command shows the resource allocation, but does not show the actual resources being used. See the
“Viewing Resource Usage” section on page 6-19 for more information about actual resource usage.
The detail argument shows additional information. See the following sample displays for more
information.
The following sample display shows the total allocation of each resource as an absolute value and as a
percentage of the available system resources:
hostname# show resource allocation
Resource
Total
Conns [rate]
35000
Inspects [rate]
35000
Syslogs [rate]
10500
Conns
305000
Hosts
78842
% of Avail
N/A
N/A
N/A
30.50%
N/A
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SSH
Telnet
Xlates
All
35
35
91749
unlimited
35.00%
35.00%
N/A
Table 6-3 shows each field description.
Table 6-3
show resource allocation Fields
Field
Description
Resource
The name of the resource that you can limit.
Total
The total amount of the resource that is allocated across all contexts. The amount
is an absolute number of concurrent instances or instances per second. If you
specified a percentage in the class definition, the security appliance converts the
percentage to an absolute number for this display.
% of Avail
The percentage of the total system resources that is allocated across all contexts, if
the resource has a hard system limit. If a resource does not have a system limit, this
column shows N/A.
The following is sample output from the show resource allocation detail command:
hostname# show resource allocation detail
Resource Origin:
A
Value was derived from the resource 'all'
C
Value set in the definition of this class
D
Value set in default class
Resource
Class
Mmbrs Origin
Limit
Conns [rate]
default
all
CA unlimited
gold
1
C
34000
silver
1
CA
17000
bronze
0
CA
8500
All Contexts:
3
Inspects [rate]
Syslogs [rate]
Conns
Hosts
SSH
default
gold
silver
bronze
All Contexts:
all
1
1
0
3
CA
DA
CA
CA
default
gold
silver
bronze
All Contexts:
all
1
1
0
3
CA
C
CA
CA
default
gold
silver
bronze
All Contexts:
all
1
1
0
3
CA
C
CA
CA
default
gold
silver
bronze
All Contexts:
all
1
1
0
3
CA
DA
CA
CA
default
gold
all
1
C
D
unlimited
unlimited
10000
5000
unlimited
6000
3000
1500
unlimited
200000
100000
50000
unlimited
unlimited
26214
13107
5
5
Total
Total %
34000
17000
N/A
N/A
51000
N/A
10000
N/A
10000
N/A
6000
3000
N/A
N/A
9000
N/A
200000
100000
20.00%
10.00%
300000
30.00%
26214
N/A
26214
N/A
5
5.00%
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Telnet
Xlates
mac-addresses
silver
bronze
All Contexts:
1
0
3
CA
CA
default
gold
silver
bronze
All Contexts:
all
1
1
0
3
C
D
CA
CA
default
gold
silver
bronze
All Contexts:
all
1
1
0
3
CA
DA
CA
CA
default
gold
silver
bronze
All Contexts:
all
1
1
0
3
C
D
CA
CA
10
5
5
5
10
5
unlimited
unlimited
23040
11520
65535
65535
6553
3276
10
10.00%
20
20.00%
5
10
5.00%
10.00%
20
20.00%
23040
N/A
23040
N/A
65535
6553
100.00%
9.99%
137623
209.99%
Table 6-4 shows each field description.
Table 6-4
show resource allocation detail Fields
Field
Description
Resource
The name of the resource that you can limit.
Class
The name of each class, including the default class.
The All contexts field shows the total values across all classes.
Mmbrs
The number of contexts assigned to each class.
Origin
The origin of the resource limit, as follows:
•
A—You set this limit with the all option, instead of as an individual resource.
•
C—This limit is derived from the member class.
•
D—This limit was not defined in the member class, but was derived from the
default class. For a context assigned to the default class, the value will be “C”
instead of “D.”
The security appliance can combine “A” with “C” or “D.”
Limit
The limit of the resource per context, as an absolute number. If you specified a
percentage in the class definition, the security appliance converts the percentage to
an absolute number for this display.
Total
The total amount of the resource that is allocated across all contexts in the class.
The amount is an absolute number of concurrent instances or instances per second.
If the resource is unlimited, this display is blank.
% of Avail
The percentage of the total system resources that is allocated across all contexts in
the class. If the resource is unlimited, this display is blank. If the resource does not
have a system limit, then this column shows N/A.
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Viewing Resource Usage
From the system execution space, you can view the resource usage for each context and display the
system resource usage.
From the system execution space, view the resource usage for each context by entering the following
command:
hostname# show resource usage [context context_name | top n | all | summary | system]
[resource {resource_name | all} | detail] [counter counter_name [count_threshold]]
By default, all context usage is displayed; each context is listed separately.
Enter the top n keyword to show the contexts that are the top n users of the specified resource. You must
specify a single resource type, and not resource all, with this option.
The summary option shows all context usage combined.
The system option shows all context usage combined, but shows the system limits for resources instead
of the combined context limits.
For the resource resource_name, see Table 6-1 for available resource names. See also the show resource
type command. Specify all (the default) for all types.
The detail option shows the resource usage of all resources, including those you cannot manage. For
example, you can view the number of TCP intercepts.
The counter counter_name is one of the following keywords:
•
current—Shows the active concurrent instances or the current rate of the resource.
•
denied—Shows the number of instances that were denied because they exceeded the resource limit
shown in the Limit column.
•
peak—Shows the peak concurrent instances, or the peak rate of the resource since the statistics were
last cleared, either using the clear resource usage command or because the device rebooted.
•
all—(Default) Shows all statistics.
The count_threshold sets the number above which resources are shown. The default is 1. If the usage of
the resource is below the number you set, then the resource is not shown. If you specify all for the
counter name, then the count_threshold applies to the current usage.
Note
To show all resources, set the count_threshold to 0.
The following is sample output from the show resource usage context command, which shows the
resource usage for the admin context:
hostname# show resource usage context admin
Resource
Telnet
Conns
Hosts
Current
1
44
45
Peak
1
55
56
Limit
5
N/A
N/A
Denied
0
0
0
Context
admin
admin
admin
The following is sample output from the show resource usage summary command, which shows the
resource usage for all contexts and all resources. This sample shows the limits for 6 contexts.
hostname# show resource usage summary
Resource
Syslogs [rate]
Conns
Current
1743
584
Peak
2132
763
Limit
Denied Context
N/A
0 Summary
280000(S)
0 Summary
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Xlates
8526
8966
N/A
0
Hosts
254
254
N/A
0
Conns [rate]
270
535
N/A
1704
Inspects [rate]
270
535
N/A
0
S = System: Combined context limits exceed the system limit; the
Summary
Summary
Summary
Summary
system limit is shown.
The following is sample output from the show resource usage summary command, which shows the
limits for 25 contexts. Because the context limit for Telnet and SSH connections is 5 per context, then
the combined limit is 125. The system limit is only 100, so the system limit is shown.
hostname# show resource usage summary
Resource
Current
Peak
Limit
Denied
Context
Telnet
1
1
100[S]
0
Summary
SSH
2
2
100[S]
0
Summary
Conns
56
90
N/A
0
Summary
Hosts
89
102
N/A
0
Summary
S = System: Combined context limits exceed the system limit; the system limit is shown.
The following is sample output from the show resource usage system command, which shows the
resource usage for all contexts, but it shows the system limit instead of the combined context limits. The
counter all 0 option is used to show resources that are not currently in use. The Denied statistics indicate
how many times the resource was denied due to the system limit, if available.
hostname# show resource usage system counter all 0
Resource
Telnet
SSH
ASDM
Syslogs [rate]
Conns
Xlates
Hosts
Conns [rate]
Inspects [rate]
Current
0
0
0
1
0
0
0
1
0
Peak
0
0
0
18
1
0
2
1
0
Limit
100
100
32
N/A
280000
N/A
N/A
N/A
N/A
Denied
0
0
0
0
0
0
0
0
0
Context
System
System
System
System
System
System
System
System
System
Monitoring SYN Attacks in Contexts
The security appliance prevents SYN attacks using TCP Intercept. TCP Intercept uses the SYN cookies
algorithm to prevent TCP SYN-flooding attacks. A SYN-flooding attack consists of a series of SYN
packets usually originating from spoofed IP addresses. The constant flood of SYN packets keeps the
server SYN queue full, which prevents it from servicing connection requests. When the embryonic
connection threshold of a connection is crossed, the security appliance acts as a proxy for the server and
generates a SYN-ACK response to the client SYN request. When the security appliance receives an ACK
back from the client, it can then authenticate the client and allow the connection to the server.
You can monitor the rate of attacks for individual contexts using the show perfmon command; you can
monitor the amount of resources being used by TCP intercept for individual contexts using the show
resource usage detail command; you can monitor the resources being used by TCP intercept for the
entire system using the show resource usage summary detail command.
The following is sample output from the show perfmon command that shows the rate of TCP intercepts
for a context called admin.
hostname/admin# show perfmon
Context:admin
PERFMON STATS:
Xlates
Current
0/s
Average
0/s
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Adding and Managing Security Contexts
Managing Security Contexts
Connections
TCP Conns
UDP Conns
URL Access
URL Server Req
WebSns Req
TCP Fixup
HTTP Fixup
FTP Fixup
AAA Authen
AAA Author
AAA Account
TCP Intercept
0/s
0/s
0/s
0/s
0/s
0/s
0/s
0/s
0/s
0/s
0/s
0/s
322779/s
0/s
0/s
0/s
0/s
0/s
0/s
0/s
0/s
0/s
0/s
0/s
0/s
322779/s
The following is sample output from the show resource usage detail command that shows the amount
of resources being used by TCP Intercept for individual contexts. (Sample text in italics shows the TCP
intercept information.)
hostname(config)# show resource usage detail
Resource
Current
Peak
Limit
memory
843732
847288 unlimited
chunk:channels
14
15 unlimited
chunk:fixup
15
15 unlimited
chunk:hole
1
1 unlimited
chunk:ip-users
10
10 unlimited
chunk:list-elem
21
21 unlimited
chunk:list-hdr
3
4 unlimited
chunk:route
2
2 unlimited
chunk:static
1
1 unlimited
tcp-intercepts
328787
803610 unlimited
np-statics
3
3 unlimited
statics
1
1 unlimited
ace-rules
1
1 unlimited
console-access-rul
2
2 unlimited
fixup-rules
14
15 unlimited
memory
959872
960000 unlimited
chunk:channels
15
16 unlimited
chunk:dbgtrace
1
1 unlimited
chunk:fixup
15
15 unlimited
chunk:global
1
1 unlimited
chunk:hole
2
2 unlimited
chunk:ip-users
10
10 unlimited
chunk:udp-ctrl-blk
1
1 unlimited
chunk:list-elem
24
24 unlimited
chunk:list-hdr
5
6 unlimited
chunk:nat
1
1 unlimited
chunk:route
2
2 unlimited
chunk:static
1
1 unlimited
tcp-intercept-rate
16056
16254 unlimited
globals
1
1 unlimited
np-statics
3
3 unlimited
statics
1
1 unlimited
nats
1
1 unlimited
ace-rules
2
2 unlimited
console-access-rul
2
2 unlimited
fixup-rules
14
15 unlimited
memory
232695716
232020648 unlimited
chunk:channels
17
20 unlimited
chunk:dbgtrace
3
3 unlimited
chunk:fixup
15
15 unlimited
chunk:ip-users
4
4 unlimited
chunk:list-elem
1014
1014 unlimited
chunk:list-hdr
1
1 unlimited
chunk:route
1
1 unlimited
Denied
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Context
admin
admin
admin
admin
admin
admin
admin
admin
admin
admin
admin
admin
admin
admin
admin
c1
c1
c1
c1
c1
c1
c1
c1
c1
c1
c1
c1
c1
c1
c1
c1
c1
c1
c1
c1
c1
system
system
system
system
system
system
system
system
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Adding and Managing Security Contexts
Managing Security Contexts
block:16384
block:2048
510
32
885
34
unlimited
unlimited
0 system
0 system
The following sample output shows the resources being used by TCP intercept for the entire system.
(Sample text in italics shows the TCP intercept information.)
hostname(config)# show resource usage summary detail
Resource
Current
Peak
Limit
memory
238421312
238434336 unlimited
chunk:channels
46
48 unlimited
chunk:dbgtrace
4
4 unlimited
chunk:fixup
45
45 unlimited
chunk:global
1
1 unlimited
chunk:hole
3
3 unlimited
chunk:ip-users
24
24 unlimited
chunk:udp-ctrl-blk
1
1 unlimited
chunk:list-elem
1059
1059 unlimited
chunk:list-hdr
10
11 unlimited
chunk:nat
1
1 unlimited
chunk:route
5
5 unlimited
chunk:static
2
2 unlimited
block:16384
510
885 unlimited
block:2048
32
35 unlimited
tcp-intercept-rate
341306
811579 unlimited
globals
1
1 unlimited
np-statics
6
6 unlimited
statics
2
2
N/A
nats
1
1
N/A
ace-rules
3
3
N/A
console-access-rul
4
4
N/A
fixup-rules
43
44
N/A
Denied
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Context
Summary
Summary
Summary
Summary
Summary
Summary
Summary
Summary
Summary
Summary
Summary
Summary
Summary
Summary
Summary
Summary
Summary
Summary
Summary
Summary
Summary
Summary
Summary
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7
Configuring Interface Parameters
This chapter describes how to configure each interface and subinterface for a name, security level, and
IP address. For single context mode, the procedures in this chapter continue the interface configuration
started in Chapter 5, “Configuring Ethernet Settings and Subinterfaces.” For multiple context mode, the
procedures in Chapter 5, “Configuring Ethernet Settings and Subinterfaces,” are performed in the system
execution space, while the procedures in this chapter are performed within each security context.
Note
To configure interfaces for the ASA 5505 adaptive security appliance, see Chapter 4, “Configuring
Switch Ports and VLAN Interfaces for the Cisco ASA 5505 Adaptive Security Appliance.”
This chapter includes the following sections:
•
Security Level Overview, page 7-1
•
Configuring the Interface, page 7-2
•
Allowing Communication Between Interfaces on the Same Security Level, page 7-6
Security Level Overview
Each interface must have a security level from 0 (lowest) to 100 (highest). For example, you should
assign your most secure network, such as the inside host network, to level 100. While the outside
network connected to the Internet can be level 0. Other networks, such as DMZs can be in between. You
can assign interfaces to the same security level. See the “Allowing Communication Between Interfaces
on the Same Security Level” section on page 7-6 for more information.
The level controls the following behavior:
•
Network access—By default, there is an implicit permit from a higher security interface to a lower
security interface (outbound). Hosts on the higher security interface can access any host on a lower
security interface. You can limit access by applying an access list to the interface.
If you enable communication for same security interfaces (see the “Allowing Communication
Between Interfaces on the Same Security Level” section on page 7-6), there is an implicit permit for
interfaces to access other interfaces on the same security level or lower.
•
Inspection engines—Some application inspection engines are dependent on the security level. For
same security interfaces, inspection engines apply to traffic in either direction.
– NetBIOS inspection engine—Applied only for outbound connections.
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Configuring the Interface
– SQL*Net inspection engine—If a control connection for the SQL*Net (formerly OraServ) port
exists between a pair of hosts, then only an inbound data connection is permitted through the
security appliance.
•
Filtering—HTTP(S) and FTP filtering applies only for outbound connections (from a higher level
to a lower level).
For same security interfaces, you can filter traffic in either direction.
•
NAT control—When you enable NAT control, you must configure NAT for hosts on a higher security
interface (inside) when they access hosts on a lower security interface (outside).
Without NAT control, or for same security interfaces, you can choose to use NAT between any
interface, or you can choose not to use NAT. Keep in mind that configuring NAT for an outside
interface might require a special keyword.
•
established command—This command allows return connections from a lower security host to a
higher security host if there is already an established connection from the higher level host to the
lower level host.
For same security interfaces, you can configure established commands for both directions.
Configuring the Interface
By default, all physical interfaces are shut down. You must enable the physical interface before any
traffic can pass through an enabled subinterface. For multiple context mode, if you allocate a physical
interface or subinterface to a context, the interfaces are enabled by default in the context. However,
before traffic can pass through the context interface, you must also enable the interface in the system
configuration. If you shut down an interface in the system execution space, then that interface is down
in all contexts that share it.
Before you can complete your configuration and allow traffic through the security appliance, you need
to configure an interface name, and for routed mode, an IP address. You should also change the security
level from the default, which is 0. If you name an interface “inside” and you do not set the security level
explicitly, then the security appliance sets the security level to 100.
Note
If you are using failover, do not use this procedure to name interfaces that you are reserving for failover
and Stateful Failover communications. See Chapter 14, “Configuring Failover.” to configure the failover
and state links.
For multiple context mode, follow these guidelines:
Note
•
Configure the context interfaces from within each context.
•
You can only configure context interfaces that you already assigned to the context in the system
configuration.
•
The system configuration only lets you configure Ethernet settings and VLANs. The exception is
for failover interfaces; do not configure failover interfaces with this procedure. See the Failover
chapter for more information.
If you change the security level of an interface, and you do not want to wait for existing connections to
time out before the new security information is used, you can clear the connections using the
clear local-host command.
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Configuring Interface Parameters
Configuring the Interface
To configure an interface or subinterface, perform the following steps:
Step 1
To specify the interface you want to configure, enter the following command:
hostname(config)# interface {physical_interface[.subinterface] | mapped_name}
The physical_interface ID includes the type, slot, and port number as type[slot/]port.
The physical interface types include the following:
•
ethernet
•
gigabitethernet
For the PIX 500 series security appliance, enter the type followed by the port number, for example,
ethernet0.
For the ASA 5500 series adaptive security appliance, enter the type followed by slot/port, for example,
gigabitethernet0/1. Interfaces that are built into the chassis are assigned to slot 0, while interfaces on
the 4GE SSM are assigned to slot 1. For the ASA 5550 adaptive security appliance, for maximum
throughput, be sure to balance your traffic over the two interface slots; for example, assign the inside
interface to slot 1 and the outside interface to slot 0.
The ASA 5510 and higher adaptive security appliance also includes the following type:
•
management
The management interface is a Fast Ethernet interface designed for management traffic only, and is
specified as management0/0. You can, however, use it for through traffic if desired (see the
management-only command). In transparent firewall mode, you can use the management interface
in addition to the two interfaces allowed for through traffic. You can also add subinterfaces to the
management interface to provide management in each security context for multiple context mode.
Append the subinterface ID to the physical interface ID separated by a period (.).
In multiple context mode, enter the mapped name if one was assigned using the allocate-interface
command.
For example, enter the following command:
hostname(config)# interface gigabitethernet0/1.1
Step 2
To name the interface, enter the following command:
hostname(config-if)# nameif name
The name is a text string up to 48 characters, and is not case-sensitive. You can change the name by
reentering this command with a new value. Do not enter the no form, because that command causes all
commands that refer to that name to be deleted.
Step 3
To set the security level, enter the following command:
hostname(config-if)# security-level number
Where number is an integer between 0 (lowest) and 100 (highest).
Step 4
(Optional) To set an interface to management-only mode, enter the following command:
hostname(config-if)# management-only
The ASA 5510 and higher adaptive security appliance includes a dedicated management interface called
Management 0/0, which is meant to support traffic to the security appliance. However, you can configure
any interface to be a management-only interface using the management-only command. Also, for
Management 0/0, you can disable management-only mode so the interface can pass through traffic just
like any other interface.
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Configuring the Interface
Note
Step 5
Transparent firewall mode allows only two interfaces to pass through traffic; however, on the
The ASA 5510 and higher adaptive security appliance, you can use the Management 0/0
interface (either the physical interface or a subinterface) as a third interface for management
traffic. The mode is not configurable in this case and must always be management-only.
To set the IP address, enter one of the following commands.
In routed firewall mode, you set the IP address for all interfaces. In transparent firewall mode, you do
not set the IP address for each interface, but rather for the whole security appliance or context. The
exception is for the Management 0/0 management-only interface, which does not pass through traffic.
To set the management IP address for transparent firewall mode, see the “Setting the Management IP
Address for a Transparent Firewall” section on page 8-5. To set the IP address of the Management 0/0
interface or subinterface, use one of the following commands.
To set an IPv6 address, see the “Configuring IPv6 on an Interface” section on page 12-3.
For failover, you must set the IP address an standby address manually; DHCP and PPPoE are not
supported.
•
To set the IP address manually, enter the following command:
hostname(config-if)# ip address ip_address [mask] [standby ip_address]
The standby keyword and address is used for failover. See Chapter 14, “Configuring Failover,” for
more information.
•
To obtain an IP address from a DHCP server, enter the following command:
hostname(config-if)# ip address dhcp [setroute]
Reenter this command to reset the DHCP lease and request a new lease.
If you do not enable the interface using the no shutdown command before you enter the ip address
dhcp command, some DHCP requests might not be sent.
•
Step 6
To obtain an IP address from a PPPoE server, see Chapter 35, “Configuring the PPPoE Client.”
(Optional) To assign a private MAC address to this interface, enter the following command:
hostname(config-if)# mac-address mac_address [standby mac_address]
The mac_address is in H.H.H format, where H is a 16-bit hexadecimal digit. For example, the
MAC address 00-0C-F1-42-4C-DE would be entered as 000C.F142.4CDE.
By default, the physical interface uses the burned-in MAC address, and all subinterfaces of a physical
interface use the same burned-in MAC address.
For use with failover, set the standby MAC address. If the active unit fails over and the standby unit
becomes active, the new active unit starts using the active MAC addresses to minimize network
disruption, while the old active unit uses the standby address.
In multiple context mode, if you share an interface between contexts, you can assign a unique MAC
address to the interface in each context. This feature lets the security appliance easily classify packets
into the appropriate context. Using a shared interface without unique MAC addresses is possible, but has
some limitations. See the “How the Security Appliance Classifies Packets” section on page 3-3 for more
information. You can assign each MAC address manually, or you can automatically generate MAC
addresses for shared interfaces in contexts. See the “Automatically Assigning MAC Addresses to
Context Interfaces” section on page 6-11 to automatically generate MAC addresses. If you automatically
generate MAC addresses, you can use the mac-address command to override the generated address.
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Configuring Interface Parameters
Configuring the Interface
For single context mode, or for interfaces that are not shared in multiple context mode, you might want
to assign unique MAC addresses to subinterfaces. For example, your service provider might perform
access control based on the MAC address.
Step 7
To enable the interface, if it is not already enabled, enter the following command:
hostname(config-if)# no shutdown
To disable the interface, enter the shutdown command. If you enter the shutdown command for a
physical interface, you also shut down all subinterfaces. If you shut down an interface in the system
execution space, then that interface is shut down in all contexts that share it, even though the context
configurations show the interface as enabled.
The following example configures parameters for the physical interface in single mode:
hostname(config)# interface gigabitethernet0/1
hostname(config-if)# speed 1000
hostname(config-if)# duplex full
hostname(config-if)# nameif inside
hostname(config-if)# security-level 100
hostname(config-if)# ip address 10.1.1.1 255.255.255.0
hostname(config-if)# no shutdown
The following example configures parameters for a subinterface in single mode:
hostname(config)# interface gigabitethernet0/1.1
hostname(config-subif)# vlan 101
hostname(config-subif)# nameif dmz1
hostname(config-subif)# security-level 50
hostname(config-subif)# ip address 10.1.2.1 255.255.255.0
hostname(config-subif)# mac-address 000C.F142.4CDE standby 020C.F142.4CDE
hostname(config-subif)# no shutdown
The following example configures interface parameters in multiple context mode for the system
configuration, and allocates the gigabitethernet 0/1.1 subinterface to contextA:
hostname(config)# interface gigabitethernet0/1
hostname(config-if)# speed 1000
hostname(config-if)# duplex full
hostname(config-if)# no shutdown
hostname(config-if)# interface gigabitethernet0/1.1
hostname(config-subif)# vlan 101
hostname(config-subif)# no shutdown
hostname(config-subif)# context contextA
hostname(config-ctx)# ...
hostname(config-ctx)# allocate-interface gigabitethernet0/1.1
The following example configures parameters in multiple context mode for the context configuration:
hostname/contextA(config)# interface gigabitethernet0/1.1
hostname/contextA(config-if)# nameif inside
hostname/contextA(config-if)# security-level 100
hostname/contextA(config-if)# ip address 10.1.2.1 255.255.255.0
hostname/contextA(config-if)# mac-address 030C.F142.4CDE standby 040C.F142.4CDE
hostname/contextA(config-if)# no shutdown
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Configuring Interface Parameters
Allowing Communication Between Interfaces on the Same Security Level
Allowing Communication Between Interfaces on the Same
Security Level
By default, interfaces on the same security level cannot communicate with each other. Allowing
communication between same security interfaces provides the following benefits:
•
You can configure more than 101 communicating interfaces.
If you use different levels for each interface and do not assign any interfaces to the same security
level, you can configure only one interface per level (0 to 100).
•
Note
You want traffic to flow freely between all same security interfaces without access lists.
If you enable NAT control, you do not need to configure NAT between same security level interfaces.
See the “NAT and Same Security Level Interfaces” section on page 17-12 for more information on NAT
and same security level interfaces.
If you enable same security interface communication, you can still configure interfaces at different
security levels as usual.
To enable interfaces on the same security level so that they can communicate with each other, enter the
following command:
hostname(config)# same-security-traffic permit inter-interface
To disable this setting, use the no form of this command.
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8
Configuring Basic Settings
This chapter describes how to configure basic settings on your security appliance that are typically
required for a functioning configuration. This chapter includes the following sections:
•
Changing the Login Password, page 8-1
•
Changing the Enable Password, page 8-1
•
Setting the Hostname, page 8-2
•
Setting the Domain Name, page 8-2
•
Setting the Date and Time, page 8-2
•
Setting the Management IP Address for a Transparent Firewall, page 8-5
Changing the Login Password
The login password is used for Telnet and SSH connections. By default, the login password is “cisco.”
To change the password, enter the following command:
hostname(config)# {passwd | password} password
You can enter passwd or password. The password is a case-sensitive password of up to 16 alphanumeric
and special characters. You can use any character in the password except a question mark or a space.
The password is saved in the configuration in encrypted form, so you cannot view the original password
after you enter it. Use the no password command to restore the password to the default setting.
Changing the Enable Password
The enable password lets you enter privileged EXEC mode. By default, the enable password is blank. To
change the enable password, enter the following command:
hostname(config)# enable password password
The password is a case-sensitive password of up to 16 alphanumeric and special characters. You can use
any character in the password except a question mark or a space.
This command changes the password for the highest privilege level. If you configure local command
authorization, you can set enable passwords for each privilege level from 0 to 15.
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Configuring Basic Settings
Setting the Hostname
The password is saved in the configuration in encrypted form, so you cannot view the original password
after you enter it. Enter the enable password command without a password to set the password to the
default, which is blank.
Setting the Hostname
When you set a hostname for the security appliance, that name appears in the command line prompt. If
you establish sessions to multiple devices, the hostname helps you keep track of where you enter
commands. The default hostname depends on your platform.
For multiple context mode, the hostname that you set in the system execution space appears in the
command line prompt for all contexts. The hostname that you optionally set within a context does not
appear in the command line, but can be used by the banner command $(hostname) token.
To specify the hostname for the security appliance or for a context, enter the following command:
hostname(config)# hostname name
This name can be up to 63 characters. A hostname must start and end with a letter or digit, and have as
interior characters only letters, digits, or a hyphen.
This name appears in the command line prompt. For example:
hostname(config)# hostname farscape
farscape(config)#
Setting the Domain Name
The security appliance appends the domain name as a suffix to unqualified names. For example, if you
set the domain name to “example.com,” and specify a syslog server by the unqualified name of “jupiter,”
then the security appliance qualifies the name to “jupiter.example.com.”
The default domain name is default.domain.invalid.
For multiple context mode, you can set the domain name for each context, as well as within the system
execution space.
To specify the domain name for the security appliance, enter the following command:
hostname(config)# domain-name name
For example, to set the domain as example.com, enter the following command:
hostname(config)# domain-name example.com
Setting the Date and Time
This section describes how to set the date and time, either manually or dynamically using an NTP server.
Time derived from an NTP server overrides any time set manually. This section also describes how to
set the time zone and daylight saving time date range.
Note
In multiple context mode, set the time in the system configuration only.
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Configuring Basic Settings
Setting the Date and Time
This section includes the following topics:
•
Setting the Time Zone and Daylight Saving Time Date Range, page 8-3
•
Setting the Date and Time Using an NTP Server, page 8-4
•
Setting the Date and Time Manually, page 8-4
Setting the Time Zone and Daylight Saving Time Date Range
By default, the time zone is UTC and the daylight saving time date range is from 2:00 a.m. on the first
Sunday in April to 2:00 a.m. on the last Sunday in October. To change the time zone and daylight saving
time date range, perform the following steps:
Step 1
To set the time zone, enter the following command in global configuration mode:
hostname(config)# clock timezone zone [-]hours [minutes]
Where zone specifies the time zone as a string, for example, PST for Pacific Standard Time.
The [-]hours value sets the number of hours of offset from UTC. For example, PST is -8 hours.
The minutes value sets the number of minutes of offset from UTC.
Step 2
To change the date range for daylight saving time from the default, enter one of the following commands.
The default recurring date range is from 2:00 a.m. on the first Sunday in April to 2:00 a.m. on the last
Sunday in October.
•
To set the start and end dates for daylight saving time as a specific date in a specific year, enter the
following command:
hostname(config)# clock summer-time zone date {day month | month day} year hh:mm {day
month | month day} year hh:mm [offset]
If you use this command, you need to reset the dates every year.
The zone value specifies the time zone as a string, for example, PDT for Pacific Daylight Time.
The day value sets the day of the month, from 1 to 31. You can enter the day and month as April 1
or as 1 April, for example, depending on your standard date format.
The month value sets the month as a string. You can enter the day and month as April 1 or as 1 April,
for example, depending on your standard date format.
The year value sets the year using four digits, for example, 2004. The year range is 1993 to 2035.
The hh:mm value sets the hour and minutes in 24-hour time.
The offset value sets the number of minutes to change the time for daylight saving time. By default,
the value is 60 minutes.
•
To specify the start and end dates for daylight saving time, in the form of a day and time of the
month, and not a specific date in a year, enter the following command.
hostname(config)# clock summer-time zone recurring [week weekday month hh:mm week
weekday month hh:mm] [offset]
This command lets you set a recurring date range that you do not need to alter yearly.
The zone value specifies the time zone as a string, for example, PDT for Pacific Daylight Time.
The week value specifies the week of the month as an integer between 1 and 4 or as the words first
or last. For example, if the day might fall in the partial fifth week, then specify last.
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Setting the Date and Time
The weekday value specifies the day of the week: Monday, Tuesday, Wednesday, and so on.
The month value sets the month as a string.
The hh:mm value sets the hour and minutes in 24-hour time.
The offset value sets the number of minutes to change the time for daylight saving time. By default,
the value is 60 minutes.
Setting the Date and Time Using an NTP Server
To obtain the date and time from an NTP server, perform the following steps:
Step 1
To configure authentication with an NTP server, perform the following steps:
a.
To enable authentication, enter the following command:
hostname(config)# ntp authenticate
b.
To specify an authentication key ID to be a trusted key, which is required for authentication with an
NTP server, enter the following command:
hostname(config)# ntp trusted-key key_id
Where the key_id is between 1 and 4294967295. You can enter multiple trusted keys for use with
multiple servers.
c.
To set a key to authenticate with an NTP server, enter the following command:
hostname(config)# ntp authentication-key key_id md5 key
Where key_id is the ID you set in Step 1b using the ntp trusted-key command, and key is a string
up to 32 characters in length.
Step 2
To identify an NTP server, enter the following command:
hostname(config)# ntp server ip_address [key key_id] [source interface_name] [prefer]
Where the key_id is the ID you set in Step 1b using the ntp trusted-key command.
The source interface_name identifies the outgoing interface for NTP packets if you do not want to use
the default interface in the routing table. Because the system does not include any interfaces in multiple
context mode, specify an interface name defined in the admin context.
The prefer keyword sets this NTP server as the preferred server if multiple servers have similar
accuracy. NTP uses an algorithm to determine which server is the most accurate and synchronizes to that
one. If servers are of similar accuracy, then the prefer keyword specifies which of those servers to use.
However, if a server is significantly more accurate than the preferred one, the security appliance uses the
more accurate one. For example, the security appliance uses a server of stratum 2 over a server of
stratum 3 that is preferred.
You can identify multiple servers; the security appliance uses the most accurate server.
Setting the Date and Time Manually
To set the date time manually, enter the following command:
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hostname# clock set hh:mm:ss {month day | day month} year
Where hh:mm:ss sets the hour, minutes, and seconds in 24-hour time. For example, set 20:54:00 for 8:54
pm.
The day value sets the day of the month, from 1 to 31. You can enter the day and month as april 1 or as
1 april, for example, depending on your standard date format.
The month value sets the month. Depending on your standard date format, you can enter the day and
month as april 1 or as 1 april.
The year value sets the year using four digits, for example, 2004. The year range is 1993 to 2035.
The default time zone is UTC. If you change the time zone after you enter the clock set command using
the clock timezone command, the time automatically adjusts to the new time zone.
This command sets the time in the hardware chip, and does not save the time in the configuration file.
This time endures reboots. Unlike the other clock commands, this command is a privileged EXEC
command. To reset the clock, you need to set a new time for the clock set command.
Setting the Management IP Address for a Transparent Firewall
Transparent firewall mode only
A transparent firewall does not participate in IP routing. The only IP configuration required for the
security appliance is to set the management IP address. This address is required because the security
appliance uses this address as the source address for traffic originating on the security appliance, such
as system messages or communications with AAA servers. You can also use this address for remote
management access.
For multiple context mode, set the management IP address within each context.
To set the management IP address, enter the following command:
hostname(config)# ip address ip_address [mask] [standby ip_address]
This address must be on the same subnet as the upstream and downstream routers. You cannot set the
subnet to a host subnet (255.255.255.255). This address must be IPv4; the transparent firewall does not
support IPv6.
The standby keyword and address is used for failover. See Chapter 14, “Configuring Failover,” for more
information.
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9
Configuring IP Routing
This chapter describes how to configure IP routing on the security appliance. This chapter includes the
following sections:
•
How Routing Behaves Within the ASA Security Appliance, page 9-1
•
Configuring Static and Default Routes, page 9-2
•
Defining Route Maps, page 9-7
•
Configuring OSPF, page 9-8
•
Configuring RIP, page 9-20
•
The Routing Table, page 9-23
•
Dynamic Routing and Failover, page 9-26
How Routing Behaves Within the ASA Security Appliance
The ASA security appliance uses both routing table and XLATE tables for routing decisions. To handle
destination IP translated traffic, that is, untranslated traffic, ASA searches for existing XLATE, or static
translation to select the egress interface. The selection process is as follows:
Egress Interface Selection Process
1.
If destination IP translating XLATE already exists, the egress interface for the packet is determined
from the XLATE table, but not from the routing table.
2.
If destination IP translating XLATE does not exist, but a matching static translation exists, then the
egress interface is determined from the static route and an XLATE is created, and the routing table
is not used.
3.
If destination IP translating XLATE does not exist and no matching static translation exists, the
packet is not destination IP translated. FWSM processes this packet by looking up the route to select
egress interface, then source IP translation is performed (if necessary).
For regular dynamic outbound NAT, initial outgoing packets are routed using the route table and
then creating the XLATE. Incoming return packets are forwarded using existing XLATE only. For
static NAT, destination translated incoming packets are always forwarded using existing XLATE or
static translation rules.
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Next Hop Selection Process
After selecting egress interface using any method described above, an additional route lookup is
performed to find out suitable next hop(s) that belong to previously selected egress interface. If there are
no routes in routing table that explicitly belong to selected interface, the packet is dropped with level 6
error message 110001 "no route to host", even if there is another route for a given destination network
that belongs to different egress interface. If the route that belongs to selected egress interface is found,
the packet is forwarded to corresponding next hop.
Load sharing on the security appliance is possible only for multiple next-hops available using single
egress interface. Load sharing cannot share multiple egress interfaces.
If dynamic routing is in use on security appliance and route table changes after XLATE creation, for
example route flap, then destination translated traffic is still forwarded using old XLATE, not via route
table, until XLATE times out. It may be either forwarded to wrong interface or dropped with message
110001 "no route to host" if old route was removed from the old interface and attached to another one
by routing process.
The same problem may happen when there is no route flaps on the security appliance itself, but some
routing process is flapping around it, sending source translated packets that belong to the same flow
through FWSM using different interfaces. Destination translated return packets may be forwarded back
using the wrong egress interface.
This issue has a high probability in same security traffic configuration, where virtually any traffic may
be either source-translated or destination-translated, depending on direction of initial packet in the flow.
When this issue occurs after a route flap, it can be resolved manually by using the clear xlate
command, or automatically resolved by an XLATE timeout. XLATE timeout may be decreased if
necessary. To ensure that this rarely happens, make sure that there is no route flaps on security appliance
and around it. That is, ensure that destination translated packets that belong to the same flow are always
forwarded the same way through the security appliance.
Configuring Static and Default Routes
This section describes how to configure static and default routes on the security appliance.
Multiple context mode does not support dynamic routing, so you must use static routes for any networks
to which the security appliance is not directly connected; for example, when there is a router between a
network and the security appliance.
You might want to use static routes in single context mode in the following cases:
•
Your networks use a different router discovery protocol from RIP or OSPF.
•
Your network is small and you can easily manage static routes.
•
You do not want the traffic or CPU overhead associated with routing protocols.
The simplest option is to configure a default route to send all traffic to an upstream router, relying on the
router to route the traffic for you. However, in some cases the default gateway might not be able to reach
the destination network, so you must also configure more specific static routes. For example, if the
default gateway is outside, then the default route cannot direct traffic to any inside networks that are not
directly connected to the security appliance.
In transparent firewall mode, for traffic that originates on the security appliance and is destined for a
non-directly connected network, you need to configure either a default route or static routes so the
security appliance knows out of which interface to send traffic. Traffic that originates on the security
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appliance might include communications to a syslog server, Websense or N2H2 server, or AAA server.
If you have servers that cannot all be reached through a single default route, then you must configure
static routes.
The security appliance supports up to three equal cost routes on the same interface for load balancing.
This section includes the following topics:
•
Configuring a Static Route, page 9-3
•
Configuring a Default Route, page 9-4
•
Configuring Static Route Tracking, page 9-5
For information about configuring IPv6 static and default routes, see the “Configuring IPv6 Default and
Static Routes” section on page 12-5.
Configuring a Static Route
To add a static route, enter the following command:
hostname(config)# route if_name dest_ip mask gateway_ip [distance]
The dest_ip and mask is the IP address for the destination network and the gateway_ip is the address of
the next-hop router.The addresses you specify for the static route are the addresses that are in the packet
before entering the security appliance and performing NAT.
The distance is the administrative distance for the route. The default is 1 if you do not specify a value.
Administrative distance is a parameter used to compare routes among different routing protocols. The
default administrative distance for static routes is 1, giving it precedence over routes discovered by
dynamic routing protocols but not directly connect routes. The default administrative distance for routes
discovered by OSPF is 110. If a static route has the same administrative distance as a dynamic route, the
static routes take precedence. Connected routes always take precedence over static or dynamically
discovered routes.
Static routes remain in the routing table even if the specified gateway becomes unavailable. If the
specified gateway becomes unavailable, you need to remove the static route from the routing table
manually. However, static routes are removed from the routing table if the specified interface goes down.
They are reinstated when the interface comes back up.
Note
If you create a static route with an administrative distance greater than the administrative distance of the
routing protocol running on the security appliance, then a route to the specified destination discovered
by the routing protocol takes precedence over the static route. The static route is used only if the
dynamically discovered route is removed from the routing table.
The following example creates a static route that sends all traffic destined for 10.1.1.0/24 to the router
(10.1.2.45) connected to the inside interface:
hostname(config)# route inside 10.1.1.0 255.255.255.0 10.1.2.45 1
You can define up to three equal cost routes to the same destination per interface. ECMP is not supported
across multiple interfaces. With ECMP, the traffic is not necessarily divided evenly between the routes;
traffic is distributed among the specified gateways based on an algorithm that hashes the source and
destination IP addresses.
The following example shows static routes that are equal cost routes that direct traffic to three different
gateways on the outside interface. The security appliance distributes the traffic among the specified
gateways.
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hostname(config)# route outside 10.10.10.0 255.255.255.0 192.168.1.1
hostname(config)# route outside 10.10.10.0 255.255.255.0 192.168.1.2
hostname(config)# route outside 10.10.10.0 255.255.255.0 192.168.1.3
Configuring a Default Route
A default route identifies the gateway IP address to which the security appliance sends all IP packets for
which it does not have a learned or static route. A default route is simply a static route with 0.0.0.0/0 as
the destination IP address. Routes that identify a specific destination take precedence over the default
route.
You can define up to three equal cost default route entries per device. Defining more than one equal cost
default route entry causes the traffic sent to the default route to be distributed among the specified
gateways. When defining more than one default route, you must specify the same interface for each
entry.
If you attempt to define more than three equal cost default routes, or if you attempt to define a default
route with a different interface than a previously defined default route, you receive the message
“ERROR: Cannot add route entry, possible conflict with existing routes.”
You can define a separate default route for tunneled traffic along with the standard default route. When
you create a default route with the tunneled option, all traffic from a tunnel terminating on the security
appliance that cannot be routed using learned or static routes, is sent to this route. For traffic emerging
from a tunnel, this route overrides over any other configured or learned default routes.
The following restrictions apply to default routes with the tunneled option:
•
Do not enable unicast RPF (ip verify reverse-path) on the egress interface of tunneled route.
Enabling uRPF on the egress interface of a tunneled route causes the session to fail.
•
Do not enable TCP intercept on the egress interface of the tunneled route. Doing so causes the
session to fail.
•
Do not use the VoIP inspection engines (CTIQBE, H.323, GTP, MGCP, RTSP, SIP, SKINNY), the
DNS inspect engine, or the DCE RPC inspection engine with tunneled routes. These inspection
engines ignore the tunneled route.
You cannot define more than one default route with the tunneled option; ECMP for tunneled traffic is
not supported.
To define the default route, enter the following command:
hostname(config)# route if_name 0.0.0.0 0.0.0.0 gateway_ip [distance | tunneled]
Tip
You can enter 0 0 instead of 0.0.0.0 0.0.0.0 for the destination network address and mask, for example:
hostname(config)# route outside 0 0 192.168.1 1
The following example shows a security appliance configured with three equal cost default routes and a
default route for tunneled traffic. Unencrypted traffic received by the security appliance for which there
is no static or learned route is distributed among the gateways with the IP addresses 192.168.2.1,
192.168.2.2, 192.168.2.3. Encrypted traffic receive by the security appliance for which there is no static
or learned route is passed to the gateway with the IP address 192.168.2.4.
hostname(config)#
hostname(config)#
hostname(config)#
hostname(config)#
route
route
route
route
outside
outside
outside
outside
0
0
0
0
0
0
0
0
192.168.2.1
192.168.2.2
192.168.2.3
192.168.2.4 tunneled
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Configuring Static Route Tracking
One of the problems with static routes is that there is no inherent mechanism for determining if the route
is up or down. They remain in the routing table even if the next hop gateway becomes unavailable. Static
routes are only removed from the routing table if the associated interface on the security appliance goes
down.
The static route tracking feature provides a method for tracking the availability of a static route and
installing a backup route if the primary route should fail. This allows you to, for example, define a
default route to an ISP gateway and a backup default route to a secondary ISP in case the primary ISP
becomes unavailable.
The security appliance does this by associating a static route with a monitoring target that you define. It
monitors the target using ICMP echo requests. If an echo reply is not received within a specified time
period, the object is considered down and the associated route is removed from the routing table. A
previously configured backup route is used in place of the removed route.
When selecting a monitoring target, you need to make sure it can respond to ICMP echo requests. The
target can be any network object that you choose, but you should consider using:
•
the ISP gateway (for dual ISP support) address
•
the next hop gateway address (if you are concerned about the availability of the gateway)
•
a server on the target network, such as a AAA server, that the security appliance needs to
communicate with
•
a persistent network object on the destination network (a desktop or notebook computer that may be
shut down at night is not a good choice)
You can configure static route tracking for statically defined routes or default routes obtained through
DHCP or PPPoE. You can only enable PPPoE clients on multiple interface with route tracking.
To configure static route tracking, perform the following steps:
Step 1
Configure the tracked object monitoring parameters:
a.
Define the monitoring process:
hostname(config)# sla monitor sla_id
If you are configuring a new monitoring process, you are taken to SLA monitor configuration mode.
If you are changing the monitoring parameters for an unscheduled monitoring process that already
has a type defined, you are taken directly to the SLA protocol configuration mode.
b.
Specify the monitoring protocol. If you are changing the monitoring parameters for an unscheduled
monitoring process that already has a type defined, you are taken directly to SLA protocol
configuration mode and cannot change this setting.
hostname(config-sla-monitor)# type echo protocol ipIcmpEcho target_ip interface
if_name
The target_ip is the IP address of the network object whose availability the tracking process
monitors. While this object is available, the tracking process route is installed in the routing table.
When this object becomes unavailable, the tracking process removed the route and the backup route
is used in its place.
c.
Schedule the monitoring process:
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hostname(config)# sla monitor schedule sla_id [life {forever | seconds}] [start-time
{hh:mm[:ss] [month day | day month] | pending | now | after hh:mm:ss}] [ageout
seconds] [recurring]
Typically, you will use sla monitor schedule sla_id life forever start-time now for the monitoring
schedule, and allow the monitoring configuration determine how often the testing occurs. However,
you can schedule this monitoring process to begin in the future and to only occur at specified times.
Step 2
Associate a tracked static route with the SLA monitoring process by entering the following command:
hostname(config)# track track_id rtr sla_id reachability
The track_id is a tracking number you assign with this command. The sla_id is the ID number of the
SLA process you defined in Step 1.
Step 3
Define the static route to be installed in the routing table while the tracked object is reachable using one
of the following options:
•
To track a static route, enter the following command:
hostname(config)# route if_name dest_ip mask gateway_ip [admin_distance] track
track_id
You cannot use the tunneled option with the route command with static route tracking.
•
To track a default route obtained through DHCP, enter the following commands:
hostname(config)# interface phy_if
hostname(config-if)# dhcp client route track track_id
hostname(config-if)# ip addresss dhcp setroute
hostname(config-if)# exit
Note
•
You must use the setroute argument with the ip address dhcp command to obtain the
default route using DHCP.
To track a default route obtained through PPPoE, enter the following commands:
hostname(config)# interface phy_if
hostname(config-if)# pppoe client route track track_id
hostname(config-if)# ip addresss pppoe setroute
hostname(config-if)# exit
Note
Step 4
You must use the setroute argument with the ip address pppoe command to obtain the
default route using PPPoE.
Define the backup route to use when the tracked object is unavailable using one of the following options.
The administrative distance of the backup route must be greater than the administrative distance of the
tracked route. If it is not, the backup route will be installed in the routing table instead of the tracked
route.
•
To use a static route, enter the following command:
hostname(config)# route if_name dest_ip mask gateway_ip [admin_distance]
The static route must have the same destination and mask as the tracked route. If you are tracking a
default route obtained through DHCP or PPPoE, then the address and mask would be 0.0.0.0 0.0.0.0.
•
To use a default route obtained through DHCP, enter the following commands:
hostname(config)# interface phy_if
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hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
hostname(config-if)#
dhcp client route track track_id
dhcp client route distance admin_distance
ip addresss dhcp setroute
exit
You must use the setroute argument with the ip address dhcp command to obtain the default route
using DHCP. Make sure the administrative distance is greater than the administrative distance of the
tracked route.
•
To use a default route obtained through PPPoE, enter the following commands:
hostname(config)# interface phy_if
hostname(config-if)# pppoe client route track track_id
hostname(config-if)# pppoe client route distance admin_distance
hostname(config-if)# ip addresss pppoe setroute
hostname(config-if)# exit
You must use the setroute argument with the ip address pppoe command to obtain the default route
using PPPoE. Make sure the administrative distance is greater than the administrative distance of
the tracked route.
Defining Route Maps
Route maps are used when redistributing routes into an OSPF or RIP routing process. They are also used
when generating a default route into an OSPF routing process. A route map defines which of the routes
from the specified routing protocol are allowed to be redistributed into the target routing process.
To define a route map, perform the following steps:
Step 1
To create a route map entry, enter the following command:
hostname(config)# route-map name {permit | deny} [sequence_number]
Route map entries are read in order. You can identify the order using the sequence_number option, or
the security appliance uses the order in which you add the entries.
Step 2
Enter one or more match commands:
•
To match any routes that have a destination network that matches a standard ACL, enter the
following command:
hostname(config-route-map)# match ip address acl_id [acl_id] [...]
If you specify more than one ACL, then the route can match any of the ACLs.
•
To match any routes that have a specified metric, enter the following command:
hostname(config-route-map)# match metric metric_value
The metric_value can be from 0 to 4294967295.
•
To match any routes that have a next hop router address that matches a standard ACL, enter the
following command:
hostname(config-route-map)# match ip next-hop acl_id [acl_id] [...]
If you specify more than one ACL, then the route can match any of the ACLs.
•
To match any routes with the specified next hop interface, enter the following command:
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hostname(config-route-map)# match interface if_name
If you specify more than one interface, then the route can match either interface.
•
To match any routes that have been advertised by routers that match a standard ACL, enter the
following command:
hostname(config-route-map)# match ip route-source acl_id [acl_id] [...]
If you specify more than one ACL, then the route can match any of the ACLs.
•
To match the route type, enter the following command:
hostname(config-route-map)# match route-type {internal | external [type-1 | type-2]}
Step 3
Enter one or more set commands.
If a route matches the match commands, then the following set commands determine the action to
perform on the route before redistributing it.
•
To set the metric, enter the following command:
hostname(config-route-map)# set metric metric_value
The metric_value can be a value between 0 and 294967295
•
To set the metric type, enter the following command:
hostname(config-route-map)# set metric-type {type-1 | type-2}
The following example shows how to redistribute routes with a hop count equal to 1 into OSPF. The
security appliance redistributes these routes as external LSAs with a metric of 5, metric type of Type 1.
hostname(config)# route-map
hostname(config-route-map)#
hostname(config-route-map)#
hostname(config-route-map)#
1-to-2 permit
match metric 1
set metric 5
set metric-type type-1
Configuring OSPF
This section describes how to configure OSPF. This section includes the following topics:
•
OSPF Overview, page 9-9
•
Enabling OSPF, page 9-9
•
Redistributing Routes Into OSPF, page 9-10
•
Configuring OSPF Interface Parameters, page 9-11
•
Configuring OSPF Area Parameters, page 9-13
•
Configuring OSPF NSSA, page 9-14
•
Defining Static OSPF Neighbors, page 9-16
•
Configuring Route Summarization Between OSPF Areas, page 9-15
•
Configuring Route Summarization When Redistributing Routes into OSPF, page 9-16
•
Generating a Default Route, page 9-17
•
Configuring Route Calculation Timers, page 9-17
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•
Logging Neighbors Going Up or Down, page 9-18
•
Displaying OSPF Update Packet Pacing, page 9-18
•
Monitoring OSPF, page 9-19
•
Restarting the OSPF Process, page 9-20
OSPF Overview
OSPF uses a link-state algorithm to build and calculate the shortest path to all known destinations. Each
router in an OSPF area contains an identical link-state database, which is a list of each of the router
usable interfaces and reachable neighbors.
The advantages of OSPF over RIP include the following:
•
OSPF link-state database updates are sent less frequently than RIP updates, and the link-state
database is updated instantly rather than gradually as stale information is timed out.
•
Routing decisions are based on cost, which is an indication of the overhead required to send packets
across a certain interface. The security appliance calculates the cost of an interface based on link
bandwidth rather than the number of hops to the destination. The cost can be configured to specify
preferred paths.
The disadvantage of shortest path first algorithms is that they require a lot of CPU cycles and memory.
The security appliance can run two processes of OSPF protocol simultaneously, on different sets of
interfaces. You might want to run two processes if you have interfaces that use the same IP addresses
(NAT allows these interfaces to coexist, but OSPF does not allow overlapping addresses). Or you might
want to run one process on the inside, and another on the outside, and redistribute a subset of routes
between the two processes. Similarly, you might need to segregate private addresses from public
addresses.
You can redistribute routes into an OSPF routing process from another OSPF routing process, a RIP
routing process, or from static and connected routes configured on OSPF-enabled interfaces.
The security appliance supports the following OSPF features:
•
Support of intra-area, interarea, and external (Type I and Type II) routes.
•
Support of a virtual link.
•
OSPF LSA flooding.
•
Authentication to OSPF packets (both password and MD5 authentication).
•
Support for configuring the security appliance as a designated router or a designated backup router.
The security appliance also can be set up as an ABR; however, the ability to configure the security
appliance as an ASBR is limited to default information only (for example, injecting a default route).
•
Support for stub areas and not-so-stubby-areas.
•
Area boundary router type-3 LSA filtering.
•
Advertisement of static and global address translations.
Enabling OSPF
To enable OSPF, you need to create an OSPF routing process, specify the range of IP addresses
associated with the routing process, then assign area IDs associated with that range of IP addresses.
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Configuring OSPF
To enable OSPF, perform the following steps:
Step 1
To create an OSPF routing process, enter the following command:
hostname(config)# router ospf process_id
This command enters the router configuration mode for this OSPF process.
The process_id is an internally used identifier for this routing process. It can be any positive integer. This
ID does not have to match the ID on any other device; it is for internal use only. You can use a maximum
of two processes.
Step 2
To define the IP addresses on which OSPF runs and to define the area ID for that interface, enter the
following command:
hostname(config-router)# network ip_address mask area area_id
The following example shows how to enable OSPF:
hostname(config)# router ospf 2
hostname(config-router)# network 10.0.0.0 255.0.0.0 area 0
Redistributing Routes Into OSPF
The security appliance can control the redistribution of routes between OSPF routing processes. The
security appliance matches and changes routes according to settings in the redistribute command or by
using a route map. See also the “Generating a Default Route” section on page 9-17 for another use for
route maps.
To redistribute static, connected, RIP, or OSPF routes into an OSPF process, perform the following steps:
Step 1
(Optional) Create a route-map to further define which routes from the specified routing protocol are
redistributed in to the OSPF routing process. See the “Defining Route Maps” section on page 9-7.
Step 2
If you have not already done so, enter the router configuration mode for the OSPF process you want to
redistribute into by entering the following command:
hostname(config)# router ospf process_id
Step 3
To specify the routes you want to redistribute, enter the following command:
hostname(config-router)# redistribute {ospf process_id
[match {internal | external 1 | external 2}] | static | connected | rip}
[metric metric-value] [metric-type {type-1 | type-2}] [tag tag_value] [subnets] [route-map
map_name]
The ospf process_id, static, connected, and rip keywords specify from where you want to redistribute
routes.
You can either use the options in this command to match and set route properties, or you can use a route
map. The tag and subnets options do not have equivalents in the route-map command. If you use both
a route map and options in the redistribute command, then they must match.
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The following example shows route redistribution from OSPF process 1 into OSPF process 2 by
matching routes with a metric equal to 1. The security appliance redistributes these routes as external
LSAs with a metric of 5, metric type of Type 1, and a tag equal to 1.
hostname(config)# route-map 1-to-2 permit
hostname(config-route-map)# match metric 1
hostname(config-route-map)# set metric 5
hostname(config-route-map)# set metric-type type-1
hostname(config-route-map)# set tag 1
hostname(config-route-map)# router ospf 2
hostname(config-router)# redistribute ospf 1 route-map 1-to-2
The following example shows the specified OSPF process routes being redistributed into OSPF
process 109. The OSPF metric is remapped to 100.
hostname(config)# router ospf 109
hostname(config-router)# redistribute ospf 108 metric 100 subnets
The following example shows route redistribution where the link-state cost is specified as 5 and the
metric type is set to external, indicating that it has lower priority than internal metrics.
hostname(config)# router ospf 1
hostname(config-router)# redistribute ospf 2 metric 5 metric-type external
Configuring OSPF Interface Parameters
You can alter some interface-specific OSPF parameters as necessary. You are not required to alter any
of these parameters, but the following interface parameters must be consistent across all routers in an
attached network: ospf hello-interval, ospf dead-interval, and ospf authentication-key. Be sure that if
you configure any of these parameters, the configurations for all routers on your network have
compatible values.
To configure OSPF interface parameters, perform the following steps:
Step 1
To enter the interface configuration mode, enter the following command:
hostname(config)# interface interface_name
Step 2
Enter any of the following commands:
•
To specify the authentication type for an interface, enter the following command:
hostname(config-interface)# ospf authentication [message-digest | null]
•
To assign a password to be used by neighboring OSPF routers on a network segment that is using
the OSPF simple password authentication, enter the following command:
hostname(config-interface)# ospf authentication-key key
The key can be any continuous string of characters up to 8 bytes in length.
The password created by this command is used as a key that is inserted directly into the OSPF header
when the security appliance software originates routing protocol packets. A separate password can
be assigned to each network on a per-interface basis. All neighboring routers on the same network
must have the same password to be able to exchange OSPF information.
•
To explicitly specify the cost of sending a packet on an OSPF interface, enter the following
command:
hostname(config-interface)# ospf cost cost
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The cost is an integer from 1 to 65535.
•
To set the number of seconds that a device must wait before it declares a neighbor OSPF router down
because it has not received a hello packet, enter the following command:
hostname(config-interface)# ospf dead-interval seconds
The value must be the same for all nodes on the network.
•
To specify the length of time between the hello packets that the security appliance sends on an OSPF
interface, enter the following command:
hostname(config-interface)# ospf hello-interval seconds
The value must be the same for all nodes on the network.
•
To enable OSPF MD5 authentication, enter the following command:
hostname(config-interface)# ospf message-digest-key key_id md5 key
Set the following values:
– key_id—An identifier in the range from 1 to 255.
– key—Alphanumeric password of up to 16 bytes.
Usually, one key per interface is used to generate authentication information when sending packets
and to authenticate incoming packets. The same key identifier on the neighbor router must have the
same key value.
We recommend that you not keep more than one key per interface. Every time you add a new key,
you should remove the old key to prevent the local system from continuing to communicate with a
hostile system that knows the old key. Removing the old key also reduces overhead during rollover.
•
To set the priority to help determine the OSPF designated router for a network, enter the following
command:
hostname(config-interface)# ospf priority number_value
The number_value is between 0 to 255.
•
To specify the number of seconds between LSA retransmissions for adjacencies belonging to an
OSPF interface, enter the following command:
hostname(config-interface)# ospf retransmit-interval seconds
The seconds must be greater than the expected round-trip delay between any two routers on the
attached network. The range is from 1 to 65535 seconds. The default is 5 seconds.
•
To set the estimated number of seconds required to send a link-state update packet on an OSPF
interface, enter the following command:
hostname(config-interface)# ospf transmit-delay seconds
The seconds is from 1 to 65535 seconds. The default is 1 second.
The following example shows how to configure the OSPF interfaces:
hostname(config)# router ospf 2
hostname(config-router)# network 2.0.0.0 255.0.0.0 area 0
hostname(config-router)# interface inside
hostname(config-interface)# ospf cost 20
hostname(config-interface)# ospf retransmit-interval 15
hostname(config-interface)# ospf transmit-delay 10
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hostname(config-interface)#
hostname(config-interface)#
hostname(config-interface)#
hostname(config-interface)#
hostname(config-interface)#
hostname(config-interface)#
ospf
ospf
ospf
ospf
ospf
ospf
priority 20
hello-interval 10
dead-interval 40
authentication-key cisco
message-digest-key 1 md5 cisco
authentication message-digest
The following is sample output from the show ospf command:
hostname(config)# show ospf
Routing Process "ospf 2" with ID 20.1.89.2 and Domain ID 0.0.0.2
Supports only single TOS(TOS0) routes
Supports opaque LSA
SPF schedule delay 5 secs, Hold time between two SPFs 10 secs
Minimum LSA interval 5 secs. Minimum LSA arrival 1 secs
Number of external LSA 5. Checksum Sum 0x 26da6
Number of opaque AS LSA 0. Checksum Sum 0x
0
Number of DCbitless external and opaque AS LSA 0
Number of DoNotAge external and opaque AS LSA 0
Number of areas in this router is 1. 1 normal 0 stub 0 nssa
External flood list length 0
Area BACKBONE(0)
Number of interfaces in this area is 1
Area has no authentication
SPF algorithm executed 2 times
Area ranges are
Number of LSA 5. Checksum Sum 0x 209a3
Number of opaque link LSA 0. Checksum Sum 0x
0
Number of DCbitless LSA 0
Number of indication LSA 0
Number of DoNotAge LSA 0
Flood list length 0
Configuring OSPF Area Parameters
You can configure several area parameters. These area parameters (shown in the following task table)
include setting authentication, defining stub areas, and assigning specific costs to the default summary
route. Authentication provides password-based protection against unauthorized access to an area.
Stub areas are areas into which information on external routes is not sent. Instead, there is a default
external route generated by the ABR, into the stub area for destinations outside the autonomous system.
To take advantage of the OSPF stub area support, default routing must be used in the stub area. To further
reduce the number of LSAs sent into a stub area, you can configure the no-summary keyword of the
area stub command on the ABR to prevent it from sending summary link advertisement (LSA type 3)
into the stub area.
To specify area parameters for your network, perform the following steps:
Step 1
If you have not already done so, enter the router configuration mode for the OSPF process you want to
configure by entering the following command:
hostname(config)# router ospf process_id
Step 2
Enter any of the following commands:
•
To enable authentication for an OSPF area, enter the following command:
hostname(config-router)# area area-id authentication
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•
To enable MD5 authentication for an OSPF area, enter the following command:
hostname(config-router)# area area-id authentication message-digest
•
To define an area to be a stub area, enter the following command:
hostname(config-router)# area area-id stub [no-summary]
•
To assign a specific cost to the default summary route used for the stub area, enter the following
command:
hostname(config-router)# area area-id default-cost cost
The cost is an integer from 1 to 65535. The default is 1.
The following example shows how to configure the OSPF area parameters:
hostname(config)# router
hostname(config-router)#
hostname(config-router)#
hostname(config-router)#
hostname(config-router)#
ospf
area
area
area
area
2
0 authentication
0 authentication message-digest
17 stub
17 default-cost 20
Configuring OSPF NSSA
The OSPF implementation of an NSSA is similar to an OSPF stub area. NSSA does not flood type 5
external LSAs from the core into the area, but it can import autonomous system external routes in a
limited way within the area.
NSSA imports type 7 autonomous system external routes within an NSSA area by redistribution. These
type 7 LSAs are translated into type 5 LSAs by NSSA ABRs, which are flooded throughout the whole
routing domain. Summarization and filtering are supported during the translation.
You can simplify administration if you are an ISP or a network administrator that must connect a central
site using OSPF to a remote site that is using a different routing protocol using NSSA.
Before the implementation of NSSA, the connection between the corporate site border router and the
remote router could not be run as an OSPF stub area because routes for the remote site could not be
redistributed into the stub area, and two routing protocols needed to be maintained. A simple protocol
such as RIP was usually run and handled the redistribution. With NSSA, you can extend OSPF to cover
the remote connection by defining the area between the corporate router and the remote router as an
NSSA.
To specify area parameters for your network as needed to configure OSPF NSSA, perform the following
steps:
Step 1
If you have not already done so, enter the router configuration mode for the OSPF process you want to
configure by entering the following command:
hostname(config)# router ospf process_id
Step 2
Enter any of the following commands:
•
To define an NSSA area, enter the following command:
hostname(config-router)# area area-id nssa [no-redistribution]
[default-information-originate]
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•
To summarize groups of addresses, enter the following command:
hostname(config-router)# summary address ip_address mask [not-advertise] [tag tag]
This command helps reduce the size of the routing table. Using this command for OSPF causes an
OSPF ASBR to advertise one external route as an aggregate for all redistributed routes that are
covered by the address.
OSPF does not support summary-address 0.0.0.0 0.0.0.0.
In the following example, the summary address 10.1.0.0 includes address 10.1.1.0, 10.1.2.0,
10.1.3.0, and so on. Only the address 10.1.0.0 is advertised in an external link-state advertisement:
hostname(config-router)# summary-address 10.1.1.0 255.255.0.0
Before you use this feature, consider these guidelines:
– You can set a type 7 default route that can be used to reach external destinations. When
configured, the router generates a type 7 default into the NSSA or the NSSA area boundary
router.
– Every router within the same area must agree that the area is NSSA; otherwise, the routers will
not be able to communicate.
Configuring Route Summarization Between OSPF Areas
Route summarization is the consolidation of advertised addresses. This feature causes a single summary
route to be advertised to other areas by an area boundary router. In OSPF, an area boundary router
advertises networks in one area into another area. If the network numbers in an area are assigned in a
way such that they are contiguous, you can configure the area boundary router to advertise a summary
route that covers all the individual networks within the area that fall into the specified range.
To define an address range for route summarization, perform the following steps:
Step 1
If you have not already done so, enter the router configuration mode for the OSPF process you want to
configure by entering the following command:
hostname(config)# router ospf process_id
Step 2
To set the address range, enter the following command:
hostname(config-router)# area area-id range ip-address mask [advertise | not-advertise]
The following example shows how to configure route summarization between OSPF areas:
hostname(config)# router ospf 1
hostname(config-router)# area 17 range 12.1.0.0 255.255.0.0
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Configuring Route Summarization When Redistributing Routes into OSPF
When routes from other protocols are redistributed into OSPF, each route is advertised individually in
an external LSA. However, you can configure the security appliance to advertise a single route for all
the redistributed routes that are covered by a specified network address and mask. This configuration
decreases the size of the OSPF link-state database.
To configure the software advertisement on one summary route for all redistributed routes covered by a
network address and mask, perform the following steps:
Step 1
If you have not already done so, enter the router configuration mode for the OSPF process you want to
configure by entering the following command:
hostname(config)# router ospf process_id
Step 2
To set the summary address, enter the following command:
hostname(config-router)# summary-address ip_address mask [not-advertise] [tag tag]
Note
OSPF does not support summary-address 0.0.0.0 0.0.0.0.
The following example shows how to configure route summarization. The summary address 10.1.0.0
includes address 10.1.1.0, 10.1.2.0, 10.1.3.0, and so on. Only the address 10.1.0.0 is advertised in an
external link-state advertisement:
hostname(config)# router ospf 1
hostname(config-router)# summary-address 10.1.0.0 255.255.0.0
Defining Static OSPF Neighbors
You need to define static OSPF neighbors to advertise OSPF routes over a point-to-point, non-broadcast
network. This lets you broadcast OSPF advertisements across an existing VPN connection without
having to encapsulate the advertisements in a GRE tunnel.
To define a static OSPF neighbor, perform the following tasks:
Step 1
Create a static route to the OSPF neighbor. See the “Configuring Static and Default Routes” section on
page 9-2 for more information about creating static routes.
Step 2
Define the OSPF neighbor by performing the following tasks:
a.
Enter router configuration mode for the OSPF process. Enter the following command:
hostname(config)# router ospf pid
b.
Define the OSPF neighbor by entering the following command:
hostname(config-router)# neighbor addr [interface if_name]
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The addr argument is the IP address of the OSPF neighbor. The if_name is the interface used to
communicate with the neighbor. If the OSPF neighbor is not on the same network as any of the
directly-connected interfaces, you must specify the interface.
Generating a Default Route
You can force an autonomous system boundary router to generate a default route into an OSPF routing
domain. Whenever you specifically configure redistribution of routes into an OSPF routing domain, the
router automatically becomes an autonomous system boundary router. However, an autonomous system
boundary router does not by default generate a default route into the OSPF routing domain.
To generate a default route, perform the following steps:
Step 1
If you have not already done so, enter the router configuration mode for the OSPF process you want to
configure by entering the following command:
hostname(config)# router ospf process_id
Step 2
To force the autonomous system boundary router to generate a default route, enter the following
command:
hostname(config-router)# default-information originate [always] [metric metric-value]
[metric-type {1 | 2}] [route-map map-name]
The following example shows how to generate a default route:
hostname(config)# router ospf 2
hostname(config-router)# default-information originate always
Configuring Route Calculation Timers
You can configure the delay time between when OSPF receives a topology change and when it starts an
SPF calculation. You also can configure the hold time between two consecutive SPF calculations.
To configure route calculation timers, perform the following steps:
Step 1
If you have not already done so, enter the router configuration mode for the OSPF process you want to
configure by entering the following command:
hostname(config)# router ospf process_id
Step 2
To configure the route calculation time, enter the following command:
hostname(config-router)# timers spf spf-delay spf-holdtime
The spf-delay is the delay time (in seconds) between when OSPF receives a topology change and when
it starts an SPF calculation. It can be an integer from 0 to 65535. The default time is 5 seconds. A value
of 0 means that there is no delay; that is, the SPF calculation is started immediately.
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The spf-holdtime is the minimum time (in seconds) between two consecutive SPF calculations. It can be
an integer from 0 to 65535. The default time is 10 seconds. A value of 0 means that there is no delay;
that is, two SPF calculations can be done, one immediately after the other.
The following example shows how to configure route calculation timers:
hostname(config)# router ospf 1
hostname(config-router)# timers spf 10 120
Logging Neighbors Going Up or Down
By default, the system sends a system message when an OSPF neighbor goes up or down.
Configure this command if you want to know about OSPF neighbors going up or down without turning
on the debug ospf adjacency command. The log-adj-changes router configuration command provides
a higher level view of the peer relationship with less output. Configure log-adj-changes detail if you
want to see messages for each state change.
To log neighbors going up or down, perform the following steps:
Step 1
If you have not already done so, enter the router configuration mode for the OSPF process you want to
configure by entering the following command:
hostname(config)# router ospf process_id
Step 2
To configure logging for neighbors going up or down, enter the following command:
hostname(config-router)# log-adj-changes [detail]
Note
Logging must be enabled for the the neighbor up/down messages to be sent.
The following example shows how to log neighbors up/down messages:
hostname(config)# router ospf 1
hostname(config-router)# log-adj-changes detail
Displaying OSPF Update Packet Pacing
OSPF update packets are automatically paced so they are not sent less than 33 milliseconds apart.
Without pacing, some update packets could get lost in situations where the link is slow, a neighbor could
not receive the updates quickly enough, or the router could run out of buffer space. For example, without
pacing packets might be dropped if either of the following topologies exist:
•
A fast router is connected to a slower router over a point-to-point link.
•
During flooding, several neighbors send updates to a single router at the same time.
Pacing is also used between resends to increase efficiency and minimize lost retransmissions. You also
can display the LSAs waiting to be sent out an interface. The benefit of the pacing is that OSPF update
and retransmission packets are sent more efficiently.
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There are no configuration tasks for this feature; it occurs automatically.
To observe OSPF packet pacing by displaying a list of LSAs waiting to be flooded over a specified
interface, enter the following command:
hostname# show ospf flood-list if_name
Monitoring OSPF
You can display specific statistics such as the contents of IP routing tables, caches, and databases. You
can use the information provided to determine resource utilization and solve network problems. You can
also display information about node reachability and discover the routing path that your device packets
are taking through the network.
To display various OSPF routing statistics, perform one of the following tasks, as needed:
•
To display general information about OSPF routing processes, enter the following command:
hostname# show ospf [process-id [area-id]]
•
To display the internal OSPF routing table entries to the ABR and ASBR, enter the following
command:
hostname# show ospf border-routers
•
To display lists of information related to the OSPF database for a specific router, enter the following
command:
hostname# show ospf [process-id [area-id]] database
•
To display a list of LSAs waiting to be flooded over an interface (to observe OSPF packet pacing),
enter the following command:
hostname# show ospf flood-list if-name
•
To display OSPF-related interface information, enter the following command:
hostname# show ospf interface [if_name]
•
To display OSPF neighbor information on a per-interface basis, enter the following command:
hostname# show ospf neighbor [interface-name] [neighbor-id] [detail]
•
To display a list of all LSAs requested by a router, enter the following command:
hostname# show ospf request-list neighbor if_name
•
To display a list of all LSAs waiting to be resent, enter the following command:
hostname# show ospf retransmission-list neighbor if_name
•
To display a list of all summary address redistribution information configured under an OSPF
process, enter the following command:
hostname# show ospf [process-id] summary-address
•
To display OSPF-related virtual links information, enter the following command:
hostname# show ospf [process-id] virtual-links
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Restarting the OSPF Process
To restart an OSPF process, clear redistribution, or counters, enter the following command:
hostname(config)# clear ospf pid {process | redistribution | counters
[neighbor [neighbor-interface] [neighbor-id]]}
Configuring RIP
Devices that support RIP send routing-update messages at regular intervals and when the network
topology changes. These RIP packets contain information about the networks that the devices can reach,
as well as the number of routers or gateways that a packet must travel through to reach the destination
address. RIP generates more traffic than OSPF, but is easier to configure.
RIP has advantages over static routes because the initial configuration is simple, and you do not need to
update the configuration when the topology changes. The disadvantage to RIP is that there is more
network and processing overhead than static routing.
The security appliance supports RIP Version 1 and RIP Version 2.
This section describes how to configure RIP. This section includes the following topics:
•
Enabling and Configuring RIP, page 9-20
•
Redistributing Routes into the RIP Routing Process, page 9-21
•
Configuring RIP Send/Receive Version on an Interface, page 9-22
•
Enabling RIP Authentication, page 9-23
•
Monitoring RIP, page 9-23
Enabling and Configuring RIP
You can only enable one RIP routing process on the security appliance. After you enable the RIP routing
process, you must define the interfaces that will participate in that routing process using the network
command. By default, the security appliance sends RIP Version 1 updates and accepts RIP Version 1 and
Version 2 updates.
To enable and configure the RIP routing process, perform the following steps:
Step 1
Start the RIP routing process by entering the following command in global configuration mode:
hostname(config): router rip
You enter router configuration mode for the RIP routing process.
Step 2
Specify the interfaces that will participate in the RIP routing process. Enter the following command for
each interface that will participate in the RIP routing process:
hostname(config-router): network network_address
If an interface belongs to a network defined by this command, the interface will participate in the RIP
routing process. If an interface does not belong to a network defined by this command, it will not send
or receive RIP updates.
Step 3
(Optional) Specify the version of RIP used by the security appliance by entering the following command:
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hostname(config-router): version [1 | 2]
You can override this setting on a per-interface basis.
Step 4
(Optional) To generate a default route into RIP, enter the following command:
hostname(config-router): default-information originate
Step 5
(Optional) To specify an interface to operate in passive mode, enter the following command:
hostname(config-router): passive-interface [default | if_name]
Using the default keyword causes all interfaces to operate in passive mode. Specifying an interface name
sets only that interface to passive RIP mode. In passive mode, RIP routing updates are accepted by but
not sent out of the specified interface. You can enter this command for each interface you want to set to
passive mode.
Step 6
(Optional) Disable automatic route summarization by entering the following command:
hostname(config-router): no auto-summarize
RIP Version 1 always uses automatic route summarization; you cannot disable it for RIP Version 1. RIP
Version 2 uses route summarization by default; you can disable it using this command.
Step 7
(Optional) To filter the networks received in updates, perform the following steps:
a.
Create a standard access list permitting the networks you want the RIP process to allow in the
routing table and denying the networks you want the RIP process to discard.
b.
Enter the following command to apply the filter. You can specify an interface to apply the filter to
only those updates received by that interface.
hostname(config-router): distribute-list acl in [interface if_name]
You can enter this command for each interface you want to apply a filter to. If you do not specify an
interface name, the filter is applied to all RIP updates.
Step 8
(Optional) To filter the networks sent in updates, perform the following steps:
a.
Create a standard access list permitting the networks you want the RIP process to advertise and
denying the networks you do not want the RIP process to advertise.
b.
Enter the following command to apply the filter. You can specify an interface to apply the filter to
only those updates sent by that interface.
hostname(config-router): distribute-list acl out [interface if_name]
You can enter this command for each interface you want to apply a filter to. If you do not specify an
interface name, the filter is applied to all RIP updates.
Redistributing Routes into the RIP Routing Process
You can redistribute routes from the OSPF, static, and connected routing processes into the RIP routing
process.
To redistribute a routes into the RIP routing process, perform the following steps:
Step 1
(Optional) Create a route-map to further define which routes from the specified routing protocol are
redistributed in to the RIP routing process. See the “Defining Route Maps” section on page 9-7 for more
information about creating a route map.
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Step 2
Choose one of the following options to redistribute the selected route type into the RIP routing process.
•
To redistribute connected routes into the RIP routing process, enter the following command:
hostname(config-router): redistribute connected [metric {metric_value | transparent}]
[route-map map_name]
•
To redistribute static routes into the RIP routing process, enter the following command:
hostname(config-router): redistribute static [metric {metric_value | transparent}]
[route-map map_name]
•
To redistribute routes from an OSPF routing process into the RIP routing process, enter the
following command:
hostname(config-router): redistribute ospf pid [match {internal | external [1 | 2] |
nssa-external [1 | 2]}] [metric {metric_value | transparent}] [route-map map_name]
Configuring RIP Send/Receive Version on an Interface
You can override the globally-set version of RIP the security appliance uses to send and receive RIP
updates on a per-interface basis.
To configure the RIP send and receive
Step 1
(Optional) To specify the version of RIP advertisements sent from an interface, perform the following
steps:
a.
Enter interface configuration mode for the interface you are configuring by entering the following
command:
hostname(config)# interface phy_if
b.
Specify the version of RIP to use when sending RIP updates out of the interface by entering the
following command:
hostname(config-if)# rip send version {[1] [2]}
Step 2
(Optional) To specify the version of RIP advertisements permitted to be received by an interface,
perform the following steps:
a.
Enter interface configuration mode for the interface you are configuring by entering the following
command:
hostname(config)# interface phy_if
b.
Specify the version of RIP to allow when receiving RIP updates on the interface by entering the
following command:
hostname(config-if)# rip receive version {[1] [2]}
RIP updates received on the interface that do not match the allowed version are dropped.
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Configuring IP Routing
The Routing Table
Enabling RIP Authentication
The security appliance supports RIP message authentication for RIP Version 2 messages.
To enable RIP message authentication, perform the following steps:
Step 1
Enter interface configuration mode for the interface you are configuring by entering the following
command:
hostname(config)# interface phy_if
Step 2
(Optional) Set the authentication mode by entering the following command. By default, text
authentication is used. MD5 authentication is recommended.
hostname(config-if)# rip authentication mode {text | md5}
Step 3
Enable authentication and configure the authentication key by entering the following command:
hostname(config-if)# rip authentication key key key_id key-id
Monitoring RIP
To display various RIP routing statistics, perform one of the following tasks, as needed:
•
To display the contents of the RIP routing database, enter the following command:
hostname# show rip database
•
To display the RIP commands in the running configuration, enter the following command:
hostname# show running-config router rip
Use the following debug commands only to troubleshoot specific problems or during troubleshooting
sessions with Cisco TAC. Debugging output is assigned high priority in the CPU process and can render
the system unusable. It is best to use debug commands during periods of lower network traffic and fewer
users. Debugging during these periods decreases the likelihood that increased debug command
processing overhead will affect system performance.
•
To display RIP processing events, enter the following command:
hostname# debug rip events
•
To display RIP database events, enter the following command:
hostname# debug rip database
The Routing Table
This section contains the following topics:
•
Displaying the Routing Table, page 9-24
•
How the Routing Table is Populated, page 9-24
•
How Forwarding Decisions are Made, page 9-26
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The Routing Table
Displaying the Routing Table
To view the entries in the routing table, enter the following command:
hostname# show route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is 10.86.194.1 to network 0.0.0.0
S
C
S*
10.1.1.0 255.255.255.0 [3/0] via 10.86.194.1, outside
10.86.194.0 255.255.254.0 is directly connected, outside
0.0.0.0 0.0.0.0 [1/0] via 10.86.194.1, outside
On the ASA 5505 adaptive security appliance, the following route is also shown. It is the internal
loopback interface, which is used by the VPN Hardware Client feature for individual user authentication.
C 127.1.0.0 255.255.0.0 is directly connected, _internal_loopback
How the Routing Table is Populated
The security appliance routing table can be populated by statically defined routes, directly connected
routes, and routes discovered by the RIP and OSPF routing protocols. Because the security appliance
can run multiple routing protocols in addition to having static and connected routed in the routing table,
it is possible that the same route is discovered or entered in more than one manner. When two routes to
the same destination are put into the routing table, the one that remains in the routing table is determined
as follows:
•
If the two routes have different network prefix lengths (network masks), then both routes are
considered unique and are entered in to the routing table. The packet forwarding logic then
determines which of the two to use.
For example, if the RIP and OSPF processes discovered the following routes:
– RIP: 192.168.32.0/24
– OSPF: 192.168.32.0/19
Even though OSPF routes have the better administrative distance, both routes are installed in the
routing table because each of these routes has a different prefix length (subnet mask). They are
considered different destinations and the packet forwarding logic determine which route to use.
•
If the security appliance learns about multiple paths to the same destination from a single routing
protocol, such as RIP, the route with the better metric (as determined by the routing protocol) is
entered into the routing table.
Metrics are values associated with specific routes, ranking them from most preferred to least
preferred. The parameters used to determine the metrics differ for different routing protocols. The
path with the lowest metric is selected as the optimal path and installed in the routing table. If there
are multiple paths to the same destination with equal metrics, load balancing is done on these equal
cost paths.
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The Routing Table
•
If the security appliance learns about a destination from more than one routing protocol, the
administrative distances of the routes are compared and the routes with lower administrative
distance is entered into the routing table.
Administrative distance is a route parameter that security appliance uses to select the best path when
there are two or more different routes to the same destination from two different routing protocols.
Because the routing protocols have metrics based on algorithms that are different from the other
protocols, it is not always possible to determine the “best path” for two routes to the same destination
that were generated by different routing protocols.
Each routing protocol is prioritized using an administrative distance value. Table 9-1 shows the default
administrative distance values for the routing protocols supported by the security appliance.
Table 9-1
Default Administrative Distance for Supported Routing Protocols
Route Source
Default Administrative Distance
Connected interface
0
Static route
1
OSPF
110
RIP
120
The smaller the administrative distance value, the more preference is given to the protocol. For example,
if the security appliance receives a route to a certain network from both an OSPF routing process (default
administrative distance - 110) and a RIP routing process (default administrative distance - 100), the
security appliance chooses the OSPF route because OSPF has a higher preference. This means the router
adds the OSPF version of the route to the routing table.
In the above example, if the source of the OSPF-derived route was lost (for example, due to a power
shutdown), the security appliance would then use the RIP-derived route until the OSPF-derived route
reappears.
The administrative distance is a local setting. For example, if you use the distance-ospf command to
change the administrative distance of routes obtained through OSPF, that change would only affect the
routing table for the security appliance the command was entered on. The administrative distance is not
advertised in routing updates.
Administrative distance does not affect the routing process. The OSPF and RIP routing processes only
advertise the routes that have been discovered by the routing process or redistributed into the routing
process. For example, the RIP routing process advertises RIP routes, even if routes discovered by the
OSPF routing process are used in the security appliance routing table.
Backup Routes
A backup route is registered when the initial attempt to install the route in the routing table fails because
another route was installed instead. If the route that was installed in the routing table fails, the routing
table maintenance process calls each routing protocol process that has registered a backup route and
requests them to reinstall the route in the routing table. If there are multiple protocols with registered
backup routes for the failed route, the preferred route is chosen based on administrative distance.
Because of this process, you can create “floating” static routes that are installed in the routing table when
the route discovered by a dynamic routing protocol fails. A floating static route is simply a static route
configured with a greater administrative distance than the dynamic routing protocols running on the
security appliance. When the corresponding route discover by a dynamic routing process fails, the static
route is installed in the routing table.
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Dynamic Routing and Failover
How Forwarding Decisions are Made
Forwarding decisions are made as follows:
•
If the destination does not match an entry in the routing table, the packet is forwarded through the
interface specified for the default route. If a default route has not been configured, the packet is
discarded.
•
If the destination matches a single entry in the routing table, the packet is forwarded through the
interface associated with that route.
•
If the destination matches more than one entry in the routing table, and the entries all have the same
network prefix length, the packets for that destination are distributed among the interfaces
associated with that route.
•
If the destination matches more than one entry in the routing table, and the entries have different
network prefix lengths, then the packet is forwarded out of the interface associated with the route
that has the longer network prefix length.
For example, a packet destined for 192.168.32.1 arrives on an interface of a security appliance with the
following routes in the routing table:
hostname# show route
....
R
192.168.32.0/24 [120/4] via 10.1.1.2
O
192.168.32.0/19 [110/229840] via 10.1.1.3
....
In this case, a packet destined to 192.168.32.1 is directed toward 10.1.1.2, because 192.168.32.1 falls
within the 192.168.32.0/24 network. It also falls within the other route in the routing table, but the
192.168.32.0/24 has the longest prefix within the routing table (24 bits verses 19 bits). Longer prefixes
are always preferred over shorter ones when forwarding a packet.
Dynamic Routing and Failover
Dynamic routes are not replicated to the standby unit or failover group in a failover configuration.
Therefore, immediately after a failover occurs, some packets received by the security appliance may be
dropped because of a lack of routing information or routed to a default static route while the routing table
is repopulated by the configured dynamic routing protocols.
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10
Configuring DHCP, DDNS, and WCCP Services
This chapter describes how to configure the DHCP server, dynamic DNS (DDNS) update methods, and
WCCP on the security appliance. DHCP provides network configuration parameters, such as IP
addresses, to DHCP clients. The security appliance can provide a DHCP server or DHCP relay services
to DHCP clients attached to security appliance interfaces. The DHCP server provides network
configuration parameters directly to DHCP clients. DHCP relay passes DHCP requests received on one
interface to an external DHCP server located behind a different interface.
DDNS update integrates DNS with DHCP. The two protocols are complementary: DHCP centralizes and
automates IP address allocation; DDNS update automatically records the association between assigned
addresses and hostnames at pre-defined intervals. DDNS allows frequently changing address-hostname
associations to be updated frequently. Mobile hosts, for example, can then move freely on a network
without user or administrator intervention. DDNS provides the necessary dynamic updating and
synchronizing of the name to address and address to name mappings on the DNS server.
WCCP specifies interactions between one or more routers, Layer 3 switches, or security appliances and
one or more web caches. The feature transparently redirects selected types of traffic to a group of web
cache engines to optimize resource usage and lower response times.
This chapter includes the following sections:
•
Configuring a DHCP Server, page 10-1
•
Configuring DHCP Relay Services, page 10-5
•
Configuring Dynamic DNS, page 10-6
•
Configuring Web Cache Services Using WCCP, page 10-9
Configuring a DHCP Server
This section describes how to configure DHCP server provided by the security appliance. This section
includes the following topics:
•
Enabling the DHCP Server, page 10-2
•
Configuring DHCP Options, page 10-3
•
Using Cisco IP Phones with a DHCP Server, page 10-4
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Configuring a DHCP Server
Enabling the DHCP Server
The security appliance can act as a DHCP server. DHCP is a protocol that supplies network settings to
hosts including the host IP address, the default gateway, and a DNS server.
Note
The security appliance DHCP server does not support BOOTP requests.
In multiple context mode, you cannot enable the DHCP server or DHCP relay on an interface that is used
by more than one context.
You can configure a DHCP server on each interface of the security appliance. Each interface can have
its own pool of addresses to draw from. However the other DHCP settings, such as DNS servers, domain
name, options, ping timeout, and WINS servers, are configured globally and used by the DHCP server
on all interfaces.
You cannot configure a DHCP client or DHCP Relay services on an interface on which the server is
enabled. Additionally, DHCP clients must be directly connected to the interface on which the server is
enabled.
To enable the DHCP server on a given security appliance interface, perform the following steps:
Step 1
Create a DHCP address pool. Enter the following command to define the address pool:
hostname(config)# dhcpd address ip_address-ip_address interface_name
The security appliance assigns a client one of the addresses from this pool to use for a given length of time.
These addresses are the local, untranslated addresses for the directly connected network.
The address pool must be on the same subnet as the security appliance interface.
Step 2
(Optional) To specify the IP address(es) of the DNS server(s) the client will use, enter the following
command:
hostname(config)# dhcpd dns dns1 [dns2]
You can specify up to two DNS servers.
Step 3
(Optional) To specify the IP address(es) of the WINS server(s) the client will use, enter the following
command:
hostname(config)# dhcpd wins wins1 [wins2]
You can specify up to two WINS servers.
Step 4
(Optional) To change the lease length to be granted to the client, enter the following command:
hostname(config)# dhcpd lease lease_length
This lease equals the amount of time (in seconds) the client can use its allocated IP address before the
lease expires. Enter a value between 0 to 1,048,575. The default value is 3600 seconds.
Step 5
(Optional) To configure the domain name the client uses, enter the following command:
hostname(config)# dhcpd domain domain_name
Step 6
(Optional) To configure the DHCP ping timeout value, enter the following command:
hostname(config)# dhcpd ping_timeout milliseconds
To avoid address conflicts, the security appliance sends two ICMP ping packets to an address before
assigning that address to a DHCP client. This command specifies the timeout value for those packets.
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Configuring a DHCP Server
Step 7
(Transparent Firewall Mode) Define a default gateway. To define the default gateway that is sent to
DHCP clients, enter the following command.
hostname(config)# dhcpd option 3 ip gateway_ip
If you do not use the DHCP option 3 to define the default gateway, DHCP clients use the IP address of
the management interface. The management interface does not route traffic.
Step 8
To enable the DHCP daemon within the security appliance to listen for DHCP client requests on the
enabled interface, enter the following command:
hostname(config)# dhcpd enable interface_name
For example, to assign the range 10.0.1.101 to 10.0.1.110 to hosts connected to the inside interface, enter
the following commands:
hostname(config)#
hostname(config)#
hostname(config)#
hostname(config)#
hostname(config)#
hostname(config)#
dhcpd
dhcpd
dhcpd
dhcpd
dhcpd
dhcpd
address 10.0.1.101-10.0.1.110 inside
dns 209.165.201.2 209.165.202.129
wins 209.165.201.5
lease 3000
domain example.com
enable inside
Configuring DHCP Options
You can configure the security appliance to send information for the DHCP options listed in RFC 2132.
The DHCP options fall into one of three categories:
•
Options that return an IP address.
•
Options that return a text string.
•
Options that return a hexadecimal value.
The security appliance supports all three categories of DHCP options. To configure a DHCP option, do
one of the following:
•
To configure a DHCP option that returns one or two IP addresses, enter the following command:
hostname(config)# dhcpd option code ip addr_1 [addr_2]
•
To configure a DHCP option that returns a text string, enter the following command:
hostname(config)# dhcpd option code ascii text
•
To configure a DHCP option that returns a hexadecimal value, enter the following command:
hostname(config)# dhcpd option code hex value
Note
The security appliance does not verify that the option type and value that you provide match the expected
type and value for the option code as defined in RFC 2132. For example, you can enter the dhcpd option
46 ascii hello command and the security appliance accepts the configuration although option 46 is
defined in RFC 2132 as expecting a single-digit, hexadecimal value. For more information about the
option codes and their associated types and expected values, refer to RFC 2132.
Table 10-1 shows the DHCP options that are not supported by the dhcpd option command.
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Configuring a DHCP Server
Table 10-1
Unsupported DHCP Options
Option Code
Description
0
DHCPOPT_PAD
1
HCPOPT_SUBNET_MASK
12
DHCPOPT_HOST_NAME
50
DHCPOPT_REQUESTED_ADDRESS
51
DHCPOPT_LEASE_TIME
52
DHCPOPT_OPTION_OVERLOAD
53
DHCPOPT_MESSAGE_TYPE
54
DHCPOPT_SERVER_IDENTIFIER
58
DHCPOPT_RENEWAL_TIME
59
DHCPOPT_REBINDING_TIME
61
DHCPOPT_CLIENT_IDENTIFIER
67
DHCPOPT_BOOT_FILE_NAME
82
DHCPOPT_RELAY_INFORMATION
255
DHCPOPT_END
Specific options, DHCP option 3, 66, and 150, are used to configure Cisco IP Phones. See the “Using
Cisco IP Phones with a DHCP Server” section on page 10-4 topic for more information about
configuring those options.
Using Cisco IP Phones with a DHCP Server
Enterprises with small branch offices that implement a Cisco IP Telephony Voice over IP solution
typically implement Cisco CallManager at a central office to control Cisco IP Phones at small branch
offices. This implementation allows centralized call processing, reduces the equipment required, and
eliminates the administration of additional Cisco CallManager and other servers at branch offices.
Cisco IP Phones download their configuration from a TFTP server. When a Cisco IP Phone starts, if it
does not have both the IP address and TFTP server IP address preconfigured, it sends a request with
option 150 or 66 to the DHCP server to obtain this information.
•
DHCP option 150 provides the IP addresses of a list of TFTP servers.
•
DHCP option 66 gives the IP address or the hostname of a single TFTP server.
Cisco IP Phones might also include DHCP option 3 in their requests, which sets the default route.
Cisco IP Phones might include both option 150 and 66 in a single request. In this case, the security
appliance DHCP server provides values for both options in the response if they are configured on the
security appliance.
You can configure the security appliance to send information for most options listed in RFC 2132. The
following example shows the syntax for any option number, as well as the syntax for commonly-used
options 66, 150, and 3:
•
To provide information for DHCP requests that include an option number as specified in RFC-2132,
enter the following command:
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Configuring DHCP Relay Services
hostname(config)# dhcpd option number value
•
To provide the IP address or name of a TFTP server for option 66, enter the following command:
hostname(config)# dhcpd option 66 ascii server_name
•
To provide the IP address or names of one or two TFTP servers for option 150, enter the following
command:
hostname(config)# dhcpd option 150 ip server_ip1 [server_ip2]
The server_ip1 is the IP address or name of the primary TFTP server while server_ip2 is the
IP address or name of the secondary TFTP server. A maximum of two TFTP servers can be
identified using option 150.
•
To set the default route, enter the following command:
hostname(config)# dhcpd option 3 ip router_ip1
Configuring DHCP Relay Services
A DHCP relay agent allows the security appliance to forward DHCP requests from clients to a router
connected to a different interface.
The following restrictions apply to the use of the DHCP relay agent:
•
The relay agent cannot be enabled if the DHCP server feature is also enabled.
•
Clients must be directly connected to the security appliance and cannot send requests through
another relay agent or a router.
•
For multiple context mode, you cannot enable DHCP relay on an interface that is used by more than
one context.
Note
DHCP Relay services are not available in transparent firewall mode. A security appliance in transparent
firewall mode only allows ARP traffic through; all other traffic requires an access list. To allow DHCP
requests and replies through the security appliance in transparent mode, you need to configure two
access lists, one that allows DCHP requests from the inside interface to the outside, and one that allows
the replies from the server in the other direction.
Note
When DHCP relay is enabled and more than one DHCP relay server is defined, the security appliance
forwards client requests to each defined DHCP relay server. Replies from the servers are also forwarded
to the client until the client DHCP relay binding is removed. The binding is removed when the security
appliance receives any of the following DHCP messages: ACK, NACK, or decline.
To enable DHCP relay, perform the following steps:
Step 1
To set the IP address of a DHCP server on a different interface from the DHCP client, enter the following
command:
hostname(config)# dhcprelay server ip_address if_name
You can use this command up to 4 times to identify up to 4 servers.
Step 2
To enable DHCP relay on the interface connected to the clients, enter the following command:
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Configuring Dynamic DNS
hostname(config)# dhcprelay enable interface
Step 3
(Optional) To set the number of seconds allowed for relay address negotiation, enter the following
command:
hostname(config)# dhcprelay timeout seconds
Step 4
(Optional) To change the first default router address in the packet sent from the DHCP server to the
address of the security appliance interface, enter the following command:
hostname(config)# dhcprelay setroute interface_name
This action allows the client to set its default route to point to the security appliance even if the DHCP
server specifies a different router.
If there is no default router option in the packet, the security appliance adds one containing the interface
address.
The following example enables the security appliance to forward DHCP requests from clients connected
to the inside interface to a DHCP server on the outside interface:
hostname(config)# dhcprelay server 201.168.200.4
hostname(config)# dhcprelay enable inside
hostname(config)# dhcprelay setroute inside
Configuring Dynamic DNS
This section describes examples for configuring the security appliance to support Dynamic DNS. DDNS
update integrates DNS with DHCP. The two protocols are complementary—DHCP centralizes and
automates IP address allocation, while dynamic DNS update automatically records the association
between assigned addresses and hostnames. When you use DHCP and dynamic DNS update, this
configures a host automatically for network access whenever it attaches to the IP network. You can locate
and reach the host using its permanent, unique DNS hostname. Mobile hosts, for example, can move
freely without user or administrator intervention.
DDNS provides address and domain name mappings so hosts can find each other even though their
DHCP-assigned IP addresses change frequently. The DDNS name and address mappings are held on the
DHCP server in two resource records: the A RR contains the name to IP address mapping while the PTR
RR maps addresses to names. Of the two methods for performing DDNS updates—the IETF standard
defined by RFC 2136 and a generic HTTP method—the security appliance supports the IETF method in
this release.
The two most common DDNS update configurations are:
•
The DHCP client updates the A RR while the DHCP server updates PTR RR.
•
The DHCP server updates both the A and PTR RRs.
In general, the DHCP server maintains DNS PTR RRs on behalf of clients. Clients may be configured
to perform all desired DNS updates. The server may be configured to honor these updates or not. To
update the PTR RR, the DHCP server must know the Fully Qualified Domain Name of the client. The
client provides an FQDN to the server using a DHCP option called Client FQDN.
The following examples present these common scenarios:
•
Example 1: Client Updates Both A and PTR RRs for Static IP Addresses, page 10-7
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•
Example 2: Client Updates Both A and PTR RRs; DHCP Server Honors Client Update Request;
FQDN Provided Through Configuration, page 10-7
•
Example 3: Client Includes FQDN Option Instructing Server Not to Update Either RR; Server
Overrides Client and Updates Both RRs., page 10-8
•
Example 4: Client Asks Server To Perform Both Updates; Server Configured to Update PTR RR
Only; Honors Client Request and Updates Both A and PTR RR, page 10-8
•
Example 5: Client Updates A RR; Server Updates PTR RR, page 10-9
Example 1: Client Updates Both A and PTR RRs for Static IP Addresses
The following example configures the client to request that it update both A and PTR resource records
for static IP addresses. To configure this example, perform the following steps:
Step 1
To define a DDNS update method called ddns-2 that requests that the client update both the A and PTR
RRs, enter the following commands:
hostname(config)# ddns update method ddns-2
hostname(DDNS-update-method)# ddns both
Step 2
To associate the method ddns-2 with the eth1 interface, enter the following commands:
hostname(DDNS-update-method)# interface eth1
hostname(config-if)# ddns update ddns-2
hostname(config-if)# ddns update hostname asa.example.com
Step 3
To configure a static IP address for eth1, enter the following commands:
hostname(config-if)# ip address 10.0.0.40 255.255.255.0
Example 2: Client Updates Both A and PTR RRs; DHCP Server Honors Client
Update Request; FQDN Provided Through Configuration
The following example configures 1) the DHCP client to request that it update both the A and PTR RRs,
and 2) the DHCP server to honor the requests. To configure this example, perform the following steps:
Step 1
To configure the DHCP client to request that the DHCP server perform no updates, enter the following
command:
hostname(config)# dhcp-client update dns server none
Step 2
To create a DDNS update method named ddns-2 on the DHCP client that requests that the client perform
both A and PTR updates, enter the following commands:
hostname(config)# ddns update method ddns-2
hostname(DDNS-update-method)# ddns both
Step 3
To associate the method named ddns-2 with the security appliance interface named Ethernet0, and enable
DHCP on the interface, enter the following commands:
hostname(DDNS-update-method)# interface Ethernet0
hostname(if-config)# ddns update ddns-2
hostname(if-config)# ddns update hostname asa.example.com
hostname(if-config)# ip address dhcp
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Configuring Dynamic DNS
Step 4
To configure the DHCP server, enter the following command:
hostname(if-config)# dhcpd update dns
Example 3: Client Includes FQDN Option Instructing Server Not to Update Either
RR; Server Overrides Client and Updates Both RRs.
The following example configures the DHCP client to include the FQDN option instructing the DHCP
server not to update either the A or PTR updates. The example also configures the server to override the
client request. As a result, the client backs off without performing any updates.
To configure this scenario, perform the following steps:
Step 1
To configure the update method named ddns-2 to request that it make both A and PTR RR updates, enter
the following commands:
hostname(config)# ddns update method ddns-2
hostname(DDNS-update-method)# ddns both
Step 2
To assign the DDNS update method named ddns-2 on interface Ethernet0 and provide the client
hostname (asa), enter the following commands:
hostname(DDNS-update-method)# interface Ethernet0
hostname(if-config)# ddns update ddns-2
hostname(if-config)# ddns update hostname asa.example.com
Step 3
To enable the DHCP client feature on the interface, enter the following commands:
hostname(if-config)# dhcp client update dns server none
hostname(if-config)# ip address dhcp
Step 4
To configure the DHCP server to override the client update requests, enter the following command:
hostname(if-config)# dhcpd update dns both override
Example 4: Client Asks Server To Perform Both Updates; Server Configured to
Update PTR RR Only; Honors Client Request and Updates Both A and PTR RR
The following example configures the server to perform only PTR RR updates by default. However, the
server honors the client request that it perform both A and PTR updates. The server also forms the FQDN
by appending the domain name (example.com) to the hostname provided by the client (asa).
To configure this scenario, perform the following steps:
Step 1
To configure the DHCP client on interface Ethernet0, enter the following commands:
hostname(config)# interface Ethernet0
hostname(config-if)# dhcp client update dns both
hostname(config-if)# ddns update hostname asa
Step 2
To configure the DHCP server, enter the following commands:
hostname(config-if)# dhcpd update dns
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Configuring Web Cache Services Using WCCP
hostname(config-if)# dhcpd domain example.com
Example 5: Client Updates A RR; Server Updates PTR RR
The following example configures the client to update the A resource record and the server to update the
PTR records. Also, the client uses the domain name from the DHCP server to form the FQDN.
To configure this scenario, perform the following steps:
Step 1
To define the DDNS update method named ddns-2, enter the following commands:
hostname(config)# ddns update method ddns-2
hostname(DDNS-update-method)# ddns
Step 2
To configure the DHCP client for interface Ethernet0 and assign the update method to the interface, enter
the following commands:
hostname(DDNS-update-method)# interface Ethernet0
hostname(config-if)# dhcp client update dns
hostname(config-if)# ddns update ddns-2
hostname(config-if)# ddns update hostname asa
Step 3
To configure the DHCP server, enter the following commands:
hostname(config-if)# dhcpd update dns
hostname(config-if)# dhcpd domain example.com
Configuring Web Cache Services Using WCCP
The purpose of web caching is to reduce latency and network traffic. Previously-accessed web pages are
stored in a cache buffer, so if a user needs the page again, they can retrieve it from the cache instead of
the web server.
WCCP specifies interactions between the security appliance and external web caches. The feature
transparently redirects selected types of traffic to a group of web cache engines to optimize resource
usage and lower response times. The security appliance only supports WCCP version 2.
Using a security appliance as an intermediary eliminates the need for a separate router to do the WCCP
redirect because the security appliance takes care of redirecting requests to cache engines. When the
security appliance knows when a packet needs redirection, it skips TCP state tracking, TCP sequence
number randomization, and NAT on these traffic flows.
This section includes the following topics:
•
WCCP Feature Support, page 10-9
•
WCCP Interaction With Other Features, page 10-10
•
Enabling WCCP Redirection, page 10-10
WCCP Feature Support
The following WCCPv2 features are supported with the security appliance:
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Configuring Web Cache Services Using WCCP
•
Redirection of multiple TCP/UDP port-destined traffic.
•
Authentication for cache engines in a service group.
The following WCCPv2 features are not supported with the security appliance:
•
Multiple routers in a service group is not supported. Multiple Cache Engines in a service group is
still supported.
•
Multicast WCCP is not supported.
•
The Layer 2 redirect method is not supported; only GRE encapsulation is supported.
•
WCCP source address spoofing.
WCCP Interaction With Other Features
In the security appliance implementation of WCCP, the following applies as to how the protocol interacts
with other configurable features:
•
An ingress access list entry always takes higher priority over WCCP. For example, if an access list
does not permit a client to communicate with a server then traffic will not be redirected to a cache
engine. Both ingress interface access lists and egress interface access lists will be applied.
•
TCP intercept, authorization, URL filtering, inspect engines, and IPS features are not applied to a
redirected flow of traffic.
•
When a cache engine cannot service a request and packet is returned, or when a cache miss happens
on a cache engine and it requests data from a web server, then the contents of the traffic flow will
be subject to all the other configured features of the security appliance.
•
In failover, WCCP redirect tables are not replicated to standby units. After a failover, packets will
not be redirected until the tables are rebuilt. Sessions redirected prior to failover will likely be reset
by the web server.
Enabling WCCP Redirection
There are two steps to configuring WCCP redirection on the security appliance. The first involves
identifying the service to be redirected with the wccp command, and the second is defining on which
interface the redirection occurs with the wccp redirect command. The wccp command can optionally
also define which cache engines can participate in the service group, and what traffic should be
redirected to the cache engine.
WCCP redirect is supported only on the ingress of an interface. The only topology that the security
appliance supports is when client and cache engine are behind the same interface of the security
appliance and the cache engine can directly communicate with the client without going through the
security appliance.
The following configuration tasks assume you have already installed and configured the cache engines
you wish to include in your network.
To configure WCCP redirection, perform the following steps:
Step 1
To enable a WCCP service group, enter the following command:
hostname(config)# wccp {web-cache | service_number} [redirect-list access_list]
[group-list access_list] [password password]
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Configuring Web Cache Services Using WCCP
The standard service is web-cache, which intercepts TCP port 80 (HTTP) traffic and redirects that traffic
to the cache engines, but you can identify a service number if desired between 0 and 254. For example,
to transparently redirect native FTP traffic to a cache engine, use WCCP service 60. You can enter this
command multiple times for each service group you want to enable.
The redirect-list access_list argument controls traffic redirected to this service group.
The group-list access_list argument determines which web cache IP addresses are allowed to participate
in the service group.
The password password argument specifies MD5 authentication for messages received from the service
group. Messages that are not accepted by the authentication are discarded.
Step 2
To enable WCCP redirection on an interface, enter the following command:
hostname(config)# wccp interface interface_name {web-cache | service_number} redirect in
The standard service is web-cache, which intercepts TCP port 80 (HTTP) traffic and redirects that traffic
to the cache engines, but you can identify a service number if desired between 0 and 254. For example,
to transparently redirect native FTP traffic to a cache engine, use WCCP service 60. You can enter this
command multiple times for each service group you want to participate in.
For example, to enable the standard web-cache service and redirect HTTP traffic that enters the inside
interface to a web cache, enter the following commands:
hostname(config)# wccp web-cache
hostname(config)# wccp interface inside web-cache redirect in
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11
Configuring Multicast Routing
This chapter describes how to configure multicast routing. This section includes the following topics:
•
Multicast Routing Overview, page 11-13
•
Enabling Multicast Routing, page 11-14
•
Configuring IGMP Features, page 11-14
•
Configuring Stub Multicast Routing, page 11-17
•
Configuring a Static Multicast Route, page 11-17
•
Configuring PIM Features, page 11-18
•
For More Information about Multicast Routing, page 11-22
Multicast Routing Overview
The security appliance supports both stub multicast routing and PIM multicast routing. However, you
cannot configure both concurrently on a single security appliance.
Stub multicast routing provides dynamic host registration and facilitates multicast routing. When
configured for stub multicast routing, the security appliance acts as an IGMP proxy agent. Instead of
fully participating in multicast routing, the security appliance forwards IGMP messages to an upstream
multicast router, which sets up delivery of the multicast data. When configured for stub multicast
routing, the security appliance cannot be configured for PIM.
The security appliance supports both PIM-SM and bi-directional PIM. PIM-SM is a multicast routing
protocol that uses the underlying unicast routing information base or a separate multicast-capable
routing information base. It builds unidirectional shared trees rooted at a single Rendezvous Point per
multicast group and optionally creates shortest-path trees per multicast source.
Bi-directional PIM is a variant of PIM-SM that builds bi-directional shared trees connecting multicast
sources and receivers. Bi-directional trees are built using a DF election process operating on each link
of the multicast topology. With the assistance of the DF, multicast data is forwarded from sources to the
Rendezvous Point, and therefore along the shared tree to receivers, without requiring source-specific
state. The DF election takes place during Rendezvous Point discovery and provides a default route to the
Rendezvous Point.
Note
If the security appliance is the PIM RP, use the untranslated outside address of the security appliance as
the RP address.
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Enabling Multicast Routing
Enabling Multicast Routing
Enabling multicast routing lets the security appliance forward multicast packets. Enabling multicast
routing automatically enables PIM and IGMP on all interfaces. To enable multicast routing, enter the
following command:
hostname(config)# multicast-routing
The number of entries in the multicast routing tables are limited by the amount of RAM on the system.
Table 11-1 lists the maximum number of entries for specific multicast tables based on the amount of
RAM on the security appliance. Once these limits are reached, any new entries are discarded.
Table 11-1
Entry Limits for Multicast Tables
Table
16 MB 128 MB 128+ MB
MFIB
1000
3000
5000
IGMP Groups 1000
3000
5000
PIM Routes
7000
12000
3000
Configuring IGMP Features
IP hosts use IGMP to report their group memberships to directly connected multicast routers. IGMP uses
group addresses (Class D IP address) as group identifiers. Host group address can be in the range
224.0.0.0 to 239.255.255.255. The address 224.0.0.0 is never assigned to any group. The address
224.0.0.1 is assigned to all systems on a subnet. The address 224.0.0.2 is assigned to all routers on a
subnet.
When you enable multicast routing on the security appliance, IGMP Version 2 is automatically enabled
on all interfaces.
Note
Only the no igmp command appears in the interface configuration when you use the show run
command. If the multicast-routing command appears in the device configuration, then IGMP is
automatically enabled on all interfaces.
This section describes how to configure optional IGMP setting on a per-interface basis. This section
includes the following topics:
•
Disabling IGMP on an Interface, page 11-15
•
Configuring Group Membership, page 11-15
•
Configuring a Statically Joined Group, page 11-15
•
Controlling Access to Multicast Groups, page 11-15
•
Limiting the Number of IGMP States on an Interface, page 11-16
•
Modifying the Query Interval and Query Timeout, page 11-16
•
Changing the Query Response Time, page 11-17
•
Changing the IGMP Version, page 11-17
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Configuring IGMP Features
Disabling IGMP on an Interface
You can disable IGMP on specific interfaces. This is useful if you know that you do not have any
multicast hosts on a specific interface and you want to prevent the security appliance from sending host
query messages on that interface.
To disable IGMP on an interface, enter the following command:
hostname(config-if)# no igmp
To reenable IGMP on an interface, enter the following command:
hostname(config-if)# igmp
Note
Only the no igmp command appears in the interface configuration.
Configuring Group Membership
You can configure the security appliance to be a member of a multicast group. Configuring the security
appliance to join a multicast group causes upstream routers to maintain multicast routing table
information for that group and keep the paths for that group active.
To have the security appliance join a multicast group, enter the following command:
hostname(config-if)# igmp join-group group-address
Configuring a Statically Joined Group
Sometimes a group member cannot report its membership in the group, or there may be no members of
a group on the network segment, but you still want multicast traffic for that group to be sent to that
network segment. You can have multicast traffic for that group sent to the segment in one of two ways:
•
Using the igmp join-group command (see Configuring Group Membership, page 11-15). This
causes the security appliance to accept and to forward the multicast packets.
•
Using the igmp static-group command. The security appliance does not accept the multicast
packets but rather forwards them to the specified interface.
To configure a statically joined multicast group on an interface, enter the following command:
hostname(config-if)# igmp static-group group-address
Controlling Access to Multicast Groups
To control the multicast groups that hosts on the security appliance interface can join, perform the
following steps:
Step 1
Create an access list for the multicast traffic. You can create more than one entry for a single access list.
You can use extended or standard access lists.
•
To create a standard access list, enter the following command:
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hostname(config)# access-list name standard [permit | deny] ip_addr mask
The ip_addr argument is the IP address of the multicast group being permitted or denied.
•
To create an extended access list, enter the following command:
hostname(config)# access-list name extended [permit | deny] protocol src_ip_addr
src_mask dst_ip_addr dst_mask
The dst_ip_addr argument is the IP address of the multicast group being permitted or denied.
Step 2
Apply the access list to an interface by entering the following command:
hostname(config-if)# igmp access-group acl
The acl argument is the name of a standard or extended IP access list.
Limiting the Number of IGMP States on an Interface
You can limit the number of IGMP states resulting from IGMP membership reports on a per-interface
basis. Membership reports exceeding the configured limits are not entered in the IGMP cache and traffic
for the excess membership reports is not forwarded.
To limit the number of IGMP states on an interface, enter the following command:
hostname(config-if)# igmp limit number
Valid values range from 0 to 500, with 500 being the default value. Setting this value to 0 prevents
learned groups from being added, but manually defined memberships (using the igmp join-group and
igmp static-group commands) are still permitted. The no form of this command restores the default
value.
Modifying the Query Interval and Query Timeout
The security appliance sends query messages to discover which multicast groups have members on the
networks attached to the interfaces. Members respond with IGMP report messages indicating that they
want to receive multicast packets for specific groups. Query messages are addressed to the all-systems
multicast group, which has an address of 224.0.0.1, with a time-to-live value of 1.
These messages are sent periodically to refresh the membership information stored on the security
appliance. If the security appliance discovers that there are no local members of a multicast group still
attached to an interface, it stops forwarding multicast packet for that group to the attached network and
it sends a prune message back to the source of the packets.
By default, the PIM designated router on the subnet is responsible for sending the query messages. By
default, they are sent once every 125 seconds. To change this interval, enter the following command:
hostname(config-if)# igmp query-interval seconds
If the security appliance does not hear a query message on an interface for the specified timeout value
(by default, 255 seconds), then the security appliance becomes the designated router and starts sending
the query messages. To change this timeout value, enter the following command:
hostname(config-if)# igmp query-timeout seconds
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Configuring Stub Multicast Routing
Note
The igmp query-timeout and igmp query-interval commands require IGMP Version 2.
Changing the Query Response Time
By default, the maximum query response time advertised in IGMP queries is 10 seconds. If the security
appliance does not receive a response to a host query within this amount of time, it deletes the group.
To change the maximum query response time, enter the following command:
hostname(config-if)# igmp query-max-response-time seconds
Changing the IGMP Version
By default, the security appliance runs IGMP Version 2, which enables several additional features such
as the igmp query-timeout and igmp query-interval commands.
All multicast routers on a subnet must support the same version of IGMP. The security appliance does
not automatically detect version 1 routers and switch to version 1. However, a mix of IGMP Version 1
and 2 hosts on the subnet works; the security appliance running IGMP Version 2 works correctly when
IGMP Version 1 hosts are present.
To control which version of IGMP is running on an interface, enter the following command:
hostname(config-if)# igmp version {1 | 2}
Configuring Stub Multicast Routing
A security appliance acting as the gateway to the stub area does not need to participate in PIM. Instead,
you can configure it to act as an IGMP proxy agent and forward IGMP messages from hosts connected
on one interface to an upstream multicast router on another. To configure the security appliance as an
IGMP proxy agent, forward the host join and leave messages from the stub area interface to an upstream
interface.
To forward the host join and leave messages, enter the following command from the interface attached
to the stub area:
hostname(config-if)# igmp forward interface if_name
Note
Stub Multicast Routing and PIM are not supported concurrently.
Configuring a Static Multicast Route
When using PIM, the security appliance expects to receive packets on the same interface where it sends
unicast packets back to the source. In some cases, such as bypassing a route that does not support
multicast routing, you may want unicast packets to take one path and multicast packets to take another.
Static multicast routes are not advertised or redistributed.
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Configuring PIM Features
To configure a static multicast route for PIM, enter the following command:
hostname(config)# mroute src_ip src_mask {input_if_name | rpf_addr) [distance]
To configure a static multicast route for a stub area, enter the following command:
hostname(config)# mroute src_ip src_mask input_if_name [dense output_if_name] [distance]
Note
The dense output_if_name keyword and argument pair is only supported for stub multicast routing.
Configuring PIM Features
Routers use PIM to maintain forwarding tables for forwarding multicast diagrams. When you enable
multicast routing on the security appliance, PIM and IGMP are automatically enabled on all interfaces.
Note
PIM is not supported with PAT. The PIM protocol does not use ports and PAT only works with protocols
that use ports.
This section describes how to configure optional PIM settings. This section includes the following
topics:
•
Disabling PIM on an Interface, page 11-18
•
Configuring a Static Rendezvous Point Address, page 11-19
•
Configuring the Designated Router Priority, page 11-19
•
Filtering PIM Register Messages, page 11-19
•
Configuring PIM Message Intervals, page 11-20
•
Configuring a Multicast Boundary, page 11-20
•
Filtering PIM Neighbors, page 11-20
•
Supporting Mixed Bidirectional/Sparse-Mode PIM Networks, page 11-21
Disabling PIM on an Interface
You can disable PIM on specific interfaces. To disable PIM on an interface, enter the following
command:
hostname(config-if)# no pim
To reenable PIM on an interface, enter the following command:
hostname(config-if)# pim
Note
Only the no pim command appears in the interface configuration.
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Configuring PIM Features
Configuring a Static Rendezvous Point Address
All routers within a common PIM sparse mode or bidir domain require knowledge of the PIM RP
address. The address is statically configured using the pim rp-address command.
Note
The security appliance does not support Auto-RP or PIM BSR; you must use the pim rp-address
command to specify the RP address.
You can configure the security appliance to serve as RP to more than one group. The group range
specified in the access list determines the PIM RP group mapping. If an access list is not specified, then
the RP for the group is applied to the entire multicast group range (224.0.0.0/4).
To configure the address of the PIM PR, enter the following command:
hostname(config)# pim rp-address ip_address [acl] [bidir]
The ip_address argument is the unicast IP address of the router to be a PIM RP. The acl argument is the
name or number of a standard access list that defines which multicast groups the RP should be used with.
Do not use a host ACL with this command. Excluding the bidir keyword causes the groups to operate
in PIM sparse mode.
Note
The security appliance always advertises the bidir capability in the PIM hello messages regardless of the
actual bidir configuration.
Configuring the Designated Router Priority
The DR is responsible for sending PIM register, join, and prune messaged to the RP. When there is more
than one multicast router on a network segment, there is an election process to select the DR based on
DR priority. If multiple devices have the same DR priority, then the device with the highest IP address
becomes the DR.
By default, the security appliance has a DR priority of 1. You can change this value by entering the
following command:
hostname(config-if)# pim dr-priority num
The num argument can be any number from 1 to 4294967294.
Filtering PIM Register Messages
You can configure the security appliance to filter PIM register messages. To filter PIM register messages,
enter the following command:
hostname(config)# pim accept-register {list acl | route-map map-name}
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Configuring PIM Features
Configuring PIM Message Intervals
Router query messages are used to elect the PIM DR. The PIM DR is responsible for sending router
query messages. By default, router query messages are sent every 30 seconds. You can change this value
by entering the following command:
hostname(config-if)# pim hello-interval seconds
Valid values for the seconds argument range from 1 to 3600 seconds.
Every 60 seconds, the security appliance sends PIM join/prune messages. To change this value, enter the
following command:
hostname(config-if)# pim join-prune-interval seconds
Valid values for the seconds argument range from 10 to 600 seconds.
Configuring a Multicast Boundary
Address scoping defines domain boundaries so that domains with RPs that have the same IP address do
not leak into each other. Scoping is performed on the subnet boundaries within large domains and on the
boundaries between the domain and the Internet.
You can set up an administratively scoped boundary on an interface for multicast group addresses using
the multicast boundary command. IANA has designated the multicast address range 239.0.0.0 to
239.255.255.255 as the administratively scoped addresses. This range of addresses can be reused in
domains administered by different organizations. They would be considered local, not globally unique.
To configure a multicast boundary, enter the following command:
hostname(config-if)# multicast boundary acl [filter-autorp]
A standard ACL defines the range of addresses affected. When a boundary is set up, no multicast data
packets are allowed to flow across the boundary from either direction. The boundary allows the same
multicast group address to be reused in different administrative domains.
You can configure the filter-autorp keyword to examine and filter Auto-RP discovery and
announcement messages at the administratively scoped boundary. Any Auto-RP group range
announcements from the Auto-RP packets that are denied by the boundary access control list (ACL) are
removed. An Auto-RP group range announcement is permitted and passed by the boundary only if all
addresses in the Auto-RP group range are permitted by the boundary ACL. If any address is not
permitted, the entire group range is filtered and removed from the Auto-RP message before the Auto-RP
message is forwarded.
Filtering PIM Neighbors
You can define the routers that can become PIM neighbors with the pim neighbor-filter command. By
filtering the routers that can become PIM neighbors, you can:
•
Prevent unauthorized routers from becoming PIM neighbors.
•
Prevent attached stub routers from participating in PIM.
To define the neighbors that can become a PIM neighbor, perform the following steps:
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Configuring PIM Features
Step 1
Use the access-list command to define a standard access list defines the routers you want to participate
in PIM.
For example the following access list, when used with the pim neighbor-filter command, prevents the
10.1.1.1 router from becoming a PIM neighbor:
hostname(config)# access-list pim_nbr deny 10.1.1.1 255.255.255.255
Step 2
Use the pim neighbor-filter command on an interface to filter the neighbor routers.
For example, the following commands prevent the 10.1.1.1 router from becoming a PIM neighbor on
interface GigabitEthernet0/3:
hostname(config)# interface GigabitEthernet0/3
hostname(config-if)# pim neighbor-filter pim_nbr
Supporting Mixed Bidirectional/Sparse-Mode PIM Networks
Bidirectional PIM allows multicast routers to keep reduced state information. All of the multicast routers
in a segment must be bidirectionally enabled in order for bidir to elect a DF.
The pim bidir-neighbor-filter command enables the transition from a sparse-mode-only network to a
bidir network by letting you specify the routers that should participate in DF election while still allowing
all routers to participate in the sparse-mode domain. The bidir-enabled routers can elect a DF from
among themselves, even when there are non-bidir routers on the segment. Multicast boundaries on the
non-bidir routers prevent PIM messages and data from the bidir groups from leaking in or out of the bidir
subset cloud.
When the pim bidir-neighbor-filter command is enabled, the routers that are permitted by the ACL are
considered to be bidir-capable. Therefore:
•
If a permitted neighbor does not support bidir, the DF election does not occur.
•
If a denied neighbor supports bidir, then DF election does not occur.
•
If a denied neighbor des not support bidir, the DF election occurs.
To control which neighbors can participate in the DF election, perform the following steps:
Step 1
Use the access-list command to define a standard access list that permits the routers you want to
participate in the DF election and denies all others.
For example, the following access list permits the routers at 10.1.1.1 and 10.2.2.2 to participate in the
DF election and denies all others:
hostname(config)# access-list pim_bidir permit 10.1.1.1 255.255.255.255
hostname(config)# access-list pim_bidir permit 10.1.1.2 255.255.255.255
hostname(config)# access-list pim_bidir deny any
Step 2
Enable the pim bidir-neighbor-filter command on an interface.
The following example applies the access list created previous step to the interface GigabitEthernet0/3.
hostname(config)# interface GigabitEthernet0/3
hostname(config-if)# pim bidir-neighbor-filter pim_bidir
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For More Information about Multicast Routing
For More Information about Multicast Routing
The following RFCs from the IETF provide technical details about the IGMP and multicast routing
standards used for implementing the SMR feature:
•
RFC 2236 IGMPv2
•
RFC 2362 PIM-SM
•
RFC 2588 IP Multicast and Firewalls
•
RFC 2113 IP Router Alert Option
•
IETF draft-ietf-idmr-igmp-proxy-01.txt
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12
Configuring IPv6
This chapter describes how to enable and configure IPv6 on the security appliance. IPv6 is available in
Routed firewall mode only.
This chapter includes the following sections:
•
IPv6-enabled Commands, page 12-1
•
Configuring IPv6, page 12-2
•
Verifying the IPv6 Configuration, page 12-11
For an sample IPv6 configuration, see Appendix B, “Sample Configurations.”
IPv6-enabled Commands
The following security appliance commands can accept and display IPv6 addresses:
•
capture
•
configure
•
copy
•
http
•
name
•
object-group
•
ping
•
show conn
•
show local-host
•
show tcpstat
•
ssh
•
telnet
•
tftp-server
•
who
•
write
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Configuring IPv6
Note
Failover does not support IPv6. The ipv6 address command does not support setting standby addresses
for failover configurations. The failover interface ip command does not support using IPv6 addresses
on the failover and Stateful Failover interfaces.
When entering IPv6 addresses in commands that support them, simply enter the IPv6 address using
standard IPv6 notation, for example ping fe80::2e0:b6ff:fe01:3b7a. The security appliance correctly
recognizes and processes the IPv6 address. However, you must enclose the IPv6 address in square
brackets ([ ]) in the following situations:
•
You need to specify a port number with the address, for example
[fe80::2e0:b6ff:fe01:3b7a]:8080 .
•
The command uses a colon as a separator, such as the write net and config net commands, for
example configure net [fe80::2e0:b6ff:fe01:3b7a]:/tftp/config/pixconfig.
The following commands were modified to work for IPv6:
•
debug
•
fragment
•
ip verify
•
mtu
•
icmp (entered as ipv6 icmp)
The following inspection engines support IPv6:
•
FTP
•
HTTP
•
ICMP
•
SMTP
•
TCP
•
UDP
Configuring IPv6
This section contains the following topics:
•
Configuring IPv6 on an Interface, page 12-3
•
Configuring a Dual IP Stack on an Interface, page 12-4
•
Enforcing the Use of Modified EUI-64 Interface IDs in IPv6 Addresses, page 12-4
•
Configuring IPv6 Duplicate Address Detection, page 12-4
•
Configuring IPv6 Default and Static Routes, page 12-5
•
Configuring IPv6 Access Lists, page 12-6
•
Configuring IPv6 Neighbor Discovery, page 12-7
•
Configuring a Static IPv6 Neighbor, page 12-11
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Configuring IPv6
Configuring IPv6 on an Interface
At a minimum, each interface needs to be configured with an IPv6 link-local address. Additionally, you
can add a site-local and global address to the interface.
Note
The security appliance does not support IPv6 anycast addresses.
You can configure both IPv6 and IPv4 addresses on an interface.
To configure IPv6 on an interface, perform the following steps:
Step 1
Enter interface configuration mode for the interface on which you are configuring the IPv6 addresses:
hostname(config)# interface if
Step 2
Configure an IPv6 address on the interface. You can assign several IPv6 addresses to an interface, such
as an IPv6 link-local, site-local, and global address. However, at a minimum, you must configure a
link-local address.
There are several methods for configuring IPv6 addresses. Pick the method that suits your needs from
the following:
•
The simplest method is to enable stateless autoconfiguration on the interface. Enabling stateless
autoconfiguration on the interface configures IPv6 addresses based on prefixes received in Router
Advertisement messages. A link-local address, based on the Modified EUI-64 interface ID, is
automatically generated for the interface when stateless autoconfiguration is enabled. To enable
stateless autoconfiguration, enter the following command:
hostname(config-if)# ipv6 address autoconfig
•
If you only need to configure a link-local address on the interface and are not going to assign any
other IPv6 addresses to the interface, you have the option of manually defining the link-local address
or generating one based on the interface MAC address (Modified EUI-64 format):
– Enter the following command to manually specify the link-local address:
hostname(config-if)# ipv6 address ipv6-address link-local
– Enter the following command to enable IPv6 on the interface and automatically generate the
link-local address using the Modified EUI-64 interface ID based on the interface MAC address:
hostname(config-if)# ipv6 enable
Note
•
You do not need to use the ipv6 enable command if you enter any other ipv6 address
commands on an interface; IPv6 support is automatically enabled as soon as you assign an
IPv6 address to the interface.
Assign a site-local or global address to the interface. When you assign a site-local or global address,
a link-local address is automatically created. Enter the following command to add a global or
site-local address to the interface. Use the optional eui-64 keyword to use the Modified EUI-64
interface ID in the low order 64 bits of the address.
hostname(config-if)# ipv6 address ipv6-address [eui-64]
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Step 3
(Optional) Suppress Router Advertisement messages on an interface. By default, Router Advertisement
messages are automatically sent in response to router solicitation messages. You may want to disable
these messages on any interface for which you do not want the security appliance to supply the IPv6
prefix (for example, the outside interface).
Enter the following command to suppress Router Advertisement messages on an interface:
hostname(config-if)# ipv6 nd suppress-ra
Configuring a Dual IP Stack on an Interface
The security appliance supports the configuration of both IPv6 and IPv4 on an interface. You do not need
to enter any special commands to do so; simply enter the IPv4 configuration commands and IPv6
configuration commands as you normally would. Make sure you configure a default route for both IPv4
and IPv6.
Enforcing the Use of Modified EUI-64 Interface IDs in IPv6 Addresses
RFC 3513: Internet Protocol Version 6 (IPv6) Addressing Architecture requires that the interface
identifier portion of all unicast IPv6 addresses, except those that start with binary value 000, be 64 bits
long and be constructed in Modified EUI-64 format. The security appliance can enforce this requirement
for hosts attached to the local link.
To enforce the use of Modified EUI-64 format interface identifiers in IPv6 addresses on a local link,
enter the following command:
hostname(config)# ipv6 enforce-eui64 if_name
The if_name argument is the name of the interface, as specified by the namif command, on which you
are enabling the address format enforcement.
When this command is enabled on an interface, the source addresses of IPv6 packets received on that
interface are verified against the source MAC addresses to ensure that the interface identifiers use the
Modified EUI-64 format. If the IPv6 packets do not use the Modified EUI-64 format for the interface
identifier, the packets are dropped and the following system log message is generated:
%PIX|ASA-3-325003: EUI-64 source address check failed.
The address format verification is only performed when a flow is created. Packets from an existing flow
are not checked. Additionally, the address verification can only be performed for hosts on the local link.
Packets received from hosts behind a router will fail the address format verification, and be dropped,
because their source MAC address will be the router MAC address and not the host MAC address.
Configuring IPv6 Duplicate Address Detection
During the stateless autoconfiguration process, duplicate address detection verifies the uniqueness of
new unicast IPv6 addresses before the addresses are assigned to interfaces (the new addresses remain in
a tentative state while duplicate address detection is performed). Duplicate address detection is
performed first on the new link-local address. When the link local address is verified as unique, then
duplicate address detection is performed all the other IPv6 unicast addresses on the interface.
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Configuring IPv6
Duplicate address detection is suspended on interfaces that are administratively down. While an
interface is administratively down, the unicast IPv6 addresses assigned to the interface are set to a
pending state. An interface returning to an administratively up state restarts duplicate address detection
for all of the unicast IPv6 addresses on the interface.
When a duplicate address is identified, the state of the address is set to DUPLICATE, the address is not
used, and the following error message is generated:
%PIX|ASA-4-325002: Duplicate address ipv6_address/MAC_address on interface
If the duplicate address is the link-local address of the interface, the processing of IPv6 packets is
disabled on the interface. If the duplicate address is a global address, the address is not used. However,
all configuration commands associated with the duplicate address remain as configured while the state
of the address is set to DUPLICATE.
If the link-local address for an interface changes, duplicate address detection is performed on the new
link-local address and all of the other IPv6 address associated with the interface are regenerated
(duplicate address detection is performed only on the new link-local address).
The security appliance uses neighbor solicitation messages to perform duplicate address detection. By
default, the number of times an interface performs duplicate address detection is 1.
To change the number of duplicate address detection attempts, enter the following command:
hostname(config-if)# ipv6 nd dad attempts value
The value argument can be any value from 0 to 600. Setting the value argument to 0 disables duplicate
address detection on the interface.
When you configure an interface to send out more than one duplicate address detection attempt, you can
also use the ipv6 nd ns-interval command to configure the interval at which the neighbor solicitation
messages are sent out. By default, they are sent out once every 1000 milliseconds.
To change the neighbor solicitation message interval, enter the following command:
hostname(config-if)# ipv6 nd ns-interval value
The value argument can be from 1000 to 3600000 milliseconds.
Note
Changing this value changes it for all neighbor solicitation messages sent out on the interface, not just
those used for duplicate address detection.
Configuring IPv6 Default and Static Routes
The security appliance automatically routes IPv6 traffic between directly connected hosts if the
interfaces to which the hosts are attached are enabled for IPv6 and the IPv6 ACLs allow the traffic.
The security appliance does not support dynamic routing protocols. Therefore, to route IPv6 traffic to a
non-connected host or network, you need to define a static route to the host or network or, at a minimum,
a default route. Without a static or default route defined, traffic to non-connected hosts or networks
generate the following error message:
%PIX|ASA-6-110001: No route to dest_address from source_address
You can add a default route and static routes using the ipv6 route command.
To configure an IPv6 default route and static routes, perform the following steps:
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Configuring IPv6
Step 1
To add the default route, use the following command:
hostname(config)# ipv6 route if_name ::/0 next_hop_ipv6_addr
The address ::/0 is the IPv6 equivalent of “any.”
Step 2
(Optional) Define IPv6 static routes. Use the following command to add an IPv6 static route to the IPv6
routing table:
hostname(config)# ipv6 route if_name destination next_hop_ipv6_addr [admin_distance]
Note
The ipv6 route command works like the route command used to define IPv4 static routes.
Configuring IPv6 Access Lists
Configuring an IPv6 access list is similar configuring an IPv4 access, but with IPv6 addresses.
To configure an IPv6 access list, perform the following steps:
Step 1
Create an access entry. To create an access list, use the ipv6 access-list command to create entries for
the access list. There are two main forms of this command to choose from, one for creating access list
entries specifically for ICMP traffic, and one to create access list entries for all other types of IP traffic.
•
To create an IPv6 access list entry specifically for ICMP traffic, enter the following command:
hostname(config)# ipv6 access-list id [line num] {permit | deny} icmp source
destination [icmp_type]
•
To create an IPv6 access list entry, enter the following command:
hostname(config)# ipv6 access-list id [line num] {permit | deny} protocol source
[src_port] destination [dst_port]
The following describes the arguments for the ipv6 access-list command:
•
id—The name of the access list. Use the same id in each command when you are entering multiple
entries for an access list.
•
line num—When adding an entry to an access list, you can specify the line number in the list where
the entry should appear.
•
permit | deny—Determines whether the specified traffic is blocked or allowed to pass.
•
icmp—Indicates that the access list entry applies to ICMP traffic.
•
protocol—Specifies the traffic being controlled by the access list entry. This can be the name (ip,
tcp, or udp) or number (1-254) of an IP protocol. Alternatively, you can specify a protocol object
group using object-group grp_id.
•
source and destination—Specifies the source or destination of the traffic. The source or destination
can be an IPv6 prefix, in the format prefix/length, to indicate a range of addresses, the keyword any,
to specify any address, or a specific host designated by host host_ipv6_addr.
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Step 2
•
src_port and dst_port—The source and destination port (or service) argument. Enter an operator (lt
for less than, gt for greater than, eq for equal to, neq for not equal to, or range for an inclusive
range) followed by a space and a port number (or two port numbers separated by a space for the
range keyword).
•
icmp_type—Specifies the ICMP message type being filtered by the access rule. The value can be a
valid ICMP type number (from 0 to 155) or one of the ICMP type literals as shown in Appendix D,
“Addresses, Protocols, and Ports”. Alternatively, you can specify an ICMP object group using
object-group id.
To apply the access list to an interface, enter the following command:
hostname(config)# access-group access_list_name {in | out} interface if_name
Configuring IPv6 Neighbor Discovery
The IPv6 neighbor discovery process uses ICMPv6 messages and solicited-node multicast addresses to
determine the link-layer address of a neighbor on the same network (local link), verify the reachability
of a neighbor, and keep track of neighboring routers.
This section contains the following topics:
•
Configuring Neighbor Solicitation Messages, page 12-7
•
Configuring Router Advertisement Messages, page 12-9
•
Multicast Listener Discovery Support, page 12-11
Configuring Neighbor Solicitation Messages
Neighbor solicitation messages (ICMPv6 Type 135) are sent on the local link by nodes attempting to
discover the link-layer addresses of other nodes on the local link. The neighbor solicitation message is
sent to the solicited-node multicast address.The source address in the neighbor solicitation message is
the IPv6 address of the node sending the neighbor solicitation message. The neighbor solicitation
message also includes the link-layer address of the source node.
After receiving a neighbor solicitation message, the destination node replies by sending a neighbor
advertisement message (ICPMv6 Type 136) on the local link. The source address in the neighbor
advertisement message is the IPv6 address of the node sending the neighbor advertisement message; the
destination address is the IPv6 address of the node that sent the neighbor solicitation message. The data
portion of the neighbor advertisement message includes the link-layer address of the node sending the
neighbor advertisement message.
After the source node receives the neighbor advertisement, the source node and destination node can
communicate. Figure 12-1 shows the neighbor solicitation and response process.
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Figure 12-1
IPv6 Neighbor Discovery—Neighbor Solicitation Message
ICMPv6 Type = 135
Src = A
Dst = solicited-node multicast of B
Data = link-layer address of A
Query = what is your link address?
A and B can now exchange
packets on this link
132958
ICMPv6 Type = 136
Src = B
Dst = A
Data = link-layer address of B
Neighbor solicitation messages are also used to verify the reachability of a neighbor after the link-layer
address of a neighbor is identified. When a node wants to verifying the reachability of a neighbor, the
destination address in a neighbor solicitation message is the unicast address of the neighbor.
Neighbor advertisement messages are also sent when there is a change in the link-layer address of a node
on a local link. When there is such a change, the destination address for the neighbor advertisement is
the all-nodes multicast address.
You can configure the neighbor solicitation message interval and neighbor reachable time on a
per-interface basis. See the following topics for more information:
•
Configuring the Neighbor Solicitation Message Interval, page 12-8
•
Configuring the Neighbor Reachable Time, page 12-8
Configuring the Neighbor Solicitation Message Interval
To configure the interval between IPv6 neighbor solicitation retransmissions on an interface, enter the
following command:
hostname(config-if)# ipv6 nd ns-interval value
Valid values for the value argument range from 1000 to 3600000 milliseconds. The default value is 1000
milliseconds.
This setting is also sent in router advertisement messages.
Configuring the Neighbor Reachable Time
The neighbor reachable time enables detecting unavailable neighbors. Shorter configured times enable
detecting unavailable neighbors more quickly; however, shorter times consume more IPv6 network
bandwidth and processing resources in all IPv6 network devices. Very short configured times are not
recommended in normal IPv6 operation.
To configure the amount of time that a remote IPv6 node is considered reachable after a reachability
confirmation event has occurred, enter the following command:
hostname(config-if)# ipv6 nd reachable-time value
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Valid values for the value argument range from 0 to 3600000 milliseconds. The default is 0.
This information is also sent in router advertisement messages.
When 0 is used for the value, the reachable time is sent as undetermined. It is up to the receiving devices
to set and track the reachable time value. To see the time used by the security appliance when this value
is set to 0, use the show ipv6 interface command to display information about the IPv6 interface,
including the ND reachable time being used.
Configuring Router Advertisement Messages
Router advertisement messages (ICMPv6 Type 134) are periodically sent out each IPv6 configured
interface of security appliance. The router advertisement messages are sent to the all-nodes multicast
address.
IPv6 Neighbor Discovery—Router Advertisement Message
Router
advertisement
Router
advertisement
Router advertisement packet definitions:
ICMPv6 Type = 134
Src = router link-local address
Dst = all-nodes multicast address
Data = options, prefix, lifetime, autoconfig flag
132917
Figure 12-2
Router advertisement messages typically include the following information:
•
One or more IPv6 prefix that nodes on the local link can use to automatically configure their IPv6
addresses.
•
Lifetime information for each prefix included in the advertisement.
•
Sets of flags that indicate the type of autoconfiguration (stateless or stateful) that can be completed.
•
Default router information (whether the router sending the advertisement should be used as a default
router and, if so, the amount of time (in seconds) the router should be used as a default router).
•
Additional information for hosts, such as the hop limit and MTU a host should use in packets that it
originates.
•
The amount of time between neighbor solicitation message retransmissions on a given link.
•
The amount of time a node considers a neighbor reachable.
Router advertisements are also sent in response to router solicitation messages (ICMPv6 Type 133).
Router solicitation messages are sent by hosts at system startup so that the host can immediately
autoconfigure without needing to wait for the next scheduled router advertisement message. Because
router solicitation messages are usually sent by hosts at system startup, and the host does not have a
configured unicast address, the source address in router solicitation messages is usually the unspecified
IPv6 address (0:0:0:0:0:0:0:0). If the host has a configured unicast address, the unicast address of the
interface sending the router solicitation message is used as the source address in the message. The
destination address in router solicitation messages is the all-routers multicast address with a scope of the
link. When a router advertisement is sent in response to a router solicitation, the destination address in
the router advertisement message is the unicast address of the source of the router solicitation message.
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Configuring IPv6
You can configure the following settings for router advertisement messages:
•
The time interval between periodic router advertisement messages.
•
The router lifetime value, which indicates the amount of time IPv6 nodes should consider security
appliance to be the default router.
•
The IPv6 network prefixes in use on the link.
•
Whether or not an interface transmits router advertisement messages.
Unless otherwise noted, the router advertisement message settings are specific to an interface and are
entered in interface configuration mode. See the following topics for information about changing these
settings:
•
Configuring the Router Advertisement Transmission Interval, page 12-10
•
Configuring the Router Lifetime Value, page 12-10
•
Configuring the IPv6 Prefix, page 12-10
•
Suppressing Router Advertisement Messages, page 12-11
Configuring the Router Advertisement Transmission Interval
By default, router advertisements are sent out every 200 seconds. To change the interval between router
advertisement transmissions on an interface, enter the following command:
ipv6 nd ra-interval [msec] value
Valid values range from 3 to 1800 seconds (or 500 to 1800000 milliseconds if the msec keyword is used).
The interval between transmissions should be less than or equal to the IPv6 router advertisement lifetime
if security appliance is configured as a default router by using the ipv6 nd ra-lifetime command. To
prevent synchronization with other IPv6 nodes, randomly adjust the actual value used to within 20
percent of the desired value.
Configuring the Router Lifetime Value
The router lifetime value specifies how long nodes on the local link should consider security appliance
as the default router on the link.
To configure the router lifetime value in IPv6 router advertisements on an interface, enter the following
command:
hostname(config-if)# ipv6 nd ra-lifetime seconds
Valid values range from 0 to 9000 seconds. The default is 1800 seconds. Entering 0 indicates that
security appliance should not be considered a default router on the selected interface.
Configuring the IPv6 Prefix
Stateless autoconfiguration uses IPv6 prefixes provided in router advertisement messages to create the
global unicast address from the link-local address.
To configure which IPv6 prefixes are included in IPv6 router advertisements, enter the following
command:
hostname(config-if)# ipv6 nd prefix ipv6-prefix/prefix-length
Note
For stateless autoconfiguration to work properly, the advertised prefix length in router advertisement
messages must always be 64 bits.
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Configuring IPv6
Verifying the IPv6 Configuration
Suppressing Router Advertisement Messages
By default, Router Advertisement messages are automatically sent in response to router solicitation
messages. You may want to disable these messages on any interface for which you do not want security
appliance to supply the IPv6 prefix (for example, the outside interface).
To suppress IPv6 router advertisement transmissions on an interface, enter the following command:
hostname(config-if)# ipv6 nd suppress-ra
Entering this command causes the security appliance to appear as a regular IPv6 neighbor on the link
and not as an IPv6 router.
Multicast Listener Discovery Support
Multicast Listener Discovery Protocol (MLD) Version 2 is supported to discover the presence of
multicast address listeners on their directly attached links, and to discover specifically which multicast
addresses are of interest to those neighboring nodes. ASA becomes a multicast address listener, or a
host, but not a multicast router, and responds to Multicast Listener Queries and sends Multicast Listener Reports only.
The following commands were added or enhanced to support MLD:
•
clear ipv6 mld traffic Command
•
show ipv6 mld Command
Configuring a Static IPv6 Neighbor
You can manually define a neighbor in the IPv6 neighbor cache. If an entry for the specified IPv6 address
already exists in the neighbor discovery cache—learned through the IPv6 neighbor discovery
process—the entry is automatically converted to a static entry. Static entries in the IPv6 neighbor
discovery cache are not modified by the neighbor discovery process.
To configure a static entry in the IPv6 neighbor discovery cache, enter the following command:
hostname(config-if)# ipv6 neighbor ipv6_address if_name mac_address
The ipv6_address argument is the link-local IPv6 address of the neighbor, the if_name argument is the
interface through which the neighbor is available, and the mac_address argument is the MAC address of
the neighbor interface.
Note
The clear ipv6 neighbors command does not remove static entries from the IPv6 neighbor discovery
cache; it only clears the dynamic entries.
Verifying the IPv6 Configuration
This section describes how to verify your IPv6 configuration. You can use various clear, and show
commands to verify your IPv6 settings.
This section includes the following topics:
•
The show ipv6 interface Command, page 12-12
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Verifying the IPv6 Configuration
•
The show ipv6 route Command, page 12-12
•
The show ipv6 mld traffic Command, page 12-13
The show ipv6 interface Command
To display the IPv6 interface settings, enter the following command:
hostname# show ipv6 interface [if_name]
Including the interface name, such as “outside”, displays the settings for the specified interface.
Excluding the name from the command displays the setting for all interfaces that have IPv6 enabled on
them. The output for the command shows the following:
•
The name and status of the interface.
•
The link-local and global unicast addresses.
•
The multicast groups the interface belongs to.
•
ICMP redirect and error message settings.
•
Neighbor discovery settings.
The following is sample output from the show ipv6 interface command:
hostname# show ipv6 interface
ipv6interface is down, line protocol is down
IPv6 is enabled, link-local address is fe80::20d:88ff:feee:6a82 [TENTATIVE]
No global unicast address is configured
Joined group address(es):
ff02::1
ff02::1:ffee:6a82
ICMP error messages limited to one every 100 milliseconds
ICMP redirects are enabled
ND DAD is enabled, number of DAD attempts: 1
ND reachable time is 30000 milliseconds
Note
The show interface command only displays the IPv4 settings for an interface. To see the IPv6
configuration on an interface, you need to use the show ipv6 interface command. The show ipv6
interface command does not display any IPv4 settings for the interface (if both types of addresses are
configured on the interface).
The show ipv6 route Command
To display the routes in the IPv6 routing table, enter the following command:
hostname# show ipv6 route
The output from the show ipv6 route command is similar to the IPv4 show route command. It displays
the following information:
•
The protocol that derived the route.
•
The IPv6 prefix of the remote network.
•
The administrative distance and metric for the route.
•
The address of the next-hop router.
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•
The interface through which the next hop router to the specified network is reached.
The following is sample output from the show ipv6 route command:
hostname# show ipv6 route
IPv6 Routing Table - 7 entries
Codes: C - Connected, L - Local, S - Static, R - RIP, B - BGP
U - Per-user Static route
I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea
O - OSPF intra, OI - OSPF inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
L
fe80::/10 [0/0]
via ::, inside
L
fec0::a:0:0:a0a:a70/128 [0/0]
via ::, inside
C
fec0:0:0:a::/64 [0/0]
via ::, inside
L
ff00::/8 [0/0]
via ::, inside
The show ipv6 mld traffic Command
To display the MLD traffic counters in the IPv6 routing table, enter the following command:
hostname# show ipv6 mld traffic
The output from the show ipv6 mld traffic command displays whether the expected number of MLD
protocol messages have been received and sent.
The following is sample output from the show ipv6 mld traffic command:
hostname# show ipv6 mld traffic
show ipv6 mld traffic
MLD Traffic Counters
Elapsed time since counters cleared:
Received
Valid MLD Packets 1
Queries
1
Reports
0
Leaves
0
Mtrace packets
0
0
Errors:
Malformed Packets 0
Martian source
0
Non link-local source 0
Hop limit is not equal to 1 0
00:01:19
Sent
3
0
3
0
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Verifying the IPv6 Configuration
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13
Configuring AAA Servers and the Local Database
This chapter describes support for AAA (pronounced “triple A”) and how to configure AAA servers and
the local database.
This chapter contains the following sections:
•
AAA Overview, page 13-1
•
AAA Server and Local Database Support, page 13-2
•
Configuring the Local Database, page 13-10
•
Identifying AAA Server Groups and Servers, page 13-12
•
Using Certificates and User Login Credentials, page 13-15
•
Supporting a Zone Labs Integrity Server, page 13-16
AAA Overview
AAA enables the security appliance to determine who the user is (authentication), what the user can do
(authorization), and what the user did (accounting).
AAA provides an extra level of protection and control for user access than using access lists alone. For
example, you can create an access list allowing all outside users to access Telnet on a server on the DMZ
network. If you want only some users to access the server and you might not always know IP addresses
of these users, you can enable AAA to allow only authenticated and/or authorized users to make it
through the security appliance. (The Telnet server enforces authentication, too; the security appliance
prevents unauthorized users from attempting to access the server.)
You can use authentication alone or with authorization and accounting. Authorization always requires a
user to be authenticated first. You can use accounting alone, or with authentication and authorization.
This section includes the following topics:
•
About Authentication, page 13-1
•
About Authorization, page 13-2
•
About Accounting, page 13-2
About Authentication
Authentication controls access by requiring valid user credentials, which are typically a username and
password. You can configure the security appliance to authenticate the following items:
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•
All administrative connections to the security appliance including the following sessions:
– Telnet
– SSH
– Serial console
– ASDM (using HTTPS)
– VPN management access
•
The enable command
•
Network access
•
VPN access
About Authorization
Authorization controls access per user after users authenticate. You can configure the security appliance
to authorize the following items:
•
Management commands
•
Network access
•
VPN access
Authorization controls the services and commands available to each authenticated user. Were you not to
enable authorization, authentication alone would provide the same access to services for all
authenticated users.
If you need the control that authorization provides, you can configure a broad authentication rule, and
then have a detailed authorization configuration. For example, you authenticate inside users who attempt
to access any server on the outside network and then limit the outside servers that a particular user can
access using authorization.
The security appliance caches the first 16 authorization requests per user, so if the user accesses the same
services during the current authentication session, the security appliance does not resend the request to
the authorization server.
About Accounting
Accounting tracks traffic that passes through the security appliance, enabling you to have a record of
user activity. If you enable authentication for that traffic, you can account for traffic per user. If you do
not authenticate the traffic, you can account for traffic per IP address. Accounting information includes
when sessions start and stop, username, the number of bytes that pass through the security appliance for
the session, the service used, and the duration of each session.
AAA Server and Local Database Support
The security appliance supports a variety of AAA server types and a local database that is stored on the
security appliance. This section describes support for each AAA server type and the local database.
This section contains the following topics:
•
Summary of Support, page 13-3
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•
RADIUS Server Support, page 13-3
•
TACACS+ Server Support, page 13-4
•
SDI Server Support, page 13-4
•
NT Server Support, page 13-5
•
Kerberos Server Support, page 13-5
•
LDAP Server Support, page 13-6
•
SSO Support for WebVPN with HTTP Forms, page 13-9
•
Local Database Support, page 13-9
Summary of Support
Table 13-1 summarizes the support for each AAA service by each AAA server type, including the local
database. For more information about support for a specific AAA server type, refer to the topics
following the table.
Table 13-1
Summary of AAA Support
Database Type
Local
RADIUS
TACACS+
SDI
NT
Kerberos
LDAP
HTTP
Form
VPN users
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes1
Firewall sessions
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
Yes
Yes
Yes
No
AAA Service
Authentication of...
Administrators
Yes
Yes
Yes
Yes
2
Yes
Yes
No
No
No
No
Yes
No
Yes
No
No
No
No
No
No
Yes
No
No
No
No
No
Authorization of...
VPN users
Firewall sessions
Administrators
No
Yes
Yes
4
3
Accounting of...
VPN connections
No
Yes
Yes
No
No
No
No
No
Firewall sessions
No
Yes
Yes
No
No
No
No
No
Administrators
No
Yes5
Yes
No
No
No
No
No
1. HTTP Form protocol supports single sign-on authentication for WebVPN users only.
2. SDI is not supported for HTTP administrative access.
3. For firewall sessions, RADIUS authorization is supported with user-specific access lists only, which are received or
specified in a RADIUS authentication response.
4. Local command authorization is supported by privilege level only.
5. Command accounting is available for TACACS+ only.
RADIUS Server Support
The security appliance supports RADIUS servers.
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This section contains the following topics:
•
Authentication Methods, page 13-4
•
Attribute Support, page 13-4
•
RADIUS Authorization Functions, page 13-4
Authentication Methods
The security appliance supports the following authentication methods with RADIUS:
•
PAP—For all connection types.
•
CHAP—For L2TP-over-IPSec.
•
MS-CHAPv1—For L2TP-over-IPSec.
•
MS-CHAPv2—For L2TP-over-IPSec, and for regular IPSec remote access connections when the
password management feature is enabled.
Attribute Support
The security appliance supports the following sets of RADIUS attributes:
•
Authentication attributes defined in RFC 2138.
•
Accounting attributes defined in RFC 2139.
•
RADIUS attributes for tunneled protocol support, defined in RFC 2868.
•
Cisco IOS VSAs, identified by RADIUS vendor ID 9.
•
Cisco VPN-related VSAs, identified by RADIUS vendor ID 3076.
•
Microsoft VSAs, defined in RFC 2548.
RADIUS Authorization Functions
The security appliance can use RADIUS servers for user authorization for network access using dynamic
access lists or access list names per user. To implement dynamic access lists, you must configure the
RADIUS server to support it. When the user authenticates, the RADIUS server sends a downloadable
access list or access list name to the security appliance. Access to a given service is either permitted or
denied by the access list. The security appliance deletes the access list when the authentication session
expires.
TACACS+ Server Support
The security appliance supports TACACS+ authentication with ASCII, PAP, CHAP, and MS-CHAPv1.
SDI Server Support
The RSA SecureID servers are also known as SDI servers.
This section contains the following topics:
•
SDI Version Support, page 13-5
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•
Two-step Authentication Process, page 13-5
•
SDI Primary and Replica Servers, page 13-5
SDI Version Support
The security appliance supports SDI Version 5.0 and 6.0. SDI uses the concepts of an SDI primary and
SDI replica servers. Each primary and its replicas share a single node secret file. The node secret file has
its name based on the hexadecimal value of the ACE/Server IP address with .sdi appended.
A version 5.0 or 6.0 SDI server that you configure on the security appliance can be either the primary or
any one of the replicas. See the “SDI Primary and Replica Servers” section on page 13-5 for information
about how the SDI agent selects servers to authenticate users.
Two-step Authentication Process
SDI version 5.0 and 6.0 uses a two-step process to prevent an intruder from capturing information from
an RSA SecurID authentication request and using it to authenticate to another server. The Agent first
sends a lock request to the SecurID server before sending the user authentication request. The server
locks the username, preventing another (replica) server from accepting it. This means that the same user
cannot authenticate to two security appliances using the same authentication servers simultaneously.
After a successful username lock, the security appliance sends the passcode.
SDI Primary and Replica Servers
The security appliance obtains the server list when the first user authenticates to the configured server,
which can be either a primary or a replica. The security appliance then assigns priorities to each of the
servers on the list, and subsequent server selection derives at random from those assigned priorities. The
highest priority servers have a higher likelihood of being selected.
NT Server Support
The security appliance supports Microsoft Windows server operating systems that support NTLM
version 1, collectively referred to as NT servers.
Note
NT servers have a maximum length of 14 characters for user passwords. Longer passwords are truncated.
This is a limitation of NTLM version 1.
Kerberos Server Support
The security appliance supports 3DES, DES, and RC4 encryption types.
Note
The security appliance does not support changing user passwords during tunnel negotiation. To avoid
this situation happening inadvertently, disable password expiration on the Kerberos/Active Directory
server for users connecting to the security appliance.
For a simple Kerberos server configuration example, see Example 13-2.
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LDAP Server Support
This section describes using an LDAP directory with the security appliance for user authentication and
VPN authorization. This section includes the following topics:
•
Authentication with LDAP, page 13-6
•
Authorization with LDAP for VPN, page 13-7
•
LDAP Attribute Mapping, page 13-8
For example configuration procedures used to set up LDAP authentication or authorization, see
Appendix E, “Configuring an External Server for Authorization and Authentication”.
Authentication with LDAP
During authentication, the security appliance acts as a client proxy to the LDAP server for the user, and
authenticates to the LDAP server in either plain text or using the Simple Authentication and Security
Layer (SASL) protocol. By default, the security appliance passes authentication parameters, usually a
username and password, to the LDAP server in plain text. Whether using SASL or plain text, you can
secure the communications between the security appliance and the LDAP server with SSL using the
ldap-over-ssl command.
Note
If you do not configure SASL, we strongly recommend that you secure LDAP communications with
SSL. See the ldap-over-ssl command in the Cisco Security Appliance Command Reference.
When user LDAP authentication has succeeded, the LDAP server returns the attributes for the
authenticated user. For VPN authentication, these attributes generally include authorization data which
is applied to the VPN session. Thus, using LDAP accomplishes authentication and authorization in a
single step.
Securing LDAP Authentication with SASL
The security appliance supports the following SASL mechanisms, listed in order of increasing strength:
•
Digest-MD5 — The security appliance responds to the LDAP server with an MD5 value computed
from the username and password.
•
Kerberos — The security appliance responds to the LDAP server by sending the username and realm
using the GSSAPI (Generic Security Services Application Programming Interface) Kerberos
mechanism.
You can configure the security appliance and LDAP server to support any combination of these SASL
mechanisms. If you configure multiple mechanisms, the security appliance retrieves the list of SASL
mechanisms configured on the server and sets the authentication mechanism to the strongest mechanism
configured on both the security appliance and the server. For example, if both the LDAP server and the
security appliance support both mechanisms, the security appliance selects Kerberos, the stronger of the
mechanisms.
The following example configures the security appliance for authentication to an LDAP directory server
named ldap_dir_1 using the digest-MD5 SASL mechanism, and communicating over an SSL-secured
connection:
hostname(config)# aaa-server ldap_dir_1 protocol ldap
hostname(config-aaa-server-group)# aaa-server ldap_dir_1 host 10.1.1.4
hostname(config-aaa-server-host)# sasl-mechanism digest-md5
hostname(config-aaa-server-host)# ldap-over-ssl enable
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hostname(config-aaa-server-host)#
Setting the LDAP Server Type
The security appliance supports LDAP Version 3. In the current release, it is compatible only with the
Sun Microsystems JAVA System Directory Server (formerly named the Sun ONE Directory Server) and
the Microsoft Active Directory. In later releases, the security appliance will support other OpenLDAP
servers.
By default, the security appliance auto-detects whether it is connected to a Microsoft or a Sun LDAP
directory server. However, if auto-detection fails to determine the LDAP server type, and you know the
server is either a Microsoft or Sun server, you can manually configure the server type. The following
example sets the LDAP directory server ldap_dir_1 to the Sun Microsystems type:
hostname(config)# aaa-server ldap_dir_1 protocol ldap
hostname(config-aaa-server-group)# aaa-server ldap_dir_1 host 10.1.1.4
hostname(config-aaa-server-host)# server-type sun
hostname(config-aaa-server-host)#
Note
•
Sun—The DN configured on the security appliance to access a Sun directory server must be able to
access the default password policy on that server. We recommend using the directory administrator,
or a user with directory administrator privileges, as the DN. Alternatively, you can place an ACI on
the default password policy.
•
Microsoft—You must configure LDAP over SSL to enable password management with Microsoft
Active Directory.
Authorization with LDAP for VPN
When user LDAP authentication for VPN access has succeeded, the security appliance queries the LDAP
server which returns LDAP attributes. These attributes generally include authorization data that applies
to the VPN session. Thus, using LDAP accomplishes authentication and authorization in a single step.
There may be cases, however, where you require authorization from an LDAP directory server that is
separate and distinct from the authentication mechanism. For example, if you use an SDI or certificate
server for authentication, no authorization information is passed back. For user authorizations in this
case, you can query an LDAP directory after successful authentication, accomplishing authentication
and authorization in two steps.
To set up VPN user authorization using LDAP, you must first create a AAA server group and a tunnel
group. You then associate the server and tunnel groups using the tunnel-group general-attributes
command. While there are other authorization-related commands and options available for specific
requirements, the following example shows fundamental commands for enabling user authorization with
LDAP. This example then creates an IPSec remote access tunnel group named remote-1, and assigns that
new tunnel group to the previously created ldap_dir_1 AAA server for authorization.
hostname(config)# tunnel-group remote-1 type ipsec-ra
hostname(config)# tunnel-group remote-1 general-attributes
hostname(config-general)# authorization-server-group ldap_dir_1
hostname(config-general)#
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After you complete this fundamental configuration work, you can configure additional LDAP
authorization parameters such as a directory password, a starting point for searching a directory, and the
scope of a directory search:
hostname(config)# aaa-server ldap_dir_1 protocol ldap
hostname(config-aaa-server-group)# aaa-server ldap_dir_1 host 10.1.1.4
hostname(config-aaa-server-host)# ldap-login-dn obscurepassword
hostname(config-aaa-server-host)# ldap-base-dn starthere
hostname(config-aaa-server-host)# ldap-scope subtree
hostname(config-aaa-server-host)#
See LDAP commands in the Cisco Security Appliance Command Reference for more information.
LDAP Attribute Mapping
If you are introducing a security appliance to an existing LDAP directory, your existing LDAP attribute
names and values are probably different from the existing ones. You must create LDAP attribute maps
that map your existing user-defined attribute names and values to Cisco attribute names and values that
are compatible with the security appliance. You can then bind these attribute maps to LDAP servers or
remove them as needed. You can also show or clear attribute maps.
Note
To use the attribute mapping features correctly, you need to understand the Cisco LDAP attribute names
and values as well as the user-defined attribute names and values.
The following command, entered in global configuration mode, creates an unpopulated LDAP attribute
map table named att_map_1:
hostname(config)# ldap attribute-map att_map_1
hostname(config-ldap-attribute-map)#
The following commands map the user-defined attribute name department to the Cisco attribute name
cVPN3000-IETF-Radius-Class. The second command maps the user-defined attribute value Engineering
to the user-defined attribute department and the Cisco-defined attribute value group1.
hostname(config)# ldap attribute-map att_map_1
hostname(config-ldap-attribute-map)# map-name department cVPN3000-IETF-Radius-Class
hostname(config-ldap-attribute-map)# map-value department Engineering group1
hostname(config-ldap-attribute-map)#
The following commands bind the attribute map att_map_1 to the LDAP server ldap_dir_1:
hostname(config)# aaa-server ldap_dir_1 host 10.1.1.4
hostname(config-aaa-server-host)# ldap-attribute-map att_map_1
hostname(config-aaa-server-host)#
Note
The command to create an attribute map (ldap attribute-map) and the command to bind it to an LDAP
server (ldap-attribute-map) differ only by a hyphen and the mode.
The following commands display or clear all LDAP attribute maps in the running configuration:
hostname# show running-config all ldap attribute-map
hostname(config)# clear configuration ldap attribute-map
hostname(config)#
The names of frequently mapped Cisco LDAP attributes and the type of user-defined attributes they
would commonly be mapped to include:
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cVPN3000-IETF-Radius-Class — Department or user group
cVPN3000-IETF-Radius-Filter-Id — Access control list
cVPN3000-IETF-Radius-Framed-IP-Address — A static IP address
cVPN3000-IPSec-Banner1 — A organization title
cVPN3000-Tunneling-Protocols — Allow or deny dial-in
For a list of Cisco LDAP attribute names and values, see Appendix E, “Configuring an External Server
for Authorization and Authentication”. Alternatively, you can enter “?” within ldap-attribute-map mode
to display the complete list of Cisco LDAP attribute names, as shown in the following example:
hostname(config)# ldap attribute-map att_map_1
hostname(config-ldap-attribute-map)# map-name att_map_1 ?
ldap mode commands/options:
cisco-attribute-names:
cVPN3000-Access-Hours
cVPN3000-Allow-Network-Extension-Mode
cVPN3000-Auth-Service-Type
cVPN3000-Authenticated-User-Idle-Timeout
cVPN3000-Authorization-Required
cVPN3000-Authorization-Type
:
:
cVPN3000-X509-Cert-Data
hostname(config-ldap-attribute-map)#
SSO Support for WebVPN with HTTP Forms
The security appliance can use the HTTP Form protocol for single sign-on (SSO) authentication of
WebVPN users only. Single sign-on support lets WebVPN users enter a username and password only
once to access multiple protected services and Web servers. The WebVPN server running on the security
appliance acts as a proxy for the user to the authenticating server. When a user logs in, the WebVPN
server sends an SSO authentication request, including username and password, to the authenticating
server using HTTPS. If the server approves the authentication request, it returns an SSO authentication
cookie to the WebVPN server. The security appliance keeps this cookie on behalf of the user and uses it
to authenticate the user to secure websites within the domain protected by the SSO server.
In addition to the HTTP Form protocol, WebVPN administrators can choose to configure SSO with the
HTTP Basic and NTLM authentication protocols (the auto-signon command), or with Computer
Associates eTrust SiteMinder SSO server (formerly Netegrity SiteMinder) as well. For an in-depth
discussion of configuring SSO with either HTTP Forms, auto-signon or SiteMinder, see the Configuring
WebVPN chapter.
Local Database Support
The security appliance maintains a local database that you can populate with user profiles.
This section contains the following topics:
•
User Profiles, page 13-10
•
Fallback Support, page 13-10
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User Profiles
User profiles contain, at a minimum, a username. Typically, a password is assigned to each username,
although passwords are optional.
The username attributes command lets you enter the username mode. In this mode, you can add other
information to a specific user profile. The information you can add includes VPN-related attributes, such
as a VPN session timeout value.
Fallback Support
The local database can act as a fallback method for several functions. This behavior is designed to help
you prevent accidental lockout from the security appliance.
For users who need fallback support, we recommend that their usernames and passwords in the local
database match their usernames and passwords in the AAA servers. This provides transparent fallback
support. Because the user cannot determine whether a AAA server or the local database is providing the
service, using usernames and passwords on AAA servers that are different than the usernames and
passwords in the local database means that the user cannot be certain which username and password
should be given.
The local database supports the following fallback functions:
•
Console and enable password authentication—When you use the aaa authentication console
command, you can add the LOCAL keyword after the AAA server group tag. If the servers in the
group all are unavailable, the security appliance uses the local database to authenticate
administrative access. This can include enable password authentication, too.
•
Command authorization—When you use the aaa authorization command command, you can
add the LOCAL keyword after the AAA server group tag. If the TACACS+ servers in the group all
are unavailable, the local database is used to authorize commands based on privilege levels.
•
VPN authentication and authorization—VPN authentication and authorization are supported to
enable remote access to the security appliance if AAA servers that normally support these VPN
services are unavailable. The authentication-server-group command, available in tunnel-group
general attributes mode, lets you specify the LOCAL keyword when you are configuring attributes
of a tunnel group. When VPN client of an administrator specifies a tunnel group configured to
fallback to the local database, the VPN tunnel can be established even if the AAA server group is
unavailable, provided that the local database is configured with the necessary attributes.
Configuring the Local Database
This section describes how to manage users in the local database. You can use the local database for
CLI access authentication, privileged mode authentication, command authorization, network access
authentication, and VPN authentication and authorization. You cannot use the local database for network
access authorization. The local database does not support accounting.
For multiple context mode, you can configure usernames in the system execution space to provide
individual logins using the login command; however, you cannot configure any aaa commands in the
system execution space.
Caution
If you add to the local database users who can gain access to the CLI but who should not be allowed to
enter privileged mode, enable command authorization. (See the “Configuring Local Command
Authorization” section on page 40-8.) Without command authorization, users can access privileged
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mode (and all commands) at the CLI using their own password if their privilege level is 2 or greater (2 is
the default). Alternatively, you can use RADIUS or TACACS+ authentication so that the user cannot use
the login command, or you can set all local users to level 1 so you can control who can use the system
enable password to access privileged mode.
To define a user account in the local database, perform the following steps:
Step 1
Create the user account. To do so, enter the following command:
hostname(config)# username name {nopassword | password password [mschap]} [privilege
priv_level]
where the options are as follows:
•
username—A string from 4 to 64 characters long.
•
password password—A string from 3 to 16 characters long.
•
mschap—Specifies that the password will be converted to unicode and hashed using MD4 after you
enter it. Use this keyword if users are authenticated using MSCHAPv1 or MSCHAPv2.
•
privilege level—The privilege level that you want to assign to the new user account (from 0 to 15).
The default is 2. This privilege level is used with command authorization.
•
nopassword—Creates a user account with no password.
The encrypted and nt-encrypted keywords are typically for display only. When you define a password
in the username command, the security appliance encrypts it when it saves it to the configuration for
security purposes. When you enter the show running-config command, the username command does
not show the actual password; it shows the encrypted password followed by the encrypted or
nt-encrypted keyword (when you specify mschap). For example, if you enter the password “test,” the
show running-config display would appear to be something like the following:
username pat password DLaUiAX3l78qgoB5c7iVNw== nt-encrypted
The only time you would actually enter the encrypted or nt-encrypted keyword at the CLI is if you are
cutting and pasting a configuration to another security appliance and you are using the same password.
Step 2
To configure a local user account with VPN attributes, follow these steps:
a.
Enter the following command:
hostname(config)# username username attributes
When you enter a username attributes command, you enter username mode. The commands
available in this mode are as follows:
•
group-lock
•
password-storage
•
vpn-access-hours
•
vpn-filter
•
vpn-framed-ip-address
•
vpn-group-policy
•
vpn-idle-timeout
•
vpn-session-timeout
•
vpn-simultaneous-logins
•
vpn-tunnel-protocol
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•
webvpn
Use these commands as needed to configure the user profile. For more information about these
commands, see the Cisco Security Appliance Command Reference.
b.
When you have finished configuring the user profiles, enter exit to return to config mode.
For example, the following command assigns a privilege level of 15 to the admin user account:
hostname(config)# username admin password passw0rd privilege 15
The following command creates a user account with no password:
hostname(config)# username bcham34 nopassword
The following commands creates a user account with a password, enters username mode, and specifies
a few VPN attributes:
hostname(config)# username
hostname(config)# username
hostname(config-username)#
hostname(config-username)#
hostname(config-username)#
rwilliams password gOgeOus
rwilliams attributes
vpn-tunnel-protocol IPSec
vpn-simultaneous-logins 6
exit
Identifying AAA Server Groups and Servers
If you want to use an external AAA server for authentication, authorization, or accounting, you must first
create at least one AAA server group per AAA protocol and add one or more servers to each group. You
identify AAA server groups by name. Each server group is specific to one type of server: Kerberos,
LDAP, NT, RADIUS, SDI, or TACACS+.
The security appliance contacts the first server in the group. If that server is unavailable, the security
appliance contacts the next server in the group, if configured. If all servers in the group are unavailable,
the security appliance tries the local database if you configured it as a fallback method (management
authentication and authorization only). If you do not have a fallback method, the security appliance
continues to try the AAA servers.
To create a server group and add AAA servers to it, follow these steps:
Step 1
For each AAA server group you need to create, follow these steps:
a.
Identify the server group name and the protocol. To do so, enter the following command:
hostname(config)# aaa-server server_group protocol {kerberos | ldap | nt | radius |
sdi | tacacs+}
For example, to use RADIUS to authenticate network access and TACACS+ to authenticate CLI
access, you need to create at least two server groups, one for RADIUS servers and one for TACACS+
servers.
You can have up to 15 single-mode server groups or 4 multi-mode server groups. Each server group
can have up to 16 servers in single mode or up to 4 servers in multi-mode.
When you enter a aaa-server protocol command, you enter group mode.
b.
If you want to specify the maximum number of requests sent to a AAA server in the group before
trying the next server, enter the following command:
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hostname(config-aaa-server-group)# max-failed-attempts number
The number can be between 1 and 5. The default is 3.
If you configured a fallback method using the local database (for management access only; see the
“Configuring AAA for System Administrators” section on page 40-5 and the “Configuring
TACACS+ Command Authorization” section on page 40-11 to configure the fallback mechanism),
and all the servers in the group fail to respond, then the group is considered to be unresponsive, and
the fallback method is tried. The server group remains marked as unresponsive for a period of 10
minutes (by default) so that additional AAA requests within that period do not attempt to contact
the server group, and the fallback method is used immediately. To change the unresponsive period
from the default, see the reactivation-mode command in the following step.
If you do not have a fallback method, the security appliance continues to retry the servers in the
group.
c.
If you want to specify the method (reactivation policy) by which failed servers in a group are
reactivated, enter the following command:
hostname(config-aaa-server-group)# # reactivation-mode {depletion [deadtime minutes] |
timed}
Where the depletion keyword reactivates failed servers only after all of the servers in the group are
inactive.
The deadtime minutes argument specifies the amount of time in minutes, between 0 and 1440, that
elapses between the disabling of the last server in the group and the subsequent re-enabling of all
servers. The default is 10 minutes.
The timed keyword reactivates failed servers after 30 seconds of down time.
d.
If you want to send accounting messages to all servers in the group (RADIUS or TACACS+ only),
enter the following command:
hostname(config-aaa-server-group)# accounting-mode simultaneous
To restore the default of sending messages only to the active server, enter the accounting-mode
single command.
Step 2
For each AAA server on your network, follow these steps:
a.
Identify the server, including the AAA server group it belongs to. To do so, enter the following
command:
hostname(config)# aaa-server server_group (interface_name) host server_ip
When you enter a aaa-server host command, you enter host mode.
b.
As needed, use host mode commands to further configure the AAA server.
The commands in host mode do not apply to all AAA server types. Table 13-2 lists the available
commands, the server types they apply to, and whether a new AAA server definition has a default
value for that command. Where a command is applicable to the server type you specified and no
default value is provided (indicated by “—”), use the command to specify the value. For more
information about these commands, see the Cisco Security Appliance Command Reference.
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Identifying AAA Server Groups and Servers
Table 13-2
Host Mode Commands, Server Types, and Defaults
Command
Applicable AAA Server Types Default Value
accounting-port
RADIUS
1646
acl-netmask-convert
RADIUS
standard
authentication-port
RADIUS
1645
kerberos-realm
Kerberos
—
key
RADIUS
—
TACACS+
—
ldap-attribute-map
LDAP
—
ldap-base-dn
LDAP
—
ldap-login-dn
LDAP
—
ldap-login-password
LDAP
—
ldap-naming-attribute
LDAP
—
ldap-over-ssl
LDAP
—
ldap-scope
LDAP
—
nt-auth-domain-controller NT
—
radius-common-pw
RADIUS
—
retry-interval
Kerberos
10 seconds
RADIUS
10 seconds
SDI
10 seconds
sasl-mechanism
LDAP
—
server-port
Kerberos
88
LDAP
389
NT
139
SDI
5500
TACACS+
49
server-type
LDAP
auto-discovery
timeout
All
10 seconds
Example 13-1 shows commands that add one TACACS+ group with one primary and one backup server,
one RADIUS group with a single server, and an NT domain server.
Example 13-1 Multiple AAA Server Groups and Servers
hostname(config)# aaa-server AuthInbound protocol tacacs+
hostname(config-aaa-server-group)# max-failed-attempts 2
hostname(config-aaa-server-group)# reactivation-mode depletion deadtime 20
hostname(config-aaa-server-group)# exit
hostname(config)# aaa-server AuthInbound (inside) host 10.1.1.1
hostname(config-aaa-server-host)# key TACPlusUauthKey
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Using Certificates and User Login Credentials
hostname(config-aaa-server-host)# exit
hostname(config)# aaa-server AuthInbound (inside) host 10.1.1.2
hostname(config-aaa-server-host)# key TACPlusUauthKey2
hostname(config-aaa-server-host)# exit
hostname(config)# aaa-server AuthOutbound protocol radius
hostname(config-aaa-server-group)# exit
hostname(config)# aaa-server AuthOutbound (inside) host 10.1.1.3
hostname(config-aaa-server-host)# key RadUauthKey
hostname(config-aaa-server-host)# exit
hostname(config)# aaa-server NTAuth protocol nt
hostname(config-aaa-server-group)# exit
hostname(config)# aaa-server NTAuth (inside) host 10.1.1.4
hostname(config-aaa-server-host)# nt-auth-domain-controller primary1
hostname(config-aaa-server-host)# exit
Example 13-2 shows commands that configure a Kerberos AAA server group named watchdogs, add a
AAA server to the group, and define the Kerberos realm for the server. Because Example 13-2 does not
define a retry interval or the port that the Kerberos server listens to, the security appliance uses the
default values for these two server-specific parameters. Table 13-2 lists the default values for all AAA
server host mode commands.
Note
Kerberos realm names use numbers and upper-case letters only. Although the security appliance accepts
lower-case letters for a realm name, it does not translate lower-case letters to upper-case letters. Be sure
to use upper-case letters only.
Example 13-2 Kerberos Server Group and Server
hostname(config)# aaa-server watchdogs protocol kerberos
hostname(config-aaa-server-group)# aaa-server watchdogs host 192.168.3.4
hostname(config-aaa-server-host)# kerberos-realm EXAMPLE.COM
hostname(config-aaa-server-host)# exit
hostname(config)#
Using Certificates and User Login Credentials
The following section describes the different methods of using certificates and user login credentials
(username and password) for authentication and authorization. This applies to both IPSec and WebVPN.
In all cases, LDAP authorization does not use the password as a credential. RADIUS authorization uses
either a common password for all users or the username as a password.
Using User Login Credentials
The default method for authentication and authorization uses the user login credentials.
•
Authentication
– Enabled by authentication server group setting
– Uses the username and password as credentials
•
Authorization
– Enabled by authorization server group setting
– Uses the username as a credential
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Supporting a Zone Labs Integrity Server
Using certificates
If user digital certificates are configured, the security appliance first validates the certificate. It does not,
however, use any of the DNs from the certificates as a username for the authentication.
If both authentication and authorization are enabled, the security appliance uses the user login
credentials for both user authentication and authorization.
•
Authentication
– Enabled by authentication server group setting
– Uses the username and password as credentials
•
Authorization
– Enabled by authorization server group setting
– Uses the username as a credential
If authentication is disabled and authorization is enabled, the security appliance uses the primary DN
field for authorization.
•
Authentication
– DISABLED (set to None) by authentication server group setting
– No credentials used
•
Authorization
– Enabled by authorization server group setting
– Uses the username value of the certificate primary DN field as a credential
Note
If the primary DN field is not present in the certificate, the security appliance uses the secondary DN
field value as the username for the authorization request.
For example, consider a user certificate that contains the following Subject DN fields and values:
Cn=anyuser,OU=sales;O=XYZCorporation;L=boston;S=mass;C=us;[email protected] .
If the Primary DN = EA (E-mail Address) and the Secondary DN = CN (Common Name), then the
username used in the authorization request would be [email protected]
Supporting a Zone Labs Integrity Server
This section introduces the Zone Labs Integrity Server, also called Check Point Integrity Server, and
presents an example procedure for configuring the security appliance to support the Zone Labs Integrity
Server. The Integrity server is a central management station for configuring and enforcing security
policies on remote PCs. If a remote PC does not conform to the security policy dictated by the Integrity
Server, it will not be granted access to the private network protected by the Integrity Server and security
appliance.
This section includes the following topics:
•
Overview of Integrity Server and Security Appliance Interaction, page 13-17
•
Configuring Integrity Server Support, page 13-17
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Supporting a Zone Labs Integrity Server
Overview of Integrity Server and Security Appliance Interaction
The VPN client software and the Integrity client software are co-resident on a remote PC. The following
steps summarize the actions of the remote PC, security appliance, and Integrity server in the
establishment of a session between the PC and the enterprise private network:
Note
1.
The VPN client software (residing on the same remote PC as the Integrity client software) connects
to the security appliance and tells the security appliance what type of firewall client it is.
2.
Once it approves the client firewall type, the security appliance passes Integrity server address
information back to the Integrity client.
3.
With the security appliance acting as a proxy, the Integrity client establishes a restricted connection
with the Integrity server. A restricted connection is only between the Integrity client and server.
4.
The Integrity server determines if the Integrity client is in compliance with the mandated security
policies. If the client is in compliance with security policies, the Integrity server instructs the
security appliance to open the connection and provide the client with connection details.
5.
On the remote PC, the VPN client passes connection details to the Integrity client and signals that
policy enforcement should begin immediately and the client can no enter the private network.
6.
Once the connection is established, the server continues to monitor the state of the client using client
heartbeat messages.
The current release of the security appliance supports one Integrity Server at a time even though the user
interfaces support the configuration of up to five Integrity Servers. If the active Server fails, configure
another Integrity Server on the security appliance and then reestablish the client VPN session.
Configuring Integrity Server Support
This section describes an example procedure for configuring the security appliance to support the Zone
Labs Integrity Servers. The procedure involves configuring address, port, connection fail timeout and
fail states, and SSL certificate parameters.
First, you must configure the hostname or IP address of the Integrity server. The following example
commands, entered in global configuration mode, configure an Integrity server using the IP address
10.0.0.5. They also specify port 300 (the default port is 5054) and the inside interface for
communications with the Integrity server.
hostname(config)# zonelabs-integrity server-address 10.0.0.5
hostname(config)# zonelabs-integrity port 300
hostname(config)# zonelabs-integrity interface inside
hostname(config)#
If the connection between the security appliance and the Integrity server fails, the VPN client
connections remain open by default so that the enterprise VPN is not disrupted by the failure of an
Integrity server. However, you may want to close the VPN connections if the Zone Labs Integrity Server
fails. The following commands ensure that the security appliance waits 12 seconds for a response from
either the active or standby Integrity servers before declaring an the Integrity server as failed and closing
the VPN client connections:
hostname(config)# zonelabs-integrity fail-timeout 12
hostname(config)# zonelabs-integrity fail-close
hostname(config)#
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Supporting a Zone Labs Integrity Server
The following command returns the configured VPN client connection fail state to the default and
ensures the client connections remain open:
hostname(config)# zonelabs-integrity fail-open
hostname(config)#
The following example commands specify that the Integrity server connects to port 300 (default is port
80) on the security appliance to request the server SSL certificate. While the server SSL certificate is
always authenticated, these commands also specify that the client SSL certificate of the Integrity server
be authenticated.
hostname(config)# zonelabs-integrity ssl-certificate-port 300
hostname(config)# zonelabs-integrity ssl-client-authentication
hostname(config)#
To set the firewall client type to the Zone Labs Integrity type, use the client-firewall command as
described in the “Configuring Firewall Policies” section on page 30-54. The command arguments that
specify firewall policies are not used when the firewall type is zonelabs-integrity because the Integrity
server determines the policies.
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14
Configuring Failover
This chapter describes the security appliance failover feature, which lets you configure two security
appliances so that one takes over operation if the other one fails.
Note
The ASA 5505 series adaptive security appliance does not support Stateful Failover or Active/Active
failover.
This chapter includes the following sections:
•
Understanding Failover, page 14-1
•
Configuring Failover, page 14-18
•
Controlling and Monitoring Failover, page 14-49
For failover configuration examples, see Appendix B, “Sample Configurations.”
Understanding Failover
The failover configuration requires two identical security appliances connected to each other through a
dedicated failover link and, optionally, a Stateful Failover link. The health of the active interfaces and
units is monitored to determine if specific failover conditions are met. If those conditions are met,
failover occurs.
The security appliance supports two failover configurations, Active/Active failover and Active/Standby
failover. Each failover configuration has its own method for determining and performing failover.
With Active/Active failover, both units can pass network traffic. This lets you configure load balancing
on your network. Active/Active failover is only available on units running in multiple context mode.
With Active/Standby failover, only one unit passes traffic while the other unit waits in a standby state.
Active/Standby failover is available on units running in either single or multiple context mode.
Both failover configurations support stateful or stateless (regular) failover.
Note
VPN failover is not supported on units running in multiple context mode. VPN failover available for
Active/Standby failover configurations only.
This section includes the following topics:
•
Failover System Requirements, page 14-2
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Configuring Failover
Understanding Failover
•
The Failover and Stateful Failover Links, page 14-3
•
Active/Active and Active/Standby Failover, page 14-6
•
Regular and Stateful Failover, page 14-15
•
Failover Health Monitoring, page 14-16
•
Failover Feature/Platform Matrix, page 14-17
•
Failover Times by Platform, page 14-18
Failover System Requirements
This section describes the hardware, software, and license requirements for security appliances in a
failover configuration. This section contains the following topics:
•
Hardware Requirements, page 14-2
•
Software Requirements, page 14-2
•
License Requirements, page 14-2
Hardware Requirements
The two units in a failover configuration must have the same hardware configuration. They must be the
same model, have the same number and types of interfaces, and the same amount of RAM.
Note
The two units do not have to have the same size Flash memory. If using units with different Flash
memory sizes in your failover configuration, make sure the unit with the smaller Flash memory has
enough space to accommodate the software image files and the configuration files. If it does not,
configuration synchronization from the unit with the larger Flash memory to the unit with the smaller
Flash memory will fail.
Software Requirements
The two units in a failover configuration must be in the operating modes (routed or transparent, single
or multiple context). They have the same major (first number) and minor (second number) software
version. However, you can use different versions of the software during an upgrade process; for example,
you can upgrade one unit from Version 7.0(1) to Version 7.0(2) and have failover remain active. We
recommend upgrading both units to the same version to ensure long-term compatibility.
See “Performing Zero Downtime Upgrades for Failover Pairs” section on page 41-6 for more
information about upgrading the software on a failover pair.
License Requirements
On the PIX 500 series security appliance, at least one of the units must have an unrestricted (UR) license.
The other unit can have a Failover Only (FO) license, a Failover Only Active-Active (FO_AA) license,
or another UR license. Units with a Restricted license cannot be used for failover, and two units with FO
or FO_AA licenses cannot be used together as a failover pair.
Note
The FO license does not support Active/Active failover.
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Understanding Failover
The FO and FO_AA licenses are intended to be used solely for units in a failover configuration and not
for units in standalone mode. If a failover unit with one of these licenses is used in standalone mode, the
unit reboots at least once every 24 hours until the unit is returned to failover duty. A unit with an FO or
FO_AA license operates in standalone mode if it is booted without being connected to a failover peer
with a UR license. If the unit with a UR license in a failover pair fails and is removed from the
configuration, the unit with the FO or FO_AA license does not automatically reboot every 24 hours; it
operates uninterrupted unless the it is manually rebooted.
When the unit automatically reboots, the following message displays on the console:
=========================NOTICE=========================
This machine is running in secondary mode without
a connection to an active primary PIX. Please
check your connection to the primary system.
REBOOTING....
========================================================
The ASA 5500 series adaptive security appliance platform does not have this restriction.
The Failover and Stateful Failover Links
This section describes the failover and the Stateful Failover links, which are dedicated connections
between the two units in a failover configuration. This section includes the following topics:
•
Failover Link, page 14-3
•
Stateful Failover Link, page 14-5
Failover Link
The two units in a failover pair constantly communicate over a failover link to determine the operating
status of each unit. The following information is communicated over the failover link:
Caution
•
The unit state (active or standby).
•
Power status (cable-based failover only—available only on the PIX 500 series security appliance).
•
Hello messages (keep-alives).
•
Network link status.
•
MAC address exchange.
•
Configuration replication and synchronization.
All information sent over the failover and Stateful Failover links is sent in clear text unless you secure
the communication with a failover key. If the security appliance is used to terminate VPN tunnels, this
information includes any usernames, passwords and preshared keys used for establishing the tunnels.
Transmitting this sensitive data in clear text could pose a significant security risk. We recommend
securing the failover communication with a failover key if you are using the security appliance to
terminate VPN tunnels.
On the PIX 500 series security appliance, the failover link can be either a LAN-based connection or a
dedicated serial Failover cable. On the ASA 5500 series adaptive security appliance, the failover link can
only be a LAN-based connection.
This section includes the following topics:
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Understanding Failover
•
LAN-Based Failover Link, page 14-4
•
Serial Cable Failover Link (PIX Security Appliance Only), page 14-4
LAN-Based Failover Link
You can use any unused Ethernet interface on the device as the failover link. You cannot specify an
interface that is currently configured with a name. The failover link interface is not configured as a
normal networking interface; it exists only for failover communication. This interface should only be
used for the failover link (and optionally for the Stateful Failover link). You can connect the LAN-based
failover link by using a dedicated switch with no hosts or routers on the link or by using a crossover
Ethernet cable to link the units directly.
Note
When using VLANs, use a dedicated VLAN for the failover link. Sharing the failover link VLAN with
any other VLANs can cause intermittent traffic problems and ping and ARP failures. If you use a switch
to connect the failover link, use dedicated interfaces on the switch and security appliance for the failover
link; do not share the interface with subinterfaces carrying regular network traffic.
On systems running in multiple context mode, the failover link resides in the system context. This
interface and the Stateful Failover link, if used, are the only interfaces that you can configure in the
system context. All other interfaces are allocated to and configured from within security contexts.
Note
The IP address and MAC address for the failover link do not change at failover.
Serial Cable Failover Link (PIX Security Appliance Only)
The serial Failover cable, or “cable-based failover,” is only available on the PIX 500 series security
appliance. If the two units are within six feet of each other, then we recommend that you use the serial
Failover cable.
The cable that connects the two units is a modified RS-232 serial link cable that transfers data at
117,760 bps (115 Kbps). One end of the cable is labeled “Primary”. The unit attached to this end of the
cable automatically becomes the primary unit. The other end of the cable is labeled “Secondary”. The
unit attached to this end of the cable automatically becomes the secondary unit. You cannot override
these designations in the PIX 500 series security appliance software. If you purchased a PIX 500 series
security appliance failover bundle, this cable is included. To order a spare, use part number PIX-FO=.
The benefits of using cable-based failover include:
•
The PIX 500 series security appliance can immediately detect a power loss on the peer unit and
differentiate between a power loss from an unplugged cable.
•
The standby unit can communicate with the active unit and can receive the entire configuration
without having to be bootstrapped for failover. In LAN-based failover you need to configure the
failover link on the standby unit before it can communicate with the active unit.
•
The switch between the two units in LAN-based failover can be another point of hardware failure;
cable-based failover eliminates this potential point of failure.
•
You do not have to dedicate an Ethernet interface (and switch) to the failover link.
•
The cable determines which unit is primary and which is secondary, eliminating the need to
manually enter that information in the unit configurations.
The disadvantages include:
•
Distance limitation—the units cannot be separated by more than 6 feet.
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Understanding Failover
•
Slower configuration replication.
Stateful Failover Link
To use Stateful Failover, you must configure a Stateful Failover link to pass all state information. You
have three options for configuring a Stateful Failover link:
•
You can use a dedicated Ethernet interface for the Stateful Failover link.
•
If you are using LAN-based failover, you can share the failover link.
•
You can share a regular data interface, such as the inside interface. However, this option is not
recommended.
If you are using a dedicated Ethernet interface for the Stateful Failover link, you can use either a switch
or a crossover cable to directly connect the units. If you use a switch, no other hosts or routers should be
on this link.
Note
Enable the PortFast option on Cisco switch ports that connect directly to the security appliance.
If you are using the failover link as the Stateful Failover link, you should use the fastest Ethernet
interface available. If you experience performance problems on that interface, consider dedicating a
separate interface for the Stateful Failover interface.
If you use a data interface as the Stateful Failover link, you receive the following warning when you
specify that interface as the Stateful Failover link:
******* WARNING ***** WARNING ******* WARNING ****** WARNING *********
Sharing Stateful failover interface with regular data interface is not
a recommended configuration due to performance and security concerns.
******* WARNING ***** WARNING ******* WARNING ****** WARNING *********
Sharing a data interface with the Stateful Failover interface can leave you vulnerable to replay attacks.
Additionally, large amounts of Stateful Failover traffic may be sent on the interface, causing
performance problems on that network segment.
Note
Using a data interface as the Stateful Failover interface is only supported in single context, routed mode.
In multiple context mode, the Stateful Failover link resides in the system context. This interface and the
failover interface are the only interfaces in the system context. All other interfaces are allocated to and
configured from within security contexts.
Note
Caution
The IP address and MAC address for the Stateful Failover link does not change at failover unless the
Stateful Failover link is configured on a regular data interface.
All information sent over the failover and Stateful Failover links is sent in clear text unless you secure
the communication with a failover key. If the security appliance is used to terminate VPN tunnels, this
information includes any usernames, passwords and preshared keys used for establishing the tunnels.
Transmitting this sensitive data in clear text could pose a significant security risk. We recommend
securing the failover communication with a failover key if you are using the security appliance to
terminate VPN tunnels.
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Configuring Failover
Understanding Failover
Active/Active and Active/Standby Failover
This section describes each failover configuration in detail. This section includes the following topics:
•
Active/Standby Failover, page 14-6
•
Active/Active Failover, page 14-9
•
Determining Which Type of Failover to Use, page 14-14
Active/Standby Failover
This section describes Active/Standby failover and includes the following topics:
•
Active/Standby Failover Overview, page 14-6
•
Primary/Secondary Status and Active/Standby Status, page 14-6
•
Device Initialization and Configuration Synchronization, page 14-7
•
Command Replication, page 14-7
•
Failover Triggers, page 14-8
•
Failover Actions, page 14-9
Active/Standby Failover Overview
Active/Standby failover lets you use a standby security appliance to take over the functionality of a failed
unit. When the active unit fails, it changes to the standby state while the standby unit changes to the
active state. The unit that becomes active assumes the IP addresses (or, for transparent firewall, the
management IP address) and MAC addresses of the failed unit and begins passing traffic. The unit that
is now in standby state takes over the standby IP addresses and MAC addresses. Because network
devices see no change in the MAC to IP address pairing, no ARP entries change or time out anywhere
on the network.
Note
For multiple context mode, the security appliance can fail over the entire unit (including all contexts)
but cannot fail over individual contexts separately.
Primary/Secondary Status and Active/Standby Status
The main differences between the two units in a failover pair are related to which unit is active and which
unit is standby, namely which IP addresses to use and which unit actively passes traffic.
However, a few differences exist between the units based on which unit is primary (as specified in the
configuration) and which unit is secondary:
•
The primary unit always becomes the active unit if both units start up at the same time (and are of
equal operational health).
•
The primary unit MAC addresses are always coupled with the active IP addresses. The exception to
this rule occurs when the secondary unit is active, and cannot obtain the primary unit MAC addresses
over the failover link. In this case, the secondary unit MAC addresses are used.
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Understanding Failover
Device Initialization and Configuration Synchronization
Configuration synchronization occurs when one or both devices in the failover pair boot. Configurations
are always synchronized from the active unit to the standby unit. When the standby unit completes its
initial startup, it clears its running configuration (except for the failover commands needed to
communicate with the active unit), and the active unit sends its entire configuration to the standby unit.
The active unit is determined by the following:
Note
•
If a unit boots and detects a peer already running as active, it becomes the standby unit.
•
If a unit boots and does not detect a peer, it becomes the active unit.
•
If both units boot simultaneously, then the primary unit becomes the active unit and the secondary
unit becomes the standby unit.
If the secondary unit boots without detecting the primary unit, it becomes the active unit. It uses its own
MAC addresses for the active IP addresses. However, when the primary unit becomes available, the
secondary unit changes the MAC addresses to those of the primary unit, which can cause an interruption
in your network traffic. To avoid this, configure the failover pair with virtual MAC addresses. See the
“Configuring Virtual MAC Addresses” section on page 14-26 for more information.
When the replication starts, the security appliance console on the active unit displays the message
“Beginning configuration replication: Sending to mate,” and when it is complete, the security appliance
displays the message “End Configuration Replication to mate.” During replication, commands entered
on the active unit may not replicate properly to the standby unit, and commands entered on the standby
unit may be overwritten by the configuration being replicated from the active unit. Avoid entering
commands on either unit in the failover pair during the configuration replication process. Depending
upon the size of the configuration, replication can take from a few seconds to several minutes.
On the standby unit, the configuration exists only in running memory. To save the configuration to Flash
memory after synchronization:
Note
•
For single context mode, enter the write memory command on the active unit. The command is
replicated to the standby unit, which proceeds to write its configuration to Flash memory.
•
For multiple context mode, enter the write memory all command on the active unit from the system
execution space. The command is replicated to the standby unit, which proceeds to write its
configuration to Flash memory. Using the all keyword with this command causes the system and all
context configurations to be saved.
Startup configurations saved on external servers are accessible from either unit over the network and do
not need to be saved separately for each unit. Alternatively, you can copy the contexts on disk from the
active unit to an external server, and then copy them to disk on the standby unit, where they become
available when the unit reloads.
Command Replication
Command replication always flows from the active unit to the standby unit. As commands are entered
on the active unit, they are sent across the failover link to the standby unit. You do not have to save the
active configuration to Flash memory to replicate the commands.
The following commands are replicated to the standby unit:
•
all configuration commands except for the mode, firewall, and failover lan unit commands
•
copy running-config startup-config
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•
delete
•
mkdir
•
rename
•
rmdir
•
write memory
The following commands are not replicated to the standby unit:
Note
•
all forms of the copy command except for copy running-config startup-config
•
all forms of the write command except for write memory
•
debug
•
failover lan unit
•
firewall
•
mode
•
show
Changes made on the standby unit are not replicated to the active unit. If you enter a command on the
standby unit, the security appliance displays the message **** WARNING **** Configuration
Replication is NOT performed from Standby unit to Active unit. Configurations are no
longer synchronized.
This message displays even when you enter many commands that do not affect
the configuration.
If you enter the write standby command on the active unit, the standby unit clears its running
configuration (except for the failover commands used to communicate with the active unit), and the
active unit sends its entire configuration to the standby unit.
For multiple context mode, when you enter the write standby command in the system execution space,
all contexts are replicated. If you enter the write standby command within a context, the command
replicates only the context configuration.
Replicated commands are stored in the running configuration. To save the replicated commands to the
Flash memory on the standby unit:
•
For single context mode, enter the copy running-config startup-config command on the active unit.
The command is replicated to the standby unit, which proceeds to write its configuration to Flash
memory.
•
For multiple context mode, enter the copy running-config startup-config command on the active
unit from the system execution space and within each context on disk. The command is replicated
to the standby unit, which proceeds to write its configuration to Flash memory. Contexts with startup
configurations on external servers are accessible from either unit over the network and do not need
to be saved separately for each unit. Alternatively, you can copy the contexts on disk from the active
unit to an external server, and then copy them to disk on the standby unit.
Failover Triggers
The unit can fail if one of the following events occurs:
•
The unit has a hardware failure or a power failure.
•
The unit has a software failure.
•
Too many monitored interfaces fail.
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•
The no failover active command is entered on the active unit or the failover active command is
entered on the standby unit.
Failover Actions
In Active/Standby failover, failover occurs on a unit basis. Even on systems running in multiple context
mode, you cannot fail over individual or groups of contexts.
Table 14-1 shows the failover action for each failure event. For each failure event, the table shows the
failover policy (failover or no failover), the action taken by the active unit, the action taken by the
standby unit, and any special notes about the failover condition and actions.
Table 14-1
Failover Behavior
Failure Event
Policy
Active Action
Standby Action
Notes
Active unit failed (power or
hardware)
Failover
n/a
Become active
No hello messages are received on
any monitored interface or the
failover link.
Formerly active unit recovers
No failover
Become standby
No action
None.
Standby unit failed (power or No failover
hardware)
Mark standby as
failed
n/a
When the standby unit is marked as
failed, then the active unit does not
attempt to fail over, even if the
interface failure threshold is
surpassed.
Failover link failed during
operation
No failover
Mark failover
interface as failed
Mark failover
interface as failed
You should restore the failover link
as soon as possible because the
unit cannot fail over to the standby
unit while the failover link is down.
Failover link failed at startup
No failover
Mark failover
interface as failed
Become active
If the failover link is down at
startup, both units become active.
Stateful Failover link failed
No failover
No action
No action
State information becomes out of
date, and sessions are terminated if
a failover occurs.
Interface failure on active unit Failover
above threshold
Mark active as
failed
Become active
None.
Interface failure on standby
unit above threshold
No action
Mark standby as
failed
When the standby unit is marked as
failed, then the active unit does not
attempt to fail over even if the
interface failure threshold is
surpassed.
Mark active as
failed
No failover
Active/Active Failover
This section describes Active/Active failover. This section includes the following topics:
•
Active/Active Failover Overview, page 14-10
•
Primary/Secondary Status and Active/Standby Status, page 14-10
•
Device Initialization and Configuration Synchronization, page 14-11
•
Command Replication, page 14-12
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•
Failover Triggers, page 14-13
•
Failover Actions, page 14-13
Active/Active Failover Overview
Active/Active failover is only available to security appliances in multiple context mode. In an
Active/Active failover configuration, both security appliances can pass network traffic.
In Active/Active failover, you divide the security contexts on the security appliance into failover groups.
A failover group is simply a logical group of one or more security contexts. You can create a maximum
of two failover groups on the security appliance. The admin context is always a member of failover
group 1. Any unassigned security contexts are also members of failover group 1 by default.
The failover group forms the base unit for failover in Active/Active failover. Interface failure monitoring,
failover, and active/standby status are all attributes of a failover group rather than the unit. When an
active failover group fails, it changes to the standby state while the standby failover group becomes
active. The interfaces in the failover group that becomes active assume the MAC and IP addresses of the
interfaces in the failover group that failed. The interfaces in the failover group that is now in the standby
state take over the standby MAC and IP addresses.
Note
A failover group failing on a unit does not mean that the unit has failed. The unit may still have another
failover group passing traffic on it.
When creating the failover groups, you should create them on the unit that will have failover group 1 in
the active state.
Note
Active/Active failover generates virtual MAC addresses for the interfaces in each failover group. If you
have more than one Active/Active failover pair on the same network, it is possible to have the same
default virtual MAC addresses assigned to the interfaces on one pair as are assigned to the interfaces of
the other pairs because of the way the default virtual MAC addresses are determined. To avoid having
duplicate MAC addresses on your network, make sure you assign each physical interface a virtual active
and standby MAC address.
Primary/Secondary Status and Active/Standby Status
As in Active/Standby failover, one unit in an Active/Active failover pair is designated the primary unit,
and the other unit the secondary unit. Unlike Active/Standby failover, this designation does not indicate
which unit becomes active when both units start simultaneously. Instead, the primary/secondary
designation does two things:
•
Determines which unit provides the running configuration to the pair when they boot
simultaneously.
•
Determines on which unit each failover group appears in the active state when the units boot
simultaneously. Each failover group in the configuration is configured with a primary or secondary
unit preference. You can configure both failover groups be in the active state on a single unit in the
pair, with the other unit containing the failover groups in the standby state. However, a more typical
configuration is to assign each failover group a different role preference to make each one active on
a different unit, distributing the traffic across the devices.
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Note
The security appliance does not provide load balancing services. Load balancing must be
handled by a router passing traffic to the security appliance.
Which unit each failover group becomes active on is determined as follows:
•
When a unit boots while the peer unit is not available, both failover groups become active on the
unit.
•
When a unit boots while the peer unit is active (with both failover groups in the active state), the
failover groups remain in the active state on the active unit regardless of the primary or secondary
preference of the failover group until one of the following:
– A failover occurs.
– You manually force the failover group to the other unit with the no failover active command.
– You configured the failover group with the preempt command, which causes the failover group
to automatically become active on the preferred unit when the unit becomes available.
•
When both units boot at the same time, each failover group becomes active on its preferred unit after
the configurations have been synchronized.
Device Initialization and Configuration Synchronization
Configuration synchronization occurs when one or both units in a failover pair boot. The configurations
are synchronized as follows:
•
When a unit boots while the peer unit is active (with both failover groups active on it), the booting
unit contacts the active unit to obtain the running configuration regardless of the primary or
secondary designation of the booting unit.
•
When both units boot simultaneously, the secondary unit obtains the running configuration from the
primary unit.
When the replication starts, the security appliance console on the unit sending the configuration displays
the message “Beginning configuration replication: Sending to mate,” and when it is complete, the
security appliance displays the message “End Configuration Replication to mate.” During replication,
commands entered on the unit sending the configuration may not replicate properly to the peer unit, and
commands entered on the unit receiving the configuration may be overwritten by the configuration being
received. Avoid entering commands on either unit in the failover pair during the configuration
replication process. Depending upon the size of the configuration, replication can take from a few
seconds to several minutes.
On the unit receiving the configuration, the configuration exists only in running memory. To save the
configuration to Flash memory after synchronization enter the write memory all command in the system
execution space on the unit that has failover group 1 in the active state. The command is replicated to
the peer unit, which proceeds to write its configuration to Flash memory. Using the all keyword with this
command causes the system and all context configurations to be saved.
Note
Startup configurations saved on external servers are accessible from either unit over the network and do
not need to be saved separately for each unit. Alternatively, you can copy the contexts configuration files
from the disk on the primary unit to an external server, and then copy them to disk on the secondary unit,
where they become available when the unit reloads.
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Command Replication
After both units are running, commands are replicated from one unit to the other as follows:
•
Note
Commands entered within a security context are replicated from the unit on which the security
context appears in the active state to the peer unit.
A context is considered in the active state on a unit if the failover group to which it belongs is
in the active state on that unit.
•
Commands entered in the system execution space are replicated from the unit on which failover
group 1 is in the active state to the unit on which failover group 1 is in the standby state.
•
Commands entered in the admin context are replicated from the unit on which failover group 1 is in
the active state to the unit on which failover group 1 is in the standby state.
All configuration and file commands (copy, rename, delete, mkdir, rmdir, and so on) are replicated,
with the following exceptions. The show, debug, mode, firewall, and failover lan unit commands are
not replicated.
Failure to enter the commands on the appropriate unit for command replication to occur causes the
configurations to be out of synchronization. Those changes may be lost the next time the initial
configuration synchronization occurs.
The following commands are replicated to the standby unit:
•
all configuration commands except for the mode, firewall, and failover lan unit commands
•
copy running-config startup-config
•
delete
•
mkdir
•
rename
•
rmdir
•
write memory
The following commands are not replicated to the standby unit:
•
all forms of the copy command except for copy running-config startup-config
•
all forms of the write command except for write memory
•
debug
•
failover lan unit
•
firewall
•
mode
•
show
You can use the write standby command to resynchronize configurations that have become out of sync.
For Active/Active failover, the write standby command behaves as follows:
•
If you enter the write standby command in the system execution space, the system configuration
and the configurations for all of the security contexts on the security appliance is written to the peer
unit. This includes configuration information for security contexts that are in the standby state. You
must enter the command in the system execution space on the unit that has failover group 1 in the
active state.
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Note
•
If there are security contexts in the active state on the peer unit, the write standby command
causes active connections through those contexts to be terminated. Use the failover active
command on the unit providing the configuration to make sure all contexts are active on that
unit before entering the write standby command.
If you enter the write standby command in a security context, only the configuration for the security
context is written to the peer unit. You must enter the command in the security context on the unit
where the security context appears in the active state.
Replicated commands are not saved to the Flash memory when replicated to the peer unit. They are
added to the running configuration. To save replicated commands to Flash memory on both units, use
the write memory or copy running-config startup-config command on the unit that you made the
changes on. The command is replicated to the peer unit and cause the configuration to be saved to Flash
memory on the peer unit.
Failover Triggers
In Active/Active failover, failover can be triggered at the unit level if one of the following events occurs:
•
The unit has a hardware failure.
•
The unit has a power failure.
•
The unit has a software failure.
•
The no failover active or the failover active command is entered in the system execution space.
Failover is triggered at the failover group level when one of the following events occurs:
•
Too many monitored interfaces in the group fail.
•
The no failover active group group_id or failover active group group_id command is entered.
You configure the failover threshold for each failover group by specifying the number or percentage of
interfaces within the failover group that must fail before the group fails. Because a failover group can
contain multiple contexts, and each context can contain multiple interfaces, it is possible for all
interfaces in a single context to fail without causing the associated failover group to fail.
See the “Failover Health Monitoring” section on page 14-16 for more information about interface and
unit monitoring.
Failover Actions
In an Active/Active failover configuration, failover occurs on a failover group basis, not a system basis.
For example, if you designate both failover groups as active on the primary unit, and failover group 1
fails, then failover group 2 remains active on the primary unit while failover group 1 becomes active on
the secondary unit.
Note
When configuring Active/Active failover, make sure that the combined traffic for both units is within the
capacity of each unit.
Table 14-2 shows the failover action for each failure event. For each failure event, the policy (whether
or not failover occurs), actions for the active failover group, and actions for the standby failover group
are given.
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Table 14-2
Failover Behavior for Active/Active Failover
Active Group
Action
Standby Group
Action
Failure Event
Policy
Notes
A unit experiences a power or
software failure
Failover
Become standby Become active
Mark as failed
Mark active as
failed
When a unit in a failover pair fails,
any active failover groups on that
unit are marked as failed and
become active on the peer unit.
Interface failure on active failover
group above threshold
Failover
Mark active
group as failed
Become active
None.
Interface failure on standby failover
group above threshold
No failover No action
Mark standby
group as failed
When the standby failover group is
marked as failed, the active failover
group does not attempt to fail over,
even if the interface failure
threshold is surpassed.
Formerly active failover group
recovers
No failover No action
No action
Unless configured with the
preempt command, the failover
groups remain active on their
current unit.
Failover link failed at startup
No failover Become active
Become active
If the failover link is down at
startup, both failover groups on
both units become active.
Stateful Failover link failed
No failover No action
No action
State information becomes out of
date, and sessions are terminated if
a failover occurs.
Failover link failed during operation
No failover n/a
n/a
Each unit marks the failover
interface as failed. You should
restore the failover link as soon as
possible because the unit cannot fail
over to the standby unit while the
failover link is down.
Determining Which Type of Failover to Use
The type of failover you choose depends upon your security appliance configuration and how you plan
to use the security appliances.
If you are running the security appliance in single mode, then you can only use Active/Standby failover.
Active/Active failover is only available to security appliances running in multiple context mode.
If you are running the security appliance in multiple context mode, then you can configure either
Active/Active failover or Active/Standby failover.
•
To provide load balancing, use Active/Active failover.
•
If you do not want to provide load balancing, use Active/Standby or Active/Active failover.
Table 14-3 provides a comparison of some of the features supported by each type of failover
configuration:
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Table 14-3
Failover Configuration Feature Support
Feature
Active/Active
Active/Standby
Single Context Mode
No
Yes
Multiple Context Mode
Yes
Yes
Load Balancing Network Configurations
Yes
No
Unit Failover
Yes
Yes
Failover of Groups of Contexts
Yes
No
Failover of Individual Contexts
No
No
Regular and Stateful Failover
The security appliance supports two types of failover, regular and stateful. This section includes the
following topics:
•
Regular Failover, page 14-15
•
Stateful Failover, page 14-15
Regular Failover
When a failover occurs, all active connections are dropped. Clients need to reestablish connections when
the new active unit takes over.
Stateful Failover
When Stateful Failover is enabled, the active unit continually passes per-connection state information to
the standby unit. After a failover occurs, the same connection information is available at the new active
unit. Supported end-user applications are not required to reconnect to keep the same communication
session.
The state information passed to the standby unit includes the following:
•
NAT translation table.
•
TCP connection states.
•
UDP connection states.
•
The ARP table.
•
The Layer 2 bridge table (when running in transparent firewall mode).
•
The HTTP connection states (if HTTP replication is enabled).
•
The ISAKMP and IPSec SA table.
•
GTP PDP connection database.
The information that is not passed to the standby unit when Stateful Failover is enabled includes the
following:
•
The HTTP connection table (unless HTTP replication is enabled).
•
The user authentication (uauth) table.
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Note
•
The routing tables. After a failover occurs, some packets may be lost our routed out of the wrong
interface (the default route) while the dynamic routing protocols rediscover routes.
•
State information for Security Service Modules.
•
DHCP server address leases.
•
L2TP over IPSec sessions.
If failover occurs during an active Cisco IP SoftPhone session, the call remains active because the call
session state information is replicated to the standby unit. When the call is terminated, the IP SoftPhone
client loses connection with the Call Manager. This occurs because there is no session information for
the CTIQBE hangup message on the standby unit. When the IP SoftPhone client does not receive a
response back from the Call Manager within a certain time period, it considers the Call Manager
unreachable and unregisters itself.
Failover Health Monitoring
The security appliance monitors each unit for overall health and for interface health. See the following
sections for more information about how the security appliance performs tests to determine the state of
each unit:
•
Unit Health Monitoring, page 14-16
•
Interface Monitoring, page 14-17
Unit Health Monitoring
The security appliance determines the health of the other unit by monitoring the failover link. When a
unit does not receive three consecutive hello messages on the failover link, the unit sends an ARP request
on all interfaces, including the failover interface. The action the security appliance takes depends on the
response from the other unit. See the following possible actions:
Note
•
If the security appliance receives a response on the failover interface, then it does not fail over.
•
If the security appliance does not receive a response on the failover link, but receives a response on
another interface, then the unit does not failover. The failover link is marked as failed. You should
restore the failover link as soon as possible because the unit cannot fail over to the standby while
the failover link is down.
•
If the security appliance does not receive a response on any interface, then the standby unit switches
to active mode and classifies the other unit as failed.
If a failed unit does not recover and you believe it should not be failed, you can reset the state by entering
the failover reset command. If the failover condition persists, however, the unit will fail again.
You can configure the frequency of the hello messages and the hold time before failover occurs. A faster
poll time and shorter hold time speed the detection of unit failures and make failover occur more quickly,
but it can also cause “false” failures due to network congestion delaying the keepalive packets. See
Configuring Unit Health Monitoring, page 14-38 for more information about configuring unit health
monitoring.
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Interface Monitoring
You can monitor up to 250 interfaces divided between all contexts. You should monitor important
interfaces, for example, you might configure one context to monitor a shared interface (because the
interface is shared, all contexts benefit from the monitoring).
When a unit does not receive hello messages on a monitored interface for half of the configured hold
time, it runs the following tests:
1.
Link Up/Down test—A test of the interface status. If the Link Up/Down test indicates that the
interface is operational, then the security appliance performs network tests. The purpose of these
tests is to generate network traffic to determine which (if either) unit has failed. At the start of each
test, each unit clears its received packet count for its interfaces. At the conclusion of each test, each
unit looks to see if it has received any traffic. If it has, the interface is considered operational. If one
unit receives traffic for a test and the other unit does not, the unit that received no traffic is
considered failed. If neither unit has received traffic, then the next test is used.
2.
Network Activity test—A received network activity test. The unit counts all received packets for up
to 5 seconds. If any packets are received at any time during this interval, the interface is considered
operational and testing stops. If no traffic is received, the ARP test begins.
3.
ARP test—A reading of the unit ARP cache for the 2 most recently acquired entries. One at a time,
the unit sends ARP requests to these machines, attempting to stimulate network traffic. After each
request, the unit counts all received traffic for up to 5 seconds. If traffic is received, the interface is
considered operational. If no traffic is received, an ARP request is sent to the next machine. If at the
end of the list no traffic has been received, the ping test begins.
4.
Broadcast Ping test—A ping test that consists of sending out a broadcast ping request. The unit then
counts all received packets for up to 5 seconds. If any packets are received at any time during this
interval, the interface is considered operational and testing stops.
If all network tests fail for an interface, but this interface on the other unit continues to successfully pass
traffic, then the interface is considered to be failed. If the threshold for failed interfaces is met, then a
failover occurs. If the other unit interface also fails all the network tests, then both interfaces go into the
“Unknown” state and do not count towards the failover limit.
An interface becomes operational again if it receives any traffic. A failed security appliance returns to
standby mode if the interface failure threshold is no longer met.
Note
If a failed unit does not recover and you believe it should not be failed, you can reset the state by entering
the failover reset command. If the failover condition persists, however, the unit will fail again.
Failover Feature/Platform Matrix
Table 14-4 shows the failover features supported by each hardware platform.
Table 14-4
Failover Feature Support by Platform
Platform
Cable-Base Failover
LAN-Based Failover
Stateful Failover
ASA 5505 series adaptive
security appliance
No
Yes
No
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Table 14-4
Failover Feature Support by Platform
Platform
Cable-Base Failover
LAN-Based Failover
Stateful Failover
ASA 5500 series adaptive
security appliance (other than
the ASA 5505)
No
Yes
Yes
PIX 500 series security
appliance
Yes
Yes
Yes
Failover Times by Platform
Table 14-5 shows the minimum, default, and maximum failover times for the PIX 500 series security
appliance.
Table 14-5
PIX 500 series security appliance failover times.
Failover Condition
Minimum
Default
Maximum
Active unit loses power or stops normal operation.
800 milliseconds
45 seconds
45 seconds
Active unit interface link down.
500 milliseconds
5 seconds
15 seconds
Active unit interface up, but connection problem
causes interface testing.
5 seconds
25 seconds
75 seconds
Table 14-6 shows the minimum, default, and maximum failover times for the ASA 5500 series adaptive
security appliance.
Table 14-6
ASA 5500 series adaptive security appliance failover times.
Failover Condition
Minimum
Default
Maximum
Active unit loses power or stops normal operation.
800 milliseconds
15 seconds
45 seconds
Active unit main board interface link down.
500 milliseconds
5 seconds
15 seconds
Active unit 4GE card interface link down.
2 seconds
5 seconds
15 seconds
Active unit IPS or CSC card fails.
2 seconds
2 seconds
2 seconds
Active unit interface up, but connection problem
causes interface testing.
5 seconds
25 seconds
75 seconds
Configuring Failover
This section describes how to configure failover and includes the following topics:
•
Failover Configuration Limitations, page 14-19
•
Configuring Active/Standby Failover, page 14-19
•
Configuring Active/Active Failover, page 14-26
•
Configuring Unit Health Monitoring, page 14-38
•
Configuring Failover Communication Authentication/Encryption, page 14-39
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•
Verifying the Failover Configuration, page 14-39
Failover Configuration Limitations
You cannot configure failover with the following type of IP addresses:
•
IP addresses obtained through DHCP
•
IP addresses obtained through PPPoE
•
IPv6 addresses
Additionally, the following restrictions apply:
•
Stateful Failover is not supported on the ASA 5505 adaptive security appliance.
•
Active/Active failover is not supported on the ASA 5505 adaptive security appliance.
•
You cannot configure failover when Easy VPN Remote is enabled on the ASA 5505 adaptive
security appliance.
•
VPN failover is not supported in multiple context mode.
Configuring Active/Standby Failover
This section provides step-by-step procedures for configuring Active/Standby failover. This section
includes the following topics:
•
Prerequisites, page 14-19
•
Configuring Cable-Based Active/Standby Failover (PIX Security Appliance Only), page 14-19
•
Configuring LAN-Based Active/Standby Failover, page 14-21
•
Configuring Optional Active/Standby Failover Settings, page 14-24
Prerequisites
Before you begin, verify the following:
•
Both units have the same hardware, software configuration, and proper license.
•
Both units are in the same mode (single or multiple, transparent or routed).
Configuring Cable-Based Active/Standby Failover (PIX Security Appliance Only)
Follow these steps to configure Active/Standby failover using a serial cable as the failover link. The
commands in this task are entered on the primary unit in the failover pair. The primary unit is the unit
that has the end of the cable labeled “Primary” plugged into it. For devices in multiple context mode, the
commands are entered in the system execution space unless otherwise noted.
You do not need to bootstrap the secondary unit in the failover pair when you use cable-based failover.
Leave the secondary unit powered off until instructed to power it on.
Cable-based failover is only available on the PIX 500 series security appliance.
To configure cable-based Active/Standby failover, perform the following steps:
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Step 1
Connect the Failover cable to the PIX 500 series security appliances. Make sure that you attach the end
of the cable marked “Primary” to the unit you use as the primary unit, and that you attach the end of the
cable marked “Secondary” to the other unit.
Step 2
Power on the primary unit.
Step 3
If you have not done so already, configure the active and standby IP addresses for each data interface
(routed mode), for the management IP address (transparent mode), or for the management-only
interface. The standby IP address is used on the security appliance that is currently the standby unit. It
must be in the same subnet as the active IP address.
Note
Do not configure an IP address for the Stateful Failover link if you are going to use a dedicated
Stateful Failover interface. You use the failover interface ip command to configure a dedicated
Stateful Failover interface in a later step.
hostname(config-if)# ip address active_addr netmask standby standby_addr
In routed firewall mode and for the management-only interface, this command is entered in interface
configuration mode for each interface. In transparent firewall mode, the command is entered in global
configuration mode.
In multiple context mode, you must configure the interface addresses from within each context. Use the
changeto context command to switch between contexts. The command prompt changes to
hostname/ context (config-if)# , where context is the name of the current context. You must enter a
management IP address for each context in transparent firewall multiple context mode.
Step 4
(Optional) To enable Stateful Failover, configure the Stateful Failover link.
Note
a.
Stateful Failover is not available on the ASA 5505 series adaptive security appliance.
Specify the interface to be used as the Stateful Failover link:
hostname(config)# failover link if_name phy_if
The if_name argument assigns a logical name to the interface specified by the phy_if argument. The
phy_if argument can be the physical port name, such as Ethernet1, or a previously created
subinterface, such as Ethernet0/2.3. This interface should not be used for any other purpose.
b.
Assign an active and standby IP address to the Stateful Failover link:
hostname(config)# failover interface ip if_name ip_addr mask standby ip_addr
Note
If the Stateful Failover link uses a data interface, skip this step. You have already defined the
active and standby IP addresses for the interface.
The standby IP address must be in the same subnet as the active IP address. You do not need to
identify the standby IP address subnet mask.
The Stateful Failover link IP address and MAC address do not change at failover unless it uses a data
interface. The active IP address always stays with the primary unit, while the standby IP address
stays with the secondary unit.
c.
Enable the interface:
hostname(config)# interface phy_if
hostname(config-if)# no shutdown
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Step 5
Enable failover:
hostname(config)# failover
Step 6
Power on the secondary unit and enable failover on the unit if it is not already enabled:
hostname(config)# failover
The active unit sends the configuration in running memory to the standby unit. As the configuration
synchronizes, the messages “Beginning configuration replication: sending to mate.” and “End
Configuration Replication to mate” appear on the primary console.
Step 7
Save the configuration to Flash memory on the primary unit. Because the commands entered on the
primary unit are replicated to the secondary unit, the secondary unit also saves its configuration to Flash
memory.
hostname(config)# copy running-config startup-config
Configuring LAN-Based Active/Standby Failover
This section describes how to configure Active/Standby failover using an Ethernet failover link. When
configuring LAN-based failover, you must bootstrap the secondary device to recognize the failover link
before the secondary device can obtain the running configuration from the primary device.
Note
If you are changing from cable-based failover to LAN-based failover, you can skip any steps, such as
assigning the active and standby IP addresses for each interface, that you completed for the cable-based
failover configuration.
This section includes the following topics:
•
Configuring the Primary Unit, page 14-21
•
Configuring the Secondary Unit, page 14-23
Configuring the Primary Unit
Follow these steps to configure the primary unit in a LAN-based, Active/Standby failover configuration.
These steps provide the minimum configuration needed to enable failover on the primary unit. For
multiple context mode, all steps are performed in the system execution space unless otherwise noted.
To configure the primary unit in an Active/Standby failover pair, perform the following steps:
Step 1
If you have not done so already, configure the active and standby IP addresses for each data interface
(routed mode), for the management IP address (transparent mode), or for the management-only
interface. The standby IP address is used on the security appliance that is currently the standby unit. It
must be in the same subnet as the active IP address.
Note
Do not configure an IP address for the Stateful Failover link if you are going to use a dedicated
Stateful Failover interface. You use the failover interface ip command to configure a dedicated
Stateful Failover interface in a later step.
hostname(config-if)# ip address active_addr netmask standby standby_addr
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In routed firewall mode and for the management-only interface, this command is entered in interface
configuration mode for each interface. In transparent firewall mode, the command is entered in global
configuration mode.
In multiple context mode, you must configure the interface addresses from within each context. Use the
changeto context command to switch between contexts. The command prompt changes to
hostname/ context (config-if)# , where context is the name of the current context. You must enter a
management IP address for each context in transparent firewall multiple context mode.
Step 2
(PIX security appliance only) Enable LAN-based failover:
hostname(config)# failover lan enable
Step 3
Designate the unit as the primary unit:
hostname(config)# failover lan unit primary
Step 4
Define the failover interface:
a.
Specify the interface to be used as the failover interface:
hostname(config)# failover lan interface if_name phy_if
The if_name argument assigns a name to the interface specified by the phy_if argument. The phy_if
argument can be the physical port name, such as Ethernet1, or a previously created subinterface,
such as Ethernet0/2.3. On the ASA 5505 adaptive security appliance, the phy_if specifies a VLAN.
b.
Assign the active and standby IP address to the failover link:
hostname(config)# failover interface ip if_name ip_addr mask standby ip_addr
The standby IP address must be in the same subnet as the active IP address. You do not need to
identify the standby address subnet mask.
The failover link IP address and MAC address do not change at failover. The active IP address for
the failover link always stays with the primary unit, while the standby IP address stays with the
secondary unit.
c.
Enable the interface:
hostname(config)# interface phy_if
hostname(config-if)# no shutdown
Step 5
(Optional) To enable Stateful Failover, configure the Stateful Failover link.
Note
a.
Stateful Failover is not available on the ASA 5505 series adaptive security appliance.
Specify the interface to be used as Stateful Failover link:
hostname(config)# failover link if_name phy_if
Note
If the Stateful Failover link uses the failover link or a data interface, then you only need to
supply the if_name argument.
The if_name argument assigns a logical name to the interface specified by the phy_if argument. The
phy_if argument can be the physical port name, such as Ethernet1, or a previously created
subinterface, such as Ethernet0/2.3. This interface should not be used for any other purpose (except,
optionally, the failover link).
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b.
Assign an active and standby IP address to the Stateful Failover link.
Note
If the Stateful Failover link uses the failover link or data interface, skip this step. You have
already defined the active and standby IP addresses for the interface.
hostname(config)# failover interface ip if_name ip_addr mask standby ip_addr
The standby IP address must be in the same subnet as the active IP address. You do not need to
identify the standby address subnet mask.
The Stateful Failover link IP address and MAC address do not change at failover unless it uses a data
interface. The active IP address always stays with the primary unit, while the standby IP address
stays with the secondary unit.
c.
Enable the interface.
Note
If the Stateful Failover link uses the failover link or data interface, skip this step. You have
already enabled the interface.
hostname(config)# interface phy_if
hostname(config-if)# no shutdown
Step 6
Enable failover:
hostname(config)# failover
Step 7
Save the system configuration to Flash memory:
hostname(config)# copy running-config startup-config
Configuring the Secondary Unit
The only configuration required on the secondary unit is for the failover interface. The secondary unit
requires these commands to initially communicate with the primary unit. After the primary unit sends
its configuration to the secondary unit, the only permanent difference between the two configurations is
the failover lan unit command, which identifies each unit as primary or secondary.
For multiple context mode, all steps are performed in the system execution space unless noted otherwise.
To configure the secondary unit, perform the following steps:
Step 1
(PIX security appliance only) Enable LAN-based failover:
hostname(config)# failover lan enable
Step 2
Define the failover interface. Use the same settings as you used for the primary unit.
a.
Specify the interface to be used as the failover interface:
hostname(config)# failover lan interface if_name phy_if
The if_name argument assigns a name to the interface specified by the phy_if argument.
b.
Assign the active and standby IP address to the failover link:
hostname(config)# failover interface ip if_name ip_addr mask standby ip_addr
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Note
c.
Enter this command exactly as you entered it on the primary unit when you configured the
failover interface on the primary unit.
Enable the interface:
hostname(config)# interface phy_if
hostname(config-if)# no shutdown
Step 3
(Optional) Designate this unit as the secondary unit:
hostname(config)# failover lan unit secondary
Note
Step 4
This step is optional because by default units are designated as secondary unless previously
configured.
Enable failover:
hostname(config)# failover
After you enable failover, the active unit sends the configuration in running memory to the standby unit.
As the configuration synchronizes, the messages “Beginning configuration replication: Sending to mate”
and “End Configuration Replication to mate” appear on the active unit console.
Step 5
After the running configuration has completed replication, save the configuration to Flash memory:
hostname(config)# copy running-config startup-config
Configuring Optional Active/Standby Failover Settings
You can configure the following optional Active/Standby failover setting when you are initially
configuring failover or after failover has already been configured. Unless otherwise noted, the
commands should be entered on the active unit.
This section includes the following topics:
•
Enabling HTTP Replication with Stateful Failover, page 14-24
•
Disabling and Enabling Interface Monitoring, page 14-25
•
Configuring Interface Health Monitoring, page 14-25
•
Configuring Failover Criteria, page 14-26
•
Configuring Virtual MAC Addresses, page 14-26
Enabling HTTP Replication with Stateful Failover
To allow HTTP connections to be included in the state information replication, you need to enable HTTP
replication. Because HTTP connections are typically short-lived, and because HTTP clients typically
retry failed connection attempts, HTTP connections are not automatically included in the replicated state
information.
Enter the following command in global configuration mode to enable HTTP state replication when
Stateful Failover is enabled:
hostname(config)# failover replication http
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Disabling and Enabling Interface Monitoring
By default, monitoring physical interfaces is enabled and monitoring subinterfaces is disabled. You can
monitor up to 250 interfaces on a unit. You can control which interfaces affect your failover policy by
disabling the monitoring of specific interfaces and enabling the monitoring of others. This lets you
exclude interfaces attached to less critical networks from affecting your failover policy.
For units in multiple configuration mode, use the following commands to enable or disable health
monitoring for specific interfaces:
•
To disable health monitoring for an interface, enter the following command within a context:
hostname/context(config)# no monitor-interface if_name
•
To enable health monitoring for an interface, enter the following command within a context:
hostname/context(config)# monitor-interface if_name
For units in single configuration mode, use the following commands to enable or disable health
monitoring for specific interfaces:
•
To disable health monitoring for an interface, enter the following command in global configuration
mode:
hostname(config)# no monitor-interface if_name
•
To enable health monitoring for an interface, enter the following command in global configuration
mode:
hostname(config)# monitor-interface if_name
Configuring Interface Health Monitoring
The security appliance sends hello packets out of each data interface to monitor interface health. If the
security appliance does not receive a hello packet from the corresponding interface on the peer unit for
over half of the hold time, then the additional interface testing begins. If a hello packet or a successful
test result is not received within the specified hold time, the interface is marked as failed. Failover occurs
if the number of failed interfaces meets the failover criteria.
Decreasing the poll and hold times enables the security appliance to detect and respond to interface
failures more quickly, but may consume more system resources.
To change the interface poll time, enter the following command in global configuration mode:
hostname(config)# failover polltime interface [msec] time [holdtime time]
Valid values for the poll time are from 1 to 15 seconds or, if the optional msec keyword is used, from
500 to 999 milliseconds. The hold time determines how long it takes from the time a hello packet is
missed to when the interface is marked as failed. Valid values for the hold time are from 5 to 75 seconds.
You cannot enter a hold time that is less than 5 times the poll time.
Note
If the interface link is down, interface testing is not conducted and the standby unit could become active
in just one interface polling period if the number of failed interface meets or exceeds the configured
failover criteria.
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Configuring Failover Criteria
By default, a single interface failure causes failover. You can specify a specific number of interfaces or
a percentage of monitored interfaces that must fail before a failover occurs.
To change the default failover criteria, enter the following command in global configuration mode:
hostname(config)# failover interface-policy num[%]
When specifying a specific number of interfaces, the num argument can be from 1 to 250. When
specifying a percentage of interfaces, the num argument can be from 1 to 100.
Configuring Virtual MAC Addresses
In Active/Standby failover, the MAC addresses for the primary unit are always associated with the active
IP addresses. If the secondary unit boots first and becomes active, it uses the burned-in MAC address for
its interfaces. When the primary unit comes online, the secondary unit obtains the MAC addresses from
the primary unit. The change can disrupt network traffic.
You can configure virtual MAC addresses for each interface to ensure that the secondary unit uses the
correct MAC addresses when it is the active unit, even if it comes online before the primary unit. If you
do not specify virtual MAC addresses the failover pair uses the burned-in NIC addresses as the MAC
addresses.
Note
You cannot configure a virtual MAC address for the failover or Stateful Failover links. The MAC and IP
addresses for those links do not change during failover.
Enter the following command on the active unit to configure the virtual MAC addresses for an interface:
hostname(config)# failover mac address phy_if active_mac standby_mac
The phy_if argument is the physical name of the interface, such as Ethernet1. The active_mac and
standby_mac arguments are MAC addresses in H.H.H format, where H is a 16-bit hexadecimal digit. For
example, the MAC address 00-0C-F1-42-4C-DE would be entered as 000C.F142.4CDE.
The active_mac address is associated with the active IP address for the interface, and the standby_mac
is associated with the standby IP address for the interface.
There are multiple ways to configure virtual MAC addresses on the security appliance. When more than
one method has been used to configure virtual MAC addresses, the security appliance uses the following
order of preference to determine which virtual MAC address is assigned to an interface:
1.
The mac-address command (in interface configuration mode) address.
2.
The failover mac address command address.
3.
The mac-address auto command generated address.
4.
The burned-in MAC address.
Use the show interface command to display the MAC address used by an interface.
Configuring Active/Active Failover
This section describes how to configure Active/Active failover.
Note
Active/Active failover is not available on the ASA 5505 series adaptive security appliance.
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This section includes the following topics:
•
Prerequisites, page 14-27
•
Configuring Cable-Based Active/Active Failover (PIX security appliance), page 14-27
•
Configuring LAN-Based Active/Active Failover, page 14-29
•
Configuring Optional Active/Active Failover Settings, page 14-32
Prerequisites
Before you begin, verify the following:
•
Both units have the same hardware, software configuration, and proper license.
•
Both units are in multiple context mode.
Configuring Cable-Based Active/Active Failover (PIX security appliance)
Follow these steps to configure Active/Active failover using a serial cable as the failover link. The
commands in this task are entered on the primary unit in the failover pair. The primary unit is the unit
that has the end of the cable labeled “Primary” plugged into it. For devices in multiple context mode, the
commands are entered in the system execution space unless otherwise noted.
You do not need to bootstrap the secondary unit in the failover pair when you use cable-based failover.
Leave the secondary unit powered off until instructed to power it on.
Cable-based failover is only available on the PIX 500 series security appliance.
To configure cable-based, Active/Active failover, perform the following steps:
Step 1
Connect the failover cable to the PIX 500 series security appliances. Make sure that you attach the end
of the cable marked “Primary” to the unit you use as the primary unit, and that you attach the end of the
cable marked “Secondary” to the unit you use as the secondary unit.
Step 2
Power on the primary unit.
Step 3
If you have not done so already, configure the active and standby IP addresses for each data interface
(routed mode), for the management IP address (transparent mode), or for the management-only
interface. The standby IP address is used on the security appliance that is currently the standby unit. It
must be in the same subnet as the active IP address.
You must configure the interface addresses from within each context. Use the changeto context
command to switch between contexts. The command prompt changes to
hostname/ context (config-if)# , where context is the name of the current context. You must enter a
management IP address for each context in transparent firewall multiple context mode.
Note
Do not configure an IP address for the Stateful Failover link if you are going to use a dedicated
Stateful Failover interface. You use the failover interface ip command to configure a dedicated
Stateful Failover interface in a later step.
hostname/context(config-if)# ip address active_addr netmask standby standby_addr
In routed firewall mode and for the management-only interface, this command is entered in interface
configuration mode for each interface. In transparent firewall mode, the command is entered in global
configuration mode.
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Step 4
(Optional) To enable Stateful Failover, configure the Stateful Failover link.
a.
Specify the interface to be used as Stateful Failover link:
hostname(config)# failover link if_name phy_if
The if_name argument assigns a logical name to the interface specified by the phy_if argument. The
phy_if argument can be the physical port name, such as Ethernet1, or a previously created
subinterface, such as Ethernet0/2.3. This interface should not be used for any other purpose (except,
optionally, the failover link).
b.
Assign an active and standby IP address to the Stateful Failover link:
hostname(config)# failover interface ip if_name ip_addr mask standby ip_addr
The standby IP address must be in the same subnet as the active IP address. You do not need to
identify the standby IP address subnet mask.
The Stateful Failover link IP address and MAC address do not change at failover except for when
Stateful Failover uses a regular data interface. The active IP address always stays with the primary
unit, while the standby IP address stays with the secondary unit.
c.
Enable the interface:
hostname(config)# interface phy_if
hostname(config-if)# no shutdown
Step 5
Configure the failover groups. You can have at most two failover groups. The failover group command
creates the specified failover group if it does not exist and enters the failover group configuration mode.
For each failover group, you need to specify whether the failover group has primary or secondary
preference using the primary or secondary command. You can assign the same preference to both
failover groups. For load balancing configurations, you should assign each failover group a different unit
preference.
The following example assigns failover group 1 a primary preference and failover group 2 a secondary
preference:
hostname(config)# failover group 1
hostname(config-fover-group)# primary
hostname(config-fover-group)# exit
hostname(config)# failover group 2
hostname(config-fover-group)# secondary
hostname(config-fover-group)# exit
Step 6
Assign each user context to a failover group using the join-failover-group command in context
configuration mode.
Any unassigned contexts are automatically assigned to failover group 1. The admin context is always a
member of failover group 1.
Enter the following commands to assign each context to a failover group:
hostname(config)# context context_name
hostname(config-context)# join-failover-group {1 | 2}
hostname(config-context)# exit
Step 7
Enable failover:
hostname(config)# failover
Step 8
Power on the secondary unit and enable failover on the unit if it is not already enabled:
hostname(config)# failover
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The active unit sends the configuration in running memory to the standby unit. As the configuration
synchronizes, the messages “Beginning configuration replication: Sending to mate” and “End
Configuration Replication to mate” appear on the primary console.
Step 9
Save the configuration to Flash memory on the Primary unit. Because the commands entered on the
primary unit are replicated to the secondary unit, the secondary unit also saves its configuration to Flash
memory.
hostname(config)# copy running-config startup-config
Step 10
If necessary, force any failover group that is active on the primary to the active state on the secondary.
To force a failover group to become active on the secondary unit, issue the following command in the
system execution space on the primary unit:
hostname# no failover active group group_id
The group_id argument specifies the group you want to become active on the secondary unit.
Configuring LAN-Based Active/Active Failover
This section describes how to configure Active/Active failover using an Ethernet failover link. When
configuring LAN-based failover, you must bootstrap the secondary device to recognize the failover link
before the secondary device can obtain the running configuration from the primary device.
This section includes the following topics:
•
Configure the Primary Unit, page 14-29
•
Configure the Secondary Unit, page 14-31
Configure the Primary Unit
To configure the primary unit in an Active/Active failover configuration, perform the following steps:
Step 1
If you have not done so already, configure the active and standby IP addresses for each data interface
(routed mode), for the management IP address (transparent mode), or for the management-only
interface. The standby IP address is used on the security appliance that is currently the standby unit. It
must be in the same subnet as the active IP address.
You must configure the interface addresses from within each context. Use the changeto context
command to switch between contexts. The command prompt changes to
hostname/ context (config-if)# , where context is the name of the current context. In transparent
firewall mode, you must enter a management IP address for each context.
Note
Do not configure an IP address for the Stateful Failover link if you are going to use a dedicated
Stateful Failover interface. You use the failover interface ip command to configure a dedicated
Stateful Failover interface in a later step.
hostname/context(config-if)# ip address active_addr netmask standby standby_addr
In routed firewall mode and for the management-only interface, this command is entered in interface
configuration mode for each interface. In transparent firewall mode, the command is entered in global
configuration mode.
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Step 2
Configure the basic failover parameters in the system execution space.
a.
(PIX security appliance only) Enable LAN-based failover:
hostname(config)# hostname(config)# failover lan enable
b.
Designate the unit as the primary unit:
hostname(config)# failover lan unit primary
c.
Specify the failover link:
hostname(config)# failover lan interface if_name phy_if
The if_name argument assigns a logical name to the interface specified by the phy_if argument. The
phy_if argument can be the physical port name, such as Ethernet1, or a previously created
subinterface, such as Ethernet0/2.3. On the ASA 5505 adaptive security appliance, the phy_if
specifies a VLAN. This interface should not be used for any other purpose (except, optionally, the
Stateful Failover link).
d.
Specify the failover link active and standby IP addresses:
hostname(config)# failover interface ip if_name ip_addr mask standby ip_addr
The standby IP address must be in the same subnet as the active IP address. You do not need to
identify the standby IP address subnet mask. The failover link IP address and MAC address do not
change at failover. The active IP address always stays with the primary unit, while the standby IP
address stays with the secondary unit.
Step 3
(Optional) To enable Stateful Failover, configure the Stateful Failover link:
a.
Specify the interface to be used as Stateful Failover link:
hostname(config)# failover link if_name phy_if
The if_name argument assigns a logical name to the interface specified by the phy_if argument. The
phy_if argument can be the physical port name, such as Ethernet1, or a previously created
subinterface, such as Ethernet0/2.3. This interface should not be used for any other purpose (except,
optionally, the failover link).
Note
b.
If the Stateful Failover link uses the failover link or a regular data interface, then you only
need to supply the if_name argument.
Assign an active and standby IP address to the Stateful Failover link.
Note
If the Stateful Failover link uses the failover link or a regular data interface, skip this step.
You have already defined the active and standby IP addresses for the interface.
hostname(config)# failover interface ip if_name ip_addr mask standby ip_addr
The standby IP address must be in the same subnet as the active IP address. You do not need to
identify the standby address subnet mask.
The state link IP address and MAC address do not change at failover. The active IP address always
stays with the primary unit, while the standby IP address stays with the secondary unit.
c.
Enable the interface.
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Note
If the Stateful Failover link uses the failover link or regular data interface, skip this step. You
have already enabled the interface.
hostname(config)# interface phy_if
hostname(config-if)# no shutdown
Step 4
Configure the failover groups. You can have at most two failover groups. The failover group command
creates the specified failover group if it does not exist and enters the failover group configuration mode.
For each failover group, specify whether the failover group has primary or secondary preference using
the primary or secondary command. You can assign the same preference to both failover groups. For
load balancing configurations, you should assign each failover group a different unit preference.
The following example assigns failover group 1 a primary preference and failover group 2 a secondary
preference:
hostname(config)# failover group 1
hostname(config-fover-group)# primary
hostname(config-fover-group)# exit
hostname(config)# failover group 2
hostname(config-fover-group)# secondary
hostname(config-fover-group)# exit
Step 5
Assign each user context to a failover group using the join-failover-group command in context
configuration mode.
Any unassigned contexts are automatically assigned to failover group 1. The admin context is always a
member of failover group 1.
Enter the following commands to assign each context to a failover group:
hostname(config)# context context_name
hostname(config-context)# join-failover-group {1 | 2}
hostname(config-context)# exit
Step 6
Enable failover:
hostname(config)# failover
Configure the Secondary Unit
When configuring LAN-based Active/Active failover, you need to bootstrap the secondary unit to
recognize the failover link. This allows the secondary unit to communicate with and receive the running
configuration from the primary unit.
To bootstrap the secondary unit in an Active/Active failover configuration, perform the following steps:
Step 1
(PIX security appliance only) Enable LAN-based failover:
hostname(config)# failover lan enable
Step 2
Define the failover interface. Use the same settings as you used for the primary unit:
a.
Specify the interface to be used as the failover interface:
hostname(config)# failover lan interface if_name phy_if
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The if_name argument assigns a logical name to the interface specified by the phy_if argument. The
phy_if argument can be the physical port name, such as Ethernet1, or a previously created
subinterface, such as Ethernet0/2.3. On the ASA 5505 adaptive security appliance, the phy_if
specifies a VLAN.
b.
Assign the active and standby IP address to the failover link:
hostname(config)# failover interface ip if_name ip_addr mask standby ip_addr
Note
Enter this command exactly as you entered it on the primary unit when you configured the
failover interface.
The standby IP address must be in the same subnet as the active IP address. You do not need to
identify the standby address subnet mask.
c.
Enable the interface:
hostname(config)# interface phy_if
hostname(config-if)# no shutdown
Step 3
(Optional) Designate this unit as the secondary unit:
hostname(config)# failover lan unit secondary
Note
Step 4
This step is optional because by default units are designated as secondary unless previously
configured otherwise.
Enable failover:
hostname(config)# failover
After you enable failover, the active unit sends the configuration in running memory to the standby unit.
As the configuration synchronizes, the messages Beginning configuration replication: Sending to
mate and End Configuration Replication to mate appear on the active unit console.
Step 5
After the running configuration has completed replication, enter the following command to save the
configuration to Flash memory:
hostname(config)# copy running-config startup-config
Step 6
If necessary, force any failover group that is active on the primary to the active state on the secondary
unit. To force a failover group to become active on the secondary unit, enter the following command in
the system execution space on the primary unit:
hostname# no failover active group group_id
The group_id argument specifies the group you want to become active on the secondary unit.
Configuring Optional Active/Active Failover Settings
The following optional Active/Active failover settings can be configured when you are initially
configuring failover or after you have already established failover. Unless otherwise noted, the
commands should be entered on the unit that has failover group 1 in the active state.
This section includes the following topics:
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Configuring Failover
•
Configuring Failover Group Preemption, page 14-33
•
Enabling HTTP Replication with Stateful Failover, page 14-33
•
Disabling and Enabling Interface Monitoring, page 14-33
•
Configuring Interface Health Monitoring, page 14-34
•
Configuring Failover Criteria, page 14-34
•
Configuring Virtual MAC Addresses, page 14-34
•
Configuring Asymmetric Routing Support, page 14-35
Configuring Failover Group Preemption
Assigning a primary or secondary priority to a failover group specifies which unit the failover group
becomes active on when both units boot simultaneously. However, if one unit boots before the other, then
both failover groups become active on that unit. When the other unit comes online, any failover groups
that have the unit as a priority do not become active on that unit unless manually forced over, a failover
occurs, or the failover group is configured with the preempt command. The preempt command causes
a failover group to become active on the designated unit automatically when that unit becomes available.
Enter the following commands to configure preemption for the specified failover group:
hostname(config)# failover group {1 | 2}
hostname(config-fover-group)# preempt [delay]
You can enter an optional delay value, which specifies the number of seconds the failover group remains
active on the current unit before automatically becoming active on the designated unit.
Enabling HTTP Replication with Stateful Failover
To allow HTTP connections to be included in the state information, you need to enable HTTP
replication. Because HTTP connections are typically short-lived, and because HTTP clients typically
retry failed connection attempts, HTTP connections are not automatically included in the replicated state
information. You can use the replication http command to cause a failover group to replicate HTTP state
information when Stateful Failover is enabled.
To enable HTTP state replication for a failover group, enter the following command. This command only
affects the failover group in which it was configured. To enable HTTP state replication for both failover
groups, you must enter this command in each group. This command should be entered in the system
execution space.
hostname(config)# failover group {1 | 2}
hostname(config-fover-group)# replication http
Disabling and Enabling Interface Monitoring
You can monitor up to 250 interfaces on a unit. By default, monitoring of physical interfaces is enabled
and the monitoring of subinterfaces is disabled. You can control which interfaces affect your failover
policy by disabling the monitoring of specific interfaces and enabling the monitoring of others. This lets
you exclude interfaces attached to less critical networks from affecting your failover policy.
To disable health monitoring on an interface, enter the following command within a context:
hostname/context(config)# no monitor-interface if_name
To enable health monitoring on an interface, enter the following command within a context:
hostname/context(config)# monitor-interface if_name
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Configuring Interface Health Monitoring
The security appliance sends hello packets out of each data interface to monitor interface health. If the
security appliance does not receive a hello packet from the corresponding interface on the peer unit for
over half of the hold time, then the additional interface testing begins. If a hello packet or a successful
test result is not received within the specified hold time, the interface is marked as failed. Failover occurs
if the number of failed interfaces meets the failover criteria.
Decreasing the poll and hold times enables the security appliance to detect and respond to interface
failures more quickly, but may consume more system resources.
To change the default interface poll time, enter the following commands:
hostname(config)# failover group {1 | 2}
hostname(config-fover-group)# polltime interface seconds
Valid values for the poll time are from 1 to 15 seconds or, if the optional msec keyword is used, from
500 to 999 milliseconds. The hold time determines how long it takes from the time a hello packet is
missed to when the interface is marked as failed. Valid values for the hold time are from 5 to 75 seconds.
You cannot enter a hold time that is less than 5 times the poll time.
Configuring Failover Criteria
By default, if a single interface fails failover occurs. You can specify a specific number of interfaces or
a percentage of monitored interfaces that must fail before a failover occurs. The failover criteria is
specified on a failover group basis.
To change the default failover criteria for the specified failover group, enter the following commands:
hostname(config)# failover group {1 | 2}
hostname(config-fover-group)# interface-policy num[%]
When specifying a specific number of interfaces, the num argument can be from 1 to 250. When
specifying a percentage of interfaces, the num argument can be from 1 to 100.
Configuring Virtual MAC Addresses
Active/Active failover uses virtual MAC addresses on all interfaces. If you do not specify the virtual
MAC addresses, then they are computed as follows:
Note
•
Active unit default MAC address: 00a0.c9physical_port_number.failover_group_id01.
•
Standby unit default MAC address: 00a0.c9physical_port_number.failover_group_id02.
If you have more than one Active/Active failover pair on the same network, it is possible to have the
same default virtual MAC addresses assigned to the interfaces on one pair as are assigned to the
interfaces of the other pairs because of the way the default virtual MAC addresses are determined. To
avoid having duplicate MAC addresses on your network, make sure you assign each physical interface
a virtual active and standby MAC address for all failover groups.
You can configure specific active and standby MAC addresses for an interface by entering the following
commands:
hostname(config)# failover group {1 | 2}
hostname(config-fover-group)# mac address phy_if active_mac standby_mac
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The phy_if argument is the physical name of the interface, such as Ethernet1. The active_mac and
standby_mac arguments are MAC addresses in H.H.H format, where H is a 16-bit hexadecimal digit. For
example, the MAC address 00-0C-F1-42-4C-DE would be entered as 000C.F142.4CDE.
The active_mac address is associated with the active IP address for the interface, and the standby_mac
is associated with the standby IP address for the interface.
There are multiple ways to configure virtual MAC addresses on the security appliance. When more than
one method has been used to configure virtual MAC addresses, the security appliance uses the following
order of preference to determine which virtual MAC address is assigned to an interface:
1.
The mac-address command (in interface configuration mode) address.
2.
The failover mac address command address.
3.
The mac-address auto command generate address.
4.
The automatically generated failover MAC address.
Use the show interface command to display the MAC address used by an interface.
Configuring Asymmetric Routing Support
When running in Active/Active failover, a unit may receive a return packet for a connection that
originated through its peer unit. Because the security appliance that receives the packet does not have
any connection information for the packet, the packet is dropped. This most commonly occurs when the
two security appliances in an Active/Active failover pair are connected to different service providers and
the outbound connection does not use a NAT address.
You can prevent the return packets from being dropped using the asr-group command on interfaces
where this is likely to occur. When an interface configured with the asr-group command receives a
packet for which it has no session information, it checks the session information for the other interfaces
that are in the same group. If it does not find a match, the packet is dropped. If it finds a match, then one
of the following actions occurs:
Note
•
If the incoming traffic originated on a peer unit, some or all of the layer 2 header is rewritten and
the packet is redirected to the other unit. This redirection continues as long as the session is active.
•
If the incoming traffic originated on a different interface on the same unit, some or all of the layer
2 header is rewritten and the packet is reinjected into the stream.
Using the asr-group command to configure asymmetric routing support is more secure than using the
static command with the nailed option.
The asr-group command does not provide asymmetric routing; it restores asymmetrically routed packets
to the correct interface.
Prerequisites
You must have to following configured for asymmetric routing support to function properly:
•
Active/Active Failover
•
Stateful Failover—passes state information for sessions on interfaces in the active failover group to
the standby failover group.
•
replication http—HTTP session state information is not passed to the standby failover group, and
therefore is not present on the standby interface. For the security appliance to be able re-route
asymmetrically routed HTTP packets, you need to replicate the HTTP state information.
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Configuring Failover
You can configure the asr-group command on an interface without having failover configured, but it
does not have any effect until Stateful Failover is enabled.
Configuring Support for Asymmetrically Routed Packets
To configure support for asymmetrically routed packets, perform the following steps:
Step 1
Configure Active/Active Stateful Failover for the failover pair. See Configuring Active/Active Failover,
page 14-26.
Step 2
For each interface that you want to participate in asymmetric routing support enter the following
command. You must enter the command on the unit where the context is in the active state so that the
command is replicated to the standby failover group. For more information about command replication,
see Command Replication, page 14-12.
hostname/ctx(config)# interface phy_if
hostname/ctx(config-if)# asr-group num
Valid values for num range from 1 to 32. You need to enter the command for each interface that
participates in the asymmetric routing group. You can view the number of ASR packets transmitted,
received, or dropped by an interface using the show interface detail command. You can have more than
one ASR group configured on the security appliance, but only one per interface. Only members of the
same ASR group are checked for session information.
Example
Figure 14-1 shows an example of using the asr-group command for asymmetric routing support.
Figure 14-1
ASR Example
ISP A
ISP B
192.168.1.1
192.168.2.2
192.168.2.1
192.168.1.2
SecAppA
SecAppB
Outbound Traffic
Return Traffic
Inside
network
250093
Failover/State link
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Configuring Failover
The two units have the following configuration (configurations show only the relevant commands). The
device labeled SecAppA in the diagram is the primary unit in the failover pair.
Example 14-1 Primary Unit System Configuration
hostname primary
interface GigabitEthernet0/1
description LAN/STATE Failover Interface
interface GigabitEthernet0/2
no shutdown
interface GigabitEthernet0/3
no shutdown
interface GigabitEthernet0/4
no shutdown
interface GigabitEthernet0/5
no shutdown
failover
failover lan unit primary
failover lan interface folink GigabitEthernet0/1
failover link folink
failover interface ip folink 10.0.4.1 255.255.255.0 standby 10.0.4.11
failover group 1
primary
failover group 2
secondary
admin-context admin
context admin
description admin
allocate-interface GigabitEthernet0/2
allocate-interface GigabitEthernet0/3
config-url flash:/admin.cfg
join-failover-group 1
context ctx1
description context 1
allocate-interface GigabitEthernet0/4
allocate-interface GigabitEthernet0/5
config-url flash:/ctx1.cfg
join-failover-group 2
Example 14-2 admin Context Configuration
hostname SecAppA
interface GigabitEthernet0/2
nameif outsideISP-A
security-level 0
ip address 192.168.1.1 255.255.255.0 standby 192.168.1.2
asr-group 1
interface GigabitEthernet0/3
nameif inside
security-level 100
ip address 10.1.0.1 255.255.255.0 standby 10.1.0.11
monitor-interface outside
Example 14-3 ctx1 Context Configuration
hostname SecAppB
interface GigabitEthernet0/4
nameif outsideISP-B
security-level 0
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ip address 192.168.2.2 255.255.255.0 standby 192.168.2.1
asr-group 1
interface GigabitEthernet0/5
nameif inside
security-level 100
ip address 10.2.20.1 255.255.255.0 standby 10.2.20.11
Figure 14-1 on page 14-36 shows the ASR support working as follows:
1.
An outbound session passes through security appliance SecAppA. It exits interface outsideISP-A
(192.168.1.1).
2.
Because of asymmetric routing configured somewhere upstream, the return traffic comes back
through the interface outsideISP-B (192.168.2.2) on security appliance SecAppB.
3.
Normally the return traffic would be dropped because there is no session information for the traffic
on interface 192.168.2.2. However, the interface is configure with the command asr-group 1. The
unit looks for the session on any other interface configured with the same ASR group ID.
4.
The session information is found on interface outsideISP-A (192.168.1.2), which is in the standby
state on the unit SecAppB. Stateful Failover replicated the session information from SecAppA to
SecAppB.
5.
Instead of being dropped, the layer 2 header is re-written with information for interface 192.168.1.1
and the traffic is redirected out of the interface 192.168.1.2, where it can then return through the
interface on the unit from which it originated (192.168.1.1 on SecAppA). This forwarding continues
as needed until the session ends.
Configuring Unit Health Monitoring
The security appliance sends hello packets over the failover interface to monitor unit health. If the
standby unit does not receive a hello packet from the active unit for two consecutive polling periods, it
sends additional testing packets through the remaining device interfaces. If a hello packet or a response
to the interface test packets is not received within the specified hold time, the standby unit becomes
active.
You can configure the frequency of hello messages when monitoring unit health. Decreasing the poll
time allows a unit failure to be detected more quickly, but consumes more system resources.
To change the unit poll time, enter the following command in global configuration mode:
hostname(config)# failover polltime [msec] time [holdtime [msec] time]
You can configure the polling frequency from 1 to 15 seconds or, if the optional msec keyword is used,
from 200 to 999 milliseconds. The hold time determines how long it takes from the time a hello packet
is missed to when failover occurs. The hold time must be at least 3 times the poll time. You can configure
the hold time from 1 to 45 seconds or, if the optional msec keyword is used, from 800 to 990
milliseconds.
Setting the security appliance to use the minimum poll and hold times allows it to detect and respond to
unit failures in under a second, but it also increases system resource usage and can cause false failure
detection in cases where the networks are congested or where the security appliance is running near full
capacity.
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Configuring Failover
Configuring Failover Communication Authentication/Encryption
You can encrypt and authenticate the communication between failover peers by specifying a shared
secret or hexadecimal key.
Note
On the PIX 500 series security appliance, if you are using the dedicated serial failover cable to connect
the units, then communication over the failover link is not encrypted even if a failover key is configured.
The failover key only encrypts LAN-based failover communication.
Caution
All information sent over the failover and Stateful Failover links is sent in clear text unless you secure
the communication with a failover key. If the security appliance is used to terminate VPN tunnels, this
information includes any usernames, passwords and preshared keys used for establishing the tunnels.
Transmitting this sensitive data in clear text could pose a significant security risk. We recommend
securing the failover communication with a failover key if you are using the security appliance to
terminate VPN tunnels.
Enter the following command on the active unit of an Active/Standby failover pair or on the unit that has
failover group 1 in the active state of an Active/Active failover pair:
hostname(config)# failover key {secret | hex key}
The secret argument specifies a shared secret that is used to generate the encryption key. It can be from
1 to 63 characters. The characters can be any combination of numbers, letters, or punctuation. The hex
key argument specifies a hexadecimal encryption key. The key must be 32 hexadecimal characters (0-9,
a-f).
Note
To prevent the failover key from being replicated to the peer unit in clear text for an existing failover
configuration, disable failover on the active unit (or in the system execution space on the unit that has
failover group 1 in the active state), enter the failover key on both units, and then re-enable failover.
When failover is re-enabled, the failover communication is encrypted with the key.
For new LAN-based failover configurations, the failover key command should be part of the failover
pair bootstrap configuration.
Verifying the Failover Configuration
This section describes how to verify your failover configuration. This section includes the following
topics:
•
Using the show failover Command, page 14-40
•
Viewing Monitored Interfaces, page 14-48
•
Displaying the Failover Commands in the Running Configuration, page 14-48
•
Testing the Failover Functionality, page 14-48
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Configuring Failover
Using the show failover Command
This section describes the show failover command output. On each unit you can verify the failover status
by entering the show failover command. The information displayed depends upon whether you are using
Active/Standby or Active/Active failover.
This section includes the following topics:
•
show failover—Active/Standby, page 14-40
•
Show Failover—Active/Active, page 14-44
show failover—Active/Standby
The following is sample output from the show failover command for Active/Standby Failover.
Table 14-7 provides descriptions for the information shown.
hostname# show failover
Failover On
Cable status: N/A - LAN-based failover enabled
Failover unit Primary
Failover LAN Interface: fover Ethernet2 (up)
Unit Poll frequency 1 seconds, holdtime 3 seconds
Interface Poll frequency 15 seconds
Interface Policy 1
Monitored Interfaces 2 of 250 maximum
failover replication http
Last Failover at: 22:44:03 UTC Dec 8 2004
This host: Primary - Active
Active time: 13434 (sec)
Interface inside (10.130.9.3): Normal
Interface outside (10.132.9.3): Normal
Other host: Secondary - Standby Ready
Active time: 0 (sec)
Interface inside (10.130.9.4): Normal
Interface outside (10.132.9.4): Normal
Stateful Failover Logical Update Statistics
Link : fover Ethernet2 (up)
Stateful Obj
xmit
xerr
General
1950
0
sys cmd
1733
0
up time
0
0
RPC services
0
0
TCP conn
6
0
UDP conn
0
0
ARP tbl
106
0
Xlate_Timeout
0
0
VPN IKE upd
15
0
VPN IPSEC upd
90
0
VPN CTCP upd
0
0
VPN SDI upd
0
0
VPN DHCP upd
0
0
rcv
1733
1733
0
0
0
0
0
0
0
0
0
0
0
rerr
0
0
0
0
0
0
0
0
0
0
0
0
0
Logical Update Queue Information
Cur
Max
Total
Recv Q:
0
2
1733
Xmit Q:
0
2
15225
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Configuring Failover
In multiple context mode, using the show failover command in a security context displays the failover
information for that context. The information is similar to the information shown when using the
command in single context mode. Instead of showing the active/standby status of the unit, it displays the
active/standby status of the context. Table 14-7 provides descriptions for the information shown.
Failover On
Last Failover at: 04:03:11 UTC Jan 4 2003
This context: Negotiation
Active time: 1222 (sec)
Interface outside (192.168.5.121): Normal
Interface inside (192.168.0.1): Normal
Peer context: Not Detected
Active time: 0 (sec)
Interface outside (192.168.5.131): Normal
Interface inside (192.168.0.11): Normal
Stateful Failover Logical Update Statistics
Status: Configured.
Stateful Obj
xmit
xerr
RPC services
0
0
TCP conn
99
0
UDP conn
0
0
ARP tbl
22
0
Xlate_Timeout
0
0
GTP PDP
0
0
GTP PDPMCB
0
0
Table 14-7
rcv
0
0
0
0
0
0
0
rerr
0
0
0
0
0
0
0
Show Failover Display Description
Field
Failover
Cable status:
Options
•
On
•
Off
•
Normal—The cable is connected to both units, and they both have
power.
•
My side not connected—The serial cable is not connected to this
unit. It is unknown if the cable is connected to the other unit.
•
Other side is not connected—The serial cable is connected to this
unit, but not to the other unit.
•
Other side powered off—The other unit is turned off.
•
N/A—LAN-based failover is enabled.
Failover Unit
Primary or Secondary.
Failover LAN Interface
Displays the logical and physical name of the failover link.
Unit Poll frequency
Displays the number of seconds between hello messages sent to the
peer unit and the number of seconds during which the unit must receive
a hello message on the failover link before declaring the peer failed.
Interface Poll frequency
n seconds
The number of seconds you set with the failover polltime interface
command. The default is 15 seconds.
Interface Policy
Displays the number or percentage of interfaces that must fail to trigger
failover.
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Table 14-7
Show Failover Display Description (continued)
Field
Options
Monitored Interfaces
Displays the number of interfaces monitored out of the maximum
possible.
failover replication http
Displays if HTTP state replication is enabled for Stateful Failover.
Last Failover at:
The date and time of the last failover in the following form:
hh:mm:ss UTC DayName Month Day yyyy
UTC (Coordinated Universal Time) is equivalent to GMT (Greenwich
Mean Time).
This host:
For each host, the display shows the following information.
Other host:
Primary or Secondary
Active time:
•
Active
•
Standby
n (sec)
The amount of time the unit has been active. This time is cumulative,
so the standby unit, if it was active in the past, also shows a value.
slot x
Information about the module in the slot or empty.
Interface name (n.n.n.n): For each interface, the display shows the IP address currently being
used on each unit, as well as one of the following conditions:
Stateful Failover Logical
Update Statistics
Link
•
Failed—The interface has failed.
•
No Link—The interface line protocol is down.
•
Normal—The interface is working correctly.
•
Link Down—The interface has been administratively shut down.
•
Unknown—The security appliance cannot determine the status of
the interface.
•
Waiting—Monitoring of the network interface on the other unit has
not yet started.
The following fields relate to the Stateful Failover feature. If the Link
field shows an interface name, the Stateful Failover statistics are shown.
•
interface_name—The interface used for the Stateful Failover link.
•
Unconfigured—You are not using Stateful Failover.
•
up—The interface is up and functioning.
•
down—The interface is either administratively shutdown or is
physically down.
•
failed—The interface has failed and is not passing stateful data.
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Table 14-7
Show Failover Display Description (continued)
Field
Options
Stateful Obj
For each field type, the following statistics are shown. They are
counters for the number of state information packets sent between the
two units; the fields do not necessarily show active connections through
the unit.
•
xmit—Number of transmitted packets to the other unit.
•
xerr—Number of errors that occurred while transmitting packets to
the other unit.
•
rcv—Number of received packets.
•
rerr—Number of errors that occurred while receiving packets from
the other unit.
General
Sum of all stateful objects.
sys cmd
Logical update system commands; for example, LOGIN and Stay
Alive.
up time
Up time, which the active unit passes to the standby unit.
RPC services
Remote Procedure Call connection information.
TCP conn
TCP connection information.
UDP conn
Dynamic UDP connection information.
ARP tbl
Dynamic ARP table information.
L2BRIDGE tbl
Layer 2 bridge table information (transparent firewall mode only).
Xlate_Timeout
Indicates connection translation timeout information.
VPN IKE upd
IKE connection information.
VPN IPSEC upd
IPSec connection information.
VPN CTCP upd
cTCP tunnel connection information.
VPN SDI upd
SDI AAA connection information.
VPN DHCP upd
Tunneled DHCP connection information.
GTP PDP
GTP PDP update information. This information appears only if inspect
GTP is enabled.
GTP PDPMCB
GTP PDPMCB update information. This information appears only if
inspect GTP is enabled.
Logical Update Queue
Information
For each field type, the following statistics are used:
•
Cur—Current number of packets
•
Max—Maximum number of packets
•
Total—Total number of packets
Recv Q
The status of the receive queue.
Xmit Q
The status of the transmit queue.
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Show Failover—Active/Active
The following is sample output from the show failover command for Active/Active Failover. Table 14-8
provides descriptions for the information shown.
hostname# show failover
Failover On
Failover unit Primary
Failover LAN Interface: third GigabitEthernet0/2 (up)
Unit Poll frequency 1 seconds, holdtime 15 seconds
Interface Poll frequency 4 seconds
Interface Policy 1
Monitored Interfaces 8 of 250 maximum
failover replication http
Group 1 last failover at: 13:40:18 UTC Dec 9 2004
Group 2 last failover at: 13:40:06 UTC Dec 9 2004
This host:
Group 1
Group 2
Primary
State:
Active time:
State:
Active time:
Active
2896 (sec)
Standby Ready
0 (sec)
slot 0: ASA-5530 hw/sw rev (1.0/7.0(0)79) status (Up Sys)
slot 1: SSM-IDS-20 hw/sw rev (1.0/5.0(0.11)S91(0.11)) status (Up)
admin Interface outside (10.132.8.5): Normal
admin Interface third (10.132.9.5): Normal
admin Interface inside (10.130.8.5): Normal
admin Interface fourth (10.130.9.5): Normal
ctx1 Interface outside (10.1.1.1): Normal
ctx1 Interface inside (10.2.2.1): Normal
ctx2 Interface outside (10.3.3.2): Normal
ctx2 Interface inside (10.4.4.2): Normal
Other host:
Group 1
Group 2
Secondary
State:
Active time:
State:
Active time:
Standby Ready
190 (sec)
Active
3322 (sec)
slot 0: ASA-5530 hw/sw rev (1.0/7.0(0)79) status (Up Sys)
slot 1: SSM-IDS-20 hw/sw rev (1.0/5.0(0.1)S91(0.1)) status (Up)
admin Interface outside (10.132.8.6): Normal
admin Interface third (10.132.9.6): Normal
admin Interface inside (10.130.8.6): Normal
admin Interface fourth (10.130.9.6): Normal
ctx1 Interface outside (10.1.1.2): Normal
ctx1 Interface inside (10.2.2.2): Normal
ctx2 Interface outside (10.3.3.1): Normal
ctx2 Interface inside (10.4.4.1): Normal
Stateful Failover Logical Update Statistics
Link : third GigabitEthernet0/2 (up)
Stateful Obj
xmit
xerr
rcv
General
1973
0
1895
sys cmd
380
0
380
up time
0
0
0
RPC services
0
0
0
TCP conn
1435
0
1450
UDP conn
0
0
0
ARP tbl
124
0
65
Xlate_Timeout
0
0
0
VPN IKE upd
15
0
0
rerr
0
0
0
0
0
0
0
0
0
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Configuring Failover
VPN
VPN
VPN
VPN
IPSEC upd
CTCP upd
SDI upd
DHCP upd
90
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Logical Update Queue Information
Cur
Max
Total
Recv Q:
0
1
1895
Xmit Q:
0
0
1940
The following is sample output from the show failover group command for Active/Active Failover. The
information displayed is similar to that of the show failover command, but limited to the specified
group. Table 14-8 provides descriptions for the information shown.
hostname# show failover group 1
Last Failover at: 04:09:59 UTC Jan 4 2005
This host:
Secondary
State:
Active time:
Active
186 (sec)
admin Interface outside (192.168.5.121): Normal
admin Interface inside (192.168.0.1): Normal
Other host:
Primary
State:
Active time:
Standby
0 (sec)
admin Interface outside (192.168.5.131): Normal
admin Interface inside (192.168.0.11): Normal
Stateful Failover Logical Update Statistics
Status: Configured.
RPC services
0
0
TCP conn
33
0
UDP conn
0
0
ARP tbl
12
0
Xlate_Timeout
0
0
GTP PDP
0
0
GTP PDPMCB
0
0
Table 14-8
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Show Failover Display Description
Field
Failover
Options
•
On
•
Off
Failover Unit
Primary or Secondary.
Failover LAN Interface
Displays the logical and physical name of the failover link.
Unit Poll frequency
Displays the number of seconds between hello messages sent to the
peer unit and the number of seconds during which the unit must receive
a hello message on the failover link before declaring the peer failed.
Interface Poll frequency
n seconds
The number of seconds you set with the failover polltime interface
command. The default is 15 seconds.
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Configuring Failover
Table 14-8
Show Failover Display Description (continued)
Field
Options
Interface Policy
Displays the number or percentage of interfaces that must fail before
triggering failover.
Monitored Interfaces
Displays the number of interfaces monitored out of the maximum
possible.
Group 1 Last Failover at:
The date and time of the last failover for each group in the following
form:
Group 2 Last Failover at:
hh:mm:ss UTC DayName Month Day yyyy
UTC (Coordinated Universal Time) is equivalent to GMT (Greenwich
Mean Time).
This host:
For each host, the display shows the following information.
Other host:
Role
System State
Primary or Secondary
•
Active or Standby Ready
•
Active Time in seconds
Group 1 State
•
Active or Standby Ready
Group 2 State
•
Active Time in seconds
slot x
Information about the module in the slot or empty.
context Interface name
(n.n.n.n):
For each interface, the display shows the IP address currently being
used on each unit, as well as one of the following conditions:
Stateful Failover Logical
Update Statistics
Link
•
Failed—The interface has failed.
•
No link—The interface line protocol is down.
•
Normal—The interface is working correctly.
•
Link Down—The interface has been administratively shut down.
•
Unknown—The security appliance cannot determine the status of
the interface.
•
Waiting—Monitoring of the network interface on the other unit has
not yet started.
The following fields relate to the Stateful Failover feature. If the Link
field shows an interface name, the Stateful Failover statistics are shown.
•
interface_name—The interface used for the Stateful Failover link.
•
Unconfigured—You are not using Stateful Failover.
•
up—The interface is up and functioning.
•
down—The interface is either administratively shutdown or is
physically down.
•
failed—The interface has failed and is not passing stateful data.
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Configuring Failover
Table 14-8
Show Failover Display Description (continued)
Field
Options
Stateful Obj
For each field type, the following statistics are used. They are counters
for the number of state information packets sent between the two units;
the fields do not necessarily show active connections through the unit.
•
xmit—Number of transmitted packets to the other unit
•
xerr—Number of errors that occurred while transmitting packets to
the other unit
•
rcv—Number of received packets
•
rerr—Number of errors that occurred while receiving packets from
the other unit
General
Sum of all stateful objects.
sys cmd
Logical update system commands; for example, LOGIN and Stay
Alive.
up time
Up time, which the active unit passes to the standby unit.
RPC services
Remote Procedure Call connection information.
TCP conn
TCP connection information.
UDP conn
Dynamic UDP connection information.
ARP tbl
Dynamic ARP table information.
L2BRIDGE tbl
Layer 2 bridge table information (transparent firewall mode only).
Xlate_Timeout
Indicates connection translation timeout information.
VPN IKE upd
IKE connection information.
VPN IPSEC upd
IPSec connection information.
VPN CTCP upd
cTCP tunnel connection information.
VPN SDI upd
SDI AAA connection information.
VPN DHCP upd
Tunneled DHCP connection information.
GTP PDP
GTP PDP update information. This information appears only if inspect
GTP is enabled.
GTP PDPMCB
GTP PDPMCB update information. This information appears only if
inspect GTP is enabled.
Logical Update Queue
Information
For each field type, the following statistics are used:
•
Cur—Current number of packets
•
Max—Maximum number of packets
•
Total—Total number of packets
Recv Q
The status of the receive queue.
Xmit Q
The status of the transmit queue.
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Configuring Failover
Viewing Monitored Interfaces
To view the status of monitored interfaces, enter the following command. In single context mode, enter
this command in global configuration mode. In multiple context mode, enter this command within a
context.
primary/context(config)# show monitor-interface
For example:
hostname/context(config)# show monitor-interface
This host: Primary - Active
Interface outside (192.168.1.2): Normal
Interface inside (10.1.1.91): Normal
Other host: Secondary - Standby
Interface outside (192.168.1.3): Normal
Interface inside (10.1.1.100): Normal
Displaying the Failover Commands in the Running Configuration
To view the failover commands in the running configuration, enter the following command:
hostname(config)# show running-config failover
All of the failover commands are displayed. On units running multiple context mode, enter this command
in the system execution space. Entering show running-config all failover displays the failover
commands in the running configuration and includes commands for which you have not changed the
default value.
Testing the Failover Functionality
To test failover functionality, perform the following steps:
Step 1
Test that your active unit or failover group is passing traffic as expected by using FTP (for example) to
send a file between hosts on different interfaces.
Step 2
Force a failover to the standby unit by entering the following command:
•
For Active/Standby failover, enter the following command on the active unit:
hostname(config)# no failover active
•
For Active/Active failover, enter the following command on the unit where the failover group
containing the interface connecting your hosts is active:
hostname(config)# no failover active group group_id
Step 3
Use FTP to send another file between the same two hosts.
Step 4
If the test was not successful, enter the show failover command to check the failover status.
Step 5
When you are finished, you can restore the unit or failover group to active status by enter the following
command:
•
For Active/Standby failover, enter the following command on the active unit:
hostname(config)# failover active
•
For Active/Active failover, enter the following command on the unit where the failover group
containing the interface connecting your hosts is active:
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Controlling and Monitoring Failover
hostname(config)# failover active group group_id
Controlling and Monitoring Failover
This sections describes how to control and monitor failover. This section includes the following topics:
•
Forcing Failover, page 14-49
•
Disabling Failover, page 14-49
•
Restoring a Failed Unit or Failover Group, page 14-50
•
Monitoring Failover, page 14-50
Forcing Failover
To force the standby unit or failover group to become active, enter one of the following commands:
•
For Active/Standby failover:
Enter the following command on the standby unit:
hostname# failover active
Or, enter the following command on the active unit:
hostname# no failover active
•
For Active/Active failover:
Enter the following command in the system execution space of the unit where the failover group is
in the standby state:
hostname# failover active group group_id
Or, enter the following command in the system execution space of the unit where the failover group
is in the active state:
hostname# no failover active group group_id
Entering the following command in the system execution space causes all failover groups to become
active:
hostname# failover active
Disabling Failover
To disable failover, enter the following command:
hostname(config)# no failover
Disabling failover on an Active/Standby pair causes the active and standby state of each unit to be
maintained until you restart. For example, the standby unit remains in standby mode so that both units
do not start passing traffic. To make the standby unit active (even with failover disabled), see the
“Forcing Failover” section on page 14-49.
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Controlling and Monitoring Failover
Disabling failover on an Active/Active pair causes the failover groups to remain in the active state on
whichever unit they are currently active on, no matter which unit they are configured to prefer. The no
failover command should be entered in the system execution space.
Restoring a Failed Unit or Failover Group
To restore a failed unit to an unfailed state, enter the following command:
hostname(config)# failover reset
To restore a failed Active/Active failover group to an unfailed state, enter the following command:
hostname(config)# failover reset group group_id
Restoring a failed unit or group to an unfailed state does not automatically make it active; restored units
or groups remain in the standby state until made active by failover (forced or natural). An exception is a
failover group configured with the preempt command. If previously active, a failover group becomes
active if it is configured with the preempt command and if the unit on which it failed is the preferred
unit.
Monitoring Failover
When a failover occurs, both security appliances send out system messages. This section includes the
following topics:
•
Failover System Messages, page 14-50
•
Debug Messages, page 14-50
•
SNMP, page 14-51
Failover System Messages
The security appliance issues a number of system messages related to failover at priority level 2, which
indicates a critical condition. To view these messages, see the Cisco Security Appliance Logging
Configuration and System Log Messages to enable logging and to see descriptions of the system
messages.
Note
During switchover, failover logically shuts down and then bring up interfaces, generating syslog 411001
and 411002 messages. This is normal activity.
Debug Messages
To see debug messages, enter the debug fover command. See the Cisco Security Appliance Command
Reference for more information.
Note
Because debugging output is assigned high priority in the CPU process, it can drastically affect system
performance. For this reason, use the debug fover commands only to troubleshoot specific problems or
during troubleshooting sessions with Cisco TAC.
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Controlling and Monitoring Failover
SNMP
To receive SNMP syslog traps for failover, configure the SNMP agent to send SNMP traps to SNMP
management stations, define a syslog host, and compile the Cisco syslog MIB into your SNMP
management station. See the snmp-server and logging commands in the Cisco Security Appliance
Command Reference for more information.
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Controlling and Monitoring Failover
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A R T
2
Configuring the Firewall
CH A P T E R
15
Firewall Mode Overview
This chapter describes how the firewall works in each firewall mode. To set the firewall mode, see the
“Setting Transparent or Routed Firewall Mode” section on page 2-5.
Note
In multiple context mode, you cannot set the firewall mode separately for each context; you can only set
the firewall mode for the entire security appliance.
This chapter includes the following sections:
•
Routed Mode Overview, page 15-1
•
Transparent Mode Overview, page 15-8
Routed Mode Overview
In routed mode, the security appliance is considered to be a router hop in the network. It can perform
NAT between connected networks, and can use OSPF or RIP (in single context mode). Routed mode
supports many interfaces. Each interface is on a different subnet. You can share interfaces between
contexts.
This section includes the following topics:
•
IP Routing Support, page 15-1
•
Network Address Translation, page 15-2
•
How Data Moves Through the Security Appliance in Routed Firewall Mode, page 15-3
IP Routing Support
The security appliance acts as a router between connected networks, and each interface requires an
IP address on a different subnet. In single context mode, the routed firewall supports OSPF and RIP.
Multiple context mode supports static routes only. We recommend using the advanced routing
capabilities of the upstream and downstream routers instead of relying on the security appliance for
extensive routing needs.
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Routed Mode Overview
Network Address Translation
NAT substitutes the local address on a packet with a global address that is routable on the destination
network. By default, NAT is not required. If you want to enforce a NAT policy that requires hosts on a
higher security interface (inside) to use NAT when communicating with a lower security interface
(outside), you can enable NAT control (see the nat-control command).
Note
NAT control was the default behavior for software versions earlier than Version 7.0. If you upgrade a
security appliance from an earlier version, then the nat-control command is automatically added to your
configuration to maintain the expected behavior.
Some of the benefits of NAT include the following:
•
You can use private addresses on your inside networks. Private addresses are not routable on the
Internet.
•
NAT hides the local addresses from other networks, so attackers cannot learn the real address of a
host.
•
NAT can resolve IP routing problems by supporting overlapping IP addresses.
Figure 15-1 shows a typical NAT scenario, with a private network on the inside. When the inside user
sends a packet to a web server on the Internet, the local source address of the packet is changed to a
routable global address. When the web server responds, it sends the response to the global address, and
the security appliance receives the packet. The security appliance then translates the global address to
the local address before sending it on to the user.
Figure 15-1
NAT Example
Web Server
www.example.com
Outside
209.165.201.2
Originating
Packet
Responding
Packet
Source Addr Translation
10.1.2.27
209.165.201.10
Dest Addr Translation
209.165.201.10
10.1.2.27
10.1.2.1
10.1.2.27
92405
Inside
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Routed Mode Overview
How Data Moves Through the Security Appliance in Routed Firewall Mode
This section describes how data moves through the security appliance in routed firewall mode, and
includes the following topics:
•
An Inside User Visits a Web Server, page 15-3
•
An Outside User Visits a Web Server on the DMZ, page 15-4
•
An Inside User Visits a Web Server on the DMZ, page 15-6
•
An Outside User Attempts to Access an Inside Host, page 15-7
•
A DMZ User Attempts to Access an Inside Host, page 15-8
An Inside User Visits a Web Server
Figure 15-2 shows an inside user accessing an outside web server.
Figure 15-2
Inside to Outside
www.example.com
Outside
209.165.201.2
Source Addr Translation
10.1.2.27
209.165.201.10
10.1.2.1
10.1.1.1
DMZ
User
10.1.2.27
Web Server
10.1.1.3
92404
Inside
The following steps describe how data moves through the security appliance (see Figure 15-2):
1.
The user on the inside network requests a web page from www.example.com.
2.
The security appliance receives the packet and because it is a new session, the security appliance
verifies that the packet is allowed according to the terms of the security policy (access lists, filters,
AAA).
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Routed Mode Overview
For multiple context mode, the security appliance first classifies the packet according to either a
unique interface or a unique destination address associated with a context; the destination address
is associated by matching an address translation in a context. In this case, the interface would be
unique; the www.example.com IP address does not have a current address translation in a context.
3.
The security appliance translates the local source address (10.1.2.27) to the global address
209.165.201.10, which is on the outside interface subnet.
The global address could be on any subnet, but routing is simplified when it is on the outside
interface subnet.
4.
The security appliance then records that a session is established and forwards the packet from the
outside interface.
5.
When www.example.com responds to the request, the packet goes through the security appliance,
and because the session is already established, the packet bypasses the many lookups associated
with a new connection. The security appliance performs NAT by translating the global destination
address to the local user address, 10.1.2.27.
6.
The security appliance forwards the packet to the inside user.
An Outside User Visits a Web Server on the DMZ
Figure 15-3 shows an outside user accessing the DMZ web server.
Figure 15-3
Outside to DMZ
User
Outside
209.165.201.2
Inside
10.1.1.1
DMZ
Web Server
10.1.1.3
92406
10.1.2.1
Dest Addr Translation
10.1.1.13
209.165.201.3
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Routed Mode Overview
The following steps describe how data moves through the security appliance (see Figure 15-3):
1.
A user on the outside network requests a web page from the DMZ web server using the global
destination address of 209.165.201.3, which is on the outside interface subnet.
2.
The security appliance receives the packet and because it is a new session, the security appliance
verifies that the packet is allowed according to the terms of the security policy (access lists, filters,
AAA).
For multiple context mode, the security appliance first classifies the packet according to either a
unique interface or a unique destination address associated with a context; the destination address
is associated by matching an address translation in a context. In this case, the classifier “knows” that
the DMZ web server address belongs to a certain context because of the server address translation.
3.
The security appliance translates the destination address to the local address 10.1.1.3.
4.
The security appliance then adds a session entry to the fast path and forwards the packet from the
DMZ interface.
5.
When the DMZ web server responds to the request, the packet goes through the security appliance
and because the session is already established, the packet bypasses the many lookups associated
with a new connection. The security appliance performs NAT by translating the local source address
to 209.165.201.3.
6.
The security appliance forwards the packet to the outside user.
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Routed Mode Overview
An Inside User Visits a Web Server on the DMZ
Figure 15-4 shows an inside user accessing the DMZ web server.
Figure 15-4
Inside to DMZ
Outside
209.165.201.2
10.1.2.1
DMZ
92403
Inside
10.1.1.1
User
10.1.2.27
Web Server
10.1.1.3
The following steps describe how data moves through the security appliance (see Figure 15-4):
1.
A user on the inside network requests a web page from the DMZ web server using the destination
address of 10.1.1.3.
2.
The security appliance receives the packet and because it is a new session, the security appliance
verifies that the packet is allowed according to the terms of the security policy (access lists, filters,
AAA).
For multiple context mode, the security appliance first classifies the packet according to either a
unique interface or a unique destination address associated with a context; the destination address
is associated by matching an address translation in a context. In this case, the interface is unique;
the web server IP address does not have a current address translation.
3.
The security appliance then records that a session is established and forwards the packet out of the
DMZ interface.
4.
When the DMZ web server responds to the request, the packet goes through the fast path, which lets
the packet bypass the many lookups associated with a new connection.
5.
The security appliance forwards the packet to the inside user.
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Routed Mode Overview
An Outside User Attempts to Access an Inside Host
Figure 15-5 shows an outside user attempting to access the inside network.
Figure 15-5
Outside to Inside
www.example.com
Outside
209.165.201.2
Inside
User
10.1.2.27
10.1.1.1
DMZ
92407
10.1.2.1
The following steps describe how data moves through the security appliance (see Figure 15-5):
1.
A user on the outside network attempts to reach an inside host (assuming the host has a routable
IP address).
If the inside network uses private addresses, no outside user can reach the inside network without
NAT. The outside user might attempt to reach an inside user by using an existing NAT session.
2.
The security appliance receives the packet and because it is a new session, the security appliance
verifies if the packet is allowed according to the security policy (access lists, filters, AAA).
3.
The packet is denied, and the security appliance drops the packet and logs the connection attempt.
If the outside user is attempting to attack the inside network, the security appliance employs many
technologies to determine if a packet is valid for an already established session.
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Transparent Mode Overview
A DMZ User Attempts to Access an Inside Host
Figure 15-6 shows a user in the DMZ attempting to access the inside network.
Figure 15-6
DMZ to Inside
Outside
209.165.201.2
10.1.2.1
10.1.1.1
DMZ
User
10.1.2.27
Web Server
10.1.1.3
92402
Inside
The following steps describe how data moves through the security appliance (see Figure 15-6):
1.
A user on the DMZ network attempts to reach an inside host. Because the DMZ does not have to
route the traffic on the internet, the private addressing scheme does not prevent routing.
2.
The security appliance receives the packet and because it is a new session, the security appliance
verifies if the packet is allowed according to the security policy (access lists, filters, AAA).
3.
The packet is denied, and the security appliance drops the packet and logs the connection attempt.
Transparent Mode Overview
Traditionally, a firewall is a routed hop and acts as a default gateway for hosts that connect to one of its
screened subnets. A transparent firewall, on the other hand, is a Layer 2 firewall that acts like a “bump
in the wire,” or a “stealth firewall,” and is not seen as a router hop to connected devices.
This section describes transparent firewall mode, and includes the following topics:
•
Transparent Firewall Network, page 15-9
•
Allowing Layer 3 Traffic, page 15-9
•
Passing Traffic Not Allowed in Routed Mode, page 15-9
•
MAC Address Lookups, page 15-10
•
Using the Transparent Firewall in Your Network, page 15-10
•
Transparent Firewall Guidelines, page 15-10
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Transparent Mode Overview
•
Unsupported Features in Transparent Mode, page 15-11
•
How Data Moves Through the Transparent Firewall, page 15-13
Transparent Firewall Network
The security appliance connects the same network on its inside and outside interfaces. Because the
firewall is not a routed hop, you can easily introduce a transparent firewall into an existing network; IP
readdressing is unnecessary.
Allowing Layer 3 Traffic
IPv4 traffic is allowed through the transparent firewall automatically from a higher security interface to
a lower security interface, without an access list. ARPs are allowed through the transparent firewall in
both directions without an access list. ARP traffic can be controlled by ARP inspection. For Layer 3
traffic travelling from a low to a high security interface, an extended access list is required.
Allowed MAC Addresses
The following destination MAC addresses are allowed through the transparent firewall. Any MAC
address not on this list is dropped.
•
TRUE broadcast destination MAC address equal to FFFF.FFFF.FFFF
•
IPv4 multicast MAC addresses from 0100.5E00.0000 to 0100.5EFE.FFFF
•
IPv6 multicast MAC addresses from 3333.0000.0000 to 3333.FFFF.FFFF
•
BPDU multicast address equal to 0100.0CCC.CCCD
•
Appletalk multicast MAC addresses from 0900.0700.0000 to 0900.07FF.FFFF
Passing Traffic Not Allowed in Routed Mode
In routed mode, some types of traffic cannot pass through the security appliance even if you allow it in
an access list. The transparent firewall, however, can allow almost any traffic through using either an
extended access list (for IP traffic) or an EtherType access list (for non-IP traffic).
Note
The transparent mode security appliance does not pass CDP packets or IPv6 packets, or any packets that
do not have a valid EtherType greater than or equal to 0x600. For example, you cannot pass IS-IS
packets. An exception is made for BPDUs, which are supported.
For example, you can establish routing protocol adjacencies through a transparent firewall; you can
allow OSPF, RIP, EIGRP, or BGP traffic through based on an extended access list. Likewise, protocols
like HSRP or VRRP can pass through the security appliance.
Non-IP traffic (for example AppleTalk, IPX, BPDUs, and MPLS) can be configured to go through using
an EtherType access list.
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Transparent Mode Overview
For features that are not directly supported on the transparent firewall, you can allow traffic to pass
through so that upstream and downstream routers can support the functionality. For example, by using
an extended access list, you can allow DHCP traffic (instead of the unsupported DHCP relay feature) or
multicast traffic such as that created by IP/TV.
MAC Address Lookups
When the security appliance runs in transparent mode, the outgoing interface of a packet is determined
by performing a MAC address lookup instead of a route lookup. Route statements can still be configured,
but they only apply to security appliance-originated traffic. For example, if your syslog server is located
on a remote network, you must use a static route so the security appliance can reach that subnet.
Using the Transparent Firewall in Your Network
Figure 15-7 shows a typical transparent firewall network where the outside devices are on the same
subnet as the inside devices. The inside router and hosts appear to be directly connected to the outside
router.
Figure 15-7
Transparent Firewall Network
Internet
10.1.1.1
Network A
Management IP
10.1.1.2
10.1.1.3
Network B
92411
192.168.1.2
Transparent Firewall Guidelines
Follow these guidelines when planning your transparent firewall network:
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Transparent Mode Overview
•
A management IP address is required; for multiple context mode, an IP address is required for each
context.
Unlike routed mode, which requires an IP address for each interface, a transparent firewall has an
IP address assigned to the entire device. The security appliance uses this IP address as the source
address for packets originating on the security appliance, such as system messages or AAA
communications.
The management IP address must be on the same subnet as the connected network. You cannot set
the subnet to a host subnet (255.255.255.255).
You can configure an IP address for the Management 0/0 management-only interface. This IP
address can be on a separate subnet from the main management IP address.
•
The transparent security appliance uses an inside interface and an outside interface only. If your
platform includes a dedicated management interface, you can also configure the management
interface or subinterface for management traffic only.
In single mode, you can only use two data interfaces (and the dedicated management interface, if
available) even if your security appliance includes more than two interfaces.
•
Each directly connected network must be on the same subnet.
•
Do not specify the security appliance management IP address as the default gateway for connected
devices; devices need to specify the router on the other side of the security appliance as the default
gateway.
•
For multiple context mode, each context must use different interfaces; you cannot share an interface
across contexts.
•
For multiple context mode, each context typically uses a different subnet. You can use overlapping
subnets, but your network topology requires router and NAT configuration to make it possible from
a routing standpoint.
Unsupported Features in Transparent Mode
Table 15-1 lists the features are not supported in transparent mode.
Table 15-1
Unsupported Features in Transparent Mode
Feature
Description
Dynamic DNS
—
DHCP relay
The transparent firewall can act as a DHCP server, but it does not
support the DHCP relay commands. DHCP relay is not required
because you can allow DHCP traffic to pass through using two
extended access lists: one that allows DCHP requests from the inside
interface to the outside, and one that allows the replies from the server
in the other direction.
Dynamic routing protocols
You can, however, add static routes for traffic originating on the
security appliance. You can also allow dynamic routing protocols
through the security appliance using an extended access list.
IPv6
You also cannot allow IPv6 using an EtherType access list.
Multicast
You can allow multicast traffic through the security appliance by
allowing it in an extended access list.
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Table 15-1
Unsupported Features in Transparent Mode
Feature
Description
NAT
NAT is performed on the upstream router.
QoS
—
VPN termination for through
traffic
The transparent firewall supports site-to-site VPN tunnels for
management connections only. It does not terminate VPN connections
for traffic through the security appliance. You can pass VPN traffic
through the security appliance using an extended access list, but it
does not terminate non-management connections. WebVPN is also not
supported.
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How Data Moves Through the Transparent Firewall
Figure 15-8 shows a typical transparent firewall implementation with an inside network that contains a
public web server. The security appliance has an access list so that the inside users can access Internet
resources. Another access list lets the outside users access only the web server on the inside network.
Figure 15-8
Typical Transparent Firewall Data Path
www.example.com
Internet
209.165.201.2
Management IP
209.165.201.6
Host
209.165.201.3
92412
209.165.200.230
Web Server
209.165.200.225
This section describes how data moves through the security appliance, and includes the following topics:
•
An Inside User Visits a Web Server, page 15-14
•
An Outside User Visits a Web Server on the Inside Network, page 15-15
•
An Outside User Attempts to Access an Inside Host, page 15-16
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An Inside User Visits a Web Server
Figure 15-9 shows an inside user accessing an outside web server.
Figure 15-9
Inside to Outside
www.example.com
Internet
209.165.201.2
Host
209.165.201.3
92408
Management IP
209.165.201.6
The following steps describe how data moves through the security appliance (see Figure 15-9):
1.
The user on the inside network requests a web page from www.example.com.
2.
The security appliance receives the packet and adds the source MAC address to the MAC address
table, if required. Because it is a new session, it verifies that the packet is allowed according to the
terms of the security policy (access lists, filters, AAA).
For multiple context mode, the security appliance first classifies the packet according to a unique
interface.
3.
The security appliance records that a session is established.
4.
If the destination MAC address is in its table, the security appliance forwards the packet out of the
outside interface. The destination MAC address is that of the upstream router, 209.186.201.2.
If the destination MAC address is not in the security appliance table, the security appliance attempts
to discover the MAC address by sending an ARP request and a ping. The first packet is dropped.
5.
The web server responds to the request; because the session is already established, the packet
bypasses the many lookups associated with a new connection.
6.
The security appliance forwards the packet to the inside user.
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An Outside User Visits a Web Server on the Inside Network
Figure 15-10 shows an outside user accessing the inside web server.
Figure 15-10
Outside to Inside
Host
Internet
209.165.201.2
Management IP
209.165.201.6
209.165.201.1
Web Server
209.165.200.225
92409
209.165.200.230
The following steps describe how data moves through the security appliance (see Figure 15-10):
1.
A user on the outside network requests a web page from the inside web server.
2.
The security appliance receives the packet and adds the source MAC address to the MAC address
table, if required. Because it is a new session, it verifies that the packet is allowed according to the
terms of the security policy (access lists, filters, AAA).
For multiple context mode, the security appliance first classifies the packet according to a unique
interface.
3.
The security appliance records that a session is established.
4.
If the destination MAC address is in its table, the security appliance forwards the packet out of the
inside interface. The destination MAC address is that of the downstream router, 209.186.201.1.
If the destination MAC address is not in the security appliance table, the security appliance attempts
to discover the MAC address by sending an ARP request and a ping. The first packet is dropped.
5.
The web server responds to the request; because the session is already established, the packet
bypasses the many lookups associated with a new connection.
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6.
The security appliance forwards the packet to the outside user.
An Outside User Attempts to Access an Inside Host
Figure 15-11 shows an outside user attempting to access a host on the inside network.
Figure 15-11
Outside to Inside
Host
Internet
209.165.201.2
92410
Management IP
209.165.201.6
Host
209.165.201.3
The following steps describe how data moves through the security appliance (see Figure 15-11):
1.
A user on the outside network attempts to reach an inside host.
2.
The security appliance receives the packet and adds the source MAC address to the MAC address
table, if required. Because it is a new session, it verifies if the packet is allowed according to the
terms of the security policy (access lists, filters, AAA).
For multiple context mode, the security appliance first classifies the packet according to a unique
interface.
3.
The packet is denied, and the security appliance drops the packet.
4.
If the outside user is attempting to attack the inside network, the security appliance employs many
technologies to determine if a packet is valid for an already established session.
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16
Identifying Traffic with Access Lists
This chapter describes how to identify traffic with access lists. This chapter includes the following
topics:
•
Access List Overview, page 16-1
•
Adding an Extended Access List, page 16-5
•
Adding an EtherType Access List, page 16-8
•
Adding a Standard Access List, page 16-10
•
Adding a Webtype Access List, page 16-11
•
Simplifying Access Lists with Object Grouping, page 16-11
•
Adding Remarks to Access Lists, page 16-17
•
Scheduling Extended Access List Activation, page 16-18
•
Logging Access List Activity, page 16-19
For information about IPv6 access lists, see the “Configuring IPv6 Access Lists” section on page 12-6.
Access List Overview
Access lists are made up of one or more Access Control Entries. An ACE is a single entry in an access
list that specifies a permit or deny rule, and is applied to a protocol, a source and destination IP address
or network, and optionally the source and destination ports.
Access lists are used in a variety of features. If your feature uses Modular Policy Framework, you can
use an access list to identify traffic within a traffic class map. For more information on Modular Policy
Framework, see Chapter 21, “Using Modular Policy Framework.”
This section includes the following topics:
•
Access List Types, page 16-2
•
Access Control Entry Order, page 16-2
•
Access Control Implicit Deny, page 16-3
•
IP Addresses Used for Access Lists When You Use NAT, page 16-3
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Access List Overview
Access List Types
Table 16-1 lists the types of access lists and some common uses for them.
Table 16-1
Access List Types and Common Uses
Access List Use
Access List Type
Description
Control network access for IP traffic
(routed and transparent mode)
Extended
The security appliance does not allow any traffic from a
lower security interface to a higher security interface
unless it is explicitly permitted by an extended access list.
Note
Identify traffic for AAA rules
Extended
To access the security appliance interface for
management access, you do not also need an
access list allowing the host IP address. You only
need to configure management access according
to Chapter 40, “Managing System Access.”
AAA rules use access lists to identify traffic.
Control network access for IP traffic for a Extended,
given user
downloaded from a
AAA server per user
You can configure the RADIUS server to download a
dynamic access list to be applied to the user, or the server
can send the name of an access list that you already
configured on the security appliance.
Identify addresses for NAT (policy NAT
and NAT exemption)
Extended
Policy NAT lets you identify local traffic for address
translation by specifying the source and destination
addresses in an extended access list.
Establish VPN access
Extended
You can use an extended access list in VPN commands.
Identify traffic in a traffic class map for
Modular Policy Framework
Extended
Access lists can be used to identify traffic in a class map,
which is used for features that support Modular Policy
Framework. Features that support Modular Policy
Framework include TCP and general connection settings,
and inspection.
For transparent firewall mode, control
network access for non-IP traffic
EtherType
You can configure an access list that controls traffic based
on its EtherType.
Identify OSPF route redistribution
Standard
Standard access lists include only the destination address.
You can use a standard access list to control the
redistribution of OSPF routes.
Filtering for WebVPN
Webtype
You can configure a Webtype access list to filter URLs.
EtherType
Access Control Entry Order
An access list is made up of one or more Access Control Entries. Depending on the access list type, you
can specify the source and destination addresses, the protocol, the ports (for TCP or UDP), the ICMP
type (for ICMP), or the EtherType.
Each ACE that you enter for a given access list name is appended to the end of the access list.
The order of ACEs is important. When the security appliance decides whether to forward or drop a
packet, the security appliance tests the packet against each ACE in the order in which the entries are
listed. After a match is found, no more ACEs are checked. For example, if you create an ACE at the
beginning of an access list that explicitly permits all traffic, no further statements are ever checked.
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Access List Overview
You can disable an ACE by specifying the keyword inactive in the access-list command.
Access Control Implicit Deny
Access lists have an implicit deny at the end of the list, so unless you explicitly permit it, traffic cannot
pass. For example, if you want to allow all users to access a network through the security appliance
except for particular addresses, then you need to deny the particular addresses and then permit all others.
For EtherType access lists, the implicit deny at the end of the access list does not affect IP traffic or
ARPs; for example, if you allow EtherType 8037, the implicit deny at the end of the access list does not
now block any IP traffic that you previously allowed with an extended access list (or implicitly allowed
from a high security interface to a low security interface). However, if you explicitly deny all traffic with
an EtherType ACE, then IP and ARP traffic is denied.
IP Addresses Used for Access Lists When You Use NAT
When you use NAT, the IP addresses you specify for an access list depend on the interface to which the
access list is attached; you need to use addresses that are valid on the network connected to the interface.
This guideline applies for both inbound and outbound access lists: the direction does not determine the
address used, only the interface does.
For example, you want to apply an access list to the inbound direction of the inside interface. You
configure the security appliance to perform NAT on the inside source addresses when they access outside
addresses. Because the access list is applied to the inside interface, the source addresses are the original
untranslated addresses. Because the outside addresses are not translated, the destination address used in
the access list is the real address (see Figure 16-1).
Figure 16-1
IP Addresses in Access Lists: NAT Used for Source Addresses
209.165.200.225
Outside
Inside
Inbound ACL
Permit from 10.1.1.0/24 to 209.165.200.225
10.1.1.0/24
209.165.201.4:port
PAT
104634
10.1.1.0/24
See the following commands for this example:
hostname(config)# access-list INSIDE extended permit ip 10.1.1.0 255.255.255.0 host
209.165.200.225
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Access List Overview
hostname(config)# access-group INSIDE in interface inside
If you want to allow an outside host to access an inside host, you can apply an inbound access list on the
outside interface. You need to specify the translated address of the inside host in the access list because
that address is the address that can be used on the outside network (see Figure 16-2).
Figure 16-2
IP Addresses in Access Lists: NAT used for Destination Addresses
209.165.200.225
ACL
Permit from 209.165.200.225 to 209.165.201.5
Outside
10.1.1.34
209.165.201.5
Static NAT
104636
Inside
See the following commands for this example:
hostname(config)# access-list OUTSIDE extended permit ip host 209.165.200.225 host
209.165.201.5
hostname(config)# access-group OUTSIDE in interface outside
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Adding an Extended Access List
If you perform NAT on both interfaces, keep in mind the addresses that are visible to a given interface.
In Figure 16-3, an outside server uses static NAT so that a translated address appears on the inside
network.
Figure 16-3
IP Addresses in Access Lists: NAT used for Source and Destination Addresses
Static NAT
209.165.200.225
10.1.1.56
Outside
Inside
ACL
Permit from 10.1.1.0/24 to 10.1.1.56
10.1.1.0/24
209.165.201.4:port
PAT
104635
10.1.1.0/24
See the following commands for this example:
hostname(config)# access-list INSIDE extended permit ip 10.1.1.0 255.255.255.0 host
10.1.1.56
hostname(config)# access-group INSIDE in interface inside
Adding an Extended Access List
This section describes how to add an extended access list, and includes the following sections:
•
Extended Access List Overview, page 16-5
•
Allowing Broadcast and Multicast Traffic through the Transparent Firewall, page 16-6
•
Adding an Extended ACE, page 16-6
Extended Access List Overview
An extended access list is made up of one or more ACEs, in which you can specify the line number to
insert the ACE, source and destination addresses, and, depending on the ACE type, the protocol, the
ports (for TCP or UDP), or the ICMP type (for ICMP). You can identify all of these parameters within
the access-list command, or you can use object groups for each parameter. This section describes how
to identify the parameters within the command. To use object groups, see the “Simplifying Access Lists
with Object Grouping” section on page 16-11.
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Adding an Extended Access List
For information about logging options that you can add to the end of the ACE, see the “Logging Access
List Activity” section on page 16-19. For information about time range options, see “Scheduling
Extended Access List Activation” section on page 16-18.
For TCP and UDP connections, you do not need an access list to allow returning traffic, because the
FWSM allows all returning traffic for established, bidirectional connections. For connectionless
protocols such as ICMP, however, the security appliance establishes unidirectional sessions, so you
either need access lists to allow ICMP in both directions (by applying access lists to the source and
destination interfaces), or you need to enable the ICMP inspection engine. The ICMP inspection engine
treats ICMP sessions as bidirectional connections.
You can apply only one access list of each type (extended and EtherType) to each direction of an
interface. You can apply the same access lists on multiple interfaces. See Chapter 18, “Permitting or
Denying Network Access,” for more information about applying an access list to an interface.
Note
If you change the access list configuration, and you do not want to wait for existing connections to time
out before the new access list information is used, you can clear the connections using the clear
local-host command.
Allowing Broadcast and Multicast Traffic through the Transparent Firewall
In routed firewall mode, broadcast and multicast traffic is blocked even if you allow it in an access list,
including unsupported dynamic routing protocols and DHCP (unless you configure DHCP relay).
Transparent firewall mode can allow any IP traffic through. This feature is especially useful in multiple
context mode, which does not allow dynamic routing, for example.
Note
Because these special types of traffic are connectionless, you need to apply an extended access list to
both interfaces, so returning traffic is allowed through.
Table 16-2 lists common traffic types that you can allow through the transparent firewall.
Table 16-2
Transparent Firewall Special Traffic
Traffic Type
Protocol or Port
Notes
DHCP
UDP ports 67 and 68
If you enable the DHCP server, then the security
appliance does not pass DHCP packets.
EIGRP
Protocol 88
—
OSPF
Protocol 89
—
Multicast streams The UDP ports vary depending
on the application.
Multicast streams are always destined to a
Class D address (224.0.0.0 to 239.x.x.x).
RIP (v1 or v2)
—
UDP port 520
Adding an Extended ACE
When you enter the access-list command for a given access list name, the ACE is added to the end of
the access list unless you specify the line number.
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Adding an Extended Access List
To add an ACE, enter the following command:
hostname(config)# access-list access_list_name [line line_number] [extended]
{deny | permit} protocol source_address mask [operator port] dest_address mask
[operator port | icmp_type] [inactive]
Tip
Enter the access list name in upper case letters so the name is easy to see in the configuration. You might
want to name the access list for the interface (for example, INSIDE), or for the purpose for which it is
created (for example, NO_NAT or VPN).
Typically, you identify the ip keyword for the protocol, but other protocols are accepted. For a list of
protocol names, see the “Protocols and Applications” section on page D-11.
Enter the host keyword before the IP address to specify a single address. In this case, do not enter a mask.
Enter the any keyword instead of the address and mask to specify any address.
You can specify the source and destination ports only for the tcp or udp protocols. For a list of permitted
keywords and well-known port assignments, see the “TCP and UDP Ports” section on page D-11. DNS,
Discard, Echo, Ident, NTP, RPC, SUNRPC, and Talk each require one definition for TCP and one for
UDP. TACACS+ requires one definition for port 49 on TCP.
Use an operator to match port numbers used by the source or destination. The permitted operators are
as follows:
•
lt—less than
•
gt—greater than
•
eq—equal to
•
neq—not equal to
•
range—an inclusive range of values. When you use this operator, specify two port numbers, for
example:
range 100 200
You can specify the ICMP type only for the icmp protocol. Because ICMP is a connectionless protocol,
you either need access lists to allow ICMP in both directions (by applying access lists to the source and
destination interfaces), or you need to enable the ICMP inspection engine (see the “Adding an ICMP
Type Object Group” section on page 16-14). The ICMP inspection engine treats ICMP sessions as
stateful connections. To control ping, specify echo-reply (0) (security appliance to host) or echo (8)
(host to security appliance). See the “Adding an ICMP Type Object Group” section on page 16-14 for a
list of ICMP types.
When you specify a network mask, the method is different from the Cisco IOS software access-list
command. The security appliance uses a network mask (for example, 255.255.255.0 for a Class C mask).
The Cisco IOS mask uses wildcard bits (for example, 0.0.0.255).
To make an ACE inactive, use the inactive keyword. To reenable it, enter the entire ACE without the
inactive keyword. This feature lets you keep a record of an inactive ACE in your configuration to make
reenabling easier.
See the following examples:
The following access list allows all hosts (on the interface to which you apply the access list) to go
through the security appliance:
hostname(config)# access-list ACL_IN extended permit ip any any
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Adding an EtherType Access List
The following sample access list prevents hosts on 192.168.1.0/24 from accessing the 209.165.201.0/27
network. All other addresses are permitted.
hostname(config)# access-list ACL_IN extended deny tcp 192.168.1.0 255.255.255.0
209.165.201.0 255.255.255.224
hostname(config)# access-list ACL_IN extended permit ip any any
If you want to restrict access to only some hosts, then enter a limited permit ACE. By default, all other
traffic is denied unless explicitly permitted.
hostname(config)# access-list ACL_IN extended permit ip 192.168.1.0 255.255.255.0
209.165.201.0 255.255.255.224
The following access list restricts all hosts (on the interface to which you apply the access list) from
accessing a website at address 209.165.201.29. All other traffic is allowed.
hostname(config)# access-list ACL_IN extended deny tcp any host 209.165.201.29 eq www
hostname(config)# access-list ACL_IN extended permit ip any any
Adding an EtherType Access List
Transparent firewall mode only
This section describes how to add an EtherType access list, and includes the following sections:
•
EtherType Access List Overview, page 16-8
•
Adding an EtherType ACE, page 16-10
EtherType Access List Overview
An EtherType access list is made up of one or more ACEs that specify an EtherType. This section
includes the following topics:
•
Supported EtherTypes, page 16-8
•
Implicit Permit of IP and ARPs Only, page 16-9
•
Implicit and Explicit Deny ACE at the End of an Access List, page 16-9
•
IPv6 Unsupported, page 16-9
•
Using Extended and EtherType Access Lists on the Same Interface, page 16-9
•
Allowing MPLS, page 16-9
Supported EtherTypes
An EtherType ACE controls any EtherType identified by a 16-bit hexadecimal number.
EtherType access lists support Ethernet V2 frames.
802.3-formatted frames are not handled by the access list because they use a length field as opposed to
a type field.
BPDUs, which are handled by the access list, are the only exception: they are SNAP-encapsulated, and
the security appliance is designed to specifically handle BPDUs.
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Adding an EtherType Access List
The security appliance receives trunk port (Cisco proprietary) BPDUs. Trunk BPDUs have VLAN
information inside the payload, so the security appliance modifies the payload with the outgoing VLAN
if you allow BPDUs.
Note
If you use failover, you must allow BPDUs on both interfaces with an EtherType access list to avoid
bridging loops.
Implicit Permit of IP and ARPs Only
IPv4 traffic is allowed through the transparent firewall automatically from a higher security interface to
a lower security interface, without an access list. ARPs are allowed through the transparent firewall in
both directions without an access list. ARP traffic can be controlled by ARP inspection.
However, to allow any traffic with EtherTypes other than IPv4 and ARP, you need to apply an EtherType
access list, even from a high security to a low security interface.
Because EtherTypes are connectionless, you need to apply the access list to both interfaces if you want
traffic to pass in both directions.
Implicit and Explicit Deny ACE at the End of an Access List
For EtherType access lists, the implicit deny at the end of the access list does not affect IP traffic or
ARPs; for example, if you allow EtherType 8037, the implicit deny at the end of the access list does not
now block any IP traffic that you previously allowed with an extended access list (or implicitly allowed
from a high security interface to a low security interface). However, if you explicitly deny all traffic with
an EtherType ACE, then IP and ARP traffic is denied.
IPv6 Unsupported
EtherType ACEs do not allow IPv6 traffic, even if you specify the IPv6 EtherType.
Using Extended and EtherType Access Lists on the Same Interface
You can apply only one access list of each type (extended and EtherType) to each direction of an
interface. You can also apply the same access lists on multiple interfaces.
Allowing MPLS
If you allow MPLS, ensure that Label Distribution Protocol and Tag Distribution Protocol TCP
connections are established through the security appliance by configuring both MPLS routers connected
to the security appliance to use the IP address on the security appliance interface as the router-id for LDP
or TDP sessions. (LDP and TDP allow MPLS routers to negotiate the labels (addresses) used to forward
packets.)
On Cisco IOS routers, enter the appropriate command for your protocol, LDP or TDP. The interface is
the interface connected to the security appliance.
hostname(config)# mpls ldp router-id interface force
Or
hostname(config)# tag-switching tdp router-id interface force
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Adding a Standard Access List
Adding an EtherType ACE
To add an EtherType ACE, enter the following command:
hostname(config)# access-list access_list_name ethertype {permit | deny} {ipx | bpdu |
mpls-unicast | mpls-multicast | any | hex_number}
The hex_number is any EtherType that can be identified by a 16-bit hexadecimal number greater than or
equal to 0x600. See RFC 1700, “Assigned Numbers,” at http://www.ietf.org/rfc/rfc1700.txt for a list of
EtherTypes.
Note
If an EtherType access list is configured to deny all, all ethernet frames are discarded. Only physical
protocol traffic, such as auto-negotiation, is still allowed.
When you enter the access-list command for a given access list name, the ACE is added to the end of
the access list.
Tip
Enter the access_list_name in upper case letters so the name is easy to see in the configuration. You
might want to name the access list for the interface (for example, INSIDE), or for the purpose (for
example, MPLS or IPX).
For example, the following sample access list allows common EtherTypes originating on the inside
interface:
hostname(config)#
hostname(config)#
hostname(config)#
hostname(config)#
access-list ETHER ethertype permit ipx
access-list ETHER ethertype permit bpdu
access-list ETHER ethertype permit mpls-unicast
access-group ETHER in interface inside
The following access list allows some EtherTypes through the security appliance, but denies IPX:
hostname(config)#
hostname(config)#
hostname(config)#
hostname(config)#
hostname(config)#
hostname(config)#
access-list ETHER ethertype deny ipx
access-list ETHER ethertype permit 0x1234
access-list ETHER ethertype permit bpdu
access-list ETHER ethertype permit mpls-unicast
access-group ETHER in interface inside
access-group ETHER in interface outside
The following access list denies traffic with EtherType 0x1256, but allows all others on both interfaces:
hostname(config)#
hostname(config)#
hostname(config)#
hostname(config)#
access-list nonIP ethertype deny 1256
access-list nonIP ethertype permit any
access-group ETHER in interface inside
access-group ETHER in interface outside
Adding a Standard Access List
Single context mode only
Standard access lists identify the destination IP addresses of OSPF routes, and can be used in a route
map for OSPF redistribution. Standard access lists cannot be applied to interfaces to control traffic.
The following command adds a standard ACE. To add another ACE at the end of the access list, enter
another access-list command specifying the same access list name. Apply the access list using the
“Defining Route Maps” section on page 9-7.
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Adding a Webtype Access List
To add an ACE, enter the following command:
hostname(config)# access-list access_list_name standard {deny | permit} {any | ip_address
mask}
The following sample access list identifies routes to 192.168.1.0/24:
hostname(config)# access-list OSPF standard permit 192.168.1.0 255.255.255.0
Adding a Webtype Access List
To add an access list to the configuration that supports filtering for WebVPN, enter the following
command:
hostname(config)# access-list access_list_name webtype {deny
|
permit} url [url_string | any]
For information about logging options that you can add to the end of the ACE, see the “Logging Access
List Activity” section on page 16-19.
Simplifying Access Lists with Object Grouping
This section describes how to use object grouping to simplify access list creation and maintenance.
This section includes the following topics:
•
How Object Grouping Works, page 16-11
•
Adding Object Groups, page 16-12
•
Nesting Object Groups, page 16-15
•
Displaying Object Groups, page 16-17
•
Removing Object Groups, page 16-17
•
Using Object Groups with an Access List, page 16-16
How Object Grouping Works
By grouping like-objects together, you can use the object group in an ACE instead of having to enter an
ACE for each object separately. You can create the following types of object groups:
•
Protocol
•
Network
•
Service
•
ICMP type
For example, consider the following three object groups:
•
MyServices—Includes the TCP and UDP port numbers of the service requests that are allowed
access to the internal network
•
TrustedHosts—Includes the host and network addresses allowed access to the greatest range of
services and servers
•
PublicServers—Includes the host addresses of servers to which the greatest access is provided
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After creating these groups, you could use a single ACE to allow trusted hosts to make specific service
requests to a group of public servers.
You can also nest object groups in other object groups.
Note
The ACE system limit applies to expanded access lists. If you use object groups in ACEs, the number of
actual ACEs that you enter is fewer, but the number of expanded ACEs is the same as without object
groups. In many cases, object groups create more ACEs than if you added them manually, because
creating ACEs manually leads you to summarize addresses more than an object group does. To view the
number of expanded ACEs in an access list, enter the show access-list access_list_name command.
Adding Object Groups
This section describes how to add object groups.
This section includes the following topics:
•
Adding a Protocol Object Group, page 16-12
•
Adding a Network Object Group, page 16-13
•
Adding a Service Object Group, page 16-13
•
Adding an ICMP Type Object Group, page 16-14
Adding a Protocol Object Group
To add or change a protocol object group, follow these steps. After you add the group, you can add more
objects as required by following this procedure again for the same group name and specifying additional
objects. You do not need to reenter existing objects; the commands you already set remain in place unless
you remove them with the no form of the command.
To add a protocol group, follow these steps:
Step 1
To add a protocol group, enter the following command:
hostname(config)# object-group protocol grp_id
The grp_id is a text string up to 64 characters in length.
The prompt changes to protocol configuration mode.
Step 2
(Optional) To add a description, enter the following command:
hostname(config-protocol)# description text
The description can be up to 200 characters.
Step 3
To define the protocols in the group, enter the following command for each protocol:
hostname(config-protocol)# protocol-object protocol
The protocol is the numeric identifier of the specific IP protocol (1 to 254) or a keyword identifier (for
example, icmp, tcp, or udp). To include all IP protocols, use the keyword ip. For a list of protocols you
can specify, see the “Protocols and Applications” section on page D-11.
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For example, to create a protocol group for TCP, UDP, and ICMP, enter the following commands:
hostname(config)# object-group protocol tcp_udp_icmp
hostname(config-protocol)# protocol-object tcp
hostname(config-protocol)# protocol-object udp
hostname(config-protocol)# protocol-object icmp
Adding a Network Object Group
To add or change a network object group, follow these steps. After you add the group, you can add more
objects as required by following this procedure again for the same group name and specifying additional
objects. You do not need to reenter existing objects; the commands you already set remain in place unless
you remove them with the no form of the command.
Note
A network object group supports IPv4 and IPv6 addresses, depending on the type of access list. For more
information about IPv6 access lists, see “Configuring IPv6 Access Lists” section on page 12-6.
To add a network group, follow these steps:
Step 1
To add a network group, enter the following command:
hostname(config)# object-group network grp_id
The grp_id is a text string up to 64 characters in length.
The prompt changes to network configuration mode.
Step 2
(Optional) To add a description, enter the following command:
hostname(config-network)# description text
The description can be up to 200 characters.
Step 3
To define the networks in the group, enter the following command for each network or address:
hostname(config-network)# network-object {host ip_address | ip_address mask}
For example, to create network group that includes the IP addresses of three administrators, enter the
following commands:
hostname(config)# object-group network admins
hostname(config-network)# description Administrator Addresses
hostname(config-network)# network-object host 10.1.1.4
hostname(config-network)# network-object host 10.1.1.78
hostname(config-network)# network-object host 10.1.1.34
Adding a Service Object Group
To add or change a service object group, follow these steps. After you add the group, you can add more
objects as required by following this procedure again for the same group name and specifying additional
objects. You do not need to reenter existing objects; the commands you already set remain in place unless
you remove them with the no form of the command.
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To add a service group, follow these steps:
Step 1
To add a service group, enter the following command:
hostname(config)# object-group service grp_id {tcp | udp | tcp-udp}
The grp_id is a text string up to 64 characters in length.
Specify the protocol for the services (ports) you want to add, either tcp, udp, or tcp-udp keywords.
Enter tcp-udp keyword if your service uses both TCP and UDP with the same port number, for example,
DNS (port 53).
The prompt changes to service configuration mode.
Step 2
(Optional) To add a description, enter the following command:
hostname(config-service)# description text
The description can be up to 200 characters.
Step 3
To define the ports in the group, enter the following command for each port or range of ports:
hostname(config-service)# port-object {eq port | range begin_port end_port}
For a list of permitted keywords and well-known port assignments, see the “Protocols and Applications”
section on page D-11.
For example, to create service groups that include DNS (TCP/UDP), LDAP (TCP), and RADIUS (UDP),
enter the following commands:
hostname(config)# object-group service services1 tcp-udp
hostname(config-service)# description DNS Group
hostname(config-service)# port-object eq domain
hostname(config-service)#
hostname(config-service)#
hostname(config-service)#
hostname(config-service)#
object-group service services2 udp
description RADIUS Group
port-object eq radius
port-object eq radius-acct
hostname(config-service)# object-group service services3 tcp
hostname(config-service)# description LDAP Group
hostname(config-service)# port-object eq ldap
Adding an ICMP Type Object Group
To add or change an ICMP type object group, follow these steps. After you add the group, you can add
more objects as required by following this procedure again for the same group name and specifying
additional objects. You do not need to reenter existing objects; the commands you already set remain in
place unless you remove them with the no form of the command.
To add an ICMP type group, follow these steps:
Step 1
To add an ICMP type group, enter the following command:
hostname(config)# object-group icmp-type grp_id
The grp_id is a text string up to 64 characters in length.
The prompt changes to ICMP type configuration mode.
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Step 2
(Optional) To add a description, enter the following command:
hostname(config-icmp-type)# description text
The description can be up to 200 characters.
Step 3
To define the ICMP types in the group, enter the following command for each type:
hostname(config-icmp-type)# icmp-object icmp_type
See the “ICMP Types” section on page D-15 for a list of ICMP types.
For example, to create an ICMP type group that includes echo-reply and echo (for controlling ping),
enter the following commands:
hostname(config)# object-group icmp-type ping
hostname(config-service)# description Ping Group
hostname(config-icmp-type)# icmp-object echo
hostname(config-icmp-type)# icmp-object echo-reply
Nesting Object Groups
To nest an object group within another object group of the same type, first create the group that you want
to nest according to the “Adding Object Groups” section on page 16-12. Then follow these steps:
Step 1
To add or edit an object group under which you want to nest another object group, enter the following
command:
hostname(config)# object-group {{protocol | network | icmp-type} grp_id | service grp_id
{tcp | udp | tcp-udp}}
Step 2
To add the specified group under the object group you specified in Step 1, enter the following command:
hostname(config-group_type)# group-object grp_id
The nested group must be of the same type.
You can mix and match nested group objects and regular objects within an object group.
For example, you create network object groups for privileged users from various departments:
hostname(config)# object-group network eng
hostname(config-network)# network-object host 10.1.1.5
hostname(config-network)# network-object host 10.1.1.9
hostname(config-network)# network-object host 10.1.1.89
hostname(config-network)# object-group network hr
hostname(config-network)# network-object host 10.1.2.8
hostname(config-network)# network-object host 10.1.2.12
hostname(config-network)# object-group network finance
hostname(config-network)# network-object host 10.1.4.89
hostname(config-network)# network-object host 10.1.4.100
You then nest all three groups together as follows:
hostname(config)# object-group network admin
hostname(config-network)# group-object eng
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hostname(config-network)# group-object hr
hostname(config-network)# group-object finance
You only need to specify the admin object group in your ACE as follows:
hostname(config)# access-list ACL_IN extended permit ip object-group admin host
209.165.201.29
Using Object Groups with an Access List
To use object groups in an access list, replace the normal protocol (protocol), network
(source_address mask, etc.), service (operator port), or ICMP type (icmp_type) parameter with
object-group grp_id parameter.
For example, to use object groups for all available parameters in the access-list {tcp | udp} command,
enter the following command:
hostname(config)# access-list access_list_name [line line_number] [extended] {deny |
permit} {tcp | udp} object-group nw_grp_id [object-group svc_grp_id] object-group
nw_grp_id [object-group svc_grp_id] [log [[level] [interval secs] | disable | default]]
[inactive | time-range time_range_name]
You do not have to use object groups for all parameters; for example, you can use an object group for
the source address, but identify the destination address with an address and mask.
The following normal access list that does not use object groups restricts several hosts on the inside
network from accessing several web servers. All other traffic is allowed.
hostname(config)#
eq www
hostname(config)#
eq www
hostname(config)#
eq www
hostname(config)#
eq www
hostname(config)#
eq www
hostname(config)#
eq www
hostname(config)#
eq www
hostname(config)#
eq www
hostname(config)#
eq www
hostname(config)#
hostname(config)#
access-list ACL_IN extended deny tcp host 10.1.1.4 host 209.165.201.29
access-list ACL_IN extended deny tcp host 10.1.1.78 host 209.165.201.29
access-list ACL_IN extended deny tcp host 10.1.1.89 host 209.165.201.29
access-list ACL_IN extended deny tcp host 10.1.1.4 host 209.165.201.16
access-list ACL_IN extended deny tcp host 10.1.1.78 host 209.165.201.16
access-list ACL_IN extended deny tcp host 10.1.1.89 host 209.165.201.16
access-list ACL_IN extended deny tcp host 10.1.1.4 host 209.165.201.78
access-list ACL_IN extended deny tcp host 10.1.1.78 host 209.165.201.78
access-list ACL_IN extended deny tcp host 10.1.1.89 host 209.165.201.78
access-list ACL_IN extended permit ip any any
access-group ACL_IN in interface inside
If you make two network object groups, one for the inside hosts, and one for the web servers, then the
configuration can be simplified and can be easily modified to add more hosts:
hostname(config)# object-group network denied
hostname(config-network)# network-object host 10.1.1.4
hostname(config-network)# network-object host 10.1.1.78
hostname(config-network)# network-object host 10.1.1.89
hostname(config-network)#
hostname(config-network)#
hostname(config-network)#
hostname(config-network)#
object-group network web
network-object host 209.165.201.29
network-object host 209.165.201.16
network-object host 209.165.201.78
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hostname(config-network)# access-list ACL_IN extended deny tcp object-group denied
object-group web eq www
hostname(config)# access-list ACL_IN extended permit ip any any
hostname(config)# access-group ACL_IN in interface inside
Displaying Object Groups
To display a list of the currently configured object groups, enter the following command:
hostname(config)# show object-group [protocol | network | service | icmp-type | id grp_id]
If you enter the command without any parameters, the system displays all configured object groups.
The following is sample output from the show object-group command:
hostname# show object-group
object-group network ftp_servers
description: This is a group of FTP servers
network-object host 209.165.201.3
network-object host 209.165.201.4
object-group network TrustedHosts
network-object host 209.165.201.1
network-object 192.168.1.0 255.255.255.0
group-object ftp_servers
Removing Object Groups
To remove an object group, enter one of the following commands.
Note
You cannot remove an object group or make an object group empty if it is used in an access list.
•
To remove a specific object group, enter the following command:
hostname(config)# no object-group grp_id
•
To remove all object groups of the specified type, enter the following command:
hostname(config)# clear object-group [protocol | network | services | icmp-type]
If you do not enter a type, all object groups are removed.
Adding Remarks to Access Lists
You can include remarks about entries in any access list, including extended, EtherType, and standard
access lists. The remarks make the access list easier to understand.
To add a remark after the last access-list command you entered, enter the following command:
hostname(config)# access-list access_list_name remark text
If you enter the remark before any access-list command, then the remark is the first line in the access list.
If you delete an access list using the no access-list access_list_name command, then all the remarks are
also removed.
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The text can be up to 100 characters in length. You can enter leading spaces at the beginning of the text.
Trailing spaces are ignored.
For example, you can add remarks before each ACE, and the remark appears in the access list in this
location. Entering a dash (-) at the beginning of the remark helps set it apart from ACEs.
hostname(config)#
hostname(config)#
hostname(config)#
hostname(config)#
access-list
access-list
access-list
access-list
OUT
OUT
OUT
OUT
remark extended
remark extended
this is the inside admin address
permit ip host 209.168.200.3 any
this is the hr admin address
permit ip host 209.168.200.4 any
Scheduling Extended Access List Activation
You can schedule each ACE to be activated at specific times of the day and week by applying a time
range to the ACE. This section includes the following topics:
•
Adding a Time Range, page 16-18
•
Applying the Time Range to an ACE, page 16-19
Adding a Time Range
To add a time range to implement a time-based access list, perform the following steps:
Step 1
Identify the time-range name by entering the following command:
hostname(config)# time-range name
Step 2
Specify the time range as either a recurring time range or an absolute time range.
Multiple periodic entries are allowed per time-range command. If a time-range command has both
absolute and periodic values specified, then the periodic commands are evaluated only after the
absolute start time is reached, and are not further evaluated after the absolute end time is reached.
•
Recurring time range:
hostname(config-time-range)# periodic days-of-the-week time to [days-of-the-week] time
You can specify the following values for days-of-the-week:
– monday, tuesday, wednesday, thursday, friday, saturday, and sunday.
– daily
– weekdays
– weekend
The time is in the format hh:mm. For example, 8:00 is 8:00 a.m. and 20:00 is 8:00 p.m.
•
Absolute time range:
hostname(config-time-range)# absolute start time date [end time date]
The time is in the format hh:mm. For example, 8:00 is 8:00 a.m. and 20:00 is 8:00 p.m.
The date is in the format day month year; for example, 1 january 2006.
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The following is an example of an absolute time range beginning at 8:00 a.m. on January 1, 2006.
Because no end time and date are specified, the time range is in effect indefinitely.
hostname(config)# time-range for2006
hostname(config-time-range)# absolute start 8:00 1 january 2006
The following is an example of a weekly periodic time range from 8:00 a.m. to 6:00 p.m on weekdays.:
hostname(config)# time-range workinghours
hostname(config-time-range)# periodic weekdays 8:00 to 18:00
Applying the Time Range to an ACE
To apply the time range to an ACE, use the following command:
hostname(config)# access-list access_list_name [extended] {deny | permit}...[time-range
name]
See the “Adding an Extended Access List” section on page 16-5 for complete access-list command
syntax.
Note
If you also enable logging for the ACE, use the log keyword before the time-range keyword. If you
disable the ACE using the inactive keyword, use the inactive keyword as the last keyword.
The following example binds an access list named “Sales” to a time range named “New_York_Minute.”
hostname(config)# access-list Sales line 1 extended deny tcp host 209.165.200.225 host
209.165.201.1 time-range New_York_Minute
Logging Access List Activity
This section describes how to configure access list logging for extended access lists and Webtype access
lists.
This section includes the following topics:
•
Access List Logging Overview, page 16-19
•
Configuring Logging for an Access Control Entry, page 16-20
•
Managing Deny Flows, page 16-21
Access List Logging Overview
By default, when traffic is denied by an extended ACE or a Webtype ACE, the security appliance
generates system message 106023 for each denied packet, in the following form:
%ASA|PIX-4-106023: Deny protocol src [interface_name:source_address/source_port] dst
interface_name:dest_address/dest_port [type {string}, code {code}] by access_group acl_id
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If the security appliance is attacked, the number of system messages for denied packets can be very large.
We recommend that you instead enable logging using system message 106100, which provides statistics
for each ACE and lets you limit the number of system messages produced. Alternatively, you can disable
all logging.
Note
Only ACEs in the access list generate logging messages; the implicit deny at the end of the access list
does not generate a message. If you want all denied traffic to generate messages, add the implicit ACE
manually to the end of the access list, as follows.
hostname(config)# access-list TEST deny ip any any log
The log options at the end of the extended access-list command lets you to set the following behavior:
•
Enable message 106100 instead of message 106023
•
Disable all logging
•
Return to the default logging using message 106023
System message 106100 is in the following form:
%ASA|PIX-n-106100: access-list acl_id {permitted | denied} protocol
interface_name/source_address(source_port) -> interface_name/dest_address(dest_port)
hit-cnt number ({first hit | number-second interval})
When you enable logging for message 106100, if a packet matches an ACE, the security appliance
creates a flow entry to track the number of packets received within a specific interval. The security
appliance generates a system message at the first hit and at the end of each interval, identifying the total
number of hits during the interval. At the end of each interval, the security appliance resets the hit count
to 0. If no packets match the ACE during an interval, the security appliance deletes the flow entry.
A flow is defined by the source and destination IP addresses, protocols, and ports. Because the source
port might differ for a new connection between the same two hosts, you might not see the same flow
increment because a new flow was created for the connection. See the “Managing Deny Flows” section
on page 16-21 to limit the number of logging flows.
Permitted packets that belong to established connections do not need to be checked against access lists;
only the initial packet is logged and included in the hit count. For connectionless protocols, such as
ICMP, all packets are logged even if they are permitted, and all denied packets are logged.
See the Cisco Security Appliance Logging Configuration and System Log Messages for detailed
information about this system message.
Configuring Logging for an Access Control Entry
To configure logging for an ACE, see the following information about the log option:
hostname(config)# access-list access_list_name [extended] {deny | permit}...[log [[level]
[interval secs] | disable | default]]
See the “Adding an Extended Access List” section on page 16-5 and “Adding a Webtype Access List”
section on page 16-11 for complete access-list command syntax.
If you enter the log option without any arguments, you enable system log message 106100 at the default
level (6) and for the default interval (300 seconds). See the following options:
•
level—A severity level between 0 and 7. The default is 6.
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•
interval secs—The time interval in seconds between system messages, from 1 to 600. The default
is 300. This value is also used as the timeout value for deleting an inactive flow.
•
disable—Disables all access list logging.
•
default—Enables logging to message 106023. This setting is the same as having no log option.
For example, you configure the following access list:
hostname(config)#
hostname(config)#
hostname(config)#
hostname(config)#
access-list outside-acl permit ip host 1.1.1.1 any log 7 interval 600
access-list outside-acl permit ip host 2.2.2.2 any
access-list outside-acl deny ip any any log 2
access-group outside-acl in interface outside
When a packet is permitted by the first ACE of outside-acl, the security appliance generates the
following system message:
%ASA|PIX-7-106100: access-list outside-acl permitted tcp outside/1.1.1.1(12345) ->
inside/192.168.1.1(1357) hit-cnt 1 (first hit)
Although 20 additional packets for this connection arrive on the outside interface, the traffic does not
have to be checked against the access list, and the hit count does not increase.
If one more connection by the same host is initiated within the specified 10 minute interval (and the
source and destination ports remain the same), then the hit count is incremented by 1 and the following
message is displayed at the end of the 10 minute interval:
%ASA|PIX-7-106100: access-list outside-acl permitted tcp outside/1.1.1.1(12345)->
inside/192.168.1.1(1357) hit-cnt 2 (600-second interval)
When a packet is denied by the third ACE, the security appliance generates the following system
message:
%ASA|PIX-2-106100: access-list outside-acl denied ip outside/3.3.3.3(12345) ->
inside/192.168.1.1(1357) hit-cnt 1 (first hit)
20 additional attempts within a 5 minute interval (the default) result in the following message at the end
of 5 minutes:
%ASA|PIX-2-106100: access-list outside-acl denied ip outside/3.3.3.3(12345) ->
inside/192.168.1.1(1357) hit-cnt 21 (300-second interval)
Managing Deny Flows
When you enable logging for message 106100, if a packet matches an ACE, the security appliance
creates a flow entry to track the number of packets received within a specific interval. The security
appliance has a maximum of 32 K logging flows for ACEs. A large number of flows can exist
concurrently at any point of time. To prevent unlimited consumption of memory and CPU resources, the
security appliance places a limit on the number of concurrent deny flows; the limit is placed only on deny
flows (and not permit flows) because they can indicate an attack. When the limit is reached, the security
appliance does not create a new deny flow for logging until the existing flows expire.
For example, if someone initiates a DoS attack, the security appliance can create a large number of deny
flows in a short period of time. Restricting the number of deny flows prevents unlimited consumption of
memory and CPU resources.
When you reach the maximum number of deny flows, the security appliance issues system message
106100:
%ASA|PIX-1-106101: The number of ACL log deny-flows has reached limit (number).
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Identifying Traffic with Access Lists
Logging Access List Activity
To configure the maximum number of deny flows and to set the interval between deny flow alert
messages (106101), enter the following commands:
•
To set the maximum number of deny flows permitted per context before the security appliance stops
logging, enter the following command:
hostname(config)# access-list deny-flow-max number
The number is between 1 and 4096. 4096 is the default.
•
To set the amount of time between system messages (number 106101) that identify that the
maximum number of deny flows was reached, enter the following command:
hostname(config)# access-list alert-interval secs
The seconds are between 1 and 3600. 300 is the default.
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17
Applying NAT
This chapter describes Network Address Translation (NAT). In routed firewall mode, the security
appliance can perform NAT between each network.
Note
In transparent firewall mode, the security appliance does not support NAT.
This chapter contains the following sections:
•
NAT Overview, page 17-1
•
Configuring NAT Control, page 17-15
•
Using Dynamic NAT and PAT, page 17-16
•
Using Static NAT, page 17-25
•
Using Static PAT, page 17-26
•
Bypassing NAT, page 17-28
•
NAT Examples, page 17-32
NAT Overview
This section describes how NAT works on the security appliance, and includes the following topics:
•
Introduction to NAT, page 17-2
•
NAT Control, page 17-3
•
NAT Types, page 17-5
•
Policy NAT, page 17-9
•
NAT and Same Security Level Interfaces, page 17-12
•
Order of NAT Commands Used to Match Real Addresses, page 17-13
•
Mapped Address Guidelines, page 17-13
•
DNS and NAT, page 17-14
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Introduction to NAT
Address translation substitutes the real address in a packet with a mapped address that is routable on the
destination network. NAT is comprised of two steps: the process in which a real address is translated into
a mapped address, and then the process to undo translation for returning traffic.
The security appliance translates an address when a NAT rule matches the traffic. If no NAT rule
matches, processing for the packet continues. The exception is when you enable NAT control.
NAT control requires that packets traversing from a higher security interface (inside) to a lower security
interface (outside) match a NAT rule, or else processing for the packet stops. (See the “Security Level
Overview” section on page 7-1 for more information about security levels, and see “NAT Control”
section on page 17-3 for more information about NAT control).
Note
In this document, all types of translation are generally referred to as NAT. When discussing NAT, the
terms inside and outside are relative, and represent the security relationship between any two interfaces.
The higher security level is inside and the lower security level is outside; for example, interface 1 is at
60 and interface 2 is at 50, so interface 1 is “inside” and interface 2 is “outside.”
Some of the benefits of NAT are as follows:
•
You can use private addresses on your inside networks. Private addresses are not routable on the
Internet. (See the “Private Networks” section on page D-2 for more information.)
•
NAT hides the real addresses from other networks, so attackers cannot learn the real address of a
host.
•
You can resolve IP routing problems such as overlapping addresses.
See Table 25-1 on page 25-3 for information about protocols that do not support NAT.
Figure 17-1 shows a typical NAT scenario, with a private network on the inside. When the inside host at
10.1.2.27 sends a packet to a web server, the real source address, 10.1.2.27, of the packet is changed to
a mapped address, 209.165.201.10. When the server responds, it sends the response to the mapped
address, 209.165.201.10, and the security appliance receives the packet. The security appliance then
undoes the translation of the mapped address, 209.165.201.10 back to the real address, 10.1.2.27 before
sending it on to the host.
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NAT Overview
Figure 17-1
NAT Example
Web Server
www.cisco.com
Outside
209.165.201.2
Originating
Packet
Security
Appliance
Translation
10.1.2.27
209.165.201.10
Responding
Packet
Undo Translation
209.165.201.10
10.1.2.27
10.1.2.1
10.1.2.27
130023
Inside
See the following commands for this example:
hostname(config)# nat (inside) 1 10.1.2.0 255.255.255.0
hostname(config)# global (outside) 1 209.165.201.1-209.165.201.15
NAT Control
NAT control requires that packets traversing from an inside interface to an outside interface match a NAT
rule; for any host on the inside network to access a host on the outside network, you must configure NAT
to translate the inside host address (see Figure 17-2).
Figure 17-2
NAT Control and Outbound Traffic
Security
Appliance
10.1.1.1
NAT
209.165.201.1
Inside
Outside
132212
10.1.2.1 No NAT
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NAT Overview
Interfaces at the same security level are not required to use NAT to communicate. However, if you
configure dynamic NAT or PAT on a same security interface, then all traffic from the interface to a same
security interface or an outside interface must match a NAT rule (see Figure 17-3).
Figure 17-3
NAT Control and Same Security Traffic
Security
Appliance
Security
Appliance
10.1.1.1 Dyn. NAT
10.1.1.1 No NAT
209.165.201.1
10.1.1.1
10.1.2.1 No NAT
Level 50
Level 50
Level 50
or
Outside
132215
Level 50
Similarly, if you enable outside dynamic NAT or PAT, then all outside traffic must match a NAT rule
when it accesses an inside interface (see Figure 17-4).
NAT Control and Inbound Traffic
Security
Appliance
Security
Appliance
209.165.202.129 Dyn. NAT
209.165.202.129 No NAT
Outside
209.165.202.129
10.1.1.50
209.165.200.240 No NAT
Inside
Outside
Inside
132213
Figure 17-4
Static NAT does not cause these restrictions.
By default, NAT control is disabled, so you do not need to perform NAT on any networks unless you
choose to perform NAT. If you upgraded from an earlier version of software, however, NAT control
might be enabled on your system. Even with NAT control disabled, you need to perform NAT on any
addresses for which you configure dynamic NAT. See the “Dynamic NAT and PAT Implementation”
section on page 17-16 for more information on how dynamic NAT is applied.
If you want the added security of NAT control but do not want to translate inside addresses in some cases,
you can apply a NAT exemption or identity NAT rule on those addresses. (See the “Bypassing NAT”
section on page 17-28 for more information).
To configure NAT control, see the “Configuring NAT Control” section on page 17-15.
Note
In multiple context mode, the packet classifier might rely on the NAT configuration to assign packets to
contexts if you do not enable unique MAC addresses for shared interfaces. See the “How the Security
Appliance Classifies Packets” section on page 3-3 for more information about the relationship between
the classifier and NAT.
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NAT Overview
NAT Types
This section describes the available NAT types. You can implement address translation as dynamic NAT,
Port Address Translation, static NAT, or static PAT or as a mix of these types. You can also configure
rules to bypass NAT, for example, if you enable NAT control but do not want to perform NAT. This
section includes the following topics:
•
Dynamic NAT, page 17-5
•
PAT, page 17-7
•
Static NAT, page 17-7
•
Static PAT, page 17-8
•
Bypassing NAT When NAT Control is Enabled, page 17-9
Dynamic NAT
Dynamic NAT translates a group of real addresses to a pool of mapped addresses that are routable on the
destination network. The mapped pool can include fewer addresses than the real group. When a host you
want to translate accesses the destination network, the security appliance assigns it an IP address from
the mapped pool. The translation is added only when the real host initiates the connection. The
translation is in place only for the duration of the connection, and a given user does not keep the same
IP address after the translation times out (see the timeout xlate command in the Cisco Security
Appliance Command Reference). Users on the destination network, therefore, cannot reliably initiate a
connection to a host that uses dynamic NAT (even if the connection is allowed by an access list), and the
security appliance rejects any attempt to connect to a real host address directly. See the following “Static
NAT” or “Static PAT” sections for reliable access to hosts.
Note
In some cases, a translation is added for a connection (see the show xlate command) even though the
session is denied by the security appliance. This condition occurs with an outbound access list, a
management-only interface, or a backup interface. The translation times out normally.
Figure 17-5 shows a remote host attempting to connect to the real address. The connection is denied
because the security appliance only allows returning connections to the mapped address.
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Figure 17-5
Remote Host Attempts to Connect to the Real Address
Web Server
www.example.com
Outside
209.165.201.2
Security
Appliance
Translation
10.1.2.27
209.165.201.10
10.1.2.27
10.1.2.1
132216
Inside
10.1.2.27
Figure 17-6 shows a remote host attempting to initiate a connection to a mapped address. This address
is not currently in the translation table, so the security appliance drops the packet.
Figure 17-6
Remote Host Attempts to Initiate a Connection to a Mapped Address
Web Server
www.example.com
Outside
209.165.201.2
Security
Appliance
209.165.201.10
10.1.2.1
132217
Inside
10.1.2.27
Note
For the duration of the translation, a remote host can initiate a connection to the translated host if an
access list allows it. Because the address is unpredictable, a connection to the host is unlikely. However
in this case, you can rely on the security of the access list.
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NAT Overview
Dynamic NAT has these disadvantages:
•
If the mapped pool has fewer addresses than the real group, you could run out of addresses if the
amount of traffic is more than expected.
Use PAT if this event occurs often, because PAT provides over 64,000 translations using ports of a
single address.
•
You have to use a large number of routable addresses in the mapped pool; if the destination network
requires registered addresses, such as the Internet, you might encounter a shortage of usable
addresses.
The advantage of dynamic NAT is that some protocols cannot use PAT. For example, PAT does not work
with IP protocols that do not have a port to overload, such as GRE version 0. PAT also does not work
with some applications that have a data stream on one port and the control path on another and are not
open standard, such as some multimedia applications. See the “When to Use Application Protocol
Inspection” section on page 25-2 for more information about NAT and PAT support.
PAT
PAT translates multiple real addresses to a single mapped IP address. Specifically, the security appliance
translates the real address and source port (real socket) to the mapped address and a unique port above
1024 (mapped socket). Each connection requires a separate translation, because the source port differs
for each connection. For example, 10.1.1.1:1025 requires a separate translation from 10.1.1.1:1026.
After the connection expires, the port translation also expires after 30 seconds of inactivity. The timeout
is not configurable. Users on the destination network cannot reliably initiate a connection to a host that
uses PAT (even if the connection is allowed by an access list). Not only can you not predict the real or
mapped port number of the host, but the security appliance does not create a translation at all unless the
translated host is the initiator. See the following “Static NAT” or “Static PAT” sections for reliable access
to hosts.
PAT lets you use a single mapped address, thus conserving routable addresses. You can even use the
security appliance interface IP address as the PAT address. PAT does not work with some multimedia
applications that have a data stream that is different from the control path. See the “When to Use
Application Protocol Inspection” section on page 25-2 for more information about NAT and PAT
support.
Note
For the duration of the translation, a remote host can initiate a connection to the translated host if an
access list allows it. Because the port address (both real and mapped) is unpredictable, a connection to
the host is unlikely. Nevertheless, in this case, you can rely on the security of the access list. However,
policy PAT does not support time-based ACLs.
Static NAT
Static NAT creates a fixed translation of real address(es) to mapped address(es).With dynamic NAT and
PAT, each host uses a different address or port for each subsequent translation. Because the mapped
address is the same for each consecutive connection with static NAT, and a persistent translation rule
exists, static NAT allows hosts on the destination network to initiate traffic to a translated host (if there
is an access list that allows it).
The main difference between dynamic NAT and a range of addresses for static NAT is that static NAT
allows a remote host to initiate a connection to a translated host (if there is an access list that allows it),
while dynamic NAT does not. You also need an equal number of mapped addresses as real addresses with
static NAT.
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Static PAT
Static PAT is the same as static NAT, except it lets you specify the protocol (TCP or UDP) and port for
the real and mapped addresses.
This feature lets you identify the same mapped address across many different static statements, so long
as the port is different for each statement (you cannot use the same mapped address for multiple static
NAT statements).
For applications that require application inspection for secondary channels (FTP, VoIP, etc.), the security
appliance automatically translates the secondary ports.
For example, if you want to provide a single address for remote users to access FTP, HTTP, and SMTP,
but these are all actually different servers on the real network, you can specify static PAT statements for
each server that uses the same mapped IP address, but different ports (see Figure 17-7).
Figure 17-7
Static PAT
Host
Undo Translation
209.165.201.3:21
10.1.2.27
Outside
Undo Translation
209.165.201.3:25
10.1.2.29
Undo Translation
209.165.201.3:80
10.1.2.28
Inside
SMTP server
10.1.2.29
HTTP server
10.1.2.28
130031
FTP server
10.1.2.27
See the following commands for this example:
hostname(config)# static (inside,outside) tcp 209.165.201.3 ftp 10.1.2.27 ftp netmask
255.255.255.255
hostname(config)# static (inside,outside) tcp 209.165.201.3 http 10.1.2.28 http netmask
255.255.255.255
hostname(config)# static (inside,outside) tcp 209.165.201.3 smtp 10.1.2.29 smtp netmask
255.255.255.255
You can also use static PAT to translate a well-known port to a non-standard port or vice versa. For
example, if your inside web servers use port 8080, you can allow outside users to connect to port 80, and
then undo translation to the original port 8080. Similarly, if you want to provide extra security, you can
tell your web users to connect to non-standard port 6785, and then undo translation to port 80.
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Bypassing NAT When NAT Control is Enabled
If you enable NAT control, then inside hosts must match a NAT rule when accessing outside hosts. If
you do not want to perform NAT for some hosts, then you can bypass NAT for those hosts (alternatively,
you can disable NAT control). You might want to bypass NAT, for example, if you are using an
application that does not support NAT (see the “When to Use Application Protocol Inspection” section
on page 25-2 for information about inspection engines that do not support NAT).
You can configure traffic to bypass NAT using one of three methods. All methods achieve compatibility
with inspection engines. However, each method offers slightly different capabilities, as follows:
•
Identity NAT (nat 0 command)—When you configure identity NAT (which is similar to dynamic
NAT), you do not limit translation for a host on specific interfaces; you must use identity NAT for
connections through all interfaces. Therefore, you cannot choose to perform normal translation on
real addresses when you access interface A, but use identity NAT when accessing interface B.
Regular dynamic NAT, on the other hand, lets you specify a particular interface on which to translate
the addresses. Make sure that the real addresses for which you use identity NAT are routable on all
networks that are available according to your access lists.
For identity NAT, even though the mapped address is the same as the real address, you cannot initiate
a connection from the outside to the inside (even if the interface access list allows it). Use static
identity NAT or NAT exemption for this functionality.
•
Static identity NAT (static command)—Static identity NAT lets you specify the interface on which
you want to allow the real addresses to appear, so you can use identity NAT when you access
interface A, and use regular translation when you access interface B. Static identity NAT also lets
you use policy NAT, which identifies the real and destination addresses when determining the real
addresses to translate (see the “Policy NAT” section on page 17-9 for more information about policy
NAT). For example, you can use static identity NAT for an inside address when it accesses the
outside interface and the destination is server A, but use a normal translation when accessing the
outside server B.
•
NAT exemption (nat 0 access-list command)—NAT exemption allows both translated and remote
hosts to initiate connections. Like identity NAT, you do not limit translation for a host on specific
interfaces; you must use NAT exemption for connections through all interfaces. However,
NAT exemption does let you specify the real and destination addresses when determining the real
addresses to translate (similar to policy NAT), so you have greater control using NAT exemption.
However unlike policy NAT, NAT exemption does not consider the ports in the access list.
Policy NAT
Policy NAT lets you identify real addresses for address translation by specifying the source and
destination addresses in an extended access list. You can also optionally specify the source and
destination ports. Regular NAT can only consider the real addresses. For example, you can use translate
the real address to mapped address A when it accesses server A, but translate the real address to mapped
address B when it accesses server B.
Note
Policy NAT does not support time-based ACLs.
When you specify the ports in policy NAT for applications that require application inspection for
secondary channels (FTP, VoIP, etc.), the security appliance automatically translates the secondary ports.
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Note
All types of NAT support policy NAT except for NAT exemption. NAT exemption uses an access list to
identify the real addresses, but differs from policy NAT in that the ports are not considered. See the
“Bypassing NAT” section on page 17-28 for other differences. You can accomplish the same result as
NAT exemption using static identity NAT, which does support policy NAT.
Figure 17-8 shows a host on the 10.1.2.0/24 network accessing two different servers. When the host
accesses the server at 209.165.201.11, the real address is translated to 209.165.202.129. When the host
accesses the server at 209.165.200.225, the real address is translated to 209.165.202.130 so that the host
appears to be on the same network as the servers, which can help with routing.
Figure 17-8
Policy NAT with Different Destination Addresses
Server 1
209.165.201.11
Server 2
209.165.200.225
209.165.201.0/27
209.165.200.224/27
DMZ
Translation
10.1.2.27
209.165.202.129
Translation
10.1.2.27
209.165.202.130
Inside
Packet
Dest. Address:
209.165.201.11
10.1.2.27
Packet
Dest. Address:
209.165.200.225
130039
10.1.2.0/24
See the following commands for this example:
hostname(config)#
255.255.255.224
hostname(config)#
255.255.255.224
hostname(config)#
hostname(config)#
hostname(config)#
hostname(config)#
access-list NET1 permit ip 10.1.2.0 255.255.255.0 209.165.201.0
access-list NET2 permit ip 10.1.2.0 255.255.255.0 209.165.200.224
nat (inside) 1 access-list NET1
global (outside) 1 209.165.202.129
nat (inside) 2 access-list NET2
global (outside) 2 209.165.202.130
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Figure 17-9 shows the use of source and destination ports. The host on the 10.1.2.0/24 network accesses
a single host for both web services and Telnet services. When the host accesses the server for web
services, the real address is translated to 209.165.202.129. When the host accesses the same server for
Telnet services, the real address is translated to 209.165.202.130.
Figure 17-9
Policy NAT with Different Destination Ports
Web and Telnet server:
209.165.201.11
Internet
Translation
10.1.2.27:80
209.165.202.129
Translation
10.1.2.27:23
209.165.202.130
Inside
Web Packet
Dest. Address:
209.165.201.11:80
10.1.2.27
Telnet Packet
Dest. Address:
209.165.201.11:23
130040
10.1.2.0/24
See the following commands for this example:
hostname(config)# access-list WEB permit tcp 10.1.2.0 255.255.255.0 209.165.201.11
255.255.255.255 eq 80
hostname(config)# access-list TELNET permit tcp 10.1.2.0 255.255.255.0 209.165.201.11
255.255.255.255 eq 23
hostname(config)# nat (inside) 1 access-list WEB
hostname(config)# global (outside) 1 209.165.202.129
hostname(config)# nat (inside) 2 access-list TELNET
hostname(config)# global (outside) 2 209.165.202.130
For policy static NAT (and for NAT exemption, which also uses an access list to identify traffic), both
translated and remote hosts can originate traffic. For traffic originated on the translated network, the
NAT access list specifies the real addresses and the destination addresses, but for traffic originated on
the remote network, the access list identifies the real addresses and the source addresses of remote hosts
who are allowed to connect to the host using this translation.
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Figure 17-10 shows a remote host connecting to a translated host. The translated host has a policy static
NAT translation that translates the real address only for traffic to and from the 209.165.201.0/27
network. A translation does not exist for the 209.165.200.224/27 network, so the translated host cannot
connect to that network, nor can a host on that network connect to the translated host.
Figure 17-10
Policy Static NAT with Destination Address Translation
209.165.201.11
209.165.200.225
209.165.201.0/27
209.165.200.224/27
DMZ
No Translation
Undo Translation
10.1.2.27
209.165.202.129
Inside
10.1.2.27
130037
10.1.2.0/27
See the following commands for this example:
hostname(config)# access-list NET1 permit ip 10.1.2.0 255.255.255.224 209.165.201.0
255.255.255.224
hostname(config)# static (inside,outside) 209.165.202.129 access-list NET1
Note
Policy NAT does not support SQL*Net, but it is supported by regular NAT. See the “When to Use
Application Protocol Inspection” section on page 25-2 for information about NAT support for other
protocols.
NAT and Same Security Level Interfaces
NAT is not required between same security level interfaces even if you enable NAT control. You can
optionally configure NAT if desired. However, if you configure dynamic NAT when NAT control is
enabled, then NAT is required. See the “NAT Control” section on page 17-3 for more information. Also,
when you specify a group of IP address(es) for dynamic NAT or PAT on a same security interface, then
you must perform NAT on that group of addresses when they access any lower or same security level
interface (even when NAT control is not enabled). Traffic identified for static NAT is not affected.
See the “Allowing Communication Between Interfaces on the Same Security Level” section on page 7-6
to enable same security communication.
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Note
The security appliance does not support VoIP inspection engines when you configure NAT on same
security interfaces. These inspection engines include Skinny, SIP, and H.323. See the “When to Use
Application Protocol Inspection” section on page 25-2 for supported inspection engines.
Order of NAT Commands Used to Match Real Addresses
The security appliance matches real addresses to NAT commands in the following order:
1.
NAT exemption (nat 0 access-list)—In order, until the first match. Identity NAT is not included in
this category; it is included in the regular static NAT or regular NAT category. We do not recommend
overlapping addresses in NAT exemption statements because unexpected results can occur.
2.
Static NAT and Static PAT (regular and policy) (static)—In order, until the first match. Static
identity NAT is included in this category.
3.
Policy dynamic NAT (nat access-list)—In order, until the first match. Overlapping addresses are
allowed.
4.
Regular dynamic NAT (nat)—Best match. Regular identity NAT is included in this category. The
order of the NAT commands does not matter; the NAT statement that best matches the real address
is used. For example, you can create a general statement to translate all addresses (0.0.0.0) on an
interface. If you want to translate a subset of your network (10.1.1.1) to a different address, then you
can create a statement to translate only 10.1.1.1. When 10.1.1.1 makes a connection, the specific
statement for 10.1.1.1 is used because it matches the real address best. We do not recommend using
overlapping statements; they use more memory and can slow the performance of the security
appliance.
Mapped Address Guidelines
When you translate the real address to a mapped address, you can use the following mapped addresses:
•
Addresses on the same network as the mapped interface.
If you use addresses on the same network as the mapped interface (through which traffic exits the
security appliance), the security appliance uses proxy ARP to answer any requests for mapped
addresses, and thus intercepts traffic destined for a real address. This solution simplifies routing,
because the security appliance does not have to be the gateway for any additional networks.
However, this approach does put a limit on the number of available addresses used for translations.
For PAT, you can even use the IP address of the mapped interface.
•
Addresses on a unique network.
If you need more addresses than are available on the mapped interface network, you can identify
addresses on a different subnet. The security appliance uses proxy ARP to answer any requests for
mapped addresses, and thus intercepts traffic destined for a real address. If you use OSPF, and you
advertise routes on the mapped interface, then the security appliance advertises the mapped
addresses. If the mapped interface is passive (not advertising routes) or you are using static routing,
then you need to add a static route on the upstream router that sends traffic destined for the mapped
addresses to the security appliance.
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DNS and NAT
You might need to configure the security appliance to modify DNS replies by replacing the address in
the reply with an address that matches the NAT configuration. You can configure DNS modification
when you configure each translation.
For example, a DNS server is accessible from the outside interface. A server, ftp.cisco.com, is on the
inside interface. You configure the security appliance to statically translate the ftp.cisco.com real address
(10.1.3.14) to a mapped address (209.165.201.10) that is visible on the outside network (see
Figure 17-11). In this case, you want to enable DNS reply modification on this static statement so that
inside users who have access to ftp.cisco.com using the real address receive the real address from the
DNS server, and not the mapped address.
When an inside host sends a DNS request for the address of ftp.cisco.com, the DNS server replies with
the mapped address (209.165.201.10). The security appliance refers to the static statement for the inside
server and translates the address inside the DNS reply to 10.1.3.14. If you do not enable DNS reply
modification, then the inside host attempts to send traffic to 209.165.201.10 instead of accessing
ftp.cisco.com directly.
Figure 17-11
DNS Reply Modification
DNS Server
1
DNS Query
ftp.cisco.com?
2
Outside
DNS Reply
209.165.201.10
Security
Appliance
3
DNS Reply Modification
209.165.201.10
10.1.3.14
Inside
4
DNS Reply
10.1.3.14
ftp.cisco.com
10.1.3.14
Static Translation
on Outside to:
209.165.201.10
130021
User
5
FTP Request
10.1.3.14
See the following command for this example:
hostname(config)# static (inside,outside) 209.165.201.10 10.1.3.14 netmask 255.255.255.255
dns
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Configuring NAT Control
Note
If a user on a different network (for example, DMZ) also requests the IP address for ftp.cisco.com from
the outside DNS server, then the IP address in the DNS reply is also modified for this user, even though
the user is not on the Inside interface referenced by the static command.
Figure 17-12 shows a web server and DNS server on the outside. The security appliance has a static
translation for the outside server. In this case, when an inside user requests the address for ftp.cisco.com
from the DNS server, the DNS server responds with the real address, 209.165.20.10. Because you want
inside users to use the mapped address for ftp.cisco.com (10.1.2.56) you need to configure DNS reply
modification for the static translation.
Figure 17-12
DNS Reply Modification Using Outside NAT
ftp.cisco.com
209.165.201.10
Static Translation on Inside to:
10.1.2.56
DNS Server
7
FTP Request
209.165.201.10
1
DNS Query
ftp.cisco.com?
2
DNS Reply
209.165.201.10
3
Outside
6
Dest Addr. Translation
10.1.2.56
209.165.201.10
Security
Appliance
5
DNS Reply Modification
209.165.201.10
10.1.2.56
Inside
4
FTP Request
10.1.2.56
User
10.1.2.27
130022
DNS Reply
10.1.2.56
See the following command for this example:
hostname(config)# static (outside,inside) 10.1.2.56 209.165.201.10 netmask 255.255.255.255
dns
Configuring NAT Control
NAT control requires that packets traversing from an inside interface to an outside interface match a NAT
rule. See the “NAT Control” section on page 17-3 for more information.
To enable NAT control, enter the following command:
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Using Dynamic NAT and PAT
hostname(config)# nat-control
To disable NAT control, enter the no form of the command.
Using Dynamic NAT and PAT
This section describes how to configure dynamic NAT and PAT, and includes the following topics:
•
Dynamic NAT and PAT Implementation, page 17-16
•
Configuring Dynamic NAT or PAT, page 17-22
Dynamic NAT and PAT Implementation
For dynamic NAT and PAT, you first configure a nat command identifying the real addresses on a given
interface that you want to translate. Then you configure a separate global command to specify the
mapped addresses when exiting another interface (in the case of PAT, this is one address). Each nat
command matches a global command by comparing the NAT ID, a number that you assign to each
command (see Figure 17-13).
Figure 17-13
nat and global ID Matching
Web Server:
www.cisco.com
Outside
Global 1: 209.165.201.3209.165.201.10
Translation
10.1.2.27
209.165.201.3
NAT 1: 10.1.2.0/24
10.1.2.27
130027
Inside
See the following commands for this example:
hostname(config)# nat (inside) 1 10.1.2.0 255.255.255.0
hostname(config)# global (outside) 1 209.165.201.3-209.165.201.10
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You can enter a nat command for each interface using the same NAT ID; they all use the same global
command when traffic exits a given interface. For example, you can configure nat commands for Inside
and DMZ interfaces, both on NAT ID 1. Then you configure a global command on the Outside interface
that is also on ID 1. Traffic from the Inside interface and the DMZ interface share a mapped pool or a
PAT address when exiting the Outside interface (see Figure 17-14).
Figure 17-14
nat Commands on Multiple Interfaces
Web Server:
www.cisco.com
Translation
10.1.1.15
209.165.201.4
Outside
Global 1: 209.165.201.3209.165.201.10
NAT 1: 10.1.1.0/24
DMZ
Translation
10.1.2.27
209.165.201.3
10.1.1.15
NAT 1: 10.1.2.0/24
130028
Inside
10.1.2.27
See the following commands for this example:
hostname(config)# nat (inside) 1 10.1.2.0 255.255.255.0
hostname(config)# nat (dmz) 1 10.1.1.0 255.255.255.0
hostname(config)# global (outside) 1 209.165.201.3-209.165.201.10
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Using Dynamic NAT and PAT
You can also enter a global command for each interface using the same NAT ID. If you enter a global
command for the Outside and DMZ interfaces on ID 1, then the Inside nat command identifies traffic to
be translated when going to both the Outside and the DMZ interfaces. Similarly, if you also enter a nat
command for the DMZ interface on ID 1, then the global command on the Outside interface is also used
for DMZ traffic. (See Figure 17-15).
Figure 17-15
global and nat Commands on Multiple Interfaces
Web Server:
www.cisco.com
Translation
10.1.1.15
209.165.201.4
Outside
Global 1: 209.165.201.3209.165.201.10
Security
Appliance
NAT 1: 10.1.1.0/24
Global 1: 10.1.1.23
Translation
10.1.2.27
209.165.201.3
DMZ
10.1.1.15
NAT 1: 10.1.2.0/24
Translation
10.1.2.27
10.1.1.23:2024
10.1.2.27
130024
Inside
See the following commands for this example:
hostname(config)#
hostname(config)#
hostname(config)#
hostname(config)#
nat (inside) 1 10.1.2.0 255.255.255.0
nat (dmz) 1 10.1.1.0 255.255.255.0
global (outside) 1 209.165.201.3-209.165.201.10
global (dmz) 1 10.1.1.23
If you use different NAT IDs, you can identify different sets of real addresses to have different mapped
addresses. For example, on the Inside interface, you can have two nat commands on two different
NAT IDs. On the Outside interface, you configure two global commands for these two IDs. Then, when
traffic from Inside network A exits the Outside interface, the IP addresses are translated to pool A
addresses; while traffic from Inside network B are translated to pool B addresses (see Figure 17-16). If
you use policy NAT, you can specify the same real addresses for multiple nat commands, as long as the
the destination addresses and ports are unique in each access list.
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Using Dynamic NAT and PAT
Figure 17-16
Different NAT IDs
Web Server:
www.cisco.com
Outside
Global 1: 209.165.201.3209.165.201.10
Global 2: 209.165.201.11
Security
Appliance
192.168.1.14
Translation
209.165.201.11:4567
NAT 1: 10.1.2.0/24
Translation
10.1.2.27
209.165.201.3
NAT 2: 192.168.1.0/24
Inside
130025
10.1.2.27
192.168.1.14
See the following commands for this example:
hostname(config)#
hostname(config)#
hostname(config)#
hostname(config)#
nat (inside) 1 10.1.2.0 255.255.255.0
nat (inside) 2 192.168.1.0 255.255.255.0
global (outside) 1 209.165.201.3-209.165.201.10
global (outside) 2 209.165.201.11
You can enter multiple global commands for one interface using the same NAT ID; the security
appliance uses the dynamic NAT global commands first, in the order they are in the configuration, and
then uses the PAT global commands in order. You might want to enter both a dynamic NAT global
command and a PAT global command if you need to use dynamic NAT for a particular application, but
want to have a backup PAT statement in case all the dynamic NAT addresses are depleted. Similarly, you
might enter two PAT statements if you need more than the approximately 64,000 PAT sessions that a
single PAT mapped statement supports (see Figure 17-17).
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Using Dynamic NAT and PAT
Figure 17-17
NAT and PAT Together
Web Server:
www.cisco.com
Translation
10.1.2.27
209.165.201.3
Outside
Global 1: 209.165.201.3209.165.201.4
Global 1: 209.165.201.5
10.1.2.29
Translation
209.165.201.5:6096
Translation
10.1.2.28
209.165.201.4
NAT 1: 10.1.2.0/24
Inside
10.1.2.29
130026
10.1.2.27
10.1.2.28
See the following commands for this example:
hostname(config)# nat (inside) 1 10.1.2.0 255.255.255.0
hostname(config)# global (outside) 1 209.165.201.3-209.165.201.4
hostname(config)# global (outside) 1 209.165.201.5
For outside NAT, you need to identify the nat command for outside NAT (the outside keyword). If you
also want to translate the same traffic when it accesses an inside interface (for example, traffic on a DMZ
is translated when accessing the Inside and the Outside interfaces), then you must configure a separate
nat command without the outside option. In this case, you can identify the same addresses in both
statements and use the same NAT ID (see Figure 17-18). Note that for outside NAT (DMZ interface to
Inside interface), the inside host uses a static command to allow outside access, so both the source and
destination addresses are translated.
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Figure 17-18
Outside NAT and Inside NAT Combined
Outside
Translation
10.1.1.15
209.165.201.4
Global 1: 209.165.201.3209.165.201.10
Outside NAT 1: 10.1.1.0/24
NAT 1: 10.1.1.0/24
DMZ
10.1.1.15
Global 1: 10.1.2.3010.1.2.40 Static to DMZ: 10.1.2.27
10.1.1.5
Translation
10.1.1.15
10.1.2.30
Inside
130038
Undo Translation
10.1.1.5
10.1.2.27
10.1.2.27
See the following commands for this example:
hostname(config)#
hostname(config)#
hostname(config)#
hostname(config)#
hostname(config)#
nat (dmz) 1 10.1.1.0 255.255.255.0 outside
nat (dmz) 1 10.1.1.0 255.255.255.0
static (inside,dmz) 10.1.1.5 10.1.2.27 netmask 255.255.255.255
global (outside) 1 209.165.201.3-209.165.201.4
global (inside) 1 10.1.2.30-1-10.1.2.40
When you specify a group of IP address(es) in a nat command, then you must perform NAT on that group
of addresses when they access any lower or same security level interface; you must apply a global
command with the same NAT ID on each interface, or use a static command. NAT is not required for
that group when it accesses a higher security interface, because to perform NAT from outside to inside,
you must create a separate nat command using the outside keyword. If you do apply outside NAT, then
the NAT requirements preceding come into effect for that group of addresses when they access all higher
security interfaces. Traffic identified by a static command is not affected.
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Using Dynamic NAT and PAT
Configuring Dynamic NAT or PAT
This section describes how to configure dynamic NAT or dynamic PAT. The configuration for dynamic
NAT and PAT are almost identical; for NAT you specify a range of mapped addresses, and for PAT you
specify a single address.
Figure 17-19 shows a typical dynamic NAT scenario. Only translated hosts can create a NAT session,
and responding traffic is allowed back. The mapped address is dynamically assigned from a pool defined
by the global command.
Figure 17-19
Dynamic NAT
Security
Appliance
209.165.201.1
10.1.1.2
209.165.201.2
130032
10.1.1.1
Inside Outside
Figure 17-20 shows a typical dynamic PAT scenario. Only translated hosts can create a NAT session, and
responding traffic is allowed back. The mapped address defined by the global command is the same for
each translation, but the port is dynamically assigned.
Dynamic PAT
Security
Appliance
10.1.1.1:1025
209.165.201.1:2020
10.1.1.1:1026
209.165.201.1:2021
10.1.1.2:1025
209.165.201.1:2022
Inside Outside
130034
Figure 17-20
For more information about dynamic NAT, see the “Dynamic NAT” section on page 17-5. For more
information about PAT, see the “PAT” section on page 17-7.
Note
If you change the NAT configuration, and you do not want to wait for existing translations to time out
before the new NAT information is used, you can clear the translation table using the clear xlate
command. However, clearing the translation table disconnects all current connections that use
translations.
To configure dynamic NAT or PAT, perform the following steps:
Step 1
To identify the real addresses that you want to translate, enter one of the following commands:
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•
Policy NAT:
hostname(config)# nat (real_interface) nat_id access-list acl_name [dns] [outside]
[norandomseq] [[tcp] tcp_max_conns [emb_limit]] [udp udp_max_conns]
You can identify overlapping addresses in other nat commands. For example, you can identify
10.1.1.0 in one command, but 10.1.1.1 in another. The traffic is matched to a policy NAT command
in order, until the first match, or for regular NAT, using the best match.
See the following description about options for this command:
– access-list acl_name—Identify the real addresses and destination addresses using an extended
access list. Create the access list using the access-list command (see the “Adding an Extended
Access List” section on page 16-5). This access list should include only permit ACEs. You can
optionally specify the real and destination ports in the access list using the eq operator. Policy
NAT does not consider the inactive or time-range keywords; all ACEs are considered to be
active for policy NAT configuration.
– nat_id—An integer between 1 and 65535. The NAT ID should match a global command NAT
ID. See the “Dynamic NAT and PAT Implementation” section on page 17-16 for more
information about how NAT IDs are used. 0 is reserved for NAT exemption. (See the
“Configuring NAT Exemption” section on page 17-31 for more information about NAT
exemption.)
– dns—If your nat command includes the address of a host that has an entry in a DNS server, and
the DNS server is on a different interface from a client, then the client and the DNS server need
different addresses for the host; one needs the mapped address and one needs the real address.
This option rewrites the address in the DNS reply to the client. The translated host needs to be
on the same interface as either the client or the DNS server. Typically, hosts that need to allow
access from other interfaces use a static translation, so this option is more likely to be used with
the static command. (See the “DNS and NAT” section on page 17-14 for more information.)
– outside—If this interface is on a lower security level than the interface you identify by the
matching global statement, then you must enter outside to identify the NAT instance as
outside NAT.
– norandomseq, tcp tcp_max_conns, udp udp_max_conns, and emb_limit—These keywords set
connection limits. However, we recommend using a more versatile method for setting
connection limits; see the “Configuring Connection Limits and Timeouts” section on page 23-6.
•
Regular NAT:
hostname(config)# nat (real_interface) nat_id real_ip [mask [dns] [outside]
[norandomseq] [[tcp] tcp_max_conns [emb_limit]] [udp udp_max_conns]]
The nat_id is an integer between 1 and 2147483647. The NAT ID must match a global command
NAT ID. See the “Dynamic NAT and PAT Implementation” section on page 17-16 for more
information about how NAT IDs are used. 0 is reserved for identity NAT. See the “Configuring
Identity NAT” section on page 17-29 for more information about identity NAT.
See the preceding policy NAT command for information about other options.
Step 2
To identify the mapped address(es) to which you want to translate the real addresses when they exit a
particular interface, enter the following command:
hostname(config)# global (mapped_interface) nat_id {mapped_ip[-mapped_ip] | interface}
This NAT ID should match a nat command NAT ID. The matching nat command identifies the addresses
that you want to translate when they exit this interface.
You can specify a single address (for PAT) or a range of addresses (for NAT). The range can go across
subnet boundaries if desired. For example, you can specify the following “supernet”:
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192.168.1.1-192.168.2.254
For example, to translate the 10.1.1.0/24 network on the inside interface, enter the following command:
hostname(config)# nat (inside) 1 10.1.1.0 255.255.255.0
hostname(config)# global (outside) 1 209.165.201.1-209.165.201.30
To identify a pool of addresses for dynamic NAT as well as a PAT address for when the NAT pool is
exhausted, enter the following commands:
hostname(config)# nat (inside) 1 10.1.1.0 255.255.255.0
hostname(config)# global (outside) 1 209.165.201.5
hostname(config)# global (outside) 1 209.165.201.10-209.165.201.20
To translate the lower security dmz network addresses so they appear to be on the same network as the
inside network (10.1.1.0), for example, to simplify routing, enter the following commands:
hostname(config)# nat (dmz) 1 10.1.2.0 255.255.255.0 outside dns
hostname(config)# global (inside) 1 10.1.1.45
To identify a single real address with two different destination addresses using policy NAT, enter the
following commands (see Figure 17-8 on page 17-10 for a related figure):
hostname(config)#
255.255.255.224
hostname(config)#
255.255.255.224
hostname(config)#
hostname(config)#
hostname(config)#
hostname(config)#
access-list NET1 permit ip 10.1.2.0 255.255.255.0 209.165.201.0
access-list NET2 permit ip 10.1.2.0 255.255.255.0 209.165.200.224
nat (inside) 1 access-list NET1 tcp 0 2000 udp 10000
global (outside) 1 209.165.202.129
nat (inside) 2 access-list NET2 tcp 1000 500 udp 2000
global (outside) 2 209.165.202.130
To identify a single real address/destination address pair that use different ports using policy NAT, enter
the following commands (see Figure 17-9 on page 17-11 for a related figure):
hostname(config)# access-list WEB permit tcp 10.1.2.0 255.255.255.0 209.165.201.11
255.255.255.255 eq 80
hostname(config)# access-list TELNET permit tcp 10.1.2.0 255.255.255.0 209.165.201.11
255.255.255.255 eq 23
hostname(config)# nat (inside) 1 access-list WEB
hostname(config)# global (outside) 1 209.165.202.129
hostname(config)# nat (inside) 2 access-list TELNET
hostname(config)# global (outside) 2 209.165.202.130
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Applying NAT
Using Static NAT
Using Static NAT
This section describes how to configure a static translation.
Figure 17-21 shows a typical static NAT scenario. The translation is always active so both translated and
remote hosts can originate connections, and the mapped address is statically assigned by the static
command.
Figure 17-21
Static NAT
10.1.1.1
209.165.201.1
10.1.1.2
209.165.201.2
Inside Outside
130035
Security
Appliance
You cannot use the same real or mapped address in multiple static commands between the same two
interfaces. Do not use a mapped address in the static command that is also defined in a global command
for the same mapped interface.
For more information about static NAT, see the “Static NAT” section on page 17-7.
Note
If you remove a static command, existing connections that use the translation are not affected. To remove
these connections, enter the clear local-host command.
You cannot clear static translations from the translation table with the clear xlate command; you must
remove the static command instead. Only dynamic translations created by the nat and global commands
can be removed with the clear xlate command.
To configure static NAT, enter one of the following commands.
•
For policy static NAT, enter the following command:
hostname(config)# static (real_interface,mapped_interface) {mapped_ip | interface}
access-list acl_name [dns] [norandomseq] [[tcp] tcp_max_conns [emb_limit]]
[udp udp_max_conns]
Create the access list using the access-list command (see the “Adding an Extended Access List”
section on page 16-5). This access list should include only permit ACEs. The source subnet mask
used in the access list is also used for the mapped addresses. You can also specify the real and
destination ports in the access list using the eq operator. Policy NAT does not consider the inactive
or time-range keywords; all ACEs are considered to be active for policy NAT configuration. See the
“Policy NAT” section on page 17-9 for more information.
If you specify a network for translation (for example, 10.1.1.0 255.255.255.0), then the security
appliance translates the .0 and .255 addresses. If you want to prevent access to these addresses, be
sure to configure an access list to deny access.
See the “Configuring Dynamic NAT or PAT” section on page 17-22 for information about the other
options.
•
To configure regular static NAT, enter the following command:
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hostname(config)# static (real_interface,mapped_interface) {mapped_ip | interface}
real_ip [netmask mask] [dns] [norandomseq] [[tcp] tcp_max_conns [emb_limit]]
[udp udp_max_conns]
See the “Configuring Dynamic NAT or PAT” section on page 17-22 for information about the
options.
For example, the following policy static NAT example shows a single real address that is translated to
two mapped addresses depending on the destination address (see Figure 17-8 on page 17-10 for a related
figure):
hostname(config)#
hostname(config)#
255.255.255.224
hostname(config)#
hostname(config)#
access-list NET1 permit ip host 10.1.2.27 209.165.201.0 255.255.255.224
access-list NET2 permit ip host 10.1.2.27 209.165.200.224
static (inside,outside) 209.165.202.129 access-list NET1
static (inside,outside) 209.165.202.130 access-list NET2
The following command maps an inside IP address (10.1.1.3) to an outside IP address (209.165.201.12):
hostname(config)# static (inside,outside) 209.165.201.12 10.1.1.3 netmask 255.255.255.255
The following command maps the outside address (209.165.201.15) to an inside address (10.1.1.6):
hostname(config)# static (outside,inside) 10.1.1.6 209.165.201.15 netmask 255.255.255.255
The following command statically maps an entire subnet:
hostname(config)# static (inside,dmz) 10.1.1.0 10.1.2.0 netmask 255.255.255.0
Using Static PAT
This section describes how to configure a static port translation. Static PAT lets you translate the real IP
address to a mapped IP address, as well as the real port to a mapped port. You can choose to translate
the real port to the same port, which lets you translate only specific types of traffic, or you can take it
further by translating to a different port.
Figure 17-22 shows a typical static PAT scenario. The translation is always active so both translated and
remote hosts can originate connections, and the mapped address and port is statically assigned by the
static command.
Figure 17-22
Static PAT
10.1.1.1:23
209.165.201.1:23
10.1.1.2:8080
209.165.201.2:80
Inside Outside
130044
Security
Appliance
For applications that require application inspection for secondary channels (FTP, VoIP, etc.), the security
appliance automatically translates the secondary ports.
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You cannot use the same real or mapped address in multiple static statements between the same two
interfaces. Do not use a mapped address in the static command that is also defined in a global command
for the same mapped interface.
For more information about static PAT, see the “Static PAT” section on page 17-8.
Note
If you remove a static command, existing connections that use the translation are not affected. To remove
these connections, enter the clear local-host command.
You cannot clear static translations from the translation table with the clear xlate command; you must
remove the static command instead. Only dynamic translations created by the nat and global commands
can be removed with the clear xlate command.
To configure static PAT, enter one of the following commands.
•
For policy static PAT, enter the following command:
hostname(config)# static (real_interface,mapped_interface) {tcp | udp}
{mapped_ip | interface} mapped_port access-list acl_name [dns] [norandomseq]
[[tcp] tcp_max_conns [emb_limit]] [udp udp_max_conns]
Create the access list using the access-list command (see the “Adding an Extended Access List”
section on page 16-5). The protocol in the access list must match the protocol you set in this
command. For example, if you specify tcp in the static command, then you must specify tcp in the
access list. Specify the port using the eq operator. This access list should include only permit ACEs.
The source subnet mask used in the access list is also used for the mapped addresses. Policy NAT
does not consider the inactive or time-range keywords; all ACEs are considered to be active for
policy NAT configuration.
If you specify a network for translation (for example, 10.1.1.0 255.255.255.0), then the security
appliance translates the .0 and .255 addresses. If you want to prevent access to these addresses, be
sure to configure an access list to deny access.
See the “Configuring Dynamic NAT or PAT” section on page 17-22 for information about the other
options.
•
To configure regular static PAT, enter the following command:
hostname(config)# static (real_interface,mapped_interface) {tcp | udp} {mapped_ip |
interface} mapped_port real_ip real_port [netmask mask] [dns] [norandomseq] [[tcp]
tcp_max_conns [emb_limit]] [udp udp_max_conns]
See the “Configuring Dynamic NAT or PAT” section on page 17-22 for information about the
options.
Note
When configuring static PAT with FTP, you need to add entries for both TCP ports 20 and 21. You must
specify port 20 so that the source port for the active transfer is not modified to another port, which may
interfere with other devices that perform NAT on FTP traffic.
For example, for Telnet traffic initiated from hosts on the 10.1.3.0 network to the security appliance
outside interface (10.1.2.14), you can redirect the traffic to the inside host at 10.1.1.15 by entering the
following commands:
hostname(config)# access-list TELNET permit tcp host 10.1.1.15 eq telnet 10.1.3.0
255.255.255.0 eq telnet
hostname(config)# static (inside,outside) tcp 10.1.2.14 telnet access-list TELNET
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For HTTP traffic initiated from hosts on the 10.1.3.0 network to the security appliance outside interface
(10.1.2.14), you can redirect the traffic to the inside host at 10.1.1.15 by entering:
hostname(config)# access-list HTTP permit tcp host 10.1.1.15 eq http 10.1.3.0
255.255.255.0 eq http
hostname(config)# static (inside,outside) tcp 10.1.2.14 http access-list HTTP
To redirect Telnet traffic from the security appliance outside interface (10.1.2.14) to the inside host at
10.1.1.15, enter the following command:
hostname(config)# static (inside,outside) tcp 10.1.2.14 telnet 10.1.1.15 telnet netmask
255.255.255.255
If you want to allow the preceding real Telnet server to initiate connections, though, then you need to
provide additional translation. For example, to translate all other types of traffic, enter the following
commands. The original static command provides translation for Telnet to the server, while the nat and
global commands provide PAT for outbound connections from the server.
hostname(config)# static (inside,outside) tcp 10.1.2.14 telnet 10.1.1.15 telnet netmask
255.255.255.255
hostname(config)# nat (inside) 1 10.1.1.15 255.255.255.255
hostname(config)# global (outside) 1 10.1.2.14
If you also have a separate translation for all inside traffic, and the inside hosts use a different mapped
address from the Telnet server, you can still configure traffic initiated from the Telnet server to use the
same mapped address as the static statement that allows Telnet traffic to the server. You need to create
a more exclusive nat statement just for the Telnet server. Because nat statements are read for the best
match, more exclusive nat statements are matched before general statements. The following example
shows the Telnet static statement, the more exclusive nat statement for initiated traffic from the Telnet
server, and the statement for other inside hosts, which uses a different mapped address.
hostname(config)#
255.255.255.255
hostname(config)#
hostname(config)#
hostname(config)#
hostname(config)#
static (inside,outside) tcp 10.1.2.14 telnet 10.1.1.15 telnet netmask
nat (inside) 1 10.1.1.15 255.255.255.255
global (outside) 1 10.1.2.14
nat (inside) 2 10.1.1.0 255.255.255.0
global (outside) 2 10.1.2.78
To translate a well-known port (80) to another port (8080), enter the following command:
hostname(config)# static (inside,outside) tcp 10.1.2.45 80 10.1.1.16 8080 netmask
255.255.255.255
Bypassing NAT
This section describes how to bypass NAT. You might want to bypass NAT when you enable NAT control.
You can bypass NAT using identity NAT, static identity NAT, or NAT exemption. See the “Bypassing
NAT When NAT Control is Enabled” section on page 17-9 for more information about these methods.
This section includes the following topics:
•
Configuring Identity NAT, page 17-29
•
Configuring Static Identity NAT, page 17-29
•
Configuring NAT Exemption, page 17-31
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Configuring Identity NAT
Identity NAT translates the real IP address to the same IP address. Only “translated” hosts can create
NAT translations, and responding traffic is allowed back.
Figure 17-23 shows a typical identity NAT scenario.
Figure 17-23
Identity NAT
Security
Appliance
209.165.201.1
209.165.201.2
209.165.201.2
Inside Outside
Note
130033
209.165.201.1
If you change the NAT configuration, and you do not want to wait for existing translations to time out
before the new NAT information is used, you can clear the translation table using the clear xlate
command. However, clearing the translation table disconnects all current connections that use
translations.
To configure identity NAT, enter the following command:
hostname(config)# nat (real_interface) 0 real_ip [mask [dns] [outside] [norandomseq]
[[tcp] tcp_max_conns [emb_limit]] [udp udp_max_conns]
See the “Configuring Dynamic NAT or PAT” section on page 17-22 for information about the options.
For example, to use identity NAT for the inside 10.1.1.0/24 network, enter the following command:
hostname(config)# nat (inside) 0 10.1.1.0 255.255.255.0
Configuring Static Identity NAT
Static identity NAT translates the real IP address to the same IP address. The translation is always active,
and both “translated” and remote hosts can originate connections. Static identity NAT lets you use
regular NAT or policy NAT. Policy NAT lets you identify the real and destination addresses when
determining the real addresses to translate (see the “Policy NAT” section on page 17-9 for more
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information about policy NAT). For example, you can use policy static identity NAT for an inside address
when it accesses the outside interface and the destination is server A, but use a normal translation when
accessing the outside server B.
Figure 17-24 shows a typical static identity NAT scenario.
Figure 17-24
Static Identity NAT
209.165.201.1
209.165.201.1
209.165.201.2
209.165.201.2
Inside Outside
Note
130036
Security
Appliance
If you remove a static command, existing connections that use the translation are not affected. To remove
these connections, enter the clear local-host command.
You cannot clear static translations from the translation table with the clear xlate command; you must
remove the static command instead. Only dynamic translations created by the nat and global commands
can be removed with the clear xlate command.
To configure static identity NAT, enter one of the following commands:
•
To configure policy static identity NAT, enter the following command:
hostname(config)# static (real_interface,mapped_interface) real_ip access-list acl_id
[dns] [norandomseq] [[tcp] tcp_max_conns [emb_limit]] [udp udp_max_conns]
Create the access list using the access-list command (see the “Adding an Extended Access List”
section on page 16-5). This access list should include only permit ACEs. Make sure the source
address in the access list matches the real_ip in this command. Policy NAT does not consider the
inactive or time-range keywords; all ACEs are considered to be active for policy NAT
configuration. See the “Policy NAT” section on page 17-9 for more information.
See the “Configuring Dynamic NAT or PAT” section on page 17-22 for information about the other
options.
•
To configure regular static identity NAT, enter the following command:
hostname(config)# static (real_interface,mapped_interface) real_ip real_ip [netmask
mask] [dns] [norandomseq] [[tcp] tcp_max_conns [emb_limit]] [udp udp_max_conns]
Specify the same IP address for both real_ip arguments.
See the “Configuring Dynamic NAT or PAT” section on page 17-22 for information about the other
options.
For example, the following command uses static identity NAT for an inside IP address (10.1.1.3) when
accessed by the outside:
hostname(config)# static (inside,outside) 10.1.1.3 10.1.1.3 netmask 255.255.255.255
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The following command uses static identity NAT for an outside address (209.165.201.15) when accessed
by the inside:
hostname(config)# static (outside,inside) 209.165.201.15 209.165.201.15 netmask
255.255.255.255
The following command statically maps an entire subnet:
hostname(config)# static (inside,dmz) 10.1.2.0 10.1.2.0 netmask 255.255.255.0
The following static identity policy NAT example shows a single real address that uses identity NAT
when accessing one destination address, and a translation when accessing another:
hostname(config)#
hostname(config)#
255.255.255.224
hostname(config)#
hostname(config)#
access-list NET1 permit ip host 10.1.2.27 209.165.201.0 255.255.255.224
access-list NET2 permit ip host 10.1.2.27 209.165.200.224
static (inside,outside) 10.1.2.27 access-list NET1
static (inside,outside) 209.165.202.130 access-list NET2
Configuring NAT Exemption
NAT exemption exempts addresses from translation and allows both real and remote hosts to originate
connections. NAT exemption lets you specify the real and destination addresses when determining the
real traffic to exempt (similar to policy NAT), so you have greater control using NAT exemption than
identity NAT. However unlike policy NAT, NAT exemption does not consider the ports in the access list.
Use static identity NAT to consider ports in the access list.
Figure 17-25 shows a typical NAT exemption scenario.
Figure 17-25
NAT Exemption
Security
Appliance
209.165.201.1
209.165.201.2
209.165.201.2
Inside Outside
Note
130036
209.165.201.1
If you remove a NAT exemption configuration, existing connections that use NAT exemption are not
affected. To remove these connections, enter the clear local-host command.
To configure NAT exemption, enter the following command:
hostname(config)# nat (real_interface) 0 access-list acl_name [outside] [norandomseq]
[[tcp] tcp_max_conns [emb_limit]] [udp udp_max_conns]
Create the access list using the access-list command (see the “Adding an Extended Access List” section
on page 16-5). This access list can include both permit ACEs and deny ACEs. Do not specify the real
and destination ports in the access list; NAT exemption does not consider the ports. NAT exemption also
does not consider the inactive or time-range keywords; all ACEs are considered to be active for
NAT exemption configuration.
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See the “Configuring Dynamic NAT or PAT” section on page 17-22 for information about the other
options.
By default, this command exempts traffic from inside to outside. If you want traffic from outside to
inside to bypass NAT, then add an additional nat command and enter outside to identify the NAT
instance as outside NAT. You might want to use outside NAT exemption if you configure dynamic NAT
for the outside interface and want to exempt other traffic.
For example, to exempt an inside network when accessing any destination address, enter the following
command:
hostname(config)# access-list EXEMPT permit ip 10.1.2.0 255.255.255.0 any
hostname(config)# nat (inside) 0 access-list EXEMPT
To use dynamic outside NAT for a DMZ network, and exempt another DMZ network, enter the following
command:
hostname(config)#
hostname(config)#
hostname(config)#
hostname(config)#
nat (dmz) 1 10.1.2.0 255.255.255.0 outside dns
global (inside) 1 10.1.1.45
access-list EXEMPT permit ip 10.1.3.0 255.255.255.0 any
nat (dmz) 0 access-list EXEMPT
To exempt an inside address when accessing two different destination addresses, enter the following
commands:
hostname(config)# access-list NET1 permit ip 10.1.2.0 255.255.255.0 209.165.201.0
255.255.255.224
hostname(config)# access-list NET1 permit ip 10.1.2.0 255.255.255.0 209.165.200.224
255.255.255.224
hostname(config)# nat (inside) 0 access-list NET1
NAT Examples
This section describes typical scenarios that use NAT solutions, and includes the following topics:
•
Overlapping Networks, page 17-33
•
Redirecting Ports, page 17-34
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Overlapping Networks
In Figure 17-26, the security appliance connects two private networks with overlapping address ranges.
Figure 17-26
Using Outside NAT with Overlapping Networks
192.168.100.2
192.168.100.2
outside
inside
192.168.100.0/24
192.168.100.3
dmz
192.168.100.0/24
10.1.1.1
192.168.100.3
130029
192.168.100.1
10.1.1.2
Two networks use an overlapping address space (192.168.100.0/24), but hosts on each network must
communicate (as allowed by access lists). Without NAT, when a host on the inside network tries to access
a host on the overlapping DMZ network, the packet never makes it past the security appliance, which
sees the packet as having a destination address on the inside network. Moreover, if the destination
address is being used by another host on the inside network, that host receives the packet.
To solve this problem, use NAT to provide non-overlapping addresses. If you want to allow access in
both directions, use static NAT for both networks. If you only want to allow the inside interface to access
hosts on the DMZ, then you can use dynamic NAT for the inside addresses, and static NAT for the DMZ
addresses you want to access. This example shows static NAT.
To configure static NAT for these two interfaces, perform the following steps. The 10.1.1.0/24 network
on the DMZ is not translated.
Step 1
Translate 192.168.100.0/24 on the inside to 10.1.2.0 /24 when it accesses the DMZ by entering the
following command:
hostname(config)# static (inside,dmz) 10.1.2.0 192.168.100.0 netmask 255.255.255.0
Step 2
Translate the 192.168.100.0/24 network on the DMZ to 10.1.3.0/24 when it accesses the inside by
entering the following command:
hostname(config)# static (dmz,inside) 10.1.3.0 192.168.100.0 netmask 255.255.255.0
Step 3
Configure the following static routes so that traffic to the dmz network can be routed correctly by the
security appliance:
hostname(config)# route dmz 192.168.100.128 255.255.255.128 10.1.1.2 1
hostname(config)# route dmz 192.168.100.0 255.255.255.128 10.1.1.2 1
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The security appliance already has a connected route for the inside network. These static routes allow
the security appliance to send traffic for the 192.168.100.0/24 network out the DMZ interface to the
gateway router at 10.1.1.2. (You need to split the network into two because you cannot create a static
route with the exact same network as a connected route.) Alternatively, you could use a more broad route
for the DMZ traffic, such as a default route.
If host 192.168.100.2 on the DMZ network wants to initiate a connection to host 192.168.100.2 on the
inside network, the following events occur:
1.
The DMZ host 192.168.100.2 sends the packet to IP address 10.1.2.2.
2.
When the security appliance receives this packet, the security appliance translates the source address
from 192.168.100.2 to 10.1.3.2.
3.
Then the security appliance translates the destination address from 10.1.2.2 to 192.168.100.2, and
the packet is forwarded.
Redirecting Ports
Figure 17-27 illustrates a typical network scenario in which the port redirection feature might be useful.
Figure 17-27
Port Redirection Using Static PAT
Telnet Server
10.1.1.6
FTP Server
10.1.1.3
Web Server
10.1.1.5
10.1.1.1
209.165.201.25
Inside
Outside
130030
Web Server
10.1.1.7
In the configuration described in this section, port redirection occurs for hosts on external networks as
follows:
•
Telnet requests to IP address 209.165.201.5 are redirected to 10.1.1.6.
•
FTP requests to IP address 209.165.201.5 are redirected to 10.1.1.3.
•
HTTP request to security appliance outside IP address 209.165.201.25 are redirected to 10.1.1.5.
•
HTTP port 8080 requests to PAT address 209.165.201.15 are redirected to 10.1.1.7 port 80.
To implement this scenario, perform the following steps:
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Step 1
Configure PAT for the inside network by entering the following commands:
hostname(config)# nat (inside) 1 0.0.0.0 0.0.0.0 0 0
hostname(config)# global (outside) 1 209.165.201.15
Step 2
Redirect Telnet requests for 209.165.201.5 to 10.1.1.6 by entering the following command:
hostname(config)# static (inside,outside) tcp 209.165.201.5 telnet 10.1.1.6 telnet netmask
255.255.255.255
Step 3
Redirect FTP requests for IP address 209.165.201.5 to 10.1.1.3 by entering the following command:
hostname(config)# static (inside,outside) tcp 209.165.201.5 ftp 10.1.1.3 ftp netmask
255.255.255.255
Step 4
Redirect HTTP requests for the security appliance outside interface address to 10.1.1.5 by entering the
following command:
hostname(config)# static (inside,outside) tcp interface www 10.1.1.5 www netmask
255.255.255.255
Step 5
Redirect HTTP requests on port 8080 for PAT address 209.165.201.15 to 10.1.1.7 port 80 by entering
the following command:
hostname(config)# static (inside,outside) tcp 209.165.201.15 8080 10.1.1.7 www netmask
255.255.255.255
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18
Permitting or Denying Network Access
This chapter describes how to control network access through the security appliance using access lists.
To create an extended access lists or an EtherType access list, see Chapter 16, “Identifying Traffic with
Access Lists.”
Note
You use ACLs to control network access in both routed and transparent firewall modes. In transparent
mode, you can use both extended ACLs (for Layer 3 traffic) and EtherType ACLs (for Layer 2 traffic).
To access the security appliance interface for management access, you do not also need an access list
allowing the host IP address. You only need to configure management access according to Chapter 40,
“Managing System Access.”
This chapter includes the following sections:
•
Inbound and Outbound Access List Overview, page 18-1
•
Applying an Access List to an Interface, page 18-2
Inbound and Outbound Access List Overview
By default, all traffic from a higher-security interface to a lower-security interface is allowed. Access
lists let you either allow traffic from lower-security interfaces, or restrict traffic from higher-security
interfaces.
The security appliance supports two types of access lists:
Note
•
Inbound—Inbound access lists apply to traffic as it enters an interface.
•
Outbound—Outbound access lists apply to traffic as it exits an interface.
“Inbound” and “outbound” refer to the application of an access list on an interface, either to traffic
entering the security appliance on an interface or traffic exiting the security appliance on an interface.
These terms do not refer to the movement of traffic from a lower security interface to a higher security
interface, commonly known as inbound, or from a higher to lower interface, commonly known as
outbound.
An outbound access list is useful, for example, if you want to allow only certain hosts on the inside
networks to access a web server on the outside network. Rather than creating multiple inbound access
lists to restrict access, you can create a single outbound access list that allows only the specified hosts
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Applying an Access List to an Interface
(see Figure 18-1). See the “IP Addresses Used for Access Lists When You Use NAT” section on
page 16-3 for information about NAT and IP addresses. The outbound access list prevents any other hosts
from reaching the outside network.
Figure 18-1
Outbound Access List
Web Server:
209.165.200.225
Security
appliance
Outside
ACL Outbound
Permit HTTP from 209.165.201.4, 209.165.201.6,
and 209.165.201.8 to 209.165.200.225
Deny all others
ACL Inbound
Permit from any to any
10.1.1.14
HR
ACL Inbound
Permit from any to any
209.165.201.4
Static NAT
10.1.2.67
209.165.201.6
Static NAT
Eng
ACL Inbound
Permit from any to any
10.1.3.34
209.165.201.8
Static NAT
132210
Inside
See the following commands for this example:
hostname(config)# access-list OUTSIDE extended permit tcp host 209.165.201.4
host 209.165.200.225 eq www
hostname(config)# access-list OUTSIDE extended permit tcp host 209.165.201.6
host 209.165.200.225 eq www
hostname(config)# access-list OUTSIDE extended permit tcp host 209.165.201.8
host 209.165.200.225 eq www
hostname(config)# access-group OUTSIDE out interface outside
Applying an Access List to an Interface
To apply an extended access list to the inbound or outbound direction of an interface, enter the following
command:
hostname(config)# access-group access_list_name {in | out} interface interface_name
[per-user-override]
You can apply one access list of each type (extended and EtherType) to both directions of the interface.
See the “Inbound and Outbound Access List Overview” section on page 18-1 for more information about
access list directions.
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Applying an Access List to an Interface
The per-user-override keyword allows dynamic access lists that are downloaded for user authorization
to override the access list assigned to the interface. For example, if the interface access list denies all
traffic from 10.0.0.0, but the dynamic access list permits all traffic from 10.0.0.0, then the dynamic
access list overrides the interface access list for that user. See the “Configuring RADIUS Authorization”
section for more information about per-user access lists. The per-user-override keyword is only
available for inbound access lists.
For connectionless protocols, you need to apply the access list to the source and destination interfaces
if you want traffic to pass in both directions. For example, you can allow BGP in an EtherType access
list in transparent mode, and you need to apply the access list to both interfaces.
The following example illustrates the commands required to enable access to an inside web server with
the IP address 209.165.201.12 (this IP address is the address visible on the outside interface after NAT):
hostname(config)# access-list ACL_OUT extended permit tcp any host 209.165.201.12 eq www
hostname(config)# access-group ACL_OUT in interface outside
You also need to configure NAT for the web server.
The following access lists allow all hosts to communicate between the inside and hr networks, but only
specific hosts to access the outside network:
hostname(config)# access-list ANY extended permit ip any any
hostname(config)# access-list OUT extended permit ip host 209.168.200.3 any
hostname(config)# access-list OUT extended permit ip host 209.168.200.4 any
hostname(config)# access-group ANY in interface inside
hostname(config)# access-group ANY in interface hr
hostname(config)# access-group OUT out interface outside
For example, the following sample access list allows common EtherTypes originating on the inside
interface:
hostname(config)#
hostname(config)#
hostname(config)#
hostname(config)#
access-list ETHER ethertype permit ipx
access-list ETHER ethertype permit bpdu
access-list ETHER ethertype permit mpls-unicast
access-group ETHER in interface inside
The following access list allows some EtherTypes through the security appliance, but denies all others:
hostname(config)#
hostname(config)#
hostname(config)#
hostname(config)#
hostname(config)#
access-list ETHER ethertype permit 0x1234
access-list ETHER ethertype permit bpdu
access-list ETHER ethertype permit mpls-unicast
access-group ETHER in interface inside
access-group ETHER in interface outside
The following access list denies traffic with EtherType 0x1256 but allows all others on both interfaces:
hostname(config)#
hostname(config)#
hostname(config)#
hostname(config)#
access-list nonIP ethertype deny 1256
access-list nonIP ethertype permit any
access-group ETHER in interface inside
access-group ETHER in interface outside
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Applying an Access List to an Interface
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19
Applying AAA for Network Access
This chapter describes how to enable AAA (pronounced “triple A”) for network access.
For information about AAA for management access, see the “Configuring AAA for System
Administrators” section on page 40-5.
This chapter contains the following sections:
•
AAA Performance, page 19-1
•
Configuring Authentication for Network Access, page 19-1
•
Configuring Authorization for Network Access, page 19-6
•
Configuring Accounting for Network Access, page 19-13
•
Using MAC Addresses to Exempt Traffic from Authentication and Authorization, page 19-14
AAA Performance
The security appliance uses “cut-through proxy” to significantly improve performance compared to a
traditional proxy server. The performance of a traditional proxy server suffers because it analyzes every
packet at the application layer of the OSI model. The security appliance cut-through proxy challenges a
user initially at the application layer and then authenticates against standard AAA servers or the local
database. After the security appliance authenticates the user, it shifts the session flow, and all traffic
flows directly and quickly between the source and destination while maintaining session state
information.
Configuring Authentication for Network Access
This section includes the following topics:
•
Authentication Overview, page 19-2
•
Enabling Network Access Authentication, page 19-3
•
Enabling Secure Authentication of Web Clients, page 19-5
•
Authenticating Directly with the Security Appliance, page 19-6
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Configuring Authentication for Network Access
Authentication Overview
The security appliance lets you configure network access authentication using AAA servers. This section
includes the following topics:
•
One-Time Authentication, page 19-2
•
Applications Required to Receive an Authentication Challenge, page 19-2
•
Security Appliance Authentication Prompts, page 19-2
•
Static PAT and HTTP, page 19-3
•
Enabling Network Access Authentication, page 19-3
One-Time Authentication
A user at a given IP address only needs to authenticate one time for all rules and types, until the
authentication session expires. (See the timeout uauth command in the Cisco Security Appliance
Command Reference for timeout values.) For example, if you configure the security appliance to
authenticate Telnet and FTP, and a user first successfully authenticates for Telnet, then as long as the
authentication session exists, the user does not also have to authenticate for FTP.
Applications Required to Receive an Authentication Challenge
Although you can configure the security appliance to require authentication for network access to any
protocol or service, users can authenticate directly with HTTP, HTTPS, Telnet, or FTP only. A user must
first authenticate with one of these services before the security appliance allows other traffic requiring
authentication.
The authentication ports that the security appliance supports for AAA are fixed:
•
Port 21 for FTP
•
Port 23 for Telnet
•
Port 80 for HTTP
•
Port 443 for HTTPS
Security Appliance Authentication Prompts
For Telnet and FTP, the security appliance generates an authentication prompt.
For HTTP, the security appliance uses basic HTTP authentication by default, and provides an
authentication prompt. You can optionally configure the security appliance to redirect users to an
internal web page where they can enter their username and password (configured with the aaa
authentication listener command).
For HTTPS, the security appliance generates a custom login screen. You can optionally configure the
security appliance to redirect users to an internal web page where they can enter their username and
password (configured with the aaa authentication listener command).
Redirection is an improvement over the basic method because it provides an improved user experience
when authenticating, and an identical user experience for HTTP and HTTPS in both Easy VPN and
firewall modes. It also supports authenticating directly with the security appliance.
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You might want to continue to use basic HTTP authentication if: you do not want the security appliance
to open listening ports; if you use NAT on a router and you do not want to create a translation rule for
the web page served by the security appliance; basic HTTP authentication might work better with your
network. For example non-browser applications, like when a URL is embedded in email, might be more
compatible with basic authentication.
After you authenticate correctly, the security appliance redirects you to your original destination. If the
destination server also has its own authentication, the user enters another username and password. If you
use basic HTTP authentication and need to enter another username and password for the destination
server, then you need to configure the virtual http command.
Note
If you use HTTP authentication without using the aaa authentication secure-http-client command, the
username and password are sent from the client to the security appliance in clear text. We recommend
that you use the aaa authentication secure-http-client command whenever you enable HTTP
authentication. For more information about the aaa authentication secure-http-client command, see
the “Enabling Secure Authentication of Web Clients” section on page 19-5.
For FTP, a user has the option of entering the security appliance username followed by an at sign (@)
and then the FTP username ([email protected]). For the password, the user enters the security appliance
password followed by an at sign (@) and then the FTP password ([email protected]). For example,
enter the following text.
name> [email protected]
password> [email protected]
This feature is useful when you have cascaded firewalls that require multiple logins. You can separate
several names and passwords by multiple at signs (@).
Static PAT and HTTP
For HTTP authentication, the security appliance checks real ports when static PAT is configured. If it
detects traffic destined for real port 80, regardless of the mapped port, the security appliance intercepts
the HTTP connection and enforces authentication.
For example, assume that outside TCP port 889 is translated to port 80 (www) and that any relevant
access lists permit the traffic:
static (inside,outside) tcp 10.48.66.155 889 192.168.123.10 www netmask 255.255.255.255
Then when users try to access 10.48.66.155 on port 889, the security appliance intercepts the traffic and
enforces HTTP authentication. Users see the HTTP authentication page in their web browsers before the
security appliance allows HTTP connection to complete.
If the local port is different than port 80, as in the following example:
static (inside,outside) tcp 10.48.66.155 889 192.168.123.10 111 netmask 255.255.255.255
Then users do not see the authentication page. Instead, the security appliance sends to the web browser
an error message indicating that the user must be authenticated prior using the requested service.
Enabling Network Access Authentication
To enable network access authentication, perform the following steps:
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Step 1
Using the aaa-server command, identify your AAA servers. If you have already identified your AAA
servers, continue to the next step.
For more information about identifying AAA servers, see the “Identifying AAA Server Groups and
Servers” section on page 13-12.
Step 2
Using the access-list command, create an access list that identifies the source addresses and destination
addresses of traffic you want to authenticate. For steps, see the “Adding an Extended Access List”
section on page 16-5.
The permit ACEs mark matching traffic for authentication, while deny entries exclude matching traffic
from authentication. Be sure to include the destination ports for either HTTP, HTTPS, Telnet, or FTP in
the access list because the user must authenticate with one of these services before other services are
allowed through the security appliance.
Step 3
To configure authentication, enter the following command:
hostname(config)# aaa authentication match acl_name interface_name server_group
Where acl_name is the name of the access list you created in Step 2, interface_name is the name of the
interface as specified with the nameif command, and server_group is the AAA server group you created
in Step 1.
Note
Step 4
You can alternatively use the aaa authentication include command (which identifies traffic within the
command). However, you cannot use both methods in the same configuration. See the Cisco Security
Appliance Command Reference for more information.
(Optional) To enable the redirection method of authentication for HTTP or HTTPS connections, enter
the following command:
hostname(config)# aaa authentication listener http[s] interface_name
redirect
[port portnum]
where the interface_name argument is the interface on which you want to enable listening ports.
The port portnum argument specifies the port number that the security appliance listens on; the defaults
are 80 (HTTP) and 443 (HTTPS).
Enter this command separately for HTTP and for HTTPS.
Step 5
(Optional) If you are using the local database for network access authentication and you want to limit
the number of consecutive failed login attempts that the security appliance allows any given user
account, use the following command:
hostname(config)# aaa local authentication attempts max-fail number
Where number is between 1 and 16.
For example:
hostname(config)# aaa local authentication attempts max-fail 7
Tip
To clear the lockout status of a specific user or all users, use the clear aaa local user lockout command.
For example, the following commands authenticate all inside HTTP traffic and SMTP traffic:
hostname(config)# aaa-server AuthOutbound protocol tacacs+
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hostname(config-aaa-server-group)# exit
hostname(config)# aaa-server AuthOutbound (inside) host 10.1.1.1
hostname(config-aaa-server-host)# key TACPlusUauthKey
hostname(config-aaa-server-host)# exit
hostname(config)# access-list MAIL_AUTH extended permit tcp any any eq smtp
hostname(config)# access-list MAIL_AUTH extended permit tcp any any eq www
hostname(config)# aaa authentication match MAIL_AUTH inside AuthOutbound
hostname(config)# aaa authentication listener http inside redirect
The following commands authenticate Telnet traffic from the outside interface to a particular server
(209.165.201.5):
hostname(config)# aaa-server AuthInbound protocol tacacs+
hostname(config-aaa-server-group)# exit
hostname(config)# aaa-server AuthInbound (inside) host 10.1.1.1
hostname(config-aaa-server-host)# key TACPlusUauthKey
hostname(config-aaa-server-host)# exit
hostname(config)# access-list TELNET_AUTH extended permit tcp any host 209.165.201.5 eq
telnet
hostname(config)# aaa authentication match TELNET_AUTH outside AuthInbound
Enabling Secure Authentication of Web Clients
The security appliance provides a method of securing HTTP authentication. Without securing HTTP
authentication, usernames and passwords from the client to the security appliance would be passed as
clear text. By using the aaa authentication secure-http-client command, you enable the exchange of
usernames and passwords between a web client and the security appliance with HTTPS.
After enabling this feature, when a user requires authentication when using HTTP, the security appliance
redirects the HTTP user to an HTTPS prompt. After you authenticate correctly, the security appliance
redirects you to the original HTTP URL.
To enable secure authentication of web clients, enter the following command:
hostname(config)# aaa authentication secure-http-client
Secured web-client authentication has the following limitations:
•
A maximum of 16 concurrent HTTPS authentication sessions are allowed. If all 16 HTTPS
authentication processes are running, a new connection requiring authentication will not succeed.
•
When uauth timeout 0 is configured (the uauth timeout is set to 0), HTTPS authentication might
not work. If a browser initiates multiple TCP connections to load a web page after HTTPS
authentication, the first connection is let through, but the subsequent connections trigger
authentication. As a result, users are continuously presented with an authentication page, even if the
correct username and password are entered each time. To work around this, set the uauth timeout
to 1 second with the timeout uauth 0:0:1 command. However, this workaround opens a 1-second
window of opportunity that might allow non-authenticated users to go through the firewall if they
are coming from the same source IP address.
•
Because HTTPS authentication occurs on the SSL port 443, users must not configure an access-list
command statement to block traffic from the HTTP client to HTTP server on port 443. Furthermore,
if static PAT is configured for web traffic on port 80, it must also be configured for the SSL port. In
the following example, the first line configures static PAT for web traffic and the second line must
be added to support the HTTPS authentication configuration.
static (inside,outside) tcp 10.132.16.200 www 10.130.16.10 www
static (inside,outside) tcp 10.132.16.200 443 10.130.16.10 443
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Authenticating Directly with the Security Appliance
If you do not want to allow HTTP, HTTPS, Telnet, or FTP through the security appliance but want to
authenticate other types of traffic, you can authenticate with the security appliance directly using HTTP,
HTTPS, or Telnet.
This section includes the following topics:
•
Enabling Direct Authentication Using HTTP and HTTPS, page 19-6
•
Enabling Direct Authentication Using Telnet, page 19-6
Enabling Direct Authentication Using HTTP and HTTPS
If you enabled the redirect method of HTTP and HTTPS authentication in the “Enabling Network Access
Authentication” section on page 19-3, then you also automatically enabled direct authentication. If you
want to continue to use basic HTTP authentication, but want to enable direct authentication for HTTP
and HTTPS, then enter the following command:
hostname(config)# aaa authentication listener http[s] interface_name
[port portnum]
where the interface_name argument is the interface on which you want to enable direct authentication.
The port portnum argument specifies the port number that the security appliance listens on; the defaults
are 80 (HTTP) and 443 (HTTPS).
Enter this command separately for HTTP and for HTTPS.
You can authenticate directly with the security appliance at the following URLs when you enable AAA
for the interface:
http://interface_ip[:port]/netaccess/connstatus.html
https://interface_ip[:port]/netaccess/connstatus.html
Enabling Direct Authentication Using Telnet
To enable direct authentication with Telnet, configure a virtual Telnet server. With virtual Telnet, the user
Telnets to a given IP address configured on the security appliance, and the security appliance provides a
Telnet prompt. To configure a virtual Telnet server, enter the following command:
hostname(config)# virtual telnet ip_address
where the ip_address argument sets the IP address for the virtual Telnet server. Make sure this address
is an unused address that is routed to the security appliance. For example, if you perform NAT for inside
addresses when they access the outside, and you want to provide outside access to the virtual Telnet
server, you can use one of the global NAT addresses for the virtual Telnet server address.
Configuring Authorization for Network Access
After a user authenticates for a given connection, the security appliance can use authorization to further
control traffic from the user.
This section includes the following topics:
•
Configuring TACACS+ Authorization, page 19-7
•
Configuring RADIUS Authorization, page 19-8
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Configuring TACACS+ Authorization
You can configure the security appliance to perform network access authorization with TACACS+. You
identify the traffic to be authorized by specifying access lists that authorization rules must match.
Alternatively, you can identify the traffic directly in authorization rules themselves.
Tip
Using access lists to identify traffic to be authorized can greatly reduced the number of authorization
commands you must enter. This is because each authorization rule you enter can specify only one source
and destination subnet and service, whereas an access list can include many entries.
Authentication and authorization statements are independent; however, any unauthenticated traffic
matched by an authorization statement will be denied. For authorization to succeed, a user must first
authenticate with the security appliance. Because a user at a given IP address only needs to authenticate
one time for all rules and types, if the authentication session hasn’t expired, authorization can occur even
if the traffic is matched by an authentication statement.
After a user authenticates, the security appliance checks the authorization rules for matching traffic. If
the traffic matches the authorization statement, the security appliance sends the username to the
TACACS+ server. The TACACS+ server responds to the security appliance with a permit or a deny for
that traffic, based on the user profile. The security appliance enforces the authorization rule in the
response.
See the documentation for your TACACS+ server for information about configuring network access
authorizations for a user.
To configure TACACS+ authorization, perform the following steps:
Step 1
Enable authentication. For more information, see the “Enabling Network Access Authentication” section
on page 19-3. If you have already enabled authentication, continue to the next step.
Step 2
Using the access-list command, create an access list that identifies the source addresses and destination
addresses of traffic you want to authorize. For steps, see the “Adding an Extended Access List” section
on page 16-5.
The permit ACEs mark matching traffic for authorization, while deny entries exclude matching traffic
from authorization. The access list you use for authorization matching should contain rules that are equal
to or a subset of the rules in the access list used for authentication matching.
Note
Step 3
If you have configured authentication and want to authorize all the traffic being authenticated,
you can use the same access list you created for use with the aaa authentication match
command.
To enable authorization, enter the following command:
hostname(config)# aaa authorization match acl_name interface_name server_group
where acl_name is the name of the access list you created in Step 2, interface_name is the name of the
interface as specified with the nameif command or by default, and server_group is the AAA server group
you created when you enabled authentication.
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Note
Alternatively, you can use the aaa authorization include command (which identifies traffic
within the command) but you cannot use both methods in the same configuration. See the Cisco
Security Appliance Command Reference for more information.
The following commands authenticate and authorize inside Telnet traffic. Telnet traffic to servers other
than 209.165.201.5 can be authenticated alone, but traffic to 209.165.201.5 requires authorization.
hostname(config)# access-list TELNET_AUTH extended permit tcp any any eq telnet
hostname(config)# access-list SERVER_AUTH extended permit tcp any host 209.165.201.5 eq
telnet
hostname(config)# aaa-server AuthOutbound protocol tacacs+
hostname(config-aaa-server-group)# exit
hostname(config)# aaa-server AuthOutbound (inside) host 10.1.1.1
hostname(config-aaa-server-host)# key TACPlusUauthKey
hostname(config-aaa-server-host)# exit
hostname(config)# aaa authentication match TELNET_AUTH inside AuthOutbound
hostname(config)# aaa authorization match SERVER_AUTH inside AuthOutbound
Configuring RADIUS Authorization
When authentication succeeds, the RADIUS protocol returns user authorizations in the access-accept
message sent by a RADIUS server. For more information about configuring authentication, see the
“Configuring Authentication for Network Access” section on page 19-1.
When you configure the security appliance to authenticate users for network access, you are also
implicitly enabling RADIUS authorizations; therefore, this section contains no information about
configuring RADIUS authorization on the security appliance. It does provide information about how the
security appliance handles access list information received from RADIUS servers.
You can configure a RADIUS server to download an access list to the security appliance or an access list
name at the time of authentication. The user is authorized to do only what is permitted in the
user-specific access list.
Note
If you have used the access-group command to apply access lists to interfaces, be aware of the following
effects of the per-user-override keyword on authorization by user-specific access lists:
•
Without the per-user-override keyword, traffic for a user session must be permitted by both the
interface access list and the user-specific access list.
•
With the per-user-override keyword, the user-specific access list determines what is permitted.
For more information, see the access-group command entry in the Cisco Security Appliance Command
Reference.
This section includes the following topics:
•
Configuring a RADIUS Server to Send Downloadable Access Control Lists, page 19-9
•
Configuring a RADIUS Server to Download Per-User Access Control List Names, page 19-12
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Configuring a RADIUS Server to Send Downloadable Access Control Lists
This section describes how to configure Cisco Secure ACS or a third-party RADIUS server, and includes
the following topics:
•
About the Downloadable Access List Feature and Cisco Secure ACS, page 19-9
•
Configuring Cisco Secure ACS for Downloadable Access Lists, page 19-10
•
Configuring Any RADIUS Server for Downloadable Access Lists, page 19-11
•
Converting Wildcard Netmask Expressions in Downloadable Access Lists, page 19-12
About the Downloadable Access List Feature and Cisco Secure ACS
Downloadable access lists is the most scalable means of using Cisco Secure ACS to provide the
appropriate access lists for each user. It provides the following capabilities:
•
Unlimited access list size—Downloadable access lists are sent using as many RADIUS packets as
required to transport the full access list from Cisco Secure ACS to the security appliance.
•
Simplified and centralized management of access lists—Downloadable access lists enable you to
write a set of access lists once and apply it to many user or group profiles and distribute it to many
security appliances.
This approach is most useful when you have very large access list sets that you want to apply to more
than one Cisco Secure ACS user or group; however, its ability to simplify Cisco Secure ACS user and
group management makes it useful for access lists of any size.
The security appliance receives downloadable access lists from Cisco Secure ACS using the following
process:
1.
The security appliance sends a RADIUS authentication request packet for the user session.
2.
If Cisco Secure ACS successfully authenticates the user, Cisco Secure ACS returns a RADIUS
access-accept message that contains the internal name of the applicable downloadable access list.
The Cisco IOS cisco-av-pair RADIUS VSA (vendor 9, attribute 1) contains the following
attribute-value pair to identify the downloadable access list set:
ACS:CiscoSecure-Defined-ACL=acl-set-name
where acl-set-name is the internal name of the downloadable access list, which is a combination of
the name assigned to the access list by the Cisco Secure ACS administrator and the date and time
that the access list was last modified.
3.
The security appliance examines the name of the downloadable access list and determines if it has
previously received the named downloadable access list.
– If the security appliance has previously received the named downloadable access list,
communication with Cisco Secure ACS is complete and the security appliance applies the
access list to the user session. Because the name of the downloadable access list includes the
date and time it was last modified, matching the name sent by Cisco Secure ACS to the name of
an access list previous downloaded means that the security appliance has the most recent
version of the downloadable access list.
– If the security appliance has not previously received the named downloadable access list, it may
have an out-of-date version of the access list or it may not have downloaded any version of the
access list. In either case, the security appliance issues a RADIUS authentication request using
the downloadable access list name as the username in the RADIUS request and a null password
attribute. In a cisco-av-pair RADIUS VSA, the request also includes the following
attribute-value pairs:
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AAA:service=ip-admission
AAA:event=acl-download
In addition, the security appliance signs the request with the Message-Authenticator attribute
(IETF RADIUS attribute 80).
4.
Upon receipt of a RADIUS authentication request that has a username attribute containing the name
of a downloadable access list, Cisco Secure ACS authenticates the request by checking the
Message-Authenticator attribute. If the Message-Authenticator attribute is missing or incorrect,
Cisco Secure ACS ignores the request. The presence of the Message-Authenticator attribute
prevents malicious use of a downloadable access list name to gain unauthorized network access. The
Message-Authenticator attribute and its use are defined in RFC 2869, RADIUS Extensions,
available at http://www.ietf.org.
5.
If the access list required is less than approximately 4 KB in length, Cisco Secure ACS responds
with an access-accept message containing the access list. The largest access list that can fit in a
single access-accept message is slightly less than 4 KB because some of the message must be other
required attributes.
Cisco Secure ACS sends the downloadable access list in a cisco-av-pair RADIUS VSA. The access
list is formatted as a series of attribute-value pairs that each contain an ACE and are numbered
serially:
ip:inacl#1=ACE-1
ip:inacl#2=ACE-2
.
.
.
ip:inacl#n=ACE-n
An example of an attribute-value pair follows:
ip:inacl#1=permit tcp 10.1.0.0 255.0.0.0 10.0.0.0 255.0.0.0
6.
If the access list required is more than approximately 4 KB in length, Cisco Secure ACS responds
with an access-challenge message that contains a portion of the access list, formatted as described
above, and an State attribute (IETF RADIUS attribute 24), which contains control data used by
Cisco Secure ACS to track the progress of the download. Cisco Secure ACS fits as many complete
attribute-value pairs into the cisco-av-pair RADIUS VSA as it can without exceeding the maximum
RADIUS message size.
The security appliance stores the portion of the access list received and responds with another
access-request message containing the same attributes as the first request for the downloadable
access list plus a copy of the State attribute received in the access-challenge message.
This repeats until Cisco Secure ACS sends the last of the access list in an access-accept message.
Configuring Cisco Secure ACS for Downloadable Access Lists
You can configure downloadable access lists on Cisco Secure ACS as a shared profile component and
then assign the access list to a group or to an individual user.
The access list definition consists of one or more security appliance commands that are similar to the
extended access-list command (see the “Adding an Extended Access List” section on page 16-5), except
without the following prefix:
access-list acl_name extended
The following example is a downloadable access list definition on Cisco Secure ACS version 3.3:
+--------------------------------------------+
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| Shared profile Components
|
|
|
|
Downloadable IP ACLs Content
|
|
|
| Name:
acs_ten_acl
|
|
|
|
ACL Definitions
|
|
|
| permit tcp any host 10.0.0.254
|
| permit udp any host 10.0.0.254
|
| permit icmp any host 10.0.0.254
|
| permit tcp any host 10.0.0.253
|
| permit udp any host 10.0.0.253
|
| permit icmp any host 10.0.0.253
|
| permit tcp any host 10.0.0.252
|
| permit udp any host 10.0.0.252
|
| permit icmp any host 10.0.0.252
|
| permit ip any any
|
+--------------------------------------------+
For more information about creating downloadable access lists and associating them with users, see the
user guide for your version of Cisco Secure ACS.
On the security appliance, the downloaded access list has the following name:
#ACSACL#-ip-acl_name-number
The acl_name argument is the name that is defined on Cisco Secure ACS (acs_ten_acl in the preceding
example), and number is a unique version ID generated by Cisco Secure ACS.
The downloaded access list on the security appliance consists of the following lines:
access-list
access-list
access-list
access-list
access-list
access-list
access-list
access-list
access-list
access-list
#ACSACL#-ip-asa-acs_ten_acl-3b5385f7
#ACSACL#-ip-asa-acs_ten_acl-3b5385f7
#ACSACL#-ip-asa-acs_ten_acl-3b5385f7
#ACSACL#-ip-asa-acs_ten_acl-3b5385f7
#ACSACL#-ip-asa-acs_ten_acl-3b5385f7
#ACSACL#-ip-asa-acs_ten_acl-3b5385f7
#ACSACL#-ip-asa-acs_ten_acl-3b5385f7
#ACSACL#-ip-asa-acs_ten_acl-3b5385f7
#ACSACL#-ip-asa-acs_ten_acl-3b5385f7
#ACSACL#-ip-asa-acs_ten_acl-3b5385f7
permit
permit
permit
permit
permit
permit
permit
permit
permit
permit
tcp any host 10.0.0.254
udp any host 10.0.0.254
icmp any host 10.0.0.254
tcp any host 10.0.0.253
udp any host 10.0.0.253
icmp any host 10.0.0.253
tcp any host 10.0.0.252
udp any host 10.0.0.252
icmp any host 10.0.0.252
ip any any
Configuring Any RADIUS Server for Downloadable Access Lists
You can configure any RADIUS server that supports Cisco IOS RADIUS VSAs to send user-specific
access lists to the security appliance in a Cisco IOS RADIUS cisco-av-pair VSA (vendor 9, attribute 1).
In the cisco-av-pair VSA, configure one or more ACEs that are similar to the access-list extended
command (see the “Adding an Extended Access List” section on page 16-5), except that you replace the
following command prefix:
access-list acl_name extended
with the following text:
ip:inacl#nnn=
The nnn argument is a number in the range from 0 to 999999999 that identifies the order of the command
statement to be configured on the security appliance. If this parameter is omitted, the sequence value is
0, and the order of the ACEs inside the cisco-av-pair RADIUS VSA is used.
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The following example is an access list definition as it should be configured for a cisco-av-pair VSA on
a RADIUS server:
ip:inacl#1=permit tcp 10.1.0.0 255.0.0.0 10.0.0.0 255.0.0.0
ip:inacl#99=deny tcp any any
ip:inacl#2=permit udp 10.1.0.0 255.0.0.0 10.0.0.0 255.0.0.0
ip:inacl#100=deny udp any any
ip:inacl#3=permit icmp 10.1.0.0 255.0.0.0 10.0.0.0 255.0.0.0
For information about making unique per user the access lists that are sent in the cisco-av-pair attribute,
see the documentation for your RADIUS server.
On the security appliance, the downloaded access list name has the following format:
AAA-user-username
The username argument is the name of the user that is being authenticated.
The downloaded access list on the security appliance consists of the following lines. Notice the order
based on the numbers identified on the RADIUS server.
access-list
access-list
access-list
access-list
access-list
AAA-user-bcham34-79AD4A08
AAA-user-bcham34-79AD4A08
AAA-user-bcham34-79AD4A08
AAA-user-bcham34-79AD4A08
AAA-user-bcham34-79AD4A08
permit tcp 10.1.0.0 255.0.0.0 10.0.0.0 255.0.0.0
permit udp 10.1.0.0 255.0.0.0 10.0.0.0 255.0.0.0
permit icmp 10.1.0.0 255.0.0.0 10.0.0.0 255.0.0.0
deny tcp any any
deny udp any any
Downloaded access lists have two spaces between the word “access-list” and the name. These spaces
serve to differentiate a downloaded access list from a local access list. In this example, “79AD4A08” is
a hash value generated by the security appliance to help determine when access list definitions have
changed on the RADIUS server.
Converting Wildcard Netmask Expressions in Downloadable Access Lists
If a RADIUS server provides downloadable access lists to Cisco VPN 3000 Series Concentrators as well
as to the security appliance, you may need the security appliance to convert wildcard netmask
expressions to standard netmask expressions. This is because Cisco VPN 3000 Series Concentrators
support wildcard netmask expressions but the security appliance only supports standard netmask
expressions. Configuring the security appliance to convert wildcard netmask expressions helps minimize
the effects of these differences upon how you configure downloadable access lists on your RADIUS
servers. Translation of wildcard netmask expressions means that downloadable access lists written for
Cisco VPN 3000 Series Concentrators can be used by the security appliance without altering the
configuration of the downloadable access lists on the RADIUS server.
You configure access list netmask conversion on a per server basis, using the acl-netmask-convert
command, available in the AAA-server configuration mode. For more information about configuring a
RADIUS server, see “Identifying AAA Server Groups and Servers” section on page 13-12. For more
information about the acl-netmask-convert command, see the Cisco Security Appliance Command
Reference.
Configuring a RADIUS Server to Download Per-User Access Control List Names
To download a name for an access list that you already created on the security appliance from the
RADIUS server when a user authenticates, configure the IETF RADIUS filter-id attribute (attribute
number 11) as follows:
filter-id=acl_name
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Configuring Accounting for Network Access
Note
In Cisco Secure ACS, the value for filter-id attributes are specified in boxes in the HTML interface,
omitting filter-id= and entering only acl_name.
For information about making unique per user the filter-id attribute value, see the documentation for your
RADIUS server.
See the “Adding an Extended Access List” section on page 16-5 to create an access list on the security
appliance.
Configuring Accounting for Network Access
The security appliance can send accounting information to a RADIUS or TACACS+ server about any
TCP or UDP traffic that passes through the security appliance. If that traffic is also authenticated, then
the AAA server can maintain accounting information by username. If the traffic is not authenticated, the
AAA server can maintain accounting information by IP address. Accounting information includes when
sessions start and stop, username, the number of bytes that pass through the security appliance for the
session, the service used, and the duration of each session.
To configure accounting, perform the following steps:
Step 1
If you want the security appliance to provide accounting data per user, you must enable authentication.
For more information, see the “Enabling Network Access Authentication” section on page 19-3. If you
want the security appliance to provide accounting data per IP address, enabling authentication is not
necessary and you can continue to the next step.
Step 2
Using the access-list command, create an access list that identifies the source addresses and destination
addresses of traffic you want accounted. For steps, see the “Adding an Extended Access List” section on
page 16-5.
The permit ACEs mark matching traffic for authorization, while deny entries exclude matching traffic
from authorization.
Note
Step 3
If you have configured authentication and want accounting data for all the traffic being
authenticated, you can use the same access list you created for use with the aaa authentication
match command.
To enable accounting, enter the following command:
hostname(config)# aaa accounting match acl_name interface_name server_group
Note
Alternatively, you can use the aaa accounting include command (which identifies traffic within
the command) but you cannot use both methods in the same configuration. See the Cisco
Security Appliance Command Reference for more information.
The following commands authenticate, authorize, and account for inside Telnet traffic. Telnet traffic to
servers other than 209.165.201.5 can be authenticated alone, but traffic to 209.165.201.5 requires
authorization and accounting.
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Using MAC Addresses to Exempt Traffic from Authentication and Authorization
hostname(config)# aaa-server AuthOutbound protocol tacacs+
hostname(config-aaa-server-group)# exit
hostname(config)# aaa-server AuthOutbound (inside) host 10.1.1.1
hostname(config-aaa-server-host)# key TACPlusUauthKey
hostname(config-aaa-server-host)# exit
hostname(config)# access-list TELNET_AUTH extended permit tcp any any eq telnet
hostname(config)# access-list SERVER_AUTH extended permit tcp any host 209.165.201.5 eq
telnet
hostname(config)# aaa authentication match TELNET_AUTH inside AuthOutbound
hostname(config)# aaa authorization match SERVER_AUTH inside AuthOutbound
hostname(config)# aaa accounting match SERVER_AUTH inside AuthOutbound
Using MAC Addresses to Exempt Traffic from Authentication
and Authorization
The security appliance can exempt from authentication and authorization any traffic from specific MAC
addresses. For example, if the security appliance authenticates TCP traffic originating on a particular
network but you want to allow unauthenticated TCP connections from a specific server, you would use
a MAC exempt rule to exempt from authentication and authorization any traffic from the server specified
by the rule.
This feature is particularly useful to exempt devices such as IP phones that cannot respond to
authentication prompts.
To use MAC addresses to exempt traffic from authentication and authorization, perform the following
steps:
Step 1
To configure a MAC list, enter the following command:
hostname(config)# mac-list id {deny | permit} mac macmask
Where the id argument is the hexadecimal number that you assign to the MAC list. To group a set of
MAC addresses, enter the mac-list command as many times as needed with the same ID value. Because
you can only use one MAC list for AAA exemption, be sure that your MAC list includes all the MAC
addresses you want to exempt. You can create multiple MAC lists, but you can only use one at a time.
The order of entries matters, because the packet uses the first entry it matches, as opposed to a best match
scenario. If you have a permit entry, and you want to deny an address that is allowed by the permit entry,
be sure to enter the deny entry before the permit entry.
The mac argument specifies the source MAC address in 12-digit hexadecimal form; that is,
nnnn.nnnn.nnnn.
The macmask argument specifies the portion of the MAC address that should be used for matching. For
example, ffff.ffff.ffff matches the MAC address exactly. ffff.ffff.0000 matches only the first 8 digits.
Step 2
To exempt traffic for the MAC addresses specified in a particular MAC list, enter the following
command:
hostname(config)# aaa mac-exempt match id
Where id is the string identifying the MAC list containing the MAC addresses whose traffic is to be
exempt from authentication and authorization. You can only enter one instance of the aaa mac-exempt
command.
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The following example bypasses authentication for a single MAC address:
hostname(config)# mac-list abc permit 00a0.c95d.0282 ffff.ffff.ffff
hostname(config)# aaa mac-exempt match abc
The following entry bypasses authentication for all Cisco IP Phones, which have the hardware ID
0003.E3:
hostname(config)# mac-list acd permit 0003.E300.0000 FFFF.FF00.0000
hostname(config)# aaa mac-exempt match acd
The following example bypasses authentication for a a group of MAC addresses except for
00a0.c95d.02b2. Enter the deny statement before the permit statement, because 00a0.c95d.02b2 matches
the permit statement as well, and if it is first, the deny statement will never be matched.
hostname(config)# mac-list 1 deny 00a0.c95d.0282 ffff.ffff.ffff
hostname(config)# mac-list 1 permit 00a0.c95d.0000 ffff.ffff.0000
hostname(config)# aaa mac-exempt match 1
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20
Applying Filtering Services
This chapter describes ways to filter web traffic to reduce security risks or prevent inappropriate use.
This chapter contains the following sections:
•
Filtering Overview, page 20-1
•
Filtering ActiveX Objects, page 20-2
•
Filtering Java Applets, page 20-3
•
Filtering URLs and FTP Requests with an External Server, page 20-4
•
Viewing Filtering Statistics and Configuration, page 20-9
Filtering Overview
This section describes how filtering can provide greater control over traffic passing through the security
appliance. Filtering can be used in two distinct ways:
•
Filtering ActiveX objects or Java applets
•
Filtering with an external filtering server
Instead of blocking access altogether, you can remove specific undesirable objects from HTTP traffic,
such as ActiveX objects or Java applets, that may pose a security threat in certain situations.
You can also use URL filtering to direct specific traffic to an external filtering server, such an Secure
Computing SmartFilter (formerly N2H2) or Websense filtering server. Long URL, HTTPS, and FTP
filtering can now be enabled using both Websense and Secure Computing SmartFilter for URL filtering.
Filtering servers can block traffic to specific sites or types of sites, as specified by the security policy.
Note
URL caching will only work if the version of the URL server software from the URL server vender
supports it.
Because URL filtering is CPU-intensive, using an external filtering server ensures that the throughput of
other traffic is not affected. However, depending on the speed of your network and the capacity of your
URL filtering server, the time required for the initial connection may be noticeably slower when filtering
traffic with an external filtering server.
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Filtering ActiveX Objects
Filtering ActiveX Objects
This section describes how to apply filtering to remove ActiveX objects from HTTP traffic passing
through the firewall. This section includes the following topics:
•
ActiveX Filtering Overview, page 20-2
•
Enabling ActiveX Filtering, page 20-2
ActiveX Filtering Overview
ActiveX objects may pose security risks because they can contain code intended to attack hosts and
servers on a protected network. You can disable ActiveX objects with ActiveX filtering.
ActiveX controls, formerly known as OLE or OCX controls, are components you can insert in a web
page or other application. These controls include custom forms, calendars, or any of the extensive
third-party forms for gathering or displaying information. As a technology, ActiveX creates many
potential problems for network clients including causing workstations to fail, introducing network
security problems, or being used to attack servers.
The filter activex command blocks the HTML <object> commands by commenting them out within the
HTML web page. ActiveX filtering of HTML files is performed by selectively replacing the <APPLET>
and </APPLET> and <OBJECT CLASSID> and </OBJECT> tags with comments. Filtering of nested
tags is supported by converting top-level tags to comments.
Caution
This command also blocks any Java applets, image files, or multimedia objects that are embedded in
object tags .
If the <object> or </object> HTML tags split across network packets or if the code in the tags is longer
than the number of bytes in the MTU, security appliance cannot block the tag.
ActiveX blocking does not occur when users access an IP address referenced by the alias command or
for WebVPN traffic.
Enabling ActiveX Filtering
This section describes how to remove ActiveX objects in HTTP traffic passing through the security
appliance. To remove ActiveX objects, enter the following command in global configuration mode:
hostname(config)# filter activex
port[-port] local_ip local_mask foreign_ip foreign_mask
To use this command, replace port with the TCP port to which filtering is applied. Typically, this is port
80, but other values are accepted. The http or url literal can be used for port 80. You can specify a range
of ports by using a hyphen between the starting port number and the ending port number.
The local IP address and mask identify one or more internal hosts that are the source of the traffic to be
filtered. The foreign address and mask specify the external destination of the traffic to be filtered.
You can set either address to 0.0.0.0 (or in shortened form, 0) to specify all hosts. You can use 0.0.0.0
for either mask (or in shortened form, 0) to specify all hosts.
The following example specifies that ActiveX objects are blocked on all outbound connections:
hostname(config)# filter activex 80 0 0 0 0
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Filtering Java Applets
This command specifies that the ActiveX object blocking applies to web traffic on port 80 from any local
host and for connections to any foreign host.
To remove the configuration, use the no form of the command, as in the following example:
hostname(config)# no filter activex 80 0 0 0 0
Filtering Java Applets
This section describes how to apply filtering to remove Java applets from HTTP traffic passing through
the firewall. Java applets may pose security risks because they can contain code intended to attack hosts
and servers on a protected network. You can remove Java applets with the filter java command.
The filter java command filters out Java applets that return to the security appliance from an outbound
connection. The user still receives the HTML page, but the web page source for the applet is commented
out so that the applet cannot execute. The filter java command does not filter WebVPN traffic.
Note
Use the filter activex command to remove Java applets that are embedded in <object> tags.
To remove Java applets in HTTP traffic passing through the firewall, enter the following command in
global configuration mode:
hostname(config)# filter java
port[-port] local_ip local_mask foreign_ip foreign_mask
To use this command, replace port with the TCP port to which filtering is applied. Typically, this is port
80, but other values are accepted. The http or url literal can be used for port 80. You can specify a range
of ports by using a hyphen between the starting port number and the ending port number.
The local IP address and mask identify one or more internal hosts that are the source of the traffic to be
filtered. The foreign address and mask specify the external destination of the traffic to be filtered.
You can set either address to 0.0.0.0 (or in shortened form, 0) to specify all hosts. You can use 0.0.0.0
for either mask (or in shortened form, 0) to specify all hosts.
You can set either address to 0.0.0.0 (or in shortened form, 0) to specify all hosts. You can use 0.0.0.0
for either mask (or in shortened form, 0) to specify all hosts.
The following example specifies that Java applets are blocked on all outbound connections:
hostname(config)# filter java 80 0 0 0 0
This command specifies that the Java applet blocking applies to web traffic on port 80 from any local
host and for connections to any foreign host.
The following example blocks downloading of Java applets to a host on a protected network:
hostname(config)# filter java http 192.168.3.3 255.255.255.255 0 0
This command prevents host 192.168.3.3 from downloading Java applets.
To remove the configuration, use the no form of the command, as in the following example:
hostname(config)# no filter java http 192.168.3.3 255.255.255.255 0 0
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Filtering URLs and FTP Requests with an External Server
Filtering URLs and FTP Requests with an External Server
This section describes how to filter URLs and FTP requests with an external server. This section includes
the following topics:
•
URL Filtering Overview, page 20-4
•
Identifying the Filtering Server, page 20-4
•
Buffering the Content Server Response, page 20-6
•
Caching Server Addresses, page 20-6
•
Filtering HTTP URLs, page 20-7
•
Filtering HTTPS URLs, page 20-8
•
Filtering FTP Requests, page 20-9
URL Filtering Overview
You can apply filtering to connection requests originating from a more secure network to a less secure
network. Although you can use ACLs to prevent outbound access to specific content servers, managing
usage this way is difficult because of the size and dynamic nature of the Internet. You can simplify
configuration and improve security appliance performance by using a separate server running one of the
following Internet filtering products:
Note
•
Websense Enterprise for filtering HTTP, HTTPS, and FTP.
•
Secure Computing SmartFilter (formerly N2H2) for filtering HTTP, HTTPS, FTP, and long URL
filtering.
URL caching will only work if the version of the URL server software from the URL server vender
supports it.
Although security appliance performance is less affected when using an external server, users may notice
longer access times to websites or FTP servers when the filtering server is remote from the security
appliance.
When filtering is enabled and a request for content is directed through the security appliance, the request
is sent to the content server and to the filtering server at the same time. If the filtering server allows the
connection, the security appliance forwards the response from the content server to the originating client.
If the filtering server denies the connection, the security appliance drops the response and sends a
message or return code indicating that the connection was not successful.
If user authentication is enabled on the security appliance, then the security appliance also sends the user
name to the filtering server. The filtering server can use user-specific filtering settings or provide
enhanced reporting regarding usage.
Identifying the Filtering Server
You can identify up to four filtering servers per context. The security appliance uses the servers in order
until a server responds. You can only configure a single type of server (Websense or Secure Computing
SmartFilter ) in your configuration.
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Filtering URLs and FTP Requests with an External Server
Note
You must add the filtering server before you can configure filtering for HTTP or HTTPS with the filter
command. If you remove the filtering servers from the configuration, then all filter commands are also
removed.
Identify the address of the filtering server using the url-server command:
For Websense:
hostname(config)# url-server (if_name) host local_ip [timeout seconds] [protocol TCP | UDP
version [1|4] [connections num_conns] ]
For Secure Computing SmartFilter (formerly N2H2):
hostname(config)# url-server (if_name) vendor {secure-computing | n2h2} host
<local_ip> [port <number>] [timeout <seconds>] [protocol {TCP [connections <number>]} |
UDP]
where <if_name> is the name of the security appliance interface connected to the filtering server (the
default is inside).
For the vendor {secure-computing | n2h2}, you can use ‘secure-computing as a vendor string, however,
‘n2h2’ is acceptable for backward compatibility. When the configuration entries are generated,
‘secure-computing’ is saved as the vendor string.
The host <local_ip> is the IP address of the URL filtering server.
The port <number> is the Secure Computing SmartFilter server port number of the filtering server; the
security appliance also listens for UDP replies on this port.
Note
The default port is 4005. This is the default port used by the Secure Computing SmartFilter server to
communicate to the security appliance via TCP or UDP. For information on changing the default port,
please refer to the Filtering by N2H2 Administrator's Guide.
The timeout <seconds> is the number of seconds the security appliance should keep trying to connect
to the filtering server.
The connections <number> is the number of tries to attempt to make a connection between the host and
server.
For example, to identify a single Websense filtering server, enter the following command:
hostname(config)# url-server (perimeter) host 10.0.1.1 protocol TCP version 4
This identifies a Websense filtering server with the IP address 10.0.1.1 on a perimeter interface of the
security appliance.Version 4, which is enabled in this example, is recommended by Websense because it
supports caching.
To identify redundant Secure Computing SmartFilter servers, enter the following commands:
hostname(config)# url-server (perimeter) vendor n2h2 host 10.0.1.1
hostname(config)# url-server (perimeter) vendor n2h2 host 10.0.1.2
This identifies two Sentian filtering servers, both on a perimeter interface of the security appliance.
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Filtering URLs and FTP Requests with an External Server
Buffering the Content Server Response
When a user issues a request to connect to a content server, the security appliance sends the request to
the content server and to the filtering server at the same time. If the filtering server does not respond
before the content server, the server response is dropped. This delays the web server response from the
point of view of the web client because the client must reissue the request.
By enabling the HTTP response buffer, replies from web content servers are buffered and the responses
are forwarded to the requesting client if the filtering server allows the connection. This prevents the
delay that might otherwise occur.
To configure buffering for responses to HTTP or FTP requests, perform the following steps:
Step 1
To enable buffering of responses for HTTP or FTP requests that are pending a response from the filtering
server, enter the following command:
hostname(config)# url-block block block-buffer-limit
Replace block-buffer with the maximum number of HTTP responses that can be buffered while awaiting
responses from the url-server.
Note
Step 2
Buffering URLs longer than 3072 bytes are not supported.
To configure the maximum memory available for buffering pending URLs (and for buffering long
URLs), enter the following command:
hostname(config)# url-block mempool-size memory-pool-size
Replace memory-pool-size with a value from 2 to 10240 for a maximum memory allocation of 2 KB to
10 MB.
Caching Server Addresses
After a user accesses a site, the filtering server can allow the security appliance to cache the server
address for a certain amount of time, as long as every site hosted at the address is in a category that is
permitted at all times. Then, when the user accesses the server again, or if another user accesses the
server, the security appliance does not need to consult the filtering server again.
Note
Requests for cached IP addresses are not passed to the filtering server and are not logged. As a result,
this activity does not appear in any reports. You can accumulate Websense run logs before using the
url-cache command.
Use the url-cache command if needed to improve throughput, as follows:
hostname(config)# url-cache dst | src_dst size
Replace size with a value for the cache size within the range 1 to 128 (KB).
Use the dst keyword to cache entries based on the URL destination address. Select this mode if all users
share the same URL filtering policy on the Websense server.
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Use the src_dst keyword to cache entries based on both the source address initiating the URL request as
well as the URL destination address. Select this mode if users do not share the same URL filtering policy
on the Websense server.
Filtering HTTP URLs
This section describes how to configure HTTP filtering with an external filtering server. This section
includes the following topics:
•
Configuring HTTP Filtering, page 20-7
•
Enabling Filtering of Long HTTP URLs, page 20-7
•
Truncating Long HTTP URLs, page 20-7
•
Exempting Traffic from Filtering, page 20-8
Configuring HTTP Filtering
You must identify and enable the URL filtering server before enabling HTTP filtering.
When the filtering server approves an HTTP connection request, the security appliance allows the reply
from the web server to reach the originating client. If the filtering server denies the request, the security
appliance redirects the user to a block page, indicating that access was denied.
To enable HTTP filtering, enter the following command:
hostname(config)# filter url [http | port[-port] local_ip local_mask foreign_ip
foreign_mask] [allow] [proxy-block]
Replace port with one or more port numbers if a different port than the default port for HTTP (80) is
used. Replace local_ip and local_mask with the IP address and subnet mask of a user or subnetwork
making requests. Replace foreign_ip and foreign_mask with the IP address and subnet mask of a server
or subnetwork responding to requests.
The allow option causes the security appliance to forward HTTP traffic without filtering when the
primary filtering server is unavailable. Use the proxy-block command to drop all requests to proxy
servers.
Enabling Filtering of Long HTTP URLs
By default, the security appliance considers an HTTP URL to be a long URL if it is greater than 1159
characters. You can increase the maximum length allowed.
Configure the maximum size of a single URL with the following command:
hostname(config)# url-block url-size long-url-size
Replace long-url-size with the maximum size in KB for each long URL being buffered. For Websense,
this is a value from 2 to 4 for a maximum URL size of 2 KB to 4 KB; for Secure Computing, this is a
value between 2 to 3 for a maximum URL size of 2 KB to 3 KB. The default value is 2.
Truncating Long HTTP URLs
By default, if a URL exceeds the maximum permitted size, then it is dropped. To avoid this, you can set
the security appliance to truncate a long URL by entering the following command:
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hostname(config)# filter url [longurl-truncate | longurl-deny | cgi-truncate]
The longurl-truncate option causes the security appliance to send only the hostname or IP address
portion of the URL for evaluation to the filtering server when the URL is longer than the maximum
length permitted. Use the longurl-deny option to deny outbound URL traffic if the URL is longer than
the maximum permitted.
Use the cgi-truncate option to truncate CGI URLs to include only the CGI script location and the script
name without any parameters. Many long HTTP requests are CGI requests. If the parameters list is very
long, waiting and sending the complete CGI request including the parameter list can use up memory
resources and affect firewall performance.
Exempting Traffic from Filtering
To exempt specific traffic from filtering, enter the following command:
hostname(config)# filter url except source_ip source_mask dest_ip dest_mask
For example, the following commands cause all HTTP requests to be forwarded to the filtering server
except for those from 10.0.2.54.
hostname(config)# filter url http 0 0 0 0
hostname(config)# filter url except 10.0.2.54 255.255.255.255 0 0
Filtering HTTPS URLs
You must identify and enable the URL filtering server before enabling HTTPS filtering.
Note
Websense and Smartfilter currently support HTTPS; older versions of Secure Computing SmartFilter
(formerly N2H2) did not support HTTPS filtering.
Because HTTPS content is encrypted, the security appliance sends the URL lookup without directory
and filename information. When the filtering server approves an HTTPS connection request, the security
appliance allows the completion of SSL connection negotiation and allows the reply from the web server
to reach the originating client. If the filtering server denies the request, the security appliance prevents
the completion of SSL connection negotiation. The browser displays an error message such as “The Page
or the content cannot be displayed.”
Note
The security appliance does not provide an authentication prompt for HTTPS, so a user must
authenticate with the security appliance using HTTP or FTP before accessing HTTPS servers.
To enable HTTPS filtering, enter the following command:
hostname(config)# filter https port[-port] localIP local_mask foreign_IP foreign_mask
[allow]
Replace port[-port] with a range of port numbers if a different port than the default port for HTTPS (443)
is used.
Replace local_ip and local_mask with the IP address and subnet mask of a user or subnetwork making
requests.
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Replace foreign_ip and foreign_mask with the IP address and subnet mask of a server or subnetwork
responding to requests.
The allow option causes the security appliance to forward HTTPS traffic without filtering when the
primary filtering server is unavailable.
Filtering FTP Requests
You must identify and enable the URL filtering server before enabling FTP filtering.
Note
Websense and Smartfilter currently support FTP; older versions of Secure Computing SmartFilter
(formerly known as N2H2) did not support FTP filtering.
When the filtering server approves an FTP connection request, the security appliance allows the
successful FTP return code to reach originating client. For example, a successful return code is “250:
CWD command successful.” If the filtering server denies the request, alters the FTP return code to show
that the connection was denied. For example, the security appliance changes code 250 to “550 Requested
file is prohibited by URL filtering policy.”
To enable FTP filtering, enter the following command:
hostname(config)# filter ftp port[-port] localIP local_mask foreign_IP foreign_mask
[allow] [interact-block]
Replace port[-port] with a range of port numbers if a different port than the default port for FTP (21) is
used.
Replace local_ip and local_mask with the IP address and subnet mask of a user or subnetwork making
requests.
Replace foreign_ip and foreign_mask with the IP address and subnet mask of a server or subnetwork
responding to requests.
The allow option causes the security appliance to forward HTTPS traffic without filtering when the
primary filtering server is unavailable.
Use the interact-block option to prevent interactive FTP sessions that do not provide the entire directory
path. An interactive FTP client allows the user to change directories without typing the entire path. For
example, the user might enter cd ./files instead of cd /public/files.
Viewing Filtering Statistics and Configuration
This section describes how to monitor filtering statistics. This section includes the following topics:
•
Viewing Filtering Server Statistics, page 20-10
•
Viewing Buffer Configuration and Statistics, page 20-11
•
Viewing Caching Statistics, page 20-11
•
Viewing Filtering Performance Statistics, page 20-11
•
Viewing Filtering Configuration, page 20-12
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Viewing Filtering Server Statistics
To show information about the filtering server, enter the following command:
hostname# show running-config url-server
The following is sample output from the show running-config url-server command:
hostname# show running-config url-server
url-server (outside) vendor n2h2 host 128.107.254.202 port 4005 timeout 5 protocol TCP
To show information about the filtering server or to show statistics, enter the following command:
The following is sample output from the show running-config url-server statistics command, which
shows filtering statistics:
hostname# show running-config url-server statistics
Global Statistics:
-------------------URLs total/allowed/denied
URLs allowed by cache/server
URLs denied by cache/server
HTTPSs total/allowed/denied
HTTPSs allowed by cache/server
HTTPSs denied by cache/server
FTPs total/allowed/denied
FTPs allowed by cache/server
FTPs denied by cache/server
Requests dropped
Server timeouts/retries
Processed rate average 60s/300s
Denied rate average 60s/300s
Dropped rate average 60s/300s
13/3/10
0/3
0/10
138/137/1
0/137
0/1
0/0/0
0/0
0/0
0
0/0
0/0 requests/second
0/0 requests/second
0/0 requests/second
Server Statistics:
-------------------10.125.76.20
Vendor
Port
Requests total/allowed/denied
Server timeouts/retries
Responses received
Response time average 60s/300s
UP
websense
15868
151/140/11
0/0
151
0/0
URL Packets Sent and Received Stats:
-----------------------------------Message
Sent
Received
STATUS_REQUEST
1609
1601
LOOKUP_REQUEST
1526
1526
LOG_REQUEST
0
NA
Errors:
------RFC noncompliant GET method
URL buffer update failure
0
0
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Applying Filtering Services
Viewing Filtering Statistics and Configuration
Viewing Buffer Configuration and Statistics
The show running-config url-block command displays the number of packets held in the url-block
buffer and the number (if any) dropped due to exceeding the buffer limit or retransmission.
The following is sample output from the show running-config url-block command:
hostname# show running-config url-block
url-block url-mempool 128
url-block url-size 4
url-block block 128
This shows the configuration of the URL block buffer.
The following is sample output from the show url-block block statistics command:
hostname# show running-config url-block block statistics
URL Pending Packet Buffer Stats with max block 128
----------------------------------------------------Cumulative number of packets held:
896
Maximum number of packets held (per URL):
3
Current number of packets held (global):
38
Packets dropped due to
exceeding url-block buffer limit:
7546
HTTP server retransmission:
10
Number of packets released back to client:
0
This shows the URL block statistics.
Viewing Caching Statistics
The following is sample output from the show url-cache stats command:
hostname# show url-cache stats
URL Filter Cache Stats
---------------------Size :
128KB
Entries :
1724
In Use :
456
Lookups :
45
Hits :
8
This shows how the cache is used.
Viewing Filtering Performance Statistics
The following is sample output from the show perfmon command:
hostname# show perfmon
PERFMON STATS:
Current
Xlates
0/s
Connections
0/s
TCP Conns
0/s
UDP Conns
0/s
URL Access
0/s
URL Server Req
0/s
TCP Fixup
0/s
TCPIntercept
0/s
HTTP Fixup
0/s
Average
0/s
2/s
2/s
0/s
2/s
3/s
0/s
0/s
3/s
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FTP
AAA
AAA
AAA
Fixup
Authen
Author
Account
0/s
0/s
0/s
0/s
0/s
0/s
0/s
0/s
This shows URL filtering performance statistics, along with other performance statistics. The filtering
statistics are shown in the URL Access and URL Server Req rows.
Viewing Filtering Configuration
The following is sample output from the show running-config filter command:
hostname# show running-config filter
filter url http 0.0.0.0 0.0.0.0 0.0.0.0 0.0.0.0
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21
Using Modular Policy Framework
This chapter describes how to use Modular Policy Framework to create security policies for TCP and
general connection settings, inspections, IPS, CSC, and QoS.
This chapter includes the following sections:
•
Modular Policy Framework Overview, page 21-1
•
Identifying Traffic (Layer 3/4 Class Map), page 21-4
•
Configuring Special Actions for Application Inspections (Inspection Policy Map), page 21-7
•
Defining Actions (Layer 3/4 Policy Map), page 21-15
•
Applying Actions to an Interface (Service Policy), page 21-21
•
Modular Policy Framework Examples, page 21-21
Modular Policy Framework Overview
Modular Policy Framework provides a consistent and flexible way to configure security appliance
features. For example, you can use Modular Policy Framework to create a timeout configuration that is
specific to a particular TCP application, as opposed to one that applies to all TCP applications. This
section includes the following topics:
•
Modular Policy Framework Features, page 21-1
•
Modular Policy Framework Configuration Overview, page 21-2
•
Default Global Policy, page 21-3
Modular Policy Framework Features
Modular Policy Framework supports the following features:
•
QoS input policing
•
TCP normalization, TCP and UDP connection limits and timeouts, and TCP sequence number
randomization
•
CSC
•
Application inspection
•
IPS
•
QoS output policing
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Modular Policy Framework Overview
•
QoS standard priority queue
•
QoS traffic shaping, hierarchical priority queue
Modular Policy Framework Configuration Overview
Configuring Modular Policy Framework consists of the following tasks:
1.
Identify the traffic on which you want to perform Modular Policy Framework actions by creating
Layer 3/4 class maps. For example, you might want to perform actions on all traffic that passes
through the security appliance; or you might only want to perform certain actions on traffic from
10.1.1.0/24 to any destination address..
Layer 3/4 Class Map
241506
Layer 3/4 Class Map
See the “Identifying Traffic (Layer 3/4 Class Map)” section on page 21-4.
2.
If one of the actions you want to perform is application inspection, and you want to perform
additional actions on some inspection traffic, then create an inspection policy map. The inspection
policy map identifies the traffic and specifies what to do with it. For example, you might want to
drop all HTTP requests with a body length greater than 1000 bytes.
Inspection Policy Map Actions
241507
Inspection Class Map/
Match Commands
You can create a self-contained inspection policy map that identifies the traffic directly with match
commands, or you can create an inspection class map for reuse or for more complicated matching.
See the “Defining Actions in an Inspection Policy Map” section on page 21-8 and the “Identifying
Traffic in an Inspection Class Map” section on page 21-11.
3.
If you want to match text with a regular expression within inspected packets, you can create a regular
expression or a group of regular expressions (a regular expression class map). Then, when you
define the traffic to match for the inspection policy map, you can call on an existing regular
expression. For example, you might want to drop all HTTP requests with a URL including the text
“example.com.”
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Modular Policy Framework Overview
Inspection Policy Map Actions
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Inspection Class Map/
Match Commands
Regular Expression Statement/
Regular Expression Class Map
See the “Creating a Regular Expression” section on page 21-12 and the “Creating a Regular
Expression Class Map” section on page 21-14.
4.
Define the actions you want to perform on each Layer 3/4 class map by creating a Layer 3/4 policy
map. Then, determine on which interfaces you want to apply the policy map using a service policy.
Layer 3/4 Policy Map
Connection Limits
Connection Limits
Service Policy
Inspection
Inspection
241508
IPS
See the “Defining Actions (Layer 3/4 Policy Map)” section on page 21-15 and the “Applying
Actions to an Interface (Service Policy)” section on page 21-21.
Default Global Policy
By default, the configuration includes a policy that matches all default application inspection traffic and
applies certain inspections to the traffic on all interfaces (a global policy). Not all inspections are enabled
by default. You can only apply one global policy, so if you want to alter the global policy, you need to
either edit the default policy or disable it and apply a new one. (An interface policy overrides the global
policy for a particular feature.)
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Identifying Traffic (Layer 3/4 Class Map)
The default policy configuration includes the following commands:
class-map inspection_default
match default-inspection-traffic
policy-map type inspect dns preset_dns_map
parameters
message-length maximum 512
policy-map global_policy
class inspection_default
inspect dns preset_dns_map
inspect ftp
inspect h323 h225
inspect h323 ras
inspect rsh
inspect rtsp
inspect esmtp
inspect sqlnet
inspect skinny
inspect sunrpc
inspect xdmcp
inspect sip
inspect netbios
inspect tftp
service-policy global_policy global
Identifying Traffic (Layer 3/4 Class Map)
A Layer 3/4 class map identifies Layer 3 and 4 traffic to which you want to apply actions. The maximum
number of Layer 3/4 class maps is 255 in single mode or per context in multiple mode.You can create
multiple Layer 3/4 class maps for each Layer 3/4 policy map. You can create the following types of class
maps:
•
Default Class Maps, page 21-4
•
Creating a Layer 3/4 Class Map for Through Traffic, page 21-5
•
Creating a Layer 3/4 Class Map for Management Traffic, page 21-7
Default Class Maps
The configuration includes a default Layer 3/4 class map that the security appliance uses in the default
global policy. It is called inspection_default and matches the default inspection traffic:
class-map inspection_default
match default-inspection-traffic
Another class map that exists in the default configuration is called class-default, and it matches all
traffic:
class-map class-default
match any
This class map appears at the end of all Layer 3/4 policy maps and essentially tells the security appliance
to not perform any actions on all other traffic. You can use the class-default class map if desired, rather
than making your own match any class map. In fact, some features are only available for class-default,
such as QoS traffic shaping.
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Identifying Traffic (Layer 3/4 Class Map)
Creating a Layer 3/4 Class Map for Through Traffic
A Layer 3/4 class map matches traffic based on protocols, ports, IP addresses and other Layer 3 or 4
attributes.
To define a Layer 3/4 class map, perform the following steps:
Step 1
Create a Layer 3/4 class map by entering the following command:
hostname(config)# class-map class_map_name
hostname(config-cmap)#
Where class_map_name is a string up to 40 characters in length. The name “class-default” is reserved.
All types of class maps use the same name space, so you cannot reuse a name already used by another
type of class map. The CLI enters class-map configuration mode.
Step 2
(Optional) Add a description to the class map by entering the following command:
hostname(config-cmap)# description string
Step 3
Define the traffic to include in the class by matching one of the following characteristics. Unless
otherwise specified, you can include only one match command in the class map.
•
Any traffic—The class map matches all traffic.
hostname(config-cmap)# match any
•
Access list—The class map matches traffic specified by an extended access list. If the security
appliance is operating in transparent firewall mode, you can use an EtherType access list.
hostname(config-cmap)# match access-list access_list_name
For more information about creating access lists, see the “Adding an Extended Access List” section
on page 16-5 or the “Adding an EtherType Access List” section on page 16-8.
For information about creating access lists with NAT, see the “IP Addresses Used for Access Lists
When You Use NAT” section on page 16-3.
•
TCP or UDP destination ports—The class map matches a single port or a contiguous range of ports.
hostname(config-cmap)# match port {tcp | udp} {eq port_num | range port_num port_num}
Tip
For applications that use multiple, non-contiguous ports, use the match access-list command
and define an ACE to match each port.
For a list of ports you can specify, see the “TCP and UDP Ports” section on page D-11.
For example, enter the following command to match TCP packets on port 80 (HTTP):
hostname(config-cmap)# match tcp eq 80
•
Default traffic for inspection—The class map matches the default TCP and UDP ports used by all
applications that the security appliance can inspect.
hostname(config-cmap)# match default-inspection-traffic
See the “Default Inspection Policy” section on page 25-3 for a list of default ports. The security
appliance includes a default global policy that matches the default inspection traffic, and applies
common inspections to the traffic on all interfaces. Not all applications whose ports are included in
the match default-inspection-traffic command are enabled by default in the policy map.
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Identifying Traffic (Layer 3/4 Class Map)
You can specify a match access-list command along with the match default-inspection-traffic
command to narrow the matched traffic. Because the match default-inspection-traffic command
specifies the ports to match, any ports in the access list are ignored.
•
DSCP value in an IP header—The class map matches up to eight DSCP values.
hostname(config-cmap)# match dscp value1 [value2] [...] [value8]
For example, enter the following:
hostname(config-cmap)# match dscp af43 cs1 ef
•
Precedence—The class map matches up to four precedence values, represented by the Type of
Service (TOS) byte in the IP header.
hostname(config-cmap)# match precedence value1 [value2] [value3] [value4]
where value1 through value4 can be 0 to 7, corresponding to the possible precedences.
•
RTP traffic—The class map matches RTP traffic.
hostname(config-cmap)# match rtp starting_port range
The starting_port specifies an even-numbered UDP destination port between 2000 and 65534. The
range specifies the number of additional UDP ports to match above the starting_port, between 0 and
16383.
•
Tunnel group traffic—The class map matches traffic for a tunnel group to which you want to apply
QoS.
hostname(config-cmap)# match tunnel-group name
You can also specify one other match command to refine the traffic match. You can specify any of
the preceding commands, except for the match any, match access-list, or match
default-inspection-traffic commands. Or you can enter the following command to police each
flow:
hostname(config-cmap)# match flow ip destination address
All traffic going to a unique IP destination address is considered a flow.
The following is an example for the class-map command:
hostname(config)# access-list udp permit udp any any
hostname(config)# access-list tcp permit tcp any any
hostname(config)# access-list host_foo permit ip any 10.1.1.1 255.255.255.255
hostname(config)# class-map all_udp
hostname(config-cmap)# description "This class-map matches all UDP traffic"
hostname(config-cmap)# match access-list udp
hostname(config-cmap)# class-map all_tcp
hostname(config-cmap)# description "This class-map matches all TCP traffic"
hostname(config-cmap)# match access-list tcp
hostname(config-cmap)# class-map all_http
hostname(config-cmap)# description "This class-map matches all HTTP traffic"
hostname(config-cmap)# match port tcp eq http
hostname(config-cmap)# class-map to_server
hostname(config-cmap)# description "This class-map matches all traffic to server 10.1.1.1"
hostname(config-cmap)# match access-list host_foo
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Creating a Layer 3/4 Class Map for Management Traffic
For management traffic to the security appliance, you might want to perform actions specific to this kind
of traffic. You can specify a management class map that can match TCP or UDP ports. The types of
actions available for a management class map in the policy map are specialized for management traffic.
Namely, this type of class map lets you inspect RADIUS accounting traffic.
To create a class map for management traffic to the security appliance, perform the following steps:
Step 1
Create a class map by entering the following command:
hostname(config)# class-map type management class_map_name
hostname(config-cmap)#
Where class_map_name is a string up to 40 characters in length. The name “class-default” is reserved.
All types of class maps use the same name space, so you cannot reuse a name already used by another
type of class map. The CLI enters class-map configuration mode.
Step 2
(Optional) Add a description to the class map by entering the following command:
hostname(config-cmap)# description string
Step 3
Define the traffic to include in the class by matching the TCP or UDP port. You can include only one
match command in the class map.
hostname(config-cmap)# match port {tcp | udp} {eq port_num | range port_num port_num}
For a list of ports you can specify, see the “TCP and UDP Ports” section on page D-11.
For example, enter the following command to match TCP packets on port 10000:
hostname(config-cmap)# match tcp eq 10000
Configuring Special Actions for Application Inspections
(Inspection Policy Map)
Modular Policy Framework lets you configure special actions for many application inspections. When
you enable an inspection engine in the Layer 3/4 policy map, you can also optionally enable actions as
defined in an inspection policy map. When the inspection policy map matches traffic within the Layer
3/4 class map for which you have defined an inspection action, then that subset of traffic will be acted
upon as specified (for example, dropped or rate-limited).
This section includes the following topics:
•
Inspection Policy Map Overview, page 21-8
•
Defining Actions in an Inspection Policy Map, page 21-8
•
Identifying Traffic in an Inspection Class Map, page 21-11
•
Creating a Regular Expression, page 21-12
•
Creating a Regular Expression Class Map, page 21-14
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Inspection Policy Map Overview
See the “Configuring Application Inspection” section on page 25-5 for a list of applications that support
inspection policy maps.
An inspection policy map consists of one or more of the following elements. The exact options available
for an inspection policy map depends on the application.
•
Traffic matching command—You can define a traffic matching command directly in the inspection
policy map to match application traffic to criteria specific to the application, such as a URL string,
for which you then enable actions.
– Some traffic matching commands can specify regular expressions to match text inside a packet.
Be sure to create and test the regular expressions before you configure the policy map, either
singly or grouped together in a regular expression class map.
•
Inspection class map—(Not available for all applications. See the CLI help for a list of supported
applications.) An inspection class map includes traffic matching commands that match application
traffic with criteria specific to the application, such as a URL string. You then identify the class map
in the policy map and enable actions. The difference between creating a class map and defining the
traffic match directly in the inspection policy map is that you can create more complex match criteria
and you can reuse class maps.
– Some traffic matching commands can specify regular expressions to match text inside a packet.
Be sure to create and test the regular expressions before you configure the policy map, either
singly or grouped together in a regular expression class map.
•
Parameters—Parameters affect the behavior of the inspection engine.
The default inspection policy map configuration includes the following commands, which sets the
maximum message length for DNS packets to be 512 bytes:
policy-map type inspect dns preset_dns_map
parameters
message-length maximum 512
Note
There are other default inspection policy maps such as policy-map type inspect esmtp
_default_esmtp_map. These default policy maps are created implicitly by the command inspect
protocol. For example, inspect esmtp implicitly uses the policy map “_default_esmtp_map.” All the
default policy maps can be shown by using the show running-config all policy-map command.
Defining Actions in an Inspection Policy Map
When you enable an inspection engine in the Layer 3/4 policy map, you can also optionally enable
actions as defined in an inspection policy map.
To create an inspection policy map, perform the following steps:
Step 1
To create the HTTP inspection policy map, enter the following command:
hostname(config)# policy-map type inspect application policy_map_name
hostname(config-pmap)#
See the “Configuring Application Inspection” section on page 25-5 for a list of applications that support
inspection policy maps.
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The policy_map_name argument is the name of the policy map up to 40 characters in length. All types
of policy maps use the same name space, so you cannot reuse a name already used by another type of
policy map. The CLI enters policy-map configuration mode.
Step 2
To apply actions to matching traffic, perform the following steps:
a.
Specify the traffic on which you want to perform actions using one of the following methods:
•
Specify the inspection class map that you created in the “Identifying Traffic in an Inspection
Class Map” section on page 21-11 by entering the following command:
hostname(config-pmap)# class class_map_name
hostname(config-pmap-c)#
•
b.
Specify traffic directly in the policy map using one of the match commands described for each
application in Chapter 25, “Configuring Application Layer Protocol Inspection.” If you use a
match not command, then any traffic that matches the criterion in the match not command does
not have the action applied.
Specify the action you want to perform on the matching traffic by entering the following command:
hostname(config-pmap-c)# {[drop [send-protocol-error] |
drop-connection [send-protocol-error]| mask | reset] [log] | rate-limit message_rate}
Not all options are available for each application. Other actions specific to the application might also
be available. See Chapter 25, “Configuring Application Layer Protocol Inspection,” for the exact
options available.
The drop keyword drops all packets that match.
The send-protocol-error keyword sends a protocol error message.
The drop-connection keyword drops the packet and closes the connection.
The mask keyword masks out the matching portion of the packet.
The reset keyword drops the packet, closes the connection, and sends a TCP reset to the server
and/or client.
The log keyword, which you can use alone or with one of the other keywords, sends a system log
message.
The rate-limit message_rate argument limits the rate of messages.
Note
You can specify multiple class or match commands in the policy map.
If a packet matches multiple different match or class commands, then the order in which the security
appliance applies the actions is determined by internal security appliance rules, and not by the order they
are added to the policy map. The internal rules are determined by the application type and the logical
progression of parsing a packet, and are not user-configurable. For example for HTTP traffic, parsing a
Request Method field precedes parsing the Header Host Length field; an action for the Request Method
field occurs before the action for the Header Host Length field. For example, the following match
commands can be entered in any order, but the match request method get command is matched first.
match request header host length gt 100
reset
match request method get
log
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If an action drops a packet, then no further actions are performed in the inspection policy map. For
example, if the first action is to reset the connection, then it will never match any further match or class
commands. If the first action is to log the packet, then a second action, such as resetting the connection,
can occur. (You can configure both the reset (or drop-connection, and so on.) and the log action for the
same match or class command, in which case the packet is logged before it is reset for a given match.)
If a packet matches multiple match or class commands that are the same, then they are matched in the
order they appear in the policy map. For example, for a packet with the header length of 1001, it will
match the first command below, and be logged, and then will match the second command and be reset.
If you reverse the order of the two match commands, then the packet will be dropped and the connection
reset before it can match the second match command; it will never be logged.
match request header length gt 100
log
match request header length gt 1000
reset
A class map is determined to be the same type as another class map or match command based on the
lowest priority match command in the class map (the priority is based on the internal rules). If a class
map has the same type of lowest priority match command as another class map, then the class maps are
matched according to the order they are added to the policy map. If the lowest priority command for each
class map is different, then the class map with the higher priority match command is matched first. For
example, the following three class maps contain two types of match commands: match request-cmd
(higher priority) and match filename (lower priority). The ftp3 class map includes both commands, but
it is ranked according to the lowest priority command, match filename. The ftp1 class map includes the
highest priority command, so it is matched first, regardless of the order in the policy map. The ftp3 class
map is ranked as being of the same priority as the ftp2 class map, which also contains the match
filename command. They are matched according to the order in the policy map: ftp3 and then ftp2.
class-map inspect type ftp ftp1
match request-cmd get
class-map inspect type ftp ftp2
match filename regex abc
class-map inspect type ftp ftp3
match request-cmd get
match filename regex abc
policy-map type inspect ftp ftp
class ftp3
log
class ftp2
log
class ftp1
log
Step 3
To configure parameters that affect the inspection engine, enter the following command:
hostname(config-pmap)# parameters
hostname(config-pmap-p)#
The CLI enters parameters configuration mode. For the parameters available for each application, see
Chapter 25, “Configuring Application Layer Protocol Inspection.”
The following is an example of an HTTP inspection policy map and the related class maps. This policy
map is activated by the Layer 3/4 policy map, which is enabled by the service policy.
hostname(config)# regex url_example example.com
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hostname(config)# regex url_example2 example2.com
hostname(config)# class-map type regex match-any URLs
hostname(config-cmap)# match regex url_example
hostname(config-cmap)# match regex url_example2
hostname(config-cmap)#
hostname(config-cmap)#
hostname(config-cmap)#
hostname(config-cmap)#
class-map type inspect http match-all http-traffic
match req-resp content-type mismatch
match request body length gt 1000
match not request uri regex class URLs
hostname(config-cmap)# policy-map type inspect http http-map1
hostname(config-pmap)# class http-traffic
hostname(config-pmap-c)# drop-connection log
hostname(config-pmap-c)# match req-resp content-type mismatch
hostname(config-pmap-c)# reset log
hostname(config-pmap-c)# parameters
hostname(config-pmap-p)# protocol-violation action log
hostname(config-pmap-p)# policy-map test
hostname(config-pmap)# class test (a Layer 3/4 class
hostname(config-pmap-c)# inspect http http-map1
map not shown)
hostname(config-pmap-c)# service-policy test interface outside
Identifying Traffic in an Inspection Class Map
This type of class map allows you to match criteria that is specific to an application. For example, for
DNS traffic, you can match the domain name in a DNS query.
Note
Not all applications support inspection class maps. See the CLI help for a list of supported applications.
A class map groups multiple traffic matches. Traffic must match all of the match criteria to match the
class map. You can alternatively identify the traffic you want to match directly in the policy map. The
difference between creating a class map and defining the traffic match directly in the inspection policy
map is that the class map lets you group multiple matches, and you can reuse class maps. For the traffic
that you identify in this class map, you can specify actions such as dropping, resetting, and/or logging
the connection in the inspection policy map. If you want to perform different actions on different types
of traffic, you should identify the traffic directly in the policy map.
To define an inspection class map, perform the following steps:
Step 1
Create a class map by entering the following command:
hostname(config)# class-map type inspect application [match-all] class_map_name
hostname(config-cmap)#
Where the application is the application you want to inspect. For supported applications, see Chapter 25,
“Configuring Application Layer Protocol Inspection.”
The class_map_name argument is the name of the class map up to 40 characters in length.
The match-all keyword is the default, and specifies that traffic must match all criteria to match the class
map.
The CLI enters class-map configuration mode, where you can enter one or more match commands.
Step 2
(Optional) To add a description to the class map, enter the following command:
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hostname(config-cmap)# description string
Step 3
Define the traffic to include in the class by entering one or more match commands available for your
application.
To specify traffic that should not match the class map, use the match not command. For example, if the
match not command specifies the string “example.com,” then any traffic that includes “example.com”
does not match the class map.
To see the match commands available for each application, see Chapter 25, “Configuring Application
Layer Protocol Inspection.”
The following example creates an HTTP class map that must match all criteria:
hostname(config-cmap)#
hostname(config-cmap)#
hostname(config-cmap)#
hostname(config-cmap)#
class-map type inspect http match-all http-traffic
match req-resp content-type mismatch
match request body length gt 1000
match not request uri regex class URLs
Creating a Regular Expression
A regular expression matches text strings either literally as an exact string, or by using metacharacters
so you can match multiple variants of a text string. You can use a regular expression to match the content
of certain application traffic; for example, you can match a URL string inside an HTTP packet.
Use Ctrl+V to escape all of the special characters in the CLI, such as question mark (?) or a tab. For
example, type d[Ctrl+V]g to enter d?g in the configuration.
See the regex command in the Cisco Security Appliance Command Reference for performance impact
information when matching a regular expression to packets.
Note
As an optimization, the security appliance searches on the deobfuscated URL. Deobfuscation
compresses multiple forward slashes (/) into a single slash. For strings that commonly use double
slashes, like “http://”, be sure to search for “http:/” instead.
Table 21-1 lists the metacharacters that have special meanings.
Table 21-1
regex Metacharacters
Character Description
Notes
.
Dot
Matches any single character. For example, d.g matches
dog, dag, dtg, and any word that contains those
characters, such as doggonnit.
(exp)
Subexpression
A subexpression segregates characters from surrounding
characters, so that you can use other metacharacters on
the subexpression. For example, d(o|a)g matches dog
and dag, but do|ag matches do and ag. A subexpression
can also be used with repeat quantifiers to differentiate
the characters meant for repetition. For example,
ab(xy){3}z matches abxyxyxyz.
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Table 21-1
regex Metacharacters (continued)
Character Description
Notes
|
Alternation
Matches either expression it separates. For example,
dog|cat matches dog or cat.
?
Question mark
A quantifier that indicates that there are 0 or 1 of the
previous expression. For example, lo?se matches lse or
lose.
Note
You must enter Ctrl+V and then the question
mark or else the help function is invoked.
*
Asterisk
A quantifier that indicates that there are 0, 1 or any
number of the previous expression. For example, lo*se
matches lse, lose, loose, and so on.
+
Plus
A quantifier that indicates that there is at least 1 of the
previous expression. For example, lo+se matches lose
and loose, but not lse.
{x}
Repeat quantifier
Repeat exactly x times. For example, ab(xy){3}z
matches abxyxyxyz.
{x,}
Minimum repeat quantifier
Repeat at least x times. For example, ab(xy){2,}z
matches abxyxyz, abxyxyxyz, and so on.
[abc]
Character class
Matches any character in the brackets. For example,
[abc] matches a, b, or c.
[^abc]
Negated character class
Matches a single character that is not contained within
the brackets. For example, [^abc] matches any character
other than a, b, or c. [^A-Z] matches any single
character that is not an uppercase letter.
[a-c]
Character range class
Matches any character in the range. [a-z] matches any
lowercase letter. You can mix characters and ranges:
[abcq-z] matches a, b, c, q, r, s, t, u, v, w, x, y, z, and so
does [a-cq-z].
The dash (-) character is literal only if it is the last or the
first character within the brackets: [abc-] or [-abc].
""
Quotation marks
Preserves trailing or leading spaces in the string. For
example, " test" preserves the leading space when it
looks for a match.
^
Caret
Specifies the beginning of a line.
\
Escape character
When used with a metacharacter, matches a literal
character. For example, \[ matches the left square
bracket.
char
Character
When character is not a metacharacter, matches the
literal character.
\r
Carriage return
Matches a carriage return 0x0d.
\n
Newline
Matches a new line 0x0a.
\t
Tab
Matches a tab 0x09.
\f
Formfeed
Matches a form feed 0x0c.
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Table 21-1
regex Metacharacters (continued)
Character Description
Notes
\xNN
Escaped hexadecimal number
Matches an ASCII character using hexadecimal (exactly
two digits).
\NNN
Escaped octal number
Matches an ASCII character as octal (exactly three
digits). For example, the character 040 represents a
space.
To test and create a regular expression, perform the following steps:
Step 1
To test a regular expression to make sure it matches what you think it will match, enter the following
command:
hostname(config)# test regex input_text regular_expression
Where the input_text argument is a string you want to match using the regular expression, up to 201
characters in length.
The regular_expression argument can be up to 100 characters in length.
Use Ctrl+V to escape all of the special characters in the CLI. For example, to enter a tab in the input
text in the test regex command, you must enter test regex "test[Ctrl+V Tab]" "test\t".
If the regular expression matches the input text, you see the following message:
INFO: Regular expression match succeeded.
If the regular expression does not match the input text, you see the following message:
INFO: Regular expression match failed.
Step 2
To add a regular expression after you tested it, enter the following command:
hostname(config)# regex name regular_expression
Where the name argument can be up to 40 characters in length.
The regular_expression argument can be up to 100 characters in length.
The following example creates two regular expressions for use in an inspection policy map:
hostname(config)# regex url_example example\.com
hostname(config)# regex url_example2 example2\.com
Creating a Regular Expression Class Map
A regular expression class map identifies one or more regular expressions. You can use a regular
expression class map to match the content of certain traffic; for example, you can match URL strings
inside HTTP packets.
To create a regular expression class map, perform the following steps:
Step 1
Create one or more regular expressions according to the “Creating a Regular Expression” section.
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Step 2
Create a class map by entering the following command:
hostname(config)# class-map type regex match-any class_map_name
hostname(config-cmap)#
Where class_map_name is a string up to 40 characters in length. The name “class-default” is reserved.
All types of class maps use the same name space, so you cannot reuse a name already used by another
type of class map.
The match-any keyword specifies that the traffic matches the class map if it matches only one of the
regular expressions.
The CLI enters class-map configuration mode.
Step 3
(Optional) Add a description to the class map by entering the following command:
hostname(config-cmap)# description string
Step 4
Identify the regular expressions you want to include by entering the following command for each regular
expression:
hostname(config-cmap)# match regex regex_name
The following example creates two regular expressions, and adds them to a regular expression class map.
Traffic matches the class map if it includes the string “example.com” or “example2.com.”
hostname(config)# regex url_example example\.com
hostname(config)# regex url_example2 example2\.com
hostname(config)# class-map type regex match-any URLs
hostname(config-cmap)# match regex url_example
hostname(config-cmap)# match regex url_example2
Defining Actions (Layer 3/4 Policy Map)
This section describes how to associate actions with Layer 3/4 class maps by creating a Layer 3/4 policy
map. This section includes the following topics:
•
Layer 3/4 Policy Map Overview, page 21-15
•
Default Layer 3/4 Policy Map, page 21-18
•
Adding a Layer 3/4 Policy Map, page 21-19
Layer 3/4 Policy Map Overview
This section describes how Layer 3/4 policy maps work, and includes the following topics:
•
Policy Map Guidelines, page 21-16
•
Supported Feature Types, page 21-16
•
Hierarchical Policy Maps, page 21-16
•
Feature Directionality, page 21-17
•
Feature Matching Guidelines within a Policy Map, page 21-17
•
Feature Matching Guidelines for multiple Policy Maps, page 21-18
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•
Order in Which Multiple Feature Actions are Applied, page 21-18
Policy Map Guidelines
See the following guidelines for using policy maps:
•
You can only assign one policy map per interface.
•
You can apply the same policy map to multiple interfaces.
•
You can identify multiple Layer 3/4 class maps in a Layer 3/4 policy map.
•
For each class map, you can assign multiple actions from one or more feature types.
•
You can create a hierarchical policy map. See the “Hierarchical Policy Maps” section on page 21-16.
Supported Feature Types
Feature types supported by the Modular Policy Framework that you can enable in the policy map include
the following:
•
QoS input policing
•
TCP normalization, TCP and UDP connection limits and timeouts, and TCP sequence number
randomization
•
CSC
•
Application inspection
•
IPS
•
QoS output policing
•
QoS standard priority queue
•
QoS traffic shaping, hierarchical priority queue
Hierarchical Policy Maps
If you enable QoS traffic shaping for a class map, then you can optionally enable priority queueing for
a subset of shaped traffic. To do so, you need to create a policy map for the priority queueing, and then
within the traffic shaping policy map, you can call the priority class map. Only the traffic shaping class
map is applied to an interface.
See Chapter 24, “Configuring QoS,” for more information about this feature.
Hierarchical policy maps are only supported for traffic shaping and priority queueing.
To implement a hierarchical policy map, perform the following tasks:
1.
Identify the prioritized traffic according to the “Identifying Traffic (Layer 3/4 Class Map)” section
on page 21-4.
You can create multiple class maps to be used in the hierarchical policy map.
2.
Create a policy map according to the “Defining Actions (Layer 3/4 Policy Map)” section on
page 21-15, and identify the sole action for each class map as priority.
3.
Create a separate policy map according to the “Defining Actions (Layer 3/4 Policy Map)” section
on page 21-15, and identify the shape action for the class-default class map.
Traffic shaping can only be applied the to class-default class map.
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4.
For the same class map, identify the priority policy map that you created in Step 2 using the
service-policy priority_policy_map command.
5.
Apply the shaping policy map to the interface accrding to “Applying Actions to an Interface (Service
Policy)” section on page 21-21.
Feature Directionality
Actions are applied to traffic bidirectionally or unidirectionally depending on the feature. For features
that are applied bidirectionally, all traffic that enters or exits the interface to which you apply the policy
map is affected if the traffic matches the class map for both directions.
Note
When you use a global policy, all features are unidirectional; features that are normally bidirectional
when applied to a single interface only apply to the ingress of each interface when applied globally.
Because the policy is applied to all interfaces, the policy will be applied in both directions so
bidirectionality in this case is redundant.
For features that are applied unidirectionally, for example QoS priority queue, only traffic that exits the
interface to which you apply the policy map is affected. See Table 21-2 for the directionality of each
feature.
Table 21-2
Feature Directionality
Feature
Single Interface Direction Global Direction
TCP normalization, TCP and UDP connection Bidirectional
limits and timeouts, and TCP sequence number
randomization
Ingress
CSC
Bidirectional
Ingress
Application inspection
Bidirectional
Ingress
IPS
Bidirectional
Ingress
QoS input policing
Ingress
Ingress
QoS output policing
Egress
Egress
QoS standard priority queue
Egress
Egress
QoS traffic shaping, hierarchical priority
queue
Egress
Egress
Feature Matching Guidelines within a Policy Map
See the following guidelines for how a packet matches class maps in a policy map:
•
A packet can match only one class map in the policy map for each feature type.
•
When the packet matches a class map for a feature type, the security appliance does not attempt to
match it to any subsequent class maps for that feature type.
•
If the packet matches a subsequent class map for a different feature type, however, then the security
appliance also applies the actions for the subsequent class map.
For example, if a packet matches a class map for connection limits, and also matches a class map for
application inspection, then both class map actions are applied.
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If a packet matches a class map for application inspection, but also matches another class map that
includes application inspection, then the second class map actions are not applied.
Feature Matching Guidelines for multiple Policy Maps
For TCP and UDP traffic (and ICMP when you enable stateful ICMP inspection), Modular Policy
Framework operates on traffic flows, and not just individual packets. If traffic is part of an existing
connection that matches a feature in a policy on one interface, that traffic flow cannot also match the
same feature in a policy on another interface; only the first policy is used.
For example, if HTTP traffic matches a policy on the inside interface to inspect HTTP traffic, and you
have a separate policy on the outside interface for HTTP inspection, then that traffic is not also inspected
on the egress of the outside interface. Similarly, the return traffic for that connection will not be
inspected by the ingress policy of the outside interface, nor by the egress policy of the inside interface.
For traffic that is not treated as a flow, for example ICMP when you do not enable stateful ICMP
inspection, returning traffic can match a different policy map on the returning interface. For example, if
you configure IPS inspection on the inside and outside interfaces, but the inside policy uses virtual
sensor 1 while the outside policy uses virtual sensor 2, then a non-stateful Ping will match virtual sensor
1 outbound, but will match virtual sensor 2 inbound.
Order in Which Multiple Feature Actions are Applied
The order in which different types of actions in a policy map are performed is independent of the order
in which the actions appear in the policy map. Actions are performed in the following order:
•
QoS input policing
•
TCP normalization, TCP and UDP connection limits and timeouts, and TCP sequence number
randomization
When a the security appliance performs a proxy service (such as AAA or CSC) or it modifies
the TCP payload (such as FTP inspection), the TCP normalizer acts in dual mode, where it is
applied before and after the proxy or payload modifying service.
Note
•
CSC
•
Application inspection
•
IPS
•
QoS output policing
•
QoS standard priority queue
•
QoS traffic shaping, hierarchical priority queue
Default Layer 3/4 Policy Map
The configuration includes a default Layer 3/4 policy map that the security appliance uses in the default
global policy. It is called global_policy and performs inspection on the default inspection traffic. You
can only apply one global policy, so if you want to alter the global policy, you need to either reconfigure
the default policy or disable it and apply a new one.
The default policy map configuration includes the following commands:
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policy-map global_policy
class inspection_default
inspect dns preset_dns_map
inspect ftp
inspect h323 h225
inspect h323 ras
inspect rsh
inspect rtsp
inspect esmtp
inspect sqlnet
inspect skinny
inspect sunrpc
inspect xdmcp
inspect sip
inspect netbios
inspect tftp
Adding a Layer 3/4 Policy Map
The maximum number of policy maps is 64. To create a Layer 3/4 policy map, perform the following
steps:
Step 1
Add the policy map by entering the following command:
hostname(config)# policy-map policy_map_name
The policy_map_name argument is the name of the policy map up to 40 characters in length. All types
of policy maps use the same name space, so you cannot reuse a name already used by another type of
policy map. The CLI enters policy-map configuration mode.
Step 2
(Optional) Specify a description for the policy map:
hostname(config-pmap)# description text
Step 3
Specify a previously configured Layer 3/4 class map using the following command:
hostname(config-pmap)# class class_map_name
See the “Identifying Traffic (Layer 3/4 Class Map)” section on page 21-4 to add a class map.
Step 4
Specify one or more actions for this class map.
•
IPS. See the “Diverting Traffic to the AIP SSM” section on page 22-2.
•
CSC. See the “Diverting Traffic to the CSC SSM” section on page 22-11.
•
TCP normalization. See the “Configuring TCP Normalization” section on page 23-1.
•
TCP and UDP connection limits and timeouts, and TCP sequence number randomization. See the
“Configuring Connection Limits and Timeouts” section on page 23-6.
•
QoS. See Chapter 24, “Configuring QoS.”
Note
•
You can configure a hierarchical policy map for the traffic shaping and priority queue
features. See the “Hierarchical Policy Maps” section on page 21-16 for more information.
Application inspection. See Chapter 25, “Configuring Application Layer Protocol Inspection.”
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Note
Step 5
If there is no match default_inspection_traffic command in a class map, then at most one
inspect command is allowed to be configured under the class.
Repeat Step 3 and Step 4 for each class map you want to include in this policy map.
The following is an example of a policy-map command for connection policy. It limits the number of
connections allowed to the web server 10.1.1.1:
hostname(config)# access-list http-server permit tcp any host 10.1.1.1
hostname(config)# class-map http-server
hostname(config-cmap)# match access-list http-server
hostname(config)# policy-map global-policy
hostname(config-pmap)# description This policy map defines a policy concerning connection
to http server.
hostname(config-pmap)# class http-server
hostname(config-pmap-c)# set connection conn-max 256
The following example shows how multi-match works in a policy map:
hostname(config)# class-map inspection_default
hostname(config-cmap)# match default-inspection-traffic
hostname(config)# class-map http_traffic
hostname(config-cmap)# match port tcp eq 80
hostname(config)# policy-map outside_policy
hostname(config-pmap)# class inspection_default
hostname(config-pmap-c)# inspect http http_map
hostname(config-pmap-c)# inspect sip
hostname(config-pmap)# class http_traffic
hostname(config-pmap-c)# set connection timeout tcp 0:10:0
The following example shows how traffic matches the first available class map, and will not match any
subsequent class maps that specify actions in the same feature domain:
hostname(config)# class-map telnet_traffic
hostname(config-cmap)# match port tcp eq 23
hostname(config)# class-map ftp_traffic
hostname(config-cmap)# match port tcp eq 21
hostname(config)# class-map tcp_traffic
hostname(config-cmap)# match port tcp range 1 65535
hostname(config)# class-map udp_traffic
hostname(config-cmap)# match port udp range 0 65535
hostname(config)# policy-map global_policy
hostname(config-pmap)# class telnet_traffic
hostname(config-pmap-c)# set connection timeout tcp 0:0:0
hostname(config-pmap-c)# set connection conn-max 100
hostname(config-pmap)# class ftp_traffic
hostname(config-pmap-c)# set connection timeout tcp 0:5:0
hostname(config-pmap-c)# set connection conn-max 50
hostname(config-pmap)# class tcp_traffic
hostname(config-pmap-c)# set connection timeout tcp 2:0:0
hostname(config-pmap-c)# set connection conn-max 2000
When a Telnet connection is initiated, it matches class telnet_traffic. Similarly, if an FTP connection is
initiated, it matches class ftp_traffic. For any TCP connection other than Telnet and FTP, it will match
class tcp_traffic. Even though a Telnet or FTP connection can match class tcp_traffic, the security
appliance does not make this match because they previously matched other classes.
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Applying Actions to an Interface (Service Policy)
Applying Actions to an Interface (Service Policy)
To activate the Layer 3/4 policy map, create a service policy that applies it to one or more interfaces or
that applies it globally to all interfaces. Interface service policies take precedence over the global service
policy for a given feature. For example, if you have a global policy with inspections, and an interface
policy with TCP normalization, then both inspections and TCP normalization are applied to the
interface. However, if you have a global policy with inspections, and an interface policy with
inspections, then only the interface policy inspections are applied to that interface.
•
To create a service policy by associating a policy map with an interface, enter the following
command:
hostname(config)# service-policy policy_map_name interface interface_name
•
To create a service policy that applies to all interfaces that do not have a specific policy, enter the
following command:
hostname(config)# service-policy policy_map_name global
By default, the configuration includes a global policy that matches all default application inspection
traffic and applies inspection to the traffic globally. You can only apply one global policy, so if you
want to alter the global policy, you need to either edit the default policy or disable it and apply a new
one.
The default service policy includes the following command:
service-policy global_policy global
For example, the following command enables the inbound_policy policy map on the outside interface:
hostname(config)# service-policy inbound_policy interface outside
The following commands disable the default global policy, and enables a new one called
new_global_policy on all other security appliance interfaces:
hostname(config)# no service-policy global_policy global
hostname(config)# service-policy new_global_policy global
Modular Policy Framework Examples
This section includes several Modular Policy Framework examples, and includes the following topics:
•
Applying Inspection and QoS Policing to HTTP Traffic, page 21-22
•
Applying Inspection to HTTP Traffic Globally, page 21-22
•
Applying Inspection and Connection Limits to HTTP Traffic to Specific Servers, page 21-23
•
Applying Inspection to HTTP Traffic with NAT, page 21-24
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Applying Inspection and QoS Policing to HTTP Traffic
In this example (see Figure 21-1), any HTTP connection (TCP traffic on port 80) that enters or exits the
security appliance through the outside interface is classified for HTTP inspection. Any HTTP traffic that
exits the outside interface is classified for policing.
HTTP Inspection and QoS Policing
Security
appliance
port 80
A
insp.
police
port 80
insp.
Host A
inside
outside
Host B
143356
Figure 21-1
See the following commands for this example:
hostname(config)# class-map http_traffic
hostname(config-cmap)# match port tcp eq 80
hostname(config)# policy-map http_traffic_policy
hostname(config-pmap)# class http_traffic
hostname(config-pmap-c)# inspect http
hostname(config-pmap-c)# police output 250000
hostname(config)# service-policy http_traffic_policy interface outside
Applying Inspection to HTTP Traffic Globally
In this example (see Figure 21-2), any HTTP connection (TCP traffic on port 80) that enters the security
appliance through any interface is classified for HTTP inspection. Because the policy is a global policy,
inspection occurs only as the traffic enters each interface.
Figure 21-2
Global HTTP Inspection
Security
appliance
port 80
A
Host A
inside
port 80 insp.
outside
Host B
143414
insp.
See the following commands for this example:
hostname(config)# class-map http_traffic
hostname(config-cmap)# match port tcp eq 80
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hostname(config)# policy-map http_traffic_policy
hostname(config-pmap)# class http_traffic
hostname(config-pmap-c)# inspect http
hostname(config)# service-policy http_traffic_policy global
Applying Inspection and Connection Limits to HTTP Traffic to Specific Servers
In this example (see Figure 21-3), any HTTP connection destined for Server A (TCP traffic on port 80)
that enters the security appliance through the outside interface is classified for HTTP inspection and
maximum connection limits. Connections initiated from server A to Host A does not match the access
list in the class map, so it is not affected.
Any HTTP connection destined for Server B that enters the security appliance through the inside
interface is classified for HTTP inspection. Connections initiated from server B to Host B does not match
the access list in the class map, so it is not affected.
Figure 21-3
HTTP Inspection and Connection Limits to Specific Servers
Server A
Real Address: 192.168.1.2
Mapped Address: 209.165.201.1
Security
appliance
port 80
insp.
set conns
port 80
insp. inside
Host B
Real Address: 192.168.1.1
Mapped Address: 209.165.201.2:port
outside
Server B
209.165.200.227
143357
Host A
209.165.200.226
See the following commands for this example:
hostname(config)#
hostname(config)#
hostname(config)#
hostname(config)#
hostname(config)#
static (inside,outside) 209.165.201.1 192.168.1.2
nat (inside) 1 192.168.1.0 255.255.255.0
global (outside) 1 209.165.201.2
access-list serverA extended permit tcp any host 209.165.201.1 eq 80
access-list ServerB extended permit tcp any host 209.165.200.227 eq 80
hostname(config)# class-map http_serverA
hostname(config-cmap)# match access-list serverA
hostname(config)# class-map http_serverB
hostname(config-cmap)# match access-list serverB
hostname(config)# policy-map policy_serverA
hostname(config-pmap)# class http_serverA
hostname(config-pmap-c)# inspect http
hostname(config-pmap-c)# set connection conn-max 100
hostname(config)# policy-map policy_serverB
hostname(config-pmap)# class http_serverB
hostname(config-pmap-c)# inspect http
hostname(config)# service-policy policy_serverB interface inside
hostname(config)# service-policy policy_serverA interface outside
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Applying Inspection to HTTP Traffic with NAT
In this example, the Host on the inside network has two addresses: one is the real IP address 192.168.1.1,
and the other is a mapped IP address used on the outside network, 209.165.200.225. Because the policy
is applied to the inside interface, where the real address is used, then you must use the real IP address in
the access list in the class map. If you applied it to the outside interface, you would use the mapped
address.
Figure 21-4
HTTP Inspection with NAT
port 80
insp. inside
Host
Real IP: 192.168.1.1
Mapped IP: 209.165.200.225
outside
Server
209.165.201.1
143416
Security
appliance
See the following commands for this example:
hostname(config)# static (inside,outside) 209.165.200.225 192.168.1.1
hostname(config)# access-list http_client extended permit tcp host 192.168.1.1 any eq 80
hostname(config)# class-map http_client
hostname(config-cmap)# match access-list http_client
hostname(config)# policy-map http_client
hostname(config-pmap)# class http_client
hostname(config-pmap-c)# inspect http
hostname(config)# service-policy http_client interface inside
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Managing AIP SSM and CSC SSM
The Cisco ASA 5500 series adaptive security appliance supports a variety of SSMs. This chapter
describes how to configure the adaptive security appliance to support an AIP SSM or a CSC SSM,
including how to send traffic to these SSMs.
For information about the 4GE SSM for the ASA 5000 series adaptive security appliance, see Chapter 5,
“Configuring Ethernet Settings and Subinterfaces”.
Note
The Cisco PIX 500 series security appliances cannot support SSMs.
This chapter includes the following sections:
•
Managing the AIP SSM, page 22-1
•
Managing the CSC SSM, page 22-5
•
Checking SSM Status, page 22-13
•
Transferring an Image onto an SSM, page 22-14
Managing the AIP SSM
This section contains the following topics:
•
About the AIP SSM, page 22-1
•
Getting Started with the AIP SSM, page 22-2
•
Diverting Traffic to the AIP SSM, page 22-2
•
Sessioning to the AIP SSM and Running Setup, page 22-4
About the AIP SSM
The ASA 5500 series adaptive security appliance supports the AIP SSM, which runs advanced
IPS software that provides further security inspection. The adaptive security appliance diverts packets
to the AIP SSM just before the packet exits the egress interface (or before VPN encryption occurs, if
configured) and after other firewall policies are applied. For example, packets that are blocked by an
access list are not forwarded to the AIP SSM.
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The AIP SSM can operate in one of two modes, as follows:
•
Inline mode—Places the AIP SSM directly in the traffic flow. No traffic can continue through the
adaptive security appliance without first passing through, and being inspected by, the AIP SSM. This
mode is the most secure because every packet is analyzed before being allowed through. Also, the
AIP SSM can implement a blocking policy on a packet-by-packet basis. This mode, however, can
affect throughput. You specify this mode with the inline keyword of the ips command.
•
Promiscuous mode—Sends a duplicate stream of traffic to the AIP SSM. This mode is less secure,
but has little impact on traffic throughput. Unlike operation in inline mode, the SSM operating in
promiscuous mode can only block traffic by instructing the adaptive security appliance to shun the
traffic or by resetting a connection on the adaptive security appliance. Also, while the AIP SSM is
analyzing the traffic, a small amount of traffic might pass through the adaptive security appliance
before the AIP SSM can block it. You specify this mode with the inline keyword of the ips
command.
You can specify how the adaptive security appliance treats traffic when the AIP SSM is unavailable due
to hardware failure or other causes. Two keywords of the ips command control this behavior. The
fail-close keyword sets the adaptive security appliance to block all traffic if the AIP SSM is unavailable.
The fail-open keyword sets the adaptive security appliance to allow all traffic through, uninspected, if
the AIP SSM is unavailable.
For more information about configuring the operating mode of the AIP SSM and how the adaptive
security appliance treats traffic during an AIP SSM failure, see the “Diverting Traffic to the AIP SSM”
section on page 22-2.
Getting Started with the AIP SSM
Configuring the AIP SSM is a two-part process that involves configuration of the ASA 5500 series
adaptive security appliance first, and then configuration of the AIP SSM:
1.
On the ASA 5500 series adaptive security appliance, identify traffic to divert to the AIP SSM (as
described in the “Diverting Traffic to the AIP SSM” section on page 22-2).
2.
On the AIP SSM, configure the inspection and protection policy, which determines how to inspect
traffic and what to do when an intrusion is detected. Because the IPS software that runs on the AIP
SSM is very robust and beyond the scope of this document, detailed configuration information is
available in the following separate documentation:
•
Configuring the Cisco Intrusion Prevention System Sensor Using the Command Line Interface
•
Cisco Intrusion Prevention System Command Reference
Diverting Traffic to the AIP SSM
You use MPF commands to configure the adaptive security appliance to divert traffic to the AIP SSM.
Before configuring the adaptive security appliance to do so, read Chapter 21, “Using Modular Policy
Framework,” which introduces MPF concepts and common commands.
To identify traffic to divert from the adaptive security appliance to the AIP SSM, perform the following
steps:
Step 1
Create an access list that matches all traffic:
hostname(config)# access-list acl-name permit ip any any
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Step 2
Create a class map to identify the traffic that should be diverted to the AIP SSM. Use the class-map
command to do so, as follows:
hostname(config)# class-map class_map_name
hostname(config-cmap)#
where class_map_name is the name of the traffic class. When you enter the class-map command, the
CLI enters class map configuration mode.
Step 3
With the access list you created in Step 1, use a match access-list command to identify the traffic to be
scanned:
hostname(config-cmap)# match access-list acl-name
Step 4
Create a policy map or modify an existing policy map that you want to use to send traffic to the AIP
SSM. To do so, use the policy-map command, as follows.
hostname(config-cmap)# policy-map policy_map_name
hostname(config-pmap)#
where policy_map_name is the name of the policy map. The CLI enters the policy map configuration
mode and the prompt changes accordingly.
Step 5
Specify the class map, created in Step 2, that identifies the traffic to be scanned. Use the class command
to do so, as follows.
hostname(config-pmap)# class class_map_name
hostname(config-pmap-c)#
where class_map_name is the name of the class map you created in Step 2. The CLI enters the policy
map class configuration mode and the prompt changes accordingly.
Step 6
Assign the traffic identified by the class map as traffic to be sent to the AIP SSM. Use the ips command
to do so, as follows.
hostname(config-pmap-c)# ips {inline | promiscuous} {fail-close | fail-open}
The inline and promiscuous keywords control the operating mode of the AIP SSM. The fail-close and
fail-open keywords control how the adaptive security appliance treats traffic when the AIP SSM is
unavailable. For more information about the operating modes and failure behavior, see the “About the
AIP SSM” section on page 22-1.
Step 7
Use the service-policy command to apply the policy map globally or to a specific interface, as follows:
hostname(config-pmap-c)# service-policy policy_map_name [global | interface interface_ID]
hostname(config)#
where policy_map_name is the policy map you configured in Step 4. If you want to apply the policy map
to traffic on all the interfaces, use the global keyword. If you want to apply the policy map to traffic on
a specific interface, use the interface interface_ID option, where interface_ID is the name assigned to
the interface with the nameif command.
Only one global policy is allowed. You can override the global policy on an interface by applying a
service policy to that interface. You can only apply one policy map to each interface.
The adaptive security appliance begins diverting traffic to the AIP SSM as specified.
The following example diverts all IP traffic to the AIP SSM in promiscuous mode, and blocks all IP
traffic should the AIP SSM card fail for any reason:
hostname(config)# access-list IPS permit ip any any
hostname(config)# class-map my-ips-class
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hostname(config-cmap)# match access-list IPS
hostname(config-cmap)# policy-map my-ips-policy
hostname(config-pmap)# class my-ips-class
hostname(config-pmap-c)# ips promiscuous fail-close
hostname(config-pmap-c)# service-policy my-ips-policy global
For a complete example of network traffic diversion from the adaptive security appliance to the AIP
SSM, see Example 16: Network Traffic Diversion.
Sessioning to the AIP SSM and Running Setup
After you have completed configuration of the ASA 5500 series adaptive security appliance to divert
traffic to the AIP SSM, session to the AIP SSM and run the setup utility for initial configuration.
Note
You can either session to the SSM from the adaptive security appliance (by using the session 1
command) or you can connect directly to the SSM using SSH or Telnet on its management interface.
Alternatively, you can use ASDM.
To session to the AIP SSM from the adaptive security appliance, perform the following steps:
Step 1
Enter the session 1 command to session from the ASA 5500 series adaptive security appliance to the AIP
SSM:
hostname# session 1
Opening command session with slot 1.
Connected to slot 1. Escape character sequence is 'CTRL-^X'.
Step 2
Enter the username and password. The default username and password are both cisco.
Note
The first time you log in to the AIP SSM you are prompted to change the default password.
Passwords must be at least eight characters long and not a dictionary word.
login: cisco
Password:
Last login: Fri Sep 2 06:21:20 from xxx.xxx.xxx.xxx
***NOTICE***
This product contains cryptographic features and is subject to United States
and local country laws governing import, export, transfer and use. Delivery
of Cisco cryptographic products does not imply third-party authority to import,
export, distribute or use encryption. Importers, exporters, distributors and
users are responsible for compliance with U.S. and local country laws. By using
this product you agree to comply with applicable laws and regulations. If you
are unable to comply with U.S. and local laws, return this product immediately.
A summary of U.S. laws governing Cisco cryptographic products may be found at:
http://www.cisco.com/wwl/export/crypto/tool/stqrg.html
If you require further assistance please contact us by sending email to
[email protected]
***LICENSE NOTICE***
There is no license key installed on the system.
Please go to http://www.cisco.com/go/license
to obtain a new license or install a license.
AIP SSM#
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Note
Step 3
If you see the preceding license notice (which displays only in some versions of software), you can
ignore the message until you need to upgrade the signature files on the AIP SSM. The AIP SSM
continues to operate at the current signature level until a valid license key is installed. You can install
the license key at a later time. The license key does not affect the current functionality of the AIP SSM.
Enter the setup command to run the setup utility for initial configuration of the AIP SSM:
AIP SSM# setup
You are now ready to configure the AIP SSM for intrusion prevention. See the following two guides for
AIP SSM configuration information:
•
Configuring the Cisco Intrusion Prevention System Sensor Using the Command Line Interface
•
Cisco Intrusion Prevention System Command Reference
Managing the CSC SSM
This section contains the following topics:
•
About the CSC SSM, page 22-5
•
Getting Started with the CSC SSM, page 22-7
•
Determining What Traffic to Scan, page 22-9
•
Limiting Connections Through the CSC SSM, page 22-11
•
Diverting Traffic to the CSC SSM, page 22-11
About the CSC SSM
The ASA 5500 series adaptive security appliance supports the CSC SSM, which runs Content Security
and Control software. The CSC SSM provides protection against viruses, spyware, spam, and other
unwanted traffic. It accomplishes this by scanning the FTP, HTTP, POP3, and SMTP traffic that you
configure the adaptive security appliance to send to it.
Figure 22-1 illustrates the flow of traffic through an adaptive security appliance that has the following:
•
A CSC SSM installed and setup.
•
A service policy that determines what traffic is diverted to the SSM for scans.
In this example, the client could be a network user who is accessing a website, downloading files from
an FTP server, or retrieving mail from a POP3 server. SMTP scans differ in that you should configure
the adaptive security appliance to scan traffic sent from outside to SMTP servers protected by the
adaptive security appliance.
Note
The CSC SSM can scan FTP file transfers only when FTP inspection is enabled on the adaptive security
appliance. By default, FTP inspection is enabled.
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Figure 22-1
Flow of Scanned Traffic with CSC SSM
Security Appliance
Main System
modular
service
policy
Request sent
Request forwarded
inside
outside
Reply forwarded
Reply sent
Diverted Traffic
Server
content security scan
CSC SSM
148386
Client
You use ASDM for system setup and monitoring of the CSC SSM. For advanced configuration of content
security policies in the CSC SSM software, you access the web-based GUI for the CSC SSM by clicking
links within ASDM. Use of the CSC SSM GUI is explained in the Trend Micro InterScan for Cisco CSC
SSM Administrator Guide.
Note
ASDM and the CSC SSM maintain separate passwords. You can configure their passwords to be
identical; however, changing one of these two passwords does not affect the other password.
The connection between the host running ASDM and the adaptive security appliance is made through a
management port on the adaptive security appliance. The connection to the CSC SSM GUI is made
through the SSM management port. Because these two connections are required to manage the CSC
SSM, any host running ASDM must be able to reach the IP address of both the adaptive security
appliance management port and the SSM management port.
Figure 22-2 shows an adaptive security appliance with a CSC SSM that is connected to a dedicated
management network. While use of a dedicated management network is not required, we recommend it.
Of particular interest in Figure 22-2 are the following:
•
An HTTP proxy server is connected to the inside network and to the management network. This
enables the CSC SSM to contact the Trend Micro update server.
•
The management port of the adaptive security appliance is connected to the management network.
To permit management of the adaptive security appliance and the CSC SSM, hosts running ASDM
must be connected to the management network.
•
The management network includes an SMTP server for email notifications for the CSC SSM and a
syslog server that the CSC SSM can send syslog messages to.
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HTTP
Proxy
CSC SSM Deployment with a Management Network
Security
Appliance
inside
192.168.100.1
Main System
management port
192.168.50.1
Internet
CSC SSM
ASDM
Syslog
outside
10.6.13.67
Trend Micro
Update Server
192.168.50.38 SSM
management
port
148387
Figure 22-2
Notifications
SMTP Server
CSC SSM cannot suport stateful failover, because the CSC SSM does not maintain connection
information and therefore cannot provide the failover unit with information necessary for stateful
failover. The connections that a CSC SSM is scanning are dropped upon failure of the security appliance
that the CSC SSM is installed in. When the standby adaptive security appliance becomes active, it will
forward the scanned traffic to its CSC SSM and the connections will be reset.
Getting Started with the CSC SSM
Before you receive the security benefits provided by a CSC SSM, you must perform several steps beyond
simple hardware installation of the SSM. This procedure provides an overview of those steps.
To configure the adaptive security appliance and the CSC SSM, follow these steps:
Step 1
If the CSC SSM did not come pre-installed in a Cisco ASA 5500 series adaptive security appliance,
install it and connect a network cable to the management port of the SSM. For assistance with installation
and connecting the SSM, see the Cisco ASA 5500 Series Hardware Installation Guide.
The management port of the CSC SSM must be connected to your network to allow management of
and automatic updates to the CSC SSM software. Additionally, the CSC SSM uses the management
port for email notifications and syslogging.
Step 2
With the CSC SSM, you should have received a Product Authorization Key (PAK). Use the PAK to
register the CSC SSM at the following URL.
http://www.cisco.com/go/license
After you register, you will receive activation keys by email. The activation keys are required before you
can complete Step 6
Step 3
Gather the following information, for use in Step 6.
•
Activation keys, received after completing Step 2.
•
SSM management port IP address, netmask, and gateway IP address.
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Note
Step 4
The SSM management port IP address must be accessible by the hosts used to run ASDM.
The IP addresses for the SSM management port and the adaptive security appliance
management interface can be in different subnets.
•
DNS server IP address.
•
HTTP proxy server IP address (required only if your security policies require use of a proxy server
for HTTP access to the Internet).
•
Domain name and hostname for the SSM.
•
An email address and an SMTP server IP address and port number, for email notifications.
•
IP addresses of hosts or networks allowed to manage the CSC SSM.
•
Password for the CSC SSM.
In a web browser, access ASDM for the adaptive security appliance that the CSC SSM is in.
Note
If you are accessing ASDM for the first time, see the Cisco ASA 5500 Series Adaptive Security
Appliance Getting Started Guide for assistance with the Startup Wizard.
For more information about enabling ASDM access, see the “Allowing HTTPS Access for ASDM”
section on page 40-3.
Step 5
Step 6
Verify time settings on the adaptive security appliance. Time setting accuracy is important for logging
of security events and for automatic updates of CSC SSM software.
•
If you manually control time settings, verify the clock settings, including time zone. Choose
Configuration > Properties > Device Administration > Clock.
•
If you are using NTP, verify the NTP configuration. Choose Configuration > Properties > Device
Administration > NTP.
In ASDM, run the Content Security setup wizard. To do so, access the ASDM GUI in a supported web
browser and on the Home page, click the Content Security tab. The Content Security setup wizard runs.
For assistance with the Content Security setup wizard, click the Help button.
Note
If you are accessing ASDM for the first time, see the Cisco ASA 5500 Series Adaptive Security
Appliance Getting Started Guide for assistance with the Startup Wizard.
Step 7
On the ASA 5500 series adaptive security appliance, identify traffic to divert to the CSC SSM (as
described in the “Diverting Traffic to the CSC SSM” section on page 22-11).
Step 8
(Optional) Review the default content security policies in the CSC SSM GUI. The default content
security policies are suitable for most implementations. Modifying them is advanced configuration that
you should perform only after reading the Trend Micro InterScan for Cisco CSC SSM Administrator
Guide.
You review the content security policies by viewing the enabled features in the CSC SSM GUI. The
availability of features depends on the license level you purchased. By default, all features included in
the license you purchased are enabled.
With a Base License, the features enabled by default are SMTP virus scanning, POP3 virus scanning and
content filtering, webmail virus scanning, HTTP file blocking, FTP virus scanning and file blocking,
logging, and automatic updates.
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With a Plus License, the additional features enabled by default are SMTP anti-spam, SMTP content
filtering, POP3 anti-spam, URL blocking, and URL filtering.
To access the CSC SSM GUI, in ASDM choose Configuration > Trend Micro Content Security, and
then select one of the following: Web, Mail, File Transfer, or Updates. The blue links on these panes,
beginning with the word “Configure”, open the CSC SSM GUI.
Determining What Traffic to Scan
The CSC SSM can scan FTP, HTTP, POP3, and SMTP traffic. It supports these protocols only when the
destination port of the packet requesting the connection is the well known port for the protocol, that is,
CSC SSM can scan only the following connections:
•
FTP connections opened to TCP port 21.
•
HTTP connections opened to TCP port 80.
•
POP3 connections opened to TCP port 110.
•
SMTP connections opened to TCP port 25.
You can choose to scan traffic for all of these protocols or any combination of them. For example, if you
do not allow network users to receive POP3 email, you would not want to configure the adaptive security
appliance to divert POP3 traffic to the CSC SSM (you would want to block it instead).
To maximize performance of the adaptive security appliance and the CSC SSM, divert to the CSC SSM
only the traffic that you want the CSC SSM to scan. Needlessly diverting traffic that you do not want to
scan, such as traffic between a trusted source and destination, can adversely affect network performance.
The action of scanning traffic with the CSC SSM is enabled with the csc command, which must be part
of a service policy. Service policies can be applied globally or to specific interfaces; therefore, you can
choose to enable the csc command globally or for specific interfaces.
Adding the csc command to your global policy ensures that all unencrypted connections through the
adaptive security appliance are scanned by the CSC SSM; however, this may mean that traffic from
trusted sources is needlessly scanned.
If you enable the csc command in interface-specific service policies, it is bi-directional. This means that
when the adaptive security appliance opens a new connection, if the csc command is active on either the
inbound or the outbound interface of the connection and if the class map for the policy identifies traffic
for scanning, the adaptive security appliance diverts it to the CSC SSM.
However, bi-directionality means that if you divert to the CSC SSM any of the supported traffic types
that cross a given interface, the CSC SSM is likely performing needless scans on traffic from your trusted
inside networks. For example, URLs and files requested from web servers on a DMZ network are
unlikely to pose content security risks to hosts on an inside network and you probably do not want the
adaptive security appliance to divert such traffic to the CSC SSM.
Therefore, we highly recommend using access lists to further limit the traffic selected by the class maps
of CSC SSM service policies. Specifically, use access lists that match the following:
•
HTTP connections to outside networks.
•
FTP connections from clients inside the adaptive security appliance to servers outside the adaptive
security appliance.
•
POP3 connections from clients inside the security appliance to servers outside the adaptive security
appliance.
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•
Incoming SMTP connections destined to inside mail servers.
In Figure 22-3, the adaptive security appliance should be configured to divert traffic to CSC SSM
requests from clients on the inside network for HTTP, FTP, and POP3 connections to the outside network
and incoming SMTP connections from outside hosts to the mail server on the DMZ network. HTTP
requests from the inside network to the web server on the DMZ network should not be scanned.
Figure 22-3
Common Network Configuration for CSC SSM Scanning
Security
appliance
192.168.10.0
inside
outside
192.168.30.0
Internet
143800
192.168.20.0
(dmz)
Web server
Mail server
There are many ways you could configure the adaptive security appliance to identify the traffic that you
want to scan. One approach is to define two service policies, one on the inside interface and the other on
the outside interface, each with an access list that matches traffic to be scanned. The following access
list could be used on the policy applied to the inside interface:
access-list
access-list
access-list
access-list
csc_out
csc_out
csc_out
csc_out
permit tcp 192.168.10.0 255.255.255.0 any eq 21
deny tcp 192.168.10.0 255.255.255.0 192.168.20.0 255.255.255.0 eq 80
permit tcp 192.168.10.0 255.255.255.0 any eq 80
permit tcp 192.168.10.0 255.255.255.0 any eq 110
As previously mentioned, policies applying the csc command to a specific interface are effective on both
ingress and egress traffic, but by specifying 192.168.10.0 as the source network in the csc_out access list
the policy applied to the inside interface matches only connections initiated by the hosts on the inside
network. Notice also that the second ACE of the access list uses the deny keyword. This ACE does not
mean the adaptive security appliance blocks traffic sent from the 192.168.10.0 network to TCP port 80
on the 192.168.20.0 network. It simply exempts the traffic from being matched by the policy map and
thus prevents the adaptive security appliance from sending it to the CSC SSM.
You can use deny statements in an access list to exempt connections with trusted external hosts from
being scanned. For example, to reduce the load on the CSC SSM, you might want to exempt HTTP traffic
to a well known, trusted site. If the web server at such a site had the IP address 209.165.201.7, you could
add the following ACE to the csc_out access list to exclude HTTP connections between the trusted
external web server and inside hosts from being scanned by CSC SSM:
access-list csc_out deny tcp 192.168.10.0 255.255.255.0 209.165.201.7 255.255.255.255 eq 80
The second policy in this example, applied to the outside interface, could use the following access list:
access-list csc_in permit tcp any 192.168.20.0 255.255.255.0 eq 25
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This access list matches inbound SMTP connections from any external host to any host on the DMZ
network. The policy applied to the outside interface would therefore ensure that incoming SMTP email
would be diverted to the CSC SSM for scanning. It would not match SMTP connections from hosts on
the inside network to the mail server on the DMZ network because those connections never use the
outside interface.
If the web server on the DMZ network receives files uploaded by HTTP from external hosts, you could
add the following ACE to the csc_in access list to use the CSC SSM to protect the web server from
infected files:
access-list csc_in permit tcp any 192.168.20.0 255.255.255.0 eq 80
For a complete example service policy configuration using the access lists in this section, see
Example 22-1.
Limiting Connections Through the CSC SSM
The adaptive security appliance can prevent the CSC SSM and the destinations of connections it scans
from accepting or even receiving requests for more connections than desired. It can do so for embryonic
connections or fully established connections. Also, you can specify limits for all clients included in a
class-map and per-client limits. The set connection command lets you configure limits for embryonic
connections or fully established connections.
Also, you can specify limits for all clients included in a class-map and per-client limits. The
per-client-embryonic-max and per-client-max parameters limit the maximum number of connections
that individual clients can open. If a client uses more network resources simultaneously than is desired,
you can use these parameters to limit the number of connections that the adaptive security appliance
allows each client.
DoS attacks seek to disrupt networks by overwhelming the capacity of key hosts with connections or
requests for connections. You can use the set connection command to thwart DoS attacks. After you
configure a per-client maximum that can be supported by hosts likely to be attacked, malicious clients
will be unable to overwhelm hosts on protected networks.
Use of the set connection command to protect the CSC SSM and the destinations of connections it scans
is included in the “Diverting Traffic to the CSC SSM” section on page 22-11.
Diverting Traffic to the CSC SSM
You use MPF commands to configure the adaptive security appliance to divert traffic to the CSC SSM.
Before configuring the adaptive security appliance to do so, read Chapter 21, “Using Modular Policy
Framework,” which introduces MPF concepts and common commands.
To identify traffic to divert from the adaptive security appliance to the CSC SSM, perform the following
steps:
Step 1
Create an access list that matches the traffic you want scanned by the CSC SSM. To do so, use the
access-list extended command. Create as many ACEs as needed to match all the traffic. For example, if
you want to specify FTP, HTTP, POP3, and SMTP traffic, you would need four ACEs. For guidance on
identifying the traffic you want to scan, see the “Determining What Traffic to Scan” section on
page 22-9.
Step 2
Create a class map to identify the traffic that should be diverted to the CSC SSM. Use the class-map
command to do so, as follows.
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hostname(config)# class-map class_map_name
hostname(config-cmap)#
where class_map_name is the name of the traffic class. When you enter the class-map command, the
CLI enters class map configuration mode.
Step 3
With the access list you created in Step 1, use a match access-list command to identify the traffic to be
scanned:
hostname(config-cmap)# match access-list acl-name
Step 4
Create a policy map or modify an existing policy map that you want to use to send traffic to the CSC
SSM. To do so, use the policy-map command, as follows.
hostname(config-cmap)# policy-map policy_map_name
hostname(config-pmap)#
where policy_map_name is the name of the policy map. The CLI enters the policy map configuration
mode and the prompt changes accordingly.
Step 5
Specify the class map, created in Step 2, that identifies the traffic to be scanned. Use the class command
to do so, as follows.
hostname(config-pmap)# class class_map_name
hostname(config-pmap-c)#
where class_map_name is the name of the class map you created in Step 2. The CLI enters the policy
map class configuration mode and the prompt changes accordingly.
Step 6
If you want to enforce a per-client limit for simultaneous connections that the adaptive security appliance
diverts to the CSC SSM, use the set connection command, as follows:
hostname(config-pmap-c)# set connection per-client-max n
where n is the maximum simultaneous connections the adaptive security appliance will allow per client.
This prevents a single client from abusing the services of the CSC SSM or any server protected by the
SSM, including prevention of attempts at DoS attacks on HTTP, FTP, POP3, or SMTP servers that the
CSC SSM protects.
Step 7
Assign the traffic identified by the class map as traffic to be sent to the CSC SSM. Use the csc command
to do so, as follows.
hostname(config-pmap-c)# csc {fail-close | fail-open}
The fail-close and fail-open keywords control how the adaptive security appliance treats traffic when
the CSC SSM is unavailable. For more information about the operating modes and failure behavior, see
the “About the CSC SSM” section on page 22-5.
Step 8
Use the service-policy command to apply the policy map globally or to a specific interface, as follows:
hostname(config-pmap-c)# service-policy policy_map_name [global | interface interface_ID]
hostname(config)#
where policy_map_name is the policy map you configured in Step 4. If you want to apply the policy map
to traffic on all the interfaces, use the global keyword. If you want to apply the policy map to traffic on
a specific interface, use the interface interface_ID option, where interface_ID is the name assigned to
the interface with the nameif command.
Only one global policy is allowed. You can override the global policy on an interface by applying a
service policy to that interface. You can only apply one policy map to each interface.
The adaptive security appliance begins diverting traffic to the CSC SSM as specified.
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Checking SSM Status
Example 22-1 is based on the network shown in Figure 22-3. It creates two service policies. The first
policy, csc_out_policy, is applied to the inside interface and uses the csc_out access list to ensure that
all outbound requests for FTP and POP3 are scanned. The csc_out access list also ensures that HTTP
connections from inside to networks on the outside interface are scanned but it includes a deny ACE to
exclude HTTP connections from inside to servers on the DMZ network.
The second policy, csc_in_policy, is applied to the outside interface and uses the csc_in access list to
ensure that requests for SMTP and HTTP originating on the outside interface and destined for the DMZ
network are scanned by the CSC SSM. Scanning HTTP requests protects the web server from HTTP file
uploads.
Example 22-1 Service Policies for a Common CSC SSM Scanning Scenario
hostname(config)#
hostname(config)#
hostname(config)#
hostname(config)#
access-list
access-list
access-list
access-list
csc_out
csc_out
csc_out
csc_out
permit tcp 192.168.10.0 255.255.255.0 any eq 21
deny tcp 192.168.10.0 255.255.255.0 192.168.20.0 255.255.255.0 eq 80
permit tcp 192.168.10.0 255.255.255.0 any eq 80
permit tcp 192.168.10.0 255.255.255.0 any eq 110
hostname(config)# class-map csc_outbound_class
hostname(config-cmap)# match access-list csc_out
hostname(config)# policy-map csc_out_policy
hostname(config-pmap)# class csc_outbound_class
hostname(config-pmap-c)# csc fail-close
hostname(config)# service-policy csc_out_policy interface inside
hostname(config)# access-list csc_in permit tcp any 192.168.20.0 255.255.255.0 eq 25
hostname(config)# access-list csc_in permit tcp any 192.168.20.0 255.255.255.0 eq 80
hostname(config)# class-map csc_inbound_class
hostname(config-cmap)# match access-list csc_in
hostname(config)# policy-map csc_in_policy
hostname(config-pmap)# class csc_inbound_class
hostname(config-pmap-c)# csc fail-close
hostname(config)# service-policy csc_in_policy interface outside
Note
FTP inspection must be enabled for CSC SSM to scan files transferred by FTP. FTP inspection is enabled
by default.
Checking SSM Status
To check the status of an SSM, use the show module command.
The follow example output is from an adaptive security appliance with a CSC SSM installed. The Status
field indicates the operational status of the SSM. An SSM operating normally has a status of “Up” in the
output of the show module command. While the adaptive security appliance transfers an application
image to the SSM, the Status field in the output reads “Recover”. For more information about possible
statuses, see the entry for the show module command in the Cisco Security Appliance Command
Reference.
hostname# show module 1
Mod Card Type
Model
Serial No.
--- -------------------------------------------- ------------------ -----------
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0 ASA 5520 Adaptive Security Appliance
1 ASA 5500 Series Security Services Module-20
ASA5520
ASA-SSM-20
P3000000034
0
Mod MAC Address Range
Hw Version
Fw Version
Sw Version
--- --------------------------------- ------------ ------------ --------------0 000b.fcf8.c30d to 000b.fcf8.c311 1.0
1.0(10)0
7.1(0)1
1 000b.fcf8.012c to 000b.fcf8.012c 1.0
1.0(10)0
Trend Micro InterScan Security Module Version 5.0
Mod SSM Application Name
SSM Application Version
--- ------------------------------ -------------------------1 Trend Micro InterScan Security Version 5.0
Mod
--0
1
Status
-----------------Up Sys
Up
Data Plane Status
Compatability
--------------------- ------------Not Applicable
Up
The argument 1, at the end of the command, is the slot number occupied by the SSM. If you do not know
the slot number, you can omit it and see information about all modules, including the adaptive security
appliance, which is considered to occupy slot 0 (zero).
Use the details keyword to view additional information for the SSM.
The follow example output is from an adaptive security appliance with a CSC SSM installed.
hostname# show module 1 details
Getting details from the Service Module, please wait...
ASA 5500 Series Security Services Module-20
Model:
ASA-SSM-20
Hardware version:
1.0
Serial Number:
0
Firmware version:
1.0(10)0
Software version:
Trend Micro InterScan Security Module Version 5.0
App. name:
Trend Micro InterScan Security Module
App. version:
Version 5.0
Data plane Status: Up
Status:
Up
HTTP Service:
Up
Mail Service:
Up
FTP Service:
Up
Activated:
Yes
Mgmt IP addr:
10.23.62.92
Mgmt web port:
8443
Transferring an Image onto an SSM
For an intelligent SSM, such as AIP SSM or CSC SSM, you can transfer application images from a TFTP
server to the SSM. This process supports upgrade images and maintenance images.
Note
If you are upgrading the application on the SSM, the SSM application may support backup of its
configuration. If you do not back up the configuration of the SSM application, it is lost when you transfer
an image onto the SSM. For more information about how your SSM supports backups, see the
documentation for your SSM.
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Transferring an Image onto an SSM
To transfer an image onto an intelligent SSM, perform the following steps:
Step 1
Create or modify a recovery configuration for the SSM. To do so, perform the following steps:
a.
Determine if there is a recovery configuration for the SSM. To do so, use the show module
command with the recover keyword, as follows.
hostname# show module slot recover
where slot is the slot number occupied by the SSM.
If the recover keyword is not valid, a recovery configuration does not exist. The recover keyword
of the show module command is available only when a recovery configuration exists for the SSM.
Note
When the adaptive security appliance operates in multiple context mode, the configure
keyword is available only in the system context.
If there is a recovery configuration for the SSM, the adaptive security appliance displays it. Examine
the recovery configuration closely to ensure that it is correct, especially the Image URL field. The
following example show a recovery configuration for an SSM in slot 1.
hostname# show module 1 recover
Module 1 recover parameters. . .
Boot Recovery Image: Yes
Image URL:
tftp://10.21.18.1/ids-oldimg
Port IP Address:
10.1.2.10
Port Mask :
255.255.255.0
Gateway IP Address: 10.1.2.254
b.
If you need to create or modify the recovery configuration, use the hw-module module recover
command with the configure keyword, as follows:
hostname# hw-module module slot recover configure
where slot is the slot number occupied by the SSM.
Complete the prompts as applicable. If you are modifying a configuration, you can keep the
previously configured value by pressing Enter. The following example shows the prompts. For more
information about them, see the entry for the hw-module module recover command in the Cisco
Security Appliance Command Reference.
Image URL [tftp://0.0.0.0/]:
Port IP Address [0.0.0.0]:
VLAN ID [0]:
Gateway IP Address [0.0.0.0]:
Note
Be sure the TFTP server you specify can transfer files up to 60 MB in size. Also, be sure the
TFTP server can connect to the management port IP address that you specify for the SSM.
After you complete the prompts, the adaptive security appliance is ready to transfer to the SSM the
image that it finds at the URL you specified.
Step 2
Transfer the image from the TFTP server to the SSM and restart the SSM. To do so, use the hw-module
module recover command with the boot keyword, as follows.
hostname# hw-module module slot recover boot
where slot is the slot number occupied by the SSM.
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Step 3
Check the progress of the image transfer and SSM restart process. To do so, use the show module
command. For details, see the “Checking SSM Status” section on page 22-13.
When the adaptive security appliance completes the image transfer and restart of the SSM, the SSM is
running the newly transferred image.
Note
If your SSM supports configuration backups and you want to restore the configuration of the application
running on the SSM, see the documentation for your SSM for details.
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23
Preventing Network Attacks
This chapter describes how to prevent network attacks by configuring TCP normalization, limiting TCP
and UDP connections, and many other protection features.
This chapter includes the following sections:
•
Configuring TCP Normalization, page 23-1
•
Configuring Connection Limits and Timeouts, page 23-6
•
Preventing IP Spoofing, page 23-10
•
Configuring the Fragment Size, page 23-11
•
Blocking Unwanted Connections, page 23-11
•
Configuring IP Audit for Basic IPS Support, page 23-12
Configuring TCP Normalization
The TCP normalization feature identifies abnormal packets that the security appliance can act on when
they are detected; for example, the security appliance can allow, drop, or clear the packets. TCP
normalization helps protect the security appliance from attacks. This section includes the following
topics:
•
TCP Normalization Overview, page 23-1
•
Enabling the TCP Normalizer, page 23-2
TCP Normalization Overview
The TCP normalizer includes non-configurable actions and configurable actions. Typically,
non-configurable actions that drop or clear connections apply to packets that are always bad.
Configurable actions (as detailed in “Enabling the TCP Normalizer” section on page 23-2) might need
to be customized depending on your network needs.
See the following guidelines for TCP normalization:
•
The normalizer does not protect from SYN floods. The security appliance includes SYN flood
protection in other ways.
•
The normalizer always sees the SYN packet as the first packet in a flow unless the security appliance
is in loose mode due to failover.
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Configuring TCP Normalization
Enabling the TCP Normalizer
This feature uses Modular Policy Framework, so that implementing TCP normalization consists of
identifying traffic, specifying the TCP normalization actions, and activating TCP normalization on an
interface. See Chapter 21, “Using Modular Policy Framework,” for more information.
To configure TCP normalization, perform the following steps:
Step 1
To specify the TCP normalization criteria that you want to look for, create a TCP map by entering the
following command:
hostname(config)# tcp-map tcp-map-name
For each TCP map, you can customize one or more settings.
Step 2
(Optional) Configure the TCP map criteria by entering one or more of the following commands (see
Table 23-1). If you want to use the default settings for all criteria, you do not need to enter any commands
for the TCP map. If you want to customize some settings, then the defaults are used for any commands
you do not enter. The default configuration includes the following settings:
no check-retransmission
no checksum-verification
exceed-mss allow
queue-limit 0 timeout 4
reserved-bits allow
syn-data allow
synack-data drop
invalid-ack drop
seq-past-window drop
tcp-options range 6 7 clear
tcp-options range 9 255 clear
tcp-options selective-ack allow
tcp-options timestamp allow
tcp-options window-scale allow
ttl-evasion-protection
urgent-flag clear
window-variation allow-connection
Table 23-1
tcp-map Commands
Command
Notes
check-retransmission
Prevents inconsistent TCP retransmissions.
checksum-verification
Verifies the checksum.
exceed-mss {allow | drop}
Sets the action for packets whose data length exceeds the TCP
maximum segment size.
(Default) The allow keyword allows packets whose data length
exceeds the TCP maximum segment size.
The drop keyword drops packets whose data length exceeds the
TCP maximum segment size.
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Table 23-1
tcp-map Commands (continued)
Command
Notes
invalid-ack {allow | drop}
Sets the action for packets with an invalid ACK. You might see
invalid ACKs in the following instances:
•
In the TCP connection SYN-ACK-received status, if the ACK
number of a received TCP packet is not exactly same as the
sequence number of the next TCP packet sending out, it is an
invalid ACK.
•
Whenever the ACK number of a received TCP packet is
greater than the sequence number of the next TCP packet
sending out, it is an invalid ACK.
The allow keyword allows packets with an invalid ACK.
(Default) The drop keyword drops packets with an invalid ACK.
Note
queue-limit pkt_num
[timeout seconds]
TCP packets with an invalid ACK are automatically
allowed for WAAS connections.
Sets the maximum number of out-of-order packets that can be
buffered and put in order for a TCP connection, between 1 and 250
packets. The default is 0, which means this setting is disabled and
the default system queue limit is used depending on the type of
traffic:
•
Connections for application inspection (the inspect
command), IPS (the ips command), and TCP
check-retransmission (the TCP map check-retransmission
command) have a queue limit of 3 packets. If the security
appliance receives a TCP packet with a different window size,
then the queue limit is dynamically changed to match the
advertised setting.
•
For other TCP connections, out-of-order packets are passed
through untouched.
If you set the queue-limit command to be 1 or above, then the
number of out-of-order packets allowed for all TCP traffic matches
this setting. For application inspection, IPS, and TCP
check-retransmission traffic, any advertised settings are ignored.
For other TCP traffic, out-of-order packets are now buffered and
put in order instead of passed through untouched.
The timeout seconds argument sets the maximum amount of time
that out-of-order packets can remain in the buffer, between 1 and
20 seconds; if they are not put in order and passed on within the
timeout period, then they are dropped. The default is 4 seconds.
You cannot change the timeout for any traffic if the pkt_num
argument is set to 0; you need to set the limit to be 1 or above for
the timeout keyword to take effect.
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Table 23-1
tcp-map Commands (continued)
Command
Notes
reserved-bits {allow | clear |
drop}
Sets the action for reserved bits in the TCP header.
(Default) The allow keyword allows packets with the reserved bits
in the TCP header.
The clear keyword clears the reserved bits in the TCP header and
allows the packet.
The drop keyword drops the packet with the reserved bits in the
TCP header.
seq-past-window {allow | drop}
Sets the action for packets that have past-window sequence
numbers, namely the sequence number of a received TCP packet
is greater than the right edge of the TCP receiving window.
The allow keyword allows packets that have past-window
sequence numbers. This action is only allowed if the queue-limit
command is set to 0 (disabled).
(Default) The drop keyword drops packets that have past-window
sequence numbers.
synack-data {allow | drop}
Sets the action for TCP SYNACK packets that contain data.
The allow keyword allows TCP SYNACK packets that contain
data.
(Default) The drop keyword drops TCP SYNACK packets that
contain data.
syn-data {allow | drop}
Sets the action for SYN packets with data.
(Default) The allow keyword allows SYN packets with data.
The drop keyword drops SYN packets with data.
tcp-options {selective-ack |
timestamp | window-scale}
{allow | clear}
Sets the action for packets with TCP options, including the
selective-ack, timestamp, or window-scale TCP options.
Or
(Default) The allow keyword allows packets with the specified
option.
tcp-options range lower upper
{allow | clear | drop}
(Default for range) The clear keyword clears the option and
allows the packet.
The drop keyword drops the packet with the specified option.
The selective-ack keyword sets the action for the SACK option.
The timestamp keyword sets the action for the timestamp option.
Clearing the timestamp option disables PAWS and RTT.
The widow-scale keyword sets the action for the window scale
mechanism option.
The range keyword specifies a range of options. The lower
argument sets the lower end of the range as 6, 7, or 9 through 255.
The upper argument sets the upper end of the range as 6, 7, or 9
through 255.
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Table 23-1
tcp-map Commands (continued)
Command
Notes
ttl-evasion-protection
Disables the TTL evasion protection. Do not enter this command
it you want to prevent attacks that attempt to evade security policy.
For example, an attacker can send a packet that passes policy with
a very short TTL. When the TTL goes to zero, a router between the
security appliance and the endpoint drops the packet. It is at this
point that the attacker can send a malicious packet with a long TTL
that appears to the security appliance to be a retransmission and is
passed. To the endpoint host, however, it is the first packet that has
been received by the attacker. In this case, an attacker is able to
succeed without security preventing the attack.
urgent-flag {allow | clear}
Sets the action for packets with the URG flag. The URG flag is
used to indicate that the packet contains information that is of
higher priority than other data within the stream. The TCP RFC is
vague about the exact interpretation of the URG flag, therefore end
systems handle urgent offsets in different ways, which may make
the end system vulnerable to attacks.
The allow keyword allows packets with the URG flag.
(Default) The clear keyword clears the URG flag and allows the
packet.
window-variation {allow | drop} Sets the action for a connection that has changed its window size
unexpectedly. The window size mechanism allows TCP to
advertise a large window and to subsequently advertise a much
smaller window without having accepted too much data. From the
TCP specification, “shrinking the window” is strongly
discouraged. When this condition is detected, the connection can
be dropped.
(Default) The allow keyword allows connections with a window
variation.
The drop keyword drops connections with a window variation.
Step 3
To identify the traffic, add a class map using the class-map command. See the “Creating a Layer 3/4
Class Map for Through Traffic” section on page 21-5 for more information.
For example, you can match all traffic using the following commands:
hostname(config)# class-map TCPNORM
hostname(config-cmap)# match any
To match specific traffic, you can match an access list:
hostname(config)# access list TCPNORM extended permit ip any 10.1.1.1 255.255.255.255
hostname(config)# class-map TCP_norm_class
hostname(config-cmap)# match access-list TCPNORM
Step 4
To add or edit a policy map that sets the actions to take with the class map traffic, enter the following
commands:
hostname(config)# policy-map name
hostname(config-pmap)# class class_map_name
hostname(config-pmap-c)#
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where the class_map_name is the class map from Step 1.
For example:
hostname(config)# policy-map TCP_norm_policy
hostname(config-pmap)# class TCP_norm_class
hostname(config-pmap-c)#
Step 5
Apply the TCP map to the class map by entering the following command.
hostname(config-pmap-c)# set connection advanced-options tcp-map-name
Step 6
To activate the policy map on one or more interfaces, enter the following command:
hostname(config)# service-policy policymap_name {global | interface interface_name}
Where global applies the policy map to all interfaces, and interface applies the policy to one interface.
Only one global policy is allowed. Interface service policies take precedence over the global service
policy for a given feature. For example, if you have a global policy with inspections, and an interface
policy with TCP normalization, then both inspections and TCP normalization are applied to the
interface. However, if you have a global policy with inspections, and an interface policy with
inspections, then only the interface policy inspections are applied to that interface.
For example, to allow urgent flag and urgent offset packets for all traffic sent to the range of TCP ports
between the well known FTP data port and the Telnet port, enter the following commands:
hostname(config)# tcp-map tmap
hostname(config-tcp-map)# urgent-flag allow
hostname(config-tcp-map)# class-map urg-class
hostname(config-cmap)# match port tcp range ftp-data telnet
hostname(config-cmap)# policy-map pmap
hostname(config-pmap)# class urg-class
hostname(config-pmap-c)# set connection advanced-options tmap
hostname(config-pmap-c)# service-policy pmap global
Configuring Connection Limits and Timeouts
This section describes how to set maximum TCP and UDP connections, maximum embryonic
connections, maximum per-client connections, connection timeouts, dead connection detection, and how
to disable TCP sequence randomization. You can set limits for connections that go through the security
appliance, or for management connections to the security appliance. This section includes the following
topics:
Note
•
Connection Limit Overview, page 23-7
•
Enabling Connection Limits and Timeouts, page 23-8
You can also configure maximum connections, maximum embryonic connections, and TCP sequence
randomization in the NAT configuration. If you configure these settings for the same traffic using both
methods, then the security appliance uses the lower limit. For TCP sequence randomization, if it is
disabled using either method, then the security appliance disables TCP sequence randomization.
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Connection Limit Overview
This section describes why you might want to limit connections, and includes the following topics:
•
TCP Intercept Overview, page 23-7
•
Disabling TCP Intercept for Management Packets for Clientless SSL Compatibility, page 23-7
•
Dead Connection Detection (DCD) Overview, page 23-7
•
TCP Sequence Randomization Overview, page 23-8
TCP Intercept Overview
Limiting the number of embryonic connections protects you from a DoS attack. The security appliance
uses the per-client limits and the embryonic connection limit to trigger TCP Intercept, which protects
inside systems from a DoS attack perpetrated by flooding an interface with TCP SYN packets. An
embryonic connection is a connection request that has not finished the necessary handshake between
source and destination. TCP Intercept uses the SYN cookies algorithm to prevent TCP SYN-flooding
attacks. A SYN-flooding attack consists of a series of SYN packets usually originating from spoofed IP
addresses. The constant flood of SYN packets keeps the server SYN queue full, which prevents it from
servicing connection requests. When the embryonic connection threshold of a connection is crossed, the
security appliance acts as a proxy for the server and generates a SYN-ACK response to the client SYN
request. When the security appliance receives an ACK back from the client, it can then authenticate the
client and allow the connection to the server.
Disabling TCP Intercept for Management Packets for Clientless SSL Compatibility
By default, TCP management connections have TCP Intercept always enabled. When TCP Intercept is
enabled, it intercepts the 3-way TCP connection establishment handshake packets and thus deprives the
security appliance from processing the packets for clientless SSL. Clientless SSL requires the ability to
process the 3-way handshake packets to provide selective ACK and other TCP options for clientless SSL
connections. To disable TCP Intercept for management traffic, you can set the embryonic connection
limit; only after the embryonic connection limit is reached is TCP Intercept enabled.
Dead Connection Detection (DCD) Overview
DCD detects a dead connection and allows it to expire, without expiring connections that can still handle
traffic. You configure DCD when you want idle, but valid connections to persist.
When you enable DCD, idle timeout behavior changes. With idle timeout, DCD probes are sent to each
of the two end-hosts to determine the validity of the connection. If an end-host fails to respond after
probes are sent at the configured intervals, the connection is freed, and reset values, if configured, are
sent to each of the end-hosts. If both end-hosts respond that the connection is valid, the activity timeout
is updated to the current time and the idle timeout is rescheduled accordingly.
Enabling DCD changes the behavior of idle-timeout handling in the TCP normalizer. DCD probing
resets the idle timeout on the connections seen in the show conn command. To determine when a
connection that has exceeded the configured timeout value in the timeout command but is kept alive due
to DCD probing, the show service-policy command includes counters to show the amount of activity
from DCD.
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TCP Sequence Randomization Overview
Each TCP connection has two ISNs: one generated by the client and one generated by the server. The
security appliance randomizes the ISN of the TCP SYN passing in both the inbound and outbound
directions.
Randomizing the ISN of the protected host prevents an attacker from predicting the next ISN for a new
connection and potentially hijacking the new session.
TCP initial sequence number randomization can be disabled if required. For example:
•
If another in-line firewall is also randomizing the initial sequence numbers, there is no need for both
firewalls to be performing this action, even though this action does not affect the traffic.
•
If you use eBGP multi-hop through the security appliance, and the eBGP peers are using MD5.
Randomization breaks the MD5 checksum.
•
You use a WAAS device that requires the security appliance not to randomize the sequence numbers
of connections.
Enabling Connection Limits and Timeouts
To set connection limits and timeouts, perform the following steps:
Step 1
To identify the traffic, add a class map using the class-map command. See the “Creating a Layer 3/4
Class Map for Through Traffic” section on page 21-5 for more information.
For example, you can match all traffic using the following commands:
hostname(config)# class-map CONNS
hostname(config-cmap)# match any
To match specific traffic, you can match an access list:
hostname(config)# access list CONNS extended permit ip any 10.1.1.1 255.255.255.255
hostname(config)# class-map CONNS
hostname(config-cmap)# match access-list CONNS
Step 2
To add or edit a policy map that sets the actions to take with the class map traffic, enter the following
commands:
hostname(config)# policy-map name
hostname(config-pmap)# class class_map_name
hostname(config-pmap-c)#
where the class_map_name is the class map from Step 1.
For example:
hostname(config)# policy-map CONNS
hostname(config-pmap)# class CONNS
hostname(config-pmap-c)#
Step 3
To set maximum connection limits or whether TCP sequence randomization is enabled, enter the
following command:
hostname(config-pmap-c)# set connection {[conn-max n] [embryonic-conn-max n]
[per-client-embryonic-max n] [per-client-max n] [random-sequence-number {enable |
disable}]}
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where the conn-max n argument sets the maximum number of simultaneous TCP and/or UDP
connections that are allowed, between 0 and 65535. The default is 0, which allows unlimited
connections.
The embryonic-conn-max n argument sets the maximum number of simultaneous embryonic
connections allowed, between 0 and 65535. The default is 0, which allows unlimited connections.
The per-client-embryonic-max n argument sets the maximum number of simultaneous embryonic
connections allowed per client, between 0 and 65535. The default is 0, which allows unlimited
connections.
The per-client-max n argument sets the maximum number of simultaneous connections allowed per
client, between 0 and 65535. The default is 0, which allows unlimited connections.
The random-sequence-number {enable | disable} keyword enables or disables TCP sequence number
randomization. See the “TCP Sequence Randomization Overview” section on page 23-8 section for
more information.
You can enter this command all on one line (in any order), or you can enter each attribute as a separate
command. The security appliance combines the command into one line in the running configuration.
Step 4
To set connection timeouts, enter the following command:
hostname(config-pmap-c)# set connection timeout {[embryonic hh:mm:ss] {tcp hh:mm:ss
[reset]] [half-closed hh:mm:ss] [dcd hh:mm:ss [max_retries]]}
where the embryonic hh:mm:ss keyword sets the timeout period until a TCP embryonic (half-open)
connection is closed, between 0:0:5 and 1193:00:00. The default is 0:0:30. You can also set this value to
0, which means the connection never times out.
The tcp hh:mm:ss keyword sets the idle timeout between 0:5:0 and 1193:00:00. The default is 1:0:0. You
can also set this value to 0, which means the connection never times out. The reset keyword sends a reset
to TCP endpoints when the connection times out. The security appliance sends the reset packet only in
response to a host sending another packet for the timed-out flow (on the same source and destination
port). The host then removes the connection from its connection table after receiving the reset packet.
The host application can then attempt to establish a new connection using a SYN packet.
The half-closed hh:mm:ss keyword sets the idle timeout between 0:5:0 and 1193:00:00. The default is
0:10:0. Half-closed connections are not affected by DCD. Also, the security appliance does not send a
reset when taking down half-closed connections.
The dcd keyword enables DCD. DCD detects a dead connection and allows it to expire, without expiring
connections that can still handle traffic. You configure DCD when you want idle, but valid connections
to persist. After a TCP connection times out, the security appliance sends DCD probes to the end hosts
to determine the validity of the connection. If one of the end hosts fails to respond after the maximum
retries are exhausted, the security appliance frees the connection. If both end hosts respond that the
connection is valid, the security appliance updates the activity timeout to the current time and
reschedules the idle timeout accordingly. The retry-interval sets the time duration in hh:mm:ss format
to wait after each unresponsive DCD probe before sending another probe, between 0:0:1 and 24:0:0. The
default is 0:0:15. The max-retries sets the number of consecutive failed retries for DCD before declaring
the connection as dead. The minimum value is 1 and the maximum value is 255. The default is 5.
You can enter this command all on one line (in any order), or you can enter each attribute as a separate
command. The command is combined onto one line in the running configuration.
Step 5
To activate the policy map on one or more interfaces, enter the following command:
hostname(config)# service-policy policymap_name {global | interface interface_name}
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Preventing IP Spoofing
Where global applies the policy map to all interfaces, and interface applies the policy to one interface.
Only one global policy is allowed. Interface service policies take precedence over the global service
policy for a given feature. For example, if you have a global policy with inspections, and an interface
policy with TCP normalization, then both inspections and TCP normalization are applied to the
interface. However, if you have a global policy with inspections, and an interface policy with
inspections, then only the interface policy inspections are applied to that interface.
The following example sets the connection limits and timeouts for all traffic:
hostname(config)# class-map CONNS
hostname(config-cmap)# match any
hostname(config-cmap)# policy-map CONNS
hostname(config-pmap)# class CONNS
hostname(config-pmap-c)# set connection conn-max 1000 embryonic-conn-max 3000
hostname(config-pmap-c)# set connection timeout tcp 2:0:0 embryonic 0:40:0 half-closed
0:20:0 dcd
hostname(config-pmap-c)# service-policy CONNS interface outside
You can enter set connection commands with multiple parameters or you can enter each parameter as a
separate command. The security appliance combines the commands into one line in the running
configuration. For example, if you entered the following two commands in class configuration mode:
hostname(config-pmap-c)# set connection conn-max 600
hostname(config-pmap-c)# set connection embryonic-conn-max 50
the output of the show running-config policy-map command would display the result of the two
commands in a single, combined command:
set connection conn-max 600 embryonic-conn-max 50
Preventing IP Spoofing
This section lets you enable Unicast Reverse Path Forwarding on an interface. Unicast RPF guards
against IP spoofing (a packet uses an incorrect source IP address to obscure its true source) by ensuring
that all packets have a source IP address that matches the correct source interface according to the
routing table.
Normally, the security appliance only looks at the destination address when determining where to
forward the packet. Unicast RPF instructs the security appliance to also look at the source address; this
is why it is called Reverse Path Forwarding. For any traffic that you want to allow through the security
appliance, the security appliance routing table must include a route back to the source address. See
RFC 2267 for more information.
For outside traffic, for example, the security appliance can use the default route to satisfy the
Unicast RPF protection. If traffic enters from an outside interface, and the source address is not known
to the routing table, the security appliance uses the default route to correctly identify the outside
interface as the source interface.
If traffic enters the outside interface from an address that is known to the routing table, but is associated
with the inside interface, then the security appliance drops the packet. Similarly, if traffic enters the
inside interface from an unknown source address, the security appliance drops the packet because the
matching route (the default route) indicates the outside interface.
Unicast RPF is implemented as follows:
•
ICMP packets have no session, so each packet is checked.
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Configuring the Fragment Size
•
UDP and TCP have sessions, so the initial packet requires a reverse route lookup. Subsequent
packets arriving during the session are checked using an existing state maintained as part of the
session. Non-initial packets are checked to ensure they arrived on the same interface used by the
initial packet.
To enable Unicast RPF, enter the following command:
hostname(config)# ip verify reverse-path interface interface_name
Configuring the Fragment Size
By default, the security appliance allows up to 24 fragments per IP packet, and up to 200 fragments
awaiting reassembly. You might need to let fragments on your network if you have an application that
routinely fragments packets, such as NFS over UDP. However, if you do not have an application that
fragments traffic, we recommend that you do not allow fragments through the security appliance.
Fragmented packets are often used as DoS attacks. To set disallow fragments, enter the following
command:
hostname(config)# fragment chain 1 [interface_name]
Enter an interface name if you want to prevent fragmentation on a specific interface. By default, this
command applies to all interfaces.
Blocking Unwanted Connections
If you know that a host is attempting to attack your network (for example, system log messages show an
attack), then you can block (or shun) connections based on the source IP address and other identifying
parameters. No new connections can be made until you remove the shun.
Note
If you have an IPS that monitors traffic, such as an AIP SSM, then the IPS can shun connections
automatically.
To shun a connection manually, perform the following steps:
Step 1
If necessary, view information about the connection by entering the following command:
hostname# show conn
The security appliance shows information about each connection, such as the following:
TCP out 64.101.68.161:4300 in 10.86.194.60:23 idle 0:00:00 bytes 1297 flags UIO
Step 2
To shun connections from the source IP address, enter the following command:
hostname(config)# shun src_ip [dst_ip src_port dest_port [protocol]] [vlan vlan_id]
If you enter only the source IP address, then all future connections are shunned; existing connections
remain active.
To drop an existing connection, as well as blocking future connections from the source IP address, enter
the destination IP address, source and destination ports, and the protocol. By default, the protocol is 0
for IP.
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Configuring IP Audit for Basic IPS Support
For multiple context mode, you can enter this command in the admin context, and by specifying a
VLAN ID that is assigned to an interface in other contexts, you can shun the connection in other
contexts.
Step 3
To remove the shun, enter the following command:
hostname(config)# no shun src_ip [vlan vlan_id]
Configuring IP Audit for Basic IPS Support
The IP audit feature provides basic IPS support for a security appliance that does not have an AIP SSM.
It supports a basic list of signatures, and you can configure the security appliance to perform one or more
actions on traffic that matches a signature.
To enable IP audit, perform the following steps:
Step 1
To define an IP audit policy for informational signatures, enter the following command:
hostname(config)# ip audit name name info [action [alarm] [drop] [reset]]
Where alarm generates a system message showing that a packet matched a signature, drop drops the
packet, and reset drops the packet and closes the connection. If you do not define an action, then the
default action is to generate an alarm.
Step 2
To define an IP audit policy for attack signatures, enter the following command:
hostname(config)# ip audit name name attack [action [alarm] [drop] [reset]]
Where alarm generates a system message showing that a packet matched a signature, drop drops the
packet, and reset drops the packet and closes the connection. If you do not define an action, then the
default action is to generate an alarm.
Step 3
To assign the policy to an interface, enter the following command:
ip audit interface interface_name policy_name
Step 4
To disable signatures, or for more information about signatures, see the ip audit signature command in
the Cisco Security Appliance Command Reference.
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24
Configuring QoS
Have you ever participated in a long-distance phone call that involved a satellite connection? The
conversation might be interrupted with brief, but perceptible, gaps at odd intervals. Those gaps are the
time, called the latency, between the arrival of packets being transmitted over the network. Some network
traffic, such as voice and video, cannot tolerate long latency times. Quality of Service (QoS) is a feature
that lets you give priority to critical traffic, prevent bandwidth hogging, and manage network bottlenecks
to prevent packet drops.
This chapter describes how to apply QoS policies, and includes the following sections:
•
QoS Overview, page 24-1
•
Creating the Standard Priority Queue for an Interface, page 24-5
•
Identifying Traffic for QoS Using Class Maps, page 24-6
•
Creating a Policy for Standard Priority Queueing and/or Policing, page 24-8
•
Creating a Policy for Traffic Shaping and Hierarchical Priority Queueing, page 24-10
•
Viewing QoS Statistics, page 24-12
QoS Overview
You should consider that in an ever-changing network environment, QoS is not a one-time deployment,
but an ongoing, essential part of network design.
Note
QoS is only available in single context mode.
This section describes the QoS features supported by the security appliance, and includes the following
topics:
•
Supported QoS Features, page 24-2
•
What is a Token Bucket?, page 24-2
•
Policing Overview, page 24-3
•
Priority Queueing Overview, page 24-3
•
Traffic Shaping Overview, page 24-4
•
DSCP and DiffServ Preservation, page 24-5
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QoS Overview
Supported QoS Features
The security appliance supports the following QoS features:
•
Policing—To prevent individual flows from hogging the network bandwidth, you can limit the
maximum bandwidth used per flow. See the “Policing Overview” section on page 24-3 for more
information.
•
Priority queuing—For critical traffic that cannot tolerate latency, such as voice over IP (VoIP), you
can identify traffic for low latency queuing (LLQ) so that it is always transmitted ahead of other
traffic. See the “Priority Queueing Overview” section on page 24-3 for more information.
•
Traffic shaping—If you have a device that transmits packets at a high speed, such as a security
appliance with Fast Ethernet, and it is connected to a low speed device such as a cable modem, then
the cable modem is a bottleneck at which packets are frequently dropped. To manage networks with
differing line speeds, you can configure the security appliance to transmit packets at a fixed slower
rate. See the “Traffic Shaping Overview” section on page 24-4 for more information.
What is a Token Bucket?
A token bucket is used to manage a device that regulates the data in a flow. For example, the regulator
might be a traffic policer or a traffic shaper. A token bucket itself has no discard or priority policy.
Rather, a token bucket discards tokens and leaves to the flow the problem of managing its transmission
queue if the flow overdrives the regulator.
A token bucket is a formal definition of a rate of transfer. It has three components: a burst size, an
average rate, and a time interval. Although the average rate is generally represented as bits per second,
any two values may be derived from the third by the relation shown as follows:
average rate = burst size / time interval
Here are some definitions of these terms:
•
Average rate—Also called the committed information rate (CIR), it specifies how much data can be
sent or forwarded per unit time on average.
•
Burst size—Also called the Committed Burst (Bc) size, it specifies in bits or bytes per burst how
much traffic can be sent within a given unit of time to not create scheduling concerns. (For traffic
shaping, it specifies bits per burst; for policing, it specifies bytes per burst.)
•
Time interval—Also called the measurement interval, it specifies the time quantum in seconds per
burst.
In the token bucket metaphor, tokens are put into the bucket at a certain rate. The bucket itself has a
specified capacity. If the bucket fills to capacity, newly arriving tokens are discarded. Each token is
permission for the source to send a certain number of bits into the network. To send a packet, the
regulator must remove from the bucket a number of tokens equal in representation to the packet size.
If not enough tokens are in the bucket to send a packet, the packet either waits until the bucket has
enough tokens (in the case of traffic shaping) or the packet is discarded or marked down (in the case of
policing). If the bucket is already full of tokens, incoming tokens overflow and are not available to future
packets. Thus, at any time, the largest burst a source can send into the network is roughly proportional
to the size of the bucket.
Note that the token bucket mechanism used for traffic shaping has both a token bucket and a data buffer,
or queue; if it did not have a data buffer, it would be a policer. For traffic shaping, packets that arrive that
cannot be sent immediately are delayed in the data buffer.
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QoS Overview
For traffic shaping, a token bucket permits burstiness but bounds it. It guarantees that the burstiness is
bounded so that the flow will never send faster than the token bucket capacity, divided by the time
interval, plus the established rate at which tokens are placed in the token bucket. See the following
formula:
(token bucket capacity in bits / time interval in seconds) + established rate in bps = maximum flow speed
in bps
This method of bounding burstiness also guarantees that the long-term transmission rate will not exceed
the established rate at which tokens are placed in the bucket.
Policing Overview
Policing is a way of ensuring that no traffic exceeds the maximum rate (in bits/second) that you
configure, thus ensuring that no one traffic flow or class can take over the entire resource. When traffic
exceeds the maximum rate, the security appliance drops the excess traffic. Policing also sets the largest
single burst of traffic allowed.
Priority Queueing Overview
LLQ priority queueing lets you prioritize certain traffic flows (such as latency-sensitive traffic like voice
and video) ahead of other traffic.
The security appliance supports two types of priority queueing:
•
Standard priority queueing—Standard priority queueing uses an LLQ priority queue on an interface
(see the “Creating the Standard Priority Queue for an Interface” section on page 24-5), while all
other traffic goes into the “best effort” queue. Because queues are not of infinite size, they can fill
and overflow. When a queue is full, any additional packets cannot get into the queue and are
dropped. This is called tail drop. To avoid having the queue fill up, you can increase the queue buffer
size. You can also fine-tune the maximum number of packets allowed into the transmit queue. These
options let you control the latency and robustness of the priority queuing. Packets in the LLQ queue
are always transmitted before packets in the best effort queue.
•
Hierarchical priority queueing—Hierarchical priority queueing is used on interfaces on which you
enable a traffic shaping queue. A subset of the shaped traffic can be prioritized. The standard priority
queue is not used. See the following guidelines about hierarchical priority queueing:
– Priority packets are always queued at the head of the shape queue so they are always transmitted
ahead of other non-priority queued packets.
– Priority packets are never dropped from the shape queue unless the sustained rate of priority
traffic exceeds the shape rate.
– For IPSec-encrypted packets, you can only match traffic based on the DSCP or precedence
setting.
– IPSec-over-TCP is not supported for priority traffic classification.
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QoS Overview
Traffic Shaping Overview
Traffic shaping is used to match device and link speeds, thereby controlling packet loss, variable delay,
and link saturation, which can cause jitter and delay.
•
Traffic shaping must be applied to all outgoing traffic on a physical interface or in the case of the
ASA 5505, on a VLAN. You cannot configure traffic shaping for specific types of traffic.
•
Traffic shaping is implemented when packets are ready to be transmitted on an interface, so the rate
calculation is performed based on the actual size of a packet to be transmitted, including all the
possible overhead such as the IPSec header and L2 header.
•
The shaped traffic includes both through-the-box and from-the-box traffic.
•
The shape rate calculation is based on the standard token bucket algorithm. The token bucket size is
twice the Burst Size value. See the “What is a Token Bucket?” section on page 24-2.
•
When bursty traffic exceeds the specified shape rate, packets are queued and transmitted later.
Following are some characteristics regarding the shape queue (for information about hierarchical
priority queueing, see the “Priority Queueing Overview” section on page 24-3):
– The queue size is calculated based on the shape rate. The queue can hold the equivalent of
200-milliseconds worth of shape rate traffic, assuming a 1500-byte packet. The minimum queue
size is 64.
– When the queue limit is reached, packets are tail-dropped.
– Certain critical keep-alive packets such as OSPF Hello packets are never dropped.
– The time interval is derived by time_interval = burst_size / average_rate. The larger the time
interval is, the burstier the shaped traffic might be, and the longer the link might be idle. The
effect can be best understood using the following exaggerated example:
Average Rate = 1000000
Burst Size = 1000000
In the above example, the time interval is 1 second, which means, 1 Mbps of traffic can be
bursted out within the first 10 milliseconds of the 1-second interval on a 100 Mbps FE link and
leave the remaining 990 milliseconds idle without being able to send any packets until the next
time interval. So if there is delay-sensitive traffic such as voice traffic, the Burst Size should be
reduced compared to the average rate so the time interval is reduced.
How QoS Features Interact
You can configure each of the QoS features alone if desired for the security appliance. Often, though,
you configure multiple QoS features on the security appliance so you can prioritize some traffic, for
example, and prevent other traffic from causing bandwidth problems.
See the following supported feature combinations per interface:
•
Standard priority queuing (for specific traffic) + Policing (for the rest of the traffic).
You cannot configure priority queueing and policing for the same set of traffic.
•
Traffic shaping (for all traffic on an interface) + Hierarchical priority queueing (for a subset of
traffic).
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Creating the Standard Priority Queue for an Interface
You cannot configure traffic shaping and standard priority queueing for the same interface; only
hierarchical priority queueing is allowed. For example, if you configure standard priority queueing for
the global policy, and then configure traffic shaping for a specific interface, the feature you configured
last is rejected because the global policy overlaps the interface policy.
Typically, if you enable traffic shaping, you do not also enable policing for the same traffic, although the
security appliance does not restrict you from configuring this.
DSCP and DiffServ Preservation
•
DSCP markings are preserved on all traffic passing through the security appliance.
•
The security appliance does not locally mark/remark any classified traffic, but it honors the
Expedited Forwarding (EF) DSCP bits of every packet to determine if it requires “priority” handling
and will direct those packets to the LLQ.
•
DiffServ marking is preserved on packets when they traverse the service provider backbone so that
QoS can be applied in transit (QoS tunnel pre-classification).
Creating the Standard Priority Queue for an Interface
If you enable standard priority queueing for traffic on a physical interface, then you need to also create
the priority queue on each interface. Each physical interface uses two queues: one for priority traffic,
and the other for all other traffic. For the other traffic, you can optionally configure policing.
Note
The standard priority queue is not required for hierarchical priority queueing with traffic shaping; see
the “Priority Queueing Overview” section on page 24-3 for more information.
To create the priority queue, perform the following steps:
Step 1
To create the priority queue, enter the following command:
hostname(config)# priority-queue interface_name
Where the interface_name argument specifies the physical interface name on which you want to enable
the priority queue, or for the ASA 5505, the VLAN interface name.
Step 2
(Optional) To change the size of the priority queues, enter the following command:
hostname(config-priority-queue)# queue-limit number_of_packets
Because queues are not of infinite size, they can fill and overflow. When a queue is full, any additional
packets cannot get into the queue and are dropped (called tail drop). To avoid having the queue fill up,
you can use the queue-limit command to increase the queue buffer size.
The number_of_packets is the number of average, 256-byte packets that the specified interface can
transmit in a 500-ms interval. A packet that stays more than 500 ms in a network node might trigger a
timeout in the end-to-end application. Such a packet can be discarded in each network node.
The upper limit of the range of values for the queue-limit command is determined dynamically at run
time. To view this limit, enter queue-limit ? on the command line. The key determinants are the memory
needed to support the queues and the memory available on the device.
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The queue-limit that you specify affects both the higher priority low-latency queue and the best effort
queue.
Step 3
(Optional) To specify the depth of the priority queues, enter the following command:
hostname(config-priority-queue)# tx-ring-limit number_of_packets
This command sets the maximum number of low-latency or normal priority packets allowed into the
Ethernet transmit driver before the driver pushes back to the queues on the interface to let them buffer
packets until the congestion clears.
The number_of_packets is the number of maximum 1550-byte packets that the specified interface can
transmit in a 10-ms interval. This guarantees that the hardware-based transmit ring imposes no more than
10-ms of extra latency for a high-priority packet.
The upper limit of the range of values for the tx-ring-limit command is determined dynamically at run
time. To view this limit, enter tx-ring-limit ? on the command line. The key determinants are the
memory needed to support the queues and the memory available on the device.
The tx-ring-limit that you specify affects both the higher priority low-latency queue and the best-effort
queue.
The following example establishes a priority queue on interface “outside” (the GigabitEthernet0/1
interface), with the default queue-limit and tx-ring-limit.
hostname(config)# priority-queue outside
The following example establishes a priority queue on the interface “outside” (the GigabitEthernet0/1
interface), sets the queue-limit to 2048 packets, and sets the tx-ring-limit to 256:
hostname(config)# priority-queue outside
hostname(config-priority-queue)# queue-limit 2048
hostname(config-priority-queue)# tx-ring-limit 256
Identifying Traffic for QoS Using Class Maps
QoS is part of the Modular Policy Framework. See the Chapter 21, “Using Modular Policy Framework,”
for more information. In Modular Policy Framework, you identify the traffic on which you want to
enable QoS in a class map. This section includes the following topics:
•
Creating a QoS Class Map, page 24-6
•
QoS Class Map Examples, page 24-7
Creating a QoS Class Map
For priority traffic, identify only latency-sensitive traffic. For policing traffic, you can choose to police
all other traffic, or you can limit the traffic to certain types. For traffic shaping, all traffic on an interface
must be shaped.
To create the class maps for QoS traffic, see the class-map command in the “Identifying Traffic (Layer
3/4 Class Map)” section on page 21-4.
You can match traffic based on many characteristics, including access lists, tunnel groups, DSCP,
precedence, and more. See the following guidelines for configuring class maps for QoS:
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Identifying Traffic for QoS Using Class Maps
•
For traffic shaping, you can only use the class-default class map, which is automatically created by
the security appliance, and which matches all traffic.
•
You cannot use the class-default class map for priority traffic.
•
For hierarchical priority queueing, for IPSec-encrypted packets, you can only match traffic based on
the DSCP or precedence setting.
•
For hierarchical priority queueing, IPSec-over-TCP traffic is not supported.
QoS Class Map Examples
For example, in the following sequence, the class-map command classifies all non-tunneled TCP traffic,
using an access list named tcp_traffic:
hostname(config)# access-list tcp_traffic permit tcp any any
hostname(config)# class-map tcp_traffic
hostname(config-cmap)# match access-list tcp_traffic
In the following example, other, more specific match criteria are used for classifying traffic for specific,
security-related tunnel groups. These specific match criteria stipulate that a match on tunnel-group (in
this case, the previously-defined Tunnel-Group-1) is required as the first match characteristic to classify
traffic for a specific tunnel, and it allows for an additional match line to classify the traffic (IP differential
services code point, expedited forwarding).
hostname(config)# class-map TG1-voice
hostname(config-cmap)# match tunnel-group tunnel-grp1
hostname(config-cmap)# match dscp ef
In the following example, the class-map command classifies both tunneled and non-tunneled traffic
according to the traffic type:
hostname(config)# access-list tunneled extended permit ip 10.10.34.0 255.255.255.0
20.20.10.0 255.255.255.0
hostname(config)# access-list non-tunneled extended permit tcp any any
hostname(config)# tunnel-group tunnel-grp1 type IPSec_L2L
hostname(config)# class-map browse
hostname(config-cmap)# description "This class-map matches all non-tunneled tcp traffic."
hostname(config-cmap)# match access-list non-tunneled
hostname(config-cmap)#
hostname(config-cmap)#
tunnel-grp 1."
hostname(config-cmap)#
hostname(config-cmap)#
class-map TG1-voice
description "This class-map matches all dscp ef traffic for
hostname(config-cmap)#
hostname(config-cmap)#
tunnel-grp1."
hostname(config-cmap)#
hostname(config-cmap)#
class-map TG1-BestEffort
description "This class-map matches all best-effort traffic for
match dscp ef
match tunnel-group tunnel-grp1
match tunnel-group tunnel-grp1
match flow ip destination-address
The following example shows a way of policing a flow within a tunnel, provided the classed traffic is
not specified as a tunnel, but does go through the tunnel. In this example, 192.168.10.10 is the address
of the host machine on the private side of the remote tunnel, and the access list is named “host-over-l2l”.
By creating a class-map (named “host-specific”), you can then police the “host-specific” class before the
LAN-to-LAN connection polices the tunnel. In this example, the “host-specific” traffic is rate-limited
before the tunnel, then the tunnel is rate-limited:
hostname(config)# access-list host-over-l2l extended permit ip any host 192.168.10.10
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hostname(config)# class-map host-specific
hostname(config-cmap)# match access-list host-over-l2l
The following example builds on the configuration developed in the previous section. As in the previous
example, there are two named class-maps: tcp_traffic and TG1-voice. Adding a third class-map:
hostname(config)# class-map TG1-best-effort
hostname(config-cmap)# match tunnel-group Tunnel-Group-1
hostname(config-cmap)# match flow ip destination-address
provides a basis for defining a tunneled and non-tunneled QoS policy, as follows, which creates a simple
QoS policy for tunneled and non-tunneled traffic, assigning packets of the class TG1-voice to the low
latency queue and setting rate limits on the tcp_traffic and TG1-best-effort traffic flows.
Creating a Policy for Standard Priority Queueing and/or Policing
After you identify the traffic in “Identifying Traffic for QoS Using Class Maps” section on page 24-6,
you can create a policy map for an interface or globally for all interfaces that assigns QoS actions (and
other feature actions) to the traffic in the class map. (See the Chapter 21, “Using Modular Policy
Framework,” for information about other features. This chapter only discusses QoS.)
You can configure standard priority queueing and policing for different class maps within the same
policy map. See the “How QoS Features Interact” section on page 24-4 for information about valid QoS
configurations.
To create a policy map, perform the following steps:
Step 1
To add or edit a policy map, enter the following command:
hostname(config)# policy-map name
For example:
hostname(config)# policy-map QoS_policy
Step 2
To configure priority queueing, enter the following commands:
hostname(config-pmap)# class priority_map_name
hostname(config-pmap-c)# priority
where the priority_map_name is the class map you created for prioritized traffic in “Identifying Traffic
for QoS Using Class Maps” section on page 24-6.
For example:
hostname(config)# class-map priority-class
hostname(config-cmap)# match tunnel-group Tunnel-Group-1
hostname(config-cmap)# match dscp ef
hostname(config-cmap)# policy-map QoS_policy
hostname(config-pmap)# class priority_class
hostname(config-pmap-c)# priority
Step 3
To configure policing, enter the following commands:
hostname(config-pmap)# class policing_map_name
hostname(config-pmap-c)# police {output | input} conform-rate [conform-burst]
[conform-action [drop | transmit]] [exceed-action [drop | transmit]]
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where the policing_map_name is the class map you created for prioritized traffic in “Identifying Traffic
for QoS Using Class Maps” section on page 24-6.
The conform-burst argument specifies the maximum number of instantaneous bytes allowed in a
sustained burst before throttling to the conforming rate value, between 1000 and 512000000 bytes.
The conform-action keyword sets the action to take when the rate is less than the conform_burst value.
The conform-rate argument sets the rate limit for this traffic flow; between 8000 and 2000000000 bits
per second.
The drop keyword drops the packet.
The exceed-action keyword sets the action to take when the rate is between the conform-rate value and
the conform-burst value.
The input keyword enables policing of traffic flowing in the input direction.
The output keyword enables policing of traffic flowing in the output direction.
The transmit keyword transmits the packet.
For example:
hostname(config)# class-map policing-class
hostname(config-cmap)# match any
hostname(config-cmap)# policy-map QoS_policy
hostname(config-pmap)# class police_class
hostname(config-pmap-c)# police output 56000 10500
Step 4
To activate the policy map on one or more interfaces, enter the following command:
hostname(config)# service-policy policymap_name {global | interface interface_name}
Where global applies the policy map to all interfaces, and interface applies the policy to one interface.
Only one global policy is allowed. Interface service policies take precedence over the global service
policy for a given feature. For example, if you have a global policy with inspections, and an interface
policy with TCP normalization, then both inspections and TCP normalization are applied to the
interface. However, if you have a global policy with inspections, and an interface policy with
inspections, then only the interface policy inspections are applied to that interface.
In this example, the maximum rate for traffic of the tcp_traffic class is 56,000 bits/second and a
maximum burst size of 10,500 bytes per second. For the TC1-BestEffort class, the maximum rate is
200,000 bits/second, with a maximum burst of 37,500 bytes/second. Traffic in the TC1-voice class has
no policed maximum speed or burst rate because it belongs to a priority class:
hostname(config)# access-list tcp_traffic permit tcp any any
hostname(config)# class-map tcp_traffic
hostname(config-cmap)# match access-list tcp_traffic
hostname(config)# class-map TG1-voice
hostname(config-cmap)# match tunnel-group tunnel-grp1
hostname(config-cmap)# match dscp ef
hostname(config-cmap)# class-map TG1-BestEffort
hostname(config-cmap)# match tunnel-group tunnel-grp1
hostname(config-cmap)# match flow ip destination-address
hostname(config)# policy-map qos
hostname(config-pmap)# class tcp_traffic
hostname(config-pmap-c)# police output 56000 10500
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hostname(config-pmap-c)# class TG1-voice
hostname(config-pmap-c)# priority
hostname(config-pmap-c)# class TG1-best-effort
hostname(config-pmap-c)# police output 200000 37500
hostname(config-pmap-c)# class class-default
hostname(config-pmap-c)# police output 1000000 37500
hostname(config-pmap-c)# service-policy qos global
Creating a Policy for Traffic Shaping and Hierarchical Priority
Queueing
You can create a policy map for an interface or globally for all interfaces that assigns QoS actions (and
other feature actions) to the traffic in the class map. (See the Chapter 21, “Using Modular Policy
Framework,” for information about other features. This chapter only discusses QoS.)
You can configure traffic shaping for all traffic on an interface, and optionally hierarchical priority
queueing for a subset of latency-sensitive traffic. See the “How QoS Features Interact” section on
page 24-4 for information about valid QoS configurations.
If you want to configure hierarchical priority queueing, then first identify the traffic in “Identifying
Traffic for QoS Using Class Maps” section on page 24-6; traffic shaping always uses the class-default
class map, which is automatically available.
Note
One side-effect of priority queueing is packet re-ordering. For IPSec packets, out-of-order packets that
are not within the anti-replay window generate warning syslog messages. These warnings are false
alarms in the case of priority queueing. You can configure the IPSec anti-replay window size to avoid
possible false alarms. See the crypto ipsec security-association replay command in the Cisco Security
Appliance Command Reference.
To create a policy map, perform the following steps:
Step 1
(Optional) For hierarchical priority queueing, create a policy map that applies the priority queueing
action to a class map by entering the following commands:
hostname(config)# policy-map name
hostname(config-pmap)# class priority_map_name
hostname(config-pmap-c)# priority
where the priority_map_name is the class map you created for prioritized traffic in “Identifying Traffic
for QoS Using Class Maps” section on page 24-6.
For example:
hostname(config)# policy-map priority-sub-policy
hostname(config-pmap)# class priority-sub-map
hostname(config-pmap-c)# priority
Step 2
To add or edit a policy map for traffic shaping, enter the following command:
hostname(config)# policy-map name
For example:
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hostname(config)# policy-map shape_policy
Step 3
To configure traffic shaping, enter the following commands:
hostname(config-pmap)# class class-default
hostname(config-pmap-c)# shape average rate [burst_size]
where the average rate argument sets the average rate of traffic in bits per second over a given fixed time
period, between 64000 and 154400000. Specify a value that is a multiple of 8000. See the “Traffic
Shaping Overview” section on page 24-4 for more information about how the time period is calculated.
The burst_size argument sets the average burst size in bits that can be transmitted over a given fixed time
period, between 2048 and 154400000. Specify a value that is a multiple of 128. If you do not specify the
burst_size, the default value is equivalent to 4-milliseconds of traffic at the specified average rate. For
example, if the average rate is 1000000 bits per second, 4 ms worth = 1000000 * 4/1000 = 4000.
You can only identify the class-default class map, which is defined as match any, because the security
appliance requires all traffic to be matched for traffic shaping.
Step 4
(Optional) To configure hierarchical priority queueing, enter the following command:
hostname(config-pmap-c)# service-policy priority_policy_map_name
where the priority_policy_map_name is the policy map you created for prioritized traffic in Step 1.
For example:
hostname(config)# policy-map priority-sub-policy
hostname(config-pmap)# class priority-sub-map
hostname(config-pmap-c)# priority
hostname(config-pmap-c)# policy-map shape_policy
hostname(config-pmap)# class class-default
hostname(config-pmap-c)# shape
hostname(config-pmap-c)# service-policy priority-sub-policy
Step 5
To activate the policy map on an interface, enter the following command:
hostname(config)# service-policy policymap_name interface interface_name
Note
You cannot configure traffic shaping in the global policy.
The following example enables traffic shaping on the outside interface, and limits traffic to 2 Mbps;
priority queueing is enabled for VoIP traffic that is tagged with DSCP EF and AF13 and for IKE traffic:
hostname(config)# access-list ike permit udp any any eq 500
hostname(config)# class-map ike
hostname(config-cmap)# match access-list ike
hostname(config-cmap)# class-map voice_traffic
hostname(config-cmap)# match dscp EF AF13
hostname(config-cmap)# policy-map qos_class_policy
hostname(config-pmap)# class voice_traffic
hostname(config-pmap-c)# priority
hostname(config-pmap-c)# class ike
hostname(config-pmap-c)# priority
hostname(config-pmap-c)# policy-map qos_outside_policy
hostname(config-pmap)# class class-default
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Viewing QoS Statistics
hostname(config-pmap-c)# shape average 2000000 16000
hostname(config-pmap-c)# service-policy qos_class_policy
hostname(config-pmap-c)# service-policy qos_outside_policy interface outside
Viewing QoS Statistics
This section contains the following topics:
•
Viewing QoS Police Statistics, page 24-12
•
Viewing QoS Standard Priority Statistics, page 24-12
•
Viewing QoS Shaping Statistics, page 24-13
•
Viewing QoS Standard Priority Queue Statistics, page 24-14
Viewing QoS Police Statistics
To view the QoS statistics for traffic policing, use the show service-policy command with the police
keyword, in privileged EXEC mode:
hostname# show service-policy police
For example, the following command displays service policies that include the police command and the
related statistics; for example:
hostname# show service-policy police
Global policy:
Service-policy: global_fw_policy
Interface outside:
Service-policy: qos
Class-map: browse
police Interface outside:
cir 56000 bps, bc 10500 bytes
conformed 10065 packets, 12621510 bytes; actions: transmit
exceeded 499 packets, 625146 bytes; actions: drop
conformed 5600 bps, exceed 5016 bps
Class-map: cmap2
police Interface outside:
cir 200000 bps, bc 37500 bytes
conformed 17179 packets, 20614800 bytes; actions: transmit
exceeded 617 packets, 770718 bytes; actions: drop
conformed 198785 bps, exceed 2303 bps
Viewing QoS Standard Priority Statistics
To view statistics for service policies implementing the priority command, use the show service-policy
command with the priority keyword, in privileged EXEC mode:
hostname# show service-policy priority
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For example, the following command displays service policies that include the priority command and
the related statistics; for example:
hostname# show service-policy priority
Global policy:
Service-policy: global_fw_policy
Interface outside:
Service-policy: qos
Class-map: TG1-voice
Priority:
Interface outside: aggregate drop 0, aggregate transmit 9383
Note
“Aggregate drop” denotes the aggregated drop in this interface; “aggregate transmit” denotes the
aggregated number of transmitted packets in this interface.
Viewing QoS Shaping Statistics
To view statistics for service policies implementing the shape command, use the show service-policy
command with the shape keyword, in privileged EXEC mode:
hostname# show service-policy shape
The following sample output of the show service policy shape command includes service policies that
include the shape command and the related statistics; for example:
hostname# show service-policy shape
Interface outside
Service-policy: shape
Class-map: class-default
Queueing
queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/0/0
(pkts output/bytes output) 0/0
shape (average) cir 2000000, bc 8000, be 8000
The following sample output of the show service policy shape command includes service policies that
include the shape command and the service-policy command that calls the hierarchical priority policy
and the related statistics; for example:
hostname# show service-policy shape
Interface outside:
Service-policy: shape
Class-map: class-default
Queueing
queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/0/0
(pkts output/bytes output) 0/0
shape (average) cir 2000000, bc 16000, be 16000
Service-policy: voip
Class-map: voip
Queueing
queue limit 64 packets
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(queue depth/total drops/no-buffer drops) 0/0/0
(pkts output/bytes output) 0/0
Class-map: class-default
queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/0/0
(pkts output/bytes output) 0/0
Viewing QoS Standard Priority Queue Statistics
To display the priority-queue statistics for an interface, use the show priority-queue statistics command
in privileged EXEC mode. The results show the statistics for both the best-effort (BE) queue and the
low-latency queue (LLQ). The following example shows the use of the show priority-queue statistics
command for the interface named test, and the command output:
hostname# show priority-queue statistics test
Priority-Queue Statistics interface test
Queue Type
Packets Dropped
Packets Transmit
Packets Enqueued
Current Q Length
Max Q Length
=
=
=
=
=
=
BE
0
0
0
0
0
Queue Type
Packets Dropped
Packets Transmit
Packets Enqueued
Current Q Length
Max Q Length
hostname#
=
=
=
=
=
=
LLQ
0
0
0
0
0
In this statistical report, the meaning of the line items is as follows:
•
“Packets Dropped” denotes the overall number of packets that have been dropped in this queue.
•
“Packets Transmit” denotes the overall number of packets that have been transmitted in this queue.
•
“Packets Enqueued” denotes the overall number of packets that have been queued in this queue.
•
“Current Q Length” denotes the current depth of this queue.
•
“Max Q Length” denotes the maximum depth that ever occurred in this queue.
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25
Configuring Application Layer Protocol
Inspection
This chapter describes how to configure application layer protocol inspection. Inspection engines are
required for services that embed IP addressing information in the user data packet or that open secondary
channels on dynamically assigned ports. These protocols require the security appliance to do a deep
packet inspection instead of passing the packet through the fast path (see the “Stateful Inspection
Overview” section on page 1-4 for more information about the fast path). As a result, inspection engines
can affect overall throughput.
Several common inspection engines are enabled on the security appliance by default, but you might need
to enable others depending on your network. This chapter includes the following sections:
•
Inspection Engine Overview, page 25-2
– When to Use Application Protocol Inspection, page 25-2
– Inspection Limitations, page 25-2
– Default Inspection Policy, page 25-3
•
Configuring Application Inspection, page 25-5
•
CTIQBE Inspection, page 25-9
•
DCERPC Inspection, page 25-11
•
DNS Inspection, page 25-13
•
ESMTP Inspection, page 25-23
•
FTP Inspection, page 25-26
•
GTP Inspection, page 25-32
•
H.323 Inspection, page 25-38
•
HTTP Inspection, page 25-44
•
Instant Messaging Inspection, page 25-49
•
ICMP Inspection, page 25-52
•
ICMP Error Inspection, page 25-52
•
ILS Inspection, page 25-53
•
IPSec Pass Through Inspection, page 25-54
•
MGCP Inspection, page 25-56
•
NetBIOS Inspection, page 25-60
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Inspection Engine Overview
•
PPTP Inspection, page 25-62
•
RADIUS Accounting Inspection, page 25-62
•
RSH Inspection, page 25-63
•
RTSP Inspection, page 25-63
•
SIP Inspection, page 25-65
•
Skinny (SCCP) Inspection, page 25-71
•
SMTP and Extended SMTP Inspection, page 25-74
•
SNMP Inspection, page 25-76
•
SQL*Net Inspection, page 25-76
•
Sun RPC Inspection, page 25-77
•
TFTP Inspection, page 25-79
•
XDMCP Inspection, page 25-80
Inspection Engine Overview
This section includes the following topics:
•
When to Use Application Protocol Inspection, page 25-2
•
Inspection Limitations, page 25-2
•
Default Inspection Policy, page 25-3
When to Use Application Protocol Inspection
When a user establishes a connection, the security appliance checks the packet against access lists,
creates an address translation, and creates an entry for the session in the fast path, so that further packets
can bypass time-consuming checks. However, the fast path relies on predictable port numbers and does
not perform address translations inside a packet.
Many protocols open secondary TCP or UDP ports. The initial session on a well-known port is used to
negotiate dynamically assigned port numbers.
Other applications embed an IP address in the packet that needs to match the source address that is
normally translated when it goes through the security appliance.
If you use applications like these, then you need to enable application inspection.
When you enable application inspection for a service that embeds IP addresses, the security appliance
translates embedded addresses and updates any checksum or other fields that are affected by the
translation.
When you enable application inspection for a service that uses dynamically assigned ports, the security
appliance monitors sessions to identify the dynamic port assignments, and permits data exchange on
these ports for the duration of the specific session.
Inspection Limitations
See the following limitations for application protocol inspection:
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Inspection Engine Overview
•
State information for multimedia sessions that require inspection are not passed over the state link
for stateful failover. The exception is GTP, which is replicated over the state link.
•
Some inspection engines do not support PAT, NAT, outside NAT, or NAT between same security
interfaces. See “Default Inspection Policy” for more information about NAT support.
Default Inspection Policy
By default, the configuration includes a policy that matches all default application inspection traffic and
applies inspection to the traffic on all interfaces (a global policy). Default application inspection traffic
includes traffic to the default ports for each protocol. You can only apply one global policy, so if you
want to alter the global policy, for example, to apply inspection to non-standard ports, or to add
inspections that are not enabled by default, you need to either edit the default policy or disable it and
apply a new one.
Table 25-1 lists all inspections supported, the default ports used in the default class map, and the
inspection engines that are on by default, shown in bold. This table also notes any NAT limitations.
Table 25-1
Supported Application Inspection Engines
Application1
Default Port NAT Limitations
Standards2
Comments
CTIQBE
TCP/2748
—
—
—
DNS over UDP
UDP/53
No NAT support is available for RFC 1123
name resolution through
WINS.
No PTR records are changed.
FTP
TCP/21
—
RFC 959
—
GTP
UDP/3386
UDP/2123
—
—
Requires a special license.
No NAT on same security
H.323 H.225 and TCP/1720
RAS
UDP/1718 interfaces.
UDP (RAS)
No static PAT.
1718-1719
ITU-T H.323,
H.245, H225.0,
Q.931, Q.932
—
HTTP
TCP/80
—
RFC 2616
Beware of MTU limitations stripping
ActiveX and Java. If the MTU is too
small to allow the Java or ActiveX tag to
be included in one packet, stripping
may not occur.
ICMP
—
—
—
All ICMP traffic is matched in the
default class map.
ICMP ERROR
—
—
—
All ICMP traffic is matched in the
default class map.
ILS (LDAP)
TCP/389
No PAT.
—
—
MGCP
UDP/2427,
2727
—
RFC 2705bis-05
—
NetBIOS Name
Server over IP
UDP/137,
—
138 (Source
ports)
—
NetBIOS is supported by performing
NAT of the packets for NBNS UDP port
137 and NBDS UDP port 138.
PPTP
TCP/1723
RFC 2637
—
—
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Table 25-1
Supported Application Inspection Engines (continued)
Application1
Default Port NAT Limitations
Standards2
Comments
RADIUS
Accounting
1646
—
RFC 2865
—
RSH
TCP/514
No PAT
Berkeley UNIX
—
RTSP
TCP/554
No PAT.
No outside NAT.
RFC 2326, 2327, No handling for HTTP cloaking.
1889
TCP/5060
UDP/5060
No outside NAT.
RFC 3261
—
SKINNY
(SCCP)
TCP/2000
No outside NAT.
—
Does not handle TFTP uploaded Cisco
IP Phone configurations under certain
circumstances.
SMTP and
ESMTP
TCP/25
—
RFC 821, 1123
—
SNMP
UDP/161,
162
No NAT or PAT.
RFC 1155, 1157, v.2 RFC 1902-1908; v.3 RFC
1212, 1213, 1215 2570-2580.
SQL*Net
TCP/1521
—
—
v.1 and v.2.
Sun RPC over
UDP and TCP
UDP/111
No NAT or PAT.
—
The default class map includes UDP
port 111; if you want to enable Sun RPC
inspection for TCP port 111, you need
to create a new class map that matches
TCP port 111, add the class to the
policy, and then apply the inspect
sunrpc command to that class.
TFTP
UDP/69
—
RFC 1350
Payload IP addresses are not translated.
XDCMP
UDP/177
No NAT or PAT.
—
—
SIP
No NAT on same security
interfaces.
No NAT on same security
interfaces.
1. Inspection engines that are enabled by default for the default port are in bold.
2. The security appliance is in compliance with these standards, but it does not enforce compliance on packets being inspected. For example, FTP commands
are supposed to be in a particular order, but the security appliance does not enforce the order.
The default policy configuration includes the following commands:
class-map inspection_default
match default-inspection-traffic
policy-map type inspect dns preset_dns_map
parameters
message-length maximum 512
policy-map global_policy
class inspection_default
inspect dns preset_dns_map
inspect ftp
inspect h323 h225
inspect h323 ras
inspect rsh
inspect rtsp
inspect esmtp
inspect sqlnet
inspect skinny
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Configuring Application Inspection
inspect sunrpc
inspect xdmcp
inspect sip
inspect netbios
inspect tftp
service-policy global_policy global
Configuring Application Inspection
This feature uses Modular Policy Framework, so that implementing application inspection consists of
identifying traffic, applying inspections to the traffic, and activating inspections on an interface. For
some applications, you can perform special actions when you enable inspection. See Chapter 21, “Using
Modular Policy Framework,” for more information.
Inspection is enabled by default for some applications. See the “Default Inspection Policy” section for
more information. Use this section to modify your inspection policy.
To configure application inspection, perform the following steps:
Step 1
To identify the traffic to which you want to apply inspections, add either a Layer 3/4 class map for
through traffic or a Layer 3/4 class map for management traffic. See the “Creating a Layer 3/4 Class Map
for Through Traffic” section on page 21-5 and “Creating a Layer 3/4 Class Map for Management
Traffic” section on page 21-7 for detailed information. The management Layer 3/4 class map can be used
only with the RADIUS accounting inspection.
The default Layer 3/4 class map for through traffic is called “inspection_default.” It matches traffic using
a special match command, match default-inspection-traffic, to match the default ports for each
application protocol.
You can specify a match access-list command along with the match default-inspection-traffic
command to narrow the matched traffic to specific IP addresses. Because the match
default-inspection-traffic command specifies the ports to match, any ports in the access list are ignored.
If you want to match non-standard ports, then create a new class map for the non-standard ports. See the
“Default Inspection Policy” section on page 25-3 for the standard ports for each inspection engine. You
can combine multiple class maps in the same policy if desired, so you can create one class map to match
certain traffic, and another to match different traffic. However, if traffic matches a class map that
contains an inspection command, and then matches another class map that also has an inspection
command, only the first matching class is used. For example, SNMP matches the inspection_default
class. To enable SNMP inspection, enable SNMP inspection for the default class in Step 5. Do not add
another class that matches SNMP.
For example, to limit inspection to traffic from 10.1.1.0 to 192.168.1.0 using the default class map, enter
the following commands:
hostname(config)# access-list inspect extended permit ip 10.1.1.0 255.255.255.0
192.168.1.0 255.255.255.0
hostname(config)# class-map inspection_default
hostname(config-cmap)# match access-list inspect
View the entire class map using the following command:
hostname(config-cmap)# show running-config class-map inspection_default
!
class-map inspection_default
match default-inspection-traffic
match access-list inspect
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Configuring Application Inspection
!
To inspect FTP traffic on port 21 as well as 1056 (a non-standard port), create an access list that specifies
the ports, and assign it to a new class map:
hostname(config)# access-list ftp_inspect extended permit tcp any any eq 21
hostname(config)# access-list ftp_inspect extended permit tcp any any eq 1056
hostname(config)# class-map new_inspection
hostname(config-cmap)# match access-list ftp_inspect
Step 2
Step 3
(Optional) Some inspection engines let you control additional parameters when you apply the inspection
to the traffic. See the following sections to configure an inspection policy map for your application:
•
DCERPC—See the “Configuring a DCERPC Inspection Policy Map for Additional Inspection
Control” section on page 25-12
•
DNS—See the “Configuring a DNS Inspection Policy Map for Additional Inspection Control”
section on page 25-20
•
ESMTP—See the “Configuring an ESMTP Inspection Policy Map for Additional Inspection
Control” section on page 25-24
•
FTP—See the “Configuring an FTP Inspection Policy Map for Additional Inspection Control”
section on page 25-28.
•
GTP—See the “Configuring a GTP Inspection Policy Map for Additional Inspection Control”
section on page 25-33.
•
H323—See the “Configuring an H.323 Inspection Policy Map for Additional Inspection Control”
section on page 25-40
•
HTTP—See the “Configuring an HTTP Inspection Policy Map for Additional Inspection Control”
section on page 25-45.
•
Instant Messaging—See the “Configuring an Instant Messaging Inspection Policy Map for
Additional Inspection Control” section on page 25-49
•
MGCP—See the “Configuring an MGCP Inspection Policy Map for Additional Inspection Control”
section on page 25-58.
•
NetBIOS—See the “Configuring a NetBIOS Inspection Policy Map for Additional Inspection
Control” section on page 25-60
•
RADIUS Accounting—See the “Configuring a RADIUS Inspection Policy Map for Additional
Inspection Control” section on page 25-63
•
SIP—See the “Configuring a SIP Inspection Policy Map for Additional Inspection Control” section
on page 25-66
•
Skinny—See the “Configuring a Skinny (SCCP) Inspection Policy Map for Additional Inspection
Control” section on page 25-73
•
SNMP—See the “SNMP Inspection” section on page 25-76.
To add or edit a Layer 3/4 policy map that sets the actions to take with the class map traffic, enter the
following command:
hostname(config)# policy-map name
hostname(config-pmap)#
The default policy map is called “global_policy.” This policy map includes the default inspections listed
in the “Default Inspection Policy” section on page 25-3. If you want to modify the default policy (for
example, to add or delete an inspection, or to identify an additional class map for your actions), then
enter global_policy as the name.
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Step 4
To identify the class map from Step 1 to which you want to assign an action, enter the following
command:
hostname(config-pmap)# class class_map_name
hostname(config-pmap-c)#
If you are editing the default policy map, it includes the inspection_default class map. You can edit the
actions for this class by entering inspection_default as the name. To add an additional class map to this
policy map, identify a different name. You can combine multiple class maps in the same policy if desired,
so you can create one class map to match certain traffic, and another to match different traffic. However,
if traffic matches a class map that contains an inspection command, and then matches another class map
that also has an inspection command, only the first matching class is used. For example, SNMP matches
the inspection_default class map.To enable SNMP inspection, enable SNMP inspection for the default
class in Step 5. Do not add another class that matches SNMP.
Step 5
Enable application inspection by entering the following command:
hostname(config-pmap-c)# inspect protocol
The protocol is one of the following values:
Table 25-2
Protocol Keywords
Keywords
Notes
ctiqbe
—
dcerpc [map_name]
If you added a DCERPC inspection policy map according to
“Configuring a DCERPC Inspection Policy Map for
Additional Inspection Control” section on page 25-12,
identify the map name in this command.
dns [map_name]
If you added a DNS inspection policy map according to
“Configuring a DNS Inspection Policy Map for Additional
Inspection Control” section on page 25-20, identify the map
name in this command. The default DNS inspection policy
map name is “preset_dns_map.” The default inspection
policy map sets the maximum DNS packet length to 512
bytes.
esmtp [map_name]
If you added an ESMTP inspection policy map according to
“Configuring an ESMTP Inspection Policy Map for
Additional Inspection Control” section on page 25-24,
identify the map name in this command.
ftp [strict [map_name]]
Use the strict keyword to increase the security of protected
networks by preventing web browsers from sending
embedded commands in FTP requests. See the “Using the
strict Option” section on page 25-27 for more information.
If you added an FTP inspection policy map according to
“Configuring an FTP Inspection Policy Map for Additional
Inspection Control” section on page 25-28, identify the map
name in this command.
gtp [map_name]
If you added a GTP inspection policy map according to the
“Configuring a GTP Inspection Policy Map for Additional
Inspection Control” section on page 25-33, identify the map
name in this command.
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Table 25-2
Protocol Keywords
Keywords
Notes
h323 h225 [map_name]
If you added an H323 inspection policy map according to
“Configuring an H.323 Inspection Policy Map for
Additional Inspection Control” section on page 25-40,
identify the map name in this command.
h323 ras [map_name]
If you added an H323 inspection policy map according to
“Configuring an H.323 Inspection Policy Map for
Additional Inspection Control” section on page 25-40,
identify the map name in this command.
http [map_name]
If you added an HTTP inspection policy map according to
the “Configuring an HTTP Inspection Policy Map for
Additional Inspection Control” section on page 25-45,
identify the map name in this command.
icmp
—
icmp error
—
ils
—
im [map_name]
If you added an Instant Messaging inspection policy map
according to “Configuring an Instant Messaging Inspection
Policy Map for Additional Inspection Control” section on
page 25-49, identify the map name in this command.
mgcp [map_name]
If you added an MGCP inspection policy map according to
“Configuring an MGCP Inspection Policy Map for
Additional Inspection Control” section on page 25-58,
identify the map name in this command.
netbios [map_name]
If you added a NetBIOS inspection policy map according to
“Configuring a NetBIOS Inspection Policy Map for
Additional Inspection Control” section on page 25-60,
identify the map name in this command.
pptp
—
radius-accounting [map_name]
The radius-accounting keyword is only available for a
management class map. See the “Creating a Layer 3/4 Class
Map for Management Traffic” section on page 21-7 for more
information about creating a management class map.
If you added a RADIUS accounting inspection policy map
according to “Configuring a RADIUS Inspection Policy
Map for Additional Inspection Control” section on
page 25-63, identify the map name in this command.
rsh
—
rtsp
—
sip [map_name]
If you added a SIP inspection policy map according to
“Configuring a SIP Inspection Policy Map for Additional
Inspection Control” section on page 25-66, identify the map
name in this command.
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Table 25-2
Step 6
Protocol Keywords
Keywords
Notes
skinny [map_name]
If you added a Skinny inspection policy map according to
“Configuring a Skinny (SCCP) Inspection Policy Map for
Additional Inspection Control” section on page 25-73,
identify the map name in this command.
snmp [map_name]
If you added an SNMP inspection policy map according to
“SNMP Inspection” section on page 25-76, identify the map
name in this command.
sqlnet
—
sunrpc
The default class map includes UDP port 111; if you want to
enable Sun RPC inspection for TCP port 111, you need to
create a new class map that matches TCP port 111, add the
class to the policy, and then apply the inspect sunrpc
command to that class.
tftp
—
xdmcp
—
To activate the policy map on one or more interfaces, enter the following command:
hostname(config)# service-policy policymap_name {global | interface interface_name}
Where global applies the policy map to all interfaces, and interface applies the policy to one interface.
By default, the default policy map, “global_policy,” is applied globally. Only one global policy is
allowed. You can override the global policy on an interface by applying a service policy to that interface.
You can only apply one policy map to each interface.
CTIQBE Inspection
This section describes CTIQBE application inspection. This section includes the following topics:
•
CTIQBE Inspection Overview, page 25-9
•
Limitations and Restrictions, page 25-10
•
Verifying and Monitoring CTIQBE Inspection, page 25-10
CTIQBE Inspection Overview
CTIQBE protocol inspection supports NAT, PAT, and bidirectional NAT. This enables Cisco IP
SoftPhone and other Cisco TAPI/JTAPI applications to work successfully with Cisco CallManager for
call setup across the security appliance.
TAPI and JTAPI are used by many Cisco VoIP applications. CTIQBE is used by Cisco TSP to
communicate with Cisco CallManager.
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Limitations and Restrictions
The following summarizes limitations that apply when using CTIQBE application inspection:
•
CTIQBE application inspection does not support configurations with the alias command.
•
Stateful failover of CTIQBE calls is not supported.
•
Entering the debug ctiqbe command may delay message transmission, which may have a
performance impact in a real-time environment. When you enable this debugging or logging and
Cisco IP SoftPhone seems unable to complete call setup through the security appliance, increase the
timeout values in the Cisco TSP settings on the system running Cisco IP SoftPhone.
The following summarizes special considerations when using CTIQBE application inspection in specific
scenarios:
•
If two Cisco IP SoftPhones are registered with different Cisco CallManagers, which are connected
to different interfaces of the security appliance, calls between these two phones fails.
•
When Cisco CallManager is located on the higher security interface compared to
Cisco IP SoftPhones, if NAT or outside NAT is required for the Cisco CallManager IP address, the
mapping must be static as Cisco IP SoftPhone requires the Cisco CallManager IP address to be
specified explicitly in its Cisco TSP configuration on the PC.
•
When using PAT or Outside PAT, if the Cisco CallManager IP address is to be translated, its TCP
port 2748 must be statically mapped to the same port of the PAT (interface) address for Cisco IP
SoftPhone registrations to succeed. The CTIQBE listening port (TCP 2748) is fixed and is not
user-configurable on Cisco CallManager, Cisco IP SoftPhone, or Cisco TSP.
Verifying and Monitoring CTIQBE Inspection
The show ctiqbe command displays information regarding the CTIQBE sessions established across the
security appliance. It shows information about the media connections allocated by the CTIQBE
inspection engine.
The following is sample output from the show ctiqbe command under the following conditions. There
is only one active CTIQBE session setup across the security appliance. It is established between an
internal CTI device (for example, a Cisco IP SoftPhone) at local address 10.0.0.99 and an external Cisco
CallManager at 172.29.1.77, where TCP port 2748 is the Cisco CallManager. The heartbeat interval for
the session is 120 seconds.
hostname# # show ctiqbe
Total: 1
LOCAL
FOREIGN
STATE
HEARTBEAT
--------------------------------------------------------------1
10.0.0.99/1117 172.29.1.77/2748
1
120
---------------------------------------------RTP/RTCP: PAT xlates: mapped to 172.29.1.99(1028 - 1029)
---------------------------------------------MEDIA: Device ID 27
Call ID 0
Foreign 172.29.1.99
(1028 - 1029)
Local
172.29.1.88
(26822 - 26823)
----------------------------------------------
The CTI device has already registered with the CallManager. The device internal address and RTP
listening port is PATed to 172.29.1.99 UDP port 1028. Its RTCP listening port is PATed to UDP 1029.
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The line beginning with RTP/RTCP: PAT xlates: appears only if an internal CTI device has registered
with an external CallManager and the CTI device address and ports are PATed to that external interface.
This line does not appear if the CallManager is located on an internal interface, or if the internal CTI
device address and ports are translated to the same external interface that is used by the CallManager.
The output indicates a call has been established between this CTI device and another phone at
172.29.1.88. The RTP and RTCP listening ports of the other phone are UDP 26822 and 26823. The other
phone locates on the same interface as the CallManager because the security appliance does not maintain
a CTIQBE session record associated with the second phone and CallManager. The active call leg on the
CTI device side can be identified with Device ID 27 and Call ID 0.
The following is sample output from the show xlate debug command for these CTIBQE connections:
hostname# show xlate debug
3 in use, 3 most used
Flags: D - DNS, d - dump, I - identity, i - inside, n - no random,
r - portmap, s - static
TCP PAT from inside:10.0.0.99/1117 to outside:172.29.1.99/1025 flags ri idle 0:00:22
timeout 0:00:30
UDP PAT from inside:10.0.0.99/16908 to outside:172.29.1.99/1028 flags ri idle 0:00:00
timeout 0:04:10
UDP PAT from inside:10.0.0.99/16909 to outside:172.29.1.99/1029 flags ri idle 0:00:23
timeout 0:04:10
The show conn state ctiqbe command displays the status of CTIQBE connections. In the output, the
media connections allocated by the CTIQBE inspection engine are denoted by a ‘C’ flag. The following
is sample output from the show conn state ctiqbe command:
hostname# show conn state ctiqbe
1 in use, 10 most used
hostname# show conn state ctiqbe detail
1 in use, 10 most used
Flags: A - awaiting inside ACK to SYN, a - awaiting outside ACK to SYN,
B - initial SYN from outside, C - CTIQBE media, D - DNS, d - dump,
E - outside back connection, F - outside FIN, f - inside FIN,
G - group, g - MGCP, H - H.323, h - H.225.0, I - inbound data,
i - incomplete, J - GTP, j - GTP data, k - Skinny media,
M - SMTP data, m - SIP media, O - outbound data, P - inside back connection,
q - SQL*Net data, R - outside acknowledged FIN,
R - UDP RPC, r - inside acknowledged FIN, S - awaiting inside SYN,
s - awaiting outside SYN, T - SIP, t - SIP transient, U - up
DCERPC Inspection
This section describes the DCERPC inspection engine. This section includes the following topics:
•
DCERPC Overview, page 25-11
•
Configuring a DCERPC Inspection Policy Map for Additional Inspection Control, page 25-12
DCERPC Overview
DCERPC is a protocol widely used by Microsoft distributed client and server applications that allows
software clients to execute programs on a server remotely.
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This typically involves a client querying a server called the Endpoint Mapper listening on a well known
port number for the dynamically allocated network information of a required service. The client then sets
up a secondary connection to the server instance providing the service. The security appliance allows the
appropriate port number and network address and also applies NAT, if needed, for the secondary
connection.
DCERPC inspect maps inspect for native TCP communication between the EPM and client on well
known TCP port 135. Map and lookup operations of the EPM are supported for clients. Client and server
can be located in any security zone. The embedded server IP address and Port number are received from
the applicable EPM response messages. Since a client may attempt multiple connections to the server
port returned by EPM, multiple use of pinholes are allowed, which have user configurable timeouts.
Configuring a DCERPC Inspection Policy Map for Additional Inspection Control
To specify additional DCERPC inspection parameters, create a DCERPC inspection policy map. You can
then apply the inspection policy map when you enable DCERPC inspection according to the
“Configuring Application Inspection” section on page 25-5.
To create a DCERPC inspection policy map, perform the following steps:
Step 1
Create a DCERPC inspection policy map, enter the following command:
hostname(config)# policy-map type inspect dcerpc policy_map_name
hostname(config-pmap)#
Where the policy_map_name is the name of the policy map. The CLI enters policy-map configuration
mode.
Step 2
(Optional) To add a description to the policy map, enter the following command:
hostname(config-pmap)# description string
Step 3
To configure parameters that affect the inspection engine, perform the following steps:
a.
To enter parameters configuration mode, enter the following command:
hostname(config-pmap)# parameters
hostname(config-pmap-p)#
b.
To configure the timeout for DCERPC pinholes and override the global system pinhole timeout of
two minutes, enter the following command:
hostname(config-pmap-p)# timeout pinhole hh:mm:ss
Where the hh:mm:ss argument is the timeout for pinhole connections. Value is between 0:0:1 and
1193:0:0.
c.
To configure options for the endpoint mapper traffic, enter the following command:
hostname(config-pmap-p)# endpoint-mapper [service-only] [lookup-operation
[timeout hh:mm:ss]]
Where the hh:mm:ss argument is the timeout for pinholes generated from the lookup operation. If
no timeout is configured for the lookup operation, the timeout pinhole command or the default is
used. The epm-service-only keyword enforces endpoint mapper service during binding so that only
its service traffic is processed. The lookup-operation keyword enables the lookup operation of the
endpoint mapper service.
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The following example shows how to define a DCERPC inspection policy map with the timeout
configured for DCERPC pinholes.
hostname(config)# policy-map type inspect dcerpc dcerpc_map
hostname(config-pmap)# timeout pinhole 0:10:00
hostname(config)# class-map dcerpc
hostname(config-cmap)# match port tcp eq 135
hostname(config)# policy-map global-policy
hostname(config-pmap)# class dcerpc
hostname(config-pmap-c)# inspect msrpc dcerpc-map
hostname(config)# service-policy global-policy global
DNS Inspection
This section describes DNS application inspection. This section includes the following topics:
•
How DNS Application Inspection Works, page 25-13
•
How DNS Rewrite Works, page 25-14
•
Configuring DNS Rewrite, page 25-15
•
Verifying and Monitoring DNS Inspection, page 25-20
How DNS Application Inspection Works
The security appliance tears down the DNS session associated with a DNS query as soon as the DNS
reply is forwarded by the security appliance. The security appliance also monitors the message exchange
to ensure that the ID of the DNS reply matches the ID of the DNS query.
When DNS inspection is enabled, which is the default, the security appliance performs the following
additional tasks:
•
Translates the DNS record based on the configuration completed using the alias, static and nat
commands (DNS Rewrite). Translation only applies to the A-record in the DNS reply; therefore,
DNS Rewrite does not affect reverse lookups, which request the PTR record.
Note
DNS Rewrite is not applicable for PAT because multiple PAT rules are applicable for each
A-record and the PAT rule to use is ambiguous.
•
Enforces the maximum DNS message length (the default is 512 bytes and the maximum length is
65535 bytes). The security appliance performs reassembly as needed to verify that the packet length
is less than the maximum length configured. The security appliance drops the packet if it exceeds
the maximum length.
Note
•
If you enter the inspect dns command without the maximum-length option, DNS packet size
is not checked
Enforces a domain-name length of 255 bytes and a label length of 63 bytes.
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•
Verifies the integrity of the domain-name referred to by the pointer if compression pointers are
encountered in the DNS message.
•
Checks to see if a compression pointer loop exists.
A single connection is created for multiple DNS sessions, as long as they are between the same two
hosts, and the sessions have the same 5-tuple (source/destination IP address, source/destination port, and
protocol). DNS identification is tracked by app_id, and the idle timer for each app_id runs
independently.
Because the app_id expires independently, a legitimate DNS response can only pass through the security
appliance within a limited period of time and there is no resource build-up. However, if you enter the
show conn command, you will see the idle timer of a DNS connection being reset by a new DNS session.
This is due to the nature of the shared DNS connection and is by design.
How DNS Rewrite Works
When DNS inspection is enabled, DNS rewrite provides full support for NAT of DNS messages
originating from any interface.
If a client on an inside network requests DNS resolution of an inside address from a DNS server on an
outside interface, the DNS A-record is translated correctly. If the DNS inspection engine is disabled, the
A-record is not translated.
As long as DNS inspection remains enabled, you can configure DNS rewrite using the alias, static, or
nat commands. For details about the configuration required see the “Configuring DNS Rewrite” section
on page 25-15.
DNS Rewrite performs two functions:
•
Translating a public address (the routable or “mapped” address) in a DNS reply to a private address
(the “real” address) when the DNS client is on a private interface.
•
Translating a private address to a public address when the DNS client is on the public interface.
In Figure 25-1, the DNS server resides on the external (ISP) network The real address of the server
(192.168.100.1) has been mapped using the static command to the ISP-assigned address
(209.165.200.5). When a web client on the inside interface attempts to access the web server with the
URL http://server.example.com, the host running the web client sends a DNS request to the DNS server
to resolve the IP address of the web server. The security appliance translates the non-routable source
address in the IP header and forwards the request to the ISP network on its outside interface. When the
DNS reply is returned, the security appliance applies address translation not only to the destination
address, but also to the embedded IP address of the web server, which is contained in the A-record in the
DNS reply. As a result, the web client on the inside network gets the correct address for connecting to
the web server on the inside network. For configuration instructions for scenarios similar to this one, see
the “Configuring DNS Rewrite with Two NAT Zones” section on page 25-16.
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Figure 25-1
Translating the Address in a DNS Reply (DNS Rewrite)
DNS server
server.example.com IN A 209.165.200.5
Web server
server.example.com
192.168.100.1
ISP Internet
132406
Security appliance
192.168.100.1IN A 209.165.200.5
Web client
http://server.example.com
192.168.100.2
DNS rewrite also works if the client making the DNS request is on a DMZ network and the DNS server
is on an inside interface. For an illustration and configuration instructions for this scenario, see the “DNS
Rewrite with Three NAT Zones” section on page 25-17.
Configuring DNS Rewrite
You configure DNS rewrite using the alias, static, or nat commands. The alias and static command can
be used interchangeably; however, we recommend using the static command for new deployments
because it is more precise and unambiguous. Also, DNS rewrite is optional when using the static
command.
This section describes how to use the alias and static commands to configure DNS rewrite. It provides
configuration procedures for using the static command in a simple scenario and in a more complex
scenario. Using the nat command is similar to using the static command except that DNS Rewrite is
based on dynamic translation instead of a static mapping.
This section includes the following topics:
•
Using the Static Command for DNS Rewrite, page 25-15
•
Using the Static Command for DNS Rewrite, page 25-15
•
Configuring DNS Rewrite with Two NAT Zones, page 25-16
•
DNS Rewrite with Three NAT Zones, page 25-17
•
Configuring DNS Rewrite with Three NAT Zones, page 25-19
For detailed syntax and additional functions for the alias, nat, and static command, see the appropriate
command page in the Cisco Security Appliance Command Reference.
Using the Static Command for DNS Rewrite
The static command causes addresses on an IP network residing on a specific interface to be translated
into addresses on another IP network on a different interface. The syntax for this command is as follows:
hostname(config)# static (real_ifc,mapped_ifc) mapped-address real-address dns
The following example specifies that the address 192.168.100.10 on the inside interface is translated into
209.165.200.5 on the outside interface:
hostname(config)# static (inside,outside) 209.165.200.225 192.168.100.10 dns
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Note
Using the nat command is similar to using the static command except that DNS Rewrite is based on
dynamic translation instead of a static mapping.
Using the Alias Command for DNS Rewrite
The alias command causes the security appliance to translate addresses on an IP network residing on any
interface into addresses on another IP network connected through a different interface. The syntax for
this command is as follows:
hostname(config)# alias (interface_name) mapped-address real-address
The following example specifies that the real address (192.168.100.10) on any interface except the inside
interface will be translated to the mapped address (209.165.200.225) on the inside interface. Notice that
the location of 192.168.100.10 is not precisely defined.
hostname(config)# alias (inside) 209.165.200.225 192.168.100.10
Note
If you use the alias command to configure DNS Rewrite, proxy ARP will be performed for the mapped
address. To prevent this, disable Proxy ARP by entering the sysopt noproxyarp command after entering
the alias command.
Configuring DNS Rewrite with Two NAT Zones
To implement a DNS Rewrite scenario similar to the one shown in Figure 25-1, perform the following
steps:
Step 1
Create a static translation for the web server, as follows:
hostname(config)# static (real_ifc,mapped_ifc) mapped-address real-address netmask
255.255.255.255 dns
where the arguments are as follows:
Step 2
•
real_ifc—The name of the interface connected to the real addresses.
•
mapped_ifc—The name of the interface where you want the addresses to be mapped.
•
mapped-address—The translated IP address of the web server.
•
real-address—The real IP address of the web server.
Create an access list that permits traffic to the port that the web server listens to for HTTP requests.
hostname(config)# access-list acl-name extended permit tcp any host mapped-address eq port
where the arguments are as follows:
acl-name—The name you give the access list.
mapped-address—The translated IP address of the web server.
port—The TCP port that the web server listens to for HTTP requests.
Step 3
Apply the access list created in Step 2 to the mapped interface. To do so, use the access-group command,
as follows:
hostname(config)# access-group acl-name in interface mapped_ifc
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Step 4
If DNS inspection is disabled or if you want to change the maximum DNS packet length, configure DNS
inspection. DNS application inspection is enabled by default with a maximum DNS packet length of 512
bytes. For configuration instructions, see the “Configuring Application Inspection” section on
page 25-5.
Step 5
On the public DNS server, add an A-record for the web server, such as:
domain-qualified-hostname. IN A mapped-address
where domain-qualified-hostname is the hostname with a domain suffix, as in server.example.com. The
period after the hostname is important. mapped-address is the translated IP address of the web server.
The following example configures the security appliance for the scenario shown in Figure 25-1. It
assumes DNS inspection is already enabled.
hostname(config)# static (inside,outside) 209.165.200.225 192.168.100.1 netmask
255.255.255.255 dns
hostname(config)# access-list 101 permit tcp any host 209.165.200.225 eq www
hostname(config)# access-group 101 in interface outside
This configuration requires the following A-record on the DNS server:
server.example.com. IN A 209.165.200.225
DNS Rewrite with Three NAT Zones
Figure 25-2 provides a more complex scenario to illustrate how DNS inspection allows NAT to operate
transparently with a DNS server with minimal configuration. For configuration instructions for scenarios
like this one, see the “Configuring DNS Rewrite with Three NAT Zones” section on page 25-19.
Figure 25-2
DNS Rewrite with Three NAT Zones
DNS server
erver.example.com IN A 209.165.200.5
Outside
Security
Web server
appliance
192.168.100.10
DMZ
192.168.100.1
Inside
Web client
10.10.10.25
10.10.10.1
132407
99.99.99.2
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In Figure 25-2, a web server, server.example.com, has the real address 192.168.100.10 on the DMZ
interface of the security appliance. A web client with the IP address 10.10.10.25 is on the inside interface
and a public DNS server is on the outside interface. The site NAT policies are as follows:
•
The outside DNS server holds the authoritative address record for server.example.com.
•
Hosts on the outside network can contact the web server with the domain name server.example.com
through the outside DNS server or with the IP address 209.165.200.5.
•
Clients on the inside network can access the web server with the domain name server.example.com
through the outside DNS server or with the IP address 192.168.100.10.
When a host or client on any interface accesses the DMZ web server, it queries the public DNS server
for the A-record of server.example.com. The DNS server returns the A-record showing that
server.example.com binds to address 209.165.200.5.
When a web client on the outside network attempts to access http://server.example.com, the sequence of
events is as follows:
1.
The host running the web client sends the DNS server a request for the IP address of
server.example.com.
2.
The DNS server responds with the IP address 209.165.200.225 in the reply.
3.
The web client sends its HTTP request to 209.165.200.225.
4.
The packet from the outside host reaches the security appliance at the outside interface.
5.
The static rule translates the address 209.165.200.225 to 192.168.100.10 and the security appliance
directs the packet to the web server on the DMZ.
When a web client on the inside network attempts to access http://server.example.com, the sequence of
events is as follows:
1.
The host running the web client sends the DNS server a request for the IP address of
server.example.com.
2.
The DNS server responds with the IP address 209.165.200.225 in the reply.
3.
The security appliance receives the DNS reply and submits it to the DNS application inspection
engine.
4.
The DNS application inspection engine does the following:
a. Searches for any NAT rule to undo the translation of the embedded A-record address
“[outside]:209.165.200.5”. In this example, it finds the following static configuration:
static (dmz,outside) 209.165.200.225 192.168.100.10 dns
b. Uses the static rule to rewrite the A-record as follows because the dns option is included:
[outside]:209.165.200.225 --> [dmz]:192.168.100.10
Note
If the dns option were not included with the static command, DNS Rewrite would not
be performed and other processing for the packet continues.
c. Searches for any NAT to translate the web server address, [dmz]:192.168.100.10, when
communicating with the inside web client.
No NAT rule is applicable, so application inspection completes.
If a NAT rule (nat or static) were applicable, the dns option must also be specified. If the dns
option were not specified, the A-record rewrite in step b would be reverted and other processing
for the packet continues.
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5.
The security appliance sends the HTTP request to server.example.com on the DMZ interface.
Configuring DNS Rewrite with Three NAT Zones
To enable the NAT policies for the scenario in Figure 25-2, perform the following steps:
Step 1
Create a static translation for the web server on the DMZ network, as follows:
hostname(config)# static (dmz,outside) mapped-address real-address dns
where the arguments are as follows:
Step 2
•
dmz—The name of the DMZ interface of the security appliance.
•
outside—The name of the outside interface of the security appliance.
•
mapped-address—The translated IP address of the web server.
•
real-address—The real IP address of the web server.
Create an access list that permits traffic to the port that the web server listens to for HTTP requests.
hostname(config)# access-list acl-name extended permit tcp any host mapped-address eq port
where the arguments are as follows:
acl-name—The name you give the access list.
mapped-address—The translated IP address of the web server.
port—The TCP port that the web server listens to for HTTP requests.
Step 3
Apply the access list created in Step 2 to the outside interface. To do so, use the access-group command,
as follows:
hostname(config)# access-group acl-name in interface outside
Step 4
If DNS inspection is disabled or if you want to change the maximum DNS packet length, configure DNS
inspection. DNS application inspection is enabled by default with a maximum DNS packet length of 512
bytes. For configuration instructions, see the “Configuring Application Inspection” section on
page 25-5.
Step 5
On the public DNS server, add an A-record for the web server, such as:
domain-qualified-hostname. IN A mapped-address
where domain-qualified-hostname is the hostname with a domain suffix, as in server.example.com. The
period after the hostname is important. mapped-address is the translated IP address of the web server.
The following example configures the security appliance for the scenario shown in Figure 25-2. It
assumes DNS inspection is already enabled.
hostname(config)# static (dmz,outside) 209.165.200.225 192.168.100.10 dns
hostname(config)# access-list 101 permit tcp any host 209.165.200.225 eq www
hostname(config)# access-group 101 in interface outside
This configuration requires the following A-record on the DNS server:
server.example.com. IN A 209.165.200.225
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Verifying and Monitoring DNS Inspection
To view information about the current DNS connections, enter the following command:
hostname# show conn
For connections using a DNS server, the source port of the connection may be replaced by the IP address
of DNS server in the show conn command output.
A single connection is created for multiple DNS sessions, as long as they are between the same two
hosts, and the sessions have the same 5-tuple (source/destination IP address, source/destination port, and
protocol). DNS identification is tracked by app_id, and the idle timer for each app_id runs independently.
Because the app_id expires independently, a legitimate DNS response can only pass through the security
appliance within a limited period of time and there is no resource build-up. However, when you enter the
show conn command, you see the idle timer of a DNS connection being reset by a new DNS session.
This is due to the nature of the shared DNS connection and is by design.
To display the statistics for DNS application inspection, enter the show service-policy command. The
following is sample output from the show service-policy command:
hostname# show service-policy
Interface outside:
Service-policy: sample_policy
Class-map: dns_port
Inspect: dns maximum-length 1500, packet 0, drop 0, reset-drop 0
Configuring a DNS Inspection Policy Map for Additional Inspection Control
DNS application inspection supports DNS message controls that provide protection against DNS
spoofing and cache poisoning. User configurable rules allow filtering based on DNS header, domain
name, resource record type and class. Zone transfer can be restricted between servers with this function,
for example.
The Recursion Desired and Recursion Available flags in the DNS header can be masked to protect a
public server from attack if that server only supports a particular internal zone. In addition, DNS
randomization can be enabled avoid spoofing and cache poisoning of servers that either do not support
randomization, or utilize a weak pseudo random number generator. Limiting the domain names that can
be queried also restricts the domain names which can be queried, which protects the public server
further.
A configurable DNS mismatch alert can be used as notification if an excessive number of mismatching
DNS responses are received, which could indicate a cache poisoning attack. In addition, a configurable
check to enforce a Transaction Signature be attached to all DNS messages is also supported.
To specify actions when a message violates a parameter, create a DNS inspection policy map. You can
then apply the inspection policy map when you enable DNS inspection according to the “Configuring
Application Inspection” section on page 25-5.
To create a DNS inspection policy map, perform the following steps:
Step 1
(Optional) Add one or more regular expressions for use in traffic matching commands according to the
“Creating a Regular Expression” section on page 21-12. See the types of text you can match in the match
commands described in Step 3.
Step 2
(Optional) Create one or more regular expression class maps to group regular expressions according to
the “Creating a Regular Expression Class Map” section on page 21-14.
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Step 3
(Optional) Create a DNS inspection class map by performing the following steps.
A class map groups multiple traffic matches. Traffic must match all of the match commands to match
the class map. You can alternatively identify match commands directly in the policy map. The difference
between creating a class map and defining the traffic match directly in the inspection policy map is that
the class map lets you create more complex match criteria, and you can reuse class maps.
To specify traffic that should not match the class map, use the match not command. For example, if the
match not command specifies the string “example.com,” then any traffic that includes “example.com”
does not match the class map.
For the traffic that you identify in this class map, you can specify actions such as drop, drop-connection,
reset, mask, set the rate limit, and/or log the connection in the inspection policy map.
If you want to perform different actions for each match command, you should identify the traffic directly
in the policy map.
a.
Create the class map by entering the following command:
hostname(config)# class-map type inspect dns [match-all] class_map_name
hostname(config-cmap)#
Where class_map_name is the name of the class map. The match-all keyword specifies that traffic
must match all criteria to match the class map. match-all is the default and only option. The CLI