Cisco 6500 - Catalyst Series 10 Gigabit EN Interface Module Expansion, 7600 series User manual

Cisco 6500 - Catalyst Series 10 Gigabit EN Interface Module Expansion, 7600 series User manual
Catalyst 6500 Series Switch and
Cisco 7600 Series Router Firewall Services
Module Configuration Guide
Release 2.3
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Text Part Number: OL-6392-01
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C O N T E N T S
About This Guide
xvii
Document Objectives
Audience
xvii
xvii
Related Documentation
xviii
Document Organization
xviii
Document Conventions
xix
Obtaining Documentation xix
Cisco.com xix
Ordering Documentation xx
Documentation Feedback
xx
Obtaining Technical Assistance xx
Cisco Technical Support Website xx
Submitting a Service Request xxi
Definitions of Service Request Severity
xxi
Obtaining Additional Publications and Information
Quick Start Steps
xxiii
Routed Firewall Configuration Steps
xxiii
Transparent Firewall Configuration Steps
CHAPTER
1
xxii
xxv
Introduction to the Firewall Services Module
Chassis System Requirements
1-1
1-2
Features 1-3
General Features 1-3
Stateful Inspection Feature 1-5
Other Protection Features 1-6
How the Firewall Services Module Works 1-8
Security Policy Overview 1-8
VLAN Interfaces 1-8
How the Firewall Services Module Works with the Switch
Using the MSFC 1-10
Routed Firewall and Transparent Firewall Modes 1-11
Security Contexts 1-12
1-9
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Contents
CHAPTER
2
Configuring the Switch for the Firewall Services Module
Switch Overview
2-1
2-1
Verifying the Module Installation
2-2
Assigning VLANs to the Firewall Services Module 2-2
Prerequisites 2-3
Assigning VLANs in Cisco IOS Software 2-3
Assigning VLANs in Catalyst Operating System Software
2-5
Adding Switched Virtual Interfaces to the MSFC 2-5
SVI Overview 2-6
Configuring SVIs for Cisco IOS Software on the Supervisor Engine 2-8
Configuring SVIs for Catalyst Operating System Software on the Supervisor Engine
Customizing the FWSM Internal Interface
2-9
2-11
Configuring the Switch for Failover 2-11
Assigning VLANs to the Secondary Firewall Services Module 2-12
Adding a Trunk Between a Primary Switch and Secondary Switch 2-12
Ensuring Compatibility with Transparent Firewall Mode 2-12
Managing the Firewall Services Module Boot Partitions 2-12
Flash Memory Overview 2-13
Setting the Default Boot Partition 2-13
Resetting the FWSM or Booting from a Specific Partition 2-13
Resetting the FWSM in Cisco IOS Software 2-14
Resetting the FWSM in Catalyst Operating System Software
CHAPTER
3
Connecting to the Firewall Services Module and Managing the Configuration
Sessioning and Logging into the Firewall Services Module
Managing the Configuration at the CLI 3-3
Saving Configuration Changes 3-3
Viewing the Configuration 3-3
Clearing and Removing Configuration Settings
Creating Text Configuration Files Offline 3-4
CHAPTER
4
2-14
Configuring the Firewall Mode
3-1
3-1
3-4
4-1
Firewall Mode Overview 4-1
Routed Mode Overview 4-1
IP Routing Support 4-2
Network Address Translation 4-2
How Data Moves Through the FWSM in Routed Firewall Mode
Transparent Mode Overview 4-8
4-3
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Transparent Firewall Features 4-9
Using the Transparent Firewall in Your Network 4-10
Transparent Firewall Guidelines 4-11
How Data Moves Through the Transparent Firewall 4-12
Setting the Firewall Mode
CHAPTER
5
Managing Security Contexts
4-16
5-1
Security Context Overview 5-1
Common Uses for Security Contexts 5-2
Context Configuration Files 5-2
How the FWSM Classifies Packets 5-2
IP Routing Support 5-5
Sharing Resources and Interfaces Between Contexts 5-5
Sharing Resources 5-6
Shared Interface Limitations 5-7
Logging into the FWSM in Multiple Context Mode 5-9
Enabling or Disabling Multiple Context Mode 5-10
Backing Up the Single Mode Configuration 5-10
Entering an Activation Key for Multiple Security Contexts
Enabling Multiple Context Mode 5-11
Restoring Single Context Mode 5-11
5-10
Configuring Resource Management 5-11
Classes and Class Members Overview 5-12
Resource Limits 5-12
Default Class 5-13
Class Members 5-14
Configuring a Class 5-14
ACL Memory Partitions Overview 5-17
Configuring ACL Memory Partitions 5-17
Configuring a Security Context
5-19
Removing a Security Context
5-22
Changing the Admin Context
5-22
Changing Between Contexts and the System Execution Space
Changing the Security Context URL
5-23
Reloading a Security Context 5-24
Reloading by Clearing the Configuration 5-24
Reloading by Removing and Re-adding the Context
Monitoring Security Contexts
5-22
5-24
5-24
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Viewing Context Information 5-25
Viewing Resource Allocation 5-26
Viewing Resource Usage 5-28
Monitoring SYN Attacks using TCP Intercept
CHAPTER
6
Configuring Basic Settings
5-29
6-1
Changing the Passwords 6-1
Changing the Login Password 6-2
Changing the Enable Password 6-2
Changing the Maintenance Partition Passwords
Setting the Host Name
6-4
Setting the Domain Name
Adding a Login Banner
6-2
6-5
6-5
Configuring Interfaces 6-6
Security Level Overview 6-6
Setting the Name and Security Level 6-7
Allowing Communication Between Interfaces on the Same Security Level
Turning Off and Turning On Interfaces 6-10
Configuring Connection Limits for Non-NAT Configurations
CHAPTER
7
Configuring Bridging Parameters and ARP Inspection
6-8
6-10
7-1
Customizing the MAC Address Table 7-1
MAC Address Table Overview 7-1
Adding a Static MAC Address 7-2
Setting the MAC Address Timeout 7-2
Disabling MAC Address Learning 7-2
Viewing the MAC Address Table 7-3
Configuring ARP Inspection 7-3
ARP Inspection Overview 7-3
Adding a Static ARP Entry 7-4
Enabling ARP Inspection 7-4
CHAPTER
8
Configuring IP Addresses, Routing, and DHCP
8-1
Configuring IP Addresses 8-1
Assigning IP Addresses to Interfaces for a Routed Firewall 8-2
Setting the Management IP Address for a Transparent Firewall 8-2
Configuring the Default Route
Configuring Static Routes
8-2
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Configuring OSPF 8-4
OSPF Overview 8-4
Enabling OSPF 8-5
Redistributing Routes Between OSPF Processes 8-6
Adding a Route Map 8-6
Redistributing Static, Connected, or OSPF Routes to an OSPF Process 8-8
Configuring OSPF Interface Parameters 8-9
Configuring OSPF Area Parameters 8-11
Configuring OSPF NSSA 8-12
Configuring Route Summarization Between OSPF Areas 8-13
Configuring Route Summarization When Redistributing Routes into OSPF 8-14
Generating a Default Route 8-14
Configuring Route Calculation Timers 8-15
Logging Neighbors Going Up or Down 8-15
Displaying OSPF Update Packet Pacing 8-16
Monitoring OSPF 8-16
Restarting the OSPF Process 8-17
Configuring RIP 8-18
RIP Overview 8-18
Enabling RIP 8-18
Configuring the DHCP Server 8-19
Enabling the DHCP Server 8-19
Using Cisco IP Phones with a DHCP Server
Configuring DHCP Relay
CHAPTER
9
8-20
8-21
Configuring Network Address Translation
9-1
NAT Overview 9-1
Introduction to NAT 9-2
NAT Types 9-3
Dynamic NAT 9-3
PAT 9-4
Static NAT 9-5
Static PAT 9-5
Bypassing NAT 9-7
Policy NAT 9-8
Outside NAT 9-10
NAT and Same Security Level Interfaces 9-11
Order of NAT Commands Used to Match Local Addresses
Maximum Number of NAT Statements 9-12
9-12
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Global Address Guidelines 9-12
DNS and NAT 9-13
Setting Connection Limits in the NAT Configuration
Using Dynamic NAT and PAT 9-16
Dynamic NAT and PAT Implementation
Configuring NAT or PAT 9-23
Using Static NAT
9-26
Using Static PAT
9-27
9-16
9-17
Bypassing NAT 9-29
Configuring Identity NAT 9-29
Configuring Static Identity NAT 9-30
Configuring NAT Exemption 9-31
NAT Examples 9-32
Overlapping Networks 9-33
Redirecting Ports 9-34
CHAPTER
10
Controlling Network Access with Access Control Lists
10-1
Access Control List Overview 10-1
Access Control List Types and Uses 10-2
Access Control List Type Overview 10-2
Controlling Network Access for IP Traffic (Extended) 10-2
Identifying Traffic for AAA rules (Extended) 10-3
Controlling Network Access for IP Traffic for a Given User (Extended) 10-4
Identifying Addresses for Policy NAT and NAT Exemption (Extended) 10-4
VPN Management Access (Extended) 10-5
Controlling Network Access for Non-IP Traffic (EtherType) 10-5
Redistributing OSPF Routes (Standard) 10-6
Access Control List Guidelines 10-6
Access Control Entry Order 10-6
Access Control List Implicit Deny 10-6
Access Control List Commit 10-6
Maximum Number of ACEs 10-7
IP Addresses Used for Access Control Lists When You Use NAT 10-7
Inbound and Outbound Access Control Lists 10-10
Access Control List Override 10-13
Adding an Extended Access Control List
Adding an EtherType Access Control List
Adding a Standard Access Control List
10-13
10-16
10-17
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Simplifying Access Control Lists with Object Grouping 10-18
How Object Grouping Works 10-18
Adding Object Groups 10-19
Adding a Protocol Object Group 10-19
Adding a Network Object Group 10-20
Adding a Service Object Group 10-20
Adding an ICMP Type Object Group 10-21
Nesting Object Groups 10-22
Using Object Groups with an Access Control List 10-23
Displaying Object Groups 10-24
Removing Object Groups 10-24
Manually Committing Access Control Lists and Rules
Adding Remarks to Access Control Lists
10-24
10-25
Logging Extended Access Control List Activity 10-26
Access Control List Logging Overview 10-26
Configuring Logging for an Access Control Entry 10-27
Managing Deny Flows 10-28
CHAPTER
11
Allowing Remote Management
Allowing Telnet
11-1
11-1
Allowing SSH 11-2
Configuring SSH Access 11-3
Using an SSH Client 11-4
Allowing HTTPS for PDM
11-4
Allowing a VPN Management Connection 11-5
Configuring Basic Settings for All Tunnels 11-5
Configuring VPN Client Access 11-7
Configuring a Site-to-Site Tunnel 11-9
Allowing ICMP to and from the FWSM
CHAPTER
12
Configuring AAA
11-10
12-1
AAA Overview 12-1
AAA Performance 12-2
About Authentication 12-2
About Authorization 12-2
About Accounting 12-3
AAA Server and Local Database Support
Configuring the Local Database
12-4
12-6
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Identifying a AAA Server
12-6
Configuring Authentication for CLI Access
12-8
Configuring Authentication to Access Privileged Mode 12-8
Configuring Authentication for the enable Command 12-9
Authenticating Users Using the login Command 12-9
Configuring Command Authorization 12-10
Command Authorization Overview 12-10
Configuring Local Command Authorization 12-10
Local Command Authorization Prerequisites 12-11
Default Command Privilege Levels 12-11
Assigning Privilege Levels to Commands and Enabling Authorization
Viewing Command Privilege Levels 12-13
Configuring TACACS+ Command Authorization 12-13
TACACS+ Command Authorization Prerequisites 12-14
Configuring Commands on the TACACS+ Server 12-14
Enabling TACACS+ Command Authorization 12-17
Viewing the Current Logged-In User
Recovering from a Lockout
12-11
12-18
12-19
Configuring Authentication for Network Access 12-20
Authentication Overview 12-20
Enabling Network Access Authentication 12-21
Enabling Secure Authentication of Web Clients 12-22
Configuring Authorization for Network Access 12-23
Configuring TACACS+ Authorization 12-24
Configuring RADIUS Authorization 12-25
Configuring the RADIUS Server to Download Per-User Access Control Lists 12-25
Configuring the RADIUS Server to Download Per-User Access Control List Names 12-27
Configuring Accounting for Network Access
CHAPTER
13
Configuring Application Protocol Inspection
12-27
13-1
Inspection Engine Overview 13-1
When to Use Application Protocol Inspection
Inspection Limitations 13-2
Inspection Support 13-2
Configuring an Inspection Engine
13-1
13-4
Detailed Information About Inspection Engines
CUSeeMe Inspection Engine 13-5
DNS over UDP Inspection Engine 13-6
13-5
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FTP Inspection Engine 13-6
H.323 Inspection Engine 13-7
Configuring the H.323 Inspection Engine 13-7
Multiple Calls on One Call Signalling Connection 13-8
Viewing Connection Status 13-8
Technical Background 13-8
HTTP Inspection Engine 13-10
ICMP Inspection Engine 13-10
ICMP Error Inspection Engine 13-11
ILS Inspection Engine 13-11
MGCP Inspection Engine 13-12
MGCP Overview 13-13
Configuration for Multiple Call Agents and Gateways 13-13
Viewing MGCP Information 13-14
NetBios Name Service Inspection Engine 13-14
OraServ Inspection Engine 13-14
RealAudio Inspection Engine 13-14
RSH Inspection Engine 13-15
RTSP Inspection Engine 13-15
SIP Inspection Engine 13-16
Configuring the SIP Inspection Engine 13-16
SIP Overview 13-17
Technical Background 13-17
Skinny Inspection Engine 13-18
Skinny Overview 13-18
Problems with Fragmented Skinny Packets 13-19
SMTP Inspection Engine 13-19
SQL*Net Inspection Engine 13-20
Sun RPC Inspection Engine 13-21
TFTP Inspection Engine 13-21
XDMCP Inspection Engine 13-22
CHAPTER
14
Filtering HTTP, HTTPS, or FTP Requests Using an External Server
Filtering Overview
14-1
14-1
Configuring General Filtering Parameters 14-2
Identifying the Filtering Server 14-2
Buffering Replies 14-3
Setting the Maximum Length of Long HTTP URLs
Caching URL Servers 14-4
14-4
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Filtering HTTP URLs
14-5
Filtering HTTPS URLs
Filtering FTP Requests
14-6
14-6
Viewing Filtering Statistics 14-6
Viewing Filtering Server Statistics 14-7
Viewing Caching Statistics 14-7
Viewing Filtering Performance Statistics 14-8
CHAPTER
15
Using Failover
15-1
Understanding Failover 15-1
Failover Overview 15-2
Regular and Stateful Failover 15-2
Failover and State Links 15-3
Failover Link 15-3
State Link 15-3
Module Placement 15-4
Intra-Chassis Failover 15-4
Inter-Chassis Failover 15-4
Transparent Firewall Requirements 15-9
Primary/Secondary Status and Active/Standby Status
Configuration Replication 15-10
Disabling Configuration Synchronization 15-12
Failover Triggers 15-12
Failover Actions 15-12
Failover Monitoring 15-13
Module Health Monitoring 15-13
Interface Monitoring 15-14
15-10
Configuring Failover 15-15
Configuring the Primary Module 15-15
Configuring the Secondary Module 15-18
Verifying the Failover Configuration 15-19
Using the Show Failover Command 15-19
Viewing Monitored Interfaces 15-22
Testing the Failover Functionality 15-22
Forcing Failover
Disabling Failover
15-23
15-23
Monitoring Failover 15-23
Failover System Messages
SNMP 15-24
15-24
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Debug Messages
15-24
Frequently Asked Failover Questions 15-24
Configuration Replication Questions 15-24
Basic Failover Questions 15-25
Stateful Failover Questions 15-26
Failover Configuration Example
CHAPTER
16
15-27
Managing Software and Configuration Files
16-1
Installing Application or PDM Software 16-1
Installation Overview 16-1
Installing Application or PDM Software to the Current Partition 16-2
Installing Application Software to Any Application Partition 16-3
Installing Maintenance Software
16-5
Downloading and Backing Up Configuration Files 16-5
Downloading a Text Configuration 16-6
Backing Up the Configuration 16-7
Copying the Configuration to a Server 16-7
Copying the Configuration from the Terminal Display
CHAPTER
17
16-8
Monitoring and Troubleshooting the Firewall Services Module
Monitoring the Firewall Services Module
Using System Messages 17-1
Using SNMP 17-1
SNMP Overview 17-2
Enabling SNMP 17-3
17-1
17-1
Troubleshooting the Firewall Services Module 17-4
Testing Your Configuration 17-4
Enabling ICMP Debug Messages and System Messages 17-4
Pinging FWSM Interfaces 17-5
Pinging Through the FWSM 17-7
Disabling the Test Configuration 17-8
Reloading the Firewall Services Module 17-8
Reloading the FWSM from the FWSM CLI 17-8
Reloading the FWSM from the Switch 17-9
Troubleshooting Passwords and AAA 17-9
Clearing the Application Partition Passwords and AAA Settings
Recovering the Maintenance Partition Passwords 17-10
Other Troubleshooting Tools 17-10
Viewing Debug Messages 17-10
17-9
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Capturing Packets 17-10
Viewing the Crash Dump 17-11
Common Problems 17-11
APPENDIX
A
Specifications
A-1
Physical Attributes
Feature Limits
A-1
A-2
Managed System Resources
Fixed System Resources
Rule Limits
APPENDIX
B
A-3
A-4
A-5
Sample Configurations
B-1
Routed Mode Examples B-1
Example 1: Security Contexts With Outside Access B-1
Example 1: System Configuration B-2
Example 1: Admin Context Configuration B-3
Example 1: Customer A Context Configuration B-4
Example 1: Customer B Context Configuration B-4
Example 1: Customer C Context Configuration B-4
Example 1: Switch Configuration B-5
Example 2: Single Mode Using Same Security Level B-5
Example 2: FWSM Configuration B-6
Example 2: Switch Configuration B-7
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
Example 3: Switch Configuration B-11
Example 4: Failover B-11
Example 4: Primary FWSM Configuration B-12
Example 4: Secondary FWSM System Configuration B-14
Example 4: Switch Configuration B-14
Transparent Mode Examples B-15
Example 5: Security Contexts With Outside Access B-15
Example 5: System Configuration B-16
Example 5: Admin Context Configuration B-17
Example 5: Customer A Context Configuration B-17
Example 5: Customer B Context Configuration B-17
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Example 5: Customer C Context Configuration B-18
Example 5: Switch Configuration B-18
Example 6: Failover B-18
Example 6: Primary FWSM Configuration B-19
Example 6: Secondary FWSM System Configuration B-21
Example 6: Switch Configuration B-21
APPENDIX
C
Understanding the Command-Line Interface
Command Prompts
C-1
Syntax Formatting
C-2
Abbreviating Commands
Command Line Editing
C-2
C-3
Filtering Show Command Output
Command Output Paging
Adding Comments
C-1
C-3
C-4
C-4
Text Configuration Files C-4
How Commands Correspond with Lines in the Text File C-5
Subcommands C-5
Automatic Text Entries C-5
Line Order C-5
Commands Not Included in the Text Configuration C-5
Passwords C-6
Multiple Security Context Files C-6
Command Help
APPENDIX
D
C-6
Addresses, Protocols, and Ports Reference
D-1
IP 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
Protocols and Applications
TCP and UDP Ports
ICMP Types
D-3
D-5
D-6
D-9
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APPENDIX
E
Acronyms and Abbreviations
E-1
INDEX
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About This Guide
This guide contains the following sections:
•
Document Objectives, page xvii
•
Audience, page xvii
•
Related Documentation, page xviii
•
Document Organization, page xviii
•
Document Conventions, page xix
•
Obtaining Documentation, page xix
•
Documentation Feedback, page xx
•
Obtaining Technical Assistance, page xx
•
Obtaining Additional Publications and Information, page xxii
Document Objectives
The purpose of this guide is to help you configure the Firewall Services Module (FWSM) for the most
common scenarios using the command line interface. It does not cover every feature, but it does describe
those tasks most commonly required for configuration.
Audience
This guide is for network managers who perform any of the following tasks:
•
Managing network security
•
Installing and configuring firewalls
•
Managing default and static routes, and TCP and UDP services
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About This Guide
Related Documentation
Related Documentation
For more information, refer to the following documentation set for the FWSM:
•
Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Command
Reference
•
Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module System
Messages Guide
•
Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Installation
Note
•
Release Notes for the Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services
Module
Document Organization
This guide includes the following chapters and appendixes:
•
“Quick Start Steps” provides pointers to the minimum configuration required for routed or
transparent mode.
•
Chapter 1, “Introduction to the Firewall Services Module,” describes the system requirements and
features.
•
Chapter 2, “Configuring the Switch for the Firewall Services Module,” tells how to configure the
switch for use with the FWSM.
•
Chapter 3, “Connecting to the Firewall Services Module and Managing the Configuration,” tells
how to access the FWSM command line interface (CLI) and manage the configuration.
•
Chapter 4, “Configuring the Firewall Mode,” tells how to set the firewall mode.
•
Chapter 5, “Managing Security Contexts,” tells how to configure multiple security contexts.
•
Chapter 6, “Configuring Basic Settings,” tells how to configure basic settings that are either
essential or useful to the operation of your FWSM.
•
Chapter 7, “Configuring Bridging Parameters and ARP Inspection,” tells how to customize the
operation of the transparent firewall.
•
Chapter 8, “Configuring IP Addresses, Routing, and DHCP,” tells how to configure IP addresses,
static routes, dynamic routing, and DHCP.
•
Chapter 9, “Configuring Network Address Translation,” tells how to configure Network Address
Translation (NAT).
•
Chapter 10, “Controlling Network Access with Access Control Lists,” tells how to control network
access through the FWSM using access control lists (ACLs).
•
Chapter 11, “Allowing Remote Management,” tells how to allow remote management access to the
FWSM.
•
Chapter 12, “Configuring AAA,” tells how to configure AAA, which includes command
authorization, CLI access authentication, and AAA for traffic through the FWSM.
•
Chapter 13, “Configuring Application Protocol Inspection,” tells how to configure inspection
engines.
•
Chapter 14, “Filtering HTTP, HTTPS, or FTP Requests Using an External Server,” tells how to
configure filtering.
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Document Conventions
•
Chapter 15, “Using Failover,” tells how to configure a primary and secondary FWSM for
redundancy.
•
Chapter 16, “Managing Software and Configuration Files,” tells how to upgrade or reinstall FWSM
software.
•
Chapter 17, “Monitoring and Troubleshooting the Firewall Services Module,” tells how to monitor
and troubleshoot the FWSM. See the Catalyst 6500 Series Switch and Cisco 7600 Series Router
Firewall Services Module System Messages Guide for detailed information about system logging.
•
Appendix A, “Specifications,” lists the specifications for the FWSM.
•
Appendix B, “Sample Configurations,” shows some common scenarios and the configurations that
support them.
•
Appendix C, “Understanding the Command-Line Interface,” describes the CLI.
•
Appendix D, “Addresses, Protocols, and Ports Reference,” provides reference information,
including lists of TCP, UDP, and ICMP port types, and common subnet masks.
•
Appendix E, “Acronyms and Abbreviations,” lists acronyms and abbreviations used in this guide.
•
“Index” provides easy access to topics within the guide.
Document Conventions
This guide uses the following conventions:
Note
Means reader take note. Notes contain helpful suggestions or references to material not
covered in the manual.
Syntax formatting is described in the “Syntax Formatting” section on page C-2.
Obtaining Documentation
Cisco documentation and additional literature are available on Cisco.com. Cisco also provides several
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technical information from Cisco Systems.
Cisco.com
You can access the most current Cisco documentation at this URL:
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You can access the Cisco website at this URL:
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You can access international Cisco websites at this URL:
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About This Guide
Documentation Feedback
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About This Guide
Obtaining Technical Assistance
Note
Use the Cisco Product Identification (CPI) tool to locate your product serial number before submitting
a web or phone request for service. You can access the CPI tool from the Cisco Technical Support
Website by clicking the Tools & Resources link under Documentation & Tools. Choose Cisco Product
Identification Tool from the Alphabetical Index drop-down list, or click the Cisco Product
Identification Tool link under Alerts & RMAs. The CPI tool offers three search options: by product ID
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Search results show an illustration of your product with the serial number label location highlighted.
Locate the serial number label on your product and record the information before placing a service call.
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and S4 service requests are those in which your network is minimally impaired or for which you require
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For a complete list of Cisco TAC contacts, go to this URL:
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Definitions of Service Request Severity
To ensure that all service requests are reported in a standard format, Cisco has established severity
definitions.
Severity 1 (S1)—Your network is “down,” or there is a critical impact to your business operations. You
and Cisco will commit all necessary resources around the clock to resolve the situation.
Severity 2 (S2)—Operation of an existing network is severely degraded, or significant aspects of your
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Severity 4 (S4)—You require information or assistance with Cisco product capabilities, installation, or
configuration. There is little or no effect on your business operations.
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About This Guide
Obtaining Additional Publications and Information
Obtaining Additional Publications and Information
Information about Cisco products, technologies, and network solutions is available from various online
and printed sources.
•
Cisco Marketplace provides a variety of Cisco books, reference guides, and logo merchandise. Visit
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•
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•
World-class networking training is available from Cisco. You can view current offerings at
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Quick Start Steps
The following sections describe the minimum configuration required for the Firewall Services Module
(FWSM) in routed mode or transparent mode:
•
Routed Firewall Configuration Steps, page xxiii
•
Transparent Firewall Configuration Steps, page xxv
Routed Firewall Configuration Steps
Follow these steps to configure the FWSM in routed mode:
Task
Description
Step 1
Assigning VLANs to the Firewall Services Module, page 2-2 On the switch, you need to assign VLANs to the
FWSM so the FWSM can send and receive traffic on
the switch.
Step 2
(Might be required) Adding Switched Virtual Interfaces to
the MSFC, page 2-5
If you want the Multilayer Switch Feature Card
(MSFC) to route between VLANs that are assigned to
the FWSM, complete this procedure.
Step 3
Sessioning and Logging into the Firewall Services Module,
page 3-1
From the switch CLI, you can session into the FWSM
to access the FWSM CLI.
Step 4
(Might be required; multiple context mode only) Enabling or If you want to use multiple context mode and your
Disabling Multiple Context Mode, page 5-10
FWSM is not already configured for it, or if you want
to change back to single mode, follow this procedure.
Step 5
(Multiple context mode only) Configuring a Security
Context, page 5-19
Add a security context.
Step 6
(Multiple context mode only) Changing Between Contexts
and the System Execution Space, page 5-22
You must configure some settings in the system
execution space, and some settings within the
context, so you need to know how to switch between
contexts and the system execution space.
Step 7
Setting the Name and Security Level, page 6-7
For each VLAN interface, you must set a name (such
as inside or outside) and a security level.
Step 8
Assigning IP Addresses to Interfaces for a Routed Firewall,
page 8-2
Assign an IP address to each interface.
Step 9
Configuring the Default Route, page 8-2
Create a default route to an upstream router.
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Routed Firewall Configuration Steps
Task
Step 10
In multiple context mode, static routing is the only
routing method supported. In single mode, you have
• Configuring Static Routes, page 8-3
a choice of static, RIP, or OSPF. RIP support is for
• (Single context mode only) Configuring OSPF, page 8-4 passive mode only.
Configure routing using one of these methods:
•
Step 11
Description
(Single context mode only) Configuring RIP, page 8-18
Use one or more of these NAT methods:
•
Using Dynamic NAT and PAT, page 9-16
•
Using Static NAT, page 9-26
•
Using Static PAT, page 9-27
•
Bypassing NAT, page 9-29
You must specifically configure some interfaces to
either use or bypass NAT. Typically, if you want to
allow inside users to access the outside or other
networks attached to the FWSM, configure dynamic
NAT or PAT according to the “Using Dynamic NAT
and PAT” section on page 16. If you want to allow
outside users to access an inside host, then configure
static NAT according to the “Using Static NAT”
section on page 26.
The FWSM offers a large amount of flexibility in
your NAT configuration.
Step 12
Adding an Extended Access Control List, page 10-13
Before any traffic can go through the FWSM, you
must create an ACL that permits traffic, and then
apply it to an interface.
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Transparent Firewall Configuration Steps
Transparent Firewall Configuration Steps
Follow these steps to configure the FWSM in transparent mode:
Task
Description
Step 1
Assigning VLANs to the Firewall Services Module, page 2-2 On the switch, you need to assign VLANs to the
FWSM so the FWSM can send and receive traffic on
the switch.
Step 2
(Might be required) Adding Switched Virtual Interfaces to
the MSFC, page 2-5
If you want the MSFC to route between VLANs that
are assigned to the FWSM, complete this procedure.
Step 3
Sessioning and Logging into the Firewall Services Module,
page 3-1
From the switch CLI, you can session into the FWSM
to access the FWSM CLI.
Step 4
Setting the Firewall Mode, page 4-16
Before you configure any settings, you must set the
firewall mode to transparent mode. Changing the
mode clears your configuration.
Step 5
(Might be required; multiple context mode only) Enabling or If you want to use multiple context mode and your
Disabling Multiple Context Mode, page 5-10
FWSM is not already configured for it, or if you want
to change back to single mode, follow this procedure.
Step 6
(Multiple context mode only) Configuring a Security
Context, page 5-19
Add a security context.
Step 7
(Multiple context mode only) Changing Between Contexts
and the System Execution Space, page 5-22
You must configure some settings in the system
execution space, and some settings within the
context, so you need to know how to switch between
contexts and the system execution space.
Step 8
Setting the Name and Security Level, page 6-7
For each VLAN interface, you must set a name (such
as inside or outside) and a security level.
Step 9
Setting the Management IP Address for a Transparent
Firewall, page 8-2
The transparent firewall requires a management IP
address.
Step 10
Adding an Extended Access Control List, page 10-13
Before any traffic can go through the FWSM, you
must create an ACL that permits traffic, and then
apply it to an interface.
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Quick Start Steps
Transparent Firewall Configuration Steps
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1
Introduction to the Firewall Services Module
The Firewall Services Module (FWSM) is a high-performance, space-saving, stateful firewall module
that installs in the Catalyst 6500 series switches and the Cisco 7600 series routers.
Firewalls protect inside networks from unauthorized access by users on an outside network. The 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
includes only the public servers, an attack there affects only 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.
Note
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 FWSM 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.
The FWSM includes many advanced features, such as multiple security contexts (similar to virtualized
firewalls), transparent (Layer 2) firewall or routed (Layer 3) firewall operation, hundreds of interfaces,
and many more features.
This chapter contains the following sections:
•
Chassis System Requirements, page 1-2
•
How the Firewall Services Module Works, page 1-8
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Chassis System Requirements
Chassis System Requirements
The switch models that support the FWSM include the following platforms:
•
Catalyst 6500 series switches, with the following required components:
– Supervisor engine with Cisco IOS software (known as supervisor IOS) or Catalyst operating
system (OS). See Table 1-1 for supported supervisor engine and software releases.
– Multilayer Switch Feature Card (MSFC 2) with Cisco IOS software. See Table 1-1 for
supported Cisco IOS releases.
•
Cisco 7600 series routers, with the following required components:
– Supervisor engine with Cisco IOS software. See Table 1-1 for supported supervisor engine and
software releases.
– MSFC 2 with Cisco IOS software. See Table 1-1 for supported Cisco IOS releases.
Note
The FWSM does not support a direct connection to a switch WAN port because WAN ports do not use
static virtual local area networks (VLANs). However, the WAN port can connect to the MSFC, which
can connect to the FWSM.
Table 1-1 shows the supervisor engine version, software, and supported FWSM features.
Table 1-1
Support for FWSM 2.3 Features
FWSM Features:
Supervisor Engines1
Multiple SVIs2
Transparent Firewall
with Failover3
12.1(13)E
2
No
No
12.1(19)E
2
Yes
No
12.1(22)E and higher
2
Yes
Yes
12.2(14)SY and higher
2
Yes
No
12.2(14)SX
2, 720
No
No
12.2(17a)SX3
2, 720
Yes
Yes
12.2(17b)SXA
2, 720
Yes
Yes
12.2(17d)SXB and higher
2, 720
Yes
Yes
7.5(x)
2
No
No
7.6(1) through 7.6(4)
2
Yes
No
7.6(5) and higher
2
Yes
Yes
8.2(x)
2, 720
Yes
Yes
8.3(x)
2, 720
Yes
Yes
Cisco IOS
Catalyst OS
4
1. The FWSM does not support the supervisor 1 or 1A.
2. Supports multiple switched VLAN interfaces (SVIs) between the MSFC and FWSM. An SVI is a VLAN interface that is
routed on the MSFC.
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3. Supports transparent firewall mode when you use failover. Failover requires BPDU forwarding to the FWSM, or else you can
have a loop. Other releases that do not support BPDU forwarding only support transparent mode without failover.
4. When you use Catalyst OS on the supervisor, you can use any of the supported Cisco IOS releases above on the MSFC. (When
you use Cisco IOS software on the supervisor, you use the same release on the MSFC.) The supervisor software determines
the FWSM feature support. For example, if you use Catalyst OS Release 7.6(1) on the supervisor and Cisco IOS 12.1(13)E
on the MSFC, then the switch does support multiple SVIs, because Catalyst OS Release 7.6(1) supports multiple SVIs.
Features
This section describes the FWSM features, and includes the following topics:
•
Features, page 1-3
•
Stateful Inspection Feature, page 1-5
•
Other Protection Features, page 1-6
General Features
Table 1-2 lists the features of the FWSM.
Table 1-2
General FWSM Features
Feature
Description
Transparent firewall or routed The firewall can run in one of the following modes:
firewall mode
• Routed—The FWSM is considered to be a router hop in the network. It performs NAT 1
between connected networks. In single context mode, you can use OSPF2 or passive
RIP3.
•
Multiple security contexts
Transparent—The FWSM acts like a “bump in the wire,” and is not a router hop. The
FWSM connects the same network on its inside and outside interfaces, but each interface
must be on a different VLAN. No dynamic routing protocols or NAT are required.
In multiple context mode, you can create up to 100 separate security contexts (depending on
your software license). A security context is a virtual firewall that has its own security policy
and interfaces. Multiple contexts are similar to having multiple stand-alone firewalls.
Contexts are conveniently contained within a single module.
You can run all security contexts in routed mode or in transparent mode; you cannot run some
contexts in one mode and others in another.
With the default software license, you can run up to two security contexts in addition to an
admin context. For more contexts, you must purchase a license.
Resource management for
security contexts
You can limit resources per context so one context does not use up too many resources. You
create classes that define resource limitations as an absolute value or as a percentage, and then
assign a context to one of these classes.
Communication between
same security level
You can configure interfaces on the same security level to communicate with each other. This
feature is off by default, and you can enable or disable this feature on a per context basis. In
earlier releases, no communication between interfaces with the same security level was
possible.
Bidirectional NAT and policy
NAT
You can perform NAT on inside and outside addresses. For policy NAT, you can identify
addresses to be translated using an extended ACL 4, which allows you more control in
determining which addresses to translate.
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Table 1-2
General FWSM Features (continued)
Feature
Description
Several ACL types
The FWSM supports the following ACLs:
•
Extended ACL to control IP traffic on an interface:
– Inbound
– Outbound
•
For transparent firewall mode, EtherType ACL to control non-IP traffic on an interface:
– Inbound
– Outbound
•
Standard ACL for OSPF route redistribution.
URL Filtering
Filter HTTP, HTTPS, and FTP requests using Websense Enterprise or Sentian by N2H2.
Dynamic Routing Protocols
Single context mode only.
•
RIP v1 and v2 (passive mode)
•
OSPF
Note
Multiple context mode supports static routing only.
DHCP server and DHCP relay The FWSM acts as a DHCP5 server. The FWSM also supports DHCP relay to forward DHCP
requests to an upstream router.
Management
The FWSM supports the following management methods:
•
Cisco PDM for FWSM—Release 4.0 supports FWSM Release 2.3 features. PDM is a
browser-based configuration tool that resides on the FWSM. The system administrator
can configure multiple security contexts. If desired, individual context administrators can
configure only their contexts.
•
Cisco Firewall MC6—Release 1.3.1 supports FWSM Release 2.3 features. For multiple
context mode, Release 1.3.1 supports management of each context separately but does
not support system-level operations, such as adding or deleting contexts, or the
provisioning of failover in multiple mode.
•
CLI7
Login banners
You can define a text message to display when users log into the FWSM.
System message
enhancements
You can configure ACLs to generate system messages when they match traffic. You can also
set the level for a system message.
1. Network Address Translation
2. Open Shortest Path First
3. Routing Information Protocol
4. access control lists
5. Dynamic Host Configuration Protocol
6. Firewall Management Center
7. command-line interface
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Features
Stateful Inspection Feature
All traffic that goes through the firewall is inspected using the Adaptive Security Algorithm (ASA) and
is 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 FWSM, however, takes into consideration the state of a packet:
•
Is this a new connection?
If it is a new connection, the firewall has to check the packet against ACLs 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 ACL checks
– Performing route lookups
– Allocating NAT translations (xlates)
– Establishing sessions in the “fast 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.
Note
•
The FWSM performs session management path and fast path processing on three specialized
networking processors (NPs). The control plane path processing is performed in a
general-purpose processor that also handles traffic directed to the FWSM and configuration and
management tasks.
Is this an established connection?
If the connection is already established, the firewall 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
The following types of traffic go through the fast path:
– Established TCP or UDP connections
For UDP, which does not have sessions, the FWSM creates UDP connection state information
so that it can also use the fast path.
– ICMP control packets
– Data packets for protocols that require Layer 7 inspection
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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.
Other Protection Features
Table 1-3 describes the protection features provided by the FWSM. These features control network
activity associated with specific kinds of attacks.
Table 1-3
Protection Features
Protection Feature
Description
ARP Inspection
For transparent firewall mode, you can enable ARP inspection. By default, ARP inspection is disabled
on all interfaces; all ARP packets are allowed through the FWSM. When you enable ARP inspection,
the FWSM compares the MAC address and IP address in all ARP packets to static entries in the ARP
table. Enable this feature using the arp inspection command.
DNS Guard
DNS Guard identifies each outbound DNS1 resolve request, and allows only a single DNS response. A
host might query several servers for a response (in the case that the first server is slow in responding),
but only the first answer to the request is allowed. All additional responses to the request are dropped
by the firewall. This feature is always enabled. This feature is unrelated to the DNS inspection engine.
Flood Guard
Flood Guard controls the tolerance of the AAA server for unanswered login attempts. This helps to
prevent a DoS 2 attack on AAA services in particular. This feature optimizes AAA system use. Flood
Guard is enabled by default and can be controlled with the floodguard command.
Frag Guard
Frag Guard provides IP fragment protection, and can be configured with the fragment command.
Note
In FWSM 1.1, the default fragment size was 1, which caused the FWSM to drop all fragments
by default. In FWSM 2.3, the default fragment size is 200 (the same as the PIX default).
ICMP Filtering
The FWSM automatically denies ICMP access to FWSM interfaces. This feature shields FWSM
interfaces from detection by users on an external network. You can allow ICMP to FWSM interfaces
using the icmp command.
Mail Guard
Mail Guard provides safe access for SMTP3 connections from the outside to an inside messaging server.
This feature lets you deploy a single mail server within the internal network without it being exposed to
known security problems with some SMTP server implementations. This eliminates the need for an
external mail relay (or bastion host) system. Mail Guard enforces a safe minimal set of SMTP commands
to avoid an SMTP server system from being compromised. Enable this feature using the fixup protocol
smtp 25 command.
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Table 1-3
Protection Features (continued)
Protection Feature
Description
TCP Intercept
TCP Intercept protects inside systems from a DoS attack perpetrated by flooding an interface with TCP
SYN4 packets. Enable this feature by setting the maximum embryonic connections option of the nat and
static commands.
When the embryonic limit has been surpassed, the TCP intercept feature intercepts TCP SYN packets
from clients to servers on a higher security level.
The TCP intercept feature implements software to protect TCP servers from TCP SYN-flooding attacks,
which are a type of denial-of-service attack. SYN cookies are used during the validation process and
help to minimize the amount of valid traffic being dropped. For detailed information about configuring
TCP intercept, see the “Monitoring SYN Attacks using TCP Intercept” section on page 5-29.
Unicast Reverse
Path Forwarding
Unicast RPF helps mitigate problems caused by the introduction of malformed or forged (spoofed) IP
source addresses into a network by discarding IP packets that lack a verifiable IP source address. Enable
this feature using the ip verify reverse-path command.
1. Domain Name System
2. denial of service
3. Simple Mail Transfer Protocol
4. synchronization
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How the Firewall Services Module Works
How the Firewall Services Module Works
This section describes the network firewall functionality provided by the FWSM. It includes the
following topics:
•
Security Policy Overview, page 1-8
•
VLAN Interfaces, page 1-8
•
How the Firewall Services Module Works with the Switch, page 1-9
•
Routed Firewall and Transparent Firewall Modes, page 1-11
•
Security Contexts, page 1-12
Security Policy Overview
A security policy determines which traffic is allowed to pass through the firewall to access another
network. By default, no traffic can pass through the firewall. By applying ACLs to interfaces, you can
determine which IP addresses and traffic types can pass through the interfaces to access other networks.
Note
By default, the Cisco PIX firewall allows traffic to flow freely from an inside network (higher security
level) to an outside network (lower security level). However, the FWSM does not allow any traffic to
pass between interfaces unless you explicitly permit it with an ACL. This rule is true for both routed
firewall mode and transparent firewall mode. While you still specify the security level for an interface
on the FWSM, the security level does not provide explicit permission for traffic to travel from a high
security interface to a low security interface. See the “Configuring Interfaces” section on page 6-6 for
more information about how security levels work.
For routed firewall mode, in addition to ACLs, you can use Network Address Translation (NAT) between
networks to further protect the real IP addresses of hosts.
If you have an AAA server, you can also apply AAA rules to users to control their access.
All of these features plus others, such as filters or inspection engines, make up the security policy of the
firewall.
VLAN Interfaces
The FWSM does not include any external physical interfaces. Instead, it uses internal VLAN interfaces.
For example, you assign VLAN 201 to the FWSM inside interface, and VLAN 200 to the outside
interface. You assign these VLANs to physical switch ports, and hosts connect to those ports. When
communication occurs between VLANs 201 and 200, the FWSM is the only available path between the
VLANs, forcing traffic to be statefully inspected.
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Figure 1-1 shows the FWSM with 4 interfaces: one outside interface (VLAN 200), one DMZ interface
(VLAN 202), and two inside interfaces (VLAN 201 and 203).
Figure 1-1
VLAN Interfaces
Internet
Switch
VLAN 200
FWSM
VLAN 201
VLAN 203
Inside
HR
DMZ
104697
VLAN 202
How the Firewall Services Module Works with the Switch
You can install the FWSM in the Catalyst 6500 series switches and the Cisco 7600 series routers. The
configuration of both series is identical, except for the following variations:
•
The Catalyst 6500 series switches supports two software modes:
– Cisco IOS software on both the switch supervisor and the integrated MSFC (known as
“supervisor IOS”).
– Catalyst Operating System (OS) on the supervisor, and Cisco IOS software on the MSFC.
For commands and configuration that are performed on the switch itself, both modes are described.
•
The Cisco 7600 series routers support only Cisco IOS software.
Both series are referred to generically in this guide as the “switch.”
The FWSM runs its own operating system, based on the PIX operating system. Although the PIX OS is
similar to the FWSM OS, there are a number of differences. Many of the differences are enhancements
that take advantage of the FWSM hardware and architecture.
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Using the MSFC
The switch includes a switching processor (the supervisor) and a router (the MSFC). Although you need
the MSFC as part of your system, you do not have to use it. If you choose to do so, you can assign one
or more VLAN interfaces to the MSFC (if your switch software version supports multiple SVIs; see
Table 1-1 on page 1-2). In single context mode, you can place the MSFC in front of the firewall or
behind the firewall (see Figure 1-2).
The location of the MSFC depends entirely on the VLANs that you assign to it. For example, the MSFC
is behind the firewall in the example shown on the left side of Figure 1-2 because you assigned
VLAN 201 to the inside interface of the FWSM. The MSFC is in front of the firewall in the example
shown on the right side of Figure 1-2 because you assigned VLAN 200 to the outside interface of the
FWSM.
In the left-hand example, the MSFC routes between VLANs 201, 301, 302, and 303, and no inside traffic
goes through the FWSM unless it is destined for the Internet. In the right-hand example, the FWSM
processes and protects all traffic between the inside VLANs 201, 202, and 203.
Figure 1-2
MSFC Placement
MSFC Behind the FWSM
MSFC In Front of the FWSM
Internet
Internet
Switch
Switch
VLAN 100
VLAN 200
MSFC
FWSM
VLAN 200
VLAN 201
FWSM
MSFC
VLAN 303
Inside
HR
VLAN 302
DMZ
VLAN 201
VLAN 203
Inside
HR
VLAN 202
DMZ
104657
VLAN 301
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For multiple context mode, if you place the MSFC behind the FWSM, you should only connect it to a
single context. If you connect the MSFC to multiple contexts, the MSFC will route between the contexts,
which might not be your intention. The typical scenario for multiple contexts is to use the MSFC in front
of all the contexts to route between the Internet and the switched networks (see Figure 1-3).
Figure 1-3
MSFC Placement with Multiple Contexts
Internet
Switch
VLAN 100
MSFC
VLAN 200
Context A
VLAN 201
Admin
Network
Context B
VLAN 202
Inside
Customer A
Context C
VLAN 203
Inside
Customer B
VLAN 204
Inside
Customer C
104659
Admin
Context
Routed Firewall and Transparent Firewall Modes
The FWSM can run in two firewall modes:
•
Routed
•
Transparent
In routed mode, the FWSM is considered to be a router hop in the network. It performs NAT between
connected networks, and can use OSPF or passive RIP (in single context mode). Routed mode supports
up to 256 interfaces per context or in single mode, with a maximum of 1000 interfaces divided between
all contexts.
In transparent mode, the FWSM acts like a “bump in the wire,” or a “stealth firewall,” and is not a router
hop. The FWSM connects the same network on its inside and outside interfaces, but each interface must
be on a different VLAN. No dynamic routing protocols or NAT are required. However, like routed mode,
transparent mode also requires ACLs to allow traffic through. Transparent mode can also optionally use
EtherType ACLs to allow non-IP traffic. Transparent mode only supports two interfaces, an inside
interface and an outside interface.
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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 ACL.
See Chapter 7, “Configuring Bridging Parameters and ARP Inspection,” for more information.
Security Contexts
You can partition a single FWSM into multiple virtual firewalls, known as security contexts. Each
context is an independent system, with its own security policy, interfaces, and administrators. Multiple
contexts are similar to having multiple stand-alone firewalls.
Each context has its own configuration that identifies the security policy, interfaces, and almost all the
options you can configure on a stand-alone firewall. If desired, you can allow individual context
administrators to implement the security policy on the context. Some resources are controlled by the
overall system administrator, such as VLANs and system resources, so that one context cannot affect
other contexts inadvertently.
The system administrator adds and manages contexts by configuring them in the system configuration,
which identifies basic settings for the module. The system administrator has privileges to manage all
contexts. 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 (for
example, over an SSH connection), then that user has system administrator rights, and can access the
system configuration and all other context configurations. Typically, the admin context provides network
access to network-wide resources, such as a syslog server or context configuration server.
With the default software license, you can run up to two security contexts plus the admin context. For
more contexts, you must purchase a license.
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.
Note
Multiple context mode supports static routing only.
See Chapter 5, “Managing Security Contexts,” for more information.
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2
Configuring the Switch for the Firewall Services
Module
This chapter describes how to configure the Catalyst 6500 series switch or the Cisco 7600 series router
for use with the Firewall Services Module (FWSM). Before completing the procedures in this chapter,
configure the basic properties of your switch, including assigning VLANs to interfaces, according to the
documentation that came with your switch.
This chapter includes the following sections:
•
Switch Overview, page 2-1
•
Verifying the Module Installation, page 2-2
•
Assigning VLANs to the Firewall Services Module, page 2-2
•
Adding Switched Virtual Interfaces to the MSFC, page 2-5
•
Customizing the FWSM Internal Interface, page 2-11
•
Configuring the Switch for Failover, page 2-11
•
Managing the Firewall Services Module Boot Partitions, page 2-12
Switch Overview
You can install the FWSM in the Catalyst 6500 series switches or the Cisco 7600 series routers. The
configuration of both series is identical, and the series are referred to generically in this guide as the
“switch.” The switch includes a switch (the supervisor engine) as well as a router (the Multilayer Switch
Feature Card (MSFC)).
The switch supports two software modes:
•
Cisco IOS software on both the switch supervisor engine and the integrated MSFC router.
•
Catalyst operating system software on the supervisor engine, and Cisco IOS software on the MSFC.
Both modes are described in this guide.
See the “Using the MSFC” section on page 1-10 for more information about the MSFC.
Note
For each FWSM in a switch using Cisco IOS software, the SPAN reflector feature is enabled. This
feature enables multicast traffic (and other traffic that requires central rewrite engine) to be switched
when coming from the FWSM. The SPAN reflector feature uses one SPAN session. To disable this
feature, enter the following command:
Router(config)# no monitor session servicemodule
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Verifying the Module Installation
Verifying the Module Installation
To verify that the switch acknowledges the FWSM and has brought it online, view the module
information according to your operating system:
•
Cisco IOS software
Router> show module [mod-num | all]
The following example shows the output of the show module command:
Router> show module
Mod Ports Card Type
--- ----- -------------------------------------1
2 Catalyst 6000 supervisor 2 (Active)
2
48 48 port 10/100 mb RJ-45 ethernet
3
2 Intrusion Detection System
4
6 Firewall Module
•
Model
-----------------WS-X6K-SUP2-2GE
WS-X6248-RJ-45
WS-X6381-IDS
WS-SVC-FWM-1
Serial No.
----------SAD0444099Y
SAD03475619
SAD04250KV5
SAD062302U4
Catalyst operating system software
Console> show module [mod-num]
The following example shows the output of the show module command:
Console>
Mod Slot
--- ---1
1
15 1
4
4
5
5
6
6
Note
show module
Ports Module-Type
----- ------------------------2
1000BaseX Supervisor
1
Multilayer Switch Feature
2
Intrusion Detection Syste
6
Firewall Module
8
1000BaseX Ethernet
Model
------------------WS-X6K-SUP1A-2GE
WS-F6K-MSFC
WS-X6381-IDS
WS-SVC-FWM-1
WS-X6408-GBIC
Sub
--yes
no
no
no
no
Status
-----ok
ok
ok
ok
ok
The show module command shows six ports for the FWSM; these are internal ports that are grouped
together as an EtherChannel. See the “Customizing the FWSM Internal Interface” section on page 2-11
for more information.
Assigning VLANs to the Firewall Services Module
This section describes how to assign VLANs to the FWSM. The FWSM does not include any external
physical interfaces. Instead, it uses VLAN interfaces. Assigning VLANs to the FWSM is similar to
assigning a VLAN to a switch port; the FWSM includes an internal interface to the Switch Fabric
Module (if present) or the shared bus.
See the following topics:
•
Prerequisites, page 2-3
•
Assigning VLANs in Cisco IOS Software, page 2-3
•
Assigning VLANs in Catalyst Operating System Software, page 2-5
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Configuring the Switch for the Firewall Services Module
Assigning VLANs to the Firewall Services Module
Prerequisites
Follow these steps to make sure you can use the VLANs on the FWSM. See the documentation for the
switch for detailed information.
1.
Add the VLANs to the switch.
If you do not add the VLANs to the switch before you assign them to the FWSM, the VLANs are
stored in the supervisor engine database and are sent to the FWSM as soon as they are added to the
switch.
The VLANs cannot be reserved VLANs.
– Cisco IOS software
To add the VLAN, enter the vlan vlan_number command.
– Catalyst operating system software
To add the VLAN, enter the set vlan vlan_number command.
2.
Assign the VLANs to switch ports.
– Cisco IOS software
To assign a VLAN to a port, enter:
router(config)# interface type slot/port
router(config-if)# switchport
router(config-if)# switchport mode access
router(config-if)# switchport access vlan vlan_id
– Catalyst operating system software
To assign a VLAN to a port, enter the set vlan vlan_number mod/ports command. This
command both creates the VLAN (if you have not already done so) and assigns it to a port.
Note
3.
If you are using FWSM failover within the same switch chassis, do not assign the VLAN(s) you
are reserving for failover and stateful communications to a switch port. However, if you are
using failover between chassis, you must include the VLANs in the trunk port between the
chassis.
Assign VLANs to the FWSM before you assign them to the MSFC.
VLANs that do not satisfy this condition are discarded from the range of VLANs that you attempt
to assign on the FWSM. See the “Adding Switched Virtual Interfaces to the MSFC” section on
page 2-5 for more information.
Assigning VLANs in Cisco IOS Software
In Cisco IOS software, create one or more firewall VLAN groups, and then assign the groups to the
FWSM. For example, you can assign all the VLANs to one group, or you can create an inside group and
an outside group, or you can create a group for each customer.
You cannot assign the same VLAN to multiple firewall groups; however, you can assign multiple firewall
groups to an FWSM. VLANs that you want to assign to multiple FWSMs, for example, can reside in a
separate group from VLANs that are unique to each FWSM.
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Assigning VLANs to the Firewall Services Module
To assign VLANs to the FWSM, follow these steps:
Step 1
To assign VLANs to a firewall group, enter the following command:
Router(config)# firewall vlan-group firewall_group vlan_range
The vlan_range can be one or more VLANs (1 to 1000 and from 1025 to 4094) identified in one of the
following ways:
•
A single number (n)
•
A range (n-x)
Separate numbers or ranges by commas. For example, enter the following numbers:
5,7-10,13,45-100
Note
Step 2
Routed ports and WAN ports consume internal VLANs, so it is possible that VLANs in the 1020-1100
range might already be in use.
To assign the firewall groups to the FWSM, enter the following command:
Router(config)# firewall module module_number vlan-group firewall_group
The firewall_group is one or more group numbers:
•
A single number (n)
•
A range (n-x)
Separate numbers or ranges by commas. For example, enter the following numbers:
5,7-10
This example shows how you can create three firewall VLAN groups: one for each FWSM, and one that
includes VLANs assigned to both FWSMs. See the “Prerequisites” section on page 2-3 for more
information about adding VLANs to the switch.
Router(config)# vlan 55-57,70-85,100
Router(config-vlan)# exit
Router(config)# firewall vlan-group 50 55-57
Router(config)# firewall vlan-group 51 70-85
Router(config)# firewall vlan-group 52 100
Router(config)# firewall module 5 vlan-group 50,52
Router(config)# firewall module 8 vlan-group 51,52
To view the group configuration, enter the following command:
Router# show firewall vlan-group
Group vlans
----- -----50 55-57
51 70-85
52 100
To view VLAN group numbers for all modules, enter the following command:
Router# show firewall module
Module Vlan-groups
5
50,52
8
51,52
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Adding Switched Virtual Interfaces to the MSFC
Assigning VLANs in Catalyst Operating System Software
In Catalyst operating system software, you assign a list of VLANs to the FWSM. You can assign the
same VLAN to multiple FWSMs if desired.
To assign VLANs to the FWSM, enter the following command:
Console> (enable) set vlan vlan_list firewall-vlan mod_num
The vlan_list can be one or more VLANs (1 to 1000 and from 1025 to 4094) identified in one of the
following ways:
•
A single number (n)
•
A range (n-x)
Separate numbers or ranges by commas. For example:
5,7-10,13,45-100
Note
Routed ports and WAN ports consume internal VLANs, so it is possible that VLANs in the 1020-1100
range might already be in use.
This example shows a typical configuration:
Console>
Console>
Console>
Console>
Console>
(enable)
(enable)
(enable)
(enable)
(enable)
set
set
set
set
set
vlan
vlan
vlan
vlan
vlan
55-57
70-85
100
55-57,100 firewall-vlan 5
70-85,100 firewall-vlan 8
To view the VLANs assigned to the FWSM, enter the following command:
Console> show vlan firewall-vlan 5
Secured vlans by firewall module 5
55-57, 100
Adding Switched Virtual Interfaces to the MSFC
A VLAN defined on the MSFC is called a switched virtual interface (SVI). If you assign the VLAN used
for the SVI to the FWSM (see the “Assigning VLANs to the Firewall Services Module” section on
page 2-2), then the MSFC routes between the FWSM and other Layer 3 VLANs.
This section includes the following topics:
•
SVI Overview, page 2-6
•
Configuring SVIs for Cisco IOS Software on the Supervisor Engine, page 2-8
•
Configuring SVIs for Catalyst Operating System Software on the Supervisor Engine, page 2-9
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SVI Overview
For security reasons, by default, only one SVI can exist between the MSFC and the FWSM. For example,
if you misconfigure the system with multiple SVIs, you could accidentally allow traffic to pass around
the FWSM by assigning both the inside and outside VLANs to the MSFC. (See Figure 2-1.)
Figure 2-1
Multiple SVI Misconfiguration
Internet
Switch
VLAN 100
MSFC
VLAN 200
FWSM
VLAN 201
VLAN 201
104665
Inside
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However, you might need to bypass the FWSM in some network scenarios. Figure 2-2 shows an IPX
host on the same Ethernet segment as IP hosts. Because the FWSM in routed firewall mode only handles
IP traffic and drops other protocol traffic like IPX (transparent firewall mode can optionally allow non-IP
traffic), you might want to bypass the FWSM for IPX traffic. Make sure to configure the MSFC with an
ACL that allows only IPX traffic to pass on VLAN 201.
Figure 2-2
Multiple SVIs for IPX
Internet
Switch
VLAN 100
MSFC
VLAN 200
FWSM
VLAN 201
VLAN 201
IPX Host
IP Host
104666
Inside
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For transparent firewalls in multiple context mode, you need to use multiple SVIs because each context
requires a unique VLAN on its outside interface (See Figure 2-3). You might also choose to use multiple
SVIs in routed mode so you do not have to share a single VLAN for the outside interface.
Figure 2-3
Multiple SVIs in Multiple Context Mode
Internet
Switch
VLAN 100
VLAN 151
VLAN 152
VLAN 150
Context A
VLAN 201
Admin
Network
Context B
VLAN 202
Inside
Customer A
Context C
VLAN 203
Inside
Customer B
VLAN 204
Inside
Customer C
104667
Admin
Context
VLAN 153
Configuring SVIs for Cisco IOS Software on the Supervisor Engine
If you are running Cisco IOS software on the supervisor engine, follow these steps to add an SVI to the
MSFC:
Step 1
(Optional) To allow you to add more than one SVI to the FWSM, enter the following command:
Router(config)# firewall multiple-vlan-interfaces
Step 2
To add a VLAN interface to the MSFC, enter the following command:
Router(config)# interface vlan vlan_number
Step 3
To set the IP address for this interface on the MSFC, enter the following command:
Router(config-if)# ip address address mask
Step 4
To enable the interface, enter the following command:
Router(config-if)# no shut
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This example shows a typical configuration with multiple SVIs:
Router(config)# vlan 55-57,70-85
Router(config-vlan)# exit
Router(config)# firewall vlan-group 50 55-57
Router(config)# firewall vlan-group 51 70-85
Router(config)# firewall module 8 vlan-group 50-51
Router(config)# firewall multiple-vlan-interfaces
Router(config)# interface vlan 55
Router(config-if)# ip address 10.1.1.1 255.255.255.0
Router(config-if)# no shut
Router(config-if)# interface vlan 56
Router(config-if)# ip address 10.1.2.1 255.255.255.0
Router(config-if)# no shut
Router(config-if)# end
Router#
To view your SVI configuration, enter the following command:
Router# show int vlan 55
Vlan55 is up, line protocol is up
Hardware is EtherSVI, address is 0008.20de.45ca (bia 0008.20de.45ca)
Internet address is 55.1.1.1/24
MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
ARP type:ARPA, ARP Timeout 04:00:00
Last input never, output 00:00:08, output hang never
Last clearing of "show interface" counters never
Input queue:0/75/0/0 (size/max/drops/flushes); Total output drops:0
Queueing strategy:fifo
Output queue :0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
L2 Switched:ucast:196 pkt, 13328 bytes - mcast:4 pkt, 256 bytes
L3 in Switched:ucast:0 pkt, 0 bytes - mcast:0 pkt, 0 bytes mcast
L3 out Switched:ucast:0 pkt, 0 bytes
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
4 packets output, 256 bytes, 0 underruns
0 output errors, 0 interface resets
0 output buffer failures, 0 output buffers swapped out
Configuring SVIs for Catalyst Operating System Software on the Supervisor
Engine
If you are running Catalyst operating system software on the supervisor engine, follow these steps to add
an SVI to the MSFC:
Step 1
(Optional) To allow you to add more than one SVI to the FWSM. enter the following command:
Console> (enable) set firewall multiple-vlan-interfaces enable
To disable this setting, enter the following command:
Console> (enable) set firewall multiple-vlan-interfaces disable
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Step 2
To access the MSFC interface, enter one of the following commands:
Console> (enable) switch console
or
Console> (enable) session {15 | 16}
If you are accessing the switch using Telnet or SSH, you must use the session command.
Step 3
To enter enable mode and then configuration mode on the MSFC, enter the following commands:
Router> enable
Router# configure terminal
Step 4
To add a VLAN interface to the MSFC, enter the following command:
Router(config)# interface vlan vlan_number
Step 5
To set the IP address for this interface on the MSFC, enter the following command:
Router(config-if)# ip address address mask
Step 6
To enable the interface, enter the following command:
Router(config-if)# no shut
Step 7
To return to privileged EXEC mode, enter the following command:
Router(config-if)# end
Step 8
To return to the switch CLI, enter Ctrl-C three times.
This example shows a typical configuration:
Console> (enable) set vlan 55-57
Console> (enable) set vlan 70-85
Console> (enable) set vlan 55-57,70-85 firewall-vlan 8
Console> (enable) set firewall multiple-vlan-interfaces enable
Console> (enable) switch console
Router> enable
Password: ******
Router# configure terminal
Router(config)# interface vlan 55
Router(config-if)# ip address 10.1.1.1 255.255.255.0
Router(config-if)# no shut
Router(config-if)# interface vlan 56
Router(config-if)# ip address 10.1.2.1 255.255.255.0
Router(config-if)# no shut
Router(config-if)# end
Router# ^C^C^C
Console> (enable)
To view your SVI configuration, enter the following command at the MSFC prompt:
Router# show int vlan 55
Vlan55 is up, line protocol is up
Hardware is EtherSVI, address is 0008.20de.45ca (bia 0008.20de.45ca)
Internet address is 55.1.1.1/24
MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
ARP type:ARPA, ARP Timeout 04:00:00
Last input never, output 00:00:08, output hang never
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Customizing the FWSM Internal Interface
Last clearing of "show interface" counters never
Input queue:0/75/0/0 (size/max/drops/flushes); Total output drops:0
Queueing strategy:fifo
Output queue :0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
L2 Switched:ucast:196 pkt, 13328 bytes - mcast:4 pkt, 256 bytes
L3 in Switched:ucast:0 pkt, 0 bytes - mcast:0 pkt, 0 bytes mcast
L3 out Switched:ucast:0 pkt, 0 bytes
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
4 packets output, 256 bytes, 0 underruns
0 output errors, 0 interface resets
0 output buffer failures, 0 output buffers swapped out
Customizing the FWSM Internal Interface
The connection between the FWSM and the switch is a 6-GB 802.1Q trunking EtherChannel. This
EtherChannel is automatically created when you install the FWSM. On the FWSM side, two network
processors (NPs) connect to three Gigabit Ethernet interfaces each, and these interfaces comprise the
EtherChannel. The switch distributes traffic to the interfaces in the EtherChannel according to a
distribution algorithm based on session information; load sharing is not performed on a per-packet basis,
but rather on a flow basis. In some cases, the algorithm assigns traffic unevenly between the interfaces
and, therefore, between the two NPs. Aside from not utilizing the full processing potential of the FWSM,
consistent inequity can result in unexpected behavior when you apply resource management to multiple
contexts. (See the “Configuring a Class” section on page 5-14 for more information.) To make changes
to the algorithm see the command for your operating system:
•
Cisco IOS Software
Router(config)# port-channel load-balance {dst-ip | dst-mac | dst-port | src-dst-ip |
src-dst-mac | src-dst-port | src-ip | src-mac | src-port}
The default is src-dst-ip.
•
Catalyst operating system software
Console> (enable) set port channel all distribution {ip | mac | session |
ip-vlan-session} [source | destination | both]
The default is ip both.
Configuring the Switch for Failover
To configure the switch for failover, see the following topics:
•
Assigning VLANs to the Secondary Firewall Services Module, page 2-12
•
Adding a Trunk Between a Primary Switch and Secondary Switch, page 2-12
•
Ensuring Compatibility with Transparent Firewall Mode, page 2-12
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Managing the Firewall Services Module Boot Partitions
Assigning VLANs to the Secondary Firewall Services Module
Because both units require the same access to the inside and outside networks, you must assign the same
VLANs to both FWSMs on the switch(es). See the “Assigning VLANs to the Firewall Services Module”
section on page 2-2.
Adding a Trunk Between a Primary Switch and Secondary Switch
If you are using inter-switch failover (see the “Module Placement” section on page 15-4), then you need
to configure an 802.1Q VLAN trunk between the two switches. The trunk should have the following
characteristics:
•
The trunk must carry all firewall VLANs, including the failover and state VLANs.
•
Because this trunk also accommodates FWSM traffic when a module fails, this trunk should be at
least as large as the maximum amount of traffic you expect to be inspected by the FWSM. The
FWSM has an internal 6-Gbps EtherChannel to the switch, so if the FWSM runs at full capacity, the
trunk between the two devices needs to include at least six 1-Gbps interfaces. EtherChannel
aggregates the bandwidth of up to eight compatibly configured ports into a single logical link. If you
do not have the ports to spare, you can create a smaller trunk; however, you might experience
decreased performance.
•
The trunk should have QoS enabled so that failover VLAN packets, which have the CoS value of 5
(higher priority), are treated with higher priority in these ports.
To configure the EtherChannel and trunk, see the documentation for your switch.
Ensuring Compatibility with Transparent Firewall Mode
To avoid loops when you use failover in transparent mode, use switch software that supports BPDU
forwarding. Catalyst operating system software release 8.2(1) and Cisco IOS software Release
12.2(17)SXA allow BPDUs automatically.
Managing the Firewall Services Module Boot Partitions
This section describes how to reset the FWSM from the switch, and how to manage the boot partitions
on the Compact Flash card. This section includes the following topics:
•
Flash Memory Overview, page 2-13
•
Setting the Default Boot Partition, page 2-13
•
Resetting the FWSM or Booting from a Specific Partition, page 2-13
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Flash Memory Overview
The FWSM has a 128-MB Compact Flash card (“Flash memory”) that stores the operating system,
configurations, and other data. The Flash memory includes six partitions, called cf:n in Cisco IOS
software and Catalyst operating system software commands:
•
Maintenance partition (cf:1)—Contains the maintenance image. Use the maintenance partition to
upgrade or install application images if you cannot boot into the application partition, to reset the
application image password, or to display the crash dump information.
•
Network configuration partition (cf:2)—Contains the network configuration of the maintenance
image. The maintenance partition requires IP settings so that the FWSM can reach the TFTP server
to download software images.
•
Crash dump partition (cf:3)—Stores the crash dump information.
•
Application partitions (cf:4 and cf:5)—Stores the software image, system configuration, and PDM
for FWSM. By default, Cisco installs the images on cf:4. You can use cf:5 as a test partition. For
example, if you want to upgrade your software, you can install the new software on cf:5, but
maintain the old software as a backup in case you have problems.
•
Security context partition (cf:6)—64 MB are dedicated to this partition, which stores security
context configurations (if desired) and RSA keys in a navigable file system. All other partitions do
not have file systems that allow you to perform common tasks such as listing files. This partition is
called disk when using the copy command.
Setting the Default Boot Partition
By default, the FWSM boots from the cf:4 application partition. However, you can choose to boot from
the cf:5 application partition or into the cf:1 maintenance partition. To change the default boot partition,
enter the command for your operating system:
•
Cisco IOS software
Router(config)# boot device module mod_num cf:n
Where n is 1 (maintenance), 4 (application), or 5 (application).
•
Catalyst operating system software
Console> (enable) set boot device cf:n mod_num
Where n is 1 (maintenance), 4 (application), or 5 (application).
Resetting the FWSM or Booting from a Specific Partition
This section describes how to reset the FWSM or boot from a specific partition. You might need to reset
the FWSM if you cannot reach it through the CLI or an external Telnet session. You might need to boot
from a non-default boot partition if you need to access the maintenance partition or if you want to boot
from a different software image in the backup application partition. The maintenance partition is
valuable for troubleshooting.
The reset process might take several minutes.
For Cisco IOS software, when you reset the FWSM, you can also choose to run a full memory test. When
the FWSM initially boots, it only runs a partial memory test. A full memory test takes approximately
six minutes.
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Managing the Firewall Services Module Boot Partitions
To reset the FWSM, see the section for your operating system:
Note
•
Resetting the FWSM in Cisco IOS Software, page 2-14
•
Resetting the FWSM in Catalyst Operating System Software, page 2-14
To reload the FWSM when you are logged into the FWSM, enter reload or reboot. You cannot boot from
a non-default boot partition with these commands.
Resetting the FWSM in Cisco IOS Software
To reset the FWSM from the switch CLI, enter the following command:
Router# hw-module module mod_num reset [cf:n] [mem-test-full]
The cf:n argument is the partition, either 1 (maintenance), 4 (application), or 5 (application). If you do
not specify the partition, the default partition is used (typically cf:4).
The mem-test-full option runs a full memory test, which takes approximately 6 minutes.
This example shows how to reset the FWSM installed in slot 9. The default boot partition is used.
Router# hw-mod mod 9 reset
Proceed with reload of module? [confirm] y
% reset issued for module 9
Router#
00:26:55:%SNMP-5-MODULETRAP:Module 9 [Down] Trap
00:26:55:SP:The PC in slot 8 is shutting down. Please wait ...
Resetting the FWSM in Catalyst Operating System Software
To reset the FWSM from the switch CLI, enter the following command:
Console> (enable) reset mod_num [cf:n]
where cf:n is the partition, either 1 (maintenance), 4 (application), or 5 (application). If you do not
specify the partition, the default partition is used (typically cf:4).
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Connecting to the Firewall Services Module and
Managing the Configuration
This chapter tells how to access the Firewall Services Module (FWSM) command-line interface (CLI)
and manage the configuration, and contains the following sections:
•
Sessioning and Logging into the Firewall Services Module, page 3-1
•
Managing the Configuration at the CLI, page 3-3
Sessioning and Logging into the Firewall Services Module
This section describes how to connect or “session,” to the FWSM from the switch command line, log in,
access privileged mode, and then configuration mode so you can configure the FWSM. The FWSM does
not have an external console port, you must session into the FWSM for initial configuration. Later, when
you configure interfaces and IP addresses on the FWSM itself, you can access the FWSM CLI remotely
through an FWSM interface. See Chapter 11, “Allowing Remote Management,” for more information.
Without any additional configuration for user authentication, the login method consists of logging in as
the default user:
Caution
Note
1.
The login password lets you access unprivileged mode.
2.
To access configuration commands, you must enter privileged mode, which requires a second
password (privileged mode is also known as enable mode).
3.
From privileged mode, you can access configuration mode, which does not require a password.
Management access to the FWSM causes a degradation in performance. We recommend that you avoid
accessing the FWSM when high network performance is critical.
For multiple context mode, see the “Logging into the FWSM in Multiple Context Mode” section on
page 5-9 for more information about logging into security contexts.
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Sessioning and Logging into the Firewall Services Module
This section describes how to log in as the default user. For information about advanced configuration
options for login access, see the sections for the following features:
•
User authentication for CLI access—See the “Configuring Authentication for CLI Access” section
on page 12-8. You can configure user authentication for accessing the CLI from Telnet, SSH, and
HTTP (for the PDM for FWSM). You can also require authentication for the enable command.
•
Command authorization—See the “Configuring Command Authorization” section on page 12-10 or
“Configuring TACACS+ Command Authorization” section on page 12-13. Use command
authorization (the authority to enter commands) in conjunction with CLI or enable authentication.
To session into the FWSM, log in, access privileged mode, and then configuration mode, follow these
steps:
Step 1
Session into the FWSM using the command appropriate for your switch operating system:
•
Cisco IOS software
Router# session slot number processor 1
•
Catalyst operating system software
Console> (enable) session module_number
For multiple context mode, when you session into the FWSM, you access the system configuration. See
Chapter 5, “Managing Security Contexts,” for more information.
Step 2
Log into the FWSM by entering the login password at the following prompt:
FWSM passwd:
By default, the password is cisco.
To change the password, see the “Changing the Passwords” section on page 6-1.
Step 3
To access privileged mode, enter the following command:
FWSM> enable
This command accesses the highest privilege level.
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
Passwords” section on page 6-1 to change the enable password.
The prompt changes to:
FWSM#
To exit privileged mode, enter disable. You can also enter exit or quit to exit the current access mode
(privileged mode, configuration mode, etc.).
Step 5
To access configuration mode, enter the following command:
FWSM# configure terminal
The prompt changes to the following:
FWSM(config)#
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Managing the Configuration at the CLI
Managing the Configuration at the CLI
The FWSM loads the configuration from a text file, called the startup configuration. This file resides in
the flash partition. 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 5, “Managing Security Contexts.”
See the “Backing Up the Configuration” section on page 16-7 for more information about managing
configuration files.
This section includes the following topics:
•
Saving Configuration Changes, page 3-3
•
Viewing the Configuration, page 3-3
•
Clearing and Removing Configuration Settings, page 3-4
•
Creating Text Configuration Files Offline, page 3-4
Saving Configuration Changes
To save your running configuration to the startup configuration, enter the following command:
FWSM# copy running-config startup-config
For multiple context mode, context startup configurations can reside on external servers. In this case, the
FWSM saves the configuration back to the server you identified in the context URL, except for an HTTP
or HTTPS URL, which do not allow you to save the configuration to the server.
Note
The copy running-config startup-config command is equivalent to the write memory command.
Viewing the Configuration
The following commands allow you to view the running and startup configurations.
•
To view the running configuration, enter the following command:
FWSM# show running-config
•
To view the startup configuration, enter the following command:
FWSM# show startup-config
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Managing the Configuration at the CLI
Clearing and Removing Configuration Settings
To erase settings, enter one of the following commands.
•
To clear all the configuration for a specified command and all its subcommands, enter the following
command:
FWSM# clear configurationcommand [subconfigurationcommand]
This command clears all the current configuration for the specified configuration command. If you
only want to clear the configuration for a specific subcommand, you can enter a value for
subconfigurationcommand.
For example, to clear the configuration for all aaa commands, enter the following command:
FWSM# clear aaa
To clear the configuration for only aaa authentication commands, enter the following command:
FWSM# clear aaa authentication
•
To disable the specific parameters or options of a command or subcommand, enter the following
command:
FWSM# no configurationcommand [subconfigurationcommand] 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:
FWSM# no nat (inside) 1
•
To erase the startup configuration, enter the following command:
FWSM# write erase
•
To erase the running configuration, enter the following command:
FWSM# 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 FWSM; 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 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 FWSM Flash memory. See the “Downloading a Text
Configuration” section on page 16-6 for information on downloading the configuration file to the
FWSM.
In most cases, commands described in this guide are preceded by a CLI prompt. The prompt in the
following example is “FWSM(config)#”:
FWSM(config)# class gold
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Managing the Configuration at the CLI
In the text configuration file you are not prompted to enter commands, so the prompt is omitted as
follows:
class gold
See the “Text Configuration Files” section on page C-4 for more information about formatting the file.
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Configuring the Firewall Mode
This chapter describes how to set the firewall mode to either routed mode or transparent mode, and
includes the following sections:
•
Firewall Mode Overview, page 4-1
•
Setting the Firewall Mode, page 4-16
Firewall Mode Overview
The FWSM can run in two firewall modes:
•
Routed mode
•
Transparent mode
In routed mode, the FWSM is considered to be a router hop in the network. It performs NAT between
connected networks, and can use OSPF or passive RIP (in single context mode). Routed mode supports
up to 256 interfaces per context or in single mode, with a maximum of 1000 interfaces divided between
all contexts. Each interface is on a different subnet. You can share interfaces between contexts.
In transparent mode, the FWSM acts like a “bump in the wire,” or a “stealth firewall,” and is not a router
hop. The FWSM connects the same network on its inside and outside interfaces, but each interface must
be on a different VLAN. No dynamic routing protocols or NAT are required. However, like routed mode,
transparent mode also requires ACLs to allow traffic through. Transparent mode can allow certain types
of traffic in an ACL that are blocked by routed mode, including unsupported routing protocols and
multicast traffic. Transparent mode can also optionally use EtherType ACLs to allow non-IP traffic.
Transparent mode only supports two interfaces, an inside interface and an outside interface.
This section includes the following topics:
•
Routed Mode Overview, page 4-1
•
Transparent Mode Overview, page 4-8
Routed Mode Overview
This section includes the following topics:
•
IP Routing Support, page 4-2
•
Network Address Translation, page 4-2
•
How Data Moves Through the FWSM in Routed Firewall Mode, page 4-3
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Firewall Mode Overview
IP Routing Support
The FWSM 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 (in passive mode).
Multiple context mode supports static routes only. We recommend using the advanced routing
capabilities of the upstream and downstream routers, such as the MSFC, instead of relying on the FWSM
for extensive routing needs.
Network Address Translation
NAT substitutes the local address on a packet with a global address that is routable on the destination
network. In routed mode, you typically configure NAT for inside hosts that access an outside network,
but you can optionally bypass NAT if you are using routable addresses.
Some of the benefits of NAT include the following:
•
You can use private addresses on your inside networks. Private addresses are not able to be routed
on the Internet. See the “Private Networks” section on page D-2 for more information.
•
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 4-1 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 firewall receives the packet. The firewall then translates the global address to the local address before
sending it on to the user.
See Chapter 9, “Configuring Network Address Translation,” for more information.
Figure 4-1
NAT Example
Web Server
www.cisco.com
Outside
209.165.201.2
Originating
Packet
FWSM
Source Addr Translation
10.1.2.27
209.165.201.10
Responding
Packet
Dest Addr Translation
209.165.201.10
10.1.2.27
10.1.2.1
10.1.2.27
104669
Inside
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How Data Moves Through the FWSM in Routed Firewall Mode
This section describes how data moves through the FWSM in routed firewall mode, and includes the
following topics:
•
An Inside User Visits a Website, page 4-3
•
An Outside User Visits a Website on the DMZ, page 4-4
•
An Inside User Visits a Website on the DMZ, page 4-5
•
An Outside User Attempts to Access an Inside Host, page 4-6
•
An DMZ User Attempts to Access an Inside Host, page 4-8
An Inside User Visits a Website
Figure 4-2 shows an inside user accessing an outside website.
Figure 4-2
Inside to Outside
www.cisco.com
Outside
Switch
209.165.201.2
FWSM
Source Addr Translation
10.1.2.27
209.165.201.10
Inside
User
10.1.2.27
10.1.1.1
DMZ
Web Server
10.1.1.3
104656
10.1.2.1
The steps below describe how data moves through the FWSM (see Figure 4-2):
1.
The user on the inside network requests a web page from www.cisco.com.
2.
The FWSM receives the packet, and because it is a new session, the FWSM verifies that the packet
is allowed according to the terms of the security policy (ACLs, filters, AAA).
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Firewall Mode Overview
For multiple context mode, the FWSM first classifies the packet according to either a unique VLAN
or a unique destination address. In this case, the VLAN would be unique; the www.cisco.com
IP address is not located uniquely within a context and is not a unique destination address.
3.
The FWSM 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 FWSM then records that a session is established and forwards the packet from the outside
interface.
5.
When www.cisco.com responds to the request, the packet goes through the FWSM, and because the
session is already established, the packet bypasses the many lookups associated with a new
connection. The fast path performs NAT by translating the global destination address to the local
user address, 10.1.2.27.
6.
The FWSM forwards the packet to the inside user.
An Outside User Visits a Website on the DMZ
Figure 4-3 shows an outside user accessing the DMZ website.
Figure 4-3
Outside to DMZ
User
Outside
Switch
209.165.201.2
Dest Addr Translation
209.165.201.3
10.1.1.3
FWSM
Inside
10.1.1.1
DMZ
Web Server
10.1.1.3
104681
10.1.2.1
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Firewall Mode Overview
The steps below describe how data moves through the FWSM (see Figure 4-3):
1.
A user on the outside network requests a web page from the DMZ website using the global
destination address of 209.165.201.3, which is on the outside interface subnet.
2.
The FWSM receives the packet, and because it is a new session, the FWSM verifies that the packet
is allowed according to the terms of the security policy (ACLs, filters, AAA).
For multiple context mode, the FWSM first classifies the packet according to either a unique VLAN
or a unique destination address. In this case, even if the VLAN is not unique, the classifier “knows”
that the DMZ web server address belongs to a certain context because of the NAT configuration.
3.
The FWSM translates the destination address to the local address 10.1.1.3.
4.
The FWSM then adds a session entry to the fast path and forwards the packet from the DMZ
interface.
5.
When the DMZ website responds to the request, the packet goes through the FWSM and because
the session is already established, the packet bypasses the many lookups associated with a new
connection. The fast path performs NAT by translating the local source address to 209.165.201.3.
6.
The FWSM forwards the packet to the outside user.
An Inside User Visits a Website on the DMZ
Figure 4-4 shows an inside user accessing the DMZ website.
Figure 4-4
Inside to DMZ
Outside
Switch
209.165.201.2
FWSM
Inside
User
10.1.2.27
Source Addr Translation
10.1.2.27
10.1.1.15
10.1.1.1
DMZ
Web Server
10.1.1.3
104655
10.1.2.1
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Firewall Mode Overview
The steps below describe how data moves through the FWSM (see Figure 4-4):
1.
A user on the inside network requests a web page from the DMZ website using the destination
address of 10.1.1.3.
Because the DMZ is a lower security interface, the inside user can use the untranslated local address
of the web server.
2.
The FWSM receives the packet, and because it is a new session, the FWSM verifies that the packet
is allowed according to the terms of the security policy (ACLs, filters, AAA).
For multiple context mode, the FWSM first classifies the packet according to either a unique VLAN
or a unique destination address. In this case, the VLAN would be unique because the destination is
on a different interface in the same context.
3.
The FWSM translates the local source address to the global address 10.1.1.15, which is on the DMZ
subnet.
4.
The FWSM then records that a session is established and forwards the packet out of the DMZ
interface.
5.
When the DMZ web server responds to the request, the packet goes through the fast path, which
allows the packet to bypass the many lookups associated with a new connection. The fast path
performs NAT by translating the global destination address to the local address of the user,
10.1.2.27.
6.
The FWSM forwards the packet to the inside user.
An Outside User Attempts to Access an Inside Host
Figure 4-5 shows an outside user attempting to access the inside network.
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Figure 4-5
Outside to Inside
www.cisco.com
Outside
Switch
209.165.201.2
FWSM
Inside
User
10.1.2.27
10.1.1.1
DMZ
104682
10.1.2.1
The steps below describe how data moves through the FWSM (see Figure 4-5):
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 FWSM receives the packet, and because it is a new session, the FWSM verifies if the packet is
allowed according to the security policy (ACLs, filters, AAA).
3.
The packet is denied, and the FWSM drops the packet and logs the connection attempt.
If the outside user is attempting to attack the inside network, the FWSM employs many technologies
to determine if a packet is valid for an already established session. See the “Other Protection
Features” section on page 1-6 for more information.
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An DMZ User Attempts to Access an Inside Host
Figure 4-6 shows a user in the DMZ attempting to access the inside network.
Figure 4-6
DMZ to Inside
Outside
Switch
209.165.201.2
FWSM
10.1.1.1
Inside
User
10.1.2.27
DMZ
Web Server
10.1.1.3
104641
10.1.2.1
The steps below describe how data moves through the FWSM (see Figure 4-6):
1.
A user on the DMZ network attempts to reach an inside host. The DMZ host might know the real
address of an inside host, and because the DMZ does not have to route the traffic on the internet, the
private addressing scheme does not prevent routing.
2.
The FWSM receives the packet, and because it is a new session, the FWSM verifies if the packet is
allowed according to the security policy (ACLs, filters, AAA).
3.
The packet is denied, and the FWSM drops the packet and logs the connection attempt.
Transparent Mode Overview
This section describes transparent firewall mode, and includes the following topics:
•
Transparent Firewall Features, page 4-9
•
Using the Transparent Firewall in Your Network, page 4-10
•
Transparent Firewall Guidelines, page 4-11
•
How Data Moves Through the Transparent Firewall, page 4-12
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Transparent Firewall Features
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. The Firewall
Services Module (FWSM) connects the same network on its inside and outside ports but uses different
VLANs on the inside and outside.
Because the firewall is not a routed hop, you can easily introduce a transparent firewall into an existing
network. You assign different VLANs to each interface, and IP readdressing is unnecessary.
Maintenance is facilitated because there are no complicated routing patterns to troubleshoot and no NAT
configuration.
Even though transparent mode acts as a bridge, Layer 3 traffic, such as IP traffic, cannot pass through
the FWSM unless you explicitly permit it with an extended access control list (ACL). (See the “Adding
an Extended Access Control List” section on page 10-13.)
In routed mode, some types of traffic cannot pass through the FWSM even if you allow it in an ACL.
The transparent firewall, however, can allow any traffic through using either an extended ACL (for IP
traffic) or an EtherType ACL (for non-IP traffic. See the “Adding an EtherType Access Control List”
section on page 10-16 for more information).
Note
The transparent mode FWSM does not pass Cisco Discovery Protocol (CDP) packets.
For example, you can allow multicast traffic such as that created by IPTV using an extended ACL. You
can also establish routing protocol adjacencies through a transparent firewall; for example, you can allow
OSPF, RIP, EIGRP, or BGP traffic through based on an extended ACL. Likewise, protocols like HSRP
or VRRP can pass through the FWSM.
Non-IP traffic (for example IPX, BPDUs, and MPLS) can be configured to go through using an
EtherType ACL.
When the FWSM 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 FWSM-originated traffic. For example, if your syslog server is located on a remote
network, you must use a static route so the FWSM can reach that subnet. See the “Configuring Static
Routes” section on page 8-3 for more information.
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Using the Transparent Firewall in Your Network
Figure 4-7 shows a typical transparent firewall network. While the outside devices are on the same
subnet as the inside devices, the VLANs are different. The inside router and hosts appear to be directly
connected to the outside router. However, no traffic can bypass the FWSM because it must route
between the two VLANs.
Figure 4-7
Transparent Firewall Network
Internet
Switch
10.1.1.1
VLAN 100
FWSM
10.1.1.2
Network A
VLAN 200
10.1.1.3
Network B
104692
192.168.1.2
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Transparent Firewall Guidelines
Follow these guidelines when planning your transparent firewall network:
•
The transparent FWSM uses an inside interface and an outside interface only.
•
Each directly connected network must be on the same subnet.
•
A management IP address is required for each context, even if you do not intend to use Telnet to the
context.
The FWSM uses this IP address as the source address for packets originating on the FWSM, such
as system messages or AAA communications.
The management IP address must be on the same subnet as the connected network.
•
Do not specify the FWSM management IP address as the default gateway for connected devices;
devices need to specify the router on the other side of the FWSM as the default gateway.
•
Each interface must be a different VLAN interface.
•
For multiple context mode, each context must use different VLANs; you cannot share a VLAN
across contexts.
•
For multiple context mode, each context can use the same (overlapping) subnet or different subnets.
Make sure that the upstream router performs NAT if you use overlapping subnets.
•
Dynamic routing protocols are neither required nor supported.
You can, however, add static routes.
•
NAT is not supported.
NAT is performed on the upstream router. However, you can configure some parameters available
only in the static command. See the “Configuring Connection Limits for Non-NAT Configurations”
section on page 6-10 for more information.
•
You must use an extended ACL to allow Layer 3 traffic, such as IP traffic, through the FWSM.
You can also optionally use an EtherType ACL to allow non-IP traffic through.
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How Data Moves Through the Transparent Firewall
Figure 4-8 shows a typical transparent firewall implementation with an inside network that contains a
public web server. The FWSM has an ACL so that the inside users can access Internet resources. Another
ACL allows the outside users to access only the web server on the inside network.
Figure 4-8
Typical Transparent Firewall Data Path
www.cisco.com
Internet
Switch
209.165.201.2
VLAN 100
FWSM
209.165.201.6
VLAN 200
Host
209.165.201.3
Web Server
209.165.200.225
104696
209.165.200.230
The following sections describe how data moves through the FWSM:
•
An Inside User Visits a Website, page 4-13
•
An Outside User Visits a Website on the Inside Network, page 4-14
•
An Outside User Attempts to Access an Inside Host, page 4-15
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An Inside User Visits a Website
Figure 4-2 shows an inside user accessing an outside website.
Figure 4-9
Inside to Outside
www.cisco.com
Internet
Switch
209.165.201.2
VLAN 100
FWSM
209.165.201.6
Host
209.165.201.3
104693
VLAN 200
The steps below describe how data moves through the FWSM (see Figure 4-2):
1.
The user on the inside network requests a web page from www.cisco.com.
2.
The FWSM receives the packet on VLAN 200 and, because it is a new session, it verifies that the
packet is allowed according to the terms of the security policy (ACLs, filters, AAA).
For multiple context mode, the FWSM first classifies the packet according to either a unique VLAN
or a unique destination address. In this case, the VLAN would be unique. For transparent firewall
mode, each context has a unique VLAN on the inside and outside, so the IP address would not be
considered.
3.
The FWSM records that a session is established.
4.
If the destination MAC address is in its table, the FWSM forwards the packet out of the outside
interface on VLAN 100.
If the destination MAC address is not in the FWSM table, the FWSM attempts to discover the MAC
address by sending an ARP request and a ping. The first packet is dropped.
5.
When the web server responds to the request, the packet goes through the FWSM, and because the
session is already established, the packet bypasses the many lookups associated with a new
connection.
6.
The FWSM forwards the packet to the inside user.
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An Outside User Visits a Website on the Inside Network
Figure 4-3 shows an outside user accessing the inside website.
Figure 4-10 Outside to Inside
Host
Internet
Switch
209.165.201.2
VLAN 100
FWSM
209.165.201.6
VLAN 200
209.165.201.1
Web Server
209.165.200.225
104694
209.165.200.230
The steps below describe how data moves through the FWSM (see Figure 4-3):
1.
A user on the outside network requests a web page from the inside website.
2.
The FWSM receives the packet on VLAN 100 and, because it is a new session, it verifies that the
packet is allowed according to the terms of the security policy (ACLs, filters, AAA).
For multiple context mode, the FWSM first classifies the packet according to either a unique VLAN
or a unique destination address. In this case, the VLAN would be unique. For transparent firewall
mode, each context has a unique VLAN on the inside and outside, so the IP address would not be
considered.
3.
The FWSM records that a session is established.
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4.
If the destination MAC address is in its table, the FWSM forwards the packet out of the inside
interface on VLAN 200.
If the destination MAC address is not in the FWSM table, the FWSM attempts to discover the MAC
address by sending an ARP request and a ping. The first packet is dropped.
5.
When the website responds to the request, the packet goes through the FWSM, and because the
session is already established, the packet bypasses the many lookups associated with a new
connection.
6.
The FWSM forwards the packet to the outside user.
An Outside User Attempts to Access an Inside Host
Figure 4-5 shows an outside user attempting to access a host on the inside network.
Figure 4-11 Outside to Inside
Host
Internet
Switch
209.165.201.2
VLAN 100
FWSM
209.165.201.6
Host
209.165.201.3
104695
VLAN 200
The steps below describe how data moves through the FWSM (see Figure 4-5):
1.
A user on the outside network attempts to reach an inside host.
2.
The FWSM receives the packet and, because it is a new session, it verifies if the packet is allowed
according to the terms of the security policy (ACLs, filters, AAA).
3.
The packet is denied, and the FWSM drops the packet.
4.
If the outside user is attempting to attack the inside network, the FWSM employs many technologies
to determine if a packet is valid for an already established session. See the “Other Protection
Features” section on page 1-6 for more information.
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Setting the Firewall Mode
Setting the Firewall Mode
You can set the FWSM 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 configuration.
When you change modes, the FWSM 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 the Configuration” section on page 16-7 for more information.
If you download a text configuration to the FWSM that changes the mode with the firewall transparent
command (see below), be sure to put the command at the top of the configuration; the FWSM 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 FWSM clears all the preceding lines in the
configuration.
•
To set the mode to transparent, enter the following command in the system execution space:
FWSM(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:
FWSM(config)# no firewall transparent
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5
Managing Security Contexts
This chapter tells how to configure multiple security contexts on the Firewall Services Module (FWSM),
and includes the following sections:
•
Security Context Overview, page 5-1
•
Enabling or Disabling Multiple Context Mode, page 5-10
•
Configuring Resource Management, page 5-11
•
Configuring a Security Context, page 5-19
•
Removing a Security Context, page 5-22
•
Changing the Admin Context, page 5-22
•
Changing Between Contexts and the System Execution Space, page 5-22
•
Changing the Security Context URL, page 5-23
•
Reloading a Security Context, page 5-24
•
Monitoring Security Contexts, page 5-24
Security Context Overview
You can partition a single FWSM into multiple virtual firewalls, known as security contexts. Each
context is an independent firewall, with its own security policy, interfaces, and administrators. Multiple
contexts are similar to having multiple stand-alone firewalls.
Each context has its own configuration that identifies the security policy, interfaces, and almost all the
options you can configure on a stand-alone firewall. If desired, you can allow individual context
administrators to implement the security policy on the context. Some resources are controlled by the
overall system administrator, such as VLANs and system resources, so that one context cannot affect
other contexts inadvertently.
The system administrator adds and manages contexts by configuring them in the system configuration,
which identifies basic settings for the FWSM. The system administrator has privileges to manage all
contexts. 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 (for
example, over an SSH connection), then that user has system administrator rights, and can access the
system execution space and all other contexts. Typically, the admin context provides network access to
network-wide resources, such as a syslog server or context configuration server.
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Security Context Overview
This section provides an overview of security contexts, and includes the following topics:
•
Common Uses for Security Contexts, page 5-2
•
Context Configuration Files, page 5-2
•
How the FWSM Classifies Packets, page 5-2
•
IP Routing Support, page 5-5
•
Sharing Resources and Interfaces Between Contexts, page 5-5
•
Logging into the FWSM in Multiple Context Mode, page 5-9
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 firewall services to many customers. By enabling
multiple security contexts on the FWSM, 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 firewall.
Context Configuration Files
Each context has its own configuration file that identifies the security policy, interfaces, and almost all
the options you can configure on a stand-alone firewall. You can store context configurations on the local
disk partition on the Flash memory card, or you can download them from a TFTP, FTP, or HTTP(S)
server.
In addition to individual security contexts, the FWSM also includes a system configuration that
identifies basic settings for the FWSM, including a list of contexts. Like the single mode configuration,
this configuration resides as the “startup” configuration in the flash partition.
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 a 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, as well as the Ethernet Out-of-Band Channel
(EOBC) to the switch, which does not require any configuration. 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 disk partition called admin.cfg. In the FWSM CLI, this context is named “admin.” If you do not
want to use admin.cfg as the admin context, you can change the admin context using the “Changing the
Admin Context” section on page 5-22.
How the FWSM Classifies Packets
Each packet that enters the FWSM must be classified, so that the FWSM can determine to which context
to send a packet. The classifier checks for the following characteristics:
•
Source interface (VLAN)
•
Destination address
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The FWSM uses the characteristic that is unique and not shared across contexts. For example, if you
share a VLAN across contexts, then the classifier uses the IP address. See the “Sharing Resources and
Interfaces Between Contexts” section on page 5-5 for more information about sharing VLANs.
The FWSM classifier only “knows” about context IP addresses that have static NAT translations or that
have active NAT translations (xlates). The classifier only looks at static statements where the global
interface matches the source interface of the packet.
You can share a VLAN interface so long as each IP address space on that VLAN is unique, or you can
have overlapping IP addresses so long as the VLANs are unique. Figure 5-1 shows multiple contexts
sharing an outside VLAN, while the inside VLANs are unique, allowing overlapping IP addresses.
Figure 5-1
Multiple Security Contexts
Internet
Switch
VLAN 200
Unique IP address
on common subnet
for each context
Classifier
VLAN 200
Context B
Context A
VLAN 201
Admin
Network
VLAN 202
Inside
Customer A
Context C
VLAN 203
Inside
Customer B
VLAN 204
Inside
Customer C
104661
Admin
Context
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Note that all new incoming traffic must be classified, even from inside networks. (See Figure 5-2.)
Figure 5-2
Incoming Traffic from Inside Networks
Internet
Switch
Unique IP address
on common subnet
for each context
VLAN 200
Admin
Context
Context A
Context B
Context C
Classifier
Admin
Network
VLAN 202
Inside
Customer A
VLAN 203
Inside
Customer B
VLAN 204
Inside
Customer C
104662
VLAN 201
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For transparent firewalls, interfaces do not have IP addresses, so you must use unique VLANs (see
Figure 5-3):
Figure 5-3
Transparent Firewall Contexts
Internet
Switch
VLAN 100
VLAN 151
VLAN 152
VLAN 150
Admin
Context
VLAN 153
Context A
Context B
Context C
Same subnet on
inside and outside
VLANs
Admin
Network
VLAN 202
Inside
Customer A
VLAN 203
Inside
Customer B
VLAN 204
Inside
Customer C
104668
VLAN 201
IP Routing Support
Security contexts support only static routes. You cannot enable OSPF or RIP in multiple context mode.
Sharing Resources and Interfaces Between Contexts
The FWSM allows you to share an interface between contexts. Typically in routed mode, you share the
outside interface to conserve VLANs. You can also share inside VLANs to share resources between
contexts, or you can place the shared resource on a single context and provide access to that resource to
other contexts.
This section includes the following topics:
•
Sharing Resources, page 5-6
•
Shared Interface Limitations, page 5-7
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Sharing Resources
If you have a server that needs to be accessed by multiple contexts (such as a AAA server or a syslog
server), then you can choose to place the server on one context network to which all other contexts have
access, or you can place the server on a shared inside VLAN.
If you put the server on one context network, allow access to the server by authorized users. The benefit
of placing the shared resources on one context is that you only need to configure that one context for the
shared resources network. The downside is that you must allow outside access to the shared network for
the other contexts. Also, because traffic must go out of one context and then back in another, the FWSM
has a slightly greater load than if the traffic stays within a context. (See Figure 5-4.)
Figure 5-4
Shared Resources on One Context
Internet
Switch
VLAN 200
Admin
Context
Context A
VLAN 201
VLAN 202
Inside
Customer A
Admin
Network
Context B
VLAN 203
Inside
Customer B
Context C
VLAN 204
Inside
Customer C
VLAN 300
104664
Shared
Network
Syslog Server
AAA Server
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Alternatively, you can share a VLAN on the inside of each context and place the shared resources on a
DMZ, labeled “VLAN 300” in Figure 5-5. The downside of placing the shared network inside each
context is that you must configure the interface for all contexts; however, this task can be simplified by
cutting and pasting between context configurations, and changing only the interface IP address. You also
need to make sure that traffic cannot go from one context to another, using the shared network as an
interim hop. For example, you could disallow any traffic from originating on the shared network. If you
need to originate traffic on the shared interface, for example, to access the Internet, then refer to the
“Shared Interface Limitations” section.
Figure 5-5
Shared Resources on a Shared DMZ
Internet
Switch
VLAN 200
Admin
Context
Context A
Context B
Context C
VLAN 201
VLAN 202
VLAN 203
VLAN 204
Admin
Network
Inside
Customer A
Inside
Customer B
Inside
Customer C
VLAN 300
VLAN 300
Shared
Network
VLAN 300
104663
VLAN 300
Syslog Server
AAA Server
Shared Interface Limitations
For traffic originating on a shared interface, you must configure a static NAT statement for the
destination address within a context. This requirement is valid for accessing both higher security
interfaces (outside to inside, where a static NAT translation is already required) as well as lower security
interfaces (inside to outside), such as connecting to the Internet. This requirement exists because the
FWSM classifier must use a unique IP address to determine to which context to send traffic (when you
use a shared VLAN, the classifier cannot use the VLAN to classify traffic). However, the FWSM
classifier only “knows” about context addresses from already existing NAT translations (returning
traffic) and from static NAT translations.
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Note
You cannot initiate connections from a shared interface when you use NAT exemption for the destination
address. The classifier only looks at static statements where the global interface matches the source
interface of the packet. Because NAT exemption does not identify a global interface, the classifier does
not consider those NAT statements for classification purposes.
For example, if you send a packet from a host on an inside shared VLAN to www.cisco.com, the FWSM
does not know to which context to send the packet unless you statically translate the www.cisco.com
IP address in one of the contexts. Figure 5-6 shows two servers on a shared VLAN. One server sends the
packet to the translated address, and the FWSM classifies the packet to go through Context C, which
includes a static translation for the address. The other server sends the packet to the real untranslated
address, and the packet is dropped because the FWSM cannot classify it. If you intend to statically
translate addresses for servers like www.cisco.com, then you also need to consider DNS entry addresses
and how NAT affects them. For example, if a server sends a packet to www.cisco.com, then the DNS
server needs to return the translated address. Managing DNS entries for translated addresses depends on
where the DNS server resides. See the “DNS and NAT” section on page 9-13 for more information.
Figure 5-6
Originating Traffic on a Shared VLAN
www.cisco.com
209.165.201.4
HTTP Packet
Dest. Address:
209.165.201.4
Internet
VLAN 200
Admin
Context
Context A
Context B
Context C
Static Translation
10.1.2.27
209.165.201.4
VLAN 300
VLAN 300
Shared
Network
HTTP Packet
Dest. Address:
209.165.201.4
HTTP Packet
Dest. Address:
10.1.2.27
Syslog Server
104690
VLAN 300
VLAN 300
AAA Server
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Because of the limitation for originating traffic on a shared VLAN, a scenario where you place one
context behind another is not practical because you would have to configure static statements in the top
context for every single outside address that users connected to the bottom context want to access. (See
Figure 5-7.)
Figure 5-7
Cascading Context Limitations
www.cisco.com
209.165.201.4
Internet
Gateway
Context
Shared VLAN 200
Classifier does not know whether
to send packet to Admin context or
Gateway context.
IP Address Classifier
Admin
Context
Context A
Inside
VLAN 301
Inside
HTTP Packet
Dest. Address:
209.165.201.4
104640
VLAN 300
Host
Logging into the FWSM in Multiple Context Mode
When you session into the FWSM, you access the system execution space. If you later configure Telnet
or SSH access to a context, you can log into a specific context. If you log into a specific context, you can
only access the configuration for that context. However, if you log into the admin context or session into
the system execution space, you can access all contexts.
When you change to a context from admin, you continue to use the username and command
authorization settings set in the admin context.
The system execution space does not support any AAA commands, but you can configure its own login
and enable passwords, as well as usernames in the local database to provide individual logins.
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Enabling or Disabling Multiple Context Mode
Enabling or Disabling Multiple Context Mode
Your FWSM 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. To view the mode, enter show mode.
The default software license lets you create and use two contexts in addition to the admin context. For
more contexts (up to 100), purchase a license from Cisco Systems.
This section includes:
•
Backing Up the Single Mode Configuration, page 5-10
•
Entering an Activation Key for Multiple Security Contexts, page 5-10
•
Enabling Multiple Context Mode, page 5-11
•
Restoring Single Context Mode, page 5-11
Backing Up the Single Mode Configuration
When you convert from single mode to multiple mode, the FWSM converts the running configuration
into two files: a new startup configuration (in Flash) that comprises the system configuration, and
admin.cfg (in the disk partition) that comprises the admin context. The original running configuration is
saved as old_running.cfg (in disk). The original startup configuration is not saved, so if it differs from
the running configuration, you should back it up before proceeding.
Entering an Activation Key for Multiple Security Contexts
The activation key to enable more than two contexts (plus the admin context) is based on your FWSM
serial number. Enter the following commands to view your serial number and to enter a key.
•
To show the serial number to give to Cisco when ordering your key, enter the following command:
FWSM> show version | include Number
Enter the pipe character (|) as part of the command.
•
To enter the activation key, enter the following command:
FWSM(config)# activation-key key
The key is a four-element hexadecimal string with one space between each element. For example, a
key in the correct form might look like the following key:
0xe02888da 0x4ba7bed6 0xf1c123ae 0xffd8624e
The leading 0x specifier is optional; all values are assumed to be hexadecimal.
If you are already in multiple context mode, enter this command in the system execution space.
Note
The activation key is not stored in your configuration file. The key is tied to the serial number
of the device.
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Configuring Resource Management
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, you will need to reenter this command
on the new device.
When you convert from single mode to multiple mode, the FWSM converts the running configuration
into two files: a new startup.cfg (in Flash) that comprises the system configuration, and admin.cfg (in
the disk partition) that comprises the admin context. The original running configuration is saved as
old_running.cfg (in disk). The original startup configuration is not saved. The FWSM automatically
adds an entry for the admin context to the system configuration with the name “admin.”
To enable multiple mode, enter the following command:
FWSM(config)# mode multiple
You are prompted to reboot the FWSM.
Restoring Single Context Mode
If you convert from multiple mode to single mode, the startup configuration is not automatically
converted back to the original running configuration. You must copy the backup version of the original
running configuration to the current startup configuration. (If you do not have the original configuration,
you can start over at the command line.) Because the system configuration does not have any network
interfaces as part of its configuration, you must session into the FWSM from the switch to perform the
copy (see the “Sessioning and Logging into the Firewall Services Module” section on page 3-1).
To copy the old running configuration to the startup configuration and to change the mode to single
mode, enter these commands 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:
FWSM(config)# copy disk:old_running.cfg startup-config
Step 2
To set the mode to single mode, enter the following command in the system execution space:
FWSM(config)# mode single
The FWSM reboots.
Configuring Resource Management
By default, all security contexts have unlimited access to the resources of the FWSM, 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.
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Note
The FWSM does not limit the bandwidth per context; however, the switch containing the FWSM can
limit bandwidth per VLAN. See the switch documentation for more information.
This section includes the following topics:
•
Classes and Class Members Overview, page 5-12
•
Configuring a Class, page 5-14
Classes and Class Members Overview
The FWSM 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 5-12
•
Default Class, page 5-13
•
Class Members, page 5-14
Resource Limits
When you create a class, the FWSM does not set aside a portion of the resources for each context
assigned to the class; rather, the FWSM 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 all resources together as a percentage of the total available for the device. Also,
you can set the limit for individual resources as a percentage or as an absolute value.
You can oversubscribe the FWSM by assigning more than 100 percent of the resources 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 5-8.)
Figure 5-8
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)
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The FWSM 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. For example, Context A, B, and C are in the Silver Class, which limits each class member
to 1 percent of the system inspections per second, for a total of 3 percent; but the three contexts are
currently only using 2 percent combined. Gold Class has unlimited access to inspections. The contexts
in Gold Class can use more than the 97 percent of “unassigned” inspections; they can also use the
1 percent of inspections 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 5-9.) Setting unlimited access
is similar to oversubscribing the FWSM, except that you have less control over how much you
oversubscribe the system.
Figure 5-9
Unlimited Resources
Total Number of Fixups per Second = 10,000
50% 43%
5%
(100)
4%
(100)
3%
(100)
2%
(100)
1%
(100)
Maximum connections
allowed.
Connections in use.
A
B
C
Contexts Silver Class
1
2
3
Contexts Gold Class
104896
Connections denied
because system limit
was reached.
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 2 percent 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 5-10 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 5-10 Resource Classes
Class
Bronze
(Some
Limits
Set)
Context A
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 add or change a class in the system configuration, follow these steps. After you add the class, you can
add more limits as required by following this procedure again for the same class name and specifying
additional limits. You do not need to reenter existing resource commands; the commands you already set
remain in place unless you remove them with the no form of the command. You can change the value of
a particular resource limit by reentering the command with a new value.
To configure a resource class, follow these steps:
Step 1
To specify the class name and enter the class configuration mode, enter the following command in the
system execution space:
FWSM(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.
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Step 2
To set the resource limits, see the following options:
•
To set all resource limits (shown in Table 5-1), enter the following command:
FWSM(config-resmgmt)# limit-resource all {number% | 0}
The number is an integer greater than or equal to 1. 0 (without a percent sign (%)) sets the resources
to unlimited. You can assign more than 100 percent if you want to oversubscribe the device.
•
To set a particular resource limit, enter the following command:
FWSM(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. See Table 5-1 for resources for which you can set the rate
per second.
Table 5-1 lists the resource types and the limits. See also the show resource types command.
Table 5-1
Resource Names and Limits
Resource Name
Minimum and Maximum
Number per Context
Total Number for System
mac-addresses
N/A
65 K concurrent
conns
N/A
999,900 concurrent
Description
For transparent firewall mode, the number of
MAC addresses allowed in the MAC address
table.
TCP or UDP connections between any two
hosts, including connections between one host
102,400 per second (rate)
and multiple other hosts.
Note
For concurrent connections, the FWSM
allocates half of the limit to each of two
network processors (NPs) that accept
connections. Typically, the connections
are divided evenly between the NPs.
However, in some circumstances, the
connections are not evenly divided, and
you might reach the maximum
connection limit on one NP before
reaching the maximum on the other. In
this case, the maximum connections
allowed is less than the limit you set.
The NP distribution is controlled by the
switch based on an algorithm. You can
adjust this algorithm on the switch (see
the “Customizing the FWSM Internal
Interface” section on page 2-11), or you
can adjust the connection limit upward
to account for the inequity.
fixups
N/A
10,000 per second (rate)
Application inspection.
hosts
N/A
256 K concurrent
Hosts that can connect through the FWSM.
ipsec
1 minimum
10 concurrent
IPSec sessions
5 maximum concurrent
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Table 5-1
Resource Names and Limits (continued)
Resource Name
Minimum and Maximum
Number per Context
Total Number for System
Description
pdm
1 minimum
PDM management sessions.
32 concurrent
5 maximum concurrent
ssh
1 minimum
Note
PDM 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 PDM
sessions represents a limit of 64 HTTPS
sessions.
100 concurrent
SSH sessions.
30,000 per second (rate)
System messages.
5 maximum concurrent
syslogs
N/A
Note
telnet
1 minimum
The FWSM can support 30,000
messages per second for messages sent
to the FWSM terminal or buffer. If you
send messages to a syslog server, the
FWSM supports 25,000 per second.
100 concurrent
Telnet sessions.
256 K concurrent
NAT translations.
5 maximum concurrent
xlates
N/A
For example, to set the default class limit for conns to 10 percent instead of unlimited, enter the
following commands:
FWSM(config)# class default
FWSM(config-class)# limit-resource conns 10%
All other resources remain at unlimited.
To add a class called gold with all resources set to 5 percent, except for fixups, with a setting of
10 percent, enter the following commands:
FWSM(config)# class gold
FWSM(config-class)# limit-resource all 5%
FWSM(config-class)# limit-resource fixups 10%
To add a class called silver with all resources set to 3 percent, except for syslogs, with a setting of 500
per second, enter the following commands:
FWSM(config)# class silver
FWSM(config-class)# limit-resource all 3%
FWSM(config-class)# limit-resource rate syslogs 500
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ACL Memory Partitions Overview
With ACL memory partitions, you can maximize the available ACL memory in the network processor
when you create security contexts. The default ACL memory is divided into 12 partitions and an
additional backup partition. In addition to these partitions, there is one partition and a backup partition
for downloadable ACLs. The default behavior is that when you create a security context, it is associated
with an ACL partition chosen in a round-robin fashion. All of the access lists created in the context get
programmed into the associated partition. This behavior results in an inefficient allocation of available
ACL memory. The default ACL memory allocation scheme results in the following inefficiencies:
•
Fewer contexts than the default number of partitions
– When you have fewer contexts than partitions, some partitions are never used. The result is that
there is less usable memory than available memory.
•
More contexts than the default number of partitions
– If the number of contexts is more than the number of partitions, configuration changes made by
one user can impact other users because they share the resource.
•
No guaranteed resources for business class customers
– All users or customers were treated equally with no way to prioritize them.
Configuring ACL Memory Partitions
Beginning with FWSM software release 2.3, you can configure the number of partitions to maximize
ACL memory usage. This feature allows you to eliminate the inefficiencies of the default ACL memory
allocation scheme.
There are two parts to configuring ACL memory partitions: partitioning the ACL memory using the
resource acl-partition command and mapping a context to a partition using the allocate-acl-partition
command.
To partition the ACL memory, enter this command:
fwsm(config)# resource acl-partition number-of-partitions
The no form of this command will cause ACL memory to be partitioned into the default number of
partitions (12).
The following caveats apply to this command:
•
You must reboot the module before the changes will take place. In a failover set up, you must reboot
both of the modules at the same time. Rebooting both modules at the same time will result in
network downtime.
•
The resource acl-partition <X> command will not take effect until you enter a write mem
command and reboot the module.
•
If you are using a failover configuration, you must use these recommended command sequences:
On the active module, use this sequence:
resource acl-partition X
write mem
reload
On the redundant module, use this sequence: reload
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Note
You must reload both the active and redundant modules at the same time.
•
Note
The resource acl-partition command is available in multiple mode only, not in single mode.
The active module and redundant module must be rebooted together. Traffic loss occurs because both
the active and the redundant modules are down at the same time.
•
The maximum number of rules of each type is a function of number of partitions.
For example, when the number of partitions is 12, the following apply:
Max Filter rules–606
Max Established rules–121
Max AAA rules–1213
Max ACL rules–9704
Max Console Access rules–363
Max PolicyNAT rules–606
To map a context to a specific partition, enter the following command in multiple mode:
allocate-acl-partition partition-number
Use the no form of the command to remove the mapping.
This example shows how to allocate contexts and ACL partitions.
This example shows how ACL partition #0 is shared by contexts “bandn” and “borders” while the
remaining contexts share ACL paritition number 1. The following sample shows how to partition ACL
memory into two partitions:
FWSM(config)# resource acl-partition 2
FWSM(config)# context bandn
FWSM(config-context)# allocate-acl-partition 0
FWSM(config)# context borders
FWSM(config-context)# allocate-acl-partition 0
FWSM(config)# context mompopa
FWSM(config)# context mompopb
FWSM(config)# context mompopc
FWSM(config)# context mompopd
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This example shows how to verify the current mapping of contexts to ACL partitions.
FWSM(config)# show resource acl-partition
Total number of configured partitions = 2
Partition #0
Mode
:exclusive
List of Contexts
:bandn, borders
Number of contexts
:2(RefCount:2)
Number of rules
:0(Max:53087)
Partition #1
Mode
:non-exclusive
List of Contexts
:admin, momandpopA, momandpopB, momandpopC
momandpopD
Number of contexts
:5(RefCount:5)
Number of rules
:6(Max:53087)
Configuring a Security Context
The security context definition in the system configuration identifies the context name, configuration
file URL, VLANs that a context can use, and the resource class to which a context belongs. After you
add the context, you can add more VLAN interfaces as required by following this procedure again and
specifying additional interfaces. You do not need to reenter other context commands again; the
commands you already set remain in place unless you remove them with the no form of the command.
You can change the value of single-instance commands by reentering the command with a new value.
For commands that you can enter multiple times, such as the allocate-interface command, you must
remove the command with the no form and then re-add the altered version.
Note
Before you configure the first context, configure the ACL partition. See the “ACL Memory Partitions
Overview” section on page 5-17.
Note
If you do not have an admin context (for example, if you clear the configuration), then the first context
you add must be the admin context. Before continuing with this procedure to add a context, enter the
following command:
FWSM(config)# admin-context name
You can now enter the context name command to match the name you specified for the admin context.
To add or change a context in the system configuration, follow these steps:
Step 1
To add or modify a context, enter the following command in the system execution space:
FWSM(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.
We recommend you do not use the names “count” or “detail.” These names are options in the
show context command, so you cannot use the show context command to show information about a
context called “count” or “detail.” “system” is a reserved name, and cannot be used.
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Step 2
(Optional) To add a description for this context, enter the following command:
FWSM(config-context)# description text
Step 3
To specify the VLAN interfaces you can use in the context, enter the following command:
FWSM(config-context)# allocate-interface vlannumber[-vlannumber] [map_name[-map_name]]
You can enter this command multiple times to specify different ranges. For transparent firewall mode,
you can only use two interfaces per context.
Enter a VLAN number or a range of VLANs, typically from 1 to 1000 and from 1025 to 4094 (see the
switch documentation for supported VLANs). You can assign the same VLANs to multiple contexts, if
desired. See the “Sharing Resources and Interfaces Between Contexts” section on page 5-5 for more
information about shared VLAN limitations.
The map_name is an alphanumeric alias for the VLAN interface that can be used within the context
instead of the VLAN number. If you do not specify a mapped name, the VLAN number is used within
the context. For security purposes, you might not want the context administrator to know which VLANs
are being used by the context. Instead of using the VLAN number in the nameif command, for example,
you can use the mapped name.
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
If you specify a range of VLAN IDs, 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
•
The numeric portion of the mapped name must include the same quantity of numbers as the
vlanx-vlany statement. For example, both ranges include 100 interfaces:
vlan100-vlan199 int1-int100
If you enter vlan100-vlan199 int1-int15 or vlan100-vlan199 happy1-sad5, for example, the
command fails.
The following example shows VLANs 100, 200, and 300 through 305 assigned to the context. The
mapped names are int1 through int8.
FWSM(config-context)# allocate-interface vlan100 int1
FWSM(config-context)# allocate-interface vlan200 int2
FWSM(config-context)# allocate-interface vlan300-vlan305 int3-int8
Step 4
To identify the URL from which the system downloads the context configuration, enter the following
command:
FWSM(config-context)# config-url url
When you add a context URL, the system immediately loads the context so that it is running.
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Note
Enter the allocate-interface command(s) before you enter the config-url command. The FWSM must
assign VLAN interfaces to the context before it loads the context configuration; the context
configuration might include commands that refer to interfaces (nameif, nat, global...). If you enter the
config-url command first, the FWSM 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
•
ftp://[user[:password]@]server/[path/]filename
•
tftp://server/[path/]filename
•
http://server/[path/]filename
•
https://server/[path/]filename
The FWSM can download a context from a TFTP or FTP server, HTTP or HTTPS server, or from the
local disk (called disk). The disk is a 64-MB partition of Flash that uses a navigable file system. The
disk partition is used only for context storage. The system configuration and the software image reside
in the Flash partition (called flash).
The server must be accessible from the admin context. The admin context file must be stored on the disk.
The filename does not require a file extension, although we recommend using “.cfg”.
If the system cannot retrieve the context configuration file because the server is unavailable, or the file
does not yet exist, the system creates a blank context that is ready for you to configure with the
command-line interface.
For example, enter the following command:
FWSM(config-context)# config-url ftp://joe:[email protected]/configlets/test.cfg
Step 5
(Optional) To assign the context to a resource class, enter the following command:
FWSM(config-context)# 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:
FWSM(config-context)# member gold
See the following sample context configurations:
FWSM(config)# context
FWSM(config-context)#
FWSM(config-context)#
FWSM(config-context)#
FWSM(config-context)#
FWSM(config-context)#
FWSM(config-context)#
FWSM(config-context)#
FWSM(config-context)#
FWSM(config-context)#
FWSM(config-context)#
FWSM(config-context)#
FWSM(config-context)#
FWSM(config-context)#
administrator
allocate-interface vlan10
allocate-interface vlan11
config-url disk://admin.cfg
context test
allocate-interface vlan100 int1
allocate-interface vlan200 int2
allocate-interface vlan300-vlan305 int3-int8
config-url ftp://joe:[email protected]/configlets/test.cfg
member gold
context sample
allocate-interface vlan101 int1
allocate-interface vlan201 int2
allocate-interface vlan306-vlan311 int3-int8
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FWSM(config-context)# config-url ftp://joe:[email protected]/configlets/sample.cfg
FWSM(config-context)# member silver
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.
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.
See the following commands for removing contexts:
•
To remove a single context, enter the following command in the system execution space:
FWSM(config)# no context name
All context subcommands are also removed.
•
To remove all contexts (including the admin context), enter the following command in the system
execution space:
FWSM(config)# clear context
Changing the Admin Context
You can set any context to be the admin context.
To set the admin context, enter the following command in the system execution space:
FWSM(config)# admin-context context_name
Changing Between Contexts and the System Execution Space
If you log into the system execution space or the admin context, you can change between contexts and
perform configuration and monitoring tasks within each context. The “running” configuration that you
edit in configuration mode, or that is used in the copy or write commands, 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.
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Changing the Security Context URL
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:
FWSM# changeto context name
The prompt changes to the following:
FWSM/name#
•
To change to the system execution space, enter the following command:
FWSM/admin# changeto system
The prompt changes to the following:
FWSM#
Changing the Security Context URL
You cannot change the security context URL without reloading the configuration from the new URL.
When you reload the configuration, the new configuration merges with the one in running memory. 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, follow these 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.
FWSM# changeto context name
FWSM/name# configuration terminal
FWSM/name(config)# clear config all
Step 2
If required, change to the system execution space by entering the following command:
FWSM/name(config)# changeto system
Step 3
To enter the context configuration mode for the context you want to change, enter the following
command:
FWSM(config)# context name
Step 4
To enter the new URL, enter the following command:
FWSM(config)# config-url new_url
The system immediately loads the context so that it is running.
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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,
VLANs, and class membership.
This section includes the following topics:
•
Reloading by Clearing the Configuration, page 5-24
•
Reloading by Removing and Re-adding the Context, page 5-24
Reloading by Clearing the Configuration
To reload the context by clearing the context configuration, and reloading the configuration from the
URL, follow these steps:
Step 1
To change to the context that you want to reload, enter the following command:
FWSM# changeto context name
Step 2
To access configuration mode, enter the following command:
FWSM/name# configuration terminal
Step 3
To clear the running configuration, enter the following command:
FWSM/name(config)# clear configure all
This command stops the context from running.
Step 4
To reload the configuration, enter the following command:
FWSM/name(config)# copy startup-config running-config
The FWSM copies the configuration from the URL specified in the system configuration. You cannot
change the URL from within a context.
Reloading by Removing and Re-adding the Context
To reload the context by removing the context and then re-adding it, follow the steps in the following
sections:
1.
“Removing a Security Context” section on page 5-22
2.
“Configuring a Security Context” section on page 5-19
Monitoring Security Contexts
This section describes how to view and monitor context information, and includes the following topics:
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•
Viewing Context Information, page 5-25
•
Viewing Resource Allocation, page 5-26
•
Viewing Resource Usage, page 5-28
Viewing Context Information
From the system execution space, you can view a list of contexts including the name, class, interfaces,
and configuration file URL.
From the system execution space, view all contexts by entering the following command:
FWSM# show context [name [detail]| count]
The detail option shows additional information. See the 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 sample display shows three contexts:
FWSM# show context
Context Name
Class
*admin
default
contexta
gold
contextb
silver
Interfaces
Vlan10,22,55-57
vlan10,100-101
vlan10,110-111
URL
disk:/admin.cfg
disk:/contexta.cfg
disk:/contextb.cfg
Total active Security Contexts: 3
Table 5-2 shows each field description.
Table 5-2
show context Fields
Field
Description
Context Name
Lists all context names. The context name with the asterisk (*) is the admin context.
Class
The class to which the context belongs.
Interfaces
The VLAN interfaces assigned to the context.
URL
The URL from which the FWSM loads the context configuration.
The following sample display shows the detail option:
FWSM# show context detail
Context "admin", is ADMIN and active
Config URL: disk:/admin.cfg
Interfaces: Vlan10,22,55-57
Class: default, Flags: 0x00000057, ID: 1
Context "contexta", is active
Config URL: disk:/contexta.cfg
Interfaces: vlan10,100-101
Class: default, Flags: 0x00000055, ID: 2
The “Flags” and “ID” fields are for internal use only.
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Viewing Resource Allocation
From the system execution space, you can view the allocation for each resource across all classes and
class members.
From the system execution space, view the resource allocation by entering the following command:
FWSM# 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 5-28 for more information about actual resource usage.
The detail argument shows additional information. See the sample displays below 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:
FWSM# show resource allocation
Resource
Total
Conns [rate]
35000
Fixups [rate]
35000
Syslogs [rate]
10500
Conns
305000
Hosts
78842
IPsec
7
SSH
35
Telnet
35
Xlates
91749
All
unlimited
% of Avail
35.00%
35.00%
35.00%
30.50%
30.07%
35.00%
35.00%
35.00%
34.99%
Table 5-3 shows each field description.
Table 5-3
show resource allocation Fields
Field
Description
Resource
The name of the resource that you can limit.
See the “Configuring a Class” section on page 5-14 for more information about
each resource name.
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 FWSM 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.
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The following sample display shows the detail option:
FWSM# 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
Fixups [rate]
Syslogs [rate]
Conns
Hosts
IPSec
SSH
Telnet
Xlates
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
silver
bronze
All Contexts:
all
1
1
0
3
C
D
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
C
D
CA
CA
default
gold
silver
bronze
All Contexts:
all
1
1
0
3
CA
DA
CA
CA
unlimited
unlimited
10000
5000
unlimited
6000
3000
1500
unlimited
200000
100000
50000
unlimited
unlimited
26214
13107
5
5
1
unlimited
5
5
10
5
5
5
10
5
unlimited
unlimited
23040
11520
Total
Total %
34000
17000
20.00%
10.00%
51000
30.00%
10000
10.00%
10000
10.00%
6000
3000
20.00%
10.00%
9000
30.00%
200000
100000
20.00%
10.00%
300000
30.00%
26214
9.99%
26214
9.99%
5
1
50.00%
10.00%
11
110.00%
5
10
5.00%
10.00%
20
20.00%
5
10
5.00%
10.00%
20
20.00%
23040
10.00%
23040
10.00%
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mac-addresses
default
gold
silver
bronze
All Contexts:
all
1
1
0
3
C
D
CA
CA
65535
65535
6553
3276
65535
6553
100.00%
9.99%
137623
209.99%
Table 5-4 shows each field description.
Table 5-4
show resource allocation detail Fields
Field
Description
Resource
The name of the resource that you can limit.
See the “Configuring a Class” section on page 5-14 for more information about
each resource name.
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 FWSM 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 FWSM 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.
Viewing Resource Usage
From the system execution space, you can view the resource usage.
From the system execution space, view the resource usage for each context by entering the following
command:
FWSM# show resource usage [context context_name | top n | all | summary | system]
[resource {[rate] resource_name | all} | detail] [counter counter_name [count_threshold]]
all is the default, and shows resource usage for each context individually.
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.
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The summary option shows the total for all contexts together. For example, the denied column shows
the items that have been denied for each context limit. The system option shows the counts for the entire
system. For the limit and denied counts, for example, you only see a number in the denied column if the
system limit is reached, not if one or more context limits are reached.
For the resource name, see Table 5-1 on page 5-15 for resource names.
The detail keyword shows the resources you can limit in a class, plus other system resources for which
you cannot configure limits.
The counter counter_name is one of the following keywords:
•
current—Shows the active concurrent instances or the current rate of the resource.
•
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.
•
denied—Shows the number of denied uses of the resource, since the resource statistics were last
cleared.
•
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 sample display shows the resource usage for all contexts and all resources.
FWSM# show resource usage summary
Resource
Current
Peak
Limit
Denied Context
Syslogs [rate]
1743
2132
12000(U)
0 Summary
Conns
584
763
100000(S)
0 Summary
Xlates
8526
8966
93400
0 Summary
Hosts
254
254
262144
0 Summary
Conns [rate]
270
535
42200
1704 Summary
Fixups [rate]
270
535
100000(S)
0 Summary
U = Some contexts are unlimited and are not included in the total.
S = All contexts are unlimited; system limit is shown.
Monitoring 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 addresess. The constant
flood of SYN packets keeps the server’s SYN queue full which prevents it from servicing connection
requests. When the embryonic connection threshold of a connection is crossed, the FWSM acts as a
proxy for the server and generates a SYN-ACK response to the client’s SYN request. When the FWSM
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.
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Note
Beginning with Release 2.3, using the show local host command is not a reliable method for monitoring
the rate of SYN attacks.
The following sample display shows the rate of TCP intercepts for a context called admin.
FWSM/admin# show perfmon
Context:admin
PERFMON STATS:
Xlates
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
Current
0/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
Average
0/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 sample display shows the amount of resources being used by TCP intercept for individual
contexts. (Sample text in italics shows the TCP intercept information.)
FWSM(config)# show resource usage detail
Resource
Current
Peak
memory
843732
847288
chunk:channels
14
15
chunk:fixup
15
15
chunk:hole
1
1
chunk:ip-users
10
10
chunk:list-elem
21
21
chunk:list-hdr
3
4
chunk:route
2
2
chunk:static
1
1
tcp-intercept-rate
328787
803610
np-statics
3
3
statics
1
1
ace-rules
1
1
console-access-rul
2
2
fixup-rules
14
15
memory
959872
960000
chunk:channels
15
16
chunk:dbgtrace
1
1
chunk:fixup
15
15
chunk:global
1
1
chunk:hole
2
2
chunk:ip-users
10
10
chunk:udp-ctrl-blk
1
1
chunk:list-elem
24
24
chunk:list-hdr
5
6
chunk:nat
1
1
chunk:route
2
2
chunk:static
1
1
tcp-intercept-rate
16056
16254
globals
1
1
np-statics
3
3
statics
1
1
Limit
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
N/A
N/A
N/A
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
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
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
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nats
ace-rules
console-access-rul
fixup-rules
memory
chunk:channels
chunk:dbgtrace
chunk:fixup
chunk:ip-users
chunk:list-elem
chunk:list-hdr
chunk:route
block:16384
block:2048
1
2
2
14
232695716
17
3
15
4
1014
1
1
510
32
1
2
2
15
232020648
20
3
15
4
1014
1
1
885
34
unlimited
N/A
N/A
N/A
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
0
0
0
0
0
0
0
0
0
0
0
0
0
0
c1
c1
c1
c1
system
system
system
system
system
system
system
system
system
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.)
FWSM(config)# show resource usage summary detail
Resource
Current
Peak
Limit
Denied Context
memory
238421312
238434336 unlimited
0 Summary
chunk:channels
46
48 unlimited
0 Summary
chunk:dbgtrace
4
4 unlimited
0 Summary
chunk:fixup
45
45 unlimited
0 Summary
chunk:global
1
1 unlimited
0 Summary
chunk:hole
3
3 unlimited
0 Summary
chunk:ip-users
24
24 unlimited
0 Summary
chunk:udp-ctrl-blk
1
1 unlimited
0 Summary
chunk:list-elem
1059
1059 unlimited
0 Summary
chunk:list-hdr
10
11 unlimited
0 Summary
chunk:nat
1
1 unlimited
0 Summary
chunk:route
5
5 unlimited
0 Summary
chunk:static
2
2 unlimited
0 Summary
block:16384
510
885
8192(S)
0 Summary
block:2048
32
35
1000(S)
0 Summary
tcp-intercept-rate
341306
811579 unlimited
0 Summary
globals
1
1
1051(S)
0 Summary
np-statics
6
6
4096(S)
0 Summary
statics
2
2
2048(S)
0 Summary
nats
1
1
2048(S)
0 Summary
ace-rules
3
3
116448(S)
0 Summary
console-access-rul
4
4
4356(S)
0 Summary
fixup-rules
43
44
8032(S)
0 Summary
S = System:Total exceeds the system limit; the system limit is shown
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C H A P T E R
6
Configuring Basic Settings
This chapter tells how to configure basic settings on your Firewall Services Module (FWSM). This
chapter includes the following sections:
•
Changing the Passwords, page 6-1
•
Setting the Host Name, page 6-4
•
Setting the Domain Name, page 6-5
•
Adding a Login Banner, page 6-5
•
Configuring Interfaces, page 6-6
•
Configuring Connection Limits for Non-NAT Configurations, page 6-10
Changing the Passwords
This section tells how to change the login password and enable password from their default settings, as
well as how to change the maintenance partition passwords. The maintenance partition is used for
troubleshooting, recovering from a corrupted image, or recovering lost passwords. See the following
topics:
Note
•
Changing the Login Password, page 6-2
•
Changing the Enable Password, page 6-2
•
Changing the Maintenance Partition Passwords, page 6-2
In multiple context mode, every context and the system execution space has its own login policies and
passwords.
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Configuring Basic Settings
Changing the Passwords
Changing the Login Password
By default, the login password is “cisco.”
To change the password, enter the following command in privileged mode:
FWSM/contexta(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 clear password command to restore the password to the default setting.
Changing the Enable Password
By default, the enable password is blank.
To change enable the password, enter the following command in privileged mode:
FWSM/contexta(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. (See the “Configuring
Command Authorization” section on page 12-10 for more information.)
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.
Changing the Maintenance Partition Passwords
The maintenance partition is valuable for troubleshooting. For example, you can install new software to
an application partition, reset passwords, or show crash dump information from the maintenance
partition. You can only access the maintenance partition by sessioning into the FWSM. (See the
“Sessioning and Logging into the Firewall Services Module” section on page 3-1.)
The maintenance partition has two user levels with different access privileges:
•
root—Lets you configure the network partition parameters, upgrade the software images on the
application partitions, change the guest account password, and enable or disable the guest account.
The default password is “cisco.”
•
guest—Lets you configure the network partition parameters and show crash dump information.
The default password is “cisco.”
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Changing the Passwords
To change the maintenance partition passwords for both users, follow these steps:
Step 1
To reboot the FWSM into the maintenance partition, enter the command for your operating system:
•
Cisco IOS software:
Router# hw-module module mod_num reset cf:1
•
Catalyst operating system software:
Console> (enable) reset mod_num boot cf:1
Step 2
To session into the FWSM, enter the command for your operating system:
•
Cisco IOS software:
Router# session slot mod_num processor 1
•
Catalyst operating system software:
Console> (enable) session mod_num
Step 3
Log in as root by entering the following command:
Login: root
Step 4
Enter the password at the prompt:
Password:
The default password is “cisco”.
Step 5
Change the root password by entering the following command:
[email protected]# passwd
Step 6
Enter the new password at the prompt:
Changing password for user root
New password:
Step 7
Enter the new password again:
Retype new password:
passwd: all authentication tokens updated successfully
Step 8
Change the guest password by entering the following command:
[email protected]# passwd-guest
Step 9
Enter the new password at the prompt:
Changing password for user guest
New password:
Step 10
Enter the new password again:
Retype new password:
passwd: all authentication tokens updated successfully
This example shows how to set the password for the root account:
[email protected]# passwd
Changing password for user root
New password: *sh1p
Retype new password: *sh1p
passwd: all authentication tokens updated successfully
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Configuring Basic Settings
Setting the Host Name
This example shows how to set the password for the guest account:
[email protected]# passwd-guest
Changing password for user guest
New password: f1rc8t
Retype new password: f1rc8t
passwd: all authentication tokens updated successfully
Setting the Host Name
When you set a host name for the FWSM, that name appears in the command line prompt. If you
establish sessions to multiple devices, the host name helps you keep track of where you enter commands.
By default, the host name is “FWSM”.
For multiple context mode, the host name that you set in the system execution space appears in the
command line prompt for all contexts.
The host name that you optionally set within a context does not appear in the command line, but is used
for RSA key generation. If you do not set a host name within a context, the context name is used as the
host name in the certificate. RSA keys are required for SSH, the HTTPS server, and can be used for VPN.
You should also set the domain name for RSA key generation (see “Setting the Domain Name”). If you
change the host name after you generate keys, you need to regenerate the keys using the ca generate rsa
key command.
To specify the host name for the FWSM or for a context, enter the following command:
FWSM(config)# hostname name
This name can be up to 63 characters, including alphanumeric characters, spaces or any of the following
special characters: ` ( ) + - , . / : = ?.
In single mode and in the system execution space in multiple mode, this name appears in the command
line prompt. For example:
FWSM(config)# hostname farscape
farscape(config)#
For a context, this name is used for RSA key generation. If you do not set a host name within a context,
the context name is used for the host name in the key. You can view a context host name using the show
hostname command.
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Setting the Domain Name
Setting the Domain Name
The domain name is used for RSA key generation. RSA keys are required for SSH, the HTTPS server,
and can be used for VPN. You should also set the host name for key generation (see “Setting the Host
Name”). If you change the domain name after generating keys, you need to regenerate the keys using
the ca generate rsa key command.
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 FWSM, enter the following command:
FWSM/contexta(config)# domain-name name
For example, to set the domain as cisco.com, enter the following command:
FWSM(config)# domain-name cisco.com
Adding a Login Banner
You can configure a message to display when a user connects to the FWSM, before a user logs in, or
before a user enters privileged mode.
To configure a login banner, enter the following command in the system execution space or within a
context:
FWSM/contexta(config)# banner {exec | login | motd} text
Adds a banner to display at one of three times: when a user first connects (message-of-the-day (motd)),
when a user logs in (login), and when a user accesses privileged mode (exec). When a user connects to
the FWSM, the message-of-the-day banner appears first, followed by the login banner and prompts.
After the user successfully logs in to the FWSM, the exec banner displays.
For the banner text, spaces are allowed but tabs cannot be entered using the CLI. You can dynamically
add the host name or domain name of the FWSM by including the strings $(hostname) and $(domain).
If you configure a banner in the system configuration, you can use that banner text within a context by
using the $(system) string in the context configuration.
To add more than one line, precede each line by the banner command.
For example, to add a message-of-the-day banner, enter:
FWSM/contexta(config)# banner motd Welcome to the $(hostname) firewall.
FWSM/contexta(config)# banner motd Contact me at [email protected] for any
FWSM/contexta(config)# banner motd issues.
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Configuring Interfaces
Configuring Interfaces
By default, all interfaces are enabled. For each interface, you must provide a name and a security level.
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 15, “Using Failover,” to configure the failover and
state links.
This section includes the following topics:
•
Security Level Overview, page 6-6
•
Setting the Name and Security Level, page 6-7
•
Allowing Communication Between Interfaces on the Same Security Level, page 6-8
•
Turning Off and Turning On Interfaces, page 6-10
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 6-8 for more information.
For interfaces that are on different security levels, the level controls the following behavior:
•
NAT—When hosts on a higher security interface (inside) access hosts on a lower security interface
(outside), you must configure Network Address Translation (NAT) for the inside hosts or
specifically configure the inside hosts to bypass NAT.
An inside host can communicate with the untranslated local address of the outside host without any
special configuration on the outside interface. However, you can also optionally perform NAT on the
outside network.
•
Inspection engines—Some inspection engines are dependent on the security level:
– SMTP inspection engine—Applied only for inbound connections (from lower level to higher
level), which protects the SMTP servers on the higher security interface.
– NetBIOS inspection engine—Applied only for outbound connections.
– XDMCP inspection engine—The XDMCP server can be configured only on the outside
interface.
– OraServ inspection engine—If a control connection for the OraServ port exists between a pair
of hosts, then only an inbound data connection is permitted through the FWSM.
•
Filtering—HTTP(S) and FTP filtering applies only for outbound connections (from a higher level
to a lower level).
•
TCP intercept—The TCP intercept feature only applies to hosts or servers on a higher security level.
See the “Other Protection Features” section on page 1-6 for more information about TCP intercept.
This feature is configured using the emb_limit option in the nat and static commands.
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•
TCP sequence randomization—Each TCP connection has two Initial Sequence Numbers (ISNs): one
generated by the client and one generated by the server. The FWSM randomizes the ISN that is
generated by the host/server on the higher security interface. At least one of the ISNs must be
randomly generated so that attackers cannot predict the next ISN and potentially hijack the session.
•
Maximum connections limit—You can set a limit on the number of TCP and UDP connections
allowed through the FWSM, but only connections from a higher security interface to a lower
security interface are tracked. This limit is set using the max_conns option in the nat and static
commands.
•
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.
These behaviors do not affect interfaces that are on the same security level. For example, you do not have
to perform NAT, nor do you have to configure the interfaces to bypass NAT. You can, however, optionally
configure NAT for these interfaces. Similarly, inspection engines are applied to both interfaces, as is
filtering.
Note
By default, the Cisco PIX firewall allows traffic to flow freely from an inside network (higher security
level) to an outside network (lower security level). However, the FWSM does not allow any traffic to
pass between interfaces unless you explicitly permit it with an access control list (ACL). While you still
have to specify the security level for an interface on the FWSM, the security level does not provide an
explicit permission for traffic to travel from a high security interface to a low security interface.
Setting the Name and Security Level
By default, all interfaces are enabled. However, you must assign a name and security level to each
interface before you can fully configure the FWSM. Many commands use the interface name instead of
the interface (VLAN) ID.
You can assign a name to a VLAN that has not yet been assigned to the FWSM (see the “Assigning
VLANs to the Firewall Services Module” section on page 2-2), but you see a warning message.
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 15, “Using Failover,” to configure the failover and
state links.
For multiple context mode, follow these guidelines:
•
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 does not include configurable interfaces, except for failover interfaces. Do
not configure failover interfaces with this procedure. See Chapter 15, “Using Failover,” for more
information.
In transparent firewall mode, you can use only two interfaces, one inside and one outside.
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Configuring Interfaces
Note
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 translation table using the clear
xlate command. However, clearing the translation table disconnects all current connections.
To name an interface, enter the following command:
FWSM/contexta(config)# nameif {vlann | context_map_name} name [security]n
For multiple context mode, if you gave the VLAN interface a mapped name for the context in the system
configuration, then you must use the mapped name.
The name is a text string up to 48 characters, and is not case-sensitive.
The security level is an integer between 0 and 100. 0 is the least secure and 100 the most secure. You
can optionally include the word security before the level number to make your configuration easier to
read. To assign more than one interface to the same level, see the “Allowing Communication Between
Interfaces on the Same Security Level” section on page 6-8 to enable this feature.
For example, enter the show nameif command to view the interface names:
FWSM# show nameif
nameif vlan100 outside security0
nameif vlan101 inside security100
nameif vlan102 dmz security50
Allowing Communication Between Interfaces on the Same Security Level
By default, interfaces on the same security level cannot communicate with each other, even if you
configure NAT and ACLs.
Allowing communication between same security interfaces provides the following benefits:
•
You do not need to configure NAT between same security interfaces.
You can, however, configure NAT if desired. If you configure dynamic NAT for an interface, then to
allow connections initiated from another interface, even if it is on the same security level, you need
to configure static NAT.
If you want to configure connection limits but do not want to configure NAT (where connection
limits are set), you can configure identity NAT or NAT exemption. (See the “Configuring
Connection Limits for Non-NAT Configurations” section on page 6-10 or the “Bypassing NAT”
section on page 9-29.)
•
You can configure more than 101 communicating interfaces.
If you use different levels for each interface, you can configure only one interface per level (0 to
100).
•
You want protection features to be applied equally for traffic between two interfaces; for example,
you have two departments that are equally secure.
For different security level interfaces, many protection features apply only in one direction, for
example, inspection engines, TCP intercept, and connection limits.
If you enable same security interface communication, you can still configure interfaces at different
security levels as usual.
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Configuring Interfaces
To enable interfaces on the same security level so that they can communicate with each other, enter the
following command:
FWSM/contexta(config)# same-security-traffic permit inter-interface
You can configure the FWSM to enable communication between two hosts on the same interface. Before
you can enable this feature, you must first correctly configure the MSFC so that packets are sent to the
FWSM MAC address instead of being sent directly through the switch to the destination host. Figure 6-1
shows a network where hosts on the same interface need to communicate. The following samples show
the route-map command used to enable policy routing in the network shown in Figure 6-1:
fwsm(config)# route-map intra-inter3 permit 0
fwsm#(config-route-map)# match ip address 103
fwsm#(config-route-map)# set interface Vlan20
fwsm#(config-route-map)# set set ip next-hop 10.6.34.7
!
fwsm(config)# route-map intra-inter2 permit 20
fwsm#(config-route-map)# match ip address 102
fwsm#(config-route-map)# set interface Vlan20
fwsm#(config-route-map)# set set ip next-hop 10.6.34.7
!
fwsm(config)# route-map intra-inter1 permit 10
fwsm#(config-route-map)# match ip address 101
fwsm#(config-route-map)# set interface Vlan20
fwsm#(config-route-map)# set set ip next-hop 10.6.34.7
Figure 6-1
Communication Between Hosts on the Same Interface
Host
IP cloud-2
Vlan60
10.6.37.0
IP cloud-1
MSFC
Vlan70
10.6.36.0
Vlan10
10.6.35.0
Host
IP cloud-3
Host
FWSM
120544
SVI, Vlan20
10.6.34.0
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Configuring Connection Limits for Non-NAT Configurations
When you enable communication between two hosts on the same interface, keep in mind the following
requirements:
•
Outside NAT is not supported.
•
You can configure static routes from one interface to another on the same security level.
To enable communication between hosts on the same security level, enter the following command:
FWSM/contexta(config)# same-security-traffic permit intra-interface
To disable these settings, add no before the command.
Turning Off and Turning On Interfaces
All interfaces are enabled by default. If you disable or reenable the interface within a context, only that
context interface is affected. But if you disable or reenable the interface in the system execution space,
then you affect that VLAN interface for all contexts.
To disable an interface or reenable it, follow these steps:
Step 1
To enter the interface configuration mode, enter the following command:
FWSM/contexta(config)# interface interface_name
Step 2
To disable the interface, enter the following command:
FWSM/contexta(config-interface)# shutdown
Step 3
To reenable the interface, enter the following command:
FWSM/contexta(config-interface)# no shutdown
Configuring Connection Limits for Non-NAT Configurations
Transparent firewall mode
Same security level mode
The NAT configuration enables you to set connection limits for traffic. For transparent firewall mode or
for same security interfaces on which you do not want to configure NAT (see the “Allowing
Communication Between Interfaces on the Same Security Level” section on page 6-8), you can
configure identity NAT to set these limits. Identity NAT lets you specify the addresses for which you
want to set limits, but no translation is performed. (For same security interfaces, you can configure any
method for bypassing NAT, including NAT exemption. See the “Bypassing NAT” section on page 9-29
for more information. For transparent mode, the FWSM supports only the following method.)
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Configuring Connection Limits for Non-NAT Configurations
To set connection limits for the inside interface (transparent mode) or for any same security interface,
enter the following command:
FWSM/contexta(config)# static (inside_interface,outside_interface) local_ip_address
local_ip_address netmask mask [norandomseq] [[tcp] tcp_max_conns [emb_limit]]
[udp udp_max_conns]
Enter the same IP address for both local_ip_address options.
Set one or more of the following options:
•
norandomseq—No TCP Initial Sequence Number (ISN) randomization. Only use this option if
another in-line firewall is also randomizing sequence numbers and the result is scrambling the data.
See the “Security Level Overview” section on page 6-6 for information about TCP sequence
numbers.
•
tcp tcp_max_conns, udp udp_max_conns—The maximum number of simultaneous TCP and/or
UDP connections for the entire subnet up to 65,536. The default is 0 for both protocols, which means
the maximum connections.
•
emb_limit—The maximum number of embryonic connections per host up to 65,536. An embryonic
connection is a connection request that has not finished the necessary handshake between source and
destination. This limit enables the TCP Intercept feature. (See the “Other Protection Features”
section on page 1-6 for more information.) The default is 0, which means the maximum embryonic
connections. You must enter the tcp tcp_max_conns before you enter the emb_limit. If you want to
use the default value for tcp_max_conns, but change the emb_limit, then enter 0 for tcp_max_conns.
For example, to set options for the host 10.1.1.1, enter the following command:
FWSM/contexta(config)# static (inside,outside) 10.1.1.1 10.1.1.1 netmask 255.255.255.255
norandomseq tcp 1000 200 udp 1000
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Configuring Connection Limits for Non-NAT Configurations
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Configuring Bridging Parameters and
ARP Inspection
Transparent firewall mode only
This chapter tells how to customize bridging operations and how to enable ARP inspection for the
transparent firewall. This chapter includes the following sections:
•
Customizing the MAC Address Table, page 7-1
•
Configuring ARP Inspection, page 7-3
Customizing the MAC Address Table
This section includes the following topics:
•
MAC Address Table Overview, page 7-1
•
Adding a Static MAC Address, page 7-2
•
Setting the MAC Address Timeout, page 7-2
•
Disabling MAC Address Learning, page 7-2
•
Viewing the MAC Address Table, page 7-3
MAC Address Table Overview
The FWSM learns and builds a MAC address table in a similar way as a normal bridge or switch: when
a device sends a packet through the FWSM, the FWSM adds the MAC address to its table. The table
associates the MAC address with the source interface so that the FWSM knows to send any packets
addressed to the device out the correct interface.
Because the FWSM is a firewall, if the destination MAC address of a packet is not in the table, the
FWSM does not flood the original packet on all interfaces as a normal bridge does. Instead, it generates
the following packets for directly connected devices or for remote devices:
•
Packets for directly connected devices—The FWSM generates an ARP request for the destination
IP address, so that the FWSM can learn which interface receives the ARP response.
•
Packets for remote devices—The FWSM generates a ping to the destination IP address so that the
FWSM can learn which interface receives the ping reply.
The original packet is dropped.
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Customizing the MAC Address Table
Note
For multiple context mode, you can limit the maximum number of mac address table entries in the
context class. See the “Configuring a Class” section on page 5-14 for more information.
Adding a Static MAC Address
Normally, MAC addresses are added to the MAC address table dynamically as traffic from a particular
MAC address enters an interface. You can add static MAC addresses to the MAC address table if desired.
To add a static MAC address to the MAC address table, enter the following command:
FWSM/contexta(config)# mac-address-table static interface_name mac_address
The interface_name is the source interface.
Setting the MAC Address Timeout
The default timeout value for dynamic MAC address table entries is 5 minutes, but you can change the
timeout.
To change the timeout, enter the following command:
FWSM/contexta(config)# mac-address-table aging-time timeout_value
The timeout_value (in minutes) is between 5 and 720 (12 hours). 5 minutes is the default.
Disabling MAC Address Learning
By default, each interface automatically learns the MAC addresses of entering traffic, and the FWSM
adds corresponding entries to the MAC address table. You can disable MAC address learning if desired.
To disable MAC address learning, enter the following command:
FWSM/contexta(config)# mac-learn interface_name disable
The no form of this command reenables MAC address learning.
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Configuring ARP Inspection
Viewing the MAC Address Table
You can view the entire MAC address table (including static and dynamic entries for both interfaces), or
you can view the MAC address table for an interface.
To view the MAC address table, enter the following command:
FWSM/contexta# show mac-address-table [interface_name]
The following example shows the entire MAC address table:
FWSM/contexta# show mac-address-table
interface
mac address
type
Time Left
----------------------------------------------------------------------outside
0009.7cbe.2100
static
inside
0010.7cbe.6101
static
inside
0009.7cbe.5101
dynamic
10
The following example shows the MAC address table for the inside interface:
FWSM/contexta# show mac-address-table inside
interface
mac address
type
Time Left
----------------------------------------------------------------------inside
0010.7cbe.6101
static
inside
0009.7cbe.5101
dynamic
10
Configuring ARP Inspection
This section describes ARP inspection and how to enable it, and includes the following topics:
•
ARP Inspection Overview, page 7-3
•
Adding a Static ARP Entry, page 7-4
•
Enabling ARP Inspection, page 7-4
ARP Inspection Overview
By default, ARP inspection is disabled on all interfaces; all ARP packets are allowed through the FWSM.
When you enable ARP inspection, the FWSM compares the MAC address, IP address, and source
interface in all ARP packets to static entries in the ARP table, and takes the following actions:
•
If the IP address, MAC address, and source interface match an ARP entry, the packet is passed
through.
•
If there is a mismatch between the MAC address, the IP address, or the interface, then the FWSM
drops the packet.
•
If the ARP packet does not match any entries in the static ARP table, then you can set the FWSM to
either forward the packet out all interfaces (flood), or to drop the packet.
ARP inspection prevents malicious users from impersonating other hosts or routers (known as ARP
spoofing). ARP spoofing can enable a “man-in-the-middle” attack. For example, a host sends an
ARP request to the gateway router; the gateway router responds with the gateway router MAC address.
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Configuring ARP Inspection
The attacker, however, sends another ARP response to the host with the attacker MAC address instead
of the router MAC address. The attacker can now intercept all the host traffic before forwarding it on to
the router.
ARP inspection ensures that an attacker cannot send an ARP response with the attacker MAC address,
so long as the correct MAC address and the associated IP address are in the static ARP table.
Adding a Static ARP Entry
ARP inspection compares ARP packets with static ARP entries in the ARP table.
To add a static ARP entry, enter the following command:
FWSM/contexta(config)# arp interface_name ip_address mac_address
For example, to allow ARP responses from the router at 10.1.1.1 with the MAC address 0009.7cbe.2100
on the outside interface, enter the following command:
FWSM/contexta(config)# arp outside 10.1.1.1 0009.7cbe.2100
Enabling ARP Inspection
To enable ARP inspection, enter the following command:
FWSM/contexta(config)# arp-inspection interface_name enable [flood | no-flood]
Where flood (the default) forwards non-matching ARP packets out all interfaces, and no-flood drops
non-matching packets.
For example, to enable ARP inspection on the outside interface, and to drop all non-matching ARP
packets, enter the following command:
FWSM/contexta(config)# arp-inspection outside enable no-flood
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8
Configuring IP Addresses, Routing, and DHCP
This chapter tells how to configure IP addresses, static routes, dynamic routing, and DHCP on the
Firewall Services Module (FWSM).
For routed and transparent mode, see the following sections:
•
Configuring IP Addresses, page 8-1
•
Configuring the Default Route, page 8-2
•
Configuring Static Routes, page 8-3
•
Configuring the DHCP Server, page 8-19
For routed mode only, see the following sections:
Note
•
Configuring OSPF, page 8-4
•
Configuring RIP, page 8-18
•
Configuring DHCP Relay, page 8-21
Multiple security contexts do not support dynamic routing protocols, such as RIP and OSPF.
Configuring IP Addresses
This section describes how to set the IP address(es) for routed mode or for transparent mode, and
includes the following topics:
•
Assigning IP Addresses to Interfaces for a Routed Firewall, page 8-2
•
Setting the Management IP Address for a Transparent Firewall, page 8-2
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Configuring the Default Route
Assigning IP Addresses to Interfaces for a Routed Firewall
Routed firewall mode only
To assign an IP address to a VLAN interface, enter the following command:
FWSM/contexta(config)# ip address interface_name ip_address mask [standby ip_address]
In single context mode, each interface address must be on a unique subnet. In multiple context mode, if
this interface is on a shared VLAN, then the IP address must be unique, and cannot be used by another
context on the shared VLAN. If the VLAN is unique, this IP address can be used by other contexts if
desired.
The standby keyword and address is used for failover. See the “Configuring Failover” section on
page 15-15 for more information.
For example, to set the IP address of the inside interface, enter the following command:
FWSM/contexta(config)# ip address inside 192.168.1.1 255.255.255.0
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
FWSM is to set the management IP address. This address is required because the FWSM uses this
address as the source address for traffic originating on the FWSM, 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:
FWSM/contexta(config)# ip address ip_address [mask] [standby ip_address]
This address must be on the same subnet as the upstream and downstream routers.
The standby keyword and address is used for failover. See the “Configuring Failover” section on
page 15-15 for more information.
Configuring the Default Route
The default route identifies the router IP address to which the FWSM sends all IP packets for which it
does not have a route. The FWSM might receive a default route from the dynamic routing protocol
(single mode only), but we recommend setting a static default route as a backup.
For transparent firewall mode, for traffic that originates on the FWSM and is destined for a non-directly
connected network, configure either a default route or static routes so the FWSM knows out of which
interface to send traffic. Traffic that originates on the FWSM might include communications to a syslog
server, Websense or N2H2 server, or AAA server.
The FWSM supports up to three equal cost routes on the same interface for load balancing.
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Configuring Static Routes
Routes that identify a specific destination address take precedence over the default route.
To set a default route, enter the following command:
FWSM/contexta(config)# route gateway_interface 0 0 gateway_ip [metric]
The metric is the number of hops to gateway_ip. The default is 1 if you do not specify a metric.
For example, if the FWSM receives traffic that it does not have a route for, it sends the traffic out the
outside interface to the router at 10.1.1.1:
FWSM/contexta(config)# route outside 0 0 10.1.1.1 1
Configuring Static Routes
Multiple context mode does not support dynamic routing, so you must use static routes for any networks
to which the FWSM is not directly connected; for example, when there is a router between a network
and the FWSM.
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 (see the previous section) 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 FWSM.
For transparent firewall mode, for traffic that originates on the FWSM and is destined for a non-directly
connected network, you need to configure either a default route or static routes so the FWSM knows out
of which interface to send traffic. Traffic that originates on the FWSM 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 FWSM supports up to three equal cost routes on the same interface for load balancing.
Static routes take precedence over dynamic routes if they have the same metric (number of router hops).
To add a static route, enter the following command:
FWSM/contexta(config)# route gateway_interface dest_ip mask gateway_ip [metric]
The metric is the number of hops to gateway_ip. The default is 1 if you do not specify a metric.
The addresses you specify for the static route are the addresses that are in the packet before entering the
FWSM and performing NAT.
For example, to send all traffic destined for 10.1.1.0/24 to the router (10.1.2.45) connected to the inside
interface, enter the following command:
FWSM/contexta(config)# route inside 10.1.1.0 255.255.255.0 10.1.2.45 1
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Configuring OSPF
The following static routes are equal cost routes that direct traffic to three different routers on the outside
interface. The FWSM sends 1/3 of the traffic to each router.
FWSM/contexta(config)# route outside 10.10.10.0 255.255.255.0 192.168.1.1
FWSM/contexta(config)# route outside 10.10.10.0 255.255.255.0 192.168.1.2
FWSM/contexta(config)# route outside 10.10.10.0 255.255.255.0 192.168.1.3
Configuring OSPF
Single context mode only
Routed firewall mode only
This section describes how to configure Open Shortest Path First (OSPF). For an overview of OSPF, see
the following topic:
•
OSPF Overview, page 8-4
To enable OSPF, see the following topic:
•
Enabling OSPF, page 8-5
After you enable OSPF, you can configure advanced options according to the following topics:
•
Redistributing Routes Between OSPF Processes, page 8-6
•
Configuring OSPF Interface Parameters, page 8-9
•
Configuring OSPF Area Parameters, page 8-11
•
Configuring OSPF NSSA, page 8-12
•
Configuring Route Summarization Between OSPF Areas, page 8-13
•
Configuring Route Summarization When Redistributing Routes into OSPF, page 8-14
•
Generating a Default Route, page 8-14
•
Configuring Route Calculation Timers, page 8-15
•
Logging Neighbors Going Up or Down, page 8-15
•
Displaying OSPF Update Packet Pacing, page 8-16
•
Monitoring OSPF, page 8-16
•
Restarting the OSPF Process, page 8-17
OSPF Overview
Single context mode only
Routed firewall mode only
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.
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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 FWSM 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 FWSM 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.
Redistribution between the two OSPF processes is supported. Static and connected routes configured on
OSPF-enabled interfaces on the FWSM can also be redistributed into the OSPF process. You cannot
enable RIP on any of the same interfaces as the interfaces on which OSPF is enabled. Redistribution
between RIP and OSPF is not supported.
The FWSM supports the following OSPF features:
•
Support of intra-area, interarea, and external (type I and Type II) routes.
•
Support of a virtual link.
•
OSPF link-state advertisement (LSA) flooding.
•
Authentication to OSPF packets (both password and MD5 authentication).
•
Support for configuring the FWSM as a designated router or a designated backup router. The FWSM
also can be set up as an area border router; however, the ability to configure the FWSM as an
autonomous system boundary router is limited to default information only (for example, injecting a
default route).
•
Support for stub areas and not-so-stubby-area (NSSA).
•
Area boundary router type-3 LSA filtering.
•
Advertisement of static and global address translations.
Enabling OSPF
Single context mode only
Routed firewall mode only
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.
To enable OSPF, follow these steps:
Step 1
To create an OSPF routing process, enter the following command:
FWSM(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.
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Step 2
To define the IP addresses on which OSPF runs and to define the area ID for that interface, enter the
following command:
FWSM(config-router)# network ip_address mask area area_id
This example shows how to enable OSPF:
FWSM(config)# router ospf 2
FWSM(config-router)# network 2.0.0.0 255.0.0.0 area 0
Redistributing Routes Between OSPF Processes
Single context mode only
Routed firewall mode only
The FWSM can control the redistribution of routes between OSPF routing processes. The FWSM
matches and changes routes according to settings in the redistribution command or by using a route
map. See also the “Generating a Default Route” section on page 8-14 for another use for route maps.
Note
The FWSM cannot redistribute routes between routing protocols. However, the FWSM can redistribute
static and connected routes.
This section includes the following topics:
•
Adding a Route Map, page 8-6
•
Redistributing Static, Connected, or OSPF Routes to an OSPF Process, page 8-8
Adding a Route Map
Single context mode only
Routed firewall mode only
To define a route map, follow these steps:
Step 1
To create a route map entry, enter the following command:
FWSM(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 FWSM 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:
FWSM(config-route-map)# match ip address acl_id [acl_id] [...]
See the “Adding a Standard Access Control List” section on page 10-17 to add the standard ACL.
If you specify more than one ACL, then the route can match any of the ACLs.
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•
To match any routes that have a specified metric, enter the following command:
FWSM(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:
FWSM(config-route-map)# match ip next-hop acl_id [acl_id] [...]
See the “Adding a Standard Access Control List” section on page 10-17 to add the standard ACL.
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:
FWSM(config-route-map)# match interface vlan number [vlan number]
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:
FWSM(config-route-map)# match ip route-source acl_id [acl_id] [...]
See the “Adding a Standard Access Control List” section on page 10-17 to add the standard ACL.
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:
FWSM(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:
FWSM(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:
FWSM(config-route-map)# set metric-type {type-1 | type-2}
•
To set the next hop router IP address, enter the following command:
FWSM(config-route-map)# set ip next-hop ip_address [ip_address] [...]
The next hop must be an adjacent router. If you specify more than one address, if the interface
associated with the first next hop address is down, then the next address is used.
The following example redistributes routes with a hop count equal to 1. The FWSM redistributes these
routes as external link-state advertisements (LSAs) with a metric of 5, metric type of Type 1, and a tag
equal to 1.
FWSM(config)# route-map
FWSM(config-route-map)#
FWSM(config-route-map)#
FWSM(config-route-map)#
1-to-2 permit
match metric 1
set metric 5
set metric-type type-1
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Redistributing Static, Connected, or OSPF Routes to an OSPF Process
Single context mode only
Routed firewall mode only
To redistribute static, connected, or OSPF routes from one process into another OSPF process, follow
these steps:
Step 1
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:
FWSM(config)# router ospf process_id
Step 2
To specify the routes you want to redistribute, enter the following command:
FWSM(config-router)# redistribute {ospf process_id | static | connect}
[match {internal | external 1 | external 2}] [metric metric-value]
[metric-type {type-1 | type-2}] [tag tag_value] [subnets] [route-map map_name]
The ospf process_id, static, and connect 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.
The following example redistributes routes from OSPF process 1 into OSPF process 2 by matching
routes with a metric equal to 1. The FWSM redistributes these routes as external link-state
advertisements (LSAs) with a metric of 5, metric type of Type 1, and a tag equal to 1.
FWSM(config)# route-map 1-to-2 permit
FWSM(config-route-map)# match metric 1
FWSM(config-route-map)# set metric 5
FWSM(config-route-map)# set metric-type type-1
FWSM(config-route-map)# set tag 1
FWSM(config-route-map)# router ospf 2
FWSM(config-router)# redistribute ospf 1 route-map 1-to-2
The following example causes the specified OSPF process routes to be redistributed into OSPF
process 109. The OSPF metric is remapped to 100.
FWSM(config)# router ospf 109
FWSM(config-router)# redistribute ospf 108 metric 100 subnets
FWSM(config-router)# redistribute static 108 metric 100 subnets
In the following example, 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.
FWSM(config)# router ospf 1
FWSM(config-router)# redistribute ospf 2 metric 5 metric-type external
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Configuring OSPF Interface Parameters
Single context mode only
Routed firewall mode only
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: ip ospf hello-interval, ip ospf dead-interval, and ip 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, follow these steps:
Step 1
To enter the interface configuration mode, enter the following command:
FWSM(config)# interface interface_name
Step 2
Enter any of the following commands:
•
To specify the authentication type for an interface, enter the following command:
FWSM(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:
FWSM(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 FWSM 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:
FWSM(config-interface)# ospf cost cost
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:
FWSM(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 FWSM sends on an OSPF interface,
enter the following command:
FWSM(config-interface)# ospf hello-interval seconds
The value must be the same for all nodes on the network.
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•
To enable OSPF MD5 authentication, enter the following command:
FWSM(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:
FWSM(config-interface)# ospf priority number_value
The number_value is between 0 to 255.
•
To specify the number of seconds between link-state advertisement (LSA) retransmissions for
adjacencies belonging to an OSPF interface, enter the following command:
FWSM(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:
FWSM(config-interface)# ospf transmit-delay seconds
The seconds is from 1 to 65535 seconds. The default is 1 second.
This example shows how to configure the OSPF interfaces:
FWSM(config)# router ospf 2
FWSM(config-router)# network 2.0.0.0 255.0.0.0 area 0
FWSM(config-router)# interface inside
FWSM(config-interface)# ospf cost 20
FWSM(config-interface)# ospf retransmit-interval 15
FWSM(config-interface)# ospf transmit-delay 10
FWSM(config-interface)# ospf priority 20
FWSM(config-interface)# ospf hello-interval 10
FWSM(config-interface)# ospf dead-interval 40
FWSM(config-interface)# ospf authentication-key cisco
FWSM(config-interface)# ospf message-digest-key 1 md5 cisco
FWSM(config-interface)# ospf authentication message-digest
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View your configuration by entering the following command:
FWSM(config)# show ip 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
Single context mode only
Routed firewall mode only
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 area border router, 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 area border router to prevent it from sending
summary link advertisement (LSAs type 3) into the stub area.
To specify area parameters for your network, follow these 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:
FWSM(config)# router ospf process_id
Step 2
Enter any of the following commands:
•
To enable authentication for an OSPF area, enter the following command:
FWSM(config-router)# area area-id authentication
•
To enable MD5 authentication for an OSPF area, enter the following command:
FWSM(config-router)# area area-id authentication message-digest
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•
To define an area to be a stub area, enter the following command:
FWSM(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:
FWSM(config-router)# area area-id default-cost cost
The cost is an integer from 1 to 65535. The default is 1.
This example shows how to configure the OSPF area parameters:
FWSM(config)# router
FWSM(config-router)#
FWSM(config-router)#
FWSM(config-router)#
FWSM(config-router)#
ospf
area
area
area
area
2
0 authentication
0 authentication message-digest
17 stub
17 default-cost 20
Configuring OSPF NSSA
Single context mode only
Routed firewall mode only
The OSPF implementation of a not-so-stubby-area (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 area border routers, which are flooded throughout
the whole routing domain. Summarization and filtering are supported during the translation.
You can simplify administration if you are an Internet service provider (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, follow these 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:
FWSM(config)# router ospf process_id
Step 2
Enter any of the following commands:
•
To define an NSSA area, enter the following command:
FWSM(config-router)# area area-id nssa [no-redistribution]
[default-information-originate]
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•
To summarize groups of addresses, enter the following command:
FWSM(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 autonomous system boundary Router (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:
FWSM(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
Single context mode only
Routed firewall mode only
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, follow these 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:
FWSM(config)# router ospf process_id
Step 2
To set the address range, enter the following command:
FWSM(config-router)# area area-id range ip-address mask [advertise | not-advertise]
This example shows how to configure route summarization between OSPF areas:
FWSM(config)# router ospf 1
FWSM(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
Single context mode only
Routed firewall mode only
When routes from other protocols are redistributed into OSPF, each route is advertised individually in
an external LSA. However, you can configure the FWSM 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, follow these 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:
FWSM(config)# router ospf process_id
Step 2
To set the summary address, enter the following command:
FWSM(config-router)# summary-address ip_address mask [not advertise] [tag tag]
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:
FWSM(config)# router ospf 1
FWSM(config-router)# summary-address 10.1.0.0 255.255.0.0
Generating a Default Route
Single context mode only
Routed firewall mode only
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, follow these 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:
FWSM(config)# router ospf process_id
Step 2
To force the autonomous system boundary router to generate a default route, enter the following
command:
FWSM(config-router)# default-information originate [always] [metric metric-value]
[metric-type {1 | 2}] [route-map map-name]
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This example shows how to generate a default route:
FWSM(config)# router ospf 2
FWSM(config-router)# default-information originate always
Configuring Route Calculation Timers
Single context mode only
Routed firewall mode only
You can configure the delay time between when OSPF receives a topology change and when it starts a
shortest path first (SPF) calculation. You also can configure the hold time between two consecutive SPF
calculations.
To configure route calculation timers, follow these 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:
FWSM(config)# router ospf process_id
Step 2
To configure the route calculation time, enter the following command:
FWSM(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.
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.
This example shows how to configure route calculation timers:
FWSM(config)# router ospf 1
FWSM(config-router)# timers spf 10 120
Logging Neighbors Going Up or Down
Single context mode only
Routed firewall mode only
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 ip 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.
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To log neighbors going up or down, follow these 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:
FWSM(config)# router ospf process_id
Step 2
To configure logging fir neighbors going up or down, enter the following command:
FWSM(config-router)# log-adj-changes [detail]
This example shows how to log neighbors:
FWSM(config)# router ospf 1
FWSM(config-router)# log-adj-changes detail
Displaying OSPF Update Packet Pacing
Single context mode only
Routed firewall mode only
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.
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:
FWSM# show ip ospf flood-list vlan number
Monitoring OSPF
Single context mode only
Routed firewall mode only
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.
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Configuring OSPF
To display various routing statistics, perform one of these tasks, as needed:
•
To display general information about OSPF routing processes, enter the following command:
FWSM# show ip ospf [process-id]
•
To display the internal OSPF routing table entries to the area border router and autonomous system
border router, enter the following command:
FWSM# show ip ospf border-routers
•
To display lists of information related to the OSPF database for a specific router, enter the following
command:
FWSM# show ip 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:
FWSM# show ip ospf flood-list interface interface-type
•
To display OSPF-related interface information, enter the following command:
FWSM# show ip ospf interface [interface-type interface-number]
•
To display OSPF neighbor information on a per-interface basis, enter the following command:
FWSM# show ip ospf neighbor [interface-name] [neighbor-id] detail
•
To display a list of all LSAs requested by a router, enter the following command:
FWSM# show ip ospf request-list [neighbor] [interface] [interface-neighbor]
•
To display a list of all LSAs waiting to be resent, enter the following command:
FWSM# show ip ospf retransmission-list [neighbor] [interface] [interface-neighbor]
•
To display a list of all summary address redistribution information configured under an OSPF
process, enter the following command:
FWSM# show ip ospf [process-id] summary-address
•
To display OSPF-related virtual links information, enter the following command:
FWSM# show ip ospf virtual-links
Restarting the OSPF Process
To restart an OSPF process, clear redistribution, or counters, enter the following command:
FWSM(config)# clear ip ospf pid {process | redistribution | counters
[neighbor [neighbor-interface] [neighbor-id]]}
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Configuring RIP
Configuring RIP
Single context mode only
Routed firewall mode only
This section describes how to configure Route Information Protocol (RIP), and includes:
•
RIP Overview, page 8-18
•
Enabling RIP, page 8-18
RIP Overview
Single context mode only
Routed firewall mode only
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 initially.
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 FWSM uses a limited version of RIP; it does not send out RIP updates that identify the networks
that the FWSM can reach. However, you can enable one or both of the following methods:
•
Passive RIP—The FWSM listens for RIP updates but does not send any updates about its networks
out of the interface.
Passive RIP allows the FWSM to learn about networks to which it is not directly connected.
•
Default Route Updates—Instead of sending normal RIP updates that describe all the networks
reachable through the FWSM, the FWSM sends a default route to participating devices that
identifies the FWSM as the default gateway.
You can use the default route option with passive RIP, or alone. You might use the default route
option alone if you use static routes on the FWSM, but do not want to configure static routes on
downstream routers. Typically, you would not enable the default route option on the outside
interface, because the FWSM is not typically the default gateway for the upstream router.
Enabling RIP
Single context mode only
Routed firewall mode only
To enable RIP on an interface, enter the following command:
FWSM(config)# rip interface_name {default | passive} [version {1 | 2
[authentication {text | md5} key key_id]}]
You can both types of RIP on an interface by entering the command two times, one for each method.
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Configuring the DHCP Server
If you want to use both modes, then enter the rip command two times with different modes for a given
interface. For example, enter the following commands:
FWSM(config)# rip inside default version 2 authentication md5 scorpius 1
FWSM(config)# rip inside passive version 2 authentication md5 scorpius 1
If you want to enable passive RIP on all interfaces, but only enable default routes on the inside interface,
enter the following commands:
FWSM(config)# rip inside default version 2 authentication md5 scorpius 1
FWSM(config)# rip inside passive version 2 authentication md5 scorpius 1
FWSM(config)# rip outside passive version 2 authentication md5 scorpius 1
Note
Before testing your configuration, flush the ARP caches on any routers connected to the FWSM. For
Cisco routers, use the clear arp command to flush the ARP cache.
Configuring the DHCP Server
This section describes how to use the Dynamic Host Configuration Protocol (DHCP) server provided by
the FWSM. It includes the following topics:
•
Enabling the DHCP Server, page 8-19
•
Using Cisco IP Phones with a DHCP Server, page 8-20
Enabling the DHCP Server
The FWSM 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 FWSM DHCP server does not support BOOTP requests.
Note
For multiple context mode, you cannot enable the DHCP server or DHCP relay on an interface that is
used by more than one context (a shared VLAN).
The DHCP server can be enabled on any interface. Clients must be directly connected to the FWSM and
cannot send requests through another relay agent or a router.
To enable the DHCP server on a given FWSM interface, follow these steps:
Step 1
To create a DHCP address pool, enter the following command:
FWSM/contexta(config)# dhcpd address ip_address-ip_address interface_name
The FWSM 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 FWSM interface.
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Configuring the DHCP Server
Step 2
(Optional) To specify the IP address(es) of the DNS server(s) the client will use, enter the following
command:
FWSM/contexta(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:
FWSM/contexta(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:
FWSM/contexta(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:
FWSM/contexta(config)# dhcpd domain domain_name
Step 6
To enable the DHCP daemon within the FWSM to listen for DHCP client requests on the enabled
interface, enter the following command:
FWSM/contexta(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:
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(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
Using Cisco IP Phones with a DHCP Server
Enterprises with small branch offices that implement a Cisco IP Telephony Voice over IP (VoIP) 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 host name of a single TFTP server.
Cisco IP Phones might also include DHCP option 3 in their requests, which lists the IP addresses of
default routers.
Cisco IP Phones might include both option 150 and 66 in a single request. In this case, the FWSM DHCP
server provides values for both options in the response if they are configured on the FWSM.
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Configuring DHCP Relay
You can configure the FWSM to send information for most options listed in RFC 2132. The following
table 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:
FWSM/contexta(config)# dhcpd option number string
•
To provide the IP address or name of a TFTP server for option 66, enter the following command:
FWSM/contexta(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:
FWSM/contexta(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 provide a list of router IP addresses for option 3, enter the following command:
FWSM/contexta(config)# dhcpd option 3 ip router_ip1 [router_ip2] [...]
Configuring DHCP Relay
Routed firewall mode only
A DHCP relay agent allows the FWSM 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 FWSM 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 (a shared VLAN).
To enable DHCP relay, follow these steps:
Step 1
To set the IP address of a DHCP server on a different interface from the DHCP client, enter the following
command:
FWSM/contexta(config)# dhcprelay server ip_address
You can use this command up to 10 times to identify up to 10 servers.
Step 2
To enable DHCP relay on the interface connected to the clients, enter the following command:
FWSM/contexta(config)# dhcprelay enable interface
Step 3
(Optional) To set the number of seconds allowed for relay address negotiation, enter the following
command:
FWSM/contexta(config)# dhcprelay timeout seconds
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Configuring DHCP Relay
Step 4
(Optional) To change the first default router address in the packet sent from the DHCP server to the
address of the FWSM interface, enter the following command:
FWSM/contexta(config)# dhcprelay setroute interface_name
This action allows the client to set its default route to point to the FWSM even if the DHCP server
specifies a different router.
If there is no default router option in the packet, the FWSM adds one containing the interface address.
The following example enables the FWSM to forward DHCP requests from clients connected to the
inside interface to a DHCP server on the outside interface:
FWSM/contexta(config)# dhcprelay server 201.168.200.4
FWSM/contexta(config)# dhcprelay enable inside
FWSM/contexta(config)# dhcprelay setroute inside
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9
Configuring Network Address Translation
Routed firewall mode only
This chapter describes Network Address Translation (NAT). In routed firewall mode, the Firewall
Services Module (FWSM) typically performs NAT between each network.
Note
In transparent firewall mode, both the inside and outside network are the same network, and the FWSM
does not perform NAT. See the “Configuring Connection Limits for Non-NAT Configurations” section
on page 6-10 for connection limits for which you must configure a NAT statement in transparent firewall
mode.
This chapter contains the following sections:
•
NAT Overview, page 9-1
•
Using Dynamic NAT and PAT, page 9-16
•
Using Static NAT, page 9-26
•
Using Static PAT, page 9-27
•
Bypassing NAT, page 9-29
•
NAT Examples, page 9-32
NAT Overview
This section describes how NAT works on the FWSM, and includes the following topics:
•
Introduction to NAT, page 9-2
•
NAT Types, page 9-3
•
Policy NAT, page 9-8
•
Outside NAT, page 9-10
•
NAT and Same Security Level Interfaces, page 9-11
•
Order of NAT Commands Used to Match Local Addresses, page 9-12
•
Maximum Number of NAT Statements, page 9-12
•
Global Address Guidelines, page 9-12
•
DNS and NAT, page 9-13
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•
Setting Connection Limits in the NAT Configuration, page 9-16
Introduction to NAT
Address translation substitutes the local address in a packet with a global address that is routable on the
destination network. In this document, all types of translation are generally referred to as “NAT.”
On the FWSM, you must specifically configure some interfaces to either use or to bypass NAT. For
example, when hosts on a higher security interface (inside) access hosts on a lower security interface
(outside), you must configure NAT on the inside hosts or specifically configure the inside hosts to bypass
NAT (See the “Configuring Interfaces” section on page 6-6 for more information about security levels).
Note
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.”
An inside host can communicate with the untranslated local address of the outside host without any
special configuration on the outside interface. However, you can also optionally configure NAT on the
outside network.
Interfaces that are on the same security level that you have allowed to communicate do not have to
perform NAT. You can, however, optionally configure NAT for these interfaces. (See the “Allowing
Communication Between Interfaces on the Same Security Level” section on page 6-8 for more
information.) In this case, there is no inside or outside when performing NAT between two interfaces.
Some of benefits of NAT are as follows:
Note
•
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 local 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 13-1 on page 13-2 for information about protocols that are not supported by NAT.
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Figure 9-1 shows a typical NAT scenario, with a private network on the inside. When the inside host
sends a packet to a web server, the local source address of the packet is changed to a routable global
address. When the server responds, it sends the response to the global address, and the FWSM receives
the packet. The FWSM then translates the global address to the local address before sending it on to
the host.
Figure 9-1
NAT Example
Web Server
www.cisco.com
Outside
209.165.201.2
Originating
Packet
FWSM
Source Addr Translation
10.1.2.27
209.165.201.10
Responding
Packet
Dest Addr Translation
209.165.201.10
10.1.2.27
10.1.2.1
10.1.2.27
104669
Inside
See the following commands for this example:
FWSM/contexta(config)# nat (inside) 1 10.1.2.0 255.255.255.0
FWSM/contexta(config)# global (outside) 1 209.165.201.1-209.165.201.15
NAT Types
You can implement address translation as dynamic NAT, Port Address Translation (PAT), static NAT, or
static PAT or as a mix of these types. You can also bypass NAT. See the following sections for
information about each type:
•
Dynamic NAT, page 9-3
•
PAT, page 9-4
•
Static NAT, page 9-5
•
Static PAT, page 9-5
•
Bypassing NAT, page 9-7
Dynamic NAT
Dynamic NAT translates a group of local addresses to a pool of global addresses that are routable on the
destination network. The global pool can include fewer addresses than the local group. When a local host
accesses the destination network, the FWSM assigns it an IP address from the global pool. Because the
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translation is only in place for the duration of the connection, a given user does not keep the same
IP address after the translation times out (see the timeout xlate command in the Catalyst 6500 Series
Switch and Cisco 7600 Series Router Firewall Services Module 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 control list (ACL)). Not only can you not predict the
global IP address of the host, but the FWSM does not create a translation at all unless the local host is
the initiator. See “Static NAT” or “Static PAT” below for reliable access to hosts.
Note
For the duration of the translation, a global host can initiate a connection to the local host if an ACL
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 ACL.
Dynamic NAT has these disadvantages:
•
If the global pool has fewer addresses than the local 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 global 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. PAT does not work with some
applications that have a data stream on one port and the control path on another, such as some multimedia
applications. See the “Inspection Engine Overview” section on page 13-1 for more information about
NAT and PAT support.
PAT
PAT translates multiple local addresses to a single global IP address. Specifically, the FWSM translates
the local address and local port for multiple connections and/or hosts to a single global address and a
unique port (above 1024). When a local host connects to the destination network on a given source port,
the FWSM assigns the global IP address to it and a unique port number. Each host receives the same
IP address, but because the source port numbers are unique, the responding traffic, which includes the
IP address and port number as the destination, can be sent to the correct host. Because there are over
64,000 ports available, you are unlikely to run out of addresses, which can happen with dynamic NAT.
Because the translation is specific to the local address and local port, each connection, which generates
a new source port, requires a separate translation. For example, 10.1.1.1:1025 requires a separate
translation from 10.1.1.1:1026.
The translation is only in place for the duration of the connection, so a given user does not keep the same
global IP address port number after the translation times out (see the timeout xlate command in the
Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Command
Reference). Users on the destination network, therefore, cannot reliably initiate a connection to a host
that uses PAT (even if the connection is allowed by an ACL). Not only can you not predict the local or
global port number of the host, but the FWSM does not create a translation at all unless the local host is
the initiator. See “Static NAT” or “Static PAT” below for reliable access to hosts.
PAT lets you use a single global address, thus conserving routable addresses. You can even use the
FWSM 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 “Inspection Engine Overview”
section on page 13-1 for more information about NAT and PAT support.
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Note
For the duration of the translation, a global host can initiate a connection to the local host if an ACL
allows it. Because the port address (both local and global) is unpredictable, a connection to the host is
unlikely. However in this case, you can rely on the security of the ACL.
Static NAT
Static NAT translates each local address to a fixed global address. With dynamic NAT and PAT, each host
uses a different address or port after the translation times out. Because the global address is the same for
each consecutive connection with static NAT, and a persistent translation rule exists, static NAT allows
hosts on the global network to initiate traffic to a local host (if there is an ACL that allows it).
The main difference between dynamic NAT and a range of addresses for static NAT is that static NAT
allows a global host to initiate a connection to a local host (if there is an ACL that allows it), while
dynamic NAT does not. You also need an equal number of global addresses as local addresses with
static NAT.
Static PAT
Static PAT is the same as static NAT, except it lets you specify the protocol (TCP or UDP) and port for
the local and global addresses.
This feature lets you identify the same global address across many different static statements, so long as
the port is different for each statement (you cannot use the same global address for multiple static NAT
statements).
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For example, if you want to provide a single address for global users to access FTP, HTTP, and SMTP,
but these are all actually different servers on the local network, you can specify static PAT statements
for each server that uses the same global IP address, but different ports (see Figure 9-2).
Figure 9-2
Static PAT
Host
Dest Addr Translation
209.165.201.3:21
10.1.2.27
Outside
Dest Addr Translation
209.165.201.3:25
10.1.2.29
Dest Addr Translation
209.165.201.3:80
10.1.2.28
Inside
SMTP server
10.1.2.29
HTTP server
10.1.2.28
114381
FTP server
10.1.2.27
See the following commands for this example:
FWSM/contexta(config)# static (inside,outside) tcp 209.165.201.3 ftp 10.1.2.27 ftp netmask
255.255.255.255
FWSM/contexta(config)# static (inside,outside) tcp 209.165.201.3 http 10.1.2.28 http
netmask 255.255.255.255
FWSM/contexta(config)# static (inside,outside) tcp 209.165.201.3 smtp 10.1.2.29 smtp
netmask 255.255.255.255
If the application used by the server requires an inspection engine to allow data channels on other ports,
such as FTP, then the server needs translation for other ports. Other protocols that require inspection
engines for data channels include TFTP, RTSP, and Skinny. See Chapter 13, “Configuring Application
Protocol Inspection,” for a complete list of protocols that require inspection engines. For example, add
the following line to the above configuration to translate all other ports from the FTP server at 10.1.2.27:
FWSM/contexta(config)# nat (inside) 1 10.1.2.27 255.255.255.255
FWSM/contexta(config)# global (outside) 1 209.165.201.3
The above configuration also allows the FTP server to initiate connections, if desired.
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 translate them to the 8080 port. Similarly, if you want to provide extra security, you can tell your
web users to connect to non-standard port 6785, and then translate them to port 80 on the local network.
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Bypassing NAT
When hosts on a higher security interface (inside) access hosts on a lower security interface (outside),
you must configure NAT on the inside hosts or specifically configure the inside interface to bypass NAT.
You might want to bypass NAT in the following circumstances:
•
You do not want the complication of NAT.
•
You are using an application that does not support NAT (see the “Inspection Engine Overview”
section on page 13-1 for information about inspection engines that do not support NAT).
•
You are using a transparent firewall and want to set connection limits.
•
You are using same security interfaces and want to set connection limits.
You can configure an interface to bypass NAT using three methods. All methods achieve compatibility
with inspection engines and simplification of your addressing. However, each method offers slightly
different capabilities, as follows:
•
Identity NAT—When you configure identity NAT (which is similar to dynamic NAT), you do not
specify global addresses, and therefore you do not specify a single global interface; you must use
identity NAT for connections through all interfaces. Therefore, you cannot choose to perform
normal translation on local 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 global
interface on which to translate the addresses. Make sure that the local addresses for which you use
identity NAT are routable on all networks that are available according to your ACLs.
For identity NAT, even though the translated address is the same as the local address, you cannot
initiate a connection from the outside to the inside (even if the interface ACL allows it). Use static
identity NAT or NAT exemption for this functionality. For same security interfaces, however, you
can initiate connections both ways.
•
Static identity NAT—Static identity NAT lets you specify the global interface on which you want to
allow the local 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 local and destination addresses when determining the local traffic to
translate (see the “Policy NAT” section on page 9-8 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 exemption allows both local and global hosts to initiate connections. Like
identity NAT, you do not specify global addresses, and therefore you do not specify a single global
interface; you must use NAT exemption for connections through all interfaces. However,
NAT exemption does allow you to specify the local and destination addresses when determining the
local traffic 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 ACL.
Note
In multiple context mode, you cannot initiate connections from an interface shared between
contexts when you use NAT exemption for the destination address. The classifier can only assign
packets from a shared interface to a context when you configure a static statement for the
destination address. For example, if you share the outside interface, you cannot use
NAT exemption on an inside interface if you want outside traffic to reach the inside addresses.
The classifier only looks at static statements where the global interface matches the source
interface of the packet. Because NAT exemption does not identify a global interface, the
classifier does not consider those NAT statements for classification purposes.
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NAT Overview
Policy NAT
Policy NAT lets you identify local traffic for address translation by specifying the source and destination
addresses in an extended ACL. You can also optionally specify the source and destination ports. Regular
NAT can only consider the local addresses.
Note
All types of NAT support policy NAT except for NAT exemption. NAT exemption uses an ACL to
identify the local addresses, but differs from policy NAT in that the ports are not considered. See the
“Bypassing NAT” section on page 9-29 for other differences.
With policy NAT, you can create multiple NAT or static statements that identify the same local address
as long as the source/port and destination/port combination is unique for each statement. You can then
match different global addresses to each source/port and destination/port pair.
Figure 9-3 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 local address is translated to 209.165.202.129. When the host
accesses the server at 209.165.200.225, the local 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 9-3
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
FWSM
Source Addr Translation
10.1.2.27
209.165.202.129
Source Addr 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
96845
10.1.2.0/24
See the following commands for this example:
FWSM/contexta(config)#
255.255.255.224
FWSM/contexta(config)#
255.255.255.224
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(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 9-4 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 local address is translated to 209.165.202.129. When the host accesses the same server for
Telnet services, the local address is translated to 209.165.202.130.
Figure 9-4
Policy NAT with Different Destination Ports
Web and Telnet server:
209.165.201.11
Internet
FWSM
Source Addr Translation
10.1.2.27:80
209.165.202.129
Source Addr 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
96846
10.1.2.0/24
See the following commands for this example:
FWSM/contexta(config)#
255.255.255.255 eq 80
FWSM/contexta(config)#
255.255.255.255 eq 23
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
access-list WEB permit tcp 10.1.2.0 255.255.255.0 209.165.201.11
access-list TELNET permit tcp 10.1.2.0 255.255.255.0 209.165.201.11
nat (inside) 1 access-list WEB
global (outside) 1 209.165.202.129
nat (inside) 2 access-list TELNET
global (outside) 2 209.165.202.130
For policy static NAT (and for NAT exemption, which also uses an ACL to identify traffic), both local
and global hosts can originate traffic. For locally originated traffic, the NAT ACL specifies the local
addresses and the destination addresses, but for globally originated traffic, the ACL identifies the local
addresses and the source addresses of global hosts who are allowed to connect to the local host using
this translation. Figure 9-5 shows a global host connecting to a local host. The local host has a policy
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static NAT translation that translates the local 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 local host cannot
connect to that network, nor can a host on that network connect to the local host.
Figure 9-5
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
FWSM
No Translation
Dest. Addr Translation
209.165.202.129
10.1.2.27
Inside
10.1.2.27
114762
10.1.2.0/24
Note
Policy NAT does not support SQL*Net, but it is supported by regular NAT. See the “Inspection Engine
Overview” section on page 13-1 for information about NAT support for other protocols.
Note
The number of access control entries (ACEs) used in policy NAT statements is limited. See the
“Maximum Number of ACEs” section on page 10-7 for information about limits on certain types of
rules.
Outside NAT
When hosts on a lower security interface (outside) access hosts on a higher security interface (inside),
you do not have to perform NAT on the outside hosts. (See the “Configuring Interfaces” section on
page 6-6 for more information about security levels.) You can, however, optionally configure NAT on
outside interfaces so that the outside host address is translated. Because the inside host is also typically
translated using a static NAT statement, both host addresses are translated.
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If you configure dynamic NAT or PAT (nat and global commands) for any hosts on an outside interface
when they access hosts on a given inside interface, then for any traffic between those two interfaces, the
NAT requirements change for the outside interface. Namely, the outside interface takes on the NAT
requirements of an inside interface, as follows:
•
No traffic can originate on the outside interface without being translated (or being configured to
bypass NAT).
This requirement is true even if the dynamic NAT statement includes only a few addresses. Other
addresses not included in the dynamic NAT statement require a NAT configuration to originate
connections, even if the NAT configuration is to bypass NAT and use the original addresses.
•
No traffic from the specified inside interface can access hosts behind the outside interface unless
you configure a static NAT statement, static identity NAT statement, or a NAT exemption statement
for the outside hosts.
If you only configure static NAT for the outside interface, these restrictions do not apply. Traffic between
the outside interface and a different inside interface is not affected.
Connection limitations that are set using NAT commands are not applied for outside NAT. (See the
“Setting Connection Limits in the NAT Configuration” section on page 9-16.)
You might want to use outside NAT, for example, to accommodate overlapping addresses. (See the
“Overlapping Networks” section on page 9-33.)
NAT and Same Security Level Interfaces
NAT is not required between same security level interfaces (see the “Allowing Communication Between
Interfaces on the Same Security Level” section on page 6-8 to enable same security communication).
However, you can optionally configure NAT if desired. Because there is no “inside” and “outside” when
configuring NAT between two interfaces at the same security, connection limits that you set in the NAT
configuration apply in both directions.
If you configure dynamic NAT or PAT (nat and global commands) for any hosts on a local interface
when they access hosts on a given same security interface, then for any traffic between those two
interfaces, the NAT requirements change for the local interface. Namely, the local interface takes on the
NAT requirements of an inside interface, as follows:
•
No traffic can originate on the local interface without being translated (or being configured to bypass
NAT).
This requirement is true even if the dynamic NAT statement includes only a few addresses. Other
addresses not included in the dynamic NAT statement require a NAT configuration to originate
connections, even if the NAT configuration is to bypass NAT and use the original addresses.
•
No traffic from the specified same security interface can access hosts behind the local interface
unless you configure a static NAT statement, a NAT exemption statement, or an identity NAT
statement for the local hosts.
If you only configure static NAT, identity NAT, or NAT exemption for the local interface, these
restrictions do not apply. Traffic between the local interface and a different same security interface is not
affected.
You might want to configure NAT exemption or identity NAT on same security interfaces to set
connection limits. (See the “Setting Connection Limits in the NAT Configuration” section on page 9-16.)
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Note
The FWSM 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 “Inspection Support”
section on page 13-2 for supported inspection engines.
Order of NAT Commands Used to Match Local Addresses
The FWSM matches local traffic 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. We do not recommend overlapping addresses in static
statements because unexpected results can occur.
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 local traffic
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 local traffic best. We do not recommend using
overlapping statements; they use more memory and can slow the performance of the FWSM.
Maximum Number of NAT Statements
The FWSM supports the following numbers of nat, global, and static commands divided between all
contexts or in single mode:
•
nat command—2 K
•
global command—1,051
•
static command—2 K
The FWSM also supports up to 3942 access control entries (ACEs) in ACLs used for policy NAT for
single mode, and 7,272 ACEs for multiple mode.
Global Address Guidelines
When you translate the local address to a global address, you can use the following global addresses:
•
Addresses on the same network as the global interface.
If you use addresses on the same network as the global interface (through which traffic exits the
FWSM), the FWSM uses proxy ARP to answer any requests for translated addresses, and thus
intercepts traffic destined for a local address. This solution simplifies routing, because the FWSM
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 global interface.
•
Addresses on a unique network.
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If you need more addresses than are available on the global interface network, you can identify
addresses on a different subnet. The FWSM uses proxy ARP to answer any requests for translated
addresses, and thus intercepts traffic destined for a local address. If you use OSPF, and you advertise
routes on the global interface, then the FWSM advertises the translated addresses. If the global
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 translated addresses to the
FWSM.
DNS and NAT
You might need to configure the FWSM 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 NAT 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 FWSM to statically translate the ftp.cisco.com local address
(10.1.3.14) to a global address (209.165.201.10) that is visible on the outside network (See Figure 9-6).
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 local address receive the local address from the DNS server, and
not the global address.
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When an inside host sends a DNS request for the address of ftp.cisco.com, the DNS server replies with
the global address (209.165.201.10). The FWSM 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 9-6
DNS Reply Modification
DNS Server
2
1
DNS Query
ftp.cisco.com?
3
DNS Reply
209.165.201.10
Outside
Static Translation
10.1.3.14
209.165.201.10
FWSM
4
DNS Reply Modification
209.165.201.10
10.1.3.14
DNS Reply
10.1.3.14
User ftp.cisco.com
10.1.3.14
104642
Inside
5
6
FTP Request
10.1.3.14
See the following command for this example:
FWSM/contexta(config)# static (inside,outside) 209.165.201.10 10.1.3.14 netmask
255.255.255.255 dns
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Figure 9-6 shows a web server and DNS server on the outside. The FWSM 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 local address, 209.165.20.10. Because you want inside
users to use the translated global address for ftp.cisco.com (10.1.2.56) you need to configure DNS reply
modification for the static translation.
Figure 9-7
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
Outside
6
Dest Addr. Translation
10.1.2.56
209.165.201.10
DNS Reply
209.165.201.10
FWSM
3
5
Inside
4
DNS Reply
10.1.2.56
User
10.1.2.27
FTP Request
10.1.2.56
104644
DNS Reply Modification
209.165.201.10
10.1.2.56
See the following command for this example:
FWSM/contexta(config)# static (outside,inside) 10.1.2.56 209.165.201.10 netmask
255.255.255.255 dns
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Setting Connection Limits in the NAT Configuration
The NAT configuration lets you set some options for traffic that cannot be set anywhere else, including
the following:
•
Setting the maximum connections—The maximum number of simultaneous TCP and/or UDP
connections for the entire subnet up to 65,536.
•
Setting the maximum embryonic connections—The maximum number of embryonic connections
per host up to 65,536. An embryonic connection is a connection request that has not finished the
necessary handshake between source and destination. This limit enables the TCP intercept feature.
(See the “Other Protection Features” section on page 1-6 for more information.)
•
Disabling TCP sequence number randomization—Only use this option if another in-line firewall is
also randomizing sequence numbers and the result is scrambling the data.
When you do not want to use NAT, such as for a transparent firewall or same security interfaces, you can
set these options in an identity NAT statement or a NAT exemption statement.
Using Dynamic NAT and PAT
This section includes the following topics:
•
Dynamic NAT and PAT Implementation, page 9-17
•
Configuring NAT or PAT, page 9-23
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Dynamic NAT and PAT Implementation
For dynamic NAT and PAT, you first configure a NAT statement (the nat command) identifying the
addresses on a given interface that you want to translate. Then you configure a separate global statement
(the global command) to specify the translated addresses when exiting another interface (in the case of
PAT, this is one address). Each NAT statement matches a global statement by comparing the NAT ID, a
number that you assign each statement (see Figure 9-8).
Figure 9-8
NAT and Global ID Matching
Web Server:
www.cisco.com
Outside
Global 1: 209.165.201.3209.165.201.10
Source Addr Translation
10.1.2.27
209.165.201.3
NAT 1: 10.1.2.0/24
10.1.2.27
104673
Inside
See the following commands for this example:
FWSM/contexta(config)# nat (inside) 1 10.1.2.0 255.255.255.0
FWSM/contexta(config)# global (outside) 1 209.165.201.3-209.165.201.10
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You can enter a NAT statement for each interface using the same NAT ID; they all use the same global
statement when traffic exits a given interface. For example, you can configure NAT statements for Inside
and DMZ interfaces, both on NAT ID 1. Then you configure a global statement on the Outside interface
that is also on ID 1. Traffic from the Inside interface and the DMZ interface share a NAT pool or a
PAT address when exiting the Outside interface (see Figure 9-9).
Figure 9-9
NAT Statements on Multiple Interfaces
Web Server:
www.cisco.com
Source Addr 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
Source Addr Translation
10.1.2.27
209.165.201.3
10.1.1.15
NAT 1: 10.1.2.0/24
104674
Inside
10.1.2.27
See the following commands for this example:
FWSM/contexta(config)# nat (inside) 1 10.1.2.0 255.255.255.0
FWSM/contexta(config)# nat (dmz) 1 10.1.1.0 255.255.255.0
FWSM/contexta(config)# global (outside) 1 209.165.201.3-209.165.201.10
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You can also enter a global statement for each interface using the same NAT ID. If you enter a global
statement for the Outside and DMZ interfaces on ID 1, then the Inside NAT statement identifies traffic
to be translated when going to both the Outside and the DMZ interfaces. Similarly, if you also enter a
NAT statement for the DMZ interface on ID 1, then the global statement on the Outside interface is also
used for DMZ traffic. (See Figure 9-10).
Figure 9-10 Global and NAT Statements on Multiple Interfaces
Web Server:
www.cisco.com
Source Addr 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
Global 1: 10.1.1.23
Source Addr Translation
10.1.2.27
209.165.201.3
DMZ
10.1.1.15
NAT 1: 10.1.2.0/24
10.1.2.27
Source Addr Translation
10.1.2.27
10.1.1.23:2024
104670
Inside
See the following commands for this example:
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(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
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If you use different NAT IDs, you can identify different sets of host addresses to have different global
addresses. For example, on the Inside interface, you can have two NAT statements on two different
NAT IDs. On the Outside interface, you configure two global statements 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 9-11). If
you use policy NAT, you can specify the same local addresses for multiple NAT statements, as long as
the source address/port and destination address/port is unique for each statement. For regular NAT, you
must identify different local addresses for each statement.
Figure 9-11 Different NAT IDs
Web Server:
www.cisco.com
Outside
Global 1: 209.165.201.3209.165.201.10
Global 2: 209.165.201.11
Source Addr Translation
192.168.1.14
209.165.201.11:4567
NAT 1: 10.1.2.0/24
Source Addr Translation
10.1.2.27
209.165.201.3
NAT 2: 192.168.1.0/24
10.1.2.27
104671
Inside
192.168.1.14
See the following commands for this example:
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(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
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You can enter multiple global statements for one interface using the same NAT ID; the FWSM uses the
dynamic NAT global statements first, in the order they are in the configuration, and then uses the PAT
global statements in order. You might want to enter both a dynamic NAT global statement and a PAT
global statement 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 used up. Similarly, you might enter two PAT
statements if you need more than the approximately 64000 connections that a single PAT global
statement supports (see Figure 9-12).
Figure 9-12 NAT and PAT Together
Web Server:
www.cisco.com
Source Addr 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
Source Addr Translation
10.1.2.29
209.165.201.5:6096
Source Addr Translation
10.1.2.28
209.165.201.4
NAT 1: 10.1.2.0/24
Inside
10.1.2.29
104672
10.1.2.27
10.1.2.28
See the following commands for this example:
FWSM/contexta(config)# nat (inside) 1 10.1.2.0 255.255.255.0
FWSM/contexta(config)# global (outside) 1 209.165.201.3-209.165.201.4
FWSM/contexta(config)# global (outside) 1 209.165.201.5
For outside NAT (see the “Outside NAT” section on page 9-10 for more information), you need to
identify the NAT statement 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 statement without the
outside option. In this case, you can identify the same addresses in both statements and use the same
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NAT ID (see Figure 9-13). Note that for outside NAT (DMZ interface to Inside interface), the inside host
uses a static NAT statement to allow outside access, so both the source and destination addresses are
translated.
Figure 9-13 Outside NAT and Inside NAT Combined
Outside
Source Addr 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
Source Addr Translation
10.1.1.15
10.1.2.30
Dest. Addr Translation
10.1.1.5
10.1.2.27
114998
Inside
10.1.2.27
See the following commands for this example:
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(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) 10.1.2.27 10.1.1.5 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
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Configuring NAT or PAT
This section tells 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 global addresses, and for PAT you specify
a single address.
Figure 9-14 shows a typical dynamic NAT scenario. Only local traffic can originate connections, and the
global address is dynamically assigned from a pool.
Figure 9-14 Dynamic NAT
10.1.1.1
209.165.201.1
10.1.1.2
209.165.201.2
Inside Outside
114403
FWSM
Figure 9-15 shows a typical dynamic PAT scenario. Only local traffic can originate connections, the
global address is the same for each translation, but the port is dynamically assigned.
Figure 9-15 Dynamic PAT
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
114405
FWSM
10.1.1.1:1025
For more information about dynamic NAT, see the “Dynamic NAT” section on page 9-3. For more
information about PAT, see the “PAT” section on page 9-4.
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.
To configure dynamic NAT or PAT, follow these steps:
Step 1
To identify the local addresses that you want to translate, enter one of the following commands:
•
Policy NAT:
FWSM/contexta(config)# nat (local_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 statements. For example, you can identify
10.1.1.0 in one statement, but 10.1.1.1 in another. The traffic is matched to a policy NAT statement
in order, until the first match, or for regular NAT, using the best match.
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See the following description about options for this command:
– access-list acl_name—Identify the local addresses and destination addresses using an extended
ACL. Create the ACL using the access-list command (see the “Adding an Extended Access
Control List” section on page 10-13). This ACL should include only permit access control
entries (ACEs). You can optionally specify the local and destination ports in the ACL using the
eq operator.
– nat_id—An integer between 1 and 65535. The NAT ID must match a global statement NAT ID.
See the “Dynamic NAT and PAT Implementation” section on page 9-17 for more information
about how NAT IDs are used. 0 is reserved for NAT exemption. (See the “Configuring NAT
Exemption” section on page 9-31 for more information about NAT exemption.)
– dns—If your NAT statement 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 global address and one needs the local
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 9-13 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. (See the “Outside NAT” section on page 9-10 for more information.)
– norandomseq—No TCP Initial Sequence Number (ISN) randomization. Only use this option
if another in-line firewall is also randomizing sequence numbers and the result is scrambling the
data. See the “Security Level Overview” section on page 6-6 for information about TCP
sequence numbers.
– tcp tcp_max_conns, udp udp_max_conns—The maximum number of simultaneous TCP and/or
UDP connections for the entire subnet up to 65,536. The default is 0 for both protocols, which
means the maximum connections.
– emb_limit—The maximum number of embryonic connections per host up to 65,536. An
embryonic connection is a connection request that has not finished the necessary handshake
between source and destination. This limit enables the TCP Intercept feature. (See the “Other
Protection Features” section on page 1-6 for more information.) The default is 0, which means
the maximum embryonic connections. You must enter the tcp tcp_max_conns before you enter
the emb_limit. If you want to use the default value for tcp_max_conns, but change the
emb_limit, then enter 0 for tcp_max_conns. Not supported for outside NAT.
•
Regular NAT:
FWSM/contexta(config)# nat (local_interface) nat_id local_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 statement
NAT ID. See the “Dynamic NAT and PAT Implementation” section on page 9-17 for more
information about how NAT IDs are used. 0 is reserved for identity NAT. See the “Configuring
Identity NAT” section on page 9-29 for more information about identity NAT.
See the policy NAT command above for information about other options.
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Step 2
To identify the global address(es) to which you want to translate the local addresses when they exit a
particular interface, enter the following command:
FWSM/contexta(config)# global (global_interface) nat_id {global_ip[-global_ip] |
interface}
This NAT ID must match a nat statement NAT ID. The matching nat statement 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”:
192.168.1.1-192.168.2.254
For example, to translate the 10.1.1.0/24 network on the inside interface, and to change the embryonic
limit, enter the following command. You must specify the tcp tcp_max_conns before specifying
emb_limit, so the command enters the default setting of 0 for tcp_max_conns.
FWSM/contexta(config)# nat (inside) 1 10.1.1.0 255.255.255.0 tcp 0 200
FWSM/contexta(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:
FWSM/contexta(config)# nat (inside) 1 10.1.1.0 255.255.255.0 tcp 5000 1000 udp 5000
FWSM/contexta(config)# global (outside) 1 209.165.201.5
FWSM/contexta(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:
FWSM/contexta(config)# nat (dmz) 1 10.1.2.0 255.255.255.0 outside dns
FWSM/contexta(config)# global (inside) 1 10.1.1.45
To identify a single local address with two different destination addresses using policy NAT, enter the
following commands (see Figure 9-3 on page 9-8 for a related graphic):
FWSM/contexta(config)#
255.255.255.224
FWSM/contexta(config)#
255.255.255.224
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(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 local address/destination address pair that use different ports using policy NAT, enter
the following commands (see Figure 9-4 on page 9-9 for a related graphic):
FWSM/contexta(config)#
255.255.255.255 eq 80
FWSM/contexta(config)#
255.255.255.255 eq 23
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
access-list WEB permit tcp 10.1.2.0 255.255.255.0 209.165.201.11
access-list TELNET permit tcp 10.1.2.0 255.255.255.0 209.165.201.11
nat (inside) 1 access-list WEB
global (outside) 1 209.165.202.129
nat (inside) 2 access-list TELNET
global (outside) 2 209.165.202.130
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Using Static NAT
This section tells how to configure a static translation.
Figure 9-16 shows a typical static NAT scenario. Both local and global traffic can originate connections,
and the global address is statically assigned.
Figure 9-16 Static NAT
10.1.1.1
209.165.201.1
10.1.1.2
209.165.201.2
Inside Outside
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You cannot use the same local or global address in multiple static statements between the same two
interfaces. Do not use an address that is also defined as a dynamic PAT address in a global statement.
For more information about static NAT, see the “Static NAT” section on page 9-5.
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.
To configure static NAT, enter one of the following commands.
•
For policy static NAT, enter the following command:
FWSM/contexta(config)# static (local_interface,global_interface)
{global_ip | interface} access-list acl_name [dns] [norandomseq] [[tcp] tcp_max_conns
[emb_limit]] [udp udp_max_conns]
Create the ACL using the access-list command (see the “Adding an Extended Access Control List”
section on page 10-13). This ACL should include only permit access control entries (ACEs). The
source subnet mask used in the ACL is also used for the global addresses. You can also specify the
local and destination ports in the ACL using the eq operator. See the “Policy NAT” section on
page 9-8 for more information.
See the “Configuring NAT or PAT” section on page 9-23 for information about the other options.
•
To configure regular static NAT, enter the following command:
FWSM/contexta(config)# static (local_interface,global_interface)
{global_ip | interface} local_ip [netmask mask] [dns] [norandomseq]
[[tcp] tcp_max_conns [emb_limit]] [udp udp_max_conns]
See the “Configuring NAT or PAT” section on page 9-23 for information about the options.
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For example, the following policy static NAT example shows a single local address that is translated to
two global addresses depending on the destination address (see Figure 9-3 on page 9-8 for a related
graphic):
FWSM/contexta(config)#
255.255.255.224
FWSM/contexta(config)#
255.255.255.224
FWSM/contexta(config)#
FWSM/contexta(config)#
access-list NET1 permit ip host 10.1.2.27 209.165.201.0
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):
FWSM/contexta(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):
FWSM/contexta(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:
FWSM/contexta(config)# static (inside,dmz) 10.1.1.0 10.1.2.0 netmask 255.255.255.0
Using Static PAT
This section tells how to configure a static port translation. Static PAT lets you translate the local IP
address to a global IP address, as well as the local port to a global port. You can choose to translate the
same port, which lets you translate specific types of traffic, or you can take it further by translating to a
different port.
Figure 9-17 shows a typical static PAT scenario. Both local and global traffic can originate connections,
and the global address and port is statically assigned.
Figure 9-17 Static PAT
10.1.1.1:23
209.165.201.1:23
10.1.1.2:8080
209.165.201.2:80
Inside Outside
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You cannot use the same local or global address in multiple static statements between the same two
interfaces. Do not use an address that is also defined as a dynamic PAT address in a global statement.
For more information about static PAT, see the “Static PAT” section on page 9-5.
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.
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To configure static PAT, enter one of the following commands.
•
For policy static PAT, enter the following command:
FWSM/contexta(config)# static (local_interface,global_interface) {tcp | udp}
{global_ip | interface} global_port access-list acl_name [dns] [norandomseq]
[[tcp] tcp_max_conns [emb_limit]] [udp udp_max_conns]
Create the ACL using the access-list command (see the “Adding an Extended Access Control List”
section on page 10-13). The protocol in the ACL 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 ACL.
Specify the port using the eq operator. This ACL should include only permit access control entries
(ACEs). The source subnet mask used in the ACL is also used for the global addresses.
See the “Configuring NAT or PAT” section on page 9-23 for information about the other options.
•
To configure regular static PAT, enter the following command:
FWSM/contexta(config)# static (local_interface,global_interface) {tcp | udp}
{global_ip | interface} global_port local_ip local_port [netmask mask]
[dns] [norandomseq] [[tcp] tcp_max_conns [emb_limit]] [udp udp_max_conns]
See the “Configuring NAT or PAT” section on page 9-23 for information about the options.
For example, for Telnet traffic initiated from hosts on the 10.1.3.0 network to the FWSM 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:
FWSM/contexta(config)# access-list TELNET permit tcp host 10.1.1.15 eq telnet 10.1.3.0
255.255.255.0 eq telnet
FWSM/contexta(config)# static (inside,outside) tcp 10.1.2.14 telnet access-list TELNET
For HTTP traffic initiated from hosts on the 10.1.3.0 network to the FWSM outside interface (10.1.2.14),
you can redirect the traffic to the inside host at 10.1.1.15 by entering:
FWSM/contexta(config)# access-list HTTP permit tcp host 10.1.1.15 eq http 10.1.3.0
255.255.255.0 eq http
FWSM/contexta(config)# static (inside,outside) tcp 10.1.2.14 http access-list HTTP
To redirect Telnet traffic from the FWSM outside interface (10.1.2.14) to the inside host at 10.1.1.15,
enter the following command:
FWSM/contexta(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 local Telnet server above 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.
FWSM/contexta(config)# static (inside,outside) tcp 10.1.2.14 telnet 10.1.1.15 telnet
netmask 255.255.255.255
FWSM/contexta(config)# nat (inside) 1 10.1.1.15 255.255.255.255
FWSM/contexta(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 global
address from the Telnet server, you can still configure traffic initiated from the Telnet server to use the
same global 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
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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 global address.
FWSM/contexta(config)# static (inside,outside) tcp 10.1.2.14 telnet 10.1.1.15 telnet
netmask 255.255.255.255
FWSM/contexta(config)# nat (inside) 1 10.1.1.15 255.255.255.255
FWSM/contexta(config)# global (outside) 1 10.1.2.14
FWSM/contexta(config)# nat (inside) 2 10.1.1.0 255.255.255.0
FWSM/contexta(config)# global (outside) 2 10.1.2.78
To translate a well-known port (80) to another port (8080), enter the following command:
FWSM/contexta(config)# static (inside,outside) tcp 10.1.2.45 80 10.1.1.16 8080 netmask
255.255.255.255
Bypassing NAT
You can bypass NAT using identity NAT, static identity NAT, or NAT exemption. See the “Bypassing
NAT” section on page 9-7 for more information about these methods. This section includes the following
topics:
•
Configuring Identity NAT, page 9-29
•
Configuring Static Identity NAT, page 9-30
•
Configuring NAT Exemption, page 9-31
Configuring Identity NAT
Identity NAT translates the local IP address to the same IP address, and only local traffic can originate
connections. (For same security level interfaces, hosts connected to any interface on the same security
level can initiate traffic.)
Figure 9-18 shows a typical identity NAT scenario.
Figure 9-18 Identity NAT
209.165.201.1
209.165.201.1
209.165.201.2
209.165.201.2
Inside Outside
Note
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FWSM
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.
To configure identity NAT, enter the following command:
FWSM/contexta(config)# nat (local_interface) 0 local_ip [mask [dns] [outside |
[norandomseq] [[tcp] tcp_max_conns [emb_limit]] [udp udp_max_conns]]]
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See the “Configuring NAT or PAT” section on page 9-23 for information about the options.
For example, to use identity NAT for the inside 10.1.1.0/24 network, enter the following command:
FWSM/contexta(config)# nat (inside) 0 10.1.1.0 255.255.255.0
Configuring Static Identity NAT
Static identity NAT translates the local IP address to the same IP address, and allows both local and
global traffic to originate connections. Static identity NAT lets you use regular NAT or policy NAT.
Policy NAT allow you to identify the local and destination addresses when determining the local traffic
to translate (see the “Policy NAT” section on page 9-8 for more 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 9-19 shows a typical static identity NAT scenario.
Figure 9-19 Static Identity NAT
209.165.201.1
209.165.201.1
209.165.201.2
209.165.201.2
Inside Outside
Note
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FWSM
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.
To configure static identity NAT, enter one of the following commands:
•
To configure policy static identity NAT, enter the following command:
FWSM/contexta(config)# static (local_interface,global_interface) local_ip access-list
acl_id [dns] [norandomseq] [[tcp] tcp_max_conns [emb_limit]] [udp udp_max_conns]
Create the ACL using the access-list command (see the “Adding an Extended Access Control List”
section on page 10-13). This ACL should include only permit access control entries (ACEs). Make
sure the source address in the ACL matches the first local_ip in this command. See the “Policy NAT”
section on page 9-8 for more information.
See the “Configuring NAT or PAT” section on page 9-23 for information about the other options.
•
To configure regular static identity NAT, enter the following command:
FWSM/contexta(config)# static (local_interface,global_interface) local_ip local_ip
[netmask mask] [dns] [norandomseq] [[tcp] tcp_max_conns [emb_limit]] [udp
udp_max_conns]
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Specify the same IP address for both local_ip variables.
See the “Configuring NAT or PAT” section on page 9-23 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:
FWSM/contexta(config)# static (inside,outside) 10.1.1.3 10.1.1.3 netmask 255.255.255.255
The following command uses static identity NAT for an outside address (209.165.201.15) when accessed
by the inside:
FWSM/contexta(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:
FWSM/contexta(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 local address that uses identity NAT
when accessing one destination address, and a translation when accessing another:
FWSM/contexta(config)#
255.255.255.224
FWSM/contexta(config)#
255.255.255.224
FWSM/contexta(config)#
FWSM/contexta(config)#
access-list NET1 permit ip host 10.1.2.27 209.165.201.0
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 translates the local IP address to the same IP address, and allows both local and global
traffic to originate connections. NAT exemption lets you specify the local and destination addresses
when determining the local traffic to translate (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 ACL.
Note
In multiple context mode, you cannot initiate connections from an interface shared between contexts
when you use NAT exemption for the destination address. The classifier can only assign packets from a
shared interface to a context when you configure a static statement for the destination address. For
example, if you share the outside interface, you cannot use NAT exemption on an inside interface if you
want outside traffic to reach the inside addresses. The classifier only looks at static statements where the
global interface matches the source interface of the packet. Because NAT exemption does not identify a
global interface, the classifier does not consider those NAT statements for classification purposes.
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Figure 9-19 shows a typical NAT exemption scenario.
Figure 9-20 NAT Exemption
209.165.201.1
209.165.201.1
209.165.201.2
209.165.201.2
Inside Outside
Note
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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.
To configure NAT exemption, enter the following command:
FWSM/contexta(config)# FWSM/contexta(config)# nat (local_interface) 0 access-list acl_name
[outside] [norandomseq] [[tcp] tcp_max_conns [emb_limit]] [udp udp_max_conns]
Create the ACL using the access-list command (see the “Adding an Extended Access Control List”
section on page 10-13). This ACL should include only permit access control entries (ACEs). Do not
specify the local and destination ports in the ACL; NAT exemption does not consider the ports.
See the “Configuring NAT or PAT” section on page 9-23 for information about the other options.
For example, to exempt an inside network when accessing any destination address, enter the following
command:
FWSM/contexta(config)# access-list EXEMPT permit ip 10.1.2.0 255.255.255.0 any
FWSM/contexta(config)# nat (inside) 0 access-list EXEMPT
To exempt an inside address when accessing two different destination addresses, enter the following
commands:
FWSM/contexta(config)# access-list NET1 permit ip 10.1.2.0 255.255.255.0 209.165.201.0
255.255.255.224
FWSM/contexta(config)# access-list NET1 permit ip 10.1.2.0 255.255.255.0 209.165.200.224
255.255.255.224
FWSM/contexta(config)# nat (inside) 0 access-list NET1
NAT Examples
The following sections show typical scenarios that use NAT solutions:
•
Overlapping Networks, page 9-33
•
Redirecting Ports, page 9-34
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Overlapping Networks
In Figure 9-21, the FWSM connects two private networks with overlapping address ranges.
Figure 9-21 Using Outside NAT with Overlapping Networks
192.168.100.2
192.168.100.2
outside
10.1.1.2
inside
192.168.100.0/24
dmz
192.168.100.0/24
FWSM
192.168.100.3
10.1.1.1
192.168.100.3
104675
192.168.100.1
Two networks use an overlapping address space (192.168.100.0/24), but hosts on each network must
communicate (as allowed by ACLs). 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 FWSM, 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, follow these 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:
FWSM/contexta(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:
FWSM/contexta(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
FWSM:
FWSM/contexta(config)# route dmz 192.168.100.128 255.255.255.128 10.1.1.2 1
FWSM/contexta(config)# route dmz 192.168.100.0 255.255.255.128 10.1.1.2 1
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The FWSM already has a connected route for the inside network. These static routes allow the FWSM
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 FWSM receives this packet, the FWSM translates the source address from 192.168.100.2
to 10.1.3.2.
3.
Then the FWSM translates the destination address from 10.1.2.2 to 192.168.100.2, and the packet
is forwarded.
Redirecting Ports
Figure 9-22 illustrates a typical network scenario in which the port redirection feature might be useful.
Figure 9-22 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
Inside
209.165.201.25
Outside
104678
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 FWSM 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, complete the following steps:
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Step 1
Configure PAT for the inside network by entering the following commands:
FWSM/contexta(config)# nat (inside) 1 0.0.0.0 0.0.0.0 0 0
FWSM/contexta(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:
FWSM/contexta(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:
FWSM/contexta(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 FWSM outside interface address to 10.1.1.5 by entering the following
command:
FWSM/contexta(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:
FWSM/contexta(config)# static (inside,outside) tcp 209.165.201.15 8080 10.1.1.7 www
netmask 255.255.255.255
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10
Controlling Network Access with
Access Control Lists
This chapter tells how to control network access through the Firewall Services Module (FWSM) using
access control lists (ACLs). You can also use ACLs for other purposes, for example, to identify addresses
for NAT, AAA, or OSPF route redistribution. This chapter describes how to create ACLs for these
purposes as well as for network access, but this chapter only describes how to apply the ACLs for
network access. Refer to the NAT, AAA, or IP chapters for information about applying ACLs for these
other purposes.
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).
This chapter contains the following sections:
•
Access Control List Overview, page 10-1
•
Adding an Extended Access Control List, page 10-13
•
Adding an EtherType Access Control List, page 10-16
•
Adding a Standard Access Control List, page 10-17
•
Simplifying Access Control Lists with Object Grouping, page 10-18
•
Manually Committing Access Control Lists and Rules, page 10-24
•
Adding Remarks to Access Control Lists, page 10-25
•
Logging Extended Access Control List Activity, page 10-26
Access Control List Overview
ACLs are made up of one or more Access Control Entries (ACEs). An ACE is a single entry in an ACL
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.
This section includes the following topics:
•
Access Control List Types and Uses, page 10-2
•
Access Control List Guidelines, page 10-6
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Access Control List Types and Uses
This section includes the following topics:
•
Access Control List Type Overview, page 10-2
•
Controlling Network Access for IP Traffic (Extended), page 10-2
•
Identifying Traffic for AAA rules (Extended), page 10-3
•
Controlling Network Access for IP Traffic for a Given User (Extended), page 10-4
•
Identifying Addresses for Policy NAT and NAT Exemption (Extended), page 10-4
•
VPN Management Access (Extended), page 10-5
•
Controlling Network Access for Non-IP Traffic (EtherType), page 10-5
•
Redistributing OSPF Routes (Standard), page 10-6
Access Control List Type Overview
Table 10-1 lists the types of ACLs you can create and how you can use them.
Table 10-1 Access Control List Types and Uses
ACL Use
ACL Type
For more information...
Control network access for IP traffic
Extended
See the “Controlling Network Access for IP Traffic
(Extended)” section on page 10-2.
Identify traffic for AAA rules
Extended
See the “Identifying Traffic for AAA rules (Extended)”
section on page 10-3.
Control network access for IP traffic for a Extended,
given user
downloaded from a
AAA server per user
See the “Controlling Network Access for IP Traffic for a
Given User (Extended)” section on page 10-4.
Identify addresses for NAT (policy NAT
and NAT exemption)
Extended
See the “Identifying Addresses for Policy NAT and NAT
Exemption (Extended)” section on page 10-4.
Establish VPN management access
Extended
See the “VPN Management Access (Extended)” section
on page 10-5.
For transparent firewall mode, control
network access for non-IP traffic
EtherType
See the “Controlling Network Access for Non-IP Traffic
(EtherType)” section on page 10-5.
Identify OSPF route redistribution
Standard
See the “Redistributing OSPF Routes (Standard)” section
on page 10-6.
Controlling Network Access for IP Traffic (Extended)
Extended ACLs control connections based on source address, destination address, protocol, or port. The
FWSM does not allow any traffic through unless it is explicitly permitted by an extended ACL. This rule
is true for both routed firewall mode and transparent firewall mode.
For TCP and UDP connections, you do not need an ACL to allow returning traffic, because the FWSM
allows all returning traffic for established connections. See the “Stateful Inspection Feature” section on
page 1-5 for more information. For connectionless protocols such as ICMP, however, you either need
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ACLs to allow ICMP in both directions (by applying ACLs to the source and destination interfaces), or
you need to enable the ICMP inspection engine (see the “ICMP Inspection Engine” section on
page 13-10). The ICMP inspection engine treats ICMP sessions as stateful connections.
You can apply one ACL of each type to each direction of an interface. You can also apply the same ACLs
on multiple interfaces.
To control network access for IP traffic, perform the following task:
•
Create and apply the ACL according to the “Adding an Extended Access Control List” section on
page 10-13.
Allowing Special Traffic through the Transparent Firewall
In routed firewall mode, some types of traffic are blocked even if you allow them in an ACL, including
unsupported dynamic routing protocols, DHCP (unless you configure DHCP relay), and multicast
traffic. Transparent firewall mode can allow any IP traffic through. Because these special types of traffic
are connectionless, you need to apply an ACL to both interfaces, so returning traffic is allowed through.
Table 10-2 lists common traffic types that you can allow through the transparent firewall. See
Appendix D, “Addresses, Protocols, and Ports Reference,” for more protocols and ports.
Table 10-2 Transparent Firewall Special Traffic
Traffic Type
BGP
1
DHCP
2
EIGRP3
Protocol or Port
Notes
TCP port 179
—
UDP ports 67 and 68
If you enable the DHCP server, then the FWSM
does not pass DHCP packets.
Protocol 88
—
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).
OSPF
Protocol 89
—
RIP (v1 or v2)
UDP port 520
—
1. Border Gateway Protocol
2. Dynamic Host Configuration Protocol
3. Enhanced Interior Gateway Routing Protocol
Identifying Traffic for AAA rules (Extended)
ACLs can be used with AAA in several ways.
•
To identify traffic for network access authorization using a TACACS+ server, perform the following
tasks:
a. Add the ACL using the “Adding an Extended Access Control List” section on page 10-13.
Permit entries in the ACL mark matching traffic for authorization, while deny entries exclude
matching traffic from authorization.
b. Apply the ACL using the aaa authorization match command in the “Configuring TACACS+
Authorization” section on page 12-24.
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•
To identify traffic for network access authentication using a TACACS+ or RADIUS server, perform
the following tasks:
a. Add the ACL using the “Adding an Extended Access Control List” section on page 10-13.
Permit entries in the ACL mark matching traffic for authentication, while deny entries exclude
matching traffic from authentication.
b. Apply the ACL using the aaa authentication match command in the “Configuring
Authentication for Network Access” section on page 12-20.
•
To identify traffic for network access accounting using a TACACS+ or RADIUS server, perform the
following tasks:
a. Add the ACL using the “Adding an Extended Access Control List” section on page 10-13.
Permit entries in the ACL mark matching traffic for accounting, while deny entries exclude
matching traffic from accounting.
b. Apply the ACL using the aaa accounting match command in the “Configuring Accounting for
Network Access” section on page 12-27.
Controlling Network Access for IP Traffic for a Given User (Extended)
When you configure user authentication for network access, you can also choose to configure user
authorization that determines the specific access privileges for each user. If you use a RADIUS server,
you can configure the RADIUS server to download a dynamic ACL to be applied to the user, or the server
can send the name of an ACL that you already configured on the FWSM. See the following tasks for
each method.
•
For dynamic ACLs, all ACL configuration takes place on the RADIUS server. Perform the following
tasks:
a. Refer to the “Adding an Extended Access Control List” section on page 10-13 for ACL syntax
and guidelines.
b. To create the ACL on the RADIUS server, see the “Configuring the RADIUS Server to
Download Per-User Access Control Lists” section on page 12-25.
•
For a downloaded ACL name, perform the following tasks:
a. Configure an extended ACL according to the “Adding an Extended Access Control List”
section on page 10-13.
This extended ACL is not assigned to an interface, but is designed to be applied to one or more
users.
b. Use the ACL name according to the “Configuring the RADIUS Server to Download Per-User
Access Control List Names” section on page 12-27.
These per-user ACLs must be as restrictive or more restrictive than an extended ACL that is assigned to
the interface. For example, if the ACL assigned to the inside interface allows all users to have only HTTP
access to other networks, it would not make sense to configure an authorization ACL for that user to
access FTP.
Identifying Addresses for 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 ACL. You can also optionally specify the source and destination ports. Regular
NAT can only consider the local addresses.
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NAT exemption statements also use ACLs, but you cannot specify the ports.
To use ACLs with NAT, perform the following tasks:
1.
Add the ACL using the “Adding an Extended Access Control List” section on page 10-13. This ACL
can contain only permit elements. Specify ports using the eq operator.
2.
Use the ACL in the nat and static commands described in the following sections:
– “Using Dynamic NAT and PAT” section on page 9-16
– “Using Static NAT” section on page 9-26
– “Using Static PAT” section on page 9-27
– “Configuring Static Identity NAT” section on page 9-30
– “Configuring NAT Exemption” section on page 9-31
VPN Management Access (Extended)
You can use an extended ACL in VPN commands. See the following tasks for each method.
•
To identify hosts allowed to connect to the FWSM over an IPSec site-to-site tunnel, perform the
following tasks:
a. Add the ACL using the “Adding an Extended Access Control List” section on page 10-13.
Specify the FWSM address as the source address. Specify the remote address(es) for the
destination address.
b. Use the ACL in the crypto map match address command according to the “Configuring a
Site-to-Site Tunnel” section on page 11-9.
•
To identify the traffic that should be tunneled from a VPN client, perform the following tasks:
a. Add the ACL using the “Adding an Extended Access Control List” section on page 10-13.
Specify the FWSM address as the source address, and the VPN pool addresses as the destination
addresses.
b. Then use the ACL in the vpngroup split-tunnel command according to the “Configuring VPN
Client Access” section on page 11-7.
The FWSM only supports IPSec tunnels that terminate on the FWSM and that allow access to the FWSM
for management purposes; you cannot terminate a tunnel on the FWSM for traffic that goes through the
FWSM to another network.
Controlling Network Access for Non-IP Traffic (EtherType)
Transparent firewall mode only
You can configure an ACL that controls traffic based on its EtherType. The FWSM can control any
EtherType identified by a 16-bit hexadecimal number. EtherType ACLs support Ethernet V2 frames.
802.3-formatted frames are not handled by the ACL because they use a length field as opposed to a type
field. Bridge protocol data units (BPDUs), which are handled by the ACL, are the only exception: they
are SNAP-encapsulated, and the FWSM is designed to specifically handle BPDUs.
To control non-IP traffic, perform the following task:
•
Create and apply the ACL according to the “Adding an EtherType Access Control List” section on
page 10-16.
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Redistributing OSPF Routes (Standard)
Single context mode only
Standard ACLs include only the destination address. You can use a standard ACL with the route-map
command to control the redistribution of OSPF routes, perform the following tasks:
1.
Create the ACL according to the “Adding a Standard Access Control List” section on page 10-17.
2.
Create a route map and apply it according to the “Redistributing Routes Between OSPF Processes”
section on page 8-6.
Access Control List Guidelines
See the following guidelines for creating ACLs:
•
Access Control Entry Order, page 10-6
•
Access Control List Implicit Deny, page 10-6
•
Access Control List Commit, page 10-6
•
Maximum Number of ACEs, page 10-7
•
IP Addresses Used for Access Control Lists When You Use NAT, page 10-7
•
Inbound and Outbound Access Control Lists, page 10-10
Access Control Entry Order
An ACL is made up of one or more Access Control Entries (ACEs). Depending on the ACL 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 ACL name is appended to the end of the ACL.
The order of ACEs is important. When the FWSM decides whether to forward or drop a packet, the
FWSM 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 ACL that
explicitly permits all traffic, no further statements are ever checked.
Access Control List Implicit Deny
ACLs 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 FWSM except for particular
addresses, then you need to deny the particular addresses and then permit all others.
Access Control List Commit
When you add an ACE to an ACL, the FWSM activates the ACL by committing it to the network
processors. The FWSM waits a short period of time after you last entered an access-list command and
then commits the ACL. This waiting period minimizes the number of times the FWSM commits the
ACL. If you enter multiple ACEs within the short waiting period, or paste ACEs at the command prompt,
then the FWSM does not commit the ACL until the waiting period has passed and you do not enter more
entries. The FWSM displays a message similar to the following after it commits the ACL:
Access Rules Download Complete: Memory Utilization: < 1%
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Large ACLs of approximately 60K ACEs can take 3 to 4 minutes to commit, depending on the size.
To manually commit ACLs, see the “Manually Committing Access Control Lists and Rules” section on
page 10-24.
For information about exceeding memory limits, see the “Maximum Number of ACEs” section.
Maximum Number of ACEs
The FWSM supports a maximum of 80K rules for the entire system in single mode, and 142K rules for
multiple mode. Rules include ACEs, ACEs used for policy NAT, filters, AAA, ICMP, Telnet, SSH,
HTTP, and established rules. See the “Rule Limits” section on page A-5 for the limits for each rule type.
Some ACLs use more memory than others, and these include ACLs that use large port number ranges or
overlapping networks (for example one ACE specifies 10.0.0.0/8 and another specifies 10.1.1.0/24).
Depending on the type of ACL, the actual limit the system can support will be less than 80K
(single mode) or 142K (multiple mode).
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, and expanded ACEs count towards the system
limit. To view the number of expanded ACEs in an ACL, enter the show access-list acl_name command.
When you add an ACE, and the FWSM compiles the ACL, the console displays the memory used in a
message similar to the following:
Access Rules Download Complete: Memory Utilization: < 1%
If you exceed the memory limitations, you receive an error message and a system message (106024), and
all the ACLs that were added in this compilation are removed from the configuration. Only the set of
ACLs that were successfully committed in the previous commitment are used. For example, if you paste
1,000 ACEs at the prompt, and the last ACE exceeds the memory limitations, all 1,000 ACEs are
rejected.
IP Addresses Used for Access Control Lists When You Use NAT
When you use NAT, the IP addresses you specify for an ACL depend on the interface to which the ACL
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 ACLs: the direction does not determine the address
used, only the interface does.
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For example, you want to apply an ACL to the inbound direction of the inside interface. You configure
the FWSM to perform NAT on the inside source addresses when they access outside addresses. Because
the ACL 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 ACL is the real
address (see Figure 10-1).
Figure 10-1 IP Addresses in ACLs: 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:
FWSM/contexta(config)# access-list INSIDE extended permit ip 10.1.1.0 255.255.255.0 host
209.165.200.225
FWSM/contexta(config)# access-group INSIDE in interface inside
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If you want to allow an outside host to access an inside host, you can apply an inbound ACL on the
outside interface. You need to specify the translated address of the inside host in the ACL because that
address is the address that can be used on the outside network. (See Figure 10-2.)
Figure 10-2 IP Addresses in ACLs: 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:
FWSM/contexta(config)# access-list OUTSIDE extended permit ip host 209.165.200.225 host
209.165.201.5
FWSM/contexta(config)# access-group OUTSIDE in interface outside
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If you perform NAT on both interfaces, then keep in mind the addresses that are visible to a given
interface. In Figure 10-3, an outside server uses static NAT so that a translated address appears on the
inside network.
Figure 10-3 IP Addresses in ACLs: 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:
FWSM/contexta(config)# access-list INSIDE extended permit ip 10.1.1.0 255.255.255.0 host
10.1.1.56
FWSM/contexta(config)# access-group INSIDE in interface inside
For an example of IP addresses used in outbound ACLs, see Figure 10-5 on page 10-12.
Inbound and Outbound Access Control Lists
Traffic flowing across an interface in the FWSM can be controlled in two ways. Traffic that enters the
FWSM can be controlled by attaching an inbound ACL to the source interface. Traffic that exits the
FWSM can be controlled by attaching an outbound ACL to the destination interface. To allow any traffic
to enter the FWSM, you must attach an inbound ACL to an interface; otherwise, the FWSM
automatically drops all traffic that enters that interface. By default, traffic can exit the FWSM on any
interface unless you restrict it using an outbound ACL, which adds restrictions to those already
configured in the inbound ACL.
Note
“Inbound” and “outbound” refer to the application of an ACL on an interface, either to traffic entering
the FWSM on an interface or traffic exiting the FWSM 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.
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You might want to use an outbound ACL to simplify your ACL configuration. For example, if you want
to allow three inside networks on three different interfaces to access each other, you can create a simple
inbound ACL that allows all traffic on each inside interface. (See Figure 10-4.)
Figure 10-4 Inbound ACLs
Web Server:
209.165.200.225
FWSM
Inside
ACL Inbound
Permit from any to any
HR
ACL Inbound
Permit from any to any
10.1.2.0/24
Eng
ACL Inbound
Permit from any to any
10.1.3.0/24
104639
10.1.1.0/24
Outside
See the following commands for this example:
FWSM/contexta(config)# access-list INSIDE extended permit ip any any
FWSM/contexta(config)# access-group INSIDE in interface inside
FWSM/contexta(config)# access-list HR extended permit ip any any
FWSM/contexta(config)# access-group HR in interface hr
FWSM/contexta(config)# access-list ENG extended permit ip any any
FWSM/contexta(config)# access-group ENG in interface eng
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Then, if you want to allow only certain hosts on the inside networks to access a web server on the outside
network, you can create a more restrictive ACL that allows only the specified hosts and apply it to the
outbound direction of the outside interface (see Figure 10-4). See the “IP Addresses Used for Access
Control Lists When You Use NAT” section on page 10-7 for information about NAT and IP addresses.
The outbound ACL prevents any other hosts from reaching the outside network.
Figure 10-5 Outbound ACL
Web Server:
209.165.200.225
FWSM
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
209.165.201.4
Static NAT
HR
ACL Inbound
Permit from any to any
Eng
ACL Inbound
Permit from any to any
10.1.2.67
209.165.201.6
Static NAT
10.1.3.34
209.165.201.8
Static NAT
104638
Inside
See the following commands for this example:
FWSM/contexta(config)# access-list INSIDE extended permit ip any any
FWSM/contexta(config)# access-group INSIDE in interface inside
FWSM/contexta(config)# access-list HR extended permit ip any any
FWSM/contexta(config)# access-group HR in interface hr
FWSM/contexta(config)# access-list ENG extended permit ip any any
FWSM/contexta(config)# access-group ENG in interface eng
FWSM/contexta(config)# access-list OUTSIDE extended permit tcp host 209.165.201.4
host 209.165.200.225 eq www
FWSM/contexta(config)# access-list OUTSIDE extended permit tcp host 209.165.201.6
host 209.165.200.225 eq www
FWSM/contexta(config)# access-list OUTSIDE extended permit tcp host 209.165.201.8
host 209.165.200.225 eq www
FWSM/contexta(config)# access-group OUTSIDE out interface outside
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Adding an Extended Access Control List
Access Control List Override
When you download a per-user access control list (ACL), the permit/deny status of the access-group
access list is maintained unless you specifically change the permit/deny status so that the downloaded
per-user access list overrides the interface access list. If ACL override is enabled, user traffic is
permitted if it is permitted by the per-user access list, regardless of the permit status of interface access
list.
Note
The access-group per-user-override command is implemented for the inbound ACLs only, not for the
outbound ACLs.
To enable ACL override, enter the following command:
fwsm/context(config)# access-group
per-user-override
access-list {in
| out} interface
interface_name
Adding an Extended Access Control List
An extended ACL is made up of one or more ACEs, in which you can specify the 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 Control Lists with Object Grouping”
section on page 10-18.
For TCP and UDP connections, you do not need to also apply an ACL on the destination interface to
allow returning traffic, because the FWSM allows all returning traffic for established connections. See
the “Stateful Inspection Feature” section on page 1-5 for more information. For connectionless protocols
such as ICMP, however, you either need ACLs to allow ICMP in both directions (by applying ACLs to
the source and destination interfaces), or you need to enable the ICMP inspection engine. (See the
“ICMP Inspection Engine” section on page 13-10.) The ICMP inspection engine treats ICMP sessions
as stateful connections. For transparent mode, you can allow protocols with an extended ACL that are
otherwise blocked by a routed mode FWSM, including BGP, DHCP, and multicast streams. Because
these protocols do not have sessions on the FWSM to allow returning traffic, these protocols also require
ACLs on both interfaces.
You can apply only one ACL of each type (extended and EtherType) to each direction of an interface.
You can apply the same ACLs on multiple interfaces.
Note
If you change the ACL configuration, and you do not want to wait for existing connections to time out
before the new ACL information is used, you can clear the translation table using the clear xlate
command. However, clearing the translation table disconnects all current connections.
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Adding an Extended Access Control List
To add an extended ACL and apply it to an interface, follow these steps:
Step 1
Add one or more ACEs of the following types using the same ACL name.
When you enter the access-list command for a given ACL name, the ACE is added to the end of the ACL.
Tip
Enter the acl_name in upper case letters so the name is easy to see in the configuration. You might want
to name the ACL for the interface (for example, INSIDE), or for the purpose (for example, NO_NAT or
VPN).
Note
You specify a network mask in the access-list command (for example, 255.255.255.0 for a class C
mask). This method is different from the Cisco IOS software access-list command, which uses wildcard
bits (for example, 0.0.0.255).
•
Add an ACE for a specific protocol by entering the following command:
FWSM/contexta(config)# access-list acl_name [extended] {deny | permit} protocol
source_address mask dest_address mask
This type of ACE lets you specify any protocol for the source and destination addresses, but not
ports. Typically, you identify ip for the protocol, but other protocols are accepted.
Enter host before the IP address to specify a single address. In this case, do not enter a mask. Enter
any instead of the address and mask to specify any address.
For a list of protocol names, see the “Protocols and Applications” section on page D-5.
For information about logging options that you can add to the end of the ACE, see the “Logging
Extended Access Control List Activity” section on page 10-26.
See the following examples:
The following ACL allows all hosts (on the interface to which you apply the ACL) to go through the
FWSM:
FWSM/contexta(config)# access-list ACL_IN extended permit ip any any
The following sample ACL prevents hosts on 192.168.1.0/24 from accessing the 209.165.201.0/27
network. All other addresses are permitted:
FWSM/contexta(config)# access-list ACL_IN extended deny tcp 192.168.1.0 255.255.255.0
209.165.201.0 255.255.255.224
FWSM/contexta(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.
FWSM/contexta(config)# access-list ACL_IN extended permit ip 192.168.1.0 255.255.255.0
209.165.201.0 255.255.255.224
•
Add an ACE for TCP or UDP ports by entering the following command:
FWSM/contexta(config)# access-list acl_name [extended] {deny | permit} {tcp | udp}
source_address mask [operator port] dest_address mask [operator port]
Enter host before the IP address to specify a single address. In this case, do not enter a mask. Enter
any instead of the address and mask to specify any address.
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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
For a list of permitted keywords and well-known port assignments, see the “TCP and UDP Ports”
section on page D-6. 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.
For information about logging options that you can add to the end of the ACE, see the “Logging
Extended Access Control List Activity” section on page 10-26.
See the following example:
The following ACL restricts all hosts (on the interface to which you apply the ACL) from accessing
a website at address 209.165.201.29. All other traffic is allowed.
FWSM/contexta(config)# access-list ACL_IN extended deny tcp any host 209.165.201.29 eq
www
FWSM/contexta(config)# access-list ACL_IN extended permit ip any any
•
Add an ACE for ICMP by entering the following command:
FWSM/contexta(config)# access-list acl_name [extended] {deny | permit} icmp
source_address mask dest_address mask [icmp_type]
Enter host before the IP address to specify a single address. In this case, do not enter a mask. Enter
any instead of the address and mask to specify any address.
Because ICMP is a connectionless protocol, you either need ACLs to allow ICMP in both directions
(by applying ACLs to the source and destination interfaces), or you need to enable the ICMP
inspection engine (see the “ICMP Inspection Engine” section on page 13-10). The ICMP inspection
engine treats ICMP sessions as stateful connections.
To control ping, specify echo-reply (0) (FWSM to host) or echo (8) (host to FWSM). See the “ICMP
Types” section on page D-9 for a list of ICMP types.
For information about logging options that you can add to the end of the ACE, see the “Logging
Extended Access Control List Activity” section on page 10-26.
Step 2
To apply an extended ACL to the inbound or outbound direction of an interface, enter the following
command:
FWSM/contexta(config)# access-group acl_name {in | out} interface interface_name
You can apply one ACL of each type (extended and EtherType) to both directions of the interface. See
the “Inbound and Outbound Access Control Lists” section on page 10-10 for more information about
ACL directions.
For connectionless protocols, you need to apply the ACL to the source and destination interfaces if you
want traffic to pass in both directions. For example, you can allow BGP in an ACL in transparent mode,
and you need to apply the ACL to both interfaces.
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Adding an EtherType Access Control List
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):
FWSM/contexta(config)# access-list ACL_OUT extended permit tcp any host 209.165.201.12 eq
www
FWSM/contexta(config)# access-group ACL_OUT in interface outside
You also need to configure NAT for the web server. See the “Using Static NAT” section on page 9-26
for more information.
The following ACLs allow all hosts to communicate between the inside and hr networks, but only
specific hosts to access the outside network:
FWSM/contexta(config)# access-list ANY extended permit ip any any
FWSM/contexta(config)# access-list OUT extended permit ip host 209.168.200.3 any
FWSM/contexta(config)# access-list OUT extended permit ip host 209.168.200.4 any
FWSM/contexta(config)# access-group ANY in interface inside
FWSM/contexta(config)# access-group ANY in interface hr
FWSM/contexta(config)# access-group OUT out interface outside
Adding an EtherType Access Control List
Transparent firewall mode only
An EtherType ACE controls any EtherType identified by a 16-bit hexadecimal number. You can identify
some types by a keyword for convenience.
Because EtherTypes are connectionless, you need to apply the ACL to both interfaces if you want traffic
to pass in both directions.
For example, you can permit or deny bridge protocol data units (BPDUs). By default, all BPDUs are
denied. The FWSM receives trunk port (Cisco proprietary) BPDUs because FWSM ports are trunk ports.
Trunk BPDUs have VLAN information inside the payload, so the FWSM modifies the payload with the
outgoing VLAN if you allow BPDUs. If you use failover, you must allow BPDUs on both interfaces with
an EtherType ACL to avoid bridging loops.
If you allow MPLS, ensure that Label Distribution Protocol (LDP) and Tag Distribution Protocol (TDP)
TCP connections are established through the FWSM by configuring both MPLS routers connected to the
FWSM to use the IP address on the FWSM 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 FWSM:
router(config)# mpls ldp router-id interface force
Or
router(config)# tag-switching tdp router-id interface force
You can apply only one ACL of each type (extended and EtherType) to each direction of an interface.
You can also apply the same ACLs on multiple interfaces.
To add an EtherType ACL and apply it to an interface, follow these steps:
Step 1
Add one or more ACEs using the same ACL name by entering the following command:
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FWSM/contexta(config)# access-list acl_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.
When you enter the access-list command for a given ACL name, the ACE is added to the end of the ACL.
Tip
Step 2
Enter the acl_name in upper case letters so the name is easy to see in the configuration. You might want
to name the ACL for the interface (for example, INSIDE), or for the purpose (for example, MPLS or
IPX).
To apply an EtherType ACL to the inbound or outbound direction of an interface, enter the following
command:
FWSM/contexta(config)# access-group acl_name {in | out} interface interface_name
You can apply one ACL of each type (extended and EtherType) to both directions of the interface. See
the “Inbound and Outbound Access Control Lists” section on page 10-10 for more information about
ACL directions.
Because EtherTypes are connectionless, you need to apply the ACL to both interfaces if you want traffic
to pass in both directions.
For example, the following sample ACL allows common EtherTypes originating on the inside interface:
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(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 ACL allows some EtherTypes through the FWSM, but denies IPX:
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(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 ACL denies traffic with EtherType 0x1256 but allows all others on both interfaces:
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(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 Control List
Single context mode only
Standard ACLs identify the destination IP addresses of OSPF routes, and can be used in a route map for
OSPF redistribution. Standard ACLs cannot be applied to interfaces to control traffic.
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The following command adds a standard ACE. To add another ACE at the end of the ACL, enter another
access-list command specifying the same ACL name. Apply the ACL using the “Adding a Route Map”
section on page 8-6.
To add an ACE, enter the following command:
FWSM(config)# access-list acl_name standard {deny | permit} {any | ip_address mask}
The following sample ACL identifies routes to 192.168.1.0/24:
FWSM(config)# access-list OSPF standard permit 192.168.1.0 255.255.255.0
Simplifying Access Control Lists with Object Grouping
This section describes how to use object grouping to simplify ACL creation and maintenance, and
includes the following topics:
•
How Object Grouping Works, page 10-18
•
Adding Object Groups, page 10-19
•
Nesting Object Groups, page 10-22
•
Displaying Object Groups, page 10-24
•
Removing Object Groups, page 10-24
•
Using Object Groups with an Access Control List, page 10-23
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
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.
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Note
The ACE system limit applies to expanded ACLs. 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 ACL, enter the show access-list acl_name command.
Adding Object Groups
This section describes how to add object groups, and includes the following topics:
Note
•
Adding a Protocol Object Group, page 10-19
•
Adding a Network Object Group, page 10-20
•
Adding a Service Object Group, page 10-20
•
Adding an ICMP Type Object Group, page 10-21
If you add new members to an existing object group that is already in use by an ACE in a large ACL,
recommitting the ACL can take a long time, depending on the size of the ACL and the object group. In
some cases, making this change can cause the FWSM to devote over an hour to committing the ACL,
during which time you cannot access the terminal. We recommend that you first remove the ACE that
refers to the object group, make your change, and then add the ACE back to the ACL. See the “Manually
Committing Access Control Lists and Rules” section on page 10-24 to insert an ACE in an ACL.
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:
FWSM/contexta(config)# object-group protocol grp_id
The grp_id is a text string up to 64 characters in length.
The prompt changes to the protocol subcommand mode.
Step 2
(Optional) To add a description, enter the following command:
FWSM/contexta(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:
FWSM/contexta(config-protocol)# protocol-object protocol
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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-5.
For example, to create a protocol group for TCP, UDP, and ICMP, enter the following commands:
FWSM/contexta(config)# object-group protocol tcp_udp_icmp
FWSM/contexta(config-protocol)# protocol-object tcp
FWSM/contexta(config-protocol)# protocol-object udp
FWSM/contexta(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.
To add a network group, follow these steps:
Step 1
To add a network group, enter the following command:
FWSM/contexta(config)# object-group network grp_id
The grp_id is a text string up to 64 characters in length.
The prompt changes to the network subcommand mode.
Step 2
(Optional) To add a description, enter the following command:
FWSM/contexta(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:
FWSM/contexta(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:
FWSM/contexta(config)# object-group network admins
FWSM/contexta(config-network)# description Administrator Addresses
FWSM/contexta(config-network)# network-object host 10.1.1.4
FWSM/contexta(config-network)# network-object host 10.1.1.78
FWSM/contexta(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:
FWSM/contexta(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. Enter tcp-udp
if your service uses both TCP and UDP with the same port number, for example, DNS (port 53).
The prompt changes to the service subcommand mode.
Step 2
(Optional) To add a description, enter the following command:
FWSM/contexta(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:
FWSM/contexta(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-5.
For example, to create service groups that include DNS (TCP/UDP), LDAP (TCP), and RADIUS (UDP),
enter the following commands:
FWSM/contexta(config)# object-group service services1 tcp-udp
FWSM/contexta(config-service)# description DNS Group
FWSM/contexta(config-service)# port-object eq domain
FWSM/contexta(config-service)#
FWSM/contexta(config-service)#
FWSM/contexta(config-service)#
FWSM/contexta(config-service)#
object-group service services2 udp
description RADIUS Group
port-object eq radius
port-object eq radius-acct
FWSM/contexta(config-service)# object-group service services3 tcp
FWSM/contexta(config-service)# description LDAP Group
FWSM/contexta(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:
FWSM/contexta(config)# object-group icmp-type grp_id
The grp_id is a text string up to 64 characters in length.
The prompt changes to the ICMP type subcommand mode.
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Step 2
(Optional) To add a description, enter the following command:
FWSM/contexta(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:
FWSM/contexta(config-icmp-type)# icmp-object icmp_type
See the “ICMP Types” section on page D-9 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:
FWSM/contexta(config)# object-group icmp-type ping
FWSM/contexta(config-service)# description Ping Group
FWSM/contexta(config-icmp-type)# icmp-object echo
FWSM/contexta(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 10-19. 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:
FWSM/contexta(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:
FWSM/contexta(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:
FWSM/contexta(config)# object-group network eng
FWSM/contexta(config-network)# network-object host 10.1.1.5
FWSM/contexta(config-network)# network-object host 10.1.1.9
FWSM/contexta(config-network)# network-object host 10.1.1.89
FWSM/contexta(config-network)# object-group network hr
FWSM/contexta(config-network)# network-object host 10.1.2.8
FWSM/contexta(config-network)# network-object host 10.1.2.12
FWSM/contexta(config-network)# object-group network finance
FWSM/contexta(config-network)# network-object host 10.1.4.89
FWSM/contexta(config-network)# network-object host 10.1.4.100
You then nest all three groups together as follows:
FWSM/contexta(config)# object-group network admin
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FWSM/contexta(config-network)# group-object eng
FWSM/contexta(config-network)# group-object hr
FWSM/contexta(config-network)# group-object finance
You only need to specify the admin object group in your ACE as follows:
FWSM/contexta(config)# access-list ACL_IN extended permit ip object-group admin host
209.165.201.29
Using Object Groups with an Access Control List
To use object groups in an ACL, replace the normal protocol (protocol), network (source_address mask,
etc.), service (operator port), or ICMP type (icmp_type) parameter with object-group grp_id.
For example, to use object groups for all available parameters in the access-list {tcp | udp} command,
enter the following command:
FWSM(config)# access-list acl_name [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]]
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 ACL that does not use object groups restricts several hosts on the inside network
from accessing several web servers. All other traffic is allowed.
FWSM/contexta(config)#
209.165.201.29 eq www
FWSM/contexta(config)#
209.165.201.29 eq www
FWSM/contexta(config)#
209.165.201.29 eq www
FWSM/contexta(config)#
209.165.201.16 eq www
FWSM/contexta(config)#
209.165.201.16 eq www
FWSM/contexta(config)#
209.165.201.16 eq www
FWSM/contexta(config)#
209.165.201.78 eq www
FWSM/contexta(config)#
209.165.201.78 eq www
FWSM/contexta(config)#
209.165.201.78 eq www
FWSM/contexta(config)#
FWSM/contexta(config)#
access-list ACL_IN extended deny tcp host 10.1.1.4 host
access-list ACL_IN extended deny tcp host 10.1.1.78 host
access-list ACL_IN extended deny tcp host 10.1.1.89 host
access-list ACL_IN extended deny tcp host 10.1.1.4 host
access-list ACL_IN extended deny tcp host 10.1.1.78 host
access-list ACL_IN extended deny tcp host 10.1.1.89 host
access-list ACL_IN extended deny tcp host 10.1.1.4 host
access-list ACL_IN extended deny tcp host 10.1.1.78 host
access-list ACL_IN extended deny tcp host 10.1.1.89 host
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:
FWSM/contexta(config)# object-group network denied
FWSM/contexta(config-network)# network-object host 10.1.1.4
FWSM/contexta(config-network)# network-object host 10.1.1.78
FWSM/contexta(config-network)# network-object host 10.1.1.89
FWSM/contexta(config-network)# object-group network web
FWSM/contexta(config-network)# network-object host 209.165.201.29
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FWSM/contexta(config-network)# network-object host 209.165.201.16
FWSM/contexta(config-network)# network-object host 209.165.201.78
FWSM/contexta(config-network)# access-list ACL_IN extended deny tcp object-group denied
object-group web eq www
FWSM/contexta(config)# access-list ACL_IN extended permit ip any any
FWSM/contexta(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:
FWSM/contexta(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 example shows sample output from the show object-group command.
FWSM/contexta# 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 ACL.
•
To remove a specific object group, enter the following command:
FWSM/contexta(config)# no object-group grp_id
•
To remove all object groups of the specified type, enter the following command:
FWSM/contexta(config)# clear object-group [protocol | network | services | icmp-type]
If you do not enter a type, all object groups are removed.
Manually Committing Access Control Lists and Rules
By default, the FWSM automatically commits ACLs as you enter them; the FWSM waits a short period
of time after you last entered an access-list command before committing the ACL. See the “Access
Control List Commit” section on page 10-6 for more information about committing ACLs.
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Adding Remarks to Access Control Lists
You might want to manually commit ACLs if you have one of the following situations:
•
You are running scripts and want to make sure the ACL was committed in its entirety. With
auto-commit, you might commit partial ACLs if you run into memory limitations or other errors in
the middle of the ACL entry.
•
You want to modify an ACL, such as inserting lines, but do not want to disrupt traffic. For example,
with auto-commit, you cannot insert a line into an ACL. You have to create a new ACL (with the
inserted line), and then change the ACL name that is assigned to the interface, causing a brief
disruption. With manual commit, you can remove the ACL (from the configuration; not from
running), enter a modified ACL with the same name, and then commit the ACL. Because the ACL
name is the same, you do not need to change the interface assignment, and there is no disruption of
traffic.
•
You want to add several ACEs to a large ACL at the command line, and do not want the ACL to
commit before you finish making your additions. For example, If you enter a line at the end of a
40,000 line ACL, and you do not enter each additional line within a second of the last line, then the
ACL will commit each time you enter a line. A large ACL can take several minutes to commit, and
you do not want to wait for the ACL to commit before entering the next line.
If you enable manual commit, then you must remember to manually commit any changes you make to
ACLs or other rules, whether the change is an addition or a subtraction. Also, you must manually commit
an ACL before you assign it to an interface (access-group command); the FWSM cannot assign an ACL
to an interface if the ACL does not exist yet.
•
To enable manual commit, or to return to auto-commit mode, enter the following command:
FWSM/contexta(config)# access-list mode {manual-commit | auto-commit}
Auto-commit is the default.
•
To commit ACL changes in manual commit mode, enter the following command:
FWSM/contexta(config)# access-list commit
•
To view which ACLs are committed and which are uncommitted, enter the following command:
FWSM/contexta(config)# show access-list
Adding Remarks to Access Control Lists
You can include remarks about entries in any ACL, including extended, EtherType, and standard ACLs.
The remarks make the ACL easier to understand.
To add a remark after the last access-list command you entered, enter the following command:
FWSM/contexta(config)# access-list acl_id remark text
If you enter the remark before any access-list statements, then the remark is the first line in the ACL.
If you delete an ACL using the no access-list acl_id command, then all the remarks are also removed.
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 ACL in this location.
Entering a dash (-) at the beginning of the remark helps set it apart from ACEs.
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Logging Extended Access Control List Activity
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(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
Logging Extended Access Control List Activity
This section describes how to configure ACL logging, and includes the following topics:
•
Access Control List Logging Overview, page 10-26
•
Configuring Logging for an Access Control Entry, page 10-27
•
Managing Deny Flows, page 10-28
Access Control List Logging Overview
By default, when traffic is denied by an extended ACE, the FWSM generates system message 106023
for each denied packet, in the following form:
%FWSM-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
If the FWSM 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 ACL generate logging messages; the implicit deny at the end of the ACL does not
generate a message. If you want all denied traffic to generate messages, add the implicit ACE manually
to the end of the ACL, as follows:
FWSM/contexta(config)# access-list TEST deny ip any any log
The log options at the end of the extended access-list command allow 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:
%FWSM-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 FWSM creates a
flow entry to track the number of packets received within a specific interval. The FWSM 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 FWSM resets the hit count to 0. If no packets match the ACE
during an interval, the FWSM deletes the flow entry.
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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 10-28 to limit the number of logging flows.
Permitted packets that belong to established connections do not need to be checked against ACLs; 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 Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module System
Messages Guide 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:
FWSM/contexta(config)# access-list acl_name [extended] {deny | permit}...[log [[level]
[interval secs] | disable | default]]
See the “Adding an Extended Access Control List” section on page 10-13 for complete access-list
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.
•
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 ACL logging.
default—Enables logging to message 106023. This setting is the same as having no log option.
For example, you configure the following ACL:
FWSM/contexta(config)#
600
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
access-list outside-acl permit ip host 1.1.1.1 any log 7 interval
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 FWSM generates the following system
message:
%FWSM-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 ACL, 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:
%FWSM-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, then the FWSM generates the following system message:
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%FWSM-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:
%FWSM-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 FWSM creates a
flow entry to track the number of packets received within a specific interval. The FWSM has a maximum
of 32K 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 FWSM 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 FWSM does not create a new deny flow for logging
until the existing flows expire.
For example, if someone initiates a denial of service (DoS) attack, the FWSM 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 FWSM issues system message 106100:
%FWSM-1-106101: The number of ACL log deny-flows has reached limit (number).
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 FWSM stops logging,
enter the following command:
FWSM/contexta(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:
FWSM/contexta(config)# access-list alert-interval secs
The seconds are between 1 and 3600. 300 is the default.
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11
Allowing Remote Management
This chapter describes how to allow remote access to the Firewall Services Module (FWSM) CLI and
how to allow ICMP to and from the FWSM.
Caution
Management access to the FWSM using Telnet, SSH, or HTTPS might cause a degradation in
performance depending on the commands that you execute during the session. For example, if there are
50,000 current connections and you enter the show conn command, the CPU utilization is higher than
if you do not enter the command. We recommend that you avoid executing commands on the FWSM
when high network performance is critical.
This chapter includes the following sections:
Note
•
Allowing Telnet, page 11-1
•
Allowing SSH, page 11-2
•
Allowing HTTPS for PDM, page 11-4
•
Allowing a VPN Management Connection, page 11-5
•
Allowing ICMP to and from the FWSM, page 11-10
To “session” into the FWSM from the switch, see the “Sessioning and Logging into the Firewall Services
Module” section on page 3-1.
Allowing Telnet
The FWSM allows Telnet connections to the FWSM for management purposes. You cannot use Telnet
to the lowest security interface unless you use Telnet inside an IPSec tunnel (See the “Allowing a VPN
Management Connection” section on page 11-5).
You can control the number of Telnet sessions allowed per context using resource classes (see the
“Configuring a Class” section on page 5-14). The FWSM allows a maximum of 5 concurrent Telnet
connections per context, if available, with a maximum of 100 connections divided between all contexts.
See the “Rule Limits” section on page A-5 for information about the maximum number of Telnet rules
allowed for the entire system.
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Allowing SSH
To configure Telnet access to the FWSM, follow these steps:
Step 1
To identify the IP addresses from which the FWSM accepts connections, enter the following command
for each address or subnet:
FWSM/contexta(config)# telnet source_IP_address mask source_interface
The source_interface cannot be the lowest security interface unless you use Telnet inside an IPSec tunnel
(See the “Allowing a VPN Management Connection” section on page 11-5).
For example, you must configure at least two interfaces so the FWSM can determine the lowest security
interface. If you configure a single interface (for the admin context, for example), then that interface is
both the highest and the lowest security interface and cannot be used. Similarly, if all interfaces are on
the same security level, you cannot use Telnet.
Step 2
(Optional) To set the duration for how long a Telnet session can be idle before the FWSM disconnects
the session, enter the following command:
FWSM/contexta(config)# telnet timeout minutes
Set the timeout from 1 to 1440 minutes. The default is 5 minutes. The default duration is too short in
most cases and should be increased until all pre-production testing and troubleshooting has been
completed.
For example, to let a host on the inside interface with an address of 192.168.1.2 access the FWSM, enter
the following command:
FWSM/contexta(config)# telnet 192.168.1.2 255.255.255.255 inside
FWSM/contexta(config)# telnet timeout 30
To allow all users on the 192.168.3.0 network to access the FWSM on the inside interface, enter the
following command:
FWSM/contexta(config)# telnet 192.168.3.0 255.255.255.0 inside
Allowing SSH
The FWSM allows SSH connections to the FWSM for management purposes. You can control the
number of SSH sessions allowed per context using resource classes (see the “Configuring a Class”
section on page 5-14). The FWSM allows a maximum of 5 concurrent SSH connections per context, if
available, with a maximum of 100 connections divided between all contexts. See the “Rule Limits”
section on page A-5 for information about the maximum number of SSH rules allowed for the entire
system.
SSH is an application running on top of a reliable transport layer, such as TCP/IP, that provides strong
authentication and encryption capabilities. FWSM supports the SSH remote shell functionality provided
in SSH Version 1 and supports DES and 3DES ciphers.
Note
SSH v1.x and v2 are entirely different protocols and are not compatible. Make sure that you download
a client that supports SSH v1.x.
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Allowing SSH
This section includes the following topics:
•
Configuring SSH Access, page 11-3
•
Using an SSH Client, page 11-4
Configuring SSH Access
To configure SSH access to the FWSM, follow these steps:
Step 1
To generate an RSA key pair, which is required for SSH, enter the following command:
FWSM/contexta(config)# ca generate rsa key modulus
The modulus (in bits) is 512, 768, 1024, or 2048. The larger the key modulus size you specify, the longer
it takes to generate an RSA. We recommend a value of 768.
Before you generate the key, you should set the host name and the domain name according to the
“Setting the Host Name” section on page 6-4 and the “Setting the Domain Name” section on page 6-5.
These settings are used in the key.
Step 2
To save the RSA keys to persistent Flash memory, enter the following command:
FWSM/contexta(config)# ca save all
Step 3
To identify the IP addresses from which the FWSM accepts connections, enter the following command
for each address or subnet:
FWSM/contexta(config)# ssh source_IP_address mask source_interface
The FWSM accepts SSH connections from all interfaces, including the lowest security one.
Step 4
(Optional) To set the duration for how long an SSH session can be idle before the FWSM disconnects
the session, enter the following command:
FWSM/contexta(config)# ssh timeout minutes
Set the timeout from 1 to 60 minutes. The default is 5 minutes. The default duration is too short in most
cases and should be increased until all pre-production testing and troubleshooting has been completed.
For example, to generate RSA keys and let a host on the inside interface with an address of 192.168.1.2
access the FWSM, enter the following command:
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
ca generate rsa key 1024
ca save all
ssh 192.168.1.2 255.255.255.255 inside
ssh 192.168.1.2 255.255.255.255 inside
ssh timeout 30
To allow all users on the 192.168.3.0 network to access the FWSM on the inside interface, the following
command:
FWSM/contexta(config)# ssh 192.168.3.0 255.255.255.0 inside
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Allowing HTTPS for PDM
Using an SSH Client
To gain access to the FWSM console using SSH, at the SSH client enter the username pix and enter the
login password set by the password command (see the “Changing the Login Password” section on
page 6-2). For individual logins, see the “Configuring Authentication for CLI Access” section on
page 12-8.
When starting an SSH session, a dot (.) displays on the FWSM console before the SSH user
authentication prompt appears, as follows:
FWSM/contexta(config)# .
The display of the dot does not affect the functionality of SSH. The dot appears at the console when
generating a server key or decrypting a message using private keys during SSH key exchange before user
authentication occurs. These tasks can take up to two minutes or longer. The dot is a progress indicator
that verifies that the FWSM is busy and has not hung.
Allowing HTTPS for PDM
To use PDM, you need to enable the HTTPS server and allow HTTPS connections to the FWSM. All of
these tasks are completed if you use the setup command. This section describes how to manually
configure PDM access.
The FWSM allows up to 32 PDM sessions for the entire modul, and it allows a maximum of 5 concurrent
HTTPS connections per context, which can be configurable. See the “Rule Limits” section on page A-5
for information about the maximum number of HTTPS rules allowed for the entire system.
To configure PDM access, follow these steps:
Step 1
To generate an RSA key pair, which is required for HTTPS, enter the following command:
FWSM/contexta(config)# ca generate rsa key modulus
The modulus (in bits) is 512, 768, 1024, or 2048. The larger the key modulus size you specify, the longer
it takes to generate an RSA. We recommend a value of 768.
Before you generate the key, you should set the host name and the domain name according to the
“Setting the Host Name” section on page 6-4 and the “Setting the Domain Name” section on page 6-5.
These settings are used in the key.
Step 2
To save the RSA keys to persistent Flash memory, enter the following command:
FWSM/contexta(config)# ca save all
Step 3
To identify the IP addresses from which the FWSM accepts HTTPS connections, enter the following
command for each address or subnet:
FWSM/contexta(config)# http source_IP_address mask source_interface
Step 4
To enable the HTTPS server, enter the following command:
FWSM/contexta(config)# http server enable
Step 5
To enable PDM metrics history, enter the following command:
FWSM/contexta(config)# pdm history enable
If you do not enable PDM metrics history, you can view real-time data only and not historical data. This
step is optional.
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Allowing a VPN Management Connection
For example, to enable the HTTPS server and let a host on the inside interface with an address of
192.168.1.2 access PDM, enter the following commands:
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
ca generate rsa key 1024
ca save all
http server enable
pdm history enable
http 192.168.1.2 255.255.255.255 inside
To allow all users on the 192.168.3.0 network to access PDM on the inside interface, enter the following
command:
FWSM/contexta(config)# http 192.168.3.0 255.255.255.0 inside
Allowing a VPN Management Connection
The FWSM supports IPSec for management access. An IPSec virtual private network (VPN) ensures that
IP packets can safely travel over insecure networks such as the Internet. All communication between two
VPN peers occurs over a secure tunnel, which means the packets are encrypted and authenticated by the
peers.
The FWSM can connect to another VPN concentrator, such as a Cisco PIX firewall or a Cisco IOS router,
using a site-to-site tunnel. You specify the peer networks that can communicate over the tunnel. In the
case of the FWSM, the only address available on the FWSM end of the tunnel is the interface itself.
The FWSM can also accept connections from VPN clients, either hosts running the Cisco VPN client,
or VPN concentrators such as the Cisco PIX firewall or Cisco IOS router running the Easy VPN client.
Unlike a site-to-site tunnel, you do not know in advance the IP address of the client. Instead, you rely on
client authentication.
The FWSM can support 5 concurrent IPSec connections, with a maximum of 10 concurrent connections
divided between all contexts. You can control the number of IPSec sessions allowed per context using
resource classes. (See the “Configuring a Class” section on page 5-14.)
This section describes the following topics:
•
Configuring Basic Settings for All Tunnels, page 11-5
•
Configuring VPN Client Access, page 11-7
•
Configuring a Site-to-Site Tunnel, page 11-9
Configuring Basic Settings for All Tunnels
The following steps are required for both VPN client access and for site-to-site tunnels, and include
setting the Internet Key Exchange (IKE) policy (IKE is part of the Internet Security Association and Key
Management Protocol (ISAKMP)) and the IPSec transforms:
Step 1
To set the IKE encryption algorithm, enter the following command:
FWSM/contexta(config)# isakmp policy priority encryption {des | 3des}
The 3des keyword is more secure than des.
You can have multiple IKE policies. The FWSM tries each policy in order of the priority until the policy
matches the peer policy. The priority can be an integer from 1 to 65,534, with 1 being the highest priority
and 65,534 the lowest. Use this same priority number for the following isakmp commands.
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Step 2
To set the Diffie-Hellman group used for key exchange, enter the following command:
FWSM/contexta(config)# isakmp policy priority group {1 | 2}
Group 1 is 768 bits, and Group 2 is 1024 bits (and therefore more secure).
Step 3
To set the authentication algorithm, enter the following command:
FWSM/contexta(config)# isakmp policy priority hash {md5 | sha}
The sha keyword is more secure than md5.
Step 4
To set the IKE authentication method as a shared key, enter the following command:
FWSM/contexta(config)# isakmp policy priority authentication pre-share
You can alternatively use certificates instead of a shared key by specifying the rsa-sig option. See the
Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Command
Reference for more information about this method.
Step 5
To enable IKE on the tunnel interface, enter the following command:
FWSM/contexta(config)# isakmp enable interface_name
Step 6
To set the authentication and encryption methods used for IPSec tunnels in a transform set, enter the
following command:
FWSM/contexta(config)# crypto ipsec transform-set transform_name {[ah-md5-hmac |
ah-sha-hmac] | [esp-md5-hmac | esp-sha-hmac]} {esp-des | esp-3des}
You refer to this transform set when you configure the VPN client group or a site-to-site tunnel.
You can refer to up to 6 transform sets for the tunnel, and the sets are checked in order until the
transforms match.
The authentication and encryption algorithms of this transform typically match the IKE policy
(isakmp policy commands). For site-to-site tunnels, this transform must match the peer transform.
Typically, you need to specify one authentication option and one encryption option.
Authentication options include the following (from most secure to least secure):
•
ah-sha-hmac
•
ah-md5-hmac
•
esp-sha-hmac
•
esp-md5-hmac
Encryption options include the following (from most secure to least secure):
•
esp-3des
•
esp-des
Note
esp-null (no encryption) is for testing purposes only.
Although you can specify authentication alone, or encryption alone, these methods are not secure. You
can also specify two authentication options, but this method does not increase security and also slows
down the FWSM because each packet is authenticated two times.
For example, to configure the IKE policy and the IPSec transform sets, enter the following commands:
FWSM/contexta(config)# isakmp policy 1 authentication pre-share
FWSM/contexta(config)# isakmp policy 1 encryption 3des
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FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
isakmp
isakmp
isakmp
crypto
crypto
policy 1 group 2
policy 1 hash sha
enable outside
ipsec transform-set vpn_client esp-3des esp-sha-hmac
ipsec transform-set site_to_site esp-3des ah-sha-hmac
Configuring VPN Client Access
A host with an installed version of the Cisco VPN Client can connect to the FWSM for management
purposes over a public network, such as the Internet.
To allow remote clients to connect to the FWSM for management access, first configure basic VPN
settings (see “Configuring Basic Settings for All Tunnels”), and then follow these steps:
Step 1
To specify the transform sets (defined in the “Configuring Basic Settings for All Tunnels” section on
page 11-5) allowed for client tunnels, enter the following command:
FWSM/contexta(config)# crypto dynamic-map dynamic_map_name priority set transform-set
transform_set1 [transform_set2] [...]
List multiple transform sets in order of priority (highest priority first).
This dynamic crypto map allows unknown IP addresses to connect to the FWSM.
The dynamic-map name is used in Step 2.
The priority specifies the order in which multiple commands are evaluated. If you have a command that
specifies one set of transforms, and another that specifies others, then the priority number determines
the command that is evaluated first.
Step 2
To assign the dynamic crypto map (from Step 1) to a static tunnel, enter the following command:
FWSM/contexta(config)# crypto map crypto_map_name priority ipsec-isakmp dynamic
dynamic_map_name
Step 3
To specify the interface at which you want the client tunnels to terminate, enter the following command:
FWSM/contexta(config)# crypto map crypto_map_name interface interface_name
You can apply only one crypto map name to an interface, so if you want to terminate both a site-to-site
tunnel and VPN clients on the same interface, they need to share the same crypto map name.
Step 4
To specify the AAA server or the local user database that provides user authentication when a client
connects to the FWSM, enter the following command:
FWSM/contexta(config)# crypto map crypto_map_name client authentication
{LOCAL | aaa_server_name [LOCAL]}
You must first configure the server name according to the “Identifying a AAA Server” section on
page 12-6 or the local database according to the “Configuring the Local Database” section on page 12-6.
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Step 5
To specify the range of addresses that VPN clients use on the FWSM enter the following command:
FWSM/contexta(config)# ip local pool pool_name ip_address[-ip_address]
All tunneled packets from the client use one of these addresses as the source address.
Step 6
To specify the traffic that is destined for the FWSM, so you can tunnel only that traffic according to the
vpngroup split-tunnel command in Step 8, enter the following command:
FWSM/contexta(config)# access-list acl_name [extended] permit {protocol} host
fwsm_interface_address pool_addresses mask
This ACL identifies traffic from the local pool (see Step 5) destined for the FWSM interface. See the
“Adding an Extended Access Control List” section on page 10-13 for more information about ACLs.
Step 7
To assign the VPN address pool to a VPN group, enter the following command:
FWSM/contexta(config)# vpngroup group_name address-pool pool_name
This group specifies VPN characteristics for connecting clients. When a client connects the FWSM, they
need to enter the VPN group name as well as the VPN group password in Step 9.
Step 8
To specify that only traffic destined for the FWSM is tunneled, enter the following command:
FWSM/contexta(config)# vpngroup group_name split-tunnel acl_name
This command is required.
Step 9
To set the VPN group password, enter the following command:
FWSM/contexta(config)# vpngroup group_name password password
Step 10
To allow Telnet or SSH access, see the “Allowing Telnet” section on page 11-1 and the “Allowing SSH”
section on page 11-2.
Specify the VPN pool addresses in the telnet and ssh commands.
For example, the following commands allow VPN clients to use Telnet on the outside interface
(209.165.200.225). The user authentication is the local database, so users with the VPN group name and
password, as well as the username “admin” and the password “passw0rd” can connect to the FWSM.
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
10.1.1.1
FWSM/contexta(config)#
10.1.1.2
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
isakmp policy 1 authentication pre-share
isakmp policy 1 encryption 3des
isakmp policy 1 group 2
isakmp policy 1 hash sha
isakmp enable outside
username admin password passw0rd
crypto ipsec transform-set vpn esp-3des esp-sha-hmac
crypto dynamic-map vpn_client 1 set transform-set vpn
crypto map telnet_tunnel 1 ipsec-isakmp dynamic vpn_client
crypto map telnet_tunnel interface outside
crypto map telnet_tunnel client authentication LOCAL
ip local pool client_pool 10.1.1.1-10.1.1.2
access-list VPN_SPLIT extended permit ip host 209.165.200.225 host
access-list VPN_SPLIT extended permit ip host 209.165.200.225 host
vpngroup admin address-pool client_pool
vpngroup admin split-tunnel VPN_SPLIT
vpngroup admin password $ecure23
telnet 10.1.1.1 255.255.255.255 outside
telnet 10.1.1.2 255.255.255.255 outside
telnet timeout 30
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Configuring a Site-to-Site Tunnel
To configure a site-to-site tunnel, first configure basic VPN settings (see “Configuring Basic Settings
for All Tunnels”), and then follow these steps:
Step 1
To set the shared key used by both peers, enter the following command:
FWSM/contexta(config)# isakmp key keystring address peer-address
Step 2
To identify the traffic allowed to go over the tunnel, enter the following command:
FWSM/contexta(config)# access-list acl_name [extended] {deny | permit} {protocol} host
fwsm_interface_address dest_address mask
For the destination address, specify the addresses that are allowed to access the FWSM.
See the “Adding an Extended Access Control List” section on page 10-13 for more information about
ACLs.
Step 3
To create an IPSec tunnel, enter the following command:
FWSM/contexta(config)# crypto map crypto_map_name priority ipsec-isakmp
All tunnel attributes are identified by the same crypto map name.
The priority specifies the order in which multiple commands are evaluated. If you have a command for
this crypto map name that specifies ipsec-isakmp, and another that specifies ipsec-isakmp dynamic
(for VPN client connections), then the priority number determines the command that is evaluated first.
Step 4
To assign the ACL from Step 2 to this tunnel, enter the following command:
FWSM/contexta(config)# crypto map crypto_map_name priority match address acl_name
Step 5
To specify the remote peer on which this tunnel terminates, enter the following command:
FWSM/contexta(config)# crypto map crypto_map_name priority set peer ip_address
Step 6
To specify the transform sets for this tunnel (defined in the “Configuring Basic Settings for All Tunnels”
section on page 11-5), enter the following command:
FWSM/contexta(config)# crypto map crypto_map_name priority set transform-set
transform_set1 [transform_set2] [...]
List multiple transform sets in order of priority (highest priority first). You can specify up to six
transform sets.
Step 7
To specify the interface at which you want this tunnel to terminate, enter the following command:
FWSM/contexta(config)# crypto map crypto_map_name interface interface_name
You can apply only one crypto map name to an interface, so if you want to terminate both a site-to-site
tunnel and VPN clients on the same interface, they need to share the same crypto map name.
This command must be entered after all other crypto map commands. If you change any crypto map
settings, remove this command with the no prefix, and reenter it.
Step 8
To allow Telnet or SSH access, see the “Allowing Telnet” section on page 11-1 and the “Allowing SSH”
section on page 11-2.
For example, the following commands allow hosts connected to the peer router (209.165.202.129) to use
Telnet on the outside interface (209.165.200.225).
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FWSM/contexta(config)# isakmp policy 1 authentication pre-share
FWSM/contexta(config)# isakmp policy 1 encryption 3des
FWSM/contexta(config)# isakmp policy 1 group 2
FWSM/contexta(config)# isakmp policy 1 hash sha
FWSM/contexta(config)# isakmp enable outside
FWSM/contexta(config)# crypto ipsec transform-set vpn esp-3des esp-sha-hmac
FWSM/contexta(config)# isakmp key 7mfi02lirotn address 209.165.200.223
FWSM/contexta(config)# access-list TUNNEL extended permit ip host 209.165.200.225
209.165.201.0 255.255.255.224
FWSM/contexta(config)# crypto map telnet_tunnel 2 ipsec-isakmp
FWSM/contexta(config)# crypto map telnet_tunnel 1 match address TUNNEL
FWSM/contexta(config)# crypto map telnet_tunnel 1 set peer 209.165.202.129
FWSM/contexta(config)# crypto map telnet_tunnel 1 set transform-set vpn
FWSM/contexta(config)# crypto map telnet_tunnel interface outside
FWSM/contexta(config)# telnet 209.165.201.0 255.255.255.224 outside
FWSM/contexta(config)# telnet timeout 30
Allowing ICMP to and from the FWSM
By default, ICMP (including ping) is not allowed to an FWSM interface (or through the FWSM. To allow
ICMP through the FWSM, see Chapter 10, “Controlling Network Access with Access Control Lists.”).
ICMP is an important tool for testing your network connectivity; however, it can also be used to attack
the FWSM or your network. We recommend allowing ICMP during your initial testing, but then
disallowing it during normal operation.
See the “Rule Limits” section on page A-5 for information about the maximum number of ICMP rules
allowed for the entire system.
To permit or deny address(es) to reach an FWSM interface with ICMP (either from a host to the FWSM,
or from the FWSM to a host, which requires the ICMP reply to be allowed back), enter the following
command:
FWSM/contexta(config)# icmp {permit | deny} {host ip_address | ip_address mask | any}
[icmp_type] interface_name
If you do not specify an icmp_type, all types are identified. You can enter the number or the name. To
control ping, specify echo-reply (0) (FWSM to host) or echo (8) (host to FWSM). See the “ICMP
Types” section on page D-9 for a list of ICMP types.
Like ACLs, the FWSM matches a packet to each icmp statement in order. You should use specific
statements first, and general statements later. There is an implicit deny at the end. For example, if you
allow all addresses first, then deny a specific address after, then that address will be unintentionally
allowed because it matched the first statement.
Note
If you only want to allow the FWSM to ping a host (and thus allow the echo reply back to the interface),
and not allow hosts to ping the FWSM, you can enable the ICMP inspection engine instead of entering
the command above. See the “ICMP Inspection Engine” section on page 13-10.
For example, to allow all hosts except the one at 10.1.1.15 to use ICMP to the inside interface, enter the
following commands:
FWSM/contexta(config)# icmp deny host 10.1.1.15 inside
FWSM/contexta(config)# icmp permit any inside
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To allow the host at 10.1.1.15 to use only ping to the inside interface, enter the following commands:
FWSM/contexta(config)# icmp permit host 10.1.1.15 inside
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12
Configuring AAA
Authentication, authorization, and accounting (AAA) tell the Firewall Services Module (FWSM) who
the user is, what the user can do, and what the user did. This chapter contains the following sections:
Note
•
AAA Overview, page 12-1
•
Configuring the Local Database, page 12-6
•
Identifying a AAA Server, page 12-6
•
Configuring Authentication for CLI Access, page 12-8
•
Configuring Authentication to Access Privileged Mode, page 12-8
•
Configuring Command Authorization, page 12-10
•
Viewing the Current Logged-In User, page 12-18
•
Recovering from a Lockout, page 12-19
•
Configuring Authentication for Network Access, page 12-20
•
Configuring Authorization for Network Access, page 12-23
•
Configuring Accounting for Network Access, page 12-27
See the “Rule Limits” section on page A-5 for information about the maximum number of AAA rules
that are allowed for the entire system.
AAA Overview
AAA provides an extra level of protection and control for user access than using ACLs alone. For
example, you can create an ACL 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 do not know their IP addresses, you
can enable AAA to allow only authenticated and/or authorized users to make it through the FWSM. (The
Telnet server has its own authentication; the FWSM 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:
•
AAA Performance, page 12-2
•
About Authentication, page 12-2
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•
About Authorization, page 12-2
•
About Accounting, page 12-3
•
AAA Server and Local Database Support, page 12-4
AAA Performance
The FWSM uses “cut-through proxy” to significantly speed up 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 Open System Interconnection (OSI) model. The FWSM cut-through proxy
challenges a user initially at the application layer and then authenticates against standard Remote
Authentication Dial-In User Service (RADIUS), Terminal Access Controller Access Control System
Plus (TACACS+), or a local database. After the FWSM checks the policy, the FWSM shifts the session
flow, and all traffic flows directly and quickly between the two parties while maintaining session state
information.
About Authentication
Authentication lets you control access by requiring a valid username and password. You can configure
the FWSM to authenticate the following items:
•
All administrative connections to the FWSM including the following sessions:
– Telnet
– SSH
– PDM (using HTTPS)
– VPN management access (see the “Configuring VPN Client Access” section on page 11-7 for
more information about using AAA with VPN)
•
The enable command
•
Network access through the FWSM
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 Catalyst 6500 Series Switch and
Cisco 7600 Series Router Firewall Services Module Command Reference for timeout values.) For
example, if you configure the FWSM to authenticate Telnet and FTP, and a user first successfully
authenticates for Telnet, then as long as the session exists, the user does not also have to authenticate for
FTP. See the “FWSM/contexta(config)# aaa accounting match SERVER_AUTH inside AuthOutbound”
section on page 12-27 for more information about authentication sessions.
About Authorization
Authorization lets you control access per user after you authenticate with a valid username and
password. You can configure the FWSM to authorize the following items:
•
Management commands
•
Network access through the FWSM
Authorization lets you control which services and commands are available to an individual user.
Authentication alone provides the same access to services for all authenticated users.
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AAA Overview
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 to access
any server on the outside network and then limit the outside servers that a particular user can access using
authorization.
The FWSM caches the first 16 authorization requests per user, so if the user accesses the same services
during the current authentication session, the FWSM does not resend the request to the authorization
server.
About Accounting
Accounting lets you keep track of traffic that passes through the FWSM. 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, the AAA client
messages and username, the number of bytes that pass through the FWSM for the session, the service
used, and the duration of each session.
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AAA Server and Local Database Support
The FWSM supports AAA servers and a local database that is stored on the FWSM. Each server type
and local database provides different functionality (see Table 12-1).
Table 12-1 AAA Server and Local Database Support
Server/Database Type Functionality
Description
RADIUS
User authentication for CLI access
When a user attempts to access the FWSM for Telnet, SSH,
or HTTP, the FWSM consults the RADIUS server for the
username and password.
User authentication for the enable
command
When a user attempts to access the enable command, the
FWSM consults the RADIUS server for the username and
password.
User authentication for network
access
When a user attempts to access networks through the FWSM,
and the traffic matches an authentication statement, the
FWSM consults the RADIUS server for the username and
password.
User authorization for network access This user authorization occurs automatically when you
using downloaded ACLs per user
configure authentication, but you must configure the
(dynamic ACLs)
RADIUS server to support it. When the user authenticates on
the FWSM, the RADIUS server sends a dynamic ACL to the
FWSM. The user’s access to a given service is either
permitted or denied by the ACL. The FWSM deletes the ACL
when the authentication session expires.
User authorization for network access This user authorization occurs implicitly when you configure
authentication, but you must configure the RADIUS server to
using a downloaded ACL name per
support it. When the user authenticates on the FWSM, the
user
RADIUS server sends a name of an ACL that is already
defined on the FWSM. The user’s access to a given service is
either permitted or denied by the ACL. You can specify the
same ACL for multiple users.
VPN client authentication
When you configure VPN management access using the
VPN client, you can use a RADIUS server to authenticate the
client. (See the “Configuring VPN Client Access” section on
page 11-7 for more information.)
Accounting for network access per
user or IP address
You can configure the FWSM to send accounting information
to the RADIUS server about any traffic that passes through
the FWSM.
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Table 12-1 AAA Server and Local Database Support (continued)
Server/Database Type Functionality
Description
TACACS+
User authentication for CLI access
When a user attempts to access the FWSM for Telnet, SSH,
or HTTP, the FWSM consults the TACACS+ server for the
username and password.
User authentication for the enable
command
When a user attempts to access the enable command, the
FWSM consults the TACACS+ server for the username and
password.
User authentication for network
access
When a user attempts to access networks through the FWSM,
and the traffic matches an authentication statement, the
FWSM consults the TACACS+ server for the username and
password.
User authorization for network access When a user matches an authorization statement on the
FWSM after authenticating, the FWSM consults the
TACACS+ server for the user’s access privileges.
Local database1
User authorization for management
commands.
On the TACACS+ server, configure the commands that a user
or group can use after they authenticate for CLI access. Every
command that a user enters at the CLI is checked with the
TACACS+ server.
VPN client authentication
When you configure VPN management access using the
VPN client, you can use a TACACS+ server to authenticate
the client. (See the “Configuring VPN Client Access” section
on page 11-7 for more information.)
Accounting for network access per
user or IP address
You can configure the FWSM to send accounting information
to the TACACS+ server about any traffic that passes through
the FWSM.
User authentication for CLI access
When a user attempts to access the FWSM for Telnet, SSH,
or HTTP, the FWSM consults the local user database for the
username and password.
User authentication for the enable or When a user attempts to access the enable or login command,
login command
the FWSM consults the local user database for the username
and password. You do not need to configure login user
authentication; it is on by default.
User authorization for management
commands.
When a user authenticates with the enable command (or logs
in with the login command), the FWSM places that user in the
privilege level defined by the local database. You can
configure each command to belong to privilege level between
0 and 15 on the FWSM.
VPN client authentication
When you configure VPN management access using the
VPN client, you can use the local database to authenticate the
client. (See the “Configuring VPN Client Access” section on
page 11-7 for more information.)
1. The local database can act as a fallback method for each of these functions if the AAA server is unavailable.
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Configuring the Local Database
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, or for VPN client
authentication for management access. You cannot use the local database for network access
authentication or authorization. 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 users to the local database who can gain access to the CLI and whom you do not want to enter
privileged mode, you should enable command authorization. (See the “Configuring Local Command
Authorization” section on page 12-10.) Without command authorization, users can access privileged
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 the user will not be able
to 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, enter the following command:
FWSM/contexta(config)# username username {nopassword | password password}
[privilege level]
Define the following parameters:
•
username—A string from 4 to 15 characters long.
•
password—A string from 3 to 16 characters long.
•
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.
For example, the following command assigns a privilege level of 15 to the admin user account:
FWSM/contexta(config)# username admin password passw0rd privilege 15
The following command creates a user account with no password:
FWSM/contexta(config)# username john.doe nopassword
Identifying a AAA Server
If you want to use an external AAA server (RADIUS or TACACS+) for authentication, authorization, or
accounting, you must first add one or more servers to a server group on the FWSM. You identify this
server group name when you add AAA rules. Each server group consists of only one type of server,
RADIUS or TACACS+. For multiple context mode, you can configure up to 4 servers in a maximum of
4 groups. In single mode, you can configure 16 servers in a maximum of 14 server groups.
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The FWSM contacts the first server in the group. If that server is unavailable, the FWSM contacts the
next server in the group, if configured. If all servers in the group are unavailable, the FWSM 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 FWSM continues to try the AAA servers.
To add a server to a group, follow these steps:
Step 1
To identify the server group name and the protocol, enter the following command:
FWSM/contexta(config)# aaa-server server_group protocol {radius | tacacs+}
Step 2
To identify the maximum number of requests to send to a AAA server in the group before trying the next
server, enter the following command:
FWSM/contexta(config)# aaa-server server_group max-failed-attempts number
The number can be between 1 and 5 times. The default is 3.
If you configured a fallback method using the local database (for management access only; see the
“Configuring Authentication for CLI Access” section on page 12-8, the “Configuring Authentication to
Access Privileged Mode” section on page 12-8, and the “Configuring TACACS+ Command
Authorization” section on page 12-13 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 aaa-server
deadtime command below.
If you do not have a fallback method, the FWSM continues to retry the servers in the group.
Step 3
If you configured a fallback method, identify the amount of time the server group is marked as
unresponsive after all communications attempts fail by entering the following command:
FWSM/contexta(config)# aaa-server server_group deadtime minutes
Step 4
To add a server to the group, enter the following command:
FWSM/contexta(config)# aaa-server server_group (interface_name) host server_ip [key]
[timeout seconds]
The key is a case-sensitive, alphanumeric keyword of up to 127 characters that is the same value as the
key on the server. Spaces are not permitted in the key, but other special characters are permitted. The key
is used between the FWSM and server for encrypting data between them.
For example, to add one TACACS+ group with one primary and one backup server, and one RADIUS
group with a single server, enter the following commands:
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
aaa-server
aaa-server
aaa-server
aaa-server
aaa-server
aaa-server
aaa-server
AuthInbound protocol tacacs+
AuthInbound max-failed-attempts 2
AuthInbound deadtime 20
AuthInbound (inside) host 10.1.1.1 TheUauthKey
AuthInbound (inside) host 10.1.1.2 TheUauthKey2
AuthOutbound protocol radius
AuthOutbound (inside) host 10.1.1.3
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Configuring Authentication for CLI Access
Configuring Authentication for CLI Access
If you enable CLI authentication, the FWSM prompts you for your username and password to log in.
After you enter your information, you have access to unprivileged mode.
To enter privileged mode, enter the enable command or the login command (if you are using the local
database only).
If you configure enable authentication (see the “Configuring Authentication to Access Privileged Mode”
section on page 12-8), the FWSM prompts you for your username and password. If you do not configure
enable authentication, enter the system enable password when you enter the enable command (set by the
enable password command). However, if you do not use enable authentication, after you enter the
enable command, you are no longer logged in as a particular user. To maintain your username, use
enable authentication.
For authentication using the local database, you can use the login command, which maintains the
username but requires no configuration to turn on authentication.
Note
Before the FWSM can authenticate a Telnet, SSH, or HTTP user, you must first configure access to the
FWSM using the telnet, ssh, and http commands. These commands identify the IP addresses that are
allowed to communicate with the FWSM. See Chapter 11, “Allowing Remote Management.” The only
exception is when you session from the switch to the FWSM; this Telnet session is always allowed.
However, you cannot authenticate the system session because the system configuration does not contain
any aaa commands.
To authenticate users who access the CLI, enter the following command:
FWSM/contexta(config)# aaa authentication {telnet | ssh | http} console {LOCAL |
server_group [LOCAL]}
The http keyword authenticates the PDM client that accesses the FWSM using HTTPS.
If you use a TACACS+ or RADIUS server group for authentication, you can configure the FWSM to use
the local database as a fallback method if the AAA server is unavailable. Specify the server group name
followed by LOCAL (LOCAL is case sensitive). We recommend that you use the same username and
password in the local database as the AAA server because the FWSM prompt does not give any
indication which method is being used.
You can alternatively use the local database as your main method of authentication (with no fallback) by
entering LOCAL alone.
Configuring Authentication to Access Privileged Mode
You can configure the FWSM to authenticate users with a AAA server or the local database when they
enter the enable command. Alternatively, users are automatically authenticated with the local database
when they enter the login command, which also accesses privileged mode depending on the user level
in the local database. See the following sections for information about these methods:
•
Configuring Authentication for the enable Command, page 12-9
•
Authenticating Users Using the login Command, page 12-9
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Configuring Authentication to Access Privileged Mode
Configuring Authentication for the enable Command
You can configure the FWSM to authenticate users when they enter the enable command. If you do not
authenticate the enable command, when you enter enable, the FWSM prompts for the system enable
password (set by the enable password command), and you are no longer logged in as a particular user.
Enable authentication maintains the username. This feature is particularly useful when you perform
command authorization, where usernames are important to determine the commands a user can enter.
To authenticate users who enter the enable command, enter the following command:
FWSM/contexta(config)# aaa authentication enable console {LOCAL | server_group [LOCAL]}
The user is prompted for the username and password.
If you use a TACACS+ or RADIUS server group for authentication, you can configure the FWSM to use
the local database as a fallback method if the AAA server is unavailable. Specify the server group name
followed by LOCAL (LOCAL is case sensitive). We recommend that you use the same username and
password in the local database as the AAA server because the FWSM prompt does not give any
indication which method is being used.
You can alternatively use the local database as your main method of authentication (with no fallback) by
entering LOCAL alone.
Authenticating Users Using the login Command
From unprivileged mode, you can log in as any username in the local database using the login command.
Unlike enable authentication, this method is available in the system execution space in multiple context
mode.
This feature allows users to log in with their own username and password to access privileged mode, so
you do not have to give out the system enable password to everyone. To allow users to access privileged
mode (and all commands) when they log in, set the user privilege level to 2 (the default) through 15. If
you configure local command authorization, then the user can only enter commands assigned to that
privilege level or lower. See the “Configuring Local Command Authorization” section on page 12-10
for more information.
Caution
If you add users to the local database who can gain access to the CLI and whom you do not want to enter
privileged mode, you should configure command authorization. Without command authorization, users
can access privileged 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,
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 log in as a user from the local database, enter the following command:
FWSM> login
The FWSM prompts for your username and password. After you enter your password, the FWSM places
you in the privilege level that the local database specifies.
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Configuring Command Authorization
Configuring Command Authorization
By default when you log in, you can access unprivileged mode, which offers only minimal commands.
When you enter the enable command (or the login command when you use the local database), you can
access privileged mode and advanced commands, including configuration commands. If you want to
control the access to commands, the FWSM lets you configure command authorization, where you can
determine which commands that are available to a user.
This section includes the following topics:
•
Command Authorization Overview, page 12-10
•
Configuring Local Command Authorization, page 12-10
•
Configuring TACACS+ Command Authorization, page 12-13
Command Authorization Overview
You can use one of two command authorization methods:
•
Note
•
Local database—Configure the command privilege levels on the FWSM. When a local user
authenticates with the enable command (or logs in with the login command), the FWSM places that
user in the privilege level that is defined by the local database. The user can then access commands
at the user’s privilege level and below.
You can use local command authorization without any users in the local database and without
CLI or enable authentication. Instead, when you enter the enable command, you enter the
system enable password, and the FWSM places you in level 15. You can then create enable
passwords for every level, so that when you enter enable n (2 to 15), the FWSM places you in
level n. These levels are not used unless you turn on local command authorization (see
“Configuring Local Command Authorization” below). (See the Catalyst 6500 Series Switch and
Cisco 7600 Series Router Firewall Services Module Command Reference for more information
about enable.)
TACACS+ server—On the TACACS+ server, configure the commands that a user or group can use
after they authenticate for CLI access. Every command that a user enters at the CLI is checked with
the TACACS+ server.
Configuring Local Command Authorization
Local command authorization places each user at a privilege level, and each user can enter any command
at their privilege level or below. The FWSM lets you assign commands to one of 16 privilege levels (0
to 15). By default, each command is assigned either to privilege level 0 or to privilege level 15.
This section includes the following topics:
•
Local Command Authorization Prerequisites, page 12-11
•
Default Command Privilege Levels, page 12-11
•
Assigning Privilege Levels to Commands and Enabling Authorization, page 12-11
•
Viewing Command Privilege Levels, page 12-13
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Configuring Command Authorization
Local Command Authorization Prerequisites
Complete the following tasks as part of your command authorization configuration:
•
Configure enable authentication. (See the “Configuring Authentication to Access Privileged Mode”
section on page 12-8.)
Alternatively, you can use the login command (which is the same as the enable command with
authentication), which requires no configuration. We do not recommend this option because it is not
as secure as enable authentication.
You can also use CLI authentication (see the “Configuring Authentication for CLI Access” section
on page 12-8), but it is not required.
•
Configure each user in the local database at a privilege level from 0 to 15. (See the “Configuring the
Local Database” section on page 12-6.)
Default Command Privilege Levels
By default, the following commands are assigned to privilege level 0. All other commands are at
level 15.
•
show checksum
•
show curpriv
•
enable (enable mode)
•
help
•
show history
•
login
•
logout
•
pager
•
show pager
•
clear pager
•
quit
•
show version
If you move any configure mode commands to a lower level than 15, be sure to move the configure
command to that level as well, otherwise, the user will not be able to enter configuration mode.
To view all privilege levels, see the “Viewing Command Privilege Levels” section on page 12-13.
Assigning Privilege Levels to Commands and Enabling Authorization
To assign a command to a new privilege level, and enable authorization, follow these steps:
Step 1
To assign a command to a privilege level, enter the following command:
FWSM/contexta(config)# privilege [show | clear | configure] level level
[mode {enable | configure}] command command
Repeat this command for each command you want to reassign.
See the following information about the options in this command:
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Configuring Command Authorization
•
show | clear | configure—These optional keywords allow you to set the privilege only for the show,
clear, or configure form of the command. The configure form of the command is typically the form
that causes a configuration change, either as the unmodified command (without the show or clear
prefix) or as the no form. If you do not use one of these keywords, all forms of the command are
affected.
•
level level—A level between 0 and 15.
•
mode {enable | configure}—If a command can be entered in unprivileged/privileged mode as well
as configuration mode, and the command performs different actions in each mode, you can set the
privilege level for these modes separately:
– enable—Specifies both unprivileged mode and privileged mode.
– configure—Specifies configuration mode, accessed using the configure terminal command.
•
command command—The command you are configuring. You can only configure the privilege
level of the main command. For example, you can configure the level of all aaa commands, but not
the level of the aaa authentication command and the aaa authorization command separately.
Also, you cannot configure the privilege level of subcommands separately from the main command.
For example, you can configure the context command, but not the allocate-interface command,
which inherits the settings from the context command.
Step 2
To enable local command authorization, enter the following command:
FWSM/contexta(config)# aaa authorization command LOCAL
Even if you set command privilege levels, command authorization does not take place unless you enable
command authorization with this command.
For example, the filter command has the following forms:
•
filter (represented by the configure option)
•
show filter
•
clear filter
You can set the privilege level separately for each form, or set the same privilege level for all forms by
omitting this option. For example, set each form separately as follows:
FWSM/contexta(config)# privilege show level 5 command filter
FWSM/contexta(config)# privilege clear level 10 command filter
FWSM/contexta(config)# privilege configure level 10 command filter
Alternatively, you can set all filter commands to the same level:
FWSM/contexta(config)# privilege level 5 command filter
The show privilege command separates the forms in the display.
The following example shows the use of the mode keyword. The enable command must be entered from
unprivileged mode, while the enable password command, which is accessible in configuration mode,
requires the highest privilege level.
FWSM/contexta(config)# privilege configure level 0 mode enable command enable
FWSM/contexta(config)# privilege configure level 15 mode configure command enable
FWSM/contexta(config)# privilege show level 15 mode configure command enable
This example shows an additional command, the configure command, that uses the mode keyword:
FWSM/contexta(config)# privilege show level 5 mode configure command configure
FWSM/contexta(config)# privilege clear level 15 mode configure command configure
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FWSM/contexta(config)# privilege configure level 15 mode configure command configure
FWSM/contexta(config)# privilege configure level 15 mode enable command configure
Note
This last line is for the configure terminal command.
Viewing Command Privilege Levels
The following commands allow you to view privilege levels for commands.
•
To show all commands, enter the following command:
FWSM/contexta(config)# show privilege all
•
To shows command for a specific level, enter the following command:
FWSM/contexta(config)# show privilege level level
The level is an integer between 0 and 15.
•
To show the level of a specific command, enter the following command:
FWSM/contexta(config)# show privilege command command
For example, for the show privilege all command, the system displays the current assignment of each
CLI command to a privilege level. The following example illustrates the first part of the display:
FWSM(config)# show privilege all
privilege show level 15 command aaa
privilege clear level 15 command aaa
privilege configure level 15 command aaa
privilege show level 15 command aaa-server
privilege clear level 15 command aaa-server
privilege configure level 15 command aaa-server
privilege show level 15 command access-group
privilege clear level 15 command access-group
privilege configure level 15 command access-group
privilege show level 15 command access-list
privilege clear level 15 command access-list
privilege configure level 15 command access-list
privilege show level 15 command activation-key
privilege configure level 15 command activation-key
....
The following command displays the command assignments for privilege level 10:
FWSM/contexta(config)# show privilege level 10
privilege show level 10 command aaa
The following command displays the command assignment for the access-list command:
FWSM/contexta(config)# show privilege command access-list
privilege show level 15 command access-list
privilege clear level 15 command access-list
privilege configure level 15 command access-list
Configuring TACACS+ Command Authorization
If you enable TACACS+ command authorization, and a user enters a command at the CLI, the FWSM
sends the command and username to the TACACS+ server to determine if the command is authorized.
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When configuring command authorization with a TACACS+ server, do not save your configuration until
you are sure it works the way you want. If you get locked out because of a mistake, you can usually
recover access by restarting the FWSM. If you still get locked out, see the “Recovering from a Lockout”
section on page 12-19.
Be sure that your TACACS+ system is completely stable and reliable. The necessary level of reliability
typically requires that you have a fully redundant TACACS+ server system and fully redundant
connectivity to the FWSM. For example, in your TACACS+ server pool, include one server connected
to interface 1, and another to interface 2. You can also configure local command authorization as a
fallback method if the TACACS+ server is unavailable. In this case, you need to configure local users
and command privilege levels according to the “Configuring Local Command Authorization” section on
page 12-10.
This section includes the following topics:
•
TACACS+ Command Authorization Prerequisites, page 12-14
•
Configuring Commands on the TACACS+ Server, page 12-14
•
Enabling TACACS+ Command Authorization, page 12-17
TACACS+ Command Authorization Prerequisites
Complete the following tasks as part of your command authorization configuration:
•
Configure CLI authentication. (See the “Configuring Authentication for CLI Access” section on
page 12-8.)
•
Configure enable authentication. (See the “Configuring Authentication to Access Privileged Mode”
section on page 12-8.)
Configuring Commands on the TACACS+ Server
You can configure commands on a CiscoSecure Access Control Server (ACS) TACACS+ server as a
shared profile component, for a group, or for individual users. For third-party TACACS+ servers, see
your server documentation for more information about command authorization support.
See the following guidelines for configuring commands on a CiscoSecure ACS TACACS+ server
Version 3.1; many of these guidelines also apply to third-party servers:
•
Note
•
The FWSM sends the commands to be authorized as “shell” commands, so configure the commands
on the TACACS+ server as shell commands.
The Cisco Secure ACS server might include a command type called “pix-shell.” Do not use this
type for FWSM command authorization.
The first word of the command is considered to be the main command. All additional words are
considered to be arguments, which need to be preceded by permit or deny.
For example, to allow show aaa, aaa authentication, and aaa authorization command commands,
add aaa to the command box, and type permit authentication and permit authorization command
in the arguments box. The show aaa command must be listed separately. (See Figure 12-1 and
Figure 12-2.)
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Figure 12-1 Permitting Specific Commands
Figure 12-2 Permitting the Show Version of a Command
•
You can permit all arguments of a command that you do not explicitly deny by selecting the Permit
Unmatched Args check box.
For example, you can configure just the show command, and then all show commands are allowed.
We recommend using this method so that you do not have to anticipate every variant of a command,
including abbreviations and ?, which shows CLI usage. (See Figure 12-3.)
Figure 12-3 Permitting All Related Commands
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•
For commands that are a single word, you must permit unmatched arguments, even if there are no
arguments for the command, for example enable or help. (See Figure 12-4.)
Figure 12-4 Permitting Single Word Commands
•
To disallow some arguments, enter the arguments preceded by deny.
For example, to allow enable, but not enable password, enter enable in the commands box, and
deny password in the arguments box. Be sure to select the Permit Unmatched Args check box so
that enable alone is still allowed. (See Figure 12-5.)
Figure 12-5 Disallowing Arguments
•
When you abbreviate a command at the command line, the FWSM expands the prefix and main
command to the full text, but it sends additional arguments to the TACACS+ server as you enter
them.
For example, if you enter sh log, then the FWSM sends the entire command to the TACACS+ server,
show logging. However, if you enter sh log mess, then the FWSM sends show logging mess to the
TACACS+ server, and not the expanded command show logging message. You can configure
multiple spellings of the same argument to anticipate abbreviations. (See Figure 12-6.)
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Configuring Command Authorization
Figure 12-6 Specifying Abbreviations
•
We recommend that you allow the following basic commands for all users:
– show checksum
– show curpriv
– enable
– help
– show history
– login
– logout
– pager
– show pager
– clear pager
– quit
– show version
Enabling TACACS+ Command Authorization
Before you enable TACACS+ command authorization, be sure that you are logged into the FWSM as a
user that is defined on the TACACS+ server, and that you have the necessary command authorization to
continue configuring the FWSM. For example, you should log in as an admin user with all commands
authorized. Otherwise, you could become unintentionally locked out.
To perform command authorization using a TACACS+ server, enter the following command:
FWSM/contexta(config)# aaa authorization command tacacs+_server_group [LOCAL]
You can configure the FWSM to use the local database as a fallback method if the TACACS+ server is
unavailable. To enable fallback, specify the server group name followed by LOCAL (LOCAL is case
sensitive). We recommend that you use the same username and password in the local database as the
TACACS+ server because the FWSM prompt does not give any indication which method is being used.
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Viewing the Current Logged-In User
Be sure to configure users in the local database (see the “Configuring the Local Database” section on
page 12-6) and command privilege levels. (See the “Configuring Local Command Authorization”
section on page 12-10.)
Viewing the Current Logged-In User
To view the current logged-in user, enter the following command:
FWSM/contexta# show curpriv
See the following sample show curpriv command output. A description of each field follows.
FWSM/contexta# show curpriv
Username : admin
Current privilege level : 15
Current Mode/s : P_PRIV
Table 12-2 describes the show curpriv command output.
Table 12-2 show curpriv Display Description
Field
Description
Username
Username. If you are logged in as the default user, the name is enable_1
(unprivileged) or enable_15 (privileged).
Current privilege level Level from 0 to 15. Unless you configure local command authorization and
assign commands to intermediate privilege levels, levels 0 and 15 are the only
levels that are used.
Current Mode/s
Shows the access modes:
•
P_UNPR—Unprivileged mode (levels 0 and 1)
•
P_PRIV—Privileged mode (levels 2 to 15)
•
P_CONF—Configuration mode
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Recovering from a Lockout
Recovering from a Lockout
In some circumstances, when you turn on command authorization or CLI authentication, you can be
locked out of the FWSM CLI. You can usually recover access by restarting the FWSM. However, if you
already saved your configuration, you might be locked out. Table 12-3 lists the common lockout
conditions and how you might recover from them.
Table 12-3 CLI Authentication and Command Authorization Lockout Scenarios
Feature
Lockout Condition Description
Workaround: Single Mode
Workaround: Multiple Mode
Local CLI
authentication
No users in the
local database
If you have no users in
the local database, you
cannot log in, and you
cannot add any users.
Log into the maintenance
partition and reset the
passwords and aaa
commands. See the
“Clearing the Application
Partition Passwords and
AAA Settings” section on
page 17-9.
Session into the FWSM
from the switch. From the
system execution space, you
can change to the context
and add a user.
TACACS+
command
authorization
Server down or
unreachable and
you do not have
the fallback
method
configured
If the server is
unreachable, then you
cannot log in or enter
any commands.
TACACS+ CLI
authentication
1.
Log into the
maintenance partition
and reset the passwords
and AAA commands.
See the “Clearing the
Application Partition
Passwords and AAA
Settings” section on
page 17-9.
2.
Configure the local
database as a fallback
method so you do not
get locked out when the
server is down.
RADIUS CLI
authentication
1.
If the server is
unreachable because the
network configuration
is incorrect on the
FWSM, session into the
FWSM from the switch.
From the system
execution space, you
can change to the
context and reconfigure
your network settings.
2.
Configure the local
database as a fallback
method so you do not
get locked out when the
server is down.
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Configuring Authentication for Network Access
Table 12-3 CLI Authentication and Command Authorization Lockout Scenarios (continued)
Feature
Lockout Condition Description
TACACS+
command
authorization
You are logged in
as a user without
enough privileges
or as a user that
does not exist
Local command
authorization
You are logged in You enable command
as a user without authorization, but then
enough privileges find that the user
cannot enter any more
commands.
You enable command
authorization, but then
find that the user
cannot enter any more
commands.
Workaround: Single Mode
Workaround: Multiple Mode
Fix the TACACS+ server
user account.
Session into the FWSM
from the switch. From the
system execution space, you
can change to the context
and complete the
configuration changes. You
can also disable command
authorization until you fix
the TACACS+
configuration.
If you do not have access to
the TACACS+ server and
you need to configure the
FWSM immediately, then
log into the maintenance
partition and reset the
passwords and aaa
commands. See the
“Clearing the Application
Partition Passwords and
AAA Settings” section on
page 17-9.
Log into the maintenance
partition and reset the
passwords and aaa
commands. See the
“Clearing the Application
Partition Passwords and
AAA Settings” section on
page 17-9.
Session into the FWSM
from the switch. From the
system execution space, you
can change to the context
and change the user level.
Configuring Authentication for Network Access
This section includes the following topics:
•
Authentication Overview, page 12-20
•
Enabling Network Access Authentication, page 12-21
•
Enabling Secure Authentication of Web Clients, page 12-22
Authentication Overview
The FWSM lets you configure network access authentication using RADIUS or TACACS+ servers.
Although you can configure network access authentication for any protocol or service, you can
authenticate directly with HTTP, Telnet, or FTP only. A user must first authenticate with one of these
services before other traffic that requires authentication is allowed through. If you do not want to allow
HTTP, Telnet, or FTP through the FWSM, but want to authenticate other types of traffic, you can
configure virtual Telnet; the user Telnets to a given IP address configured on the FWSM, and the FWSM
provides a Telnet prompt. See the Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall
Services Module Command Reference for more information about the virtual telnet command.
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 Catalyst 6500 Series Switch and
Cisco 7600 Series Router Firewall Services Module Command Reference for timeout values.) For
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example, if you configure the FWSM 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.
For Telnet, HTTP, and FTP, the FWSM generates an authentication prompt. If the destination server also
has its own authentication, the user enters another username and password.
For FTP, a user has the option of entering the FWSM username followed by an at sign (@) and then the
FTP username ([email protected]). For the password, the user enters the FWSM 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 using multiple “at” signs (@).
Enabling Network Access Authentication
To configure authentication, enter the following command:
FWSM/contexta(config)# aaa authentication match acl_name interface_name server_group
Identify the source addresses and destination addresses using an extended ACL. Create the ACL using
the access-list command (see the “Adding an Extended Access Control List” section on page 10-13).
The permit access control entries (ACEs) mark matching traffic for authentication, while deny entries
exclude matching traffic from authentication. Be sure to include the destination ports for either HTTP,
Telnet, or FTP in the ACL because the user must authenticate with one of these services before other
services are allowed through the FWSM.
Note
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 Catalyst 6500
Series Switch and Cisco 7600 Series Router Firewall Services Module Command Reference for more
information.
For example, the following commands authenticate all inside HTTP traffic and SMTP traffic:
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
access-list MAIL_AUTH extended permit tcp any any eq smtp
access-list MAIL_AUTH extended permit tcp any any eq www
aaa-server AuthOutbound protocol tacacs+
aaa-server AuthOutbound (inside) host 10.1.1.1 TheUauthKey
aaa authentication match MAIL_AUTH inside AuthOutbound
The following commands authenticate Telnet traffic from the outside interface to a particular server
(209.165.201.5):
FWSM/contexta(config)#
eq telnet
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
access-list TELNET_AUTH extended permit tcp any host 209.165.201.5
aaa-server AuthInbound protocol tacacs+
aaa-server AuthInbound (inside) host 10.1.1.1 TheUauthKey
aaa authentication match TELNET_AUTH outside AuthInbound
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Enabling Secure Authentication of Web Clients
FWSM version 2.3 introduces a secured method of exchanging usernames and passwords between a web
client and an FWSM by using HTTP over SSL (HTTPS). HTTPS encrypts the username and password
and makes the transmission secure.
Previous versions of the FWSM, when authenticating a web browser using an AAA server, obtained the
username and password from the HTTP client in clear text.
Add the following keyword to the aaa command to enable this feature:
aaa authentication secure-http-client
The keyword secure-http-client enables this feature so that the username and password are exchanged
securely between HTTP clients and the FWSM.
To enable this feature, you must configure AAA authentication by using one of these formats:
aaa authentication http interface ...
aaa authentication tcp/0 interface ...
This feature supports authentication of clients accessing secure (HTTPS) websites by using this
command:
aaa authentication https interface ...
aaa authentication tcp/0 interface ...
Note
Enabling AAA authentication secure-http-client is not required to authenticate HTTPS sessions.
After enabling this feature, when a user accesses a web page requiring authentication, the FWSM
displays the Authentication dialog box shown in Figure 12-7.
Figure 12-7 Secure Authentication Page
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Configuring AAA
Configuring Authorization for Network Access
Note
The Cisco Systems text field shown in this example was customized using the auth-prompt command.
If you do not enter a string using the auth-prompt command, this field will be blank. For the detailed
syntax of this command, refer to the Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall
Services Module Command Reference.
After the you enter a valid username and password, an “Authentication Successful” page appears and
closes automatically. If you fail to enter a valid username and password, an “Authentication Failed” page
appears.
A maximum of 64 concurrent HTTPS authentications are allowed. If all 64 HTTPS authentication
processes are running, a new connection requiring authentication will not succeed. An authentication
process starts when the FWSM receives the user name and password from the browser and ends when it
receives the authentication result from the AAA server. The length of time required to complete each
authentication process depends on the response time from the authentication source. If the LOCAL
database is used, it is very fast; while if a RADIUS or TACACS+ server is used, it will depend on the
server response time.
Note
Pre-FWSM release 2.3, configurations that include AAA authentication include tcp/0.. and will inherit
the HTTPS Authentication Proxy feature enabled with a code upgrade to FWSM release 2.3 or later.
When using the uauth timeout 0 command, HTTPS authentication will not take place if a browser
initiates multiple TCP connections to get a web page after HTTPS authentication. In this scenario, the
first connection is allowed, yet the subsequent connections will trigger authentication because the uauth
timeout is set to 0. As a result, users will be presented with authentication pages continuously, even
though the correct username and password are entered each time. Avoid this problem by setting the uauth
timeout to 1 second. However, this setting opens a 1-second window that could conceivably allow a
non-authenticated user to obtain access from the same source IP address.
If a web browser launches an HTTPS web page request while secure authentication is in process for a
previous HTTP request, the HTTPS request triggers a second secure authentication process, even if
secure authentication is not specifically enabled for HTTPS. Once the authentication process for either
web page is completed successfully, the remaining request can be completed by reloading the page.
Because HTTPS authentication occurs on SSL port 443, do not use the access-list command to block
traffic from the HTTP client to HTTP server on port 443. Also, if you configure static PAT for web traffic
on port 80, you must also configure a static entry for SSL port 443.
Configuring Authorization for Network Access
After a user authenticates for a given connection, the FWSM checks for an authorization rule or a
dynamic ACL for the traffic. The authorization server or dynamic ACL then determines whether the
traffic is allowed or denied.
The FWSM supports TACACS+ authorization servers. You identify the traffic that you want to authorize
in the FWSM configuration, and the TACACS+ server determines a user’s authorization based on the
user profile.
Alternatively, you can use dynamic ACLs that are downloaded from a RADIUS server at the time of
authentication. The configuration on the FWSM consists only of the authentication configuration; you
enable downloadable ACLs on the server itself.
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Configuring Authorization for Network Access
This section includes the following topics:
•
Configuring TACACS+ Authorization, page 12-24
•
Configuring RADIUS Authorization, page 12-25
Configuring TACACS+ Authorization
The FWSM lets you configure network access authorization using TACACS+. You can identify the
traffic that needs to be authorized in the authorization rule, or by matching an ACL name. Authorization
rules can include only one source and destination subnet and service, while an ACL can include many
entries.
For all traffic that you want to authorize, a user must first authenticate with the FWSM for that traffic.
You can choose to authenticate, but not authorize, some traffic; be sure that the authorization rules are
equal to or a subset of the authentication rules. See the “Configuring Authentication for Network
Access” section on page 12-20 to configure authentication.
After a user authenticates, the FWSM checks the authorization rules for matching traffic. If the traffic
matches the authorization statement, the FWSM sends the username to the TACACS+ server. The
TACACS+ server responds to the FWSM with a permit or a deny for that traffic, based on the user’s
profile. See the TACACS+ server documentation for information about configuring network access
restrictions for a user.
To configure authorization, enter the following command:
FWSM/contexta(config)# aaa authorization match acl_name interface_name server_group
Identify the source addresses and destination addresses using an extended ACL. Create the ACL using
the access-list command (see the “Adding an Extended Access Control List” section on page 10-13).
The permit access control entries (ACEs) mark matching traffic for authorization, while deny entries
exclude matching traffic from authorization.
Note
You can alternatively use the aaa authorization include command (which identifies traffic within the
command). However, you cannot use both methods in the same configuration. See the Catalyst 6500
Series Switch and Cisco 7600 Series Router Firewall Services Module 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:
FWSM/contexta(config)#
FWSM/contexta(config)#
eq telnet
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
access-list TELNET_AUTH extended permit tcp any any eq telnet
access-list SERVER_AUTH extended permit tcp any host 209.165.201.5
aaa-server AuthOutbound protocol tacacs+
aaa-server AuthOutbound (inside) host 10.1.1.1 TheUauthKey
aaa authentication match TELNET_AUTH inside AuthOutbound
aaa authorization match SERVER_AUTH inside AuthOutbound
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Configuring AAA
Configuring Authorization for Network Access
Configuring RADIUS Authorization
You can configure a RADIUS server to download an ACL to the FWSM or an ACL name at the time of
authentication. See the “Configuring Authentication for Network Access” section on page 12-20 for
more information about configuring authentication. The user is authorized to do only what is permitted
in the user’s ACL. This section includes the following topics:
•
Configuring the RADIUS Server to Download Per-User Access Control Lists, page 12-25
•
Configuring the RADIUS Server to Download Per-User Access Control List Names, page 12-27
Configuring the RADIUS Server to Download Per-User Access Control Lists
This section describes how to configure a CiscoSecure ACS RADIUS server or a third-party RADIUS
server, and includes the following topics:
•
Configuring a CiscoSecure ACS RADIUS Server for Downloadable ACLs, page 12-25
•
Configuring a Third-Party RADIUS Server for Downloadable ACLs, page 12-26
Configuring a CiscoSecure ACS RADIUS Server for Downloadable ACLs
You can configure ACLs on the CiscoSecure ACS RADIUS server as a shared profile component and
then assign the ACL to a group or to an individual user.
The ACL definition consists of one or more FWSM commands that are similar to the extended
access-list command (see the “Adding an Extended Access Control List” section on page 10-13), except
without the following prefix:
access-list acl_name extended
The following example is an ACL definition before it is downloaded to the FWSM:
+--------------------------------------------+
| Shared profile Components
|
|
|
|
Downloadable PIX ACLs
|
|
|
| Name:
acs_ten_acl
|
| Description: 10 access-list commands |
|
|
|
|
|
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
|
+--------------------------------------------+
The downloaded ACL on the FWSM has the following name:
#ACSACL#-ip-acl_name-number
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The acl_name argument is the name that is defined on the RADIUS server, and number is a unique
version ID.
The downloaded ACL on the FWSM 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-fwsm-acs_ten_acl-3b5385f7
#ACSACL#-ip-fwsm-acs_ten_acl-3b5385f7
#ACSACL#-ip-fwsm-acs_ten_acl-3b5385f7
#ACSACL#-ip-fwsm-acs_ten_acl-3b5385f7
#ACSACL#-ip-fwsm-acs_ten_acl-3b5385f7
#ACSACL#-ip-fwsm-acs_ten_acl-3b5385f7
#ACSACL#-ip-fwsm-acs_ten_acl-3b5385f7
#ACSACL#-ip-fwsm-acs_ten_acl-3b5385f7
#ACSACL#-ip-fwsm-acs_ten_acl-3b5385f7
#ACSACL#-ip-fwsm-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 a Third-Party RADIUS Server for Downloadable ACLs
Configure the ACL using Cisco Vendor Specific Attribute (VSA) number 1 (cisco-AV-pair).
Configure one or more access control entries (ACEs) that are similar to the extended access-list
command (see the “Adding an Extended Access Control List” section on page 10-13), 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 FWSM. If this parameter is omitted, the sequence value is 0, and the
order in the RADIUS configuration is used.
The following example is an ACL definition before it is downloaded to the FWSM:
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
The downloaded ACL name has the following format:
AAA-user-username
The username argument is the name of the user that is being authenticated.
The downloaded ACL on the FWSM 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-john
AAA-user-john
AAA-user-john
AAA-user-john
AAA-user-john
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 ACLs have two spaces between the word “access-list” and the name. These spaces serve to
differentiate a downloaded ACL from a local ACL.
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Configuring Accounting for Network Access
Configuring the RADIUS Server to Download Per-User Access Control List Names
To download a name for an ACL that you already created on the FWSM from the RADIUS server when
a user authenticates, configure RADIUS attribute 11 (filter-id) as follows:
filter-id=acl_name
See the “Adding an Extended Access Control List” section on page 10-13 to create an ACL on the
FWSM.
Configuring Accounting for Network Access
The FWSM can send accounting information to a RADIUS or TACACS+ server about any TCP or UDP
traffic that passes through the FWSM. 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, the AAA client messages and username, the number of bytes that pass through the FWSM for
the session, the service used, and the duration of each session.
To configure accounting, enter the following command:
FWSM/contexta(config)# aaa accounting match acl_name interface_name server_group
Identify the source addresses and destination addresses using an extended ACL. Create the ACL using
the access-list command (see the “Adding an Extended Access Control List” section on page 10-13).
The permit access control entries (ACEs) mark matching traffic for accounting, while deny entries
exclude matching traffic from accounting.
Note
You can alternatively use the aaa accounting include command (which identifies traffic within the
command). However, you cannot use both methods in the same configuration. See the Catalyst 6500
Series Switch and Cisco 7600 Series Router Firewall Services Module 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:
FWSM/contexta(config)#
FWSM/contexta(config)#
eq telnet
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
access-list TELNET_AUTH extended permit tcp any any eq telnet
access-list SERVER_AUTH extended permit tcp any host 209.165.201.5
aaa-server AuthOutbound protocol tacacs+
aaa-server AuthOutbound (inside) host 10.1.1.1 TheUauthKey
aaa authentication match TELNET_AUTH inside AuthOutbound
aaa authorization match SERVER_AUTH inside AuthOutbound
aaa accounting match SERVER_AUTH inside AuthOutbound
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Configuring AAA
Configuring Accounting for Network Access
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C H A P T E R
13
Configuring Application Protocol Inspection
This chapter describes how to use and configure application protocol inspection, which is often called a
“fixup.” 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
Firewall Services Module (FWSM) to do a deep packet inspection instead of passing the packet through
the fast path (see the “Stateful Inspection Feature” section on page 1-5 for more information about the
fast path). As a result, inspection engines can affect overall throughput.
Several common inspection engines are enabled on the FWSM by default, but you might need to enable
others depending on your network. This chapter includes the following sections:
•
Inspection Engine Overview, page 13-1
•
Configuring an Inspection Engine, page 13-4
•
Detailed Information About Inspection Engines, page 13-5
Inspection Engine Overview
This section includes the following topics:
•
When to Use Application Protocol Inspection, page 13-1
•
Inspection Limitations, page 13-2
•
Inspection Support, page 13-2
When to Use Application Protocol Inspection
When a user establishes a connection, the FWSM checks the packet against access control lists (ACLs),
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 FWSM.
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 FWSM translates
embedded addresses and updates any checksum or other fields that are affected by the translation.
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Inspection Engine Overview
When you enable application inspection for a service that uses dynamically assigned ports, the FWSM
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:
•
You can configure up to 32 inspection engines per context. This limit includes the following
inspection engines that are enabled by default, making the total number of configurable inspection
engines 27: TFTP, Sun RPC over UDP, NetBIOS NameServer, XDMCP, and CUSeeMe. The
OraServ and RealAudio inspection engines, which are also enabled by default, do not affect this
limit.
•
State information for multimedia sessions that require inspection are not passed over the state link
for stateful failover.
•
For fragmented IP packets, only the first fragment is inspected.
•
For segmented TCP packets, if messages are divided between segments, the FWSM cannot inspect
the packets.
•
Some inspection engines do not support PAT, NAT, policy NAT, outside NAT, or NAT between same
security interfaces. See “Inspection Support” for more information about NAT support.
•
DNS fixups are limited to 4000 per second.
Inspection Support
Table 13-1 describes the inspection engines supported by the FWSM and whether they are compatible
with Network Address Translation (NAT), Port Address Translation (PAT), outside NAT, or NAT
between same security interfaces. If a inspection engine does not support outside NAT, consider using
the alias command instead of outside NAT. See the Catalyst 6500 Series Switch and Cisco 7600 Series
Router Firewall Services Module Command Reference for more information about the alias command.
Inspection engines that are enabled for the default port by default are in bold.
Table 13-1 Inspection Engine Support
Application1
CUSeeMe
Configurable Default Port
No
UDP/7648
DNS over
Yes
UDP
FTP
Yes
H.323 H.225 Yes
and RAS
HTTP
ICMP
ICMP error
Yes
Yes
Yes
UDP/53
TCP/21
TCP/1720
UDP/1718-1719
TCP/80
—
—
NAT Limitations
No NAT or PAT. Use NAT
identity or NAT exemption only.
No NAT support is available for
name resolution through WINS.
—
No outside NAT. Use the alias
command.
Comments
—
Standards2
—
No PTR records are
changed.
—
Does not support
segmented messages.
RFC 1123
No NAT on same security
interfaces.
—
—
—
—
—
—
RFC 1123
ITU-T H.323,
H.245, H225.0,
Q.931, Q.932
RFC 2616
—
—
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Inspection Engine Overview
Table 13-1 Inspection Engine Support (continued)
Application1
ILS (LDAP)
Configurable Default Port
Yes
TCP/389
MGCP
Yes
NetBIOS
Name Server
over IP
OraServ
RealAudio
RSH
RTSP
SIP TCP
SIP UDP
SKINNY
(SCCP)
NAT Limitations
No outside NAT. Use the alias
command.
Comments
—
No
UDP/2427,
2727
UDP/137-138
No PAT.
No NAT or PAT. Use NAT
—
identity or NAT exemption only.
—
—
No
No
Yes
Yes
UDP/1525
UDP/7070
TCP/514
TCP/554
—
—
No PAT.
No PAT.
Yes
Yes
Yes
TCP/5060
UDP/5060
TCP/2000
SMTP
SQL*Net
Sun RPC
over UDP
Sun RPC
over TCP
TFTP
Yes
Yes
No
TCP/25
TCP/1521 (v1)
UDP/111
Yes
TCP/111
No
UDP/69
XDMCP
No
UDP/177
No outside NAT. Use the alias
command.
No outside NAT. Use the alias
command.
No NAT on same security
interfaces.
No outside NAT. Use the alias
command.
No NAT on same security
interfaces.
No outside NAT. Use the alias
command.
No NAT on same security
interfaces.
—
No policy NAT.
No NAT or PAT. Use NAT
identity or NAT exemption only.
No NAT or PAT. Use NAT
identity or NAT exemption only.
Payload IP address not
translated.
No NAT or PAT. Use NAT
identity or NAT exemption only.
Standards2
—
RFC2705bis-05
—
—
—
—
No handling for HTTP
cloaking.
Berkeley UNIX
RFC 2326, RFC
2327, RFC 1889
—
RFC 2543
—
RFC 2543
Does not handle TFTP
uploaded Cisco IP
Phone configurations.
—
—
v1 and v2.
—
RFC 821, 1123
—
—
—
—
—
RFC 1350
—
—
1. Inspection engines that are enabled by default for the default port are in bold.
2. The FWSM 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 FWSM does not enforce the order.
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Configuring Application Protocol Inspection
Configuring an Inspection Engine
Configuring an Inspection Engine
Disabling or modifying an inspection engine only affects connections that are initiated after the
command is processed. Disabling an inspection engine for a specific port or application does not affect
existing connections. If you want the change to take effect immediately, enter the clear xlate command
to remove all existing sessions.
To configure an inspection engine, enter the following command:
FWSM/contexta(config)# fixup protocol {
dns [maximum-length length]
ftp [strict] [port[-port]] |
h323 {h225 | ras} [port[-port]] |
http [port[-port]] |
icmp |
icmp error |
ils [port[-port]] |
mgcp [port[-port] |
rpc [port[-port] |
rsh [port[-port] |
rtsp [port[-port] |
sip [port[-port] |
sip udp |
skinny [port[-port] |
smtp [port[-port]] |
sqlnet [port[-port]]}
For most applications and protocols, you can define multiple port assignments, which is useful when
multiple instances of the same service are running on different ports.
Because you can enter multiple ports (either as a range or as separate commands), if you specify a new
port, that port is added to the configuration along with previously configured ports. To remove a port,
enter the no version of the command.
See the following keywords:
•
dns maximum-length length—This option sets the maximum length of a DNS reply. The default is
512 bytes. This inspection engine uses UDP port 53, and the port is not configurable.
•
ftp strict—This option only lets an FTP server generate the 227 command and only lets an FTP
client generate the PORT command. The 227 and PORT commands are checked to ensure they do
not appear in an error string. This limitation prevents clients from sending embedded commands in
FTP requests. Each FTP command must be acknowledged before a new command is allowed.
•
h323 {h225 | ras}—You can set the inspection engines for H.323 and RAS (h225 and ras)
separately.
See the “Detailed Information About Inspection Engines” section on page 13-5 for information about
each protocol inspection engine.
By default, an inspection engine for FTP port 21 is enabled. The following example shows how to define
additional ports for FTP:
FWSM/contexta(config)# fixup protocol ftp 2100
FWSM/contexta(config)# fixup protocol ftp 4254
FWSM/contexta(config)# fixup protocol ftp 9090
After entering these commands, the FWSM listens for FTP traffic on port 21, as well as 2100, 4254, and
9090.
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Detailed Information About Inspection Engines
The following command assigns the port range from 1500 to 2000 to SQL*Net:
FWSM/contexta(config)# fixup protocol sqlnet 1500-2000
Detailed Information About Inspection Engines
•
CUSeeMe Inspection Engine, page 13-5
•
DNS over UDP Inspection Engine, page 13-6
•
FTP Inspection Engine, page 13-6
•
H.323 Inspection Engine, page 13-7
•
HTTP Inspection Engine, page 13-10
•
ICMP Inspection Engine, page 13-10
•
ICMP Error Inspection Engine, page 13-11
•
ILS Inspection Engine, page 13-11
•
MGCP Inspection Engine, page 13-12
•
NetBios Name Service Inspection Engine, page 13-14
•
OraServ Inspection Engine, page 13-14
•
RealAudio Inspection Engine, page 13-14
•
RSH Inspection Engine, page 13-15
•
RTSP Inspection Engine, page 13-15
•
SIP Inspection Engine, page 13-16
•
Skinny Inspection Engine, page 13-18
•
SMTP Inspection Engine, page 13-19
•
SQL*Net Inspection Engine, page 13-20
•
Sun RPC Inspection Engine, page 13-21
•
TFTP Inspection Engine, page 13-21
•
XDMCP Inspection Engine, page 13-22
CUSeeMe Inspection Engine
Enabled by default for UDP port 7648
Not Configurable
With CUSeeMe clients, one user can connect directly to another (CUSeeMe or other H.323 client) for
person-to-person audio, video, and data collaboration. CUSeeMe clients can conference in a mixed
client environment that includes both CUSeeMe clients and H.323-compliant clients from other vendors.
Behind the scenes, CUSeeMe clients operate in two different modes. When connected to another
CUSeeMe client or CUSeeMe Conference Server, the client sends information in CUSeeMe mode.
When connected to an H.323-compliant videoconferencing client from a different vendor, CUSeeMe
clients communicate using the H.323-standard format in H.323 mode.
CUSeeMe is supported through H.323 inspection, as well as performing NAT on the CUSeeMe control
stream, which operates on UDP port 7648.
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Detailed Information About Inspection Engines
DNS over UDP Inspection Engine
Enabled by default for UDP port 53
Domain Name System (DNS) requests require an inspection engine so that DNS queries are not subject
to the generic UDP handling based on activity timeouts. Instead, the UDP connections associated with
DNS queries and responses are torn down as soon as a reply to a DNS query has been received. The DNS
inspection engine monitors the message exchange to ensure that the ID of the DNS reply matches the ID
of the DNS query. See the “DNS and NAT” section on page 9-13 for more information about how the
FWSM alters the DNS payload.
This functionality is different from DNS Guard. See the “Other Protection Features” section on page 1-6
for more information about DNS Guard.
To configure the maximum length of the DNS reply, enter the following command:
FWSM/contexta(config)# fixup protocol dns [maximum-length length]
The default is 512 bytes. The port is 53 (UDP) and is not configurable.
FTP Inspection Engine
Enabled by default for TCP port 21
To configure the FTP inspection engine, enter the following command:
FWSM/contexta(config)# fixup protocol ftp
[strict] port[-port]
The default port is 21 (TCP).
If you disable FTP inspection engines with the no fixup protocol ftp command, outbound users can start
connections only in passive mode, and inbound users can start connections only in active mode.
The FTP inspection engine inspects the FTP sessions, and performs four tasks:
•
Prepares dynamic secondary data connection—The channels are allocated in response to a file
upload, a file download, or a directory listing event and must be pre-negotiated. The port is
negotiated through the PORT or PASV commands.
•
Tracks ftp command-response sequence—If the strict option is enabled, each ftp command and
response sequence is tracked for the following anomalous activity:
– Truncated command—Number of commas in the PORT and PASV reply command is checked
to see if it is five. If it is not five, then the PORT command is assumed to be truncated and the
TCP connection is closed.
– Incorrect command—Checks the ftp command to see if it ends with <CR><LF> characters, as
required by the RFC. If it does not, the connection is closed.
– Size of RETR and STOR commands—These are checked against a fixed constant of 256. If the
size is greater, then an error message is logged and the connection is closed.
– Command spoofing—The PORT command should always be sent from the client. The TCP
connection is denied if a PORT command is sent from the server.
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– Reply spoofing—PASV reply command (227) should always be sent from the server. The TCP
connection is denied if a PASV reply command is sent from the client. This prevents the security
hole when the user executes “227 xxxxx a1, a2, a3, a4, p1, p2.”
– TCP stream editing.
– Invalid port negotiation—The negotiated dynamic port value is checked to see if it is less than
1024. As port numbers in the range from 1 to 1024 are reserved for well-known connections, if
the negotiated port falls in this range, then the TCP connection is freed.
– Command pipelining—The number of characters present after the port numbers in the PORT
and PASV reply command is cross checked with a constant value of 8. If it is more than 8, then
the TCP connection is closed.
Note
•
The use of the strict option may break FTP clients that do not comply with the RFC standards.
Generates an audit trail—The FTP inspection engine generates the following system messages:
– System message 303002 is generated for each file that is retrieved or uploaded.
– System message 201005 is generated if the secondary dynamic channel preparation failed due
to memory shortage.
•
Translates embedded IP addresses—In conjunction with NAT, the FTP inspection engine translates
the IP address within the application payload. This is described in detail in RFC 959.
H.323 Inspection Engine
H.323 H.225 enabled by default for TCP port 1720
H.323 RAS enabled by default for UDP ports 1718-1719
The fixup protocol h323 command provides support for H.323-compliant endpoints. The FWSM
supports H.323 Version 2, 3, and 4.
H.323 is a suite of protocols defined by the International Telecommunication Union (ITU) for
multimedia conferences over LANs. H.323 supports VoIP gateways and VoIP gatekeepers.
This section includes the following topics:
•
Configuring the H.323 Inspection Engine, page 13-7
•
Multiple Calls on One Call Signalling Connection, page 13-8
•
Viewing Connection Status, page 13-8
•
Technical Background, page 13-8
Configuring the H.323 Inspection Engine
To configure the H.323 inspection engine, enter the following command:
FWSM/contexta(config)# fixup protocol h323 {h225 | ras} [port[-port]]
You can set the inspection engines for H.232 and RAS (h225 and ras) separately. The default port for
h225 is 1720 (TCP), and the default ports for ras are 1718-1719 (UDP).
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Multiple Calls on One Call Signalling Connection
Allowing multiple calls on the same call signaling channel reduces call setup time and reduces the use
of ports on the FWSM.
To configure how long the H.225 call signaling channel stays open, enter the following command:
FWSM/contexta(config)# timeout h225 hh[:mm[:ss]]
The default is 1 hour.
For example, to keep the channel open without any timeout, set the timer to 0 by entering the following
command:
timeout h225 00:00:00
To disable the timer and close the TCP connection immediately after all calls are cleared, set the timeout
value to 1 second, as follows:
timeout h225 00:00:01
Viewing Connection Status
To display the status of H.225 connections, enter the following command:
FWSM/contexta(config)# show conn state h225
Technical Background
The H.323 collection of protocols collectively can use up to two TCP connections and four to six UDP
connections. FastConnect uses only one TCP connection, and RAS uses a single UDP connection for
registration, admissions, and status.
An H.323 client might initially establish a TCP connection to an H.323 server using TCP port 1720 to
request Q.931 call setup. As part of the call setup process, the H.323 terminal supplies a port number to
the client to use for an H.245 TCP connection.
Note
In environments where an H.323 gatekeeper is in use, the initial packet is transmitted using UDP.
The H.323 inspection engine monitors the Q.931 TCP connection to determine the H.245 port number.
If the H.323 terminals are not using FastConnect, the FWSM dynamically allocates the H.245
connection based on the inspection of the H.225 messages.
Within each H.245 message, the H.323 endpoints exchange port numbers that are used for subsequent
UDP data streams. The H.323 inspection engine inspects the H.245 messages to identify these ports and
dynamically creates connections for the media exchange. Real-Time Transport Protocol (RTP) uses the
negotiated port number, while RTP Control Protocol (RTCP) uses the next higher port number.
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The H.323 control channel handles H.225 and H.245 and H.323 RAS. The H.323 inspection engine uses
the following ports:
•
1718—Gate Keeper Discovery UDP port
•
1719—RAS UDP port
•
1720—TCP Control Port
The two major functions of the H.323 inspection engine are as follows:
•
NAT the necessary embedded IPv4 addresses in the H.225 and H.245 messages. Because H.323
messages are encoded in PER encoding format, FWSM uses an ASN.1 decoder to decode the H.323
messages. The H.323 inspection engine supports static NAT and dynamic NAT. It does not support
NAT on same security interfaces or outside NAT.
•
Dynamically allocate the negotiated H.245 and RTP/RTCP connections.
The FWSM administrator must configure an access control list (ACL) for the well-known H.323 port
1720 for the H.225 call signaling. However, the H.245 signaling ports are negotiated between the
endpoints in the H.225 signaling.
Note
When an H.323 gatekeeper is used, the FWSM opens an H.225 connection based on inspection of the
AdmissionConfirm (ACF) message.
The FWSM dynamically allocates the H.245 channel after inspecting the H.225 messages and then
“hooks up” the H.245 channel to be fixed up as well. That means whatever H.245 messages pass through
the FWSM are passed through the H.245 inspection engine, NATing embedded IP addresses and opening
the negotiated media channels.
The H.323 ITU standard requires that a TPKT header, defining the length of the message, precede the
H.225 and H.245, before being passed on to the reliable connection. Because the TPKT header does not
necessarily need to be sent in the same TCP packet as the H.225/H.245 message, the FWSM must
remember the TPKT length to process/decode the messages properly. FWSM keeps a data structure for
each connection and that data structure contains the TPKT length for the next expected message.
If the FWSM needs to NAT any IP addresses, then it will have to change the checksum, the UUIE
(user-user information element) length, and the TPKT, if included in the TCP packet with the H.225
message. If the TPKT is sent in a separate TCP packet, then the FWSM will proxy ACK that TPKT and
append a new TPKT to the H.245 message with the new length.
Note
The FWSM does not support TCP options in the Proxy ACK for the TPKT.
Each UDP connection with a packet going through the H.323 inspection engine is marked as an H.323
connection and will time out with the H.323 timeout as configured by the administrator using the
timeout command.
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HTTP Inspection Engine
The HTTP inspection engine enables the system message 304001 when an inside user issues an HTTP
GET request:
%FWSM-5-304001: user source_address Accessed [JAVA] URL dest_address: url.
To configure the HTTP inspection engine, enter the following command:
FWSM/contexta(config)# fixup protocol http [port[-port]]
The default port is 80 (TCP).
ICMP Inspection Engine
The ICMP inspection engine allows ICMP traffic to have a “session” so it can be inspected like TCP and
UDP traffic. Without the ICMP inspection engine, we recommend that you do not allow ICMP through
the FWSM in an ACL. Without stateful inspection, ICMP can be used to attack your network. The ICMP
inspection engine ensures that there is only one response for each request, and that the sequence number
is correct.
To configure the ICMP inspection engine, enter the following command:
FWSM/contexta(config)# fixup protocol icmp
The ICMP payload is scanned to retrieve the five-tuple from the original packet. The ICMP inspection
engine supports both one-to-one NAT and PAT. Using the retrieved five-tuple, a lookup is performed to
determine the original address of the client. The ICMP inspection engine makes the following changes
to the ICMP packet:
•
In the IP Header, the NAT IP is changed to the Client IP (Destination Address) and the IP checksum
is modified.
•
In the ICMP Header, the ICMP checksum is modified due to the changes in the ICMP packet.
•
In the Payload, the following changes are made:
– Original packet NAT IP is changed to the Client IP
– Original packet NAT port is changed to the Client Port
– Original packet IP checksum is recalculated
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ICMP Error Inspection Engine
The FWSM supports NAT of ICMP error messages. When this feature is enabled, the FWSM creates
translation sessions for intermediate hops that send ICMP error messages, based on the NAT
configuration. The FWSM overwrites the packet with the translated IP addresses.
To configure the ICMP error inspection engine, enter the following command:
FWSM/contexta(config)# fixup protocol icmp error
When disabled, the FWSM does not create translation sessions for intermediate nodes that generate
ICMP error messages. ICMP error messages generated by the intermediate nodes between the inside host
and the FWSM reach the outside host without consuming any additional NAT resource. This is
undesirable when an outside host uses the traceroute command to trace the hops to the destination on
the inside of the FWSM. When the FWSM does not NAT the intermediate hops, all the intermediate hops
appear with the translated destination IP address.
ILS Inspection Engine
Enabled by default for TCP port 389
The Internet Locator Service (ILS) is based on the Lightweight Directory Access Protocol (LDAP) and
is LDAPv2 compliant. ILS was developed by Microsoft for use with its NetMeeting, SiteServer, and
Active Directory products.
To configure the ILS inspection engine, enter the following command:
FWSM/contexta(config)# fixup protocol ils [port[-port]]
The default port is 389 (TCP).
The FWSM supports NAT for ILS, which is used to register and locate endpoints in the ILS or SiteServer
Directory. PAT is not supported because only IP addresses, and not ports, are stored by an LDAP
database.
For search responses, when the LDAP server is located outside, NAT should be considered to allow
internal peers to communicate locally while registered to external LDAP servers. For such search
responses, translation sessions are searched first, and then NAT entries to obtain the correct address. If
both of these searches fail, then the address is not changed.
Note
For sites using NAT exemption or identity NAT, we recommend that you disable this inspection engine
for better performance.
Additional configuration might be necessary when the ILS server is located inside the FWSM border.
This requires an ACL for outside clients to access the LDAP server on the specified port, typically
TCP 389.
ILS/LDAP follows a client/server model with sessions handled over a single TCP connection.
Depending on the client’s actions, several of these sessions might be created.
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During connection negotiation time, a Berkeley Internet Name Domain (BIND) protocol data unit (PDU)
is sent from the client to the server. Once a successful BIND RESPONSE from the server is received,
other operational messages might be exchanged (such as ADD, DEL, SEARCH, or MODIFY) to perform
operations on the ILS Directory. The ADD REQUEST and SEARCH RESPONSE PDUs might contain
IP addresses of NetMeeting peers, used by H.323 (SETUP and CONNECT messages) to establish
NetMeeting sessions. Microsoft NetMeeting v2.X and v3.X provide ILS support.
The ILS inspection engine performs the following operations:
•
Decodes the LDAP REQUEST/RESPONSE PDUs using the bit error rate (BER) decode functions
•
Parses the LDAP packet
•
Extracts IP addresses
•
Translates IP addresses as necessary
•
Encodes the PDU with translated addresses using BER encode functions
•
Copies the newly encoded PDU back to the TCP packet
•
Performs incremental TCP checksum and sequence number adjustment
The ILS inspection engine has the following limitations:
•
Referral requests and responses are not supported
•
Users in multiple directories are not unified
•
Single hosts that register to multiple directories using different name are not supported by the ILS
inspection engine. You must use the same for all directories.
MGCP Inspection Engine
The Media Gateway Control Protocol (MGCP) is used for controlling media gateways from external call
control elements called media gateway controllers, or call agents. A media gateway is typically a
network element that provides conversion between the audio signals carried on telephone circuits and
data packets carried over the Internet or over other packet networks.
To use MGCP, you typically need to configure at least two ports. One on which the gateway receives
commands and one for the port on which the call agent receives commands. Normally, a call agent sends
commands to port 2427, while a gateway sends commands to port 2727.
To configure the MGCP inspection engine, enter the following command:
FWSM/contexta(config)# fixup protocol mgcp port[-port]
The default ports are 2427 and 2727
Neither NAT or PAT are supported by the FWSM with MGCP.
This section includes the following topics:
•
MGCP Overview, page 13-13
•
Configuration for Multiple Call Agents and Gateways, page 13-13
•
Viewing MGCP Information, page 13-14
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MGCP Overview
Examples of media gateways are:
•
Trunking gateways, that interface between the telephone network and a Voice over IP network. Such
gateways typically manage a large number of digital circuits.
•
Residential gateways, that provide a traditional analog (RJ11) interface to a Voice over IP network.
Examples of residential gateways include cable modem/cable set-top boxes, xDSL devices,
broad-band wireless devices.
•
Business gateways, that provide a traditional digital PBX interface or an integrated soft PBX
interface to a Voice over IP network.
MGCP messages are transmitted over UDP. A response is sent back to the source address (IP address
and UDP port number) of the command, but the response may not arrive from the same address as the
command was sent to. This can happen when multiple call agents are being used in a failover
configuration and the call agent that received the command has passed control to a backup call agent,
which then sends the response.
Configuration for Multiple Call Agents and Gateways
Use the following commands to configure the FWSM to support the use of multiple MGCP call agents
and gateways:
•
To specify a group of call agents that can manage one or more gateways, enter the following
command:
FWSM/contexta(config)# mgcp call-agent ip_address group_id
This information is used to open connections for the other call agents than the one a gateway sends
a command to, so that any of the call agents can send the response. The ip_address specifies the IP
address of the call agent. The group_id is a number from 0 to 4294967295. Call agents with the same
group_id belong to the same group.
•
To specify the maximum number of MGCP commands that can be queued waiting for a response,
enter the following command:
FWSM/contexta(config)# mgcp command-queue limit
The range of allowed values for limit is 1 to 4294967295. The default is 200. When the limit is
reached and a new command arrives, the command that was in the queue for the longest time is
removed.
•
To specify which group of call agents are managing a particular gateway, enter the following
command:
FWSM/contexta(config)# mgcp gateway ip_address group_id
The IP address of the gateway is specified with the ip_address option. The group_id option is a
number from 0 to 4294967295. It must correspond with the group_id of the call agents that are
managing the gateway.
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The following example limits the MGCP command queue to 150 commands, allows call agents
10.10.11.5 and 10.10.11.6 to control gateway 10.10.10.115 and allows call agents 10.10.11.7 and
10.10.11.8 to control gateway 10.10.10.116:
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
mgcp
mgcp
mgcp
mgcp
mgcp
mgcp
mgcp
call-agent 10.10.11.5 101
call-agent 10.10.11.6 101
call-agent 10.10.11.7 102
call-agent 10.10.11.8 102
command-queue 150
gateway 10.10.10.115 101
gateway 10.10.10.116 102
Viewing MGCP Information
•
To view information about MGCP, enter the following command:
FWSM/contexta(config)# show mgcp {commands | sessions} [detail]
Use the commands option to list the commands in the command queue. Use the sessions option to
list the existing MGCP sessions. Use the detail option to list detailed information about each
command or session.
•
To show information about the MGCP connections, enter the following command:
FWSM/contexta(config)# show conn {detail | state} mgcp
Use the detail option to display detailed information about the MGCP connections. Use the state
option to display the media connections created for MGCP sessions.
NetBios Name Service Inspection Engine
Enabled by default for UDP ports 137 and 138
Not Configurable
The NetBios inspection engine translates IP addresses in the NetBios name service (NBNS) packets
according to the FWSM NAT configuration.
OraServ Inspection Engine
Enabled by default for UDP port 1525
Not Configurable
The OraServ inspection engine allows the data channel to go through the FWSM.
RealAudio Inspection Engine
Enabled by default for UDP port 7070
Not Configurable
The RealAudio inspection engine allows the data channel to go through the FWSM when the data
channel source port is between UDP ports 6790 and 7170.
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RSH Inspection Engine
Enabled by default for TCP port 514
The Remote Shell (RSH) protocol uses a TCP connection from the RSH client to the RSH server on
TCP port 514. The client and server negotiate the TCP port number where the client will listen for the
STDERR output stream. The RSH inspection engine supports NAT of the negotiated port number if
necessary.
To configure the RSH inspection engine, enter the following command:
FWSM/contexta(config)# fixup protocol rsh [port[-port]]
The default port for the initial RSH connection is 514 (TCP).
RTSP Inspection Engine
Real Time Streaming Protocol (RTSP) is used by RealAudio, RealNetworks, Apple QuickTime 4,
RealPlayer, and Cisco IP/TV connections. FWSM does not support multicast RTSP.
RTSP applications use the well-known port 554 with TCP (rarely UDP) as a control channel. The FWSM
only supports TCP, in conformity with RFC 2326.
This TCP control channel is used to negotiate the data channels that are used to transmit audio/video
traffic, depending on the transport mode that is configured on the client.
The supported Real Data Transports (RDTs) are: rtp/avp, rtp/avp/udp, x-real-rdt, x-real-rdt/udp, and
x-pn-tng/udp.
The FWSM parses Setup response messages with a status code of 200. If the response message is
travelling inbound, the server is outside relative to the FWSM and dynamic channels need to be opened
for connections coming inbound from the server. If the response message is outbound, then the FWSM
does not need to open dynamic channels.
Because RFC 2326 does not require that the client and server ports must be in the SETUP response
message, the FWSM will need to keep state and remember the client ports in the SETUP message.
QuickTime places the client ports in the SETUP message and then the server responds with only the
server ports.
To configure the RTSP inspection engine, enter the following command:
FWSM/contexta(config)# fixup protocol rtsp [port[-port]]
The default port is 554 (TCP).
If you are using Cisco IP/TV, use RTSP TCP port 554 and TCP 8554 as follows:
FWSM/contexta(config)# fixup protocol rtsp 554
FWSM/contexta(config)# fixup protocol rtsp 8554
The following restrictions apply to the RTSP inspection engine:
•
The FWSM does not inspect RTSP messages passing through UDP ports.
•
The FWSM does not inspect inbound RTSP connections.
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•
The FWSM does not support RealNetworks multicast mode (x-real-rdt/mcast).
•
The FWSM does not support PAT and outside NAT for RTSP.
•
The FWSM does not have the ability to recognize HTTP cloaking where RTSP messages are hidden
in HTTP messages.
•
The FWSM cannot perform NAT on RTSP messages because the embedded IP addresses are
contained in the Session Description Protocol (SDP) files as part of HTTP or RTSP messages.
Packets could be fragmented, and the FWSM cannot perform NAT on fragmented packets.
•
With Cisco IP/TV, the number of translations the FWSM performs on the SDP part of the message
is proportional to the number of program listings in the Content Manager (each program listing can
have at least six embedded IP addresses).
•
You can configure NAT for Apple QuickTime 4 or RealPlayer. Cisco IP/TV only works with NAT
if the Viewer and Content Manager are on the outside network and the server is on the inside
network.
•
When using RealPlayer, it is important to properly configure transport mode. For the FWSM, add
an access-list command statement from the server to the client or vice versa. For RealPlayer, change
transport mode by clicking Options>Preferences>Transport>RTSP Settings.
If you use TCP mode on the RealPlayer, select the Use TCP to Connect to Server and Attempt to
use TCP for all content check boxes. On the FWSM, there is no need to configure the inspection
engine.
If you use UDP mode on the RealPlayer, select the Use TCP to Connect to Server and Attempt to
use UDP for static content check boxes. On the FWSM, configure the RTSP inspection engine.
SIP Inspection Engine
Enabled by default for TCP and UDP port 5060
Session Initiation Protocol (SIP), as defined by the Internet Engineering Task Force (IETF), enables call
handling sessions, particularly two-party audio conferences, or “calls.”
This section includes the following topics:
•
Configuring the SIP Inspection Engine, page 13-16
•
SIP Overview, page 13-17
•
Technical Background, page 13-17
Configuring the SIP Inspection Engine
To configure the SIP inspection engine, enter the following commands:
•
To configure the SIP TCP inspection engine, enter the following command:
FWSM/contexta(config)# fixup protocol sip [port[-port]]
The default port is 5060 (TCP).
•
To configure the SIP UDP inspection engine, enter the following command:
FWSM/contexta(config)# fixup protocol sip udp
The default port is 5060 (UDP), which is the only port allowed.
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SIP Overview
SIP works with Session Description Protocol (SDP) for call signalling. SDP specifies the ports for the
media stream. The inspection engine supports the following SIP message types. Other message types are
allowed through the FWSM, but they are not inspected.
•
Messages in RFC 2543 (redefined in RFC 3261):
– INVITE
– ACK
– BYE
– CANCEL
– REGISTER
– Responses 1xx, 2xx, 3xx, 4xx, 5xx, 6xx
•
Message in RFC 2976:
– INFO
•
Messages in RFC 3265:
– SUBSRIBE
– NOTIFY
•
Message in RFC 3428:
– MESSAGE
To support SIP calls through the FWSM, the FWSM inspects signaling messages for the media
connection addresses, media ports, and embryonic connections for the media, because while the
signaling is sent over a well-known destination port (UDP/TCP 5060), the media streams are
dynamically allocated. Also, SIP embeds IP addresses in the user-data portion of the IP packet. The SIP
inspection engine applies NAT for these embedded IP addresses. It does not support NAT between same
security interfaces or outside NAT.
Technical Background
The SIP inspection engine NATs the SIP text-based messages, recalculates the content length for the
SDP portion of the message, and recalculates the packet length and checksum. It dynamically opens
media connections for ports specified in the SDP portion of the SIP message as address/ports on which
the endpoint should listen.
The SIP inspection engine has a database that keeps track of information from the SIP payload that
identifies the call, as well as the source and destination. Contained within this database are the media
addresses and media ports that were contained in the SDP media information fields and the media type.
There can be multiple media addresses and ports for a session. RTP/RTCP connections are opened
between the two endpoints using these media addresses/ports. The well-known port 5060 must be used
on the initial call setup (INVITE) message. However, subsequent messages may not have this port
number. The SIP inspection engine opens signaling connection pinholes, and marks these connections
as SIP connections. This is done for the messages to reach the SIP application and be NATed.
As a call is set up, the SIP session is considered in the “transient” state until the media address and media
port is received in a Response message from the called endpoint indicating the RTP port the called
endpoint will listen on. If there is a failure to receive the response messages within one minute, the
signaling connection will be torn down.
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Once the final handshake is made, the call state is moved to active and the signaling connection will
remain until a BYE message is received.
If an inside endpoint initiates a call to an outside endpoint, a media hole is opened to the outside interface
to allow RTP/RTCP UDP packets to flow to the inside endpoint media address and media port specified
in the INVITE message from the inside endpoint. Unsolicited RTP/RTCP UDP packets to an inside
interface will not traverse the FWSM, unless the FWSM configuration specifically allows it.
The media connections are torn down within two minutes after the connection becomes idle. This is,
however, a configurable timeout and can be set for a shorter or longer period of time. See the timeout
command in the Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module
Command Reference.
Skinny Inspection Engine
Enabled by default for TCP port 2000
Skinny (or Simple) Client Control Protocol (SCCP) is a protocol used in VoIP networks.
To configure the Skinny inspection engine, enter the following command:
FWSM/contexta(config)# fixup protocol skinny [port[-port]]
The default port is 2000 (TCP).
This section includes the following topics:
•
Skinny Overview, page 13-18
•
Problems with Fragmented Skinny Packets, page 13-19
Skinny Overview
Cisco IP Phones using Skinny can coexist with an H.323 environment. When used with
Cisco CallManager, the Skinny client can interoperate with H.323-compliant terminals. The FWSM
ensures that all SCCP signalling and media packets can traverse the FWSM by providing NAT of the
SCCP Signaling packets. This inspection engine does not support NAT between same security interfaces.
There are 5 versions of the SCCP protocol supported: 2.4, 3.0.4, 3.1.1, 3.2, and 3.3.2.
The FWSM supports DHCP options 150 and 66, which allow the FWSM to send the location of a TFTP
server to Cisco IP Phones and other DHCP clients. The TFTP server provides the address of the
Cisco CallManager for the Cisco IP Phones. For further information about this feature, see the
“Configuring the DHCP Server” section on page 8-19. If the Cisco CallManager is on a higher security
interface, which requires NAT for the Cisco CallManager IP address, and you configure the TFTP server
to serve a file with the local untranslated address of the Cisco CallManager, then the Cisco IP Phones
cannot contact the Cisco CallManager. We recommend that you use the Cisco CallManager name instead
of the IP address, and rely on the DNS server to provide the correct address. If the DNS server is also on
the higher security interface, the FWSM can use the DNS inspection engine to translate the address
inside the DNS response.
If you enter the clear xlate command after PAT translations are created for Cisco CallManager, Skinny
calls cannot be established because the translations for the Cisco CallManager are permanently deleted.
Under these circumstances, Cisco IP Phones need to reregister with the Cisco CallManager to establish
calls through the FWSM.
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Detailed Information About Inspection Engines
Problems with Fragmented Skinny Packets
The FWSM does not correctly handle fragmented Skinny packets. For instance, when using a voice
conferencing bridge, Skinny packets might become fragmented and are then dropped by the FWSM. This
happens because the Skinny inspection engine checks each packet and drops what appear to be bad
packets. When a single Skinny packet is fragmented into multiple TCP packets, the Skinny inspection
engine finds that the internal checksums within the Skinny packet fragments are not correct and so it
drops the packet.
SMTP Inspection Engine
Enabled by default for TCP port 25
The SMTP inspection engine enables the Mail Guard feature. This restricts mail servers to receiving the
seven minimal commands defined in RFC 821, section 4.5.1 (HELO, MAIL, RCPT, DATA, RSET,
NOOP, and QUIT). All other commands are rejected.
Microsoft Exchange server does not strictly comply with RFC 821 section 4.5.1, using extended SMTP
commands such as EHLO. The FWSM converts any such commands into NOOP commands, which as
specified by the RFC, forces SMTP servers to fall back to using minimal SMTP commands only. This
might cause Microsoft Outlook clients and Exchange servers to function unpredictably when their
connection passes through FWSM. In this case, you might want to disable the SMTP inspection engine,
although the Mail Guard feature does provide valuable protection.
To configure the SMTP inspection engine, enter the following command:
FWSM/contexta(config)# fixup protocol smtp [port[-port]]
The default port is 25 (TCP).
An SMTP server responds to client requests with numeric reply codes and optional human-readable
strings. The SMTP inspection engine controls and reduces the commands that the user can use as well
as the messages that the server returns. The SMTP inspection engine performs three primary tasks:
•
Restricts SMTP requests to seven minimal commands (HELO, MAIL, RCPT, DATA, RSET, NOOP,
and QUIT).
•
Changes the characters in the server SMTP banner to asterisks except for the “2”, “0”, “0”
characters. Carriage return (CR) and linefeed (LF) characters are ignored.
•
Monitors the SMTP command-response sequence.
•
Generates an audit trail—Audit record 108002 is generated when an invalid character embedded in
he mail address is replaced. For more information, see RFC 821.
t
The SMTP inspection engine monitors the command and response sequence for the following anomalous
signatures:
•
Truncated commands.
•
Incorrect command termination (not terminated with <CR><LR>).
•
The MAIL and RCPT commands specify who are the sender and the receiver of the mail. Mail
addresses are scanned for strange characters. The pipeline character (|) is deleted (changed to a blank
space) and “<” ‚”>” are only allowed if they are used to define a mail address (“>” must be preceded
by “<”).
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•
Unexpected transition by the SMTP server.
•
For unknown commands, the FWSM changes all the characters in the packet to X. In this case, the
server will generate an error code to the client. Because of the change in the packet, the TCP
checksum has to be recalculated.
•
TCP stream editing.
•
Command pipelining.
SQL*Net Inspection Engine
Enabled by default for TCP port 1521
The SQL*Net protocol consists of different packet types that the FWSM handles to make the data stream
appear consistent with the Oracle applications on either side of the FWSM.
To configure the SQL*Net inspection engine, enter the following command:
FWSM/contexta(config)# fixup protocol sqlnet [port[-port]]
The default port is 1521 (TCP).
The FWSM NATs all addresses and looks in the packets for all embedded ports to open for SQL*Net
Version 1.
For SQL*Net Version 2, all DATA or REDIRECT packets that immediately follow REDIRECT packets
with a zero data length are fixed up.
The packets that need inspection engine contain embedded host/port addresses in the following format:
(ADDRESS=(PROTOCOL=tcp)(DEV=6)(HOST=a.b.c.d)(PORT=a))
SQL*Net Version 2 TNSFrame types (Connect, Accept, Refuse, Resend, and Marker) are not scanned
for addresses to NAT, nor does the inspection engine open dynamic connections for any embedded ports
in the packet.
SQL*Net Version 2 TNSFrames, Redirect, and Data packets are scanned for ports to open and addresses
to NAT, if preceded by a REDIRECT TNSFrame type with a zero data length for the payload. When the
Redirect message with data length zero passes through the FWSM, a flag is set in the connection data
structure to expect the Data or Redirect message that follows is NATed and ports are dynamically
opened. If one of the TNS frames in the preceding paragraph arrives after the Redirect message, the flag
is reset.
The SQL*Net inspection engine recalculates the checksum, change IP, TCP lengths, and readjusts
Sequence Numbers and Acknowledgment Numbers using the delta of the length of the new and old
message.
SQL*Net Version 1 is assumed for all other cases. TNSFrame types (Connect, Accept, Refuse, Resend,
Marker, Redirect, and Data) and all packets are scanned for ports and addresses. Addresses are NATed
and port connections are opened.
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Sun RPC Inspection Engine
Enabled by default for UDP port 111
Sun Remote Procedure Call (RPC) is used by many services, for example, Network File System (NFS)
and Network Information Service (NIS).
Sun RPC services can run on any port on the system. When a client attempts to access an RPC service
on a server, it must find out which port that service is running on. It does this by querying the portmapper
process on the well-known port of 111.
The client sends the RPC program number of the service, and gets back the port number. From this point
on, the client program sends its RPC queries to that new port.
When a server sends out a reply, the FWSM intercepts this packet and opens both embryonic TCP and
UDP connections on that port for a short period of time. After the client connects to the port and makes
a full connection, the embryonic connection goes away. For additional connections from the client to the
port, the client must repeat the portmapper process. Alternatively, you can configure the FWSM to keep
the embryonic connections open for a longer period of time so that clients can use cached port numbers
and do not have to repeat the portmapper process. This method is required for Sun RPC over TCP; only
the default inspection for UDP uses the above method. See the rpc-server command below.
NAT or PAT of RPC payload information is not supported. Use NAT exemption or identity NAT.
•
To configure the Sun RPC inspection engine for TCP, enter the following command:
FWSM/contexta(config)# fixup protocol rpc [port[-port]]
The default port is 111 (TCP). You must also configure the rpc-server command (below). The UDP
inspection engine is on by default and is not configurable.
•
To allow clients to use cached port numbers for Sun RPC services (such as NFS or NIS), enter the
following command:
FWSM/contexta(config)# rpc-server interface_name ip_address mask service service_type
protocol {tcp | udp} port[-port] timeout hh:mm:ss
After a client initially connects to a server running a Sun RPC service, the client might cache the
Sun RPC port information supplied by the portmapper process. Additional connections from the
client might use these cached ports. This command allows clients to use cached port numbers for
the duration of the specified timeout rather than have to re-request the port numbers from the
portmapper process. This command is required for Sun RPC over TCP.
TFTP Inspection Engine
Enabled by default for UDP port 69
Not Configurable
The FWSM permits all UDP connections from a TFTP server back to a client source port if there is an
existing TFTP connection between the server and client.
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XDMCP Inspection Engine
Enabled by default for UDP port 177
Not Configurable
The port assignment for the X Display Manager Control Protocol (XDMCP) is not configurable.
XDMCP is a protocol that uses UDP port 177 to negotiate X sessions, which use TCP when established.
For successful negotiation and as the start of an Xwindows session, the FWSM must allow the TCP back
connection. Once XDMCP negotiates the session, a single embryonic connection is created to handle the
initial TCP connection, after which the established rule is consulted.
During the X Windows session, the manager talks to the display's Xserver on the well-known port 6000
+ n. Each display has a separate connection to the Xserver as a result of the following terminal setting:
setenv DISPLAY Xserver:n
where n is the display number.
When XDMCP is used, the display is negotiated using IP addresses, which the FWSM can NAT if
needed. The XDCMP inspection engine does not support PAT.
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14
Filtering HTTP, HTTPS, or FTP Requests Using an
External Server
This section tells how to enable HTTP, HTTPS, or FTP filtering for inside users, and contains the
following topics:
•
Filtering Overview, page 14-1
•
Configuring General Filtering Parameters, page 14-2
•
Filtering HTTP URLs, page 14-5
•
Filtering HTTPS URLs, page 14-6
•
Filtering FTP Requests, page 14-6
•
Viewing Filtering Statistics, page 14-6
Filtering Overview
Although you can use ACLs 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 Firewall Services Module (FWSM) in conjunction with a separate server
running one of the following Internet filtering products:
•
Websense Enterprise—http://www.websense.com. Supports HTTP, HTTPS, and FTP filtering.
•
Sentian by N2H2—http://www.n2h2.com. Supports HTTP filtering. Although some versions of
Sentian support HTTPS, the FWSM only supports HTTP with Sentian.
Because URL filtering is handled on a separate platform, the performance of the FWSM is less affected.
However, filtering can considerably increase access times to websites or FTP servers when the filtering
server is remote from the FWSM.
When a user issues an HTTP, HTTPS, or FTP GET request, the FWSM sends the request to the web/FTP
server as well as to the filtering server at the same time. If the filtering server permits the connection for
the user, then the following action occurs for each request type:
•
For HTTP, the FWSM allows the reply from the web server to reach the user who issued the original
request.
•
For HTTPS, the FWSM allows the completion of SSL connection negotiation, and allows the reply
from the web server to reach the user who issued the original request.
•
For FTP, the FWSM allows the successful FTP return code to reach the user unchanged. For
example, a successful return code is “250: CWD command successful.”
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Configuring General Filtering Parameters
If the filtering server denies the connection, then the following action occurs for each request type:
•
For HTTP, the FWSM redirects the user to a block page, indicating that access was denied.
•
For HTTPS, the FWSM prevents the completion of SSL connection negotiation. The browser
displays an error message such as “The Page or the content cannot be displayed.”
•
For FTP, the FWSM alters the FTP return code to show that the connection was denied. For example,
the FWSM changes code 250 to “code 550: Directory not found.”
For N2H2, if you enabled user authentication on the FWSM for HTTP, HTTPS, or FTP, then the FWSM
also sends the username to the filtering server. The filtering server can then use user-specific filtering
settings or provide enhanced reporting per user. See the “Configuring Authentication for Network
Access” section on page 12-20 to configure user authentication. Websense supports filtering by
IP address only.
Filtering applies only for outbound connections (from a higher security interface to a lower security
interface) or between same security interfaces.
Configuring General Filtering Parameters
This section describes how to configure the FWSM to communicate with the filtering server and how to
handle requests when the filtering server is down, how to handle long URLs, and whether to cache server
addresses. This section includes the following topics:
•
Identifying the Filtering Server, page 14-2
•
Buffering Replies, page 14-3
•
Setting the Maximum Length of Long HTTP URLs, page 14-4
•
Caching URL Servers, page 14-4
Identifying the Filtering Server
You can identify up to four filtering servers per context. The FWSM uses the servers in order until a
server responds. You can only configure one type of server (Websense or N2H2) in your configuration.
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.
To identify the filtering server(s), enter one of the following commands for each server you want to
identify. Only one type of server is allowed in your configuration.
•
To identify a Websense Enterprise server, enter the following command:
FWSM/contexta(config)# url-server (if_name) vendor websense host ip_address
[timeout seconds] [protocol tcp [version {1 | 4}] | udp]
See the following options:
– (if_name)—The interface through which the FWSM communicates with the server.
– ip_address—The Websense server IP address.
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– timeout seconds—The number of seconds between 10 and 120 before the FWSM stops trying
to connect to the server, and attempts to connect to the next server in the list (if available). The
default is 30 seconds.
– protocol tcp [version {1 | 4}]—Specifies that communication between the FWSM and the
Websense server uses TCP, which is the default protocol. We recommend version 4, although
version 1 is the default. Version 4 allows the FWSM to send authenticated usernames to the
Websense server and to support URL caching.
– protocol udp—Specifies UDP, which has greater throughput, but which does not support long
URLs.
•
To identify an N2H2 Sentian server, enter the following command:
FWSM/contexta(config)# url-server (if_name) vendor n2h2 host ip_address [port number]
[timeout <seconds>] [protocol {tcp | udp}]
See the following options:
– (if_name)—The interface through which the FWSM communicates with the server.
– ip_address—The N2H2 server IP address.
– port number—The port used to communicate with the N2H2 server. The default is 4005 for
TCP or UDP. Change this value if you change the port on the N2H2 server.
– timeout seconds—The number of seconds between 10 and 120 before the FWSM stops trying
to connect to the server, and attempts to connect to the next server in the list (if available). The
default is 30 seconds.
– protocol {tcp | udp}—Specifies the protocol used for communication between the FWSM and
the N2H2 server. TCP is the default protocol, and is recommended.
For example, to identify redundant Sentian servers, enter:
FWSM/contexta(config)# url-server (perimeter) vendor n2h2 host 10.0.1.1
FWSM/contexta(config)# url-server (perimeter) vendor n2h2 host 10.0.1.2
Buffering Replies
By default, when a user issues a request to connect to a website or FTP server, the FWSM sends the
request to the web/FTP server and to the filtering server at the same time. If the filtering server does not
respond before the web/FTP server, the reply from the web/FTP server is dropped.
To avoid dropping traffic, you can configure the FWSM to buffer replies from web and FTP servers.
When the filtering server eventually responds, the FWSM can allow the connection.
To enable buffering, enter the following command:
FWSM/contexta(config)# url-block block block-buffer-limit
The block-buffer-limit sets the amount of memory assigned to the buffer from 0 to 128 blocks. Each
block is 1550 bytes.
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Configuring General Filtering Parameters
Setting the Maximum Length of Long HTTP URLs
Websense only
By default, the FWSM considers an HTTP URL to be a long URL if it is greater than 1159 characters.
If the URL exceeds the maximum size, then it is dropped by default. You can set the FWSM to truncate
or block a long URL when you configure HTTP filtering. (See the “Filtering HTTP URLs” section on
page 14-5.)
To increase the maximum length and to set the amount of memory used for long URLs, follow these
steps:
Step 1
To change the limit for long URLs from 1159 bytes (characters), enter the following command:
FWSM/contexta(config)# url-block url-size long-url-size
Enter 2, 3, or 4 to change the limit to 2, 3, or 4 KB.
Step 2
To set the maximum memory available for buffering long URLs, enter the following command:
FWSM/contexta(config)# url-block url-mempool memory-pool-size
The amount of memory dedicated to long URLs is limited to avoid a DoS attack, for example.
Set the size from 2 to 10240 KB. Typically, the amount of memory should be the number of sessions you
want to allow times the maximum length of the URL. For example, to allow 100 sessions for 3 KB URLs,
then set the memory to be 300 KB. However, we recommend setting the memory to the maximum,
10240 KB, because the FWSM has enough memory to handle the maximum number of sessions.
Caching URL Servers
After a user accesses a site, the filtering server can allow the FWSM 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 FWSM
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.
To enable caching, enter the following command:
FWSM/contexta(config)# url-cache {dst | src_dst} kbytes
See the following options:
•
dst—Caches the destination server address for any user that accesses the server.
•
src_dst— Caches the source and destination server address, so access is only cached for a given user
at the source address.
•
kbytes—The cache size between 1 and 128 KB.
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Filtering HTTP URLs
Filtering HTTP URLs
To filter HTTP web access for specified users, or to exempt some traffic from filtering, enter the
following commands:
•
To identify HTTP traffic to be filtered by a filtering server, enter the following command:
FWSM/contexta(config)# filter url [http | port[-port]] source_ip source_mask dest_ip
dest_mask [allow] [proxy-block] [longurl-truncate | longurl-deny] [cgi-truncate]
See the following options:
– http | port[-port]—The port to which the HTTP request is sent. http specifies port 80, which is
commonly used, but you can specify other ports.
– source_ip source_mask—The source address and mask. Specify 0 0 for all addresses. These
addresses are the local, untranslated addresses. When you configure the filtering server, use
these local addresses and not the translated addresses.
– dest_ip dest_mask—The destination server address and mask. Specify 0 0 for all addresses. You
typically specify all addresses and allow the filtering server to determine the websites that are
allowed.
– allow—When the filtering server is unavailable, this option allows connections to pass without
filtering. Without this option, the FWSM stops HTTP traffic until the filtering server is back
online.
– proxy-block—Prevents users from connecting to an HTTP proxy server.
– longurl-truncate | longurl-deny—By default, if a URL is longer than the maximum length
then the FWSM drops the packet. (The default maximum length is 1159 bytes, but can be made
larger for Websense. See the “Setting the Maximum Length of Long HTTP URLs” section on
page 14-4). If you specify the longurl-truncate option, the FWSM sends the host name or IP
address portion of the URL for evaluation to the filtering server. The longurl-deny option
denies the URL, and forwards the user to the block page.
– cgi-truncate—Truncates CGI URLs to include only the CGI script location and the script name
(but not 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 waste
memory resources and impact performance.
•
To exempt traffic from being filtered, enter the following command:
FWSM/contexta(config)# filter url except source_ip source_mask dest_ip dest_mask
For example, to filter all HTTP requests from the 10.1.1.0 network to any web server, but to exempt an
administrator user (10.1.1.1) from filtering, enter the following commands:
FWSM/contexta(config)# filter url except 10.1.1.1 255.255.255.255 0 0
FWSM/contexta(config)# filter url http 10.1.1.0 255.255.255.0 0 0 longurl-truncate
cgi-truncate
To filter users only on the 10.1.2.0 network, enter the following commands:
FWSM/contexta(config)# filter url http 10.1.2.0 255.255.255.0 0 0
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Filtering HTTPS URLs
Filtering HTTPS URLs
Websense only
To filter HTTPS web access for specified users, enter the following command:
FWSM/contexta(config)# filter https source_ip source_mask dest_ip dest_mask [allow]
HTTPS content is encrypted, so the FWSM sends the URL lookup to the filtering server without
directory and filename information.
For the source addresses, specify the local, untranslated addresses. When you configure the filtering
server, use these local addresses and not the translated addresses.
When the filtering server is unavailable, the allow keyword allows connections to pass without filtering.
Without this option, the FWSM stops HTTPS traffic until the filtering server is back online.
Filtering FTP Requests
Websense only
To enable FTP filtering, enter the following command:
FWSM/contexta(config)# filter ftp port source_ip source_mask dest_ip dest_mask [allow]
[interact-block]
Websense only filters FTP GET commands and not PUT commands.
For the source addresses, specify the local, untranslated addresses. When you configure the filtering
server, use these local addresses and not the translated addresses.
When the filtering server is unavailable, use the allow keyword allows connections to pass without
filtering. Without this option, the FWSM stops FTP traffic until the filtering server is back online.
The interactive-block keyword prevents interactive FTP sessions that do not provide the entire directory
path. An interactive FTP client is a non-browser client such as the ftp command from a DOS prompt or
a UNIX shell prompt, or a stand alone FTP client. For example, when you use a web browser for FTP
and you browse to a file, the URL for the file includes the entire path. When you use the ftp command
at the command line, you can change directories without typing the entire path (cd ./files instead of cd
/public/files), in which case the firewall cannot determine your exact location.
Viewing Filtering Statistics
This section describes how to monitor filtering statistics, and includes the following topics:
•
Viewing Filtering Server Statistics, page 14-7
•
Viewing Caching Statistics, page 14-7
•
Viewing Filtering Performance Statistics, page 14-8
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Viewing Filtering Statistics
Viewing Filtering Server Statistics
To show information about the filtering server or to show statistics, enter the following command:
FWSM/contexta# show url-server stats
The following sample display shows filtering statistics:
FWSM/contexta# show url-server stats
URL Server Statistics:
---------------------Vendor
websense
URLs total/allowed/denied
50/35/15
HTTPSs total/allowed/denied
1/1/0
FTPs total/allowed/denied
3/1/2
URL Server Status:
-----------------10.130.28.18
UP
URL Packets Sent and Received Stats:
----------------------------------Message
Sent
Received
STATUS_REQUEST
65155
34773
LOOKUP_REQUEST
0
0
LOG_REQUEST
0
NA
-----------------------------------
Viewing Caching Statistics
To show URL caching statistics, enter the following command:
FWSM/contexta# show url-cache stats
The following sample display shows how the cache is used:
FWSM/contexta# show url-cache stats
URL Filter Cache Stats
---------------------Size :
128KB
Entries :
1724
In Use :
456
Lookups :
45
Hits :
8
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Viewing Filtering Statistics
Viewing Filtering Performance Statistics
To show URL filtering performance statistics (as well as other performance statistics), enter the
following command:
FWSM/contexta# show perfmon
The following sample display shows filtering statistics in the URL Access and URL Server Req rows:
FWSM/contexta# 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
FTP Fixup
0/s
AAA Authen
0/s
AAA Author
0/s
AAA Account
0/s
Average
0/s
2/s
2/s
0/s
2/s
3/s
0/s
0/s
3/s
0/s
0/s
0/s
0/s
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Using Failover
This chapter describes the Firewall Services Module (FWSM) failover feature, which allows a secondary
FWSM to take over the functionality of a failed FWSM. This chapter includes the following sections:
•
Understanding Failover, page 15-1
•
Configuring Failover, page 15-15
•
Verifying the Failover Configuration, page 15-19
•
Forcing Failover, page 15-23
•
Disabling Failover, page 15-23
•
Monitoring Failover, page 15-23
•
Frequently Asked Failover Questions, page 15-24
•
Failover Configuration Example, page 15-27
Note
See the “Configuring the Switch for Failover” section on page 2-11 to configure the switch for failover.
Note
In this chapter, the term “standby” signifies the redundant module in standby mode.
Understanding Failover
This section describes how failover works and includes the following sections:
•
Failover Overview, page 15-2
•
Regular and Stateful Failover, page 15-2
•
Failover and State Links, page 15-3
•
Module Placement, page 15-4
•
Transparent Firewall Requirements, page 15-9
•
Primary/Secondary Status and Active/Standby Status, page 15-10
•
Configuration Replication, page 15-10
•
Failover Triggers, page 15-12
•
Failover Actions, page 15-12
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Using Failover
Understanding Failover
•
Failover Monitoring, page 15-13
Failover Overview
The failover feature lets you use a standby FWSM to take over the functionality of a failed FWSM.
Failover is compatible with both routed and transparent firewall modes, and with single and
multiple context modes.
Note
The two FWSMs must have the same major (first number) and minor (second number) software version,
license, and operating modes (routed or transparent, single or multiple context). You can use different
maintenance versions (third numbers) during an upgrade process; for example, you can upgrade one
module from 2.2(1) to 2.2(2) and failover is still active. However, we recommend upgrading both
modules to the same version to ensure long-term compatibility. We do not guarantee full compatibility
for failover when the maintenance versions differ.
When the active module fails, it changes to the standby state, while the standby module changes to the
active state.
The module that becomes active takes over the active module IP addresses (or, for transparent firewall,
the management IP address) and MAC address, and it begins passing traffic. The FWSM has one MAC
address for all interfaces. The module that was active and is now in standby state takes over the standby
IP addresses and MAC address.
Because network devices see no change in the MAC to IP address pairing, failover is unnoticed by the
rest of the network. However, the host switch needs to reassociate the new active and standby chassis
slots with their corresponding MAC addresses. The FWSM helps this process by sending out gratuitous
ARPs on all its VLAN interfaces. (See the “Primary/Secondary Status and Active/Standby Status”
section on page 15-10 section for more information about MAC addresses).
The standby module can effectively take over as the active module because it has the same configuration,
and it is assigned the same VLANs from the switch.
Note
For multiple context mode, the FWSM can fail over the entire module (including all contexts) but cannot
fail over individual contexts separately.
Regular and Stateful Failover
The FWSM supports two types of failover:
•
Regular failover—When a failover occurs, all active connections are dropped and clients need to
reestablish connections when the new active module takes over.
•
Stateful failover—During normal operation, the active module continually passes per-connection
stateful information (for each context) to the standby module. The interval between stateful
information updates is 10 seconds, but if you set the module polltime to be greater than 10 seconds,
then that interval is used.
After a failover occurs, the same connection information is available at the new active module.
Supported end-user applications are not required to reconnect to keep the same communication
session.
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The state information passed to the standby module includes the following data:
– NAT translation table
– TCP connection states
– UDP connection states (for connections lasting at least 15 seconds)
– HTTP connection states (Optional)
– H.323, SIP, and MGCP UDP media connections
– ARP table
– (Transparent firewall mode only) MAC address table
Failover and State Links
This section describes the failover link and, for stateful failover, the state link, and it includes the
following topics:
•
Failover Link, page 15-3
•
State Link, page 15-3
Failover Link
The two modules constantly communicate over a failover link to determine the operating status of each
module. Communications over the failover link include the following data:
•
The module state (active or standby).
•
Hello messages (also sent on all other interfaces).
•
Configuration synchronization between the two modules. (See the “Configuration Replication”
section on page 15-10 section for more information.)
The failover link uses a special VLAN interface that you do not configure as a normal networking
interface; rather, it exists only for failover communications. This VLAN should only be used for the
failover link (and optionally for the state link).
For multiple context mode, the failover link resides in the system configuration. This interface (and the
state link, if used) is the only configurable interface in the system configuration.
Note
The IP address and MAC address for the failover link do not change at failover.
State Link
To use stateful failover, configure a state link to pass all state information. This link can be the same as
the failover link, but we recommend that you assign a separate VLAN and IP address for the state link.
The state traffic can be large, and performance is improved with separate links.
In multiple context mode, the state link resides in the system configuration. This interface and the
failover interface are the only interfaces in the system configuration.
Note
The IP address and MAC address for the state link do not change at failover.
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Module Placement
You can place the primary and secondary FWSMs within the same switch or in two separate switches.
The following sections describe each option:
•
Intra-Chassis Failover, page 15-4
•
Inter-Chassis Failover, page 15-4
Intra-Chassis Failover
If you install the secondary FWSM in the same switch as the primary FWSM, you protect against
module-level failure. To protect against switch-level failure, as well as module-level failure, see the
“Inter-Chassis Failover” section on page 15-4.
Even though both FWSMs are assigned the same VLANs, only the active module takes part in
networking. The standby module does not pass any traffic.
Figure 15-1 shows a typical intra-switch configuration.
Figure 15-1 Intra-Switch Failover
Internet
VLAN 100
Switch
VLAN 200
Failover VLAN 10
Standby
FWSM
Active
FWSM
Inside
104650
State VLAN 11
VLAN 201
Inter-Chassis Failover
To protect against switch-level failure, you can install the secondary FWSM in a separate switch. The
FWSM does not coordinate failover directly with the switch, but it works harmoniously with the switch
failover operation. See the switch documentation to configure failover for the switch.
To accommodate the failover communications between the FWSMs, you must configure a trunk port
between the two switches that carries all the FWSM VLANs. Because this trunk also accommodates
FWSM traffic when a module fails, this trunk should be at least as large as the maximum amount of
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traffic you expect to be inspected by the FWSM. The FWSM has an internal 6-Gbps EtherChannel to the
switch, so if the FWSM runs at full capacity, the trunk between the two devices needs to include at least
six 1-Gbps interfaces. EtherChannel aggregates the bandwidth of up to eight compatibly configured
ports into a single logical link. (See the “Adding a Trunk Between a Primary Switch and Secondary
Switch” section on page 2-12 for more information.)
Figure 15-2 shows a typical switch and FWSM redundancy configuration. The Spanning Tree algorithm
ensures that the VLANs pass through only one switch, which also contains the active FWSM. The trunk
between the two switches carries all FWSM VLANs, including the failover and state links (VLANs 10
and 11).
Note
The FWSM failover is independent of the switch failover operation; however, the FWSM works in any
switch failover scenario.
Figure 15-2 Normal Operation with Standby Modules
Internet
VLAN 100
Active Switch
Standby Switch
VLAN 200
Failover Links:
VLAN 10
Active
FWSM
Trunk:
VLANs 200, 201,
202, 203, 10, 11
VLAN 203
VLAN 11
Standby
FWSM
Eng
Mktg
Inside
104652
VLAN 202
VLAN 201
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The path that the traffic takes after failover depends on which device fails as follows:
•
FWSM failure only—If the primary FWSM fails, then the secondary FWSM becomes active.
However, if the primary switch is still active, all VLAN traffic destined for the FWSM continues to
enter the primary switch. The secondary (now active) FWSM receives and sends all traffic over the
trunk (Figure 15-3).
Figure 15-3 FWSM Failure Only
Internet
VLAN 100
Active Switch
Standby Switch
Failover Links:
VLAN 11
VLAN 10
VLAN 200
Standby
FWSM
Trunk:
VLANs 200, 201,
202, 203, 10, 11
Active
FWSM
Eng
VLAN 203
Mktg
Inside
VLAN 201
104651
VLAN 202
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•
Switch/FWSM failure—If the entire switch fails, as well as the FWSM (such as in a power failure),
then both the switch and the FWSM fail over to their secondary modules (Figure 15-4).
Figure 15-4 Switch/FWSM Failure
Internet
VLAN 100
Standby Switch
Active Switch
VLAN 200
Trunk
Active
FWSM
Standby
FWSM
Eng
VLAN 203
Mktg
Inside
VLAN 201
104654
VLAN 202
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•
Partial switch failure—If one or more interfaces on the switch fails, both switches would be partially
active, but only one FWSM is active. The FWSM, which operates independently of the switch, has
no reason to fail over because the active FWSM receives FWSM traffic from the secondary switch
over the trunk (Figure 15-5).
Figure 15-5 Partial Switch Failure
Internet
VLAN 100
Active Switch
Active Switch
VLAN 200
Failover Links:
VLAN 10
Trunk:
VLANs 200, 201,
202, 203, 10, 11
Active
FWSM
VLAN 203
VLAN 11
Standby
FWSM
Eng
Mktg
104653
VLAN 202
Inside
VLAN 201
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•
Trunk failure—If the trunk between the switches fails, all communication between the FWSMs
terminates, which results in both FWSMs becoming active. Spanning Tree prevents any loops,
however, and traffic is handled successfully by one or both FWSMs until you resolve the trunk issue
(Figure 15-6).
Figure 15-6 Trunk Failure
Internet
VLAN 100
Active Switch
Active Switch
No Trunk
No Failover
Links
VLAN 200
Active
FWSM
Active
FWSM
Eng
VLAN 203
Mktg
Inside
VLAN 201
104648
VLAN 202
Transparent Firewall Requirements
To avoid loops when you use failover in transparent mode, you must use switch software that supports
BPDU forwarding, and you must configure the FWSM to allow BPDUs. See the “Chassis System
Requirements” section on page 1-2 for switch software versions that allow BPDUs automatically.
To allow BPDUs through the FWSM, configure an EtherType ACL and apply it to both interfaces
according to the “Adding an EtherType Access Control List” section on page 10-16.
Loops can occur if both modules are active at the same time, such as when both modules are discovering
each other’s presence, or due to a bad failover link as described in the “Basic Failover Questions” section
on page 15-25. Because the FWSMs bridge packets between the same two VLANs, loops can occur
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when inside packets destined for the outside get endlessly replicated by both FWSMs (see Figure 15-7).
The spanning tree protocol can break such loops if there is a timely exchange of BPDUs. To break the
loop, BPDUs sent between VLAN 200 and VLAN 201 need to be bridged.
Figure 15-7 Potential Loops in Transparent Mode
Internet
MSFC
VLAN 200
Failover VLAN 10
Active
FWSM
Active
FWSM
State VLAN 11
Inside
104894
VLAN 201
Primary/Secondary Status and Active/Standby Status
The main differences between the two modules in a failover pair are related to which module is active
and which module is standby, namely which IP addresses to use and which module actively passes
traffic.
However, a few differences exist between the modules based on which module is primary (as specified
in the configuration) and which module is secondary:
•
The primary module always becomes the active module if both modules start up at the same time
(and are of equal operational health).
•
The primary modulemodule MAC address is always coupled with the active IP addresses. The
exception to this rule occurs when the secondary module is active, and cannot obtain the primary
MAC address over the failover link. In this case, the secondary MAC address is used.
Configuration Replication
The two FWSM modules share almost the identical configuration. The configuration can be the same
because it includes both the active IP addresses and the standby IP addresses. When a module is active,
it uses the active IP addresses; when a module is standby, it uses the standby IP addresses.
Note
Because the configuration is the same on both modules, the host names, usernames, and passwords are
also the same.
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The only difference in the configuration is the primary and secondary designation, although you must
also pre-configure the failover link on the secondary module before the modules can communicate. All
other configuration is automatically replicated from the active to the standby module.
Note
You can suspend the the configuration replication process using the failover suspend-config-sync
command. See the “Disabling Configuration Synchronization” section on page 15-12.
The active module sends the configuration in running memory to the standby module. On the standby
module, the configuration exists only in running memory. You can optionally save the configuration to
Flash memory so that when you reboot the standby module when the active module is unavailable, the
standby module can become the active module. To save the configuration to Flash memory after
replication:
•
For single context mode, enter the copy running-config startup-config command on the active
module. The command is replicated to the standby module, which proceeds to write its configuration
to Flash memory.
•
For multiple context mode, enter the copy running-config startup-config command on the active
module from the system execution space and within each context on disk. The command is
replicated to the standby module, which proceeds to write its configuration to Flash memory.
Contexts with startup configurations on external servers are accessible from either module over the
network and do not need to be saved separately for each module. Alternatively, you can copy the
contexts on disk from the active module to an external server, and then copy them to disk on the
standby module. (See the “Downloading a Text Configuration” section on page 16-6 for more
information.)
Configuration replication from the active module to the standby module occurs in the following
circumstances:
•
When the standby module completes its initial startup, it clears its running configuration (except for
the failover commands that must be pre-configured and are not replicated), and the active module
sends its entire configuration to the standby module.
•
As commands are entered on the active module, they are sent across the failover link to the standby
module. You do not have to save the active configuration to Flash memory to replicate the
commands.
•
If you enter the write standby command on the active module, the standby module clears its running
configuration (except for the failover commands that must be pre-configured and are not replicated),
and the active module sends its entire configuration to the standby module.
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.
Note
Changes made on the standby module are not replicated to the active module. If you enter a command
on the standby module, the FWSM displays the message “**** WARNING **** Configuration
Replication is NOT performed from Standby module to Active module. Configurations are no longer
synchronized.” This message displays even when you enter many commands that do not affect the
configuration.
When the replication starts, the FWSM console displays the message “Beginning configuration
replication: Sending to mate,” and when it is complete, the FWSM displays the message “End
Configuration Replication to mate.” During the replication, information cannot be entered on the FWSM
terminal. Depending on the size of the configuration, replication can take several minutes.
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Disabling Configuration Synchronization
Management applications may lose connectivity when upgrading the FWSM with complex
configurations. This can result in incomplete configuration files being applied to the standby FWSM.
You can disable the automatic configuration synchronization in order to avoid incomplete configurations
being applied to the standby FWSM. You need to disable configuration synchronization when upgrading
a software image or changing the configuration on the active FWSM to verify that the configuration files
are complete before the configuration is synchronized with the standby FWSM configuration. After you
verify that the configuration is complete, reenable configuration synchronization
To disable configuration synchronization, enter this command:
fwsm(config)# failover suspend-config-sync
To reenable configuration synchronization, use the no form of the this command.
Failover Triggers
The module can fail if one of the following events occurs:
•
The module has a hardware failure or a power failure.
•
The module has a software failure.
•
Too many monitored interfaces fail.
Because the FWSM can have a large number of interfaces, it cannot monitor every interface. Rather,
you configure the FWSM to monitor a subset of interfaces. The FWSM fails over when a certain
number of monitored interfaces fails; you configure the failure threshold to be an absolute value or
a percentage of the total number of monitored interfaces.
See the “Failover Monitoring” section on page 15-13 for more information about when a module or
interface is considered to be failed.
Failover Actions
Table 15-1 shows the failover action for each failure event.
Table 15-1 Failover Behavior
Failure Event
Policy
Active Action
Standby Action
Notes
Active module failed (power
or hardware)
Failover
n/a
Become active
No hello messages are received on
any monitored interface or the
failover link.
Formerly active module
recovers
No failover
Become standby
No action
None.
Standby module failed (power No failover
or hardware)
Mark standby as
failed
n/a
When the standby module is
marked as failed, then the active
module will not attempt to fail
over, even if the interface failure
threshold is surpassed.
Mark active as
failed
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Table 15-1 Failover Behavior (continued)
Failure Event
Policy
Active Action
Standby Action
Notes
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 module cannot fail over to the
standby module 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 modules will become
active.
State link failed
No failover
No action
No action
State information will become out
of date, and sessions will be
terminated if a failover occurs.
Interface failure on active
module above threshold
Failover
Mark active as
failed
Become active
None.
Interface failure on standby
module above threshold
No failover
No action
Mark standby as
failed
When the standby module is
marked as failed, then the active
module will not attempt to fail over
even if the interface failure
threshold is surpassed.
Trunk failure in inter-switch
setup
No failover
No action
Become active
Both modules become active if all
communication between the
modules is terminated, as in the
case of a trunk failure. Neither
module receives hello messages,
and both modules assume the
active role.
Failover Monitoring
The FWSM monitors each module for overall health and for interface health. See the following sections
for more information about how the FWSM performs tests to determine the state of each module:
•
Module Health Monitoring, page 15-13
•
Interface Monitoring, page 15-14
Module Health Monitoring
The FWSM determines the health of the other module by monitoring the failover link. When a module
does not receive hello messages on the failover link, then the module sends an ARP request on all
interfaces, including the failover interface. The FWSM retries a user-configurable number of times. The
action the FWSM takes depends on the response from the other module. See the following possible
actions:
•
If the FWSM receives a response on any interface, then it does not fail over.
•
If the FWSM does not receive a response on any interface, then the standby module switches to
active mode and classifies the other module as failed.
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•
Note
If the FWSM does not receive a response on the failover link only, then the module does not failover.
The failover link is marked as failed. You should restore the failover link as soon as possible because
the module cannot fail over to the standby while the failover link is down.
If a failed module 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 module will fail
again.
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 VLAN (because the
interface is shared, all contexts benefit from the monitoring).
Note
An interface may be marked as failed (auto state down) when there are no longer any physical ports
belonging to a VLAN that is configured on the switch for the FWSM.
When a module does not receive hello messages on a monitored interface, it runs the following tests:
1.
Link Up/Down test—A test of the VLAN status. If the Link Up/Down test indicates that the VLAN
is operational, then the FWSM performs network tests. The purpose of these tests is to generate
network traffic to determine which (if either) module has failed. At the start of each test, each
module clears its received packet count for its interfaces. At the conclusion of each test, each module
looks to see if it has received any traffic. If it has, the interface is considered operational. If one
module receives traffic for a test and the other module does not, the module that received no traffic
is considered failed. If neither module has received traffic, then the next test is used.
2.
Network Activity test—A received network activity test. The module 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 module ARP cache for the 2 most recently acquired entries. One at a
time, the module sends ARP requests to these machines, attempting to stimulate network traffic.
After each request, the module 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 module
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 module 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 module 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 FWSM returns to standby mode
if the interface failure threshold is no longer met.
Note
If a failed module 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 module will fail
again.
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Configuring Failover
This section describes how to configure failover and includes the following topics:
•
Configuring the Primary Module, page 15-15
•
Configuring the Secondary Module, page 15-18
Configuring the Primary Module
Follow these steps to configure the primary module. For multiple context mode, all steps are performed
in the system execution space unless otherwise noted.
Note
At any time during the procedure, you can enter the show failover command to see the failover status.
See the “Using the Show Failover Command” section on page 15-19 section for detailed information.
Step 1
To configure the VLAN interface you are using for the failover link, enter the following command. For
multiple context mode, enter this command in the system execution space:
primary(config)# failover lan interface interface_name vlan vlan
Note this setting because this command is the same on the secondary module.
This VLAN should not be used for any other purpose (except, optionally, the state link) or be assigned
to any switch ports. This VLAN does need to be assigned to the FWSM by the switch.
Do not assign an ACL to this interface; failover traffic is allowed automatically, and other traffic is
denied.
Step 2
To set the IP address of the failover interface, enter the following command:
primary(config)# failover interface ip failover_interface ip_address mask standby
ip_address
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.
Note this setting because this command is the same on the secondary module.
The failover link IP address and MAC address do not change at failover. The active IP address always
stays with the primary module, while the standby IP address stays with the secondary module.
Step 3
(Stateful failover only) To configure the VLAN interface you are using for the state link, enter the
following command:
primary(config)# failover link interface_name [vlan vlan]
This VLAN should not be used for any other purpose (except, optionally, the failover link) or be assigned
to any switch ports. This VLAN does need to be assigned to the FWSM by the switch.
If the interface is the same as the failover interface, you do not need to identify the VLAN.
Do not assign an ACL to this interface; failover traffic is allowed automatically, and other traffic is
denied.
Step 4
(Stateful failover only) To set the IP address of the state interface, enter the following command:
primary(config)# failover interface ip state_interface ip_address mask standby ip_address
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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 module, while the standby IP address stays with the secondary module.
Step 5
(Stateful failover only—Optional), To allow HTTP connections to be included in the state information,
enter the following command:
primary(config)# failover replication http
If you do not allow HTTP replication, then HTTP connections are disconnected at failover. HTTP
connections are brief and frequent, and the state information, although updated constantly, might not
include the latest HTTP states at failover. For this reason, you might want to disable HTTP replication
to reduce the amount of traffic on the state link.
Step 6
To set the threshold for monitored interface failure, enter the following command:
primary(config)# failover interface-policy number[%]
When the number of failed monitored interfaces meets the value you set with this command, then the
FWSM fails over. You can set the following arguments:
Step 7
•
number—An absolute value.
•
number%—A percentage of all monitored interfaces.
To set this FWSM as the primary module, enter the following command:
primary(config)# failover lan unit primary
Note
Step 8
This command is the only configuration difference between the primary and secondary modules,
although you need to set other failover commands on the secondary module before the FWSM can
replicate the active configuration.
(Optional) To set how often hello messages are sent on the failover link and how long to wait before
testing the peer for failure if no hello messages are received, enter the following command:
primary(config)# failover polltime [unit] [msec] number [holdtime seconds]
See the following arguments:
•
polltime unit [msec] number—The amount of time between hello messages. Set the time in seconds
between 1 and 15. The default is 1 second. If you specify msec, you can set the time between 500
and 999 milliseconds.
•
holdtime number—Sets the time during which a module must receive a hello message on the
failover link, or else the module begins the testing process for peer failure. Set the time in seconds
between 15 and 45. The default is the greater of 15 seconds or 3 times the polltime. You cannot enter
a value that is less than 3 times the polltime.
For example, if the polltime is 1 second, then a 15 second holdtime means 15 hello messages are
missed before the module is tested for failure.
Note
Step 9
The interval between stateful information updates is 10 seconds, but if you set the polltime to be greater
than 10, then that interval is used.
(Optional) To set the time in seconds between hello messages on monitored interfaces, enter the
following command:
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primary(config)# failover polltime interface seconds
If the interface does not receive five consecutive hello messages, the FWSM begins the testing process
for interface failure. See the “Failover Monitoring” section on page 15-13 for more information.
The seconds is an integer between 3 and 15. The default is 15 seconds, which means an interface receives
no reply for 75 seconds (5 times the polling interval) before the interface is tested for failure.
Step 10
To enable failover, enter the following command:
primary(config)# failover
Step 11
(Multiple context mode only) To save the system configuration to Flash memory, enter the following
command:
primary(config)# copy running-config startup-config
Step 12
(Multiple context mode only) To change to a context to configure the standby IP addresses (if you have
not already done so) and to configure the interface monitoring, enter the following command:
primary(config)# changeto context name
Step 13
If you have not done so already, set the standby IP address for each interface (routed mode) or for the
management IP address (transparent mode) by entering the command appropriate for your firewall mode.
•
For routed mode, enter the following command for each interface:
primary/contexta(config)# ip address interface_name ip_address mask standby ip_address
•
For transparent mode, enter the following command:
primary/contexta(config)# ip address ip_address mask standby ip_address
The standby IP address is used on the FWSM that is currently the standby module.
To add the standby address, reenter the ip address command for each interface (or management IP
address) and add the standby ip_address option.
This IP address must be in the same subnet as the active IP address. You do not identify the subnet mask.
To check the current IP address settings, enter the show ip address command.
Step 14
To enable monitoring on an interface, enter the following command:
primary/contexta(config)# monitor-interface interface_name
The maximum number of interfaces to monitor on the FWSM (divided between all contexts) is 250.
Step 15
To save the configuration for the context (in multiple context mode) or for the single mode FWSM, enter
the following command:
primary/contexta(config)# copy running-config startup-config
Step 16
(Multiple context mode only) Repeat Step 12 through Step 15 for each context.
See the “Failover Configuration Example” section on page 15-27 for a typical failover configuration.
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Configuring Failover
Configuring the Secondary Module
The only configuration required for the secondary module is for the failover interface. The secondary
module requires these commands to initially communicate with the primary module. After the primary
module sends its configuration to the secondary module, the only permanent difference between the two
configurations is the failover lan unit command, which identifies each module as primary or secondary.
For multiple context mode, all steps are performed in the system execution space.
Note
At any time during the procedure, you can enter the show failover command to see the failover status.
See the “Using the Show Failover Command” section on page 15-19 section for detailed information.
To configure the secondary module, follow these steps:
Step 1
If required, and if you have not already done so, enter the activation key to enable the same number of
contexts as are licensed on the primary module by entering the following command:
secondary(config)# activation-key key
Step 2
If you have not already done so, set the context mode to match the primary module by entering the
following command:
secondary(config)# mode {single | multiple}
The FWSM reboots.
Step 3
To configure the VLAN interface you are using for the failover link, enter the following command:
secondary(config)# failover lan interface interface_name vlan vlan
Use the same setting as the primary module.
Step 4
To set the IP address of the failover interface, enter the following command:
secondary(config)# failover interface ip interface_name ip_address mask standby ip_address
Use the same setting as the primary module.
Step 5
(Optional) To set this FWSM as the secondary module, enter the following command:
secondary(config)# failover lan unit secondary
The default is secondary.
Note
Step 6
This command is the only configuration difference between the primary and secondary modules.
To enable failover, enter the following command:
secondary(config)# failover
After you enable failover, the active module sends the configuration in running memory to the standby
module. As the configuration synchronizes, the messages “Beginning configuration replication: Sending
to mate” and “End Configuration Replication to mate” appear on the active module console.
Step 7
To save the configuration to Flash memory, enter the following command:
secondary(config)# copy running-config startup-config
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Verifying the Failover Configuration
See the “Failover Configuration Example” section on page 15-27 for a typical failover 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 15-19
•
Viewing Monitored Interfaces, page 15-22
•
Testing the Failover Functionality, page 15-22
See the “Monitoring Failover” section on page 15-23 section for other troubleshooting tools.
Using the Show Failover Command
On each module, verify the failover status by entering the following command in the system execution
space:
primary(config)# show failover
This command shows the following information:
•
The failover status, either on or off
•
The active module
•
The IP addresses assigned for the active and standby modules
•
The failover link information
•
The interface policy
•
The stateful failover statistics
See the following sample show failover command output. A description of each field follows.
FWSM(config)# show failover
Failover On
Failover unit Primary
Failover LAN Interface fover Vlan 150
Unit Poll frequency 15 seconds
Interface Poll frequency 15 seconds
Interface Policy 50%
Monitored Interfaces 249 of 250 maximum
Config sync: active
Last Failover at: 10:58:08 Apr 15 2004
This host: Primary - Active
Active time: 2232 (sec)
admin Interface inside (10.6.8.91): Normal
admin Interface outside (70.1.1.2): Normal
Other host: Secondary - Standby
Active time: 0 (sec)
admin Interface inside (10.6.8.100): Normal
admin Interface outside (70.1.1.3): Normal
Stateful Failover Logical Update Statistics
Link : Luifc Vlan 151
Stateful Obj
xmit
xerr
rcv
rerr
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Verifying the Failover Configuration
General
sys cmd
up time
xlate
tcp conn
udp conn
ARP tbl
RIP Tbl
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
Logical Update Queue Information
Cur
Max
Total
Recv Q:
0
0
0
Xmit Q:
0
0
0
Table 15-2 describes the show failover output.
Table 15-2 Show Failover Display Description
Field
Failover
Failover module
Failover LAN Interface
Options
•
On
•
Off
•
Primary
•
Secondary
Shows the interface name and VLAN for the failover link:
interface_name vlan number
If you have not configured the failover interface, the display shows:
Not configured
Module Poll frequency
n seconds
The number of seconds you set with the failover poll unit command.
The default is 15 seconds.
Interface Poll frequency
n seconds
The number of seconds you set with the failover poll interface
command. The default is 15 seconds.
Interface Policy
n[%]
The threshold for interface failure that you set with the failover
interface-policy command. The default is 50%.
Monitored Interfaces
n of 250 maximum
The number of interfaces you are monitoring.
Config sync
•
Active—Configuration synchronization is active on the FWSM
•
Suspended—Configuration synchronization has been suspended or
disabled on the FWSM
Last Failover
The last time a failover occurred.
This host:
For each host, the display shows the following information.
Other host:
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Table 15-2 Show Failover Display Description (continued)
Field
Options
Primary or Secondary
Active time:
•
Active—The module is in active mode.
•
Standby—The module is in standby mode,
•
Disabled—The module has failover disabled, or the failover link is
not configured.
•
Listen—The module is attempting to discover an active module by
listening for polling messages.
•
Learn—The module detected an active module, and is not
synchronizing the configuration before going to standby mode.
•
Failed—The module is failed.
n (sec)
The amount of time the module has been in the active state. This time
is cumulative, so the standby module, if it was active in the past, will
also show a value.
[context_name] Interface For each interface, the display shows the IP address currently being
name (n.n.n.n):
used on each module, as well as one of the following conditions:
•
Failed—The interface has failed.
•
Link Down—The interface line protocol is down.
•
Normal—The interface is working correctly.
•
No Link—The interface has been administratively shut down.
•
Unknown—The FWSM cannot determine the status of the
interface.
•
(Waiting)—The interface has not yet received any polling
messages from the other module.
•
(Autostate Down)—The interface is marked as autostate down.
•
Testing—The interface is being tested.
In multiple context mode, the context name appears before each
interface.
Stateful Failover Logical
Update Statistics
Link
Stateful Obj
General
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.
For each field type, the following statistics are used:
•
xmit—Number of transmitted packets to the other module.
•
xerr—Number of errors that occurred while transmitting packets to
the other module.
•
rcv—Number of received packets.
•
rerr—Number of errors that occurred while receiving packets from
the other module.
Sum of all stateful objects.
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Table 15-2 Show Failover Display Description (continued)
Field
Options
sys cmd
Logical update system commands; for example, LOGIN and Stay
Alive.
up time
Up time, which the active module passes to the standby module.
xlate
Translation information.
tcp conn
TCP connection information.
udp conn
Dynamic UDP connection information.
ARP tbl
Dynamic ARP table information.
RIP Tbl
Dynamic router table information.
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.
Viewing Monitored Interfaces
To view the status of monitored interfaces, (from within the context) enter the following command:
primary/contexta(config)# show monitor-interface
For example:
primary/contexta(config)# show monitor-interface
This host: Primary - Active
Interface outside (88.1.1.2): Normal
Interface inside (10.6.8.91): Normal
Other host: Secondary - Standby
Interface outside (88.1.1.3): Normal
Interface inside (10.6.8.100): Normal
Testing the Failover Functionality
Follow these steps to ensure that failover works:
Step 1
Test that your primary (active) module 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 module by entering the following command:
primary(config)# no failover active
Step 3
Use FTP to send another file between the same two hosts.
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Forcing Failover
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 leave the secondary module as active or force the primary module to be
active again by entering the following command:
primary(config)# failover active
Forcing Failover
To force the standby module to become active, enter one of the following commands:
•
Enter this command on the active module to failover to the standby module:
primary(config)# no failover active
•
Enter this command on the standby module to force it to become active:
secondary(config)# failover active
Disabling Failover
When you disable failover, the active and standby state of each module is maintained until you restart.
For example, the standby module remains in standby mode so that both modules do not start passing
traffic. To make the standby module active (even with failover disabled), see the “Forcing Failover”
section above.
To disable failover, enter the following command:
primary(config)# no failover
This command is not replicated to the standby module so you must disable failover of the standby
module separately.
To verify that failover is off, enter the show failover command:
primary(config)# show failover
Failover Off
...
Monitoring Failover
When a failover occurs, both FWSMs send out system messages. This section includes the following
topics:
•
Failover System Messages, page 15-24
•
SNMP, page 15-24
•
Debug Messages, page 15-24
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Frequently Asked Failover Questions
Failover System Messages
The FWSM issues a number of system messages related to failover at priority level 2, which indicates a
critical condition. To view these messages, see the Catalyst 6500 Series Switch and Cisco 7600 Series
Router Firewall Services Module System Messages Guide to enable logging and to see descriptions of
the system messages.
SNMP
To receive SNMP syslog traps for failover, see the “Using SNMP” section on page 17-1 for more
information.
Debug Messages
To see debug messages, enter the debug fover command. See the Catalyst 6500 Series Switch and Cisco
7600 Series Router Firewall Services Module Command Reference for more information.
Frequently Asked Failover Questions
This section contains frequently asked questions about the failover features and includes the following
topics:
•
Configuration Replication Questions, page 15-24
•
Basic Failover Questions, page 15-25
•
Stateful Failover Questions, page 15-26
Configuration Replication Questions
See the following questions and answers for configuration replication:
•
Does configuration replication save the configuration to Flash memory on the standby module?
No, the configuration is only in running memory.
•
How can both modules be configured the same without manually entering the configuration twice?
Commands entered on the active module are automatically replicated to the standby module.
•
What happens if I enter commands on the standby module?
You will see an error message telling you that the configurations are out of sync. However, the
command is still applied.
If you enter individual commands on the active module that are replicated to the standby module,
your alterations on the standby module are preserved.
If you use the write standby command on the active module, it will erase any new commands you
entered on the standby module.
•
What happens if I enter the copy running-config startup-config command on the active module?
The copy running-config startup-config command is replicated to the standby module, which
proceeds to write its configuration to Flash memory.
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Frequently Asked Failover Questions
•
What happens if the configuration in Flash memory on the secondary module differs from the
configuration on the primary module?
After startup, the primary module sends its configuration to the secondary module and erases the
running configuration on the secondary module. However, the secondary module startup
configuration remains unaltered in Flash memory.
•
How can I view the running configuration and the Flash memory configuration?
– show running—Shows the running configuration. You can also enter write terminal.
– show config—Shows the configuration in Flash memory.
•
Are contexts that are on disk saved to disk on the standby module?
No, all contexts are loaded into running memory only. The startup configuration for a context
continues to reside on the primary module disk. You can copy the context configurations to the
standby module so that if the standby module starts up and needs to be the active module, it can load
the contexts from disk.
•
Can I fail over a context, but not the entire module?
No, you can only have one active FWSM.
Basic Failover Questions
See the following questions and answers for basic failover:
•
Which module becomes active if you restart both modules?
The primary module.
•
What happens if the active module has a power failure?
After hello messages are not acknowledged, the standby module becomes active.
•
What happens when the formerly active module comes online again?
No failover occurs. It remains in standby mode.
•
How long does it take to detect a failure?
– Network errors are detected within three consecutive polling intervals (by default, 15 second
intervals). The polling interval is user-configurable using the failover poll interface command.
– Failover communication errors are detected within a user-configurable number of seconds (the
default is 15). The polling time is user-configurable using the failover poll unit command.
•
What maintenance is required?
Syslog messages are generated when any errors or switches occur. Evaluate the failed module and
fix or replace it.
•
Is it possible to have both FWSM modules become active at the same time?
Yes, in the following circumstances:
– Both modules have configurations in Flash memory
– Both modules have failover enabled
– The failover link is down at startup
or
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Frequently Asked Failover Questions
In an inter-switch failover scenario, the trunk between the switches fails
•
What prevents the standby module from passing traffic?
The FWSM failover feature ensures that only traffic aimed to the standby module (hello messages,
Telnet if enabled) is successful, while traffic aimed through the module is dropped.
Stateful Failover Questions
See the following questions and answers for stateful failover:
•
What information is not replicated to the standby FWSM on stateful failover?
– The user authentication (uauth) table.
– The ISAKMP and IPSec SA table (for management access only).
– The ARP table.
– Routing information.
– Other UDP connections.
•
Can I share the state link interface with the failover link?
Yes, however, we recommend that you use a separate interface.
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Failover Configuration Example
Failover Configuration Example
Figure 15-8 shows the network diagram for a failover configuration within a switch. The only difference
between the configuration of inter-switch and intra-switch failover is on the switch; the configuration
on the FWSM is the same.
Figure 15-8 Failover Scenario
Internet
VLAN 100
Switch
VLAN 200
Active FWSM
209.165.201.1
PAT: 209.165.201.5
Standby FWSM
209.165.201.2
192.168.253.1
192.168.253.2
Failover VLAN 10
State VLAN 11
192.168.253.5
192.168.253.6
192.168.2.1
192.168.2.2
Inside
Web Server 192.168.2.5
Static: 209.165.201.5
104649
VLAN 201
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Failover Configuration Example
Example 15-1 lists the typical commands in a failover configuration. This example shows how to
configure multiple context mode and shows one context, the admin context. For single context mode,
simply combine the two configurations, and remove the admin-context command and the context
commands.
Example 15-1 Failover Configuration
System Configuration:
hostname FWSM
enable password farscape
password crichton
admin-context adminctxt
context adminctxt
allocate-interface vlan200
allocate-interface vlan201
config-url disk:/adminctxt.cfg
failover lan interface faillink vlan 10
failover link statelink vlan 11
failover lan unit primary
failover interface ip faillink 192.168.253.1 255.255.255.252 standby 192.168.253.2
failover interface ip statelink 192.168.253.5 255.255.255.252 standby 192.168.253.6
failover interface-policy 1
failover replication http
failover
Context Configuration:
nameif vlan200 outside security0
nameif vlan201 inside security100
enable password aeryn
password rygel
telnet 192.168.2.45 255.255.255.255 [A host on the context network, not shown]
ip address outside 209.165.201.1 255.255.255.224 standby 209.165.201.2
ip address inside 192.168.2.1 255.255.255.0 standby 192.168.2.2
monitor-interface inside
monitor-interface outside
global (outside) 1 209.165.201.3 netmask 255.255.255.224
nat (inside) 1 0.0.0.0 0.0.0.0 0 0
static (inside,outside) 209.165.201.5 192.168.2.5 netmask 255.255.255.255 0 0
access-list acl_out permit tcp any 209.165.201.5 eq 80
access-group acl_out in interface outside
route outside 0 0 209.165.201.4 1
Example 15-2 shows the configuration for the secondary module.
Example 15-2 Failover Configuration: Secondary Unit
failover lan interface faillink vlan 10
failover lan unit secondary
failover interface ip faillink 192.168.253.1 255.255.255.252 standby 192.168.253.2
failover
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16
Managing Software and Configuration Files
This chapter describes how to install new software on the Firewall Services Module (FWSM) from an
FTP, TFTP, HTTP, or HTTPS server. You can upgrade the application software, the maintenance
software, and PDM for FWSM management software.
Note
If you are upgrading from a pervious release, for example FWSM release 1.1, refer to the FWSM
documentation for your release.
This chapter also describes how to download or back up a configuration file.
This chapter contains the following sections:
•
Installing Application or PDM Software, page 16-1
•
Installing Maintenance Software, page 16-5
•
Downloading and Backing Up Configuration Files, page 16-5
Installing Application or PDM Software
This section contains the following topics:
•
Installation Overview, page 16-1
•
Installing Application or PDM Software to the Current Partition, page 16-2
•
Installing Application Software to Any Application Partition, page 16-3
Installation Overview
To upgrade PDM, you can only install to the current application partition. For application software, you
can use one of two methods to upgrade:
•
Installing to the current application partition
The benefit of this method is you do not have to boot into the maintenance partition; instead you log
in as usual and copy the new software. The activation key is maintained with this method.
This method supports downloading from a TFTP, FTP, HTTP, or HTTPS server.
You cannot copy software to the other application partition. You might want to copy to the other
partition if you want to keep the old version of software as a backup in the current partition.
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Installing Application or PDM Software
You must have an operational configuration with network access. For multiple context mode, you
need to have network connectivity through the admin context.
•
Installing to any application partition from the maintenance partition
The benefit of this method is you can copy software to both application partitions, and you do not
have to have an operational configuration. You just need to configure some routing parameters in
the maintenance partition so you can reach the server on VLAN 1.
The disadvantage is that you need to boot into the maintenance partition, which might not be
convenient if you have an operational application partition. Also, if you are running maintenance
software Version 1.1, the activation key, if present, is removed and the mode reverts to single context
mode. We suggest that you upgrade the maintenance software to Version 2.1 or later to keep the
activation key and mode. See the “Installing Maintenance Software” section on page 16-5 to
upgrade. To view the maintenance software version, log into the maintenance partition (see the
“Installing Application Software to Any Application Partition” section on page 16-3), and enter
show version.
This method supports downloading from an FTP server only.
See the “Managing the Firewall Services Module Boot Partitions” section on page 2-12 for more
information about application and maintenance partitions.
Installing Application or PDM Software to the Current Partition
When you log into the FWSM during normal operation, you can copy the application software or PDM
software to the current application partition from a TFTP, FTP, HTTP, or HTTPS server.
For multiple context mode, you must be in the system execution space.
Make sure you have network access to the server:
•
For single context mode, configure any interface, its IP address, and any static routes required to
reach the server. See the “Configuring Interfaces” section on page 6-6 and then Chapter 8,
“Configuring IP Addresses, Routing, and DHCP.”
•
For multiple context mode, you must first add the admin context and configure interfaces, IP
addresses, and routing to provide network access. See the “Configuring a Security Context” section
on page 5-19, and then the “Configuring Interfaces” section on page 6-6 and Chapter 8,
“Configuring IP Addresses, Routing, and DHCP.”
To copy the application or PDM software, enter one of the following commands for the appropriate
download server:
•
To copy from a TFTP server, enter the following command:
FWSM# copy tftp://server[/path]/filename flash:[image | pdm]
The image keyword (default) copies the application software, and the pdm keyword copies the PDM
software.
•
To copy from an FTP server, enter the following command:
FWSM# copy ftp://[user[:password]@]server[/path]/filename[;type=xx]
flash:[image | pdm]
The image option (default) copies the application software, and the pdm option copies the PDM
software.
The type can be one of the following keywords:
– ap—ASCII passive mode
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Installing Application or PDM Software
– an—ASCII normal mode
– ip—(Default) Binary passive mode
– in—Binary normal mode
Use binary for image files.
•
To copy from an HTTP or HTTPS server, enter the following command:
FWSM# copy http[s]://
[user[:password]@]server[:port][/path]/filename flash:[image | pdm]
The image option (default) copies the application software, and the pdm option copies the PDM
software.
For example, to copy the application software from a TFTP server, enter:
FWSM# copy tftp://209.165.200.226/cisco/c6svc-fwm-k9.2-1-1.bin flash:image
To copy the application software from an FTP server, enter:
FWSM# copy ftp://admin:[email protected]/cisco/c6svc-fwm-k9.2-1-1.bin;type=ip
flash:image
To copy PDM from an HTTPS server, enter:
FWSM# copy http://admin:[email protected]/pdm/pdm-411.bin flash:pdm
Installing Application Software to Any Application Partition
If you log into the maintenance partition, you can install application software to either application
partition (cf:4 or cf:5).
Note
The FWSM maintenance partition can only use VLAN 1 on the switch. The FWSM does not support
802.1Q tagging on VLAN 1.
If you are running maintenance software release 1.1, the activation key, if present, is removed and the
mode reverts to single context mode. We suggest that you upgrade the maintenance software to Release
2.1 or later to keep the activation key and mode. See the “Installing Maintenance Software” section on
page 16-5 to upgrade. To view the maintenance software version, log into the maintenance partition (see
the “Installing Application Software to Any Application Partition” section on page 16-3), and enter
show version.
To install application software from an FTP server while logged into the maintenance partition, follow
these steps:
Step 1
To boot the FWSM into the maintenance partition, enter the command for your operating system:
•
For Cisco IOS software, enter the following command:
Router# hw-module module mod_num reset cf:1
•
For Catalyst operating system software, enter the following command:
Console> (enable) reset mod_num boot cf:1
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Installing Application or PDM Software
Step 2
To session into the FWSM, enter the command for your operating system:
•
For Cisco IOS software, enter the following command:
Router# session slot mod_num processor 1
•
For Catalyst operating system software, enter the following command:
Console> (enable) session mod_num
Step 3
To log into the FWSM maintenance partition as root, enter the following command:
Login: root
Step 4
Enter the password at the prompt:
Password:
By default, the password is “cisco.”
Step 5
To assign an IP address to the maintenance partition, enter the following command:
[email protected]# ip address ip _address netmask
This address is the address for VLAN 1, which is the only VLAN used by the maintenance partition.
Step 6
To assign a default gateway to the maintenance partition, enter the following command:
[email protected]# ip gateway ip_address
Step 7
Optional) To ping the FTP server to verify connectivity, enter the following command:
[email protected]# ping ftp_address
Step 8
To download the application software from the FTP server, enter the following command:
[email protected]# upgrade ftp://[user[:password]@]server[/path]/filename cf:{4 | 5}
cf:4 and cf:5 are the application partitions on the FWSM.
Follow the screen prompts during the upgrade.
The configuration file in the application partition is backed up and restored at the end of the upgrade
operation.
Step 9
To log out of the maintenance partition, enter the following command:
[email protected]# logout
Step 10
To reboot the module into the application partition, cf:4 or cf:5, enter the command for your operating
system:
•
For Cisco IOS, enter the following command:
Router# hw-module module mod_num reset cf:{4 | 5}
•
For Catalyst operating system software, enter the following command:
Console> (enable) reset mod_num boot cf:{4 | 5}
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Installing Maintenance Software
Installing Maintenance Software
You can download the maintenance software from a TFTP, HTTP, or HTTPS server when you are logged
into the application partition. Passwords for the root and guest accounts of the maintenance partition are
retained after the upgrade.
For multiple context mode, you must be in the system execution space.
Make sure you have network access to the server:
•
For single context mode, configure any interface, its IP address, and any static routes required to
reach the server. See the “Configuring Interfaces” section on page 6-6 and then Chapter 8,
“Configuring IP Addresses, Routing, and DHCP.”
•
For multiple context mode, you must first add the admin context and configure interfaces, IP
addresses, and routing to provide network access. See the “Configuring a Security Context” section
on page 5-19, and then the “Configuring Interfaces” section on page 6-6 and Chapter 8,
“Configuring IP Addresses, Routing, and DHCP.”
To upgrade the maintenance partition software, enter one of the following commands for the appropriate
download server:
•
To download the maintenance software from a TFTP server, enter the following command:
FWSM# upgrade-mp tftp[://server[:port][/path]/filename]
If you do not enter the TFTP server information, you are prompted for the server information.
•
To download the maintenance software from an HTTP or HTTPS server, enter the following
command:
FWSM# upgrade-mp http[s]://[user[:password]@]server[:port][/path]/filename
The following example shows the prompts for the TFTP server information:
FWSM# upgrade-mp tftp
Address or name of remote host [127.0.0.1]? 10.1.1.5
Source file name [cdisk]? mp.2-1-0-3.bin.gz
copying tftp://10.1.1.5/mp.2-1-0-3.bin.gz to flash
[yes|no|again]? yes
!!!!!!!!!!!!!!!!!!!!!!!
Received 1695744 bytes.
Maintenance partition upgraded.
Downloading and Backing Up Configuration Files
This section describes how to download and back up configuration files, and includes the following
sections:
•
Downloading a Text Configuration, page 16-6
•
Backing Up the Configuration, page 16-7
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Downloading and Backing Up Configuration Files
Downloading a Text Configuration
You can download a text file from the following server types:
•
TFTP
•
FTP
•
HTTP
•
HTTPS
Make sure you have network access to the server:
•
For single context mode, configure any interface, its IP address, and any static routes required to
reach the server. See the “Configuring Interfaces” section on page 6-6 and then Chapter 8,
“Configuring IP Addresses, Routing, and DHCP.”
•
For multiple context mode, add the admin context and configure interfaces, IP addresses, and
routing to provide network access. See the “Configuring a Security Context” section on page 5-19,
and then the “Configuring Interfaces” section on page 6-6 and Chapter 8, “Configuring IP
Addresses, Routing, and DHCP.”
To download a text configuration from a server, follow these steps:
Step 1
To copy the single mode startup configuration or the multiple mode system startup configuration from
the server to Flash memory, enter one of the following commands for the appropriate download server:
•
To copy from a TFTP server, enter the following command:
FWSM# copy tftp://server[/path]/filename startup-config
•
To copy from an FTP server, enter the following command:
FWSM# copy ftp://[user[:password]@]server[/path]/filename[;type=xx] startup-config
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
You can use ASCII or binary for configuration files.
•
To copy from an HTTP or HTTPS server, enter the following command:
FWSM# copy http[s]://[user[:password]@]server[:port][/path]/filename startup-config
For example, to copy the configuration from a TFTP server, enter the following command:
FWSM# copy tftp://209.165.200.226/configs/startup.cfg startup-config
To copy the configuration from an FTP server, enter the following command:
FWSM# copy ftp://admin:[email protected]/configs/startup.cfg;type=an startup-config
To copy the configuration from an HTTP server, enter the following command:
FWSM# copy http://209.165.200.228/configs/startup.cfg startup-config
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Step 2
(Multiple context mode only) To copy context configurations to disk, including the admin configuration,
enter one of the following commands for the appropriate download server:
•
To copy from a TFTP server, enter the following command:
FWSM# copy tftp://server[/path]/filename disk:[path/]filename
•
To copy from a FTP server, enter the following command:
FWSM# copy ftp://[user[:password]@]server[/path]/filename[;type=xx] disk:[path/]filename
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
You can use ASCII or binary for configuration files.
•
To copy from a HTTP or HTTPS server, enter the following command:
FWSM# copy http[s]://[user[:password]@]server[:port][/path]/filename disk:[path/]filename
Step 3
Copy the new startup configuration to the running configuration using one of these options:
•
To merge the startup configuration with the current running configuration, enter the following
command:
FWSM(config)# copy startup-config running-config
•
To load the startup configuration and discard the running configuration, restart the FWSM by
entering the following command:
FWSM# reboot
Backing Up the Configuration
To back up your configuration, copy it to an external server. Use one of the following methods:
•
Copying the Configuration to a Server, page 16-7
•
Copying the Configuration from the Terminal Display, page 16-8
Copying the Configuration to a Server
You can back up configuration files in the following circumstances:
•
Backing up the Single Mode Configuration or Multiple Mode System Configuration, page 16-7
•
Backing Up a Context Configuration within the Context, page 16-8
Backing up the Single Mode Configuration or Multiple Mode System Configuration
In single context mode, or from the system configuration in multiple mode, you can copy the startup
configuration, running configuration, or a configuration file by name on disk (such as the admin.cfg).
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Downloading and Backing Up Configuration Files
Enter one of the following commands for the appropriate backup server:
•
To copy to a TFTP server, enter the following command:
FWSM# copy {startup-config | running-config | disk:[path/]filename}
tftp://server[/path]/filename
•
To copy to a FTP server, enter the following command:
FWSM# copy {startup-config | running-config | disk:[path/]filename}
ftp://[user[:password]@]server[/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
Use ASCII or binary for configuration files (as in this case), and binary only for image files.
Backing Up a Context Configuration within the Context
In multiple context mode, from within a context, you can perform the following backups:
•
To copy the running configuration to the startup configuration server (connected to the
admin context), enter the following command:
FWSM/contexta# copy running-config startup-config
•
To copy the running configuration to a TFTP server connected to the context network, follow these
steps:
a. To specify the TFTP server that is connected to the context network, enter the following
command:
FWSM/contexta# tftp-server interface_name ip_address path[/filename]
b. To copy the running configuration to the TFTP server, enter the following command:
FWSM/contexta(config)# write net [:filename]
If you specify the filename in the tftp-server command (above), you do not need to identify it
in the write net command.
For example:
FWSM/contexta(config)# tftp-server 10.1.1.1 /fwsmconfigs/contextbackup.cfg
FWSM/contexta(config)# write net
Copying the Configuration from the Terminal Display
To print the configuration to the terminal, enter the following command:
FWSM# write terminal
Copy the output from this command, and then paste the configuration into a text file.
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17
Monitoring and Troubleshooting the Firewall
Services Module
This chapter describes how to monitor and troubleshoot the Firewall Services Module (FWSM), and
contains the following sections:
•
Monitoring the Firewall Services Module, page 17-1
•
Troubleshooting the Firewall Services Module, page 17-4
Monitoring the Firewall Services Module
You can monitor the FWSM using system messages or using Simple Network Management Protocol
(SNMP). This section describes:
•
Using System Messages, page 17-1
•
Using SNMP, page 17-1
Using System Messages
The FWSM provides extensive system messages. See the Catalyst 6500 Series Switch and Cisco 7600
Series Router Firewall Services Module System Messages Guide to configure logging and to view system
message descriptions.
Using SNMP
This section describes how to use SNMP and includes the following topics:
•
SNMP Overview, page 17-2
•
Enabling SNMP, page 17-3
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Monitoring the Firewall Services Module
SNMP Overview
The FWSM provides support for network monitoring using SNMP V1. The FWSM supports traps and
SNMP get requests, but does not support SNMP set requests.
You can configure the FWSM to send traps (event notifications) to a network management station
(NMS), or you can use the NMS to browse the Management Information Bases (MIBs) on the FWSM.
MIBs are a collection of definitions, and the FWSM maintains a database of values for each definition.
Browsing a MIB entails issuing an SNMP get request from the NMS. Use CiscoWorks for Windows or
any other SNMP V1, MIB-II compliant browser to receive SNMP traps and browse a MIB.
Table 17-1 lists supported MIBs and traps for the FWSM and, in multiple mode, for each context. You
can download Cisco MIBs from the following website:
http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml
After you download the MIBs, compile them for your NMS.
Table 17-1 SNMP MIB and Trap Support
MIB or Trap Support
Description
SNMP core traps
The FWSM sends the following core SNMP traps:
MIB-II
•
authentication—An SNMP request fails because the NMS did not authenticate with the
correct community string.
•
linkup—A VLAN interface is up.
•
linkdown—A VLAN interface is down, for example, if you removed the nameif command,
or the VLAN was removed from the switch configuration.
•
coldstart—The FWSM is running after a reload.
The FWSM supports browsing of the following groups and tables:
Cisco Firewall MIB
•
system
•
interfaces
•
ip.ipAddrTable
The FWSM supports browsing of the following groups:
•
cfwEvents
•
cfwSystem
The information is cfwSystem.cfwStatus, which relates to failover status, pertains to the
entire device and not just a single context.
The FWSM supports the following trap:
•
cfwSecurityNotification
Cisco Memory Pool MIB The FWSM supports browsing of the following table:
•
Cisco Process MIB
The FWSM supports browsing of the following table:
•
Cisco Syslog MIB
ciscoMemoryPoolTable—The memory usage described in this table applies only to the
FWSM general-purpose processor, and not to the network processors.
cpmCPUTotalTable—The CPU usage described in this table applies only to the FWSM
general-purpose processor, and not to the network processors.
The FWSM supports the following trap:
•
clogMessageGenerated
You cannot browse this MIB.
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Enabling SNMP
The SNMP agent that runs on the FWSM performs two functions:
•
Replies to SNMP requests from NMSs.
•
Sends traps (event notifications) to NMSs.
To enable the SNMP agent and identify an NMS that can connect to the FWSM, follow these steps:
Step 1
To identify the IP address of the NMS that can connect to the FWSM, enter the following command:
FWSM/contexta(config)# snmp-server host interface_name ip_address [trap | poll]
[udp-port port]
Specify trap or poll if you want to limit the NMS to receiving traps only or browsing (polling) only. By
default, the NMS can use both functions.
SNMP traps are sent on UDP port 162 by default. You can change the port number using the udp-port
keyword.
Step 2
To specify the community string, enter the following command:
FWSM/contexta(config)# snmp-server community key
The SNMP community string is a shared secret between the FWSM and the NMS. The key is a
case-sensitive value up to 32 characters in length. Spaces are not permitted. The default is public.
Step 3
(Optional) To set the SNMP server location or contact information, enter the following command:
FWSM/contexta(config)# snmp-server {contact | location} text
Step 4
To enable the FWSM to send traps to the NMS, enter the following command:
FWSM/contexta(config)# snmp-server enable traps [all | syslog | firewall | snmp [trap1]
[trap2] [...]]
By default, SNMP core traps are enabled (snmp). If you do not enter a trap type in the command, syslog
is the default. To enable or disable all traps, enter the all option. For snmp, you can identify each trap
type separately. See Table 17-1 on page 17-2 for a list of traps.
Step 5
To enable system messages to be sent as traps to the NMS, enter the following command:
FWSM/contexta(config)# logging history level
You must also enable syslog traps using the snmp-server enable traps command above.
Step 6
To enable logging, so system messages are generated and can then be sent to an NMS, enter the following
command:
FWSM/contexta(config)# logging on
The following example sets the FWSM to receive requests from host 192.168.3.2 on the inside interface,
but the FWSM does not send SNMP traps.
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
FWSM/contexta(config)#
snmp-server
snmp-server
snmp-server
snmp-server
host 192.168.3.2
location building 42
contact kim lee
community ohwhatakeyisthee
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Troubleshooting the Firewall Services Module
Troubleshooting the Firewall Services Module
This section describes how troubleshoot the FWSM, and includes the following topics:
•
Testing Your Configuration, page 17-4
•
Reloading the Firewall Services Module, page 17-8
•
Troubleshooting Passwords and AAA, page 17-9
•
Other Troubleshooting Tools, page 17-10
•
Common Problems, page 17-11
Testing Your Configuration
This section describes how to test connectivity for the single mode FWSM or for each security context.
The following steps describe how to ping the FWSM interfaces, and how to allow hosts on one interface
to ping through to hosts on another interface.
We recommend that you only enable pinging and debug messages during troubleshooting. When you are
done testing the FWSM, follow the steps in the “Disabling the Test Configuration” section on page 17-8.
This section includes:
•
Enabling ICMP Debug Messages and System Messages, page 17-4
•
Pinging FWSM Interfaces, page 17-5
•
Pinging Through the FWSM, page 17-7
•
Disabling the Test Configuration, page 17-8
Enabling ICMP Debug Messages and System Messages
Debug messages and system messages can help you troubleshoot why your pings are not successful. The
FWSM only shows ICMP debug messages for pings to the FWSM interfaces, and not for pings through
the FWSM to other hosts. To enable debugging and system messages, follow these steps:
Step 1
To show ICMP packet information for pings to the FWSM interfaces, enter the following command:
FWSM/contexta(config)# debug icmp trace
Step 2
To set system messages to be sent to Telnet or SSH sessions, enter the following command:
FWSM/contexta(config)# logging monitor debug
You can alternately use logging buffer debug to send messages to a buffer, and then view them later
using the show logging command.
Step 3
To send the system messages to your Telnet or SSH session, enter the following command:
FWSM/contexta(config)# terminal monitor
Step 4
To enable system messages, enter the following command:
FWSM/contexta(config)# logging on
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The following example shows a successful ping from an external host (209.165.201.2) to the FWSM
outside interface (209.165.201.1):
FWSM/contexta(config)# debug icmp trace
Inbound ICMP echo reply (len 32 id 1 seq 256) 209.165.201.1 > 209.165.201.2
Outbound ICMP echo request (len 32 id 1 seq 512) 209.165.201.2 > 209.165.201.1
Inbound ICMP echo reply (len 32 id 1 seq 512) 209.165.201.1 > 209.165.201.2
Outbound ICMP echo request (len 32 id 1 seq 768) 209.165.201.2 > 209.165.201.1
Inbound ICMP echo reply (len 32 id 1 seq 768) 209.165.201.1 > 209.165.201.2
Outbound ICMP echo request (len 32 id 1 seq 1024) 209.165.201.2 > 209.165.201.1
Inbound ICMP echo reply (len 32 id 1 seq 1024) 209.165.201.1 > 209.165.201.2
The above example shows the ICMP packet length (32 bytes), the ICMP packet identifier (1), and the
ICMP sequence number (the ICMP sequence number starts at 0 and is incremented each time a request
is sent).
Pinging FWSM Interfaces
To test that the FWSM interfaces are up and running and that the FWSM and connected routers are
routing correctly, you can ping the FWSM interfaces. To ping the FWSM interfaces, follow these steps:
Step 1
Create a sketch of your single mode FWSM or security context showing the interface names, security
levels, and IP addresses. The sketch should also include any directly connected routers, and a host on the
other side of the router from which you will ping the FWSM. You will use this information for this
procedure as well as the procedure in the “Pinging Through the FWSM” section on page 17-7. (See
Figure 17-1.)
Figure 17-1 Network Sketch with Interfaces, Routers, and Hosts
10.1.1.2
Host 209.265.200.230
209.265.200.226
Router
10.1.3.2
Router
192.168.1.2
dmz1
192.168.1.1
security20
209.165.201.2
outside
209.165.201.1
security
Host 10.1.3.6
Router
192.168.3.2
dmz3
192.168.3.1
security60
192.168.2.2
Router
inside
192.168.0.1
security100
192.168.0.2
Router
10.1.0.1
10.1.0.3
dmz4
192.168.4.1
security80
inside
security100
192.168.4.2
10.1.0.2
Host 10.1.2.90
209.165.201.1
Transp. FWSM
Router
10.1.2.2
209.165.201.24
outside
security
Routed FWSM
dmz2
192.168.2.1
security40
Host
Host 10.1.0.34
10.1.0.2
Router
10.1.4.2
Host 10.1.4.67
Router
10.1.1.1
Host
10.1.1.5
104680
Host 10.1.1.56
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Step 2
To enable ICMP to the FWSM, enter the following command:
FWSM/contexta(config)# icmp permit any interface_name
Enter this command for each interface you want to test.
Step 3
Ping each FWSM interface from the directly connected routers. For transparent mode, ping the
management IP address.
This test ensures that the FWSM interfaces are active and that the VLAN configuration is correct.
A ping might fail if the FWSM interface is not active, the VLAN configuration is incorrect, or if a switch
between the FWSM and router is down (see Figure 17-2). In this case, no debug messages or system
messages appear on the FWSM, because the packet never reaches it.
Figure 17-2 Ping Failure at FWSM Interface
FWSM
104687
Ping
Router
If the ping reaches the FWSM, and the FWSM responds, you see debug messages like the following:
ICMP echo reply (len 32 id 1 seq 256) 209.165.201.1 > 209.165.201.2
ICMP echo request (len 32 id 1 seq 512) 209.165.201.2 > 209.165.201.1
If the ping reply does not return to the router, then you might have a switch loop or redundant IP
addresses. (See Figure 17-3.)
Figure 17-3 Ping Failure Because of IP Addressing Problems
Ping
Router
FWSM
192.168.1.2
192.168.1.1
104688
Host
192.168.1.2
Step 4
Ping each FWSM interface from a remote host. For transparent mode, ping the management IP address.
This test checks that the directly connected router can route the packet between the host and the FWSM,
and that the FWSM can correctly route the packet back to the host.
A ping might fail if the FWSM does not have a route back to the host through the intermediate router
(see Figure 17-4). In this case, the debug messages show that the ping was successful, but you see system
message 110001 indicating a routing failure.
Ping
Host
Router
?
FWSM
104683
Figure 17-4 Ping Failure Because the FWSM has no Route
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Pinging Through the FWSM
After you successfully ping the FWSM interfaces, you should make sure traffic can pass successfully
through the FWSM. For routed mode, this test shows that NAT is working correctly. For transparent
mode, which does not use NAT, this test confirms that the FWSM is operating correctly; if the ping fails
in transparent mode, contact technical support.
You should originate pings from hosts that are normally allowed to access remote networks; you do not
need to ping from outside to inside, for example, if you do not allow any outside hosts to access the
inside.
To ping between hosts on different interfaces, follow these steps:
Step 1
To add an ACL allowing ICMP from any source host, enter the following command:
FWSM/contexta(config)# access-list ICMPTEST extended permit icmp any any
Step 2
To assign the ACL to each source interface, enter the following command:
FWSM/contexta(config)# access-group ICMPTEST in interface interface_name
Repeat this command for each source interface.
Step 3
To enable the ICMP inspection engine, so ICMP responses are allowed back to the source host, enter the
following command:
FWSM/contexta(config)# fixup protocol icmp
Alternatively, you can also apply the ICMPTEST ACL to the destination interface to allow ICMP traffic
back through the FWSM.
Step 4
Ping from the host or router through the source interface to another host or router on another interface.
Repeat this step for as many interface pairs as you want to check.
If the ping succeeds, you see a system message confirming the address translation for routed mode
(305009 or 305011) and that an ICMP connection was established (302020). You can also enter the
show xlate and show conns commands to view this information.
If the ping fails for transparent mode, contact technical support.
For routed mode, the ping might fail because NAT is not configured correctly. (See Figure 17-5.) In this
case, you see a system message showing that the NAT translation failed (305005 or 305006). If the ping
is from an outside host to an inside host, and you do not have a static translation, you see message
106010: deny inbound icmp.
Note
The FWSM only shows ICMP debug messages for pings to the FWSM interfaces, and not for pings
through the FWSM to other hosts.
Host
Ping
Router
FWSM
Router
Host
104686
Figure 17-5 Ping Failure Because the FWSM is not Translating Addresses
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Disabling the Test Configuration
After you complete your testing, disable the test configuration that allows ICMP to and through the
FWSM and that prints debug messages. If you leave this configuration in place, it can pose a serious
security risk. Debug messages also slow the FWSM performance.
To disable the test configuration, follow these steps:
Step 1
To disable ICMP debug messages, enter the following command:
FWSM/contexta(config)# no debug icmp trace
Step 2
To disable logging, if desired, enter the following command:
FWSM/contexta(config)# no logging on
Step 3
To disable ICMP to the FWSM for all interfaces, enter the following command:
FWSM/contexta(config)# clear icmp
If you want to disable ICMP for a certain interface, use the no icmp permit interface_name command.
Step 4
To remove the ICMPTEST ACL, and also delete the related access-group commands, enter the
following command:
FWSM/contexta(config)# no access-list ICMPTEST
Step 5
(Optional) To disable the ICMP inspection engine, enter the following command:
FWSM/contexta(config)# no fixup protocol icmp
Reloading the Firewall Services Module
If you need to reload the FWSM, see the following sections:
•
Reloading the FWSM from the FWSM CLI, page 17-8
•
Reloading the FWSM from the Switch, page 17-9
Reloading the FWSM from the FWSM CLI
In multiple mode, you can only reload from the system execution space. To reload the FWSM from the
FWSM CLI, enter the following command:
FWSM# reload
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Reloading the FWSM from the Switch
If you need to reload the FWSM from the switch into the current partition, enter the command for your
operating system. See the “Resetting the FWSM or Booting from a Specific Partition” section on
page 2-13 for other options.
•
For Cisco IOS software, enter the following command:
Router# hw-module module mod_num reset
•
For Catalyst operating system software, enter the following command:
Console> (enable) reset mod_num
Troubleshooting Passwords and AAA
If you forget passwords, or you create a lockout situation because of AAA settings, the following
sections describe how to recover:
•
Clearing the Application Partition Passwords and AAA Settings, page 17-9
•
Recovering the Maintenance Partition Passwords, page 17-10
Clearing the Application Partition Passwords and AAA Settings
If you forget the login and enable passwords, or you create a lockout situation because of AAA settings,
you can reset the passwords and portions of AAA configuration to the default values. You must log into
the maintenance partition to perform this procedure:
Step 1
To boot the FWSM into the maintenance partition, enter the command for your operating system:
•
For Cisco IOS software, enter the following command:
Router# hw-module module mod_num reset cf:1
•
For Catalyst operating system software, enter the following command:
Console> (enable) reset mod_num cf:1
Step 2
To session into the FWSM, enter the command for your operating system:
•
For Cisco IOS software, enter the following command:
Router# session slot mod_num processor 1
•
For Catalyst operating system software, enter the following command:
Console> (enable) session mod_num
Step 3
To log into the maintenance partition as root, enter the following command:
Login: root
Step 4
Enter the password at the prompt:
Password: password
By default, the password is “cisco.”
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Step 5
To clear the login and enable passwords, as well as the aaa authentication console and aaa
authorization command commands, enter the following command:
[email protected]# clear passwd cf:{4 | 5}
Step 6
Follow the screen prompts, as follows:
Do you wish to erase the passwords? [yn] y
The following lines will be removed from the configuration:
enable password 8Ry2YjIyt7RRXU24 encrypted
passwd 2KFQnbNIdI.2KYOU encrypted
Do you want to remove the commands listed above from the configuration?
[yn] y
Passwords and aaa commands have been erased.
Recovering the Maintenance Partition Passwords
If you forget the passwords for the maintenance partition, you can reset them to the default values. You
must be logged into the application partition. In multiple mode, you can only reset the passwords from
the system execution space.
To reset the maintenance passwords, enter the following command:
FWSM# clear mp-passwd
Other Troubleshooting Tools
The FWSM provides other troubleshooting tools to be used in conjunction with technical support:
•
Viewing Debug Messages, page 17-10
•
Capturing Packets, page 17-10
•
Viewing the Crash Dump, page 17-11
Viewing Debug Messages
Debug messages can slow the FWSM performance considerably. However, if you are troubleshooting
the FWSM, debug messages can be useful. We recommend contacting technical support to help you
debug your FWSM. To enable debug messages, see the debug commands in the Catalyst 6500 Series
Switch and Cisco 7600 Series Router Firewall Services Module Command Reference.
Capturing Packets
Capturing packets is sometimes useful when troubleshooting connectivity problems or monitoring
suspicious activity. The FWSM can track packet information for traffic that passes through the
general-purpose processor, including management traffic and inspection engines. The FWSM cannot
capture traffic that goes through the network processors (such as most through traffic). We recommend
contacting technical support if you want to use the packet capture feature. See the capture command in
the Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Command
Reference.
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Viewing the Crash Dump
If the FWSM crashes, you can view the crash dump information. We recommend contacting technical
support if you want to interpret the crash dump. See the show crashdump command in the Catalyst 6500
Series Switch and Cisco 7600 Series Router Firewall Services Module Command Reference.
Common Problems
This section describes common problems with the FWSM, and how you might resolve them.
Symptom When you reset the FWSM from the switch CLI, the system always boots into the maintenance
partition.
Possible Cause The default boot partition is set to cf:1.
Recommended Action Change the default boot partition according to the “Setting the Default Boot
Partition” section on page 2-13.
Symptom You are unable to log into the maintenance partition with the same password as the application
partition.
Possible Cause The application partition and the maintenance partition have different password
databases.
Recommended Action Use the password appropriate for your partition. See the “Changing the
Passwords” section on page 6-1 for more information.
Symptom Traffic does not pass through the FWSM.
Possible Cause The VLANs are not configured on the switch or are not assigned to the FWSM.
Recommended Action Configure the VLANs and assign them to the FWSM according to the
“Assigning VLANs to the Firewall Services Module” section on page 2-2.
Symptom You cannot configure a VLAN interface within a context.
Possible Cause You did not assign that VLAN to the context.
Recommended Action Assign VLANs to contexts according to the “Configuring a Security Context”
section on page 5-19.
Symptom You cannot add more than one switched virtual interface (SVI) to the MSFC.
Possible Cause You did not enable multiple SVIs.
Recommended Action Enable multiple SVIs according to the “Adding Switched Virtual Interfaces to
the MSFC” section on page 2-5.
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Symptom The context configuration was not saved, and was lost when you reloaded.
Possible Cause You did not save each context within the context execution space. If you are
configuring contexts at the command line, you did not save the context before you changed to the
next context.
Recommended Action Save each context within the context execution space using the copy run start
command. You cannot save contexts from the system execution space.
Symptom You cannot make a Telnet connection or SSH to the FWSM interface.
Possible Cause You did not enable Telnet or SSH to the FWSM.
Recommended Action Enable Telnet or SSH to the FWSM according to the “Allowing Telnet” section
on page 11-1 or the “Allowing SSH” section on page 11-2.
Symptom You cannot ping the FWSM interface.
Possible Cause You did not enable ICMP to the FWSM.
Recommended Action Enable ICMP to the FWSM according to the “Allowing ICMP to and from the
FWSM” section on page 11-10.
Symptom You cannot ping through the FWSM, even though the ACL allows it.
Possible Cause You did not enable the ICMP inspection engine or apply ACLs on both the source and
destination interfaces.
Recommended Action Because ICMP is a connectionless protocol, the FWSM does not automatically
allow returning traffic through. In addition to an ACL on the source interface, you either need to
apply an ACL to destination interface to allow replying traffic, or enable the ICMP inspection engine,
which treats ICMP connections as stateful connections.
Symptom Traffic does not go through the FWSM from a higher security interface to a lower security
interface.
Possible Cause You did not apply an ACL to the higher security interface to allow traffic through.
Unlike the PIX firewall, the FWSM does not automatically allow traffic to pass between interfaces.
Recommended Action Apply an ACL to the source interface to allow traffic through. See the “Adding
an Extended Access Control List” section on page 10-13.
Symptom Traffic does not pass between two interfaces on the same security level.
Possible Cause You did not enable the feature that allows traffic to pass between interfaces on the
same security level.
Recommended Action Enable this feature according to the “Allowing Communication Between
Interfaces on the Same Security Level” section on page 6-8.
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Symptom When the FWSM fails over, the secondary unit does not pass traffic.
Possible Cause You did not assign the same VLANs for both units.
Recommended Action Make sure to assign the same VLANs to both units in the switch configuration.
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A P P E N D I X
A
Specifications
This chapter lists the specifications of the Firewall Services Module (FWSM) and includes the following
sections:
•
Physical Attributes, page A-1
•
Feature Limits, page A-2
•
Managed System Resources, page A-3
•
Fixed System Resources, page A-4
•
Rule Limits, page A-5
Physical Attributes
Table A-1 lists the physical attributes of the FWSM.
Table A-1
Physical Attributes
Specification
Description
Bandwidth
CEF256 line card with a 6-Gbps path to the Switch Fabric Module (if
present) or the 32-Gbps shared bus.
Memory
Modules per switch
•
1 GB RAM.
•
128-MB Flash memory.
Maximum four modules per switch.
If you are using failover, you can still only have four modules per
switch even if two of them are in standby mode.
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Appendix A
Specifications
Feature Limits
Feature Limits
Table A-2 lists the feature limits for the FWSM.
Table A-2
Feature Limits
Context Mode
Specification
Single
Multiple
AAA servers (RADIUS and
TACACS+)
16
4 per context
Failover interface monitoring
250
250 divided between all contexts
Filtering servers (Websense
Enterprise and Sentian by
N2H2)
16
4 per context
Jumbo Ethernet packets
8500 Bytes
8500 Bytes
Security contexts
N/A
100 security contexts (depending on your
software license).
Syslog servers
16
4 per context
256
256 per context
VLAN interfaces
Routed Mode
The FWSM has an overall limit of 1000 VLAN
interfaces divided between all contexts. You
can share outside interfaces between contexts,
and in some circumstances, you can share
inside interfaces.
Transparent Mode
2
2 per context
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Specifications
Managed System Resources
Managed System Resources
Table A-3 lists the managed system resources of the FWSM. You can manage these resources per context
using the resource manager. See the “Configuring Resource Management” section on page 5-11.
Table A-3
Managed System Resources
Context Mode
Specification
Single
Multiple
MAC addresses (transparent
firewall mode only)
64,000
64,000 divided between all contexts
Hosts allowed to connect
256,000
through the FWSM, concurrent
256,000 divided between all contexts
Inspection engine connections, 10,000 per second
rate
10,000 per second divided between all contexts
IPSec management
connections, concurrent
5
5 per context
PDM management sessions,
concurrent1
5
NAT translations, concurrent
256,000
256,000 divided between all contexts
SSH management
connections, concurrent
5
5 per context
System messages, rate
30,000 per second divided between all contexts
30,000 per second
for messages sent to for messages sent to the FWSM terminal or
the FWSM terminal buffer
or buffer
25,000 per second divided between all contexts
for messages sent to a syslog server
25,000 per second
for messages sent to
a syslog server
2
Maximum of 10 divided between all contexts
Up to 5 per context
Maximum of 32 divided between all contexts
Maximum of 100 divided between all contexts
TCP3 or UDP4 connections
999,900
999,900 divided between all contexts
between any two hosts,
100,000 per second 100,000 per second divided between all
including connections between
contexts
one host and multiple other
hosts, concurrent and rate5
Telnet management
connections, concurrent
5
5 per context
Maximum of 100 connections divided between
all contexts.
1. PDM 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 PDM sessions represents a limit of
64 HTTPS connections.
2. Secure Shell
3. Transmission Control Protocol
4. User Datagram Protocol
5. Because Port Address Translation (PAT) requires a separate translation for each connection, the effective limit of connections
using PAT is the translation limit (256,000), not the higher connection limit. To use the connection limit, you need to use
NAT, which allows multiple connections using the same translation session.
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Specifications
Fixed System Resources
Fixed System Resources
Table A-4 lists the fixed system resources of the FWSM.
Table A-4
Fixed System Resources
Context Mode
Specification
1
AAA connections, rate
Single
Multiple
80 per second
80 per second divided between all contexts
ACL logging flows, concurrent 32,000
32,000 divided between all contexts
Alias statements
1,000
1,000 divided between all contexts
ARP2 table entries, concurrent
64,000
64,00 divided between all contexts
Global statements
1,051
1,051 divided between all contexts
Inspection engine (fixup)
statements
32
32 per context3
NAT statements
2,000
2,000 divided between all contexts
Packet reassembly, concurrent
30,000
30,000 fragments divided between all contexts
Route table entries, concurrent
32,000
32,000 divided between all contexts
Shun statements
5,000
5,000 divided between all contexts
SIP connections, concurrent
5,000
5,000 divided between all contexts
Static NAT statements
2,000
2,000 divided between all contexts
User authentication sessions,
concurrent
50,000
50,000 divided between all contexts
User authorization sessions,
concurrent
150,000
150,000 divided between all contexts
Maximum 15
sessions per user.
Maximum 15 sessions per user.
1. authentication, authorization, and accounting
2. Address Resolution Protocol
3. This limit includes the following inspection engines that are enabled by default, making the total number of configurable
inspection engines 27: TFTP, Sun RPC over UDP, NetBIOS NameServer, XDMCP, and CUSeeMe. The OraServ and
RealAudio inspection engines, which are also enabled by default, do not affect this limit.
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Specifications
Rule Limits
Rule Limits
The FWSM supports approximately 80K rules for the entire system in single mode, and 142K rules for
multiple mode.
In multiple context mode, each context supports at most 12,130 rules, but the actual number of rules
supported in a context might be less, depending on how many contexts you have. A context belongs to
one of 12 pools that offers a maximum of 12,130 rules. The FWSM assigns contexts to the pools in the
order they are loaded at startup. For example, if you have 12 contexts, each context is assigned to its own
pool, and can use 12,130 rules. If you add one more context, then context number 1 and the new context
number 13 are both assigned to pool 1, and can use 12,130 rules divided between them; the other
11 contexts continue to use 12,130 rules each. If you delete contexts, the pool membership does not shift,
so you might have some unequal distribution until you reboot, at which time the contexts are evenly
distributed.
Note
Rules are used up on a first come, first served basis, so one context might use more rules than another
context.
Table A-5 lists the maximum number of each rule type.
Table A-5
Rule Limits
Context Mode
Specification
Single
Multiple (Maximum per Pool)
AAA Rules
3,942
6061
ACEs2
63,078
9,704
Downloaded ACEs for network access
authorization
3,000
3,000
Established Rules
788
121
3,942
606
ICMP , Telnet, SSH, and HTTP Rules 2,365
363
Policy NAT ACEs
606
Filter Rules
3
4
3,942
1. For example, if you have 96 contexts evenly distributed among the 12 pools, so there are 8 contexts per pool, each context
can use 75 filter rules, if evenly divided.
2. access control entries
3. Internet Control Message Protocol
4. HyperText Transfer Protocol
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Specifications
Rule Limits
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A P P E N D I X
B
Sample Configurations
This chapter illustrates and describes a number of common ways to implement the Firewall Services
Module (FWSM). It includes the following topics:
•
Routed Mode Examples, page B-1
•
Transparent Mode Examples, page B-15
Routed Mode Examples
This section includes the following topics:
•
Example 1: Security Contexts With Outside Access, page B-1
•
Example 2: Single Mode Using Same Security Level, page B-5
•
Example 3: Shared Resources for Multiple Contexts, page B-8
•
Example 4: Failover, page B-11
Example 1: Security Contexts With Outside Access
This configuration creates three security contexts plus the admin context, each with an inside and an
outside interface. The Customer C context includes a DMZ interface where a Websense server for HTTP
filtering resides on the service provider premises. (See Figure B-1.)
Inside hosts can access the Internet through the outside using dynamic NAT or PAT, but no outside hosts
can access the inside.
The Customer A context has a second network behind an inside router.
The admin context allows SSH sessions to the FWSM from one host.
Each customer context belongs to a class that limits its resources (gold, silver, or bronze).
Although inside IP addresses can be the same across contexts when the VLANs are unique, keeping them
unique is easier to manage.
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Appendix B
Sample Configurations
Routed Mode Examples
Figure B-1
Example 1
Internet
MSFC
209.165.201.1
VLAN 3
Admin Context
outside
209.165.201.2
customerA
outside
209.165.201.3
customerB
outside
209.165.201.4
customerC
outside
209.165.201.5
DMZ
192.168.2.1
VLAN 8
inside
10.1.1.1
inside
10.1.3.1
inside
10.1.2.1
VLAN 4
Admin
Network
VLAN 5
customerA
Network 1
Websense
192.168.2.2
inside
10.1.4.1
VLAN 6
customerB
Network
VLAN 7
customerC
Network
10.1.2.2
192.168.1.1
customerA
Network 2
104645
Management host
10.1.1.75
See the following sections for the configurations for this scenario:
•
Example 1: System Configuration, page B-2
•
Example 1: Admin Context Configuration, page B-3
•
Example 1: Customer A Context Configuration, page B-4
•
Example 1: Customer B Context Configuration, page B-4
•
Example 1: Customer C Context Configuration, page B-4
•
Example 1: Switch Configuration, page B-5
Example 1: System Configuration
You must first enable multiple context mode using the mode multiple command. Then enter the
activation key to allow more than two contexts using the activation-key command. The mode and the
activation key are not stored in the configuration file, even though they do endure reboots. If you view
the configuration on the FWSM using the write terminal, show startup, or show running commands,
the mode displays after the FWSM Version (blank means single mode, “<system>” means you are in
multiple mode in the system configuration, and <context> means you are in multiple mode in a context).
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Sample Configurations
Routed Mode Examples
hostname Farscape
password passw0rd
enable password chr1cht0n
admin-context admin
context admin
allocate-interface vlan3
allocate-interface vlan4
config-url disk://admin.cfg
class default
context customerA
description This is the context for customer A
allocate-interface vlan3
allocate-interface vlan5
config-url disk://contexta.cfg
class gold
context customerB
description This is the context for customer B
allocate-interface vlan3
allocate-interface vlan6
config-url disk://contextb.cfg
class silver
context customerC
description This is the context for customer C
allocate-interface vlan3
allocate-interface vlan7-vlan8
config-url disk://contextc.cfg
class bronze
class gold
limit-resource all 7%
limit-resource rate conns 2000
limit-resource conns 20000
class silver
limit-resource all 5%
limit-resource rate conns 1000
limit-resource conns 10000
class bronze
limit-resource all 3%
limit-resource rate conns 500
limit-resource conns 5000
Example 1: Admin Context Configuration
The host at 10.1.1.75 can access the context using SSH, which requires a certificate to be generated using
the ca generate rsa key modulus command and saved using the ca save all command. The certificate is
saved in Flash memory.
hostname Admin
domain isp
nameif vlan3 outside security0
nameif vlan4 inside security100
passwd secret1969
enable password h1andl0
ip address outside 209.165.201.2 255.255.255.224
ip address inside 10.1.1.1 255.255.255.0
route outside 0 0 209.165.201.1 1
ssh 10.1.1.75 255.255.255.255 inside
nat (inside) 1 10.1.1.0 255.255.255.0
global (outside) 1 209.165.201.10-209.165.201.29 [This context uses dynamic NAT for inside
users that access the outside]
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Sample Configurations
Routed Mode Examples
static (inside,outside) 209.165.201.30 10.1.1.75 netmask 255.255.255.255 [The host at
10.1.1.75 has access to the Websense server in Customer C, so it needs a static
translation for use in Customer C’s ACL]
access-list INTERNET extended permit ip any any
access-group INTERNET in interface inside [Allows all inside hosts to access the outside
for any IP traffic]
Example 1: Customer A Context Configuration
nameif vlan3 outside security0
nameif vlan5 inside security100
passwd hell0!
enable password enter55
ip address outside 209.165.201.3 255.255.255.224
ip address inside 10.1.2.1 255.255.255.0
route outside 0 0 209.165.201.1 1
route inside 192.168.1.0 255.255.255.0 10.1.2.2 1 [The Customer A context has a second
network behind an inside router that requires a static route. All other traffic is handled
by the default route pointing to the MSFC.]
nat (inside) 1 10.1.2.0 255.255.255.0
global (outside) 1 interface [This context uses dynamic PAT for inside users that access
that outside. The outside interface address is used for the PAT address]
access-list INTERNET extended permit ip any any
access-group INTERNET in interface inside [Allows all inside hosts to access the outside
for any IP traffic]
Example 1: Customer B Context Configuration
nameif vlan3 outside security0
nameif vlan6 inside security100
passwd tenac10us
enable password defen$e
ip address outside 209.165.201.4 255.255.255.224
ip address inside 10.1.3.1 255.255.255.0
route outside 0 0 209.165.201.1 1
nat (inside) 1 10.1.3.0 255.255.255.0
global (outside) 1 209.165.201.9 netmask 255.255.255.255 [This context uses dynamic PAT
for inside users that access the outside]
access-list INTERNET extended permit tcp any any eq http
access-list INTERNET extended permit tcp any any eq https
access-group INTERNET in interface inside [Inside users can only access HTTP and HTTPS
servers on the outside]
Example 1: Customer C Context Configuration
nameif vlan3 outside security0
nameif vlan7 inside security100
nameif vlan8 dmz security50
passwd fl0wer
enable password treeh0u$e
ip address outside 209.165.201.5 255.255.255.224
ip address inside 10.1.4.1 255.255.255.0
ip address dmz 192.168.2.1 255.255.255.0
route outside 0 0 209.165.201.1 1
url-server (dmz) vendor websense host 192.168.2.2 url-block block 50
url-cache dst 128
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Sample Configurations
Routed Mode Examples
filter url http 10.1.4.0 255.255.255.0 0 0 [When inside users access an HTTP server, the
FWSM consults with a Websense server to determine if the traffic is allowed]
nat (inside) 1 10.1.4.0 255.255.255.0
global (outside) 1 209.165.201.9 netmask 255.255.255.255 [This context uses dynamic NAT
for inside users that access the outside]
static (dmz,outside) 209.165.201.6 192.168.2.2 netmask 255.255.255.255 [A host on the
admin context requires access to the Websense server for management using pcAnywhere, so
the Websense server requires a static translation]
access-list INTERNET extended permit ip any any
access-group INTERNET in interface inside [Allows all inside hosts to access the outside
for any IP traffic. Because there is no NAT from inside to dmz, you do not have to deny
traffic from accessing the dmz.]
access-list MANAGE extended permit tcp host 209.165.201.30 host 209.165.201.6 eq
pcanywhere-data
access-list MANAGE extended permit udp host 209.165.201.30 host 209.165.201.6 eq
pcanywhere-status
access-group MANAGE in interface outside [This ACL allows the management host to use
pcAnywhere on the Websense server]
access-list WEBSENSE extended permit tcp host 192.168.2.2 any eq http [The Websense server
needs to access the Websense updater server on the outside]
access-group WEBSENSE in interface dmz
Example 1: Switch Configuration
The following lines in the Cisco IOS switch configuration relate to the FWSM:
...
firewall module 8 vlan-group 1
firewall vlan-group 1 3-8
interface vlan 3
ip address 209.165.201.1 255.255.255.224
no shut
...
Example 2: Single Mode Using Same Security Level
This configuration creates three internal interfaces. Two of the interfaces connect to departments that are
on the same security level, which allows all hosts to communicate without using NAT. The DMZ
interface hosts a Syslog server. The management host on the outside needs access to the Syslog server
and the FWSM. To connect to the FWSM, the host uses a VPN connection. The FWSM uses RIP on the
inside interfaces to learn routes. Because the FWSM does not advertise routes with RIP, the MSFC needs
to use static routes for FWSM traffic (See Figure B-2.)
The Department networks are allowed to access the Internet, and use PAT.
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Appendix B
Sample Configurations
Routed Mode Examples
Figure B-2
Example 2
Management Host
209.165.200.225
Internet
MSFC
209.165.201.1
outside VLAN 3
209.165.201.3
Department 1
dept1
10.1.1.1
VLAN 5
DMZ
192.168.2.1
VLAN 10
Syslog Server
192.168.2.2
dept2
10.1.2.1
VLAN 4
Department 2
10.1.2.2
192.168.1.1
Department 2
Network 2
104646
VLAN 9
See the following sections for the configurations for this scenario:
•
Example 2: FWSM Configuration, page B-6
•
Example 2: Switch Configuration, page B-7
Example 2: FWSM Configuration
nameif vlan3 outside security0
nameif vlan4 dept2 security100
nameif vlan5 dept1 security100
nameif vlan10 dmz security50
passwd g00fba11
enable password gen1u$
hostname Buster
same-security-traffic permit inter-interface
ip address outside 209.165.201.3 255.255.255.224
ip address dept2 10.1.2.1 255.255.255.0
ip address dept2 10.1.1.1 255.255.255.0
ip address dmz 192.168.2.1 255.255.255.0
route outside 0 0 209.165.201.1 1
nat (dept1) 1 10.1.1.0 255.255.255.0
nat (dept2) 1 10.1.2.0 255.255.255.0
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Sample Configurations
Routed Mode Examples
global (outside) 1 209.165.201.9 netmask 255.255.255.255 [The dept1 and dept2 networks use
PAT when accessing the outside]
static (dmz,outside) 209.165.201.5 192.168.2.2 netmask 255.255.255.255 [The syslog server
needs a static translation so the outside management host can access the server]
access-list DEPTS extended permit ip any any
access-group DEPTS in interface dept1
access-group DEPTS in interface dept2 [Allows all dept1 and dept2 hosts to access the
outside for any IP traffic]
access-list MANAGE extended permit tcp host 209.165.200.225 host 209.165.201.5 eq telnet
access-group MANAGE in interface outside [This ACL allows the management host to access
the syslog server]
rip dept2 default version 2 authentication md5 scorpius 1 [Advertises the FWSM IP address
as the default gateway for the downstream router. The FWSM does not advertise a default
route to the MSFC.]
rip dept2 passive version 2 authentication md5 scorpius 1 [Listens for RIP updates from
the downstream router. The FWSM does not listen for RIP updates from the MSFC because a
default route to the MSFC is all that is required.]
isakmp policy 1 authentication pre-share [The client uses a pre-shared key to connect to
the FWSM over IPSec. The key is the password in the username command below.]
isakmp policy 1 encryption 3des
isakmp policy 1 group 2
isakmp policy 1 hash sha
isakmp enable outside
crypto ipsec transform-set vpn_client esp-3des esp-sha-hmac
username admin password passw0rd
crypto ipsec transform-set vpn esp-3des esp-sha-hmac
crypto dynamic-map vpn_client 1 set transform-set vpn
crypto map telnet_tunnel 1 ipsec-isakmp dynamic vpn_client
crypto map telnet_tunnel interface outside
crypto map telnet_tunnel client authentication LOCAL
ip local pool client_pool 10.1.1.2
access-list VPN_SPLIT extended permit ip host 209.165.201.3 host 10.1.1.2
vpngroup admin address-pool client_pool
vpngroup admin split-tunnel VPN_SPLIT
vpngroup admin password $ecure23
telnet 10.1.1.2 255.255.255.255 outside
telnet timeout 30
logging trap 5
logging host dmz 192.168.2.2 [System messages are sent to the syslog server on the DMZ
network]
logging on
Example 2: Switch Configuration
The following lines in the switch configuration relate to the FWSM:
Catalyst OS on the supervisor:
set vlan 3-5,9,10 firewall-vlan 8
Cisco IOS software on the MSFC:
interface vlan 3
ip address 209.165.201.1 255.255.255.224
no shut
...
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Sample Configurations
Routed Mode Examples
Example 3: Shared Resources for Multiple Contexts
This configuration includes multiple contexts for multiple departments within a company. Each
department has its own security context so that each department can have its own security policy.
However, the syslog, mail, and AAA servers are shared across all departments. These servers are placed
on a shared VLAN (See Figure B-3.)
Department 1 has a web server that outside users who are authenticated by the AAA server can access.
Figure B-3
Example 3
Internet
MSFC
209.165.201.2
VLAN 200
Outside
209.165.201.3
Admin
Context
Inside
10.1.0.1
Outside
209.165.201.4
Department 2
Department 1
Shared
10.1.1.1
VLAN 201
Inside
10.1.2.1
VLAN 202
Web Server
10.1.2.3
Config Server Admin Host
10.1.0.15
10.1.0.16
Outside
209.165.201.5
Shared
10.1.1.2
Inside
10.1.3.1
Shared
10.1.1.3
VLAN 203
Inside
VLAN 300
VLAN 300
Shared
Network
AAA Server
10.1.1.6
Mail Server
10.1.1.7
Syslog Server
10.1.1.8
104647
VLAN 300
See the following sections for the configurations for this scenario:
•
Example 3: System Configuration, page B-9
•
Example 3: Admin Context Configuration, page B-9
•
Example 3: Department 1 Context Configuration, page B-10
•
Example 3: Department 2 Context Configuration, page B-11
•
Example 3: Switch Configuration, page B-11
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Sample Configurations
Routed Mode Examples
Example 3: System Configuration
You must first enable multiple context mode using the mode multiple command. Then enter the
activation key to allow more than two contexts using the activation-key command. The mode and the
activation key are not stored in the configuration file, even though they do endure reboots. If you view
the configuration on the FWSM using the write terminal, show startup, or show running commands,
the mode displays after the FWSM Version (blank means single mode, “<system>” means you are in
multiple mode in the system configuration, and <context> means you are in multiple mode in a context).
hostname Ubik
password pkd55
enable password deckard69
admin-context admin
context admin
allocate-interface vlan200
allocate-interface vlan201
allocate-interface vlan300
config-url disk://admin.cfg
context department1
allocate-interface vlan200
allocate-interface vlan202
allocate-interface vlan300
config-url ftp://admin:[email protected]/dept1.cfg
context department2
allocate-interface vlan200
allocate-interface vlan203
allocate-interface vlan300
config-url ftp://admin:[email protected]/dept2.cfg
Example 3: Admin Context Configuration
hostname Admin
nameif vlan200 outside security0
nameif vlan201 inside security100
nameif vlan300 shared security50
passwd v00d00
enable password d011
ip address outside 209.165.201.3 255.255.255.224
ip address inside 10.1.0.1 255.255.255.0
ip address shared 10.1.1.1 255.255.255.0
route outside 0 0 209.165.201.2 1
nat (inside) 1 10.1.0.0 255.255.255.0
global (outside) 1 209.165.201.6 netmask 255.255.255.255 [This context uses PAT for inside
users that access the outside]
global (shared) 1 10.1.1.30 [This context uses PAT for inside users that access the shared
network]
static (inside,outside) 209.165.201.7 10.1.0.15 netmask 255.255.255.255 [Because this host
can access the web server in the Department 1 context, it requires a static translation]
static (inside,shared) 10.1.1.78 10.1.0.15 netmask 255.255.255.255 [Because this host has
management access to the servers on the Shared interface, it requires a static translation
to be used in an ACL]
access-list INTERNET extended permit ip any any
access-group INTERNET in interface inside [Allows all inside hosts to access the outside
and shared network for any IP traffic]
access-list SHARED extended permit ip host 10.1.1.78 any
access-list SHARED extended permit tcp host 10.1.1.30 host 10.1.1.7 eq smtp
access-group SHARED out interface shared [This ACL allows only mail traffic from the
inside network to exit out the shared interface, but allows the admin host to access any
server. Note that the translated addresses are used.]
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Sample Configurations
Routed Mode Examples
telnet 10.1.0.15 255.255.255.255 inside [Allows 10.1.0.15 to access the admin context
using Telnet. From the admin context, you can access all other contexts.]
aaa-server AAA-SERVER protocol tacacs+
aaa-server AAA-SERVER (shared) host 10.1.1.6 TheUauthKey
aaa authentication telnet console AAA-SERVER [The host at 10.1.0.15 must authenticate with
the AAA server to log in]
logging trap 6
logging host shared 10.1.1.8 [System messages are sent to the syslog server on the Shared
network]
logging on
Example 3: Department 1 Context Configuration
nameif vlan200 outside security0
nameif vlan202 inside security100
nameif vlan300 shared security50
passwd cugel
enable password rhialto
ip address outside 209.165.201.4 255.255.255.224
ip address inside 10.1.2.1 255.255.255.0
ip address shared 10.1.1.2 255.255.255.0
nat (inside) 1 10.1.2.0 255.255.255.0
global (outside) 1 209.165.201.8 netmask 255.255.255.255 [The inside network uses PAT when
accessing the outside]
global (shared) 1 10.1.1.31-10.1.1.37 [The inside network uses dynamic NAT when accessing
the shared network]
static (inside,outside) 209.165.201.9 10.1.2.3 netmask 255.255.255.255 [The web server can
be accessed from outside and requires a static translation]
access-list INTERNET extended permit ip any any
access-group INTERNET in interface inside [Allows all inside hosts to access the outside
and shared network for any IP traffic]
access-list WEBSERVER extended permit ip host 209.165.201.7 host 209.165.201.9 [This ACE
allows the management host (its translated address) on the admin context to access the web
server for management (it can use any IP protocol)]
access-list WEBSERVER extended permit tcp any eq http host 209.165.201.9 eq http [This ACE
allows any outside address to access the web server with HTTP]
access-group WEBSERVER in interface outside
access-list MAIL extended permit tcp host 10.1.1.31 eq smtp host 10.1.1.7 eq smtp
access-list MAIL extended permit tcp host 10.1.1.32 eq smtp host 10.1.1.7 eq smtp
access-list MAIL extended permit tcp host 10.1.1.33 eq smtp host 10.1.1.7 eq smtp
access-list MAIL extended permit tcp host 10.1.1.34 eq smtp host 10.1.1.7 eq smtp
access-list MAIL extended permit tcp host 10.1.1.35 eq smtp host 10.1.1.7 eq smtp
access-list MAIL extended permit tcp host 10.1.1.36 eq smtp host 10.1.1.7 eq smtp
access-list MAIL extended permit tcp host 10.1.1.37 eq smtp host 10.1.1.7 eq smtp
access-group MAIL out interface shared [This ACL allows only mail traffic from the inside
network to exit out the shared interface. Note that the translated addresses are used.]
aaa-server AAA-SERVER protocol tacacs+
aaa-server AAA-SERVER (shared) host 10.1.1.6 TheUauthKey
aaa authentication match WEBSERVER outside AAA-SERVER [All traffic matching the WEBSERVER
ACL must authenticate with the AAA server]
logging trap 4
logging host shared 10.1.1.8 [System messages are sent to the syslog server on the Shared
network]
logging on
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Sample Configurations
Routed Mode Examples
Example 3: Department 2 Context Configuration
nameif vlan200 outside security0
nameif vlan203 inside security100
nameif vlan300 shared security50
passwd maz1r1an
enable password ly0ne$$e
ip address outside 209.165.201.5 255.255.255.224
ip address inside 10.1.3.1 255.255.255.0
ip address shared 10.1.1.3 255.255.255.0
route outside 0 0 209.165.201.2 1
nat (inside) 1 10.1.3.0 255.255.255.0
global (outside) 1 209.165.201.10 netmask 255.255.255.255 [The inside network uses PAT
when accessing the outside]
global (shared) 1 10.1.1.38 [The inside network uses PAT when accessing the shared
network]
access-list INTERNET extended permit ip any any
access-group INTERNET in interface inside [Allows all inside hosts to access the outside
and shared network for any IP traffic]
access-list MAIL extended permit tcp host 10.1.1.38 host 10.1.1.7 eq smtp
access-group MAIL out interface shared [This ACL allows only mail traffic from the inside
network to exit out the shared interface. Note that the translated PAT address is used.]
logging trap 3
logging host shared 10.1.1.8 [System messages are sent to the syslog server on the Shared
network]
logging on
Example 3: Switch Configuration
The following lines in the Cisco IOS switch configuration relate to the FWSM:
...
firewall module 6 vlan-group 1
firewall vlan-group 1 200-203,300
interface vlan 200
ip address 209.165.201.2 255.255.255.224
no shut
...
Example 4: Failover
This configuration shows a routed, multiple context mode FWSM in one switch, and another FWSM in
a second switch acting as a backup (see Figure B-4). Each context (A, B, and C) monitors the inside
interface, and context A, which is the admin context, also monitors the outside interface. Because the
outside interface is shared among all contexts, monitoring in one context benefits all contexts.
The secondary FWSM is also in routed, multiple context mode, and has the same software version.
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Sample Configurations
Routed Mode Examples
Figure B-4
Example 4
Internet
VLAN 100
Active Switch
209.165.201.3
209.165.201.2
MSFC
HSRP IP:
209.165.201.5
209.165.201.7
209.165.201.4
Trunk:
VLANs 200, 201,
202, 203, 10, 11
Primary
FWSM
10.0.1.1
Failover Links:
VLAN 10
10.0.3.1
VLAN 202
VLAN 203
209.165.201.8
Secondary
FWSM
VLAN 11
10.0.1.2
10.0.2.1
VLAN 201
209.165.201.6
10.0.3.2
10.0.2.2
Context A
Context B
Context C
104893
VLAN 200
MSFC
HSRP IP:
209.165.201.5
Standby Switch
See the following sections for the configurations for this scenario:
•
Example 4: Primary FWSM Configuration, page B-12
•
Example 4: Secondary FWSM System Configuration, page B-14
•
Example 4: Switch Configuration, page B-14
Example 4: Primary FWSM Configuration
The following sections include the configuration for the primary FWSM:
•
Example 4: System Configuration (Primary), page B-12
•
Example 4: Context A Configuration (Primary), page B-13
•
Example 4: Context B Configuration (Primary), page B-13
•
Example 4: Context C Configuration (Primary), page B-14
Example 4: System Configuration (Primary)
You must first enable multiple context mode using the mode multiple command. Then enter the
activation key to allow more than two contexts using the activation-key command. The mode and the
activation key are not stored in the configuration file, even though they do endure reboots. If you view
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Sample Configurations
Routed Mode Examples
the configuration on the FWSM using the write terminal, show startup, or show running commands,
the mode displays after the FWSM Version (blank means single mode, “<system>” means you are in
multiple mode in the system configuration, and <context> means you are in multiple mode in a context).
hostname primary
enable password farscape
password crichton
failover lan interface faillink vlan 10
failover link statelink vlan 11
failover lan unit primary
failover interface ip faillink 192.168.253.1 255.255.255.252 standby 192.168.253.2
failover interface ip statelink 192.168.253.5 255.255.255.252 standby 192.168.253.6
failover interface-policy 50%
failover replication http
failover
admin-context contexta
context contexta
allocate-interface vlan200
allocate-interface vlan201
config-url disk://contexta.cfg
context contextb
allocate-interface vlan200
allocate-interface vlan202
config-url ftp://admin:[email protected]/contextb.cfg
context contextc
allocate-interface vlan200
allocate-interface vlan203
config-url ftp://admin:[email protected]/contextc.cfg
Example 4: Context A Configuration (Primary)
nameif vlan200 outside security0
nameif vlan201 inside security100
passwd secret1969
enable password h1andl0
ip address outside 209.165.201.2 255.255.255.224 standby 209.165.201.6
ip address inside 10.0.3.1 255.255.255.0 standby 10.0.3.2
monitor-interface inside
monitor-interface outside
nat (inside) 1 0.0.0.0 0.0.0.0 0 0
global (outside) 1 209.165.201.10 netmask 255.255.255.224 [This context uses dynamic PAT
for inside users that access the outside]
route outside 0 0 209.165.201.5 1
telnet 10.0.3.75 255.255.255.255 inside
access-list INTERNET extended permit ip any any
access-group INTERNET in interface inside [Allows all inside hosts to access the outside
for any IP traffic]
Example 4: Context B Configuration (Primary)
nameif vlan200 outside security0
nameif vlan202 inside security100
passwd secret1978
enable password 7samura1
ip address outside 209.165.201.4 255.255.255.224 standby 209.165.201.8
ip address inside 10.0.2.1 255.255.255.0 standby 10.0.2.2
monitor-interface inside
nat (inside) 1 0.0.0.0 0.0.0.0 0 0
global (outside) 1 209.165.201.11 netmask 255.255.255.224 [This context uses dynamic PAT
for inside users that access the outside]
route outside 0 0 209.165.201.5 1
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Routed Mode Examples
telnet 10.0.2.14 255.255.255.255 inside
access-list INTERNET extended permit ip any any
access-group INTERNET in interface inside [Allows all inside hosts to access the outside
for any IP traffic]
Example 4: Context C Configuration (Primary)
nameif vlan200 outside security0
nameif vlan203 inside security100
passwd secret0997
enable password strayd0g
ip address outside 209.165.201.3 255.255.255.224 standby 209.165.201.7
ip address inside 10.0.1.1 255.255.255.0 standby 10.0.1.2
monitor-interface inside
nat (inside) 1 0.0.0.0 0.0.0.0 0 0
global (outside) 1 209.165.201.12 netmask 255.255.255.224 [This context uses dynamic PAT
for inside users that access the outside]
route outside 0 0 209.165.201.5 1
telnet 10.0.1.65 255.255.255.255 inside
access-list INTERNET extended permit ip any any
access-group INTERNET in interface inside [Allows all inside hosts to access the outside
for any IP traffic]
Example 4: Secondary FWSM System Configuration
You do not need to configure any contexts, just the following minimal configuration for the system.
You must first enable multiple context mode using the mode multiple command. Then enter the
activation key to allow more than two contexts using the activation-key command. The mode and the
activation key are not stored in the configuration file, even though they do endure reboots. If you view
the configuration on the FWSM using the write terminal, show startup, or show running commands,
the mode displays after the FWSM Version (blank means single mode, “<system>” means you are in
multiple mode in the system configuration, and <context> means you are in multiple mode in a context).
failover lan interface faillink vlan 10
failover interface ip faillink 192.168.253.1 255.255.255.252 standby 192.168.253.2
failover lan unit secondary
failover
Example 4: Switch Configuration
The following lines in the Cisco IOS switch configuration on both switches relate to the FWSM. For
information about configuring redundancy for the switch, see the switch documentation.
...
firewall module 1 vlan-group 1
firewall vlan-group 1 10,11,200-203
interface vlan 200
ip address 209.165.201.1 255.255.255.224
standby 200 ip 209.165.201.5
standby 200 priority 110
standby 200 preempt
standby 200 timers 5 15
standby 200 authentication Secret
no shut
interface range gigabitethernet 2/1-3
channel-group 2 mode on
switchport trunk encapsulation dot1q
no shut
...
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Sample Configurations
Transparent Mode Examples
Transparent Mode Examples
This section includes the following topics:
•
Example 5: Security Contexts With Outside Access, page B-15
•
Example 6: Failover, page B-18
Example 5: Security Contexts With Outside Access
This configuration creates three security contexts plus the admin context. Each context allows OSPF
traffic to pass between the inside and outside routers (See Figure B-5.)
Inside hosts can access the Internet through the outside, but no outside hosts can access the inside.
The admin context allows SSH sessions to the FWSM from one host.
Each customer context belongs to a class that limits its resources (gold, silver, or bronze).
Although inside IP addresses can be the same across contexts, keeping them unique is easier to manage.
Figure B-5
Example 5
Internet
MSFC
10.1.n.2
VLAN 152
VLAN 151
VLAN 150
10.1.1.1
customerA
outside
customerB
outside
customerC
outside
10.1.2.1
10.1.3.1
10.1.4.1
inside
Management host
10.1.1.75
inside
inside
inside
VLAN 4
VLAN 5
VLAN 6
VLAN 7
10.1.1.3
10.1.2.3
10.1.3.3
10.1.4.3
192.168.1.1
192.168.2.1
192.168.3.1
192.168.4.1
Admin
Network 2
customerA
Network 2
customerB
Network 2
customerC
Network 2
114999
Admin Context
outside
VLAN 153
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Sample Configurations
Transparent Mode Examples
See the following sections for the configurations for this scenario:
•
Example 1: System Configuration, page B-2
•
Example 5: System Configuration, page B-16
•
Example 5: Admin Context Configuration, page B-17
•
Example 5: Customer A Context Configuration, page B-17
•
Example 5: Customer B Context Configuration, page B-17
•
Example 5: Customer C Context Configuration, page B-18
•
Example 5: Switch Configuration, page B-18
Example 5: System Configuration
You must first enable multiple context mode using the mode multiple command. Then enter the
activation key to allow more than two contexts using the activation-key command. The mode and the
activation key are not stored in the configuration file, even though they do endure reboots. If you view
the configuration on the FWSM using the write terminal, show startup, or show running commands,
the mode displays after the FWSM Version (blank means single mode, “<system>” means you are in
multiple mode in the system configuration, and <context> means you are in multiple mode in a context).
firewall transparent
hostname Farscape
password passw0rd
enable password chr1cht0n
admin-context admin
context admin
allocate-interface vlan150
allocate-interface vlan4
config-url disk://admin.cfg
class default
context customerA
description This is the context for customer A
allocate-interface vlan151
allocate-interface vlan5
config-url disk://contexta.cfg
class gold
context customerB
description This is the context for customer B
allocate-interface vlan152
allocate-interface vlan6
config-url disk://contextb.cfg
class silver
context customerC
description This is the context for customer C
allocate-interface vlan153
allocate-interface vlan7-vlan8
config-url disk://contextc.cfg
class bronze
class gold
limit-resource all 7%
limit-resource rate conns 2000
limit-resource conns 20000
class silver
limit-resource all 5%
limit-resource rate conns 1000
limit-resource conns 10000
class bronze
limit-resource all 3%
limit-resource rate conns 500
limit-resource conns 5000
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Sample Configurations
Transparent Mode Examples
Example 5: Admin Context Configuration
The host at 10.1.1.75 can access the context using SSH, which requires a certificate to be generated using
the ca generate rsa key modulus command and saved using the ca save all command. The certificate is
saved in Flash memory.
hostname Admin
domain isp
nameif vlan150 outside security0
nameif vlan4 inside security100
passwd secret1969
enable password h1andl0
ip address 10.1.1.1 255.255.255.0
route outside 0 0 10.1.1.2 1
ssh 10.1.1.75 255.255.255.255 inside
access-list INTERNET extended permit 89 any any
access-list INTERNET extended permit ip any any
access-list OSPF extended permit 89 any any
access-group INTERNET in interface inside [Allows all inside hosts to access the outside
for any IP traffic. Also allows OSPF.]
access-group OSPF in interface outside [Allows OSPF.]
Example 5: Customer A Context Configuration
nameif vlan151 outside security0
nameif vlan5 inside security100
passwd hell0!
enable password enter55
ip address 10.1.2.1 255.255.255.0
route outside 0 0 10.1.2.2 1
access-list INTERNET extended permit 89 any any
access-list INTERNET extended permit ip any any
access-list OSPF extended permit 89 any any
access-group INTERNET in interface inside [Allows all inside hosts to access the outside
for any IP traffic. Also allows OSPF.]
access-group OSPF in interface outside [Allows OSPF.]
Example 5: Customer B Context Configuration
nameif vlan152 outside security0
nameif vlan6 inside security100
passwd tenac10us
enable password defen$e
ip address 10.1.3.1 255.255.255.0
route outside 0 0 10.1.3.2 1
access-list INTERNET extended permit 89 any any
access-list INTERNET extended permit ip any any
access-list OSPF extended permit 89 any any
access-group INTERNET in interface inside [Allows all inside hosts to access the outside
for any IP traffic. Also allows OSPF.]
access-group OSPF in interface outside [Allows OSPF.]
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Sample Configurations
Transparent Mode Examples
Example 5: Customer C Context Configuration
nameif vlan153 outside security0
nameif vlan7 inside security100
passwd fl0wer
enable password treeh0u$e
ip address 10.1.4.1 255.255.255.0
route outside 0 0 10.1.4.2 1
access-list INTERNET extended permit 89 any any
access-list INTERNET extended permit ip any any
access-list OSPF extended permit 89 any any
access-group INTERNET in interface inside [Allows all inside hosts to access the outside
for any IP traffic. Also allows OSPF.]
access-group OSPF in interface outside [Allows OSPF.]
Example 5: Switch Configuration
The following lines in the Cisco IOS switch configuration relate to the FWSM:
...
firewall multiple-vlan-interfaces
firewall module 8 vlan-group 1
firewall vlan-group 1 4-7,150-153
interface vlan 150
ip address 10.1.1.2 255.255.255.0
no shut
interface vlan 151
ip address 10.1.2.2 255.255.255.0
no shut
interface vlan 152
ip address 10.1.3.2 255.255.255.0
no shut
interface vlan 153
ip address 10.1.4.2 255.255.255.0
no shut
...
Example 6: Failover
This configuration shows a transparent, multiple context mode FWSM in one switch, and another FWSM
in a second switch acting as a backup (see Figure B-4). Each context (A, B, and C) monitors the inside
interface and outside interface.
The secondary FWSM is also in transparent, multiple context mode, and has the same software version.
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Sample Configurations
Transparent Mode Examples
Figure B-6
Example 6
Internet
VLAN 100
Active Switch
VLANs 200-202
Standby Switch
MSFC
HSRP IPs:
10.0.n.4
MSFC
HSRP IPs:
10.0.n.4
Failover Links:
VLAN 10
Trunk:
VLANs 200, 201, VLAN 11
202, 4, 5, 6, 10, 11
Mgmt IPs:
10.0.1.2
Primary
FWSM
Mgmt IPs:
10.0.1.1
10.0.3.1
10.0.2.1
Secondary
FWSM
10.0.3.2
10.0.2.2
VLAN 5
VLAN 6
Context A
Context B
115000
VLAN 4
Context C
See the following sections for the configurations for this scenario:
•
Example 6: Primary FWSM Configuration, page B-19
•
Example 6: Secondary FWSM System Configuration, page B-21
•
Example 6: Switch Configuration, page B-21
Example 6: Primary FWSM Configuration
The following sections include the configuration for the primary FWSM:
•
Example 6: System Configuration (Primary), page B-19
•
Example 6: Context A Configuration (Primary), page B-20
•
Example 6: Context B Configuration (Primary), page B-20
•
Example 6: Context C Configuration (Primary), page B-21
Example 6: System Configuration (Primary)
You must first enable multiple context mode using the mode multiple command. Then enter the
activation key to allow more than two contexts using the activation-key command. The mode and the
activation key are not stored in the configuration file, even though they do endure reboots. If you view
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Appendix B
Sample Configurations
Transparent Mode Examples
the configuration on the FWSM using the write terminal, show startup, or show running commands,
the mode displays after the FWSM Version (blank means single mode, “<system>” means you are in
multiple mode in the system configuration, and <context> means you are in multiple mode in a context).
firewall transparent
hostname primary
enable password farscape
password crichton
failover lan interface faillink vlan 10
failover link statelink vlan 11
failover lan unit primary
failover interface ip faillink 192.168.253.1 255.255.255.252 standby 192.168.253.2
failover interface ip statelink 192.168.253.5 255.255.255.252 standby 192.168.253.6
failover interface-policy 1
failover replication http
failover
admin-context contexta
context contexta
allocate-interface vlan200
allocate-interface vlan4
config-url disk://contexta.cfg
context contextb
allocate-interface vlan201
allocate-interface vlan5
config-url ftp://admin:[email protected]/contextb.cfg
context contextc
allocate-interface vlan202
allocate-interface vlan6
config-url ftp://admin:[email protected]/contextc.cfg
Example 6: Context A Configuration (Primary)
nameif vlan200 outside security0
nameif vlan4 inside security100
passwd secret1969
enable password h1andl0
ip address 10.0.3.1 255.255.255.0 standby 10.0.3.2
monitor-interface inside
monitor-interface outside
route outside 0 0 10.0.3.4 1
telnet 10.0.3.75 255.255.255.255 inside
access-list INTERNET extended permit ip any any
access-group INTERNET in interface inside [Allows all inside hosts to access the outside
for any IP traffic]
access-list BPDU ethertype permit bpdu
access-group BPDU in interface inside
access-group BPDU in interface outside
Example 6: Context B Configuration (Primary)
nameif vlan201 outside security0
nameif vlan5 inside security100
passwd secret1978
enable password 7samura1
ip address inside 10.0.2.1 255.255.255.0 standby 10.0.2.2
monitor-interface inside
monitor-interface outside
route outside 0 0 10.0.2.4 1
telnet 10.0.2.14 255.255.255.255 inside
access-list INTERNET extended permit ip any any
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Sample Configurations
Transparent Mode Examples
access-group INTERNET in interface inside [Allows all inside hosts to access the outside
for any IP traffic]
access-list BPDU ethertype permit bpdu
access-group BPDU in interface inside
access-group BPDU in interface outside
Example 6: Context C Configuration (Primary)
nameif vlan202 outside security0
nameif vlan6 inside security100
passwd secret0997
enable password strayd0g
ip address inside 10.0.1.1 255.255.255.0 standby 10.0.1.2
monitor-interface inside
monitor-interface outside
route outside 0 0 10.0.1.4 1
telnet 10.0.1.65 255.255.255.255 inside
access-list INTERNET extended permit ip any any
access-group INTERNET in interface inside [Allows all inside hosts to access the outside
for any IP traffic]
access-list BPDU ethertype permit bpdu
access-group BPDU in interface inside
access-group BPDU in interface outside
Example 6: Secondary FWSM System Configuration
You do not need to configure any contexts, just the following minimal configuration for the system.
You must first enable multiple context mode using the mode multiple command. Then enter the
activation key to allow more than two contexts using the activation-key command. The mode and the
activation key are not stored in the configuration file, even though they do endure reboots. If you view
the configuration on the FWSM using the write terminal, show startup, or show running commands,
the mode displays after the FWSM Version (blank means single mode, “<system>” means you are in
multiple mode in the system configuration, and <context> means you are in multiple mode in a context).
firewall
failover
failover
failover
failover
transparent
lan interface faillink vlan 10
interface ip faillink 192.168.253.1 255.255.255.252 standby 192.168.253.2
lan unit secondary
Example 6: Switch Configuration
The following lines in the Cisco IOS switch configuration on both switches relate to the FWSM. For
information about configuring redundancy for the switch, see the switch documentation.
...
firewall multiple-vlan-interfaces
firewall module 1 vlan-group 1
firewall vlan-group 1 4-6,10,11,200-202
interface vlan 200
ip address 10.0.1.3 255.255.255.0
standby 200 ip 10.0.1.4
standby 200 priority 110
standby 200 preempt
standby 200 timers 5 15
standby 200 authentication Secret
no shut
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Sample Configurations
Transparent Mode Examples
interface vlan 201
ip address 10.0.2.3 255.255.255.0
standby 200 ip 10.0.2.4
standby 200 priority 110
standby 200 preempt
standby 200 timers 5 15
standby 200 authentication Secret
no shut
interface vlan 202
ip address 10.0.3.3 255.255.255.0
standby 200 ip 10.0.3.4
standby 200 priority 110
standby 200 preempt
standby 200 timers 5 15
standby 200 authentication Secret
no shut
interface range gigabitethernet 2/1-3
channel-group 2 mode on
switchport trunk encapsulation dot1q
no shut
...
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A P P E N D I X
C
Understanding the Command-Line Interface
This appendix includes the following topics, which describe how to use the command-line interface
(CLI) on the Firewall Services Module (FWSM):
Note
•
Command Prompts, page C-1
•
Syntax Formatting, page C-2
•
Abbreviating Commands, page C-2
•
Command Line Editing, page C-3
•
Filtering Show Command Output, page C-3
•
Command Output Paging, page C-4
•
Adding Comments, page C-4
•
Text Configuration Files, page C-4
•
Command Help, page C-6
The CLI uses similar syntax and other conventions to the Cisco IOS CLI, but the FWSM operating
system is not a version of Cisco IOS software. Do not assume that a Cisco IOS CLI command works or
has the same function with the FWSM.
Command Prompts
When you are in the system configuration or in single context mode, the prompt begins with the host
name:
FWSM
When you are within a context, the prompt begins with the host name followed by the context name:
FWSM/context
The prompt changes depending on the access mode:
•
Unprivileged mode:
FWSM>
FWSM/context>
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Appendix C
Understanding the Command-Line Interface
Syntax Formatting
•
Privileged mode, accessible by entering the enable command:
FWSM#
FWSM/context#
•
Configuration mode, accessible by entering the configure terminal command:
FWSM(config)#
FWSM/context(config)#
•
Subcommand mode, accessible when you enter a command that places you in a subcommand mode,
such as class or interface:
FWSM(config-class)#
FWSM/context(config-if)#
Syntax Formatting
Command syntax descriptions use the following conventions:
Table C-1
Convention
Description
bold
Bold text indicates commands and keywords that you enter literally as shown.
italics
Italic text indicates arguments for which you supply values.
[x]
Square brackets enclose an optional element (keyword or argument).
|
A vertical line indicates a choice within an optional or required set of keywords or
arguments.
[x | y]
Square brackets enclosing keywords or arguments separated by a vertical line indicate
an optional choice.
{x | y}
Braces enclosing keywords or arguments separated by a vertical line indicate a required
choice.
[x {y | z}]
Nested sets of square brackets or braces indicate optional or required choices within
optional or required elements. Braces and a vertical line within square brackets indicate
a required choice within an optional element.
Abbreviating Commands
You can abbreviate most commands down to the fewest unique characters for a command; for example,
you can enter wr t to view the configuration instead of entering the full command write terminal, or
you can enter en to start privileged mode and con te to start configuration mode. In addition, you can
enter 0 to represent 0.0.0.0.
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Understanding the Command-Line Interface
Command Line Editing
Command Line Editing
The FWSM uses the same command-line editing conventions as Cisco IOS software. You can view all
previously entered commands with the show history command or individually with the up arrow or ^p
command. Once you have examined a previously entered command, you can move forward in the list
with the down arrow or ^n command. When you reach a command you wish to reuse, you can edit it or
press the Enter key to start it. You can also delete the word to the left of the cursor with ^w, or erase the
line with ^u.
The FWSM permits up to 512 characters in a command; additional characters are ignored.
Filtering Show Command Output
You can use the “pipe” operator (|) with any show command and include a filter option and filtering
expression. The filtering is performed by matching each output line with a regular expression, similar to
Cisco IOS software. By selecting different filter options you can include or exclude all output that
matches the expression. You can also display all output beginning with the line that matches the
expression.
The syntax for using filtering options with the show command is as follows:
show command | {include | exclude | begin | grep [-v]} regexp
In this command string, the first vertical bar (|) is the pipe operator and must be included in the
command. This operator directs the output of the show command to the filter. In the syntax diagram, the
other vertical bars (|) indicate alternative options and are not part of the command.
The include option includes all output lines that match the regular expression. The grep option without
-v has the same effect. The exclude option excludes all output lines that match the regular expression.
The grep option with -v has the same effect. The begin option shows all the output lines starting with
the line that matches the regular expression.
Replace regexp with any Cisco IOS regular expression. The regular expression is not enclosed in quotes or
double-quotes, so be careful with trailing white spaces, which will be taken as part of the regular
expression.
When creating regular expressions, you can use any letter or number that you want to match. In addition,
certain keyboard characters have special meaning when used in regular expressions. Table C-2 lists the
keyboard characters that have special meaning.
Table C-2
Using Special Characters in Regular Expressions
Character Type Character
Special Meaning
period
.
Matches any single character, including white space.
asterisk
*
Matches 0 or more sequences of the pattern.
plus sign
+
Matches 1 or more sequences of the pattern.
caret
^
Matches the beginning of the input string.
dollar sign
$
Matches the end of the input string.
underscore
_
Matches a comma (,), left brace ({), right brace (}), left parenthesis,
right parenthesis, the beginning of the input string, the end of the
input string, or a space.
brackets
[]
Designates a range of single-character patterns.
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Appendix C
Understanding the Command-Line Interface
Command Output Paging
Table C-2
Using Special Characters in Regular Expressions (continued)
Character Type Character
Special Meaning
hyphen
-
Separates the end points of a range.
parentheses
()
(Border Gateway Protocol [BGP] specific) Designates a group of
characters as the name of a confederation.
Command Output Paging
On commands such as help or?, show, show xlate, or other commands that provide long listings, you
can determine if the information displays a screen and pauses, or lets the command run to completion.
The pager command lets you choose the number of lines to display before the More prompt appears.
When paging is enabled, the following prompt appears:
<--- More --->
The More prompt uses syntax similar to the UNIX more command:
•
To view another screen, press the Space bar.
•
To view the next line, press the Enter key.
•
To return to the command line, press the q key.
Adding Comments
You can precede a line with a colon ( : ) to create a comment. However, the comment only appears in the
command history buffer and not in the configuration. Therefore, you can view the comment with the
show history command or by pressing an arrow key to retrieve a previous command, but because the
comment is not in the configuration, the write terminal command does not display it.
Text Configuration Files
This section describes how to format a text configuration file that you can download to the FWSM, and
includes the following topics:
•
How Commands Correspond with Lines in the Text File, page C-5
•
Subcommands, page C-5
•
Automatic Text Entries, page C-5
•
Commands Not Included in the Text Configuration, page C-5
•
Passwords, page C-6
•
Multiple Security Context Files, page C-6
To download the file, see the “Downloading a Text Configuration” section on page 16-6.
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Understanding the Command-Line Interface
Text Configuration Files
How Commands Correspond with Lines in the Text File
The text configuration file includes lines that correspond with the commands described in this guide and
in the Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Command
Reference.
In most cases, commands described in this guide are preceded by a CLI prompt. The prompt in the
following example is “FWSM(config)#”:
FWSM(config)# class gold
In the text configuration file you are not prompted to enter commands, so the prompt is omitted:
class gold
Subcommands
Subcommands appear indented under the main command when entered at the command line. Your text
file lines do not need to be indented, as long as the subcommands appear directly following the main
command. For example, the following unindented text is read the same as indented text:
class silver
limit all 5%
class gold
limit all 10%
Automatic Text Entries
When you download a configuration to the FWSM, the FWSM inserts some lines automatically. For
example, the FWSM inserts lines for default settings or for the time the configuration was modified. You
do not need to enter these automatic entries when you create your text file.
Line Order
For the most part, commands can be in any order in the file. However, some lines, such as access control
entries (ACEs), are processed in the order they appear, and the order can affect the function of the access
control list (ACL). Other commands might also have order requirements. For example, you must enter
the nameif command for an interface before you assign an IP address to it because many subsequent
commands use the name of the interface. Also, subcommands must directly follow the main command.
Commands Not Included in the Text Configuration
Some commands do not insert lines in the configuration. For example, a runtime command such as show
config does not have a corresponding line in the text file. Commands that you might expect to have
entries but do not are noted in this guide, such as activation key or mode multiple.
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Appendix C
Understanding the Command-Line Interface
Command Help
Passwords
The login, enable, and user passwords are automatically encrypted before they are stored in the
configuration. For example, the encrypted form of the password “letmein” might look like
jMorNbK0514fadBh. You can copy the configuration passwords to another FWSM in their encrypted
form, but you cannot unencrypt the passwords yourself.
If you enter an unencrypted password in a text file, the FWSM does not automatically encrypt them when
you copy the configuration to the FWSM. The FWSM only encrypts them when you save the
running configuration from the command line using the copy running-config startup-config or write
memory command.
Multiple Security Context Files
For multiple security contexts, the entire configuration consists of multiple parts:
•
The security context configurations
•
The system configuration, which identifies basic settings for the FWSM, including a list of contexts
•
The admin context, which provides network interfaces for the system configuration
The system configuration does not include any 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 a context that is designated as the admin context.
Each context is similar to a single context mode configuration. The system configuration differs from a
context configuration in that the system configuration includes system-only commands (such as a list of
all contexts) while other typical commands are not present (such as many interface parameters).
See Chapter 5, “Managing Security Contexts,” for more information about contexts.
Command Help
Help information is available from the command line by entering help or a question mark to list all
commands, or after a command to list command syntax; for example, arp ?.
The number of commands listed when you use the question mark or help command differs by access
mode so that unprivileged mode offers the least commands and configuration mode offers the greatest
number of commands.
In addition, you can enter any command by itself on the command line and then press Enter to view the
command syntax.
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A P P E N D I X
D
Addresses, Protocols, and Ports Reference
This appendix provides a quick reference for the following categories:
•
IP Addresses and Subnet Masks, page D-1
•
Protocols and Applications, page D-5
•
TCP and UDP Ports, page D-6
•
ICMP Types, page D-9
IP Addresses and Subnet Masks
This section describes how to use IP addresses in the Firewall Services Module (FWSM). An IP address
is a 32-bit number written in dotted decimal notation: four 8-bit fields (octets) converted from binary to
decimal numbers, separated by dots. The first part of an IP address identifies the network on which the
host resides, while the second part identifies the particular host on the given network. The network
number field is called the network prefix. All hosts on a given network share the same network prefix
but must have a unique host number. In classful IP, the class of the address determines the boundary
between the network prefix and the host number.
This section includes the following topics:
•
Classes, page D-1
•
Private Networks, page D-2
•
Subnet Masks, page D-2
Classes
IP host addresses are divided into three different address classes: Class A, Class B, and Class C. Each
class fixes the boundary between the network prefix and the host number at a different point within the
32-bit address. Class D addresses are reserved for multicast IP.
•
Class A addresses (1.xxx.xxx.xxx through 126.xxx.xxx.xxx) use only the first octet as the network
prefix.
•
Class B addresses (128.0.xxx.xxx through 191.255.xxx.xxx) use the first two octets as the network
prefix.
•
Class C addresses (192.0.0.xxx through 223.255.255.xxx) use the first three octets as the network
prefix.
Because Class A addresses have 16,777,214 host addresses, and Class B addresses 65,534 hosts, you can
use subnet masking to break these huge networks into smaller subnets.
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Appendix D
Addresses, Protocols, and Ports Reference
IP Addresses and Subnet Masks
Private Networks
If you need large numbers of addresses on your network, and they do not need to be routed on the
Internet, you can use private IP addresses that the Internet Assigned Numbers Authority (IANA)
recommends (see RFC 1918). The following address ranges are designated as private networks that
should not be advertised:
•
10.0.0.0 through 10.255.255.255
•
172.16.0.0 through 172.31.255.255
•
192.168.0.0 through 192.168.255.255
Subnet Masks
A subnet mask lets you convert a single Class A, B, or C network into multiple networks. With a subnet
mask, you can create an extended network prefix that adds bits from the host number to the network
prefix. For example, a Class C network prefix always consists of the first three octets of the IP address.
But a Class C extended network prefix uses part of the fourth octet as well.
Subnet masking is easy to understand if you use binary notation instead of dotted decimal. The bits in
the subnet mask have a one-to-one correspondence with the Internet address:
•
The bits are set to 1 if the corresponding bit in the IP address is part of the extended network prefix.
•
The bits are set to 0 if the bit is part of the host number.
Example 1: If you have the Class B address 129.10.0.0 and you want to use the entire third octet as part
of the extended network prefix instead of the host number, you must specify a subnet mask of
11111111.11111111.11111111.00000000. This subnet mask converts the Class B address into the
equivalent of a Class C address, where the host number consists of the last octet only.
Example 2: If you want to use only part of the third octet for the extended network prefix, then you must
specify a subnet mask like 11111111.11111111.11111000.00000000, which uses only 5 bits of the third
octet for the extended network prefix.
You can write a subnet mask as a dotted decimal mask or as a /bits (“slash bits”) mask. In Example 1,
for a dotted decimal mask, you convert each binary octet into a decimal number: 255.255.255.0. For a
/bits mask, you add the number of 1s: /24. In Example 2, the decimal number is 255.255.248.0 and the
/bits is /21.
You can also supernet multiple Class C networks into a larger network by using part of the third octet
for the extended network prefix. For example, 192.168.0.0/20.
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Addresses, Protocols, and Ports Reference
IP Addresses and Subnet Masks
Determining the Subnet Mask
To determine the subnet mask based on how many hosts you want, see Table D-1.
Table D-1
Hosts, Bits, and Dotted Decimal Masks
Hosts1
/Bits Mask
Dotted Decimal Mask
16,777,216
/8
255.0.0.0 Class A Network
65,536
/16
255.255.0.0 Class B Network
32,768
/17
255.255.128.0
16,384
/18
255.255.192.0
8,192
/19
255.255.224.0
4,096
/20
255.255.240.0
2,048
/21
255.255.248.0
1,024
/22
255.255.252.0
512
/23
255.255.254.0
256
/24
255.255.255.0 Class C Network
128
/25
255.255.255.128
64
/26
255.255.255.192
32
/27
255.255.255.224
16
/28
255.255.255.240
8
/29
255.255.255.248
4
/30
255.255.255.252
Do not use
/31
255.255.255.254
1
/32
255.255.255.255 Single Host Address
1. The first and last number of a subnet are reserved, except for /32, which identifies a single host.
Determining the Address to Use with the Subnet Mask
The following sections describe how to determine the network address to use with a subnet mask for a
Class C-size and a Class B-size network:
•
Class C-Size Network Address, page D-4
•
Class B-Size Network Address, page D-4
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Appendix D
Addresses, Protocols, and Ports Reference
IP Addresses and Subnet Masks
Class C-Size Network Address
For a network between 2 and 254 hosts, the fourth octet falls on a multiple of the number of host
addresses, starting with 0. For example, the 8-host subnets (/29) of 192.168.0.x are as follows:
Subnet with Mask /29 (255.255.255.248)
Address Range1
192.168.0.0
192.168.0.0 to 192.168.0.7
192.168.0.8
192.168.0.8 to 192.168.0.15
192.168.0.16
192.168.0.16 to 192.168.0.31
…
…
192.168.0.248
192.168.0.248 to 192.168.0.255
1. The first and last address of a subnet are reserved. In the first subnet example, you cannot use
192.168.0.0 or 192.168.0.7.
Class B-Size Network Address
To determine the network address to use with the subnet mask for a network with between 254 and
65,534 hosts, you need to determine the value of the third octet for each possible extended network
prefix. For example, you might want to subnet an address like 10.1.x.0, where the first two octets are
fixed because they are used in the extended network prefix, and the fourth octet is 0 because all bits are
used for the host number.
To determine the value of the third octet, follow these steps:
Step 1
Calculate how many subnets you can make from the network by dividing 65,536 (the total number of
addresses using the third and fourth octet) by the number of host addresses you want.
For example, 65,536 divided by 4096 hosts equals 16.
Therefore, there are 16 subnets of 4096 addresses each in a Class B-size network.
Step 2
Determine the multiple of the third octet value by dividing 256 (the number of values for the third octet)
by the number of subnets:
In this example, 256/16 = 16.
The third octet falls on a multiple of 16, starting with 0.
Therefore, the 16 subnets of the network 10.1 are as follows:
Subnet with Mask /20 (255.255.240.0)
Address Range1
10.1.0.0
10.1.0.0 to 10.1.15.255
10.1.16.0
10.1.16.0 to 10.1.31.255
10.1.32.0
10.1.32.0 to 10.1.47.255
…
…
10.1.240.0
10.1.240.0 to 10.1.255.255
1. The first and last address of a subnet are reserved. In the first subnet example, you cannot use
10.1.0.0 or 10.1.15.255.
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Addresses, Protocols, and Ports Reference
Protocols and Applications
Protocols and Applications
This section provides information about the protocols and applications with which you may need to work
when configuring the FWSM. It includes the following topics:
Possible literal values are ahp, eigrp, esp, gre, icmp, igmp, igrp, ip, ipinip, ipsec, nos, ospf, pcp, snp,
tcp, and udp. You can also specify any protocol by number. The esp and ah protocols only work in
conjunction with Private Link.
Note
The FWSM does not pass multicast packets. Many routing protocols use multicast packets for data
transfer. If you need to send routing protocols across the FWSM, configure the routers with the Cisco
IOS software neighbor command. We consider it inherently dangerous to send routing protocols across
the FWSM. If the routes on the unprotected interface are corrupted, the routes transmitted to the
protected side of the firewall will pollute routers there as well.
Table D-2 lists the numeric values for the protocol literals.
Table D-2
Protocol Literal Values
Literal
Value
Description
ah
51
Authentication Header for IPv6, RFC 1826
eigrp
88
Enhanced Interior Gateway Routing Protocol
esp
50
Encapsulated Security Payload for IPv6, RFC 1827
gre
47
generic routing encapsulation
icmp
1
Internet Control Message Protocol, RFC 792
igmp
2
Internet Group Management Protocol, RFC 1112
igrp
9
Interior Gateway Routing Protocol
ip
0
Internet Protocol
ipinip
4
IP-in-IP encapsulation
nos
94
Network Operating System (Novell’s NetWare)
ospf
89
Open Shortest Path First routing protocol, RFC 1247
pcp
108
Payload Compression Protocol
snp
109
Sitara Networks Protocol
tcp
6
Transmission Control Protocol, RFC 793
udp
17
User Datagram Protocol, RFC 768
Protocol numbers can be viewed online at the IANA website:
http://www.iana.org/assignments/protocol-numbers
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Appendix D
Addresses, Protocols, and Ports Reference
TCP and UDP Ports
TCP and UDP Ports
Table D-3 lists the literal values and port numbers; either can be entered in FWSM commands. See the
following caveats:
•
The FWSM uses port 1521 for SQL*Net. This is the default port used by Oracle for SQL*Net. This
value, however, does not agree with IANA port assignments.
•
The FWSM listens for RADIUS on ports 1645 and 1646. If your RADIUS server uses the standard
ports 1812 and 1813, you can configure the FWSM to listen to those ports using the aaa-server,
radius-authport, and aaa-server radius-acctport commands.
•
To assign a port for DNS access, use domain, not dns. The dns keyword translates into the port
value for dnsix.
Port numbers can be viewed online at the IANA website:
http://www.iana.org/assignments/port-numbers
Table D-3
Port Literal Values
Literal
TCP or UDP? Value
Description
aol
TCP
5190
America On-line
bgp
TCP
179
Border Gateway Protocol, RFC 1163
biff
UDP
512
Used by mail system to notify users that new mail is
received
bootpc
UDP
68
Bootstrap Protocol Client
bootps
UDP
67
Bootstrap Protocol Server
chargen
TCP
19
Character Generator
citrix-ica
TCP
1494
Citrix Independent Computing Architecture (ICA)
protocol
cmd
TCP
514
Similar to exec except that cmd has automatic
authentication
ctiqbe
TCP
2748
Computer Telephony Interface Quick Buffer
Encoding
daytime
TCP
13
Day time, RFC 867
discard
TCP, UDP
9
Discard
domain
TCP, UDP
53
DNS (Domain Name System)
dnsix
UDP
195
DNSIX Session Management Module Audit
Redirector
echo
TCP, UDP
7
Echo
exec
TCP
512
Remote process execution
finger
TCP
79
Finger
ftp
TCP
21
File Transfer Protocol (control port)
ftp-data
TCP
20
File Transfer Protocol (data port)
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Appendix D
Addresses, Protocols, and Ports Reference
TCP and UDP Ports
Table D-3
Port Literal Values (continued)
Literal
TCP or UDP? Value
Description
gopher
TCP
70
Gopher
https
TCP
443
Hyper Text Transfer Protocol (SSL)
h323
TCP
1720
H.323 call signalling
hostname
TCP
101
NIC Host Name Server
ident
TCP
113
Ident authentication service
imap4
TCP
143
Internet Message Access Protocol, version 4
irc
TCP
194
Internet Relay Chat protocol
isakmp
UDP
500
Internet Security Association and Key Management
Protocol
kerberos
TCP, UDP
750
Kerberos
klogin
TCP
543
KLOGIN
kshell
TCP
544
Korn Shell
ldap
TCP
389
Lightweight Directory Access Protocol
ldaps
TCP
636
Lightweight Directory Access Protocol (SSL)
lpd
TCP
515
Line Printer Daemon - printer spooler
login
TCP
513
Remote login
lotusnotes
TCP
1352
IBM Lotus Notes
mobile-ip
UDP
434
MobileIP-Agent
nameserver
UDP
42
Host Name Server
netbios-ns
UDP
137
NetBIOS Name Service
netbios-dgm
UDP
138
NetBIOS Datagram Service
netbios-ssn
TCP
139
NetBIOS Session Service
nntp
TCP
119
Network News Transfer Protocol
ntp
UDP
123
Network Time Protocol
pcanywhere-status
UDP
5632
pcAnywhere status
pcanywhere-data
TCP
5631
pcAnywhere data
pim-auto-rp
TCP, UDP
496
Protocol Independent Multicast, reverse path
flooding, dense mode
pop2
TCP
109
Post Office Protocol - Version 2
pop3
TCP
110
Post Office Protocol - Version 3
pptp
TCP
1723
Point-to-Point Tunneling Protocol
radius
UDP
1645
Remote Authentication Dial-In User Service
radius-acct
UDP
1646
Remote Authentication Dial-In User Service
(accounting)
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Appendix D
Addresses, Protocols, and Ports Reference
TCP and UDP Ports
Table D-3
Port Literal Values (continued)
Literal
TCP or UDP? Value
Description
rip
UDP
520
Routing Information Protocol
secureid-udp
UDP
5510
SecureID over UDP
smtp
TCP
25
Simple Mail Transport Protocol
snmp
UDP
161
Simple Network Management Protocol
snmptrap
UDP
162
Simple Network Management Protocol - Trap
sqlnet
TCP
1521
Structured Query Language Network
ssh
TCP
22
Secure Shell
sunrpc (rpc)
TCP, UDP
111
Sun Remote Procedure Call
syslog
UDP
514
System Log
tacacs
TCP, UDP
49
Terminal Access Controller Access Control System
Plus
talk
TCP, UDP
517
Talk
telnet
TCP
23
RFC 854 Telnet
tftp
UDP
69
Trivial File Transfer Protocol
time
UDP
37
Time
uucp
TCP
540
UNIX-to-UNIX Copy Program
who
UDP
513
Who
whois
TCP
43
Who Is
www
TCP
80
World Wide Web
xdmcp
UDP
177
X Display Manager Control Protocol
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Appendix D
Addresses, Protocols, and Ports Reference
ICMP Types
ICMP Types
Table D-4 lists the ICMP type numbers and names that you can enter in FWSM commands:
Table D-4
ICMP Types
ICMP Number
ICMP Name
0
echo-reply
3
unreachable
4
source-quench
5
redirect
6
alternate-address
8
echo
9
router-advertisement
10
router-solicitation
11
time-exceeded
12
parameter-problem
13
timestamp-request
14
timestamp-reply
15
information-request
16
information-reply
17
mask-request
18
mask-reply
31
conversion-error
32
mobile-redirect
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Appendix D
Addresses, Protocols, and Ports Reference
ICMP Types
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A P P E N D I X
E
Acronyms and Abbreviations
This appendix lists the acronyms and abbreviations used in this document.
For more information on acronyms used in this guide, refer to the Internetworking Terms and Acronyms
guide, which can be viewed online at the following website:
http://www.cisco.com/univercd/cc/td/doc/cisintwk/ita/index.htm
Table E-1
Acronyms and Abbreviations
Abbreviation
Description
AAA
authentication, authorization, and accounting.
ACE
access control entry.
ACK
acknowledgement notification.
ACL
access control list.
AH
Authentication Header.
ARP
Address Resolution Protocol—A low-level TCP/IP protocol that maps the
hardware address of a node (called a “MAC” address) to its IP address. Defined in
RFC 826. An example hardware address is 00:00:a6:00:01:ba. (The first three
groups specify the manufacturer, the rest identify the host’s motherboard.)
ASA
Adaptive Security Algorithm.
ASBR
Autonomous System Boundary Router.
ASCII
American Standard Code for Information Interchange.
BER
bit error rate.
BIND
Berkeley Internet Name Domain.
BGP
Border Gateway Protocol—While the Firewall Services Module (FWSM) does not
support use of this protocol, you can set the routers on either side of the FWSM to
use RIP between them and then run BGP on the rest of the network before the
routers.
BOOTP
Bootstrap Protocol—Lets diskless workstations boot over the network and is
described in RFC 951 and RFC 1542.
BPDU
bridge protocol data unit.
BSD
Berkeley Standard Distribution.
CA
certification authority.
CDP
Cisco Discovery Protocol.
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Appendix E
Table E-1
Acronyms and Abbreviations
Acronyms and Abbreviations (continued)
Abbreviation
Description
CGI
Common Gateway Interface.
chargen
Character Generation—Via TCP, a service that sends a continual stream of
characters until stopped by the client. Via UDP, the server sends a random number
of characters each time the client sends a datagram. Defined in RFC 864.
CLI
command-line interface.
conn
Connection slot in the FWSM—Refer to the xlate command page in the Catalyst
6500 Series Switch and Cisco 7600 Series Router Firewall Services Module
Command Reference for more information.
CoS
Class of Service.
CPU
Central Processing Unit.
CR
carriage return.
CTIQBE
Computer Telephony Interface Quick Buffer Encoding.
DES
Data Encryption Standard.
DHCP
Dynamic Host Configuration Protocol.
DMZ
demilitarized zone—A separate network behind the firewall that allows limited
access to outside users.
DNAT
Dynamic Network Address Translation.
DNS
Domain Name System (or Service)—Operates over UDP unless zone file access
over TCP is required.
DoS
Denial of service.
EIGRP
Enhanced Interior Gateway Routing Protocol—While the FWSM does not support
use of this protocol, you can set the routers on either side of the FWSM to use RIP
between them and then run EIGRP on the rest of the network before the routers.
EOBC
Ethernet Out-of-Band Channel.
ESP
Encapsulating Security Payload. Refer to RFC 1827 for more information.
EXEC
privileged command mode, which displays the “#” prompt.
Firewall MC
Firewall Management Center.
FTP
File Transfer Protocol.
FWSM
Firewall Services Module.
GRE
Generic Routing Encapsulation—A tunneling protocol that does not use
encryption.
H.323
A collection of protocols that allow the transmission of voice data over TCP/IP
networks.
HTTP
HyperText Transfer Protocol—The service that handles access to the World Wide
Web.
HTTPS
HTTP over SSL.
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Appendix E
Acronyms and Abbreviations
Table E-1
Acronyms and Abbreviations (continued)
Abbreviation
Description
IANA
Internet Assigned Number Authority—Assigns all port and protocol numbers for
use on the Internet. You can view port numbers at the following site:
http://www.iana.org/assignments/port-numbers
You can view protocol numbers at the following site:
http://www.iana.org/assignments/protocol-numbers
ICMP
Internet Control Message Protocol—This protocol is commonly used with the ping
command. You can view ICMP traces through the FWSM with the debug trace on
command. Refer to RFC 792 for more information.
IETF
Internet Engineering Task Force.
IGMP
Internet Group Management Protocol.
IGRP
Interior Gateway Routing Protocol.
IKE
Internet Key Exchange.
ILS
Internet Locator Service.
IOS
Internetwork Operating System.
IP
Internet Protocol.
IPinIP
IP-in-IP Encapsulation Protocol.
IPSec
IP Security Protocol efforts in the IETF (Internet Engineering Task Force).
IPX
Internetwork Packet Exchange.
IRC
Internet Relay Chat protocol—The protocol that lets users access chat rooms.
ISAKMP
Internet Security Association and Key Management Protocol.
ISC
IP Solution Center.
ISN
Initial Sequence Number.
ISP
Internet service provider.
ITU
International Telecommunication Union.
LDAP
Lightweight Directory Access Protocol.
LF
linefeed.
LSA
link-state advertisement.
MAC
Media Access Control.
MD5
Message Digest 5—An encryption standard for encrypting VPN packets. This same
encryption is used with the aaa authentication console command to encrypt Telnet
sessions to the console.
MGCP
Media Gateway Control Protocol.
MIB
Management Information Base—Used with SNMP.
MPLS
Multiprotocol Label Switching.
MSFC
Multilayer Switch Feature Card.
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Appendix E
Table E-1
Acronyms and Abbreviations
Acronyms and Abbreviations (continued)
Abbreviation
Description
MTU
maximum transmission unit—The maximum number of bytes in a packet that can
flow efficiently across the network with best response time. For Ethernet, the
default MTU is 1500 bytes, but each network can have different values, with serial
connections having the smallest values. The MTU is described in RFC 1191.
NAT
Network Address Translation.
NetBIOS
Network Basic Input Output System—An application programming interface (API)
that provides special functions for PCs in local-area networks (LANs).
NFS
Network File System.
NIC
Network Information Center.
NIS
Network Information Service.
NMS
network management station.
NNTP
Network News Transfer Protocol—News reader service.
NOS
Network Operating System.
NP
Network Processor—as in IBM NP or Intel NP.
NSSA
not so stubby area.
NTP
Network Time Protocol—Set system clocks via the network.
OSPF
Open Shortest Path First.
PAT
Port Address Translation.
PBX
private branch exchange.
PCP
Payload Compression Protocol.
PDM
PDM for FWSM.
PDU
protocol data unit.
PIM
Protocol Independent Multicast.
PIX
Private Internet Exchange.
POP
Post Office Protocol.
PPP
Point-to-Point Protocol. Provides FWSM-to-router and host-to-network
connections over synchronous and asynchronous circuits.
PPPoE
Point-to-Point Protocol over Ethernet.
PPTP
Point-to-Point Tunneling Protocol. RFC 2637 describes the PPTP protocol.
RADIUS
Remote Authentication Dial-In User Service—User authentication server specified
with the aaa-server command.
RAS
The registration, admission, and status protocol. Provided with H.323 support.
RDT
Real Data Transport.
RFC
Request For Comment—RFCs are the defacto standards of networking protocols.
RIP
Routing Information Protocol.
RPC
Remote Procedure Call.
RSA
Rivest, Shamir, and Adelman. RSA is the trade name for RSA Data Security, Inc.
RSH
Remote Shell—as in Remote Shell protocol.
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Appendix E
Acronyms and Abbreviations
Table E-1
Acronyms and Abbreviations (continued)
Abbreviation
Description
RTCP
RTP Control Protocol.
RTP
Real-Time Transport Protocol.
RTSP
Real Time Streaming Protocol.
SA
security association.
SCCP
Skinny (or Simple) Client Control Protocol is a simplified protocol used in VoIP
networks.
SDP
Session Description Protocol.
SIP
Session Initiation Protocol.
SMTP
Simple Mail Transfer Protocol—Mail service. The fixup protocol smtp command
enables the Mail Guard feature. The Mail Guard feature is compliant with both the
RFC 1651 EHLO and RFC 821 section 4.5.1 commands.
SNMP
Simple Network Management Protocol—Set attributes with the snmp-server
command.
SNP
Sitara Networks Protocol.
SPC
Shared Profile Component.
SPF
shortest path first.
SPI
Security Parameter Index—A number which, together with a destination IP address
and security protocol, uniquely identifies a particular security association.
SQL*Net
SQL*Net is a protocol Oracle uses to communicate between client and server
processes. (SQL stands for Structured Query Language.)
SSH
Secure Shell.
STDERR
standard error file descriptor.
SVI
switched virtual interface.
SYN
TCP synchronization, used as part of three-way handshake to establish a TCP
session.
TACACS+
Terminal Access Controller Access Control System Plus.
TCP
Transmission Control Protocol. Refer to RFC 793 for more information.
TFTP
Trivial File Transfer Protocol.
TNSFrame
Transparent Network Substrate Frame.
TPKT
Transport Packet.
Triple DES
Triple Data Encryption Standard. Also known as 3DES.
uauth
User authentication.
UDP
User Datagram Protocol.
URL
Universal Resource Locator.
UUIE
user-user information element.
VLAN
virtual LAN.
VoIP
Voice over IP.
VPN
Virtual Private Network.
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Appendix E
Table E-1
Acronyms and Abbreviations
Acronyms and Abbreviations (continued)
Abbreviation
Description
WAN
wide-area network.
WINS
Windows Internet Naming Service.
WWW
World Wide Web.
XDMCP
X Display Manager Control Protocol.
xlate
Translation session.
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I N D EX
logging
Symbols
10-26
maximum
/bits subnet masks
D-3
order
10-7
10-6
ACL memory partitions
5-17
ACLs
A
comments
AAA
accounting
12-27
authentication
CLI
inbound
network access
12-4
12-1
10-6
10-10
12-2
10-25
manual commit
10-24
maximum rules
10-7
NAT addresses
10-7
network access
10-13
10-6
OSPF, route map
12-4
abbreviating commands
abbreviations
10-18 to 10-24
order of ACEs
12-6
E-1
access control entries
See ACEs
access control lists
C-2
outbound
12-27
10-4
A-5
remarks
10-25
standard
10-17
acronyms
See ACLs
E-1
activation key
5-10
Active Directory
ACEs
10-7
10-17
10-10
policy NAT
pools
10-7
10-7
object groups
adding
expanded
10-7
10-26
memory
A-5
server
accounting
10-16
IP address guidelines
logging
17-9
local database support
maximum rules
12-25
12-23
clearing settings
12-25
inserting lines
12-10
downloadable ACLs
types
10-6
guidelines
12-20
authorization
performance
compilation
expanded
network access
overview
10-6
EtherType
12-8
command
commitment
downloadable
12-8
enable
10-25
13-11
active state, failover
15-2
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IN-1
Index
adaptive security algorithm
address range, subnets
bandwidth
1-5
limiting
D-4
admin context
maximum
changing
5-22
banners
overview
5-1
BGP
alternate address, ICMP message
Apple QuickTime
from the switch
ARP inspection
D-3
17-9
boot partitions
17-8
2-13
2-13
BPDUs
ACL, EtherType
7-4
10-17
forwarding on the switch
7-3
bridge entry timeout
7-4
ARP spoofing
7-2
See MAC address table
15-14
Broadcast Ping test
1-5
attacks, protection from
audience profile
2-12
bridge table
7-3
ARP test, failover
ASA
10-3
from the module
application partition passwords, clearing
static entry
6-5
booting
13-15
See inspection engines
overview
A-1
bits subnet masks
D-9
application inspection
enabling
5-12
1-6
xvii
15-14
buffering URL replies
14-3
bypassing the firewall
2-7
authentication
CLI
12-8
enable
FTP
C
12-8
12-21
HTTP
caching URLs
12-21
HTTPS
capturing packets
12-22
network access
overview
Telnet
12-20
See switch
12-2
Catalyst OS versions
CEF
12-2
web clients
12-22
5-22
See switch
12-10
network access
overview
A-1
Cisco 7600
12-10
command
1-2
changing between contexts
authorization
CLI
17-10
Catalyst 6500
12-21
timeout
14-4
12-23
12-2
Cisco CallManager
13-18
Cisco Firewall MC
1-4
Cisco IOS versions
1-2
Cisco IP/TV
13-15
Cisco IP Phones
inspection engine
B
with DHCP
backing up configuration
16-5
Cisco PDM
13-18
8-20
1-4
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Index
Cisco VPN Client
text file
11-7
Class A, B, and C addresses
D-1
classes
URL for a context
viewing
See resource management
classifier
prompt
adding comments
C-2
12-8
authorization
12-10
connection limits
port
6-10
12-8
3-1
contexts
C-3
command output paging
C-4
See security contexts
control plane path
C-4
conventions
C-6
1-5
xix
conversion error, ICMP message
C-4
privilege levels
crash dump
12-11
syntax formatting
local user database
TACACS+
17-11
D
12-10
12-13
data flow
command-line interface
routed firewall
See CLI
4-3
transparent firewall
command privilege levels
command prompts
C-1
comments
10-25
12-11
debug messages
default class
5-13
default route
8-2
denial of service attacks, protection
C-4
deny flows, logging
Compact Flash
2-13
DHCP
configuration
clearing
relay
16-5
3-4
comments
context files
5-2
downloading
16-5
failover
B-1
15-10
minimum
xxiii
1-6
10-28
8-21
server
Cisco IP Phones
C-4
examples
4-12
17-10
configuration
backing up
D-9
C-2
command authorization
ACLs
C-2
authentication
command line editing
displaying
3-2
console
C-4
authentication
paging
3-3
accessing
5-2
abbreviating commands
5-20
configuration mode
CLI
help
3-4
configuring
overview
8-20
8-19
8-19
transparent firewall
DMZ, definition
10-3
1-1
DNS
inspection engine
13-6
saving
3-3
NAT effect on
switch
2-1
protection from attacks
9-13
1-6
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Index
DNS Guard
actions
1-6
domain name
15-12
active state
6-5
dotted decimal subnet masks
downloadable ACLs
D-3
15-2
bandwidth
2-12, 15-5
configuration file
12-25
Flash memory
dynamic NAT
replication
See NAT
15-11
15-10
running memory
15-11
terminal messages
E
configuring
echo reply, ICMP message
editing command lines
EIGRP
D-9
contexts
15-2
disabling
10-3
routed firewall
display
9-24
transparent firewall
15-23
examples
FAQs
3-2
authentication
forcing
12-8
changing
15-27
15-24
15-23
inter-chassis
6-2
default
15-2
15-4
interface monitoring
6-2
interface policy
established command
maximum rules
EtherChannel
6-7
15-14
intra-chassis
15-4
IP addresses
15-2
link communications
backplane
load-balancing
overview
2-11
MAC addresses
monitoring
2-12, 15-5
network tests
ACL
primary unit
10-16
assigned numbers
10-13
15-13
15-13
15-14
15-10
secondary unit
standby state
B-1
extended ACL
10-17
15-10
15-2
stateful failover
overview
15-2
state information
failover
15-3
15-10
module health
2-11
EtherType
F
15-14
15-16
interface tests
A-5
security level requirements
examples
2-12, 15-5
gratuitous ARPs
password
15-12
15-19
EtherChannel
6-11
enable
failover
15-24
disabling configuration synchronization
embryonic limit
accessing
15-15
debugging
C-3
15-11
state link
15-3
statistics
15-21
switch configuration
15-3
2-11
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system messages
testing
inspection engine
15-24
15-22
threshold
15-16
transparent firewall
triggers
trunk
G
15-9
15-12
global addresses
2-12, 15-4
verifying
VLANs
recommendations
15-19
specifying
15-3
fast path
1-5
features
1-3
caching URLs
14-3
H.225, connection status
14-4
inspection engine
14-5
14-6
long URL maximum
maximum rules
14-4
13-8
version
13-7
13-7
C-6
6-4
hosts, subnet masks for
14-1
show command output
6-6
HSRP
D-3
4-9
HTTP
C-3
authentication
14-6
Firewall MC
13-18
host name
14-1
security level requirements
statistics
Skinny
help, command line
A-5
servers supported
12-8
concurrent connections
1-4
filtering
firewall mode, setting
4-16
13-10
long URL maximum
See inspection engines.
maximum rules
14-4
A-5
HTTPS
overview
2-13
filtering
partitions
2-13
management connection
size
A-1
Flood Defender
1-7
RSA key
11-4
A-3
11-4
1-6
Frag Guard
1-6
fragment size
I
1-6
FTP
ICMP
authentication
filtering
14-6
maximum connections
Flood Guard
11-4
14-5
inspection engine
fixups
Flash memory
6-2
H.323
14-6
overview
15-2
H
14-2
buffering replies
HTTPS
9-25
guest user, maintenance partition
adding a server
HTTP
9-12
gratuitous ARPs, failover
filtering
FTP
13-6
12-21
ACL
10-15
14-6
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IN-5
Index
denied access
standards
1-6
error inspection engine
inspection engine
maximum rules
object group
TFTP
11-10
13-22
module verification
17-4
enabled status
10-10
information request, ICMP message
inside, definition
D-9
D-9
failover monitoring
failover policy
maximum
naming
13-4
1-8
13-7
overview
HTTP
13-10
setting
ICMP
13-10
shared
ICMP error
6-6
6-8
5-5
standby address
13-11
15-17
turning off and on
13-11
IOS versions
13-11
limitations
classes
13-12
13-14
overview
13-1
RealAudio
1-2
D-1
configuring
13-2
8-2
management, transparent firewall
13-14
OraServ
overlapping between contexts
private
standby
13-14
13-15
SCCP
13-18
security level requirements
D-4
11-8
IPSec
6-6
basic settings
11-5
11-7
Skinny
13-18
management access
SMTP
13-19
transforms
SQL*Net
13-20
5-3
15-17
VPN client
client
13-16
8-2
D-2
subnet mask
13-15
RTSP
6-10
IP addresses
13-2
NAT and PAT support
SIP
9-25
6-8
H.323
RSH
15-16
security level
13-6
NetBIOS
15-14
A-2
overview
13-6
MGCP
6-7
global addresses
1-1
inspection engines
configuring
16-2
interfaces
13-11
information reply, ICMP message
LDAP
16-3
software to current partition
inbound ACLs
ILS
2-2
software to any partition
D-9
ILS inspection engine
FTP
13-21
installation
11-5
DNS
13-21
XDMCP
10-21
type numbers
9-6
Sun RPC
A-5
testing connectivity
IKE
static PAT
13-11
13-10
management access
13-2
11-5
11-6
IP spoofing, protection from
1-7
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Index
IPX
2-7
M
ISAKMP
11-5
MAC addresses, failover
15-10
MAC address table
L
entry timeout
MAC learning, disabling
Layer 2 firewall
overview
See transparent firewall
static entry
See MAC address table
LDAP inspection engine
Mail Guard
level
12-6
command authorization
12-9
12-4
lockout, recovering
12-19
installing application software
12-10
changing
6-2
clearing
17-10
default
6-2
root user
6-2
software installation
ACLs
system messages
17-1
management support
manual commit
12-21
SSH
maximum connections
viewing the user
login banners
12-18
6-5
login command
login password
default
D-9
mask request, ICMP message
3-2
changing
5-20
mask reply, ICMP message
3-2
3-2
Telnet
7-3
10-24
mapped interface name
12-9
6-2
6-2
12-9
8-2
1-4
man-in-the-middle attack
login
session
12-8
management IP address, transparent firewall
10-26
local user
16-3
16-5
management access authentication
logging
FTP
2-11
6-2
password
local user database
support
7-2
1-6, 13-19
guest user
15-14
load-balancing, backplane EtherChannel
logging in
7-2
maintenance partition
See security level
link up/down test
5-15
MAC learning, disabling
13-11
7-2
4-12
resource management
Layer 2 forwarding table
adding a user
7-2
D-9
9-24
memory
ACLs
10-7
Flash
A-1
RAM
A-1
rules
10-7
message-of-the-day banner
MGCP inspection engine
MIBs
6-5
13-12
17-2
Microsoft Exchange
13-19
minimum configuration
xxiii
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Index
mobile redirection, ICMP message
mode
D-9
examples
9-32
exemption from NAT
context
5-11
configuration
firewall
4-16
overview
monitoring
configuration
15-13
overview
8-16
resource management
security contexts
SNMP
TDP
9-7
maximum connections
5-24
NAT ID
outside NAT
overview
10-16
9-10
9-33
9-1, 9-2
PAT
10-16
configuring
MSFC
9-23
definition
1-2
implementation
overview
1-10
overview
SVIs
9-24
9-12
overlapping addresses
10-16
13-2
9-17
order of statements
C-4
MPLS
router-id
9-29
inspection engine support
5-26
17-2
More prompt
LDP
9-7
identity NAT
failover
OSPF
9-31
9-17
9-4
policy NAT
2-7
multicast traffic
maximum rules
4-9
Multilayer Switch Feature Card
overview
See MSFC
9-8
port redirection
multiple mode, enabling
multiple SVIs
A-5
9-34
same security level
5-11
9-11
security level requirements
2-6
6-6
static NAT
configuring
N
overview
N2H2 Sentian filtering server
naming an interface
14-1
configuring
6-8
overview
configuration
9-29
types
15-14
Network Address Translation
9-23
9-17
See NAT
network processors
9-3
embryonic limit
13-14
13-11
Network Activity test
dynamic NAT
implementation
4-11
9-3
NetMeeting
9-13
overview
9-5
NetBIOS inspection engine
9-7
configuring
9-27
transparent firewall
bypassing NAT
DNS
9-5
static PAT
NAT
overview
9-26
9-24
NPs
1-5
1-5
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IN-8
OL-6392-01
Index
route summarization
O
stub area
object groups
8-12
summary route cost
adding
outbound ACLs
ICMP
10-21
8-13
8-12
10-10
outside, definition
1-1
network
10-20
outside NAT
protocol
10-19
oversubscribing resources
service
5-12
10-20
displaying
expanded
nesting
9-10
10-24
P
10-7
10-22
packet capture
17-10
overview
10-18
packet classifier
removing
10-24
packet flow
operating system
1-9
5-2
routed firewall
OraServ inspection engine
13-14
OSPF
4-3
transparent firewall
4-12
paging screen displays
C-4
ACL for route map
10-17
parameter problem, ICMP message
area authentication
8-11
partitions
area MD5 authentication
area parameters
application
8-11
authentication key
cost
8-11
boot
8-9
8-9
default route
8-14
hello interval
8-9
8-9
logging neighbor states
8-15
MD5 authentication
8-10
changing
changing
default
8-16
6-2
6-2
6-2
6-2
maintenance partition
8-5
changing
8-6
route calculation timers
8-6
17-10
login
8-4
redistributing routes
17-9
enable
default
8-16
8-12
route map
2-13
passwords
maintenance
8-5
processes
8-16
application
link-state advertisement
packet pacing
2-13
clearing
interface parameters
monitoring
2-13
network configuration
8-5
overview
2-13
maintenance
displaying update packet pacing
NSSA
2-13
Flash memory
dead interval
enabling
2-13
crash dump
8-9
D-9
default
8-15
6-2
6-2
troubleshooting
17-9
PAT
Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Configuration Guide
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IN-9
Index
command
See NAT
more
PDM
allowing connections
installation
C-4
protocol numbers and literal values
11-4
D-5
16-2
maximum connections
version
C-1
A-3
Q
1-4
ping
quick start
xxiii
See ICMP
PIX
implicit permit
R
1-8
operating system
security levels
1-9
RADIUS
6-7
adding a server
policy NAT
ACLs
CLI authentication
10-4
inspection engines
maximum rules
9-23
9-6
network access authentication
A-5
network access authorization
support
static, configuring
9-26
static PAT, configuring
RTSP
RealPlayer
9-25
11-8
A-5
prompt
D-9
See failover
reloading
D-2
context
5-24
module
17-8
remarks
privileged mode
10-25
requirements
3-2
authentication
2-13
redundancy
15-10
private networks
17-8
redirect, ICMP message
9-34
primary unit, failover
accessing
13-15
from the switch
15-16
overview
13-15
from the module
primary module, failover
setting
13-14
rebooting
addresses
port redirection, NAT
12-25
13-15
RealNetworks
8-19
context rules
12-21
12-4
inspection engine
address
VPN
12-9
RealAudio
9-28
pools
global NAT
12-25
enable command authentication
9-8
DHCP
12-8
downloadable ACLs
dynamic, configuring
overview
12-6
1-2
resetting
12-8
from the module
C-2
privilege levels, for commands
from the switch
12-11
17-8
2-13
resource management
prompts
Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Configuration Guide
IN-10
OL-6392-01
Index
assigning a context
configuring
NAT
5-13
monitoring
oversubscribing
H.323
13-19
13-18
inspection engine
5-15
13-18
secondary unit, failover
5-13
reverse route lookup
15-10
security contexts
See Unicast RPF
adding
5-19
admin context
RIP
default route updates
enabling
passive
8-18
8-18
overview
changing
5-22
overview
5-1
assigning to a resource class
8-18
changing between
8-18
root user, maintenance partition
routed firewall mode, setting
route map ACL
classifier
6-2
files
10-17
router solicitation, ICMP message
routing
5-22
5-2
D-9
D-9
5-2
URL, changing
URL, setting
5-23
5-20
IP address overlap
default route
OSPF
logging in
8-2
other protocols
RSH, inspection engine
RTSP, inspection engine
13-15
13-15
13-15
rules
manually committing
10-24
5-9
5-1
prompt
C-1
reloading
5-24
removing
5-22
resource management
VLAN allocation
10-7
pools for contexts
overview
5-11
5-19
nesting or cascading
11-3, 11-4
maximum
5-24
name guidelines
RTSP restrictions
5-20
multiple mode, enabling
8-3
RSA key
5-9
monitoring
10-3
8-18 to 8-19
static
5-3
mapped interface name
8-4 to 8-17
5-21
configuration
4-16
router advertisement, ICMP message
RIP
9-11
fragmented packets
5-12
5-12
unlimited
6-10
SCCP
5-26
resource types
6-8
maximum connections
5-14
default class
overview
enabling
5-21
5-12
5-20
security level
A-5
allowing communication between the same level
overview
S
6-6
PIX comparison
same security level communication
embryonic connections
6-10
same security
setting
6-8
6-7
6-8
6-8
Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Configuration Guide
OL-6392-01
IN-11
Index
security policy
SQL*Net inspection engine
1-8
Sentian filtering server
serial number
SSH
14-1
authentication
5-10
server
AAA
12-8
concurrent connections
login
12-6
filtering
session management path
shared VLANs
maximum rules
3-1
1-5
5-5
show command, filtering output
shutting down an interface
C-3
RSA key
11-3
username
11-4
version
Simple Network Management Protocol
10-17
standby state, failover
backing up configuration
configuration
5-10
stateful inspection
5-11
5-11
state information
restoring
5-11
state link
SIP inspection engine
15-3
15-3
7-4
static bridge entry
7-2
static NAT
11-9
See NAT
Skinny
fragmented packets
static PAT
13-19
See NAT
13-18
inspection engine
static routes
13-18
SMTP
8-3
stealth firewall
inspection engine
See transparent firewall
13-19
protection from attacks
subcommand mode prompt
1-6
SNMP
C-2
subnet masks
/bits
17-2
overview
traps
1-5
static ARP entry
13-16
13-11
site-to-site tunnel
MIBs
5-2
See failover
enabling
H.323
15-2
stateful failover
single mode
SiteServer
A-5
startup configuration
See SNMP
11-2
11-2
standard ACL
6-10
11-2
11-4
management access
14-2
sessioning from the switch
13-20
D-3
address range
17-2
D-4
dotted decimal
17-2
software installation
any partition
maintenance
number of hosts
overview
16-3
current partition
source quench, ICMP message
2-1
specifications
A-1
D-3
D-2
Sun RPC, inspection engine
16-2
supervisor engine versions
16-5
SPAN session
D-3
D-9
supervisor IOS
13-21
1-2
1-2
SVIs
configuring
2-8
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IN-12
OL-6392-01
Index
multiple
disabling
2-6
overview
routed mode
2-6
switch
adding VLANs
2-3
assigning VLANs to module
assigning VLANs to ports
BPDU forwarding
configuration
same security level
6-11
transparent firewall
6-11
security level requirements
2-2
authentication
2-12
failover compatibility with transparent firewall
maximum modules
management access
test
sessioning to the module
15-14
2-2
switched virtual interfaces
timestamp request, ICMP message
routed firewall
1-7
system configuration
data flow
4-12
embryonic limit
6-11
EtherType ACL
10-16
examples
failover
TACACS+
HSRP
12-13
12-24
15-9
4-11
4-9
MAC address timeout
7-2
MAC learning, disabling
12-4
5-29
1-7
security level requirements
TCP ports and literal values
6-6
D-5
TCP sequence number randomization
10-3
B-15
guidelines
12-6
network access authorization
overview
7-4
DHCP packets, allowing
1-2
command authorization
7-3
static entry
5-2
T
TCP intercept
7-4
overview
5-1
adding a server
4-12
ARP inspection
enabling
C-2
system requirements
D-9
transparent firewall
SYN packet attack protection
overview
D-9
4-3
transparent firewall
A-1
1-7, 5-29
network settings
D-9
traffic flow
See SVIs
syntax formatting
13-21
timestamp reply, ICMP message
2-12
verifying module installation
SYN cookies
17-4
time exceeded, ICMP message
1-2
Switch Fabric Module
11-1
TFTP inspection engine
3-1
11-1
A-5
testing configuration
2-13
system requirements
2-12
maximum rules
2-11
A-1
resetting the module
support
12-8
concurrent connections
failover configuration
6-7
Telnet
2-3
2-1
trunk for failover
9-23
7-2
management IP address
8-2
maximum connections
6-11
mode, setting
multicast traffic
NAT
4-16
4-9
4-11
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IN-13
Index
overview
interfaces
4-9
packet handling
mapped interface name
10-3
static bridge entry
maximum
7-2
TCP sequence number randomization, disabling
VLANs
VRRP
6-11
overview
shared
4-9
A-2
1-8
5-5
gateways and gatekeepers
17-2
trunk, failover
H.323
2-12, 15-4
SCCP
U
13-7
13-7
MGCP
13-12
13-18
Skinny
13-18
VPN
UDP
connection state information
ports and literal values
Unicast RPF
basic settings
1-5
client tunnel
D-5
Unicast Reverse Path Forwarding
1-7
accessing
3-2
password
6-2
11-7
management access
transforms
VRRP
C-1
unreachable, ICMP message
context configuration, setting
14-1
11-9
11-6
4-9
WAN ports
context configuration, changing
11-5
W
D-9
URL
user, logged in
11-5
site-to-site tunnel
1-7
unprivileged mode
filtering
5-20
VoIP
4-9
traps, SNMP
prompt
2-2
5-23
1-2
Websense Enterprise filtering server
14-1
5-20
X
12-18
XDMCP, inspection engine
13-22
V
virtual firewalls
See security contexts
Virtual Re-assembly
1-6
VLANs
adding to switch
2-3
allocating to a context
assigning to FWSM
5-20
2-2
assigning to switch ports
failover interface
2-3
15-3
Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Configuration Guide
IN-14
OL-6392-01
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