Cisco ASA and PIX Firewall Handbook

• Copyright 2005
• Edition: 1st

• Book
• ISBN-10: 1-58705-158-3
• ISBN-13: 978-1-58705-158-6

The complete guide to the most popular Cisco PIX®, ASA, FWSM, and IOS® firewall security features

• Learn about the various firewall models, user interfaces, feature sets, and configuration methods
• Understand how a Cisco firewall inspects traffic
• Configure firewall interfaces, routing, IP addressing services, and IP multicast support
• Maintain security contexts and Flash and configuration files, manage users, and monitor firewalls with SNMP
• Authenticate, authorize, and maintain accounting records for firewall users
• Control access through the firewall by implementing transparent and routed firewall modes, address translation, traffic filtering, user authentication, content filtering, application inspection, and traffic shunning
• Increase firewall availability with firewall failover operation
• Understand how firewall load balancing works
• Generate firewall activity logs and learn how to analyze the contents of the log
• Verify firewall operation and connectivity and observe data passing through a firewall
• Control access and manage activity on the Cisco IOS firewall
• Configure a Cisco firewall to act as an IDS sensor

Every organization has data, facilities, and workflow processes that are critical to their success. As more organizations make greater use of the Internet, defending against network attacks becomes crucial for businesses. Productivity gains and returns on company investments are at risk if the network is not properly defended. Firewalls have emerged as the essential foundation component in any network security architecture.

Cisco ASA and PIX Firewall Handbook is a guide for the most commonly implemented features of the popular Cisco Systems® firewall security solutions. This is the first book to cover the revolutionary Cisco ASA and PIX® version 7 security appliances. This book will help you quickly and easily configure, integrate, and manage the entire suite of Cisco® firewall products, including Cisco ASA, PIX version 7 and 6.3, the Cisco IOS router firewall, and the Catalyst Firewall Services Module (FWSM). Organized by families of features, this book helps you get up to speed quickly and efficiently on topics such as file management, building connectivity, controlling access, firewall management, increasing availability with failover, load balancing, logging, and verifying operation. Shaded thumbtabs mark each section for quick reference and each section provides information in a concise format, with background, configuration, and example components. Each section also has a quick reference table of commands that you can use to troubleshoot or display information about the features presented. Appendixes present lists of well-known IP protocol numbers, ICMP message types, and IP port numbers that are supported in firewall configuration commands and provide a quick reference to the many logging messages that can be generated from a Cisco PIX, ASA, FWSM, or IOS firewall.

Whether you are looking for an introduction to the firewall features of the new ASA security appliance, a guide to configuring firewalls with the new Cisco PIX version 7 operating system, or a complete reference for making the most out of your Cisco ASA, PIX, IOS, and FWSM firewall deployments, Cisco ASA and PIX Firewall Handbook helps you achieve maximum protection of your network resources.

“Many books on network security and firewalls settle for a discussion focused primarily on concepts and theory. This book, however, goes well beyond these topics. It covers in tremendous detail the information every network and security administrator needs to know when configuring and managing market-leading firewall products from Cisco.”

—Jason Nolet, Sr. Director of Engineering, Security Technology Group, Cisco Systems 

This security book is part of the Cisco Press® Networking Technology Series. Security titles from Cisco Press help networking professionals secure critical data and resources, prevent and mitigate network attacks, and build end-to-end self-defending networks.

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Table of Contents

Introduction

Chapter 1           Firewall Overview

1-1: Overview of Firewall Operation

Initial Checking

Xlate Lookup

Conn Lookup

ACL Lookup

Uauth Lookup

Inspection Engine

1-2: Inspection Engines for ICMP, UDP, and TCP

ICMP Inspection

UDP Inspection

TCP Inspection

TCP Normalization

Other Firewall Operations

1-3: Hardware and Performance

1-4: Basic Security Policy Guidelines

Further Reading

Chapter 2           Configuration Fundamentals

2-1: User Interface

User Interface Modes

User Interface Features

2-2: Firewall Features and Licenses

Upgrading a License Activation Key

2-3: Initial Firewall Configuration

Chapter 3           Building Connectivity

3-1: Configuring Interfaces

Basic Interface Configuration

Configuring IPv6 on an Interface

Configuring the ARP Cache

Configuring Interface MTU and Fragmentation

Configuring an Interface Priority Queue

Firewall Topology Considerations

3-2: Configuring Routing

Using Routing Information to Prevent IP Address Spoofing

Configuring Static Routes

Configuring RIP to Exchange Routing Information

Configuring OSPF to Exchange Routing Information

3-3: DHCP Server Functions

Using the Firewall as a DHCP Server

Relaying DHCP Requests to a DHCP Server

3-4: Multicast Support

Multicast Overview

Multicast Addressing

Forwarding Multicast Traffic

IGMP: Finding Multicast Group Recipients

PIM: Building a Multicast Distribution Tree

Configuring PIM

Configuring Stub Multicast Routing (SMR)

Configuring IGMP Operation

Stub Multicast Routing Example

PIM Multicast Routing Example

Verifying IGMP Multicast Operation

Verifying PIM Multicast Routing Operation

Chapter 4           Firewall Management

4-1: Using Security Contexts to Make Virtual Firewalls

Security Context Organization

Sharing Context Interfaces

Issues with Sharing Context Interfaces

Configuration Files and Security Contexts

Guidelines for Multiple-Context Configuration

Initiating Multiple-Context Mode

Navigating Multiple Security Contexts

Configuring a New Context

Allocating Firewall Resources to Contexts

Verifying Multiple-Context Operation

4-2: Managing the Flash File System

Using the PIX6.x Flash File System

Navigating a PIX 7.x or FWSM Flash File System

Administering a PIX 7.x or FWSM Flash File System

Identifying the Operating System Image

Upgrading an Image from the Monitor Prompt

Upgrading an Image from an Administrative Session

4-3: Managing Configuration Files

Managing the Startup Configuration

Saving a Running Configuration

Importing a Configuration

4-4: Managing Administrative Sessions

Console Connection

Telnet Sessions

SSH Sessions

PDM/ASDM Sessions

User Session Banners

Monitoring Administrative Sessions

4-5: Firewall Reloads and Crashes

Reloading a Firewall

Obtaining Crash Information

4-6: Monitoring a Firewall with SNMP

Overview of Firewall SNMP Support

SNMP Configuration

Chapter 5           Managing Firewall Users

5-1: Managing Generic Users

Authenticating and Authorizing Generic Users

Accounting of Generic Users

5-2: Managing Users with a Local Database

Authenticating with Local Usernames

Authorizing Users to Access Firewall Commands

Accounting of Local User Activity

5-3: Defining AAA Servers for User Management

5-4: Configuring AAA to Manage Administrative Users

Enabling AAA User Authentication

Enabling AAA Command Authorization

Enabling AAA Command Accounting

5-5: Configuring AAA for End-User Cut-Through Proxy

Authenticating Users Passing Through

Authorizing User Activity with TACACS+ Servers

Authorizing User Activity with RADIUS Servers

Keeping Accounting Records of User Activity

AAA Cut-Through Proxy Configuration Examples

5-6: Firewall Password Recovery

Recovering a PIX or ASA Password

Recovering an FWSM Password

Chapter 6           Controlling Access Through the Firewall

6-1: Transparent Firewall Mode

Configuring a Transparent Firewall

6-2: Routed Firewall Mode and Address Translation

Defining Access Directions

Types of Address Translation

Handling Connections Through an Address Translation

Static NAT

Policy NAT

Identity NAT

NAT Exemption

Dynamic Address Translation (NAT or PAT)

Controlling Traffic

6-3: Controlling Access with Access Lists

Defining Object Groups

Configuring an Access List

Access List Examples

Monitoring Access Lists

6-4: Filtering Content

Configuring Content Filters

Content-Filtering Examples

6-5: Defining Security Policies in a Modular Policy Framework

Classifying Traffic

Defining a Policy

Default Policy Definitions

6-6: Application Inspection

Configuring Application Inspection

6-7: Shunning Traffic

Shun Example

Chapter 7           Increasing Firewall Availability with Failover

7-1: Firewall Failover Overview

How Failover Works

Firewall Failover Roles

Detecting a Firewall Failure

Failover Communication

Active-Active Failover Requirements

7-2: Configuring Firewall Failover

7-3: Firewall Failover Configuration Examples

Active-Standby Failover Example with PIX Firewalls

Active-Standby Failover Example with FWSM

Active-Active Failover Example

7-4: Managing Firewall Failover

Displaying Information About Failover

Debugging Failover Activity

Manually Intervening in Failover

7-5: Upgrading Firewalls in Failover Mode

Upgrading an Active-Standby Failover Pair

Upgrading an Active-Active Failover Pair

Chapter 8           Firewall Load Balancing

8-1: Firewall Load Balancing Overview

8-2: Firewall Load Balancing in Software

IOS FWLB Configuration Notes

IOS FWLB Configuration

IOS Firewall Load-Balancing Example

Displaying Information About IOS FWLB

8-3: Firewall Load Balancing in Hardware

FWLB in Hardware Configuration Notes

CSM FWLB Configuration

CSM Firewall Load-Balancing Example

Displaying Information About CSM FWLB

8-4: Firewall Load-Balancing Appliance

CSS FWLB Configuration

CSS Appliance Firewall Load-Balancing Example

Displaying Information About CSS FWLB

Chapter 9           Firewall Logging

9-1: Managing the Firewall Clock

Setting the Clock Manually

Setting the Clock with NTP

9-2: Generating Logging Messages

Syslog Server Suggestions

Logging Configuration

Verifying Message Logging Activity

Manually Testing Logging Message Generation

9-3: Fine-Tuning Logging Message Generation

Pruning Messages

Changing the Message Severity Level

Access List Activity Logging

9-4: Analyzing Firewall Logs

Chapter 10           Verifying Firewall Operation

10-1: Checking Firewall Vital Signs

Using the Syslog Information

Checking System Resources

Checking Stateful Inspection Resources

Checking Firewall Throughput

Checking Inspection Engine and Service Policy Activity

Checking Failover Operation

Checking Firewall Interfaces

10-2: Watching Data Pass Through a Firewall

Using Capture

Using Debug Packet

10-3: Verifying Firewall Connectivity

Step 1: Test with Ping Packets

Step 2: Check the ARP Cache

Step 3: Check the Routing Table

Step 4: Use Traceroute to Verify the Forwarding Path

Step 5: Check the Access Lists

Step 6: Verify Address Translation Operation

Step 7: Look for Active Shuns

Step 8: Check User Authentication

Step 9: See What Has Changed

Chapter 11           Cisco IOS Firewall: Controlling Access

11-1: IOS Transparent Firewall

Configuring a Transparent IOS Firewall

11-2: Configuring Network Address Translation

NAT Operation

Using Static Address Translations

Using Dynamic Address Translations

11-3: Configuring IOS Firewall Stateful Inspection

How CBAC Works

Configuring CBAC Inspection

CBAC Example

Monitoring CBAC Operation

11-4: HTTP, Java, and URL Filtering

Monitoring URL Filtering

Chapter 12           Cisco IOS Firewall: Managing Activity

12-1: Synchronizing the IOS Firewall Clock

Setting the Clock Manually

Setting the Clock with NTP

12-2: Configuring IOS Firewall Logging

Syslog Server Suggestions

Logging Configuration

IOS Firewall Logging Messages

12-3: Using Authentication Proxy to Manage User Access

Configuring Authentication Proxy

Authentication Proxy Example

Chapter 13           Intrusion Detection System (IDS) Sensors

13-1: IDS Overview

Cisco Embedded IDS Sensor Availability

IDS Alarms

13-2: IDS Embedded Sensor Configuration

Locating the Signature Definitions

Using a Signature Update with an IOS IPS Sensor

Configuring an Embedded IDS Sensor

IDS Sensor Examples

13-3: Monitoring IDS Activity

Verifying Syslog Operation

Verifying Post Office Operation

Verifying IDS Activity on a Router Sensor

Verifying IDS Activity on a Firewall Sensor

13-4: IDS Sensor Signature List

Appendix A           Well-Known Protocol and Port Numbers

A-1: IP Protocol Numbers

A-2: ICMP Message Types

A-3: IP Port Numbers

Appendix B       Security Appliance Logging Messages

B-1: Alerts–Syslog Severity Level 1 Messages

B-2: Critical–Syslog Severity Level 2 Messages

B-3: Errors–Syslog Severity Level 3 Messages

B-4: Warnings–Syslog Severity Level 4 Messages

B-5: Notifications–Syslog Severity Level 5 Messages

B-6: Informational–Syslog Severity Level 6 Messages

B-7: Debugging–Syslog Severity Level 7 Messages

Index

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