Cisco Router Firewall Security

• Copyright 2005
• Dimensions: 7-3/8" x 9-1/8"
• Edition: 1st

• eBook
• ISBN-10: 0-13-343316-1
• ISBN-13: 978-0-13-343316-6

Harden perimeter routers with Cisco firewall functionality and features to ensure network security

• Detect and prevent denial of service (DoS) attacks with TCP Intercept, Context-Based Access Control (CBAC), and rate-limiting techniques
• Use Network-Based Application Recognition (NBAR) to detect and filter unwanted and malicious traffic
• Use router authentication to prevent spoofing and routing attacks
• Activate basic Cisco IOS filtering features like standard, extended, timed, lock-and-key, and reflexive ACLs to block various types of security threats and attacks, such as spoofing, DoS, Trojan horses, and worms
• Use black hole routing, policy routing, and Reverse Path Forwarding (RPF) to protect against spoofing attacks
• Apply stateful filtering of traffic with CBAC, including dynamic port mapping
• Use Authentication Proxy (AP) for user authentication
• Perform address translation with NAT, PAT, load distribution, and other methods
• Implement stateful NAT (SNAT) for redundancy
• Use Intrusion Detection System (IDS) to protect against basic types of attacks
• Obtain how-to instructions on basic logging and learn to easily interpret results
• Apply IPSec to provide secure connectivity for site-to-site and remote access connections
• Read about many, many more features of the IOS firewall for mastery of router security

The Cisco IOS firewall offers you the feature-rich functionality that you've come to expect from best-of-breed firewalls: address translation, authentication, encryption, stateful filtering, failover, URL content filtering, ACLs, NBAR, and many others. Cisco Router Firewall Security teaches you how to use the Cisco IOS firewall to enhance the security of your perimeter routers and, along the way, take advantage of the flexibility and scalability that is part of the Cisco IOS Software package.

Each chapter in Cisco Router Firewall Security addresses an important component of perimeter router security. Author Richard Deal explains the advantages and disadvantages of all key security features to help you understand when they should be used and includes examples from his personal consulting experience to illustrate critical issues and security pitfalls. A detailed case study is included at the end of the book, which illustrates best practices and specific information on how to implement Cisco router security features.

Whether you are looking to learn about firewall security or seeking how-to techniques to enhance security in your Cisco routers, Cisco Router Firewall Security is your complete reference for securing the perimeter of your network.

This book is part of the Networking Technology Series from Cisco Press, which offers networking professionals valuable information for constructing efficient networks, understanding new technologies, and building successful careers.

Table of Contents

Introduction.

I. SECURITY OVERVIEW AND FIREWALLS.

1. Security Threats.

Planning for Security.

Diverse Platforms.

Security Goals.

Causes of Security Problems.

Policy Definitions.

Computer Technologies.

Equipment Configurations.

Types of Security Threats.

External and Internal Threats.

Unstructured and Structured Threats.

Categories of Threats.

Reconnaissance Attacks.

Access Attacks.

Denial of Service Attacks.

Security Solutions.

Designing a Security Solution.

The Cisco Security Wheel.

Security Checklist.

Additional Information.

Summary.

2. Introduction to Firewalls.

Firewall Overview.

Definition of a Firewall.

Firewall Protection.

Controlling Traffic and the OSI Reference Model.

OSI Reference Model Overview.

Firewalls and the OSI Reference Model.

Firewall Categories.

Packet-Filtering Firewalls.

Stateful Firewalls.

Application Gateway Firewalls.

Address-Translation Firewalls.

Host-Based Firewalls.

Hybrid Firewalls.

Firewalls and Other Services.

Firewall Design.

Design Guidelines.

DMZ.

Components.

Component Placement.

Firewall Implementation.

Firewall Administration and Management.

Cisco IOS Security.

Cisco IOS Uses.

Cisco IOS Security Features.

Cisco IOS Devices and Their Uses.

When to Use a Cisco IOS Firewall.

Summary.

II. MANAGING ACCESS TO ROUTERS.

3. Accessing a Router.

Types of Authentication.

No Password Authentication.

Static Password Authentication.

Aging Password Authentication.

One-Time Password Authentication.

Token Card Services.

Methods of User EXEC Access.

Local Access: Console and Auxiliary.

Remote Access.

Privileged EXEC Access.

Passwords.

Privilege Levels.

Other Access Items.

Encrypting Passwords.

Banners.

Example Configuration.

Summary.

4. Disabling Unnecessary Services.

Disabling Global Services.

Cisco Discovery Protocol.

TCP and UDP Small Servers.

Finger.

IdentD.

IP Source Routing.

FTP and TFTP.

HTTP.

SNMP.

Name Resolution.

BootP.

DHCP.

PAD.

Configuration Autoloading.

Disabling Interface Services.

CDP on Insecure Interfaces.

Proxy ARP.

Directed Broadcasts.

ICMP Messages.

Maintenance Operation Protocol.

VTYs.

Unused Interfaces.

Manual Configuration Example of Disabling Services on a Perimeter Router.

AutoSecure.

Securing Planes.

AutoSecure Configuration.

Summary.

5. Authentication, Authorization, and Accounting.

AAA Overview.

AAA Functions.

Enabling AAA.

Security Protocols.

Authentication.

Methods of Authentication.

Authentication Configuration.

Authentication Troubleshooting.

Authentication Example.

Authorization.

Methods of Authorization.

Authorization Configuration.

Authorization Troubleshooting.

Authorization Example.

Accounting.

Methods of Accounting.

Accounting Configuration.

Accounting Troubleshooting.

Accounting Example.

Secure Copy.

Preparation for SCP.

SCP Configuration.

SCP Troubleshooting.

SCP Example.

Summary.

III. NONSTATEFUL FILTERING TECHNOLOGIES.

6. Access List Introduction.

Access List Overview.

ACLs and Filtering.

Types of ACLs.

Processing ACLs.

Basic ACL Configuration.

Creating ACLs.

Activating ACLs.

Editing ACLs.

Wildcard Masks.

Converting a Subnet Mask to a Wildcard Mask.

Wildcard Mask Mistakes.

Summary.

7. Basic Access Lists.

Types of ACLs.

Standard ACLs.

Extended ACLs.

ACL Verification.

Fragments and Extended ACLs.

Timed ACLs.

Additional ACL Features.

ACL Remarks.

Logging Updates.

IP Accounting and ACLs.

Turbo ACLs.

Sequenced ACLs.

Protection Against Attacks.

Bogon Blocking and Spoofing.

DoS and Distributed DoS Attacks.

Simple Reconnaissance Attacks.

Distributed DoS Attacks.

Trojan Horses.

Worms.

Blocking Unnecessary Services.

An Uphill Battle.

Instant-Messenger Products.

File Sharing: Peer-to-Peer Products.

Summary.

IV. STATEFUL AND ADVANCED FILTERING TECHNOLOGIES.

8. Reflexive Access Lists.

Overview of Reflexive ACLs.

Extended Versus Reflexive ACLs.

Reflexive ACLs in Action.

Limitations of Reflexive ACLs.

Configuring Reflexive ACLs.

Interface Selection.

Configuration Commands.

Reflexive ACL Examples.

Summary.

9. Context-Based Access Control.

Cisco IOS Firewall Features.

CBAC Functions.

Filtering Traffic.

Inspecting Traffic.

Detecting Intrusions.

Generating Alerts and Audits.

Operation of CBAC.

Basic Operation.

CBAC Enhancements over RACLs.

Supported Protocols for CBAC.

RTSP Applications.

H.323 Applications.

Skinny Support.

SIP Support.

CBAC Performance.

Throughput Improvement Feature.

Connections Per Second Improvement Feature.

CPU Utilization Improvement Feature.

CBAC Limitations.

CBAC Configuration.

Step 1: Interface Selection.

Step 2: ACL Configuration.

Step 3: Global Timeouts.

Step 4: Port Application Mapping.

Step 5: Inspection Rules.

Step 6: Inspection Activation.

Step 7: Troubleshooting CBAC.

CBAC Removal.

CBAC Examples.

Summary.

10. Filtering Web and Application Traffic.

Java Applets.

Java Inspection.

Java Blocking .

Java Blocking Example.

URL Filtering.

Operation of URL Filtering.

Advantages and Limitations of URL Filtering.

URL Filtering Implementation.

URL Filtering Verification.

URL Filtering Example.

Network-Based Application Recognition.

Components of QoS.

NBAR and Classification.

NBAR Restrictions and Limitations.

Basic NBAR Configuration.

NBAR Verification.

NBAR Examples.

Summary.

V. ADDRESS TRANSLATION AND FIREWALLS.

11. Address Translation.

Address Translation Overview.

Private Addresses.

Address Translation.

How Address Translation Works.

Terms Used in Address Translation.

Performing Address Translation.

Limitations of Address Translation.

Address Translation Configuration.

Configuration of NAT.

Configuration of PAT.

Configuration of Port Address Redirection.

Dealing with Overlapping Addresses.

Configuration of Traffic Distribution.

Configuration of Translation Limits.

Verifying and Troubleshooting Address Translation.

NAT and CBAC Example.

Summary.

12. Address Translation Issues.

Embedded Addressing Information.

Problem with Embedding Addressing Information.

Supported Protocols and Applications.

Nonstandard Port Numbers.

Controlling Address Translation.

Using ACLs.

Using Route Maps: Dynamic Translations.

Using Route Maps: Static Translations.

Address Translation and Redundancy.

Static NAT Redundancy with HSRP.

Stateful Address Translation Failover.

Traffic Distribution with Server Load Balancing.

SLB Process.

SLB Advantages and Limitations.

SLB Configuration.

SLB Verification.

SLB Example.

Summary.

VI. MANAGING ACCESS THROUGH ROUTERS.

13. Lock-and-Key Access Lists.

Lock-and-Key Overview.

Lock-and-Key and Normal ACLs.

When to Use Lock-and-Key.

Lock-and-Key Benefits.

Lock-and-Key Process.

Lock-and-Key Configuration.

Configuration Steps.

Allowing Remote Administration Access.

Verification and Troubleshooting.

Lock-and-Key Example.

Summary.

14. Authentication Proxy.

Introduction to AP.

AP Features.

AP Process.

AP Usage.

Limitations of AP.

AP Configuration.

Configuring AAA on Your Router.

Configuring AAA on Your Server.

Preparing for HTTP or HTTPS.

Configuring AP Policies.

Tuning AP.

Protecting Against Access Attacks.

Verifying and Troubleshooting AP.

show Commands.

clear Commands.

debug Commands.

AP Examples.

Simple AP Example.

Complex AP Example: CBAC and NAT.

Summary.

15. Routing Protocol Protection.

Static and Black Hole Routing.

Static Routes.

Null Routes.

Policy-Based Routing.

Interior Gateway Protocol Security.

Authentication.

RIPv2.

EIGRP.

OSPF.

IS-IS.

Other Tools.

HSRP.

BGP Security.

Reverse-Path Forwarding (Unicast Traffic).

RPF Process.

RPF Usage.

RPF Limitations.

RPF Configuration.

RPF Verification.

Unicast RPF Example.

Summary.

VII. DETECTING AND PREVENTING ATTACKS.

16. Intrusion-Detection System.

IDS Introduction.

IDS Implementations.

IDS Solutions.

IDS Concerns.

IDS Signatures.

Cisco Router IDS Solution.

Signature Support.

Router IDS Process.

Memory and Performance Issues.

IDS Configuration.

Step 1: Initialization Configuration.

Step 2: Logging and PostOffice Configuration.

Step 3: Audit Rule Configuration and Activation.

IDS Verification.

IDS Example.

Summary.

17. DoS Protection.

Detecting DoS Attacks.

Common Attacks.

Symptoms of Attacks.

Examining CPU Utilization to Detect DoS Attacks.

Using ACLs to Detect DoS Attacks.

Using NetFlow to Detect DoS Attacks.

CEF Switching.

TCP Intercept.

TCP SYN Flood Attacks.

TCP Intercept Modes.

TCP Intercept Configuration and Verification.

CBAC and DoS Attacks.

Timeouts and Thresholds.

CBAC DoS Prevention Verification.

CBAC Example Configuration.

Rate Limiting.

ICMP Rate Limiting.

CAR.

NBAR.

Summary.

18. Logging Events.

Basic Logging.

Log Message Format.

Basic Logging Configuration.

Logging Destinations.

Other Logging Commands.

Logging Verification.

Logging and Error Counts.

Time and Date and the Cisco IOS.

Router Time Sources.

Manual Time and Date Configuration.

Network Time Protocol Overview.

Router Client Configuration for NTP.

Router Server Configuration for NTP.

NTP Security.

Other NTP Commands.

NTP Verification.

NTP Configuration Example.

Embedded Syslog Manager.

ESM Overview.

ESM Filter Modules.

Introduction to ESM Setup and Configuration.

Additional Logging Information.

What to Look For.

Additional Tools.

Summary.

VIII. VIRTUAL PRIVATE NETWORKS.

19. IPSec Site-to-Site Connections.

IPSec Preparation.

Basic Tasks.

External ACL.

IKE Phase 1: Management Connection.

Enabling ISAKMP/IKE.

Defining IKE Phase 1 Policies.

IKE Phase 1 Peer Authentication.

Identity Type.

Authentication with Preshared Keys.

Authentication with RSA Encrypted Nonces.

Authentication with Certificates.

IKE Phase 2: Data Connection.

Step 1: Building a Crypto ACL.

Step 2: Creating a Transform Set.

Step 3: Creating a Crypto Map.

Step 4: Activating a Crypto Map.

Step 5: Verifying a Crypto Map Configuration.

IPSec Connection Troubleshooting.

Examining SAs.

Using debug Commands.

Clearing Connections.

L2L Example.

Summary.

20. IPSec Remote-Access Connections.

Remote Access Overview.

EasyVPN Introduction.

EasyVPN IPSec Support.

EasyVPN Features.

IPSec Remote-Access Connection Process.

Step 1: The EVC Initiates an IPSec Connection.

Step 2: The EVC Sends the IKE Phase 1 Policies.

Step 3: The EVS Accepts an IKE Phase 1 Policy.

Step 4: The EVS Authenticates the User.

Step 5: The EVS Performs IKE Mode Config.

Step 6: The EVS Handles Routing with RRI.

Step 7: The IPSec Devices Build the Data Connections.

IPSec Remote-Access EVS Setup.

Configuration Process.

Task 1: Authentication Policies.

Task 2: Group Policies.

Task 3: IKE Phase 1 Policies.

Task 4: Dynamic Crypto Maps.

Task 5: Static Crypto Map.

Task 6: Remote-Access Verification.

IPSec Remote Access Example.

Summary.

IX. CASE STUDY.

21. Case Study.

Company Profile.

Corporate Office.

Branch Office.

Remote-Access Users.

Proposal.

Case Study Configuration.

Basic Configuration.

Unnecessary Services and SSH.

AAA.

Access Control Lists.

CBAC and Web Filtering.

Address Translation.

Routing.

Intrusion-Detection System.

Connection Attacks and CBAC.

Rate Limiting.

NTP and Syslog.

Site-to-Site VPN.

Remote-Access VPNs.

Summary.

Index.

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