Comparing, Designing, and Deploying VPNs
暫譯: 比較、設計與部署 VPN

A practical guide for comparing, designing, and deploying IPsec, MPLS Layer 3, L2TPv3, L2TPv2, AToM, and SSL virtual private networks

• Explore the major VPN technologies and their applications, design, and configurations on the Cisco IOS® Router, Cisco® ASA 5500 Series, and the Cisco VPN 3000 Series Concentrator platforms
• Compare the various VPN protocols and technologies, learn their advantages and disadvantages, and understand their real-world applications and methods of integration
• Find out how to design and implement Secure Socket Layer (SSL) VPNs, including consideration of clientless operation, the Cisco SSL VPN Client, the Cisco Secure Desktop, file and web server access, e-mail proxies, and port forwarding
• Learn how to deploy scalable and secure IPsec and L2TP remote access VPN designs, including consideration of authentication, encryption, split-tunneling, high availability, load-balancing, and NAT transparency
• Master scalable IPsec site-to-site VPN design and implementation including configuration of security protocols and policies, multiprotocol/ multicast traffic transport, NAT/PAT traversal, quality of service (QoS), Dynamic Multipoint VPNs (DMVPNs), and public key infrastructure (PKI)

Virtual private networks (VPNs) enable organizations to connect offices or other sites over the Internet or a service provider network and allow mobile or home-based users to enjoy the same level of productivity as those who are in the same physical location as the central network. However, with so many flavors of VPNs available, companies and providers are often hard pressed to identify, design, and deploy the VPN solutions that are most appropriate for their particular network architecture and service needs.

 

Comparing, Designing, and Deploying VPNs brings together the most popular VPN technologies for convenient reference. The book examines the real-world operation, application, design, and configuration of the following site-to-site VPNs: Layer 2 Tunneling Protocol version 3 (L2TPv3)-based Layer 2 VPNs (L2VPN); Any Transport over MPLS (AToM)-based L2VPN; MPLS Layer 3-based VPNs; and IP Security (IPsec)-based VPNs. The book covers the same details for the following remote access VPNs: Layer 2 Tunneling Protocol version 2 (L2TPv2) VPNs; L2TPv3 VPNs; IPsec-based VPNs; and Secure Socket Layer (SSL) VPNs. Through the operation, application, and configuration details offered in each chapter, you’ll learn how to compare and contrast the numerous types of VPN technologies, enabling you to consider all relevant VPN deployment options and select the VPN technologies that are most appropriate for your network.

 

Comparing, Designing, and Deploying VPNs begins with an introduction of the types of VPNs available. Subsequent chapters begin with an overview of the technology, followed by an examination of deployment pros and cons that you can use to determine if the particular VPN technology is appropriate for your network. Detailed discussion of design, deployment, and configuration make up the heart of each chapter. Appendix A offers insight into two multipoint emulated LAN services that can be deployed over a MAN or WAN: Virtual Private LAN Service (VPLS) and IP-only Private LAN Service (IPLS).

 

If you are a network architect, network engineer, network administrator, an IT manager, or CIO involved in selecting, designing, deploying, and supporting VPNs, you’ll find Comparing, Designing, and Deploying VPNs to be an indispensable reference.

 

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

 

 

 

Table of Contents

Introduction

Part I        Understanding VPN Technology

Chapter 1   What Is a Virtual Private Network?

VPN Devices

VPN Technologies and Protocols

Modeling and Characterizing VPNs

Deploying Site-to-Site and Remote Access VPNs: A Comparison

Summary

Review Questions

Part II       Site-to-Site VPNs

Chapter 2   Designing and Deploying L2TPv3-Based Layer 2 VPNs

Benefits and Drawbacks of L2TPv3-Based L2VPNs

L2TPv3 Pseudowire Operation

L2TPv3 Deployment Models

L2TPv3 Message Types

The L2TPv3 Control Connection

Configuring and Verifying L2TPv3 Pseudowires

Deploying L2TPv3 Pseudowires with Dynamic Session Setup

Implementing L2TPv3 Pseudowire-Based L2VPNs Using Static Session Configuration

L2VPN Interworking with L2TPv3

Transporting IPv6 over an IPv4 Backbone Using IPv6 Protocol Demultiplexing

Provisioning Quality of Service for L2TPv3 Pseudowires

Avoiding Packet Fragmentation and Packet Drops with L2TPv3 Pseudowires

Summary

Review Questions

Chapter 3   Designing and Implementing AToM-Based Layer 2 VPNs

Benefits and Drawbacks of AToM-Based L2VPNs

AToM Pseudowire Operation

Control Channel Messages

AToM Data Channel Packet Forwarding

Deploying AToM Pseudowires

Implementing AToM Pseudowires for Ethernet Traffic Transport

Deploying AToM Pseudowires for HDLC and PPP Traffic Transport

Frame Relay Traffic Transport with AToM Pseudowires

Using AToM Pseudowires to Transport ATM Traffic

Implementing Advanced AToM Features

Deploying AToM Pseudowire QoS

Tunnel Selection for AToM Pseudowires

L2VPN Pseudowire Switching with AToM

L2VPN Interworking with AToM Pseudowires

Configuring and Verifying Local Switching

Resolving AToM Data Channel Packet Drop Issues

Summary

Review Questions

Chapter 4   Designing MPLS Layer 3 Site-to-Site VPNs

Advantages and Disadvantages of MPLS Layer 3 VPNs

MPLS Layer 3 VPNs Overview

IP Reachability in an MPLS Layer 3 VPN

User Packet Forwarding Between MPLS Layer 3 VPN Sites

A Detailed Examination of MPLS Layer 3 VPNs

Distinguishing Customer VPN Prefixes Using Route Distinguishers (RD)

Using Route Targets (RT) to Control Customer VPN Route Distribution

Deploying MPLS Layer 3 VPNs

Configuration of PE Routers

Configuration of P Routers

Provisioning Route Distribution for VPN Topologies

Preventing Routing Loops When Customer VPN Sites Are Multihomed

Implementing Internet Access for MPLS Layer 3 VPNs

Summary

Review Questions

Chapter 5   Advanced MPLS Layer 3 VPN Deployment Considerations

The Carriers’ Carrier Architecture

CSC Architecture When MPLS Is Not Enabled Within CSC Customer Sites

CSC Architecture When MPLS Is Enabled Within CSC Customer Sites

The Inter-Autonomous System/Interprovider MPLS VPN Architecture

VRF-to-VRF Connectivity at ASBRs

Advertisement of Labeled VPN-IPv4 (VPNv4) Between ASBRs Using MP-eBGP

Advertisement of Labeled VPN-IPv4 (VPNv4) Between Route Reflectors in Separate Autonomous Systems Using Multihop MP-eBGP

Supporting Multicast Transport in MPLS Layer 3 VPNs

Point-to-Point GRE Tunnels

Multicast VPNs (MVPN)

Implementing QoS for MPLS Layer 3 VPNs

MPLS DiffServ Tunneling Models

Configuring MPLS QoS on Cisco Routers

Supporting IPv6 Traffic Transport in MPLS Layer 3 VPNs Using 6VPE

6VPE Route Exchange

6VPE Data Packet Forwarding

Configuring and Verifying 6VPE

Summary

Review Questions

Chapter 6   Deploying Site-to-Site IPsec VPNs

Advantages and Disadvantages of IPsec Site-to-Site VPNs

IPsec: A Security Architecture for IP

Cryptographic Algorithms

Security Protocols: AH and ESP

Security Associations

IPsec Databases

SA and Key Management Techniques

Putting It All Together: IPsec Packet Processing

Deploying IPsec VPNs: Fundamental Considerations

Selecting and Configuring IKE Policies for Automated SA and Key Management

Selecting and Configuring IPsec Transforms

Designing and Configuring Crypto Access Lists

Pulling Everything Together with a Crypto Map

Complete IPsec VPN Gateway Configurations

Transporting Multiprotocol and Multicast Traffic over an IPsec VPN

Manual SA and Key Management

Deploying IPsec VPNs with NAT/PAT

Allowing IPsec to Traverse a Firewall

Summary

Review Questions

Chapter 7   Scaling and Optimizing IPsec VPNs

Scaling IPsec Virtual Private Networks

Reducing the Number of IPsec Tunnels Required in a VPN

Reducing IPsec VPN Configuration Complexity with TED and DMVPN

Scaling IPsec VPNs with Digital Signature Authentication

Ensuring High Availability in an IPsec VPN

High Availability with HSRP

High Availability with GRE

Designing QoS for IPsec VPNs

Using DiffServ in an IPsec VPN

Configuring QoS with the qos pre-classify Command

IPsec Anti-Replay Considerations with QoS

Other Considerations When Provisioning QoS for an IPsec VPN

MTU and Fragmentation Considerations in an IPsec VPN

IPsec Packet Overhead

Ensuring That Large IPsec Packets Are Not Fragmented or Dropped

Summary

Review Questions

Part III     Remote Access VPNs

Chapter 8   Designing and Implementing L2TPv2 and L2TPv3 Remote Access VPNs

Benefits and Drawbacks of L2TP Remote Access VPNs

Operation of L2TP Voluntary/Client-Initiated Tunnel Mode

L2TPv2 Message Formats and Message Types

L2TP/IPsec Remote Access VPN Setup (Voluntary/Client-Initiated Tunnel Mode)

Implementing L2TP Voluntary/Client-Initiated Tunnel Mode Remote Access VPNs

Configuring PSK Authentication for L2TP/IPsec Voluntary Tunnel Mode VPNs

Implementing Digital Signature (Digital Certificate) Authentication with L2TP/ IPsec Voluntary/Client-Initiated Tunnel Mode Remote Access VPNs

Verifying L2TP/IPsec Voluntary Tunnel Mode Remote Access VPNs

Configuring L2TP/IPsec Remote Access VPNs to Transit NAT Devices

Deploying L2TP Voluntary/Client-Initiated VPNs on Cisco IOS Routers

Designing and Implementing L2TP Compulsory/NAS-Initiated Tunnel Mode Remote Access VPNs

L2TP Compulsory Tunnel Mode Setup: LAC Perspective

L2TP Compulsory Tunnel Mode Setup: LNS Perspective

Configuring the LAC for Compulsory Tunnel Mode

Configuring Tunnel Definitions on a RADIUS Server

Configuring the LNS for Compulsory Tunnel Mode

Integrating L2TP Remote Access VPNs with MPLS VPNs

Summary

Review Questions

Chapter 9   Designing and Deploying IPsec Remote Access and Teleworker VPNs

Comparing IPsec Remote Access VPNs with Other Types of Remote Access VPNs

Understanding IKE in an IPsec Remote Access VPN Environment

Resolving Issues Relating to User Authentication

Resolving Issues Relating to Negotiation of Attributes Such as IP Addresses, DNS Server Addresses, and WINS Server Addresses

Deploying IPsec Remote Access VPNs Using Preshared Key and Digital Signature Authentication

Implementing IPsec Remote Access VPNs Using Preshared Key Authentication

Designing and Deploying IPsec Remote Access VPNs Using Digital Signature Authentication

Implementing IPsec Remote Access VPNs Using Hybrid Authentication

Verifying and Debugging IPsec Remote Access VPNs

Configuring NAT Transparency for IPsec Remote Access VPNs

IPsec Remote Access/Telecommuter VPNs Using Easy VPN (EZVPN)

Integrating IPsec with MPLS VPNs

High Availability: Enabling Redundancy for IPsec Remote Access VPNs

Placing IPsec Remote Access VPN Gateways in Relation to Firewalls

Considerations When Building Wireless IPsec VPNs

Allowing or Disallowing Split Tunneling for Remote Access VPN Clients

Summary

Review Questions

Chapter 10 Designing and Building SSL Remote Access VPNs (WebVPN)

Comparing SSL VPNs to Other Types of Remote Access VPNs

Understanding the Operation of SSL Remote Access VPNs

SSL Overview: TCP, the Record Layer, and the Handshake Protocol

Establishing an SSL Connection Between a Remote Access VPN User and an SSL VPN Gateway Using an RSA Handshake

Understanding the SSL RSA Handshake with Client Authentication

Resuming an SSL Session

Closing an SSL Connection

Using Clientless SSL Remote Access VPNs (WebVPN) on the Cisco VPN 3000 Concentrator

Completing Basic SSL Remote Access VPN Access Configuration Tasks on the Cisco VPN 3000 Concentrator

Configuring File and Web Server Access via SSL Remote Access VPNs

Enabling TCP Applications over Clientless SSL Remote Access VPNs

Configuring E-mail Proxy for SSL Remote Access VPN Users

Implementing Full Network Access Using the Cisco SSL VPN Client

Installing and Enabling the Cisco VPN Client Software

Understanding Remote Access Connectivity When Using the Cisco SSL VPN Client

Strengthening SSL Remote Access VPNs Security by Implementing Cisco Secure Desktop

Installing the Cisco Secure Desktop

Configuring the Cisco Secure Desktop for Windows Clients

Configuring Cache Cleaner Options for Mac and Linux Users

Enabling the Cisco Secure Desktop

Enabling SSL VPNs (WebVPN) on Cisco IOS Devices

Step 1: Configure Domain Name and Name Server Addresses

Step 2: Configure Remote AAA for Remote Access User Login Authentication

Step 3: Enroll the IOS Router with a CA and Obtain an Identity Certificate

Step 4: Enable WebVPN

Step 5: Configure Basic SSL Parameters

Step 6: Customize Login and Home Pages (Optional)

Step 7: Specify URLs

Step 8: Configure Port Forwarding

Deploying SSL VPNs (WebVPN) on the ASA 5500

Step 1: Configure the HTTP Server

Step 2: Enable WebVPN on the Outside Interface

Step 3: Configure the WebVPN User Group Policy and Attributes

Step 4: Configure Remote Access User Authentication

Step 5: Specify URL Lists

Step 6: Configure File Access, Entry, and Browsing

Step 7: Configure Port Forwarding

Step 8: Configure E-mail Proxy

Step 9: Specify an SSL Trustpoint, SSL Version, and SSL Encryption Algorithm (Optional)

Step 10: Customize Login and Home Pages (Optional)

Verifying SSL VPNs on the ASA

Summary

Review Questions

Part IV      Appendixes

Appendix A VPLS and IPLS Layer 2 VPNs

Understanding VPLS

Ensuring a Loop-Free Topology in a VPLS

Frame Forwarding over a VPLS

VPLS MAC Address Learning

Hierarchical VPLS (H-VPLS) Deployments

Understanding IPLS

Unicast and Broadcast/Multicast Pseudowires in IPLS

Unicast and Broadcast/Multicast Forwarding in IPLS

Summary: Comparing VPLS and IPLS

Appendix B Answers to Review Questions

Chapter 1

Chapter 2

Chapter 3

Chapter 4

Chapter 5

Chapter 6

Chapter 7

Chapter 8

Chapter 9

Chapter 10

Index