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Comparing, Designing, and Deploying VPNs

Book Description

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

    1. Copyright
    2. About the Author
      1. About the Technical Reviewers
    3. Acknowledgments
    4. Icons Used in This Book
    5. Command Syntax Conventions
    6. Introduction
      1. Motivation for the Book
      2. Who Should Read This Book?
      3. How This Book Is Organized
    7. I. Understanding VPN Technology
      1. 1. What Is a Virtual Private Network?
        1. VPN Devices
          1. VPN Technologies and Protocols
            1. Technologies and Protocols Used to Enable Site-to-Site VPNs
            2. Technologies and Protocols Used to Enable Remote Access VPNs
          2. Modeling and Characterizing VPNs
            1. Service Provider and Customer Provisioned VPNs
            2. Site-to-Site and Remote Access VPNs
            3. Service Provider Provisioned Site-to-Site VPNs
              1. Layer 2 VPNs
              2. Layer 3 VPNs
            4. Customer Provisioned Site-to-Site VPNs
            5. Service Provider and Customer Provisioned Remote Access VPNs
            6. Other Methods of Categorizing VPNs
              1. Overlay and Peer-to-Peer VPNs
              2. Connection-Oriented and Connectionless VPNs
              3. Trusted and Secure VPNs
              4. And Finally. . .
        2. Deploying Site-to-Site and Remote Access VPNs: A Comparison
          1. Site-to-Site VPN Deployment
          2. Remote Access VPN Deployment
        3. Summary
        4. Review Questions
    8. II. Site-to-Site VPNs
      1. 2. Designing and Deploying L2TPv3-Based Layer 2 VPNs
        1. Benefits and Drawbacks of L2TPv3-Based L2VPNs
        2. L2TPv3 Pseudowire Operation
          1. L2TPv3 Deployment Models
          2. L2TPv3 Message Types
          3. The L2TPv3 Control Connection
            1. L2TPv3 Control Connection Setup
            2. L2TPv3 Control Connection Teardown
            3. L2TPv3 Session Setup
            4. L2TPv3 Session Teardown
            5. Hello and SLI Messages
        3. Configuring and Verifying L2TPv3 Pseudowires
          1. Deploying L2TPv3 Pseudowires with Dynamic Session Setup
            1. Step 1: Configure CEF
            2. Step 2: Configure a Loopback Interface to Use as the Pseudowire Endpoint
            3. Step 3: Configure an L2TPv3 Class (Optional)
            4. Step 4: Configure a Pseudowire Class
            5. Step 5: Bind Attachment Circuits to Pseudowires
              1. Transporting Ethernet Traffic over L2TPv3 Pseudowires
                1. Ethernet Port Transport with L2TPv3 Pseudowires
                2. Ethernet VLAN Transport with L2TPv3 Pseudowires
              2. Transporting HDLC, PPP, and X.25 over L2TPv3 Pseudowires
                1. HDLC Traffic Transport over L2TPv3
                2. PPP Traffic Transport over L2TPv3
                3. X.25 Traffic Transport over L2TPv3
              3. Deploying Frame-Relay L2TPv3 Pseudowires
                1. Frame Relay Operation and Frame Formats
                2. Frame Relay Traffic Transport over L2TPv3 Using DLCI-to-DLCI Switching
                3. Frame Relay Traffic Transport over L2TPv3 Using Frame Relay Trunks
              4. Implementing ATM Pseudowires
                1. ATM Operation, Cell, PDU, and SDU Formats
                2. Operations, Administration, and Management (OAM)
                3. Transporting ATM Traffic over L2TPv3
          2. Implementing L2TPv3 Pseudowire-Based L2VPNs Using Static Session Configuration
            1. Static L2TPv3 Sessions Without a Control Connection
            2. Static L2TPv3 Sessions with a Control Connection
          3. L2VPN Interworking with L2TPv3
            1. Ethernet Mode L2VPN Interworking with L2TPv3
            2. IP Mode L2VPN Interworking with L2TPv3
              1. Configuring and Verifying IP Mode L2VPN Interworking with L2TPv3
                1. IP Mode L2VPN Interworking Between Frame Relay and Ethernet or VLAN (802.1Q) Attachment Circuits
                2. IP Mode L2VPN Interworking Between Frame Relay and PPP Attachment Circuits
                3. IP Mode L2VPN Interworking with Ethernet and VLAN (802.1Q) Attachment Circuits
            3. Resolving MTU Issues with L2VPN Interworking
            4. Routing Protocol Considerations with L2VPN Interworking
          4. Transporting IPv6 over an IPv4 Backbone Using IPv6 Protocol Demultiplexing
          5. Provisioning Quality of Service for L2TPv3 Pseudowires
            1. Configuring an Input QoS Policy on (Ingress) PE Router Attachment Circuits
              1. Using the ip tos value value and ip tos reflect Commands
              2. Configuring QoS for L2TPv3 Using L2TPv3 Tunnel Marking
                1. Step 1: Configure a Class Map
                2. Step 2: Configure a Policy Map
                3. Step 3: Apply the Policy Map to an Interface or Virtual Circuit
                4. Configuring L2TPv3 Tunnel Marking Using Policing
            2. Configuring an Output QoS Policy on (Egress) PE Router Attachment Circuits
          6. Avoiding Packet Fragmentation and Packet Drops with L2TPv3 Pseudowires
        4. Summary
        5. Review Questions
      2. 3. Designing and Implementing AToM-Based Layer 2 VPNs
        1. Benefits and Drawbacks of AToM-Based L2VPNs
        2. AToM Pseudowire Operation
          1. Control Channel Messages
            1. AToM Pseudowire Setup
            2. AToM Status Signaling
              1. Signaling Attachment Circuit Status Changes with an LDP Label Withdraw Message
              2. Signaling Attachment Circuit Status Changes with an LDP Notification Message
          2. AToM Data Channel Packet Forwarding
        3. Deploying AToM Pseudowires
          1. Implementing AToM Pseudowires for Ethernet Traffic Transport
            1. AToM Pseudowire Ethernet Port Transport
              1. AToM Pseudowire Configuration on PE Routers
              2. Configuration on P Routers
            2. AToM Pseudowire Ethernet VLAN (802.1Q) Transport
          2. Deploying AToM Pseudowires for HDLC and PPP Traffic Transport
          3. Frame Relay Traffic Transport with AToM Pseudowires
            1. Frame Relay Port Mode Traffic Transport
            2. Frame Relay DLCI-to-DLCI Switching Traffic Transport
          4. Using AToM Pseudowires to Transport ATM Traffic
            1. ATM Cell Relay
              1. ATM Port Mode Cell Relay Transport over AToM Pseudowires
              2. ATM n-to-One Cell Relay Transport over AToM Pseudowires
              3. VCC and VPC N-to-One Cell Relay Transport with Single Cell Relay
              4. VCC and VPC N-to-One Cell Relay Transport with Packed Cell Relay
              5. Deploying ATM VCC N-to-One Cell Relay
              6. Deploying ATM VPC N-to-One Cell Relay
        4. Implementing Advanced AToM Features
          1. Deploying AToM Pseudowire QoS
          2. Tunnel Selection for AToM Pseudowires
            1. Configuring PE Routers for MPLS-TE Tunnel Selection for AToM Pseudowires
            2. Configuring P Routers for MPLS-TE
            3. Tunnel Selection for AtoM Pseudowires: Final Network Topology and Advantages
            4. Verifying MPLS-TE Tunnel Selection for AToM Pseudowires
          3. L2VPN Pseudowire Switching with AToM
          4. L2VPN Interworking with AToM Pseudowires
            1. Configuring Ethernet Mode L2VPN Interworking with AToM Pseudowires
            2. Configuring IP Mode L2VPN Interworking with AToM Pseudowires
            3. Verifying L2VPN Interworking with AToM Pseudowires
          5. Configuring and Verifying Local Switching
            1. Local Switching Between the Same Types of Physical Interfaces
            2. Local Switching Between Different Interfaces Types
            3. Local Switching Between Circuits on the Same Interface
          6. Resolving AToM Data Channel Packet Drop Issues
        5. Summary
        6. Review Questions
      3. 4. Designing MPLS Layer 3 Site-to-Site VPNs
        1. Advantages and Disadvantages of MPLS Layer 3 VPNs
        2. MPLS Layer 3 VPNs Overview
          1. IP Reachability in an MPLS Layer 3 VPN
          2. User Packet Forwarding Between MPLS Layer 3 VPN Sites
        3. A Detailed Examination of MPLS Layer 3 VPNs
          1. Distinguishing Customer VPN Prefixes Using Route Distinguishers (RD)
          2. Using Route Targets (RT) to Control Customer VPN Route Distribution
        4. Deploying MPLS Layer 3 VPNs
          1. Configuration of PE Routers
            1. Step 1: Configure a Loopback Interface for Use as the PE Router’s BGP Router ID/LDP Router ID
            2. Step 2: Configure LDP
            3. Step 3: Enable MPLS on Interfaces Connected to Other PE or P Routers
            4. Step 4: Configure the Backbone Network IGP
              1. Configuring OSPF as the Backbone Network IGP
              2. Configuring IS-IS as the Backbone Network IGP
            5. Step 5: Configure MP-BGP for VPNv4 Route Exchange with Other PE Routers or Route Reflectors
            6. Step 6: Configure the Customer VRFs
            7. Step 7: Configure the Customer VRF Interfaces
            8. Step 8: Configure the Customer VRF Routing Protocols or Static Routes for Connectivity Between Customer VPN Sites
              1. Configuring RIPv2 for Connectivity Between Customer VPN Sites
              2. Configuring EIGRP for Connectivity Between Customer VPN Sites
              3. Configuring OSPF for Connectivity Between Customer VPN Sites
              4. Configuring EBGP for Connectivity Between Customer VPN Sites
              5. Configuring Static Routes for Connectivity Between Customer VPN Sites
            9. Step 9: Redistribute the PE-CE Routing Protocol / Static VRF Routes into MP-BGP
          2. Configuration of P Routers
          3. Provisioning Route Distribution for VPN Topologies
            1. Full-Mesh Topology
            2. Hub-and-Spoke Topology
            3. Extranet Topology
          4. Preventing Routing Loops When Customer VPN Sites Are Multihomed
            1. Configuring the SoO Attribute When eBGP Is Used as the PE-CE Routing Protocol
            2. Configuring the SoO Attribute When eBGP Is Not Used as the PE-CE Routing Protocol
          5. Implementing Internet Access for MPLS Layer 3 VPNs
            1. Providing Internet Access via Separate Global Interfaces on PE Routers
            2. Providing Internet Access Using Route Leaking Between VRFs and the Global Routing Table on PE Routers
            3. Providing Internet Access via a Shared Services VPN
        5. Summary
        6. Review Questions
      4. 5. Advanced MPLS Layer 3 VPN Deployment Considerations
        1. The Carriers’ Carrier Architecture
          1. CSC Architecture When MPLS Is Not Enabled Within CSC Customer Sites
            1. Route Advertisement in a CSC Architecture When MPLS Is Not Enabled Within CSC Customer Sites
              1. Advertising External Routes Between CSC Customer Sites
              2. Advertising Internal Routes Between CSC Customer Sites
            2. Packet Forwarding in a CSC Architecture When MPLS Is Not Enabled Between Routers Within CSC Customer Sites
          2. CSC Architecture When MPLS Is Enabled Within CSC Customer Sites
            1. Route Advertisement in a CSC Architecture When MPLS Is Enabled Within CSC Customer Sites
            2. Packet Forwarding in a CSC Architecture When MPLS Is Enabled Between Routers Within CSC Customer Sites
            3. Enabling Hierarchical VPNs in a CSC Architecture
        2. The Inter-Autonomous System/Interprovider MPLS VPN Architecture
          1. VRF-to-VRF Connectivity at ASBRs
            1. Route and Label Advertisement Between Autonomous Systems When Deploying Inter-Autonomous System MPLS VPNs VRF-to-VRF Connectivity at ASBRs
            2. Packet Forwarding Between Autonomous Systems When Deploying Inter-Autonomous System MPLS VPNs VRF-to-VRF Connectivity at ASBRs
          2. Advertisement of Labeled VPN-IPv4 (VPNv4) Between ASBRs Using MP-eBGP
            1. Route and Label Advertisement Between Autonomous Systems When Deploying Inter-Autonomous System MPLS VPNs Using MP-eBGP Between ASBRs
            2. Packet Forwarding Between Autonomous Systems When Deploying Inter-Autonomous System MPLS VPNs Using MP-eBGP Between ASBRs
          3. Advertisement of Labeled VPN-IPv4 (VPNv4) Between Route Reflectors in Separate Autonomous Systems Using Multihop MP-eBGP
            1. Route and Label Advertisement When Deploying Inter-Autonomous System MPLS VPNs with the Advertisement of Labeled VPN-IPv4 Between Route Reflectors in the Separate Autonomous Systems
              1. Advertisement of VPN-IPv4 Routes (and Associated VPN Labels)
              2. Advertisement of Routes to the Next Hops of VPN-IPv4 Routes (and Routes to Route Reflectors)
            2. Packet Forwarding When Deploying Inter-Autonomous System MPLS VPNs Using MP-eBGP Between Route Reflectors in Separate Autonomous Systems
        3. Supporting Multicast Transport in MPLS Layer 3 VPNs
          1. Point-to-Point GRE Tunnels
          2. Multicast VPNs (MVPN)
            1. The Multicast VRF and Multicast Domain
            2. The Default and Data MDTs
            3. PIM Adjacencies
            4. Reverse-Path Forwarding Checks in the MVPN
            5. Configuring PIM Between PE and P Routers in the Service Provider MPLS VPN Backbone Network
            6. Advantages of Deploying MVPN
            7. Configuring and Verifying MVPN
              1. Configuring MVPN
              2. Verifying PIM Adjacencies
              3. Verifying the Signaling of the Default MDT
              4. Verifying Multicast Traffic Flow
        4. Implementing QoS for MPLS Layer 3 VPNs
          1. MPLS DiffServ Tunneling Models
            1. Pipe Model/Short Pipe Model
            2. Uniform Model
          2. Configuring MPLS QoS on Cisco Routers
            1. Implementing an MPLS DiffServ Pipe Model Architecture
            2. Implementing an MPLS DiffServ Short Pipe Model Architecture
            3. Implementing an MPLS DiffServ Uniform Model Architecture
        5. Supporting IPv6 Traffic Transport in MPLS Layer 3 VPNs Using 6VPE
          1. 6VPE Route Exchange
          2. 6VPE Data Packet Forwarding
          3. Configuring and Verifying 6VPE
        6. Summary
        7. Review Questions
      5. 6. Deploying Site-to-Site IPsec VPNs
        1. Advantages and Disadvantages of IPsec Site-to-Site VPNs
        2. IPsec: A Security Architecture for IP
          1. Cryptographic Algorithms
            1. Authentication Algorithms
              1. Hash Algorithms
              2. Message Authentication Code (MAC) and Hashed Message Authentication Code (HMAC) Algorithms
            2. Encryption Algorithms
              1. Block Ciphers
              2. Stream Ciphers
            3. Public Key Cryptographic Algorithms
              1. Encryption Using Public Key Algorithms
              2. Digital Signatures
              3. Key Exchange with Diffie-Hellman
          2. Security Protocols: AH and ESP
            1. Authentication Header (AH)
            2. Encapsulating Security Payload (ESP)
            3. AH and ESP Together
          3. Security Associations
          4. IPsec Databases
          5. SA and Key Management Techniques
            1. IKEv1
              1. IKE Phase 1 Main Mode Negotiation
              2. IKE Phase 1 Aggressive Mode Negotiation
              3. IKE Phase 2 Quick Mode Negotiation
            2. IKEv2
          6. Putting It All Together: IPsec Packet Processing
            1. Outbound Processing
            2. Inbound Processing
        3. Deploying IPsec VPNs: Fundamental Considerations
          1. Selecting and Configuring IKE Policies for Automated SA and Key Management
            1. Selecting the Appropriate Method of IKE Authentication
              1. IKE Preshared Key Authentication
              2. IKE Encrypted Nonce Authentication
              3. IKE Digital Signature Authentication
                1. Step 1: Set the Time on the IPsec VPN Gateways
                2. Step 2: Configure the IPsec VPN Gateways’ Host Names and IP Domain Names
                3. Step 3: Generate RSA Keys on the IPsec VPN Gateways
                4. Step 4: Declare the CA
                5. Step 5: Authenticate the CA
                6. Step 6: Enroll the IPsec VPN Gateways with the CA
                7. Automating Enrollment with the CA
                8. Automating Re-Enrollment with the CA
            2. Selecting Cryptographic Parameters for IKE Policies
              1. Configuring an Encryption Algorithm for an IKE Policy
              2. Configuring a Diffie-Hellman Group for an IKE Policy
              3. Configuring a Hash Algorithm for an IKE Policy
              4. Configuring an Authentication Method for an IKE Policy
              5. Configuring an IKE SA Lifetime for an IKE Policy
              6. Sample IKE Policy
          2. Selecting and Configuring IPsec Transforms
            1. Selecting Security Protocols in an IPsec Transform Set
            2. Selecting Hash Algorithms in an IPsec Transform Set
            3. Selecting Encryption Algorithms for Use with ESP
            4. Selecting Compression in an IPsec Transform Set
            5. Configuring IPsec Transform Sets
          3. Designing and Configuring Crypto Access Lists
          4. Pulling Everything Together with a Crypto Map
          5. Complete IPsec VPN Gateway Configurations
          6. Transporting Multiprotocol and Multicast Traffic over an IPsec VPN
            1. Configuring GRE/IPsec Tunnels
              1. Step 1: Configure the GRE Tunnel Interfaces
              2. Step 2: Configure the Routing Protocol or Static Routes
              3. Step 3: Configure the IKE Policies
              4. Step 4: Configure the IPsec Transform Sets
              5. Step 5: Configure the Crypto Access Lists
              6. Step 6: Configure and Apply Crypto Maps
              7. Complete IPsec VPN Gateway Configurations with GRE Tunnel for Multiprotocol and Multicast Traffic Transport
            2. Configuring VTIs
          7. Manual SA and Key Management
          8. Deploying IPsec VPNs with NAT/PAT
            1. How NAT/PAT Breaks IPsec
              1. NAT/PAT Can Cause IKE Negotiation Initiated by IPsec Peers on Outside Networks to Fail
              2. NAT/PAT Can Cause Rekeying to Fail When NAT/PAT Is Based on IKE Cookies
              3. NAT/PAT Might Break IP Address IKE Identifier Verification
              4. NAT/PAT Can Cause IPsec Peers to Drop ISAKMP Traffic
              5. NAT/PAT Causes IPsec Devices to Drop All AH Traffic
              6. NAT/PAT Based on SPI Selection Might Break IPsec
              7. NAT/PAT Devices Might Not Translate ESP Packets
              8. NAT/PAT Translation Timeouts Can Cause IPsec Traffic to be Dropped
              9. NAT/PAT Can Cause TCP/UDP Header Checksum Verification to Fail When TCP/UDP Traffic Is Transported over ESP
              10. NAT/PAT Can Cause Applications with Embedded IP Addresses to Fail
              11. Unintentional NAT’ing of User Packets Can Cause These Packets Not to Be Sent over the IPsec Tunnel
            2. Getting Around Issues with NAT/PAT and IPsec Tunnels
          9. Allowing IPsec to Traverse a Firewall
        4. Summary
        5. Review Questions
      6. 7. Scaling and Optimizing IPsec VPNs
        1. Scaling IPsec Virtual Private Networks
          1. Reducing the Number of IPsec Tunnels Required in a VPN
          2. Reducing IPsec VPN Configuration Complexity with TED and DMVPN
            1. Tunnel Endpoint Discovery (TED)
            2. Dynamic Multipoint Virtual Private Network (DMVPN)
              1. How DMVPN Works
              2. Deploying a DMVPN Architecture
                1. Configuring the DMVPN Hub Site Gateway
                2. Complete Sample Hub Site Gateway DMVPN Configuration
                3. Configuring the DMVPN Spoke Site Gateways
                4. Complete Sample Spoke Site Gateway DMVPN Configuration
                5. Configuring DMVPN on Spoke Site Gateways with Dynamically Assigned IP Addresses
          3. Scaling IPsec VPNs with Digital Signature Authentication
            1. Background to PKI Deployment
              1. X.509 Certificates
              2. Certificate Revocation
                1. CRLs
                2. Online Certificate Status Protocol (OCSP)
              3. PKI Components
                1. End Entity
                2. Certificate Authority (CA)
                3. Registration Authority (RA)
                4. Certificate Repository
                5. CRL Issuer
              4. PKI Trust Models Commonly Deployed with IPsec VPNs
            2. Deploying the PKI for an IPsec VPN: Considerations
            3. Simplifying PKI Deployment with the IOS Certificate Server
              1. Determining the Cisco IOS Certificate Server Deployment Model
              2. Configuring a Cisco IOS Certificate Server
                1. Step 1: Set the Time on the Router
                2. Step 2: Generate and Export the Cisco IOS Certificate Server Key Pair (Recommended)
                3. Step 3: Configure the HTTP Server (Recommended)
                4. Step 4: Configure the Cisco IOS Certificate Server’s Database Parameters
                5. Step 5: Configure Certificate Attributes
                6. Step 6: Specify the CRL Lifetime
                7. Step 7: Enable the Cisco IOS Certificate Server
              3. Approving, Rejecting, Revoking, and Manually Requesting Certificates
                1. Approving and Rejecting Certificate Requests
                2. Revoking Certificates
                3. Manually Requesting Certificates
        2. Ensuring High Availability in an IPsec VPN
          1. High Availability with HSRP
            1. Stateless IPsec High Availability
              1. Stateless IPsec High Availability with RRI
              2. Stateless IPsec High Availability with HSRP on the Inside Interface
            2. Stateful IPsec High Availability
          2. High Availability with GRE
            1. High Availability with Point-to-Point GRE Tunnels
            2. High Availability with DMVPN
              1. High Availability with Gateways Connected over One DMVPN
              2. High Availability with Gateways Connected over Two DMVPNs
        3. Designing QoS for IPsec VPNs
          1. Using DiffServ in an IPsec VPN
          2. Configuring QoS with the qos pre-classify Command
          3. IPsec Anti-Replay Considerations with QoS
          4. Other Considerations When Provisioning QoS for an IPsec VPN
        4. MTU and Fragmentation Considerations in an IPsec VPN
          1. IPsec Packet Overhead
            1. Overhead Added by Security Protocols
            2. Overhead Added in Transport and Tunnel Modes
            3. Overhead Added by a GRE Tunnel
            4. Calculating Total Overhead
          2. Ensuring That Large IPsec Packets Are Not Fragmented or Dropped
            1. Fragmentation of IPsec and GRE/IPsec Packets
            2. Fragmentation of Plain IPsec Packets
            3. Fragmentation of GRE/IPsec Packets
            4. PMTUD and IPsec Packet Drops
              1. PMTUD with Plain IPsec Packets
              2. PMTUD with GRE/IPsec Packets
              3. User Packets Are Dropped When PMTUD Is Broken
            5. Solutions for IPsec Packet Fragmentation and Drops
              1. Solution 1: Ensuring That End Hosts Send Smaller User Packets
                1. Configuring the ip mtu Command on GRE Tunnel Interfaces
                2. Configuring the ip tcp adjust-mss Command on the GRE Tunnel or Inside Physical Interface
              2. Solution 2: Fixing PMTUD If It Is Broken
              3. Solution 3: Using Prefragmentation for IPsec Packets
              4. Solution 4: As a Very Last Resort, Allowing Fragmentation of IPsec Packets
        5. Summary
        6. Review Questions
    9. III. Remote Access VPNs
      1. 8. Designing and Implementing L2TPv2 and L2TPv3 Remote Access VPNs
        1. Benefits and Drawbacks of L2TP Remote Access VPNs
        2. Operation of L2TP Voluntary/Client-Initiated Tunnel Mode
          1. L2TPv2 Message Formats and Message Types
          2. L2TP/IPsec Remote Access VPN Setup (Voluntary/Client-Initiated Tunnel Mode)
        3. Implementing L2TP Voluntary/Client-Initiated Tunnel Mode Remote Access VPNs
          1. Configuring PSK Authentication for L2TP/IPsec Voluntary Tunnel Mode VPNs
            1. Configuring a Cisco VPN 3000 Concentrator as an L2TP/IPsec VPN Gateway for PSK Authentication
              1. Step 1: Configure an Address Pool
              2. Step 2: Configure the Base Group
              3. Step 3: Configure L2TP/IPsec Remote Access Client User Accounts
              4. Step 4: Modify IPsec Parameters such as IKE and IPsec SA Proposals (Optional)
            2. Configuring a Cisco IOS Router as an L2TP/IPsec VPN Gateway for PSK Authentication
            3. Configuring Windows L2TP/IPsec Remote Access VPN Clients for PSK Authentication
          2. Implementing Digital Signature (Digital Certificate) Authentication with L2TP/IPsec Voluntary/Client-Initiated Tunnel Mode Remote Access VPNs
            1. Configuring the L2TP/IPsec VPN Gateway for Digital Signature Authentication
              1. Specifying Digital Signature Authentication on a Cisco VPN 3000 Concentrator
                1. Step 1: Retrieve and Install the CA’s Certificate
                2. Step 2: Enroll the VPN Gateway with the CA and Obtain a Certificate
              2. Step 5: Configure a Group for L2TP/IPsec Remote Access Client Users
              3. Step 7: Modify IPsec Parameters Such as IKE and IPsec SA Proposals
              4. Implementing Digital Signature Authentication on a Cisco IOS VPN Gateway
            2. Configuring Windows L2TP/IPsec Remote Access Clients for Digital Signature (Digital Certificate) Authentication
              1. Step 1: Obtain and Install the CA’s Certificate on the L2TP/IPsec Remote Access VPN Client
              2. Step 2: Enroll and Obtain an Identity Certificate for the Remote Access VPN Client Workstation
          3. Verifying L2TP/IPsec Voluntary Tunnel Mode Remote Access VPNs
            1. Verifying L2TP/IPsec VPNs on the VPN Gateway
            2. Verifying L2TP/IPsec VPNs on Remote Access Client Workstations
          4. Configuring L2TP/IPsec Remote Access VPNs to Transit NAT Devices
            1. Configuring L2TP/IPsec Remote Access Clients to Support NAT-T
            2. Configuring the L2TP/IPsec VPN Gateway to Support NAT-T
            3. Ensuring That More Than One Windows L2TP/IPsec Remote Access Client Can Successfully Connect to a VPN Gateway from Behind the Same NAT Device (When Using NAT-T)
          5. Deploying L2TP Voluntary/Client-Initiated VPNs on Cisco IOS Routers
        4. Designing and Implementing L2TP Compulsory/NAS-Initiated Tunnel Mode Remote Access VPNs
          1. L2TP Compulsory Tunnel Mode Setup: LAC Perspective
          2. L2TP Compulsory Tunnel Mode Setup: LNS Perspective
          3. Configuring the LAC for Compulsory Tunnel Mode
          4. Configuring Tunnel Definitions on a RADIUS Server
          5. Configuring the LNS for Compulsory Tunnel Mode
        5. Integrating L2TP Remote Access VPNs with MPLS VPNs
        6. Summary
        7. Review Questions
      2. 9. Designing and Deploying IPsec Remote Access and Teleworker VPNs
        1. Comparing IPsec Remote Access VPNs with Other Types of Remote Access VPNs
        2. Understanding IKE in an IPsec Remote Access VPN Environment
          1. Resolving Issues Relating to User Authentication
            1. Extended Authentication Within IKE (Xauth)
            2. Hybrid Authentication Mode for IKE
            3. IKE Challenge/Response for Authenticated Cryptographic Keys (CRACK)
          2. Resolving Issues Relating to Negotiation of Attributes Such as IP Addresses, DNS Server Addresses, and WINS Server Addresses
        3. Deploying IPsec Remote Access VPNs Using Preshared Key and Digital Signature Authentication
          1. Implementing IPsec Remote Access VPNs Using Preshared Key Authentication
            1. Configuring an IPsec Remote Access VPN Gateway for Preshared Key Authentication
              1. Cisco VPN 3000 Concentrator as an IPsec Remote Access VPN Gateway Using Preshared Key Authentication
                1. Step 1: Specify an IP Address Pool or Other Form of IP Address Assignment
                2. Step 2: Configure a Group for IPsec Remote Access VPN Users
                3. Step 3: Configure User Accounts for Remote Access VPN Users
                4. Step 4: Modify IPsec/IKE Parameters (Optional)
              2. Cisco IOS Router as an IPsec Remote Access VPN Gateway with IKE Preshared Key Authentication
              3. Cisco ASA as an IPsec Remote Access VPN Gateway with IKE Preshared Key Authentication
            2. Configuring the Cisco VPN Client for IKE Preshared Key Authentication
          2. Designing and Deploying IPsec Remote Access VPNs Using Digital Signature Authentication
            1. Implementing Digital Signature Authentication on IPsec Remote Access VPN Gateways
              1. IKE Digital Signature Authentication on a Cisco VPN 3000 Concentrator
                1. Step 1: Obtain the CA’s Certificate Using SCEP
                2. Step 2: Enroll the VPN Gateway with the CA and Obtain an Identity Certificate Using SCEP
                3. Step 6: Modify IPsec/IKE Parameters for Digital Signature Authentication
              2. IKE Digital Signature Authentication on a Cisco IOS VPN Gateway
              3. IKE Digital Signature Authentication on a Cisco ASA VPN Gateway
            2. Deploying IKE Digital Signature Authentication on IPsec Remote Access VPN Clients
          3. Implementing IPsec Remote Access VPNs Using Hybrid Authentication
            1. Deploying Hybrid Authentication on the Cisco VPN 3000 Concentrator
            2. Configuring Hybrid Authentication on Cisco VPN Clients
          4. Verifying and Debugging IPsec Remote Access VPNs
            1. Verifying IPsec Remote Access VPNs on Cisco VPN 3000 Concentrators
            2. Verifying IPsec Remote Access VPNs on Cisco IOS VPN Gateways
            3. Verifying IPsec Remote Access VPNs on the Cisco ASA
            4. Verifying IPsec Remote Access VPNs on Cisco VPN Clients
          5. Configuring NAT Transparency for IPsec Remote Access VPNs
            1. Overcoming Issues with NAT/PAT When Using Cisco VPN 3000 Concentrators
            2. Overcoming Issues with NAT/PAT When Using Cisco IOS VPN Gateways
            3. Overcoming Issues with NAT/PAT When Using the Cisco ASA 5500
            4. Configuring NAT/PAT Transparency on Cisco VPN Clients
          6. IPsec Remote Access/Telecommuter VPNs Using Easy VPN (EZVPN)
          7. Integrating IPsec with MPLS VPNs
            1. Providing IPsec Remote Access Connectivity to MPLS VPNs
            2. Integrating IPsec Site-to-Site VPNs with MPLS VPNs
          8. High Availability: Enabling Redundancy for IPsec Remote Access VPNs
            1. Load Balancing of IPsec Remote Access VPN Connections over a Number of VPN Gateways at the Same Central Site
              1. Load Balancing on Cisco VPN 3000 Concentrators
              2. Load Balancing on Cisco ASA 5500s
            2. Failover Between a Number of VPN Gateways at the Same Central Site Using VRRP
            3. Using Backup VPN Gateways (Servers) at Geographically Dispersed VPN Gateways
          9. Placing IPsec Remote Access VPN Gateways in Relation to Firewalls
          10. Considerations When Building Wireless IPsec VPNs
          11. Allowing or Disallowing Split Tunneling for Remote Access VPN Clients
        4. Summary
        5. Review Questions
      3. 10. Designing and Building SSL Remote Access VPNs (WebVPN)
        1. Comparing SSL VPNs to Other Types of Remote Access VPNs
        2. Understanding the Operation of SSL Remote Access VPNs
          1. SSL Overview: TCP, the Record Layer, and the Handshake Protocol
          2. Establishing an SSL Connection Between a Remote Access VPN User and an SSL VPN Gateway Using an RSA Handshake
            1. SSL Connection Establishment: ClientHello Message
            2. SSL Connection Establishment: ServerHello, Certificate, and ServerHelloDone Messages
            3. SSL Connection Establishment: ClientKeyExchange, ChangeCipherSpec, and Finished Messages
            4. SSL Handshake: SSLv2, SSLv3, or TLS?
          3. Understanding the SSL RSA Handshake with Client Authentication
          4. Resuming an SSL Session
          5. Closing an SSL Connection
        3. Using Clientless SSL Remote Access VPNs (WebVPN) on the Cisco VPN 3000 Concentrator
          1. Completing Basic SSL Remote Access VPN Access Configuration Tasks on the Cisco VPN 3000 Concentrator
            1. Step 1: Enroll and Obtain a (SSL) Certificate for the VPN 3000 Concentrator from a Certificate Authority (Optional)
            2. Step 2: Enable WebVPN for Relevant User Groups
            3. Step 3: Specify Acceptable Versions of SSL and Configure Cryptographic Algorithms Associated with SSL Cipher Suites (Optional)
            4. Step 4: Enable SSL on the VPN 3000 Concentrator’s Public Interface
          2. Configuring File and Web Server Access via SSL Remote Access VPNs
            1. Step 1: Configure One or More NetBIOS Name Servers
            2. Step 2: Configure WebVPN File Servers and Shares
            3. Step 3: Enable File and URL Access for the WebVPN User Group(s)
          3. Enabling TCP Applications over Clientless SSL Remote Access VPNs
          4. Configuring E-mail Proxy for SSL Remote Access VPN Users
        4. Implementing Full Network Access Using the Cisco SSL VPN Client
          1. Installing and Enabling the Cisco VPN Client Software
          2. Understanding Remote Access Connectivity When Using the Cisco SSL VPN Client
        5. Strengthening SSL Remote Access VPNs Security by Implementing Cisco Secure Desktop
          1. Installing the Cisco Secure Desktop
          2. Configuring the Cisco Secure Desktop for Windows Clients
            1. Configuring the Windows Cache Cleaner
            2. Configuring VPN Feature Policy Settings
            3. Configuring Secure Desktop Options
          3. Configuring Cache Cleaner Options for Mac and Linux Users
          4. Enabling the Cisco Secure Desktop
        6. Enabling SSL VPNs (WebVPN) on Cisco IOS Devices
          1. Step 1: Configure Domain Name and Name Server Addresses
          2. Step 2: Configure Remote AAA for Remote Access User Login Authentication
          3. Step 3: Enroll the IOS Router with a CA and Obtain an Identity Certificate
          4. Step 4: Enable WebVPN
          5. Step 5: Configure Basic SSL Parameters
          6. Step 6: Customize Login and Home Pages (Optional)
          7. Step 7: Specify URLs
          8. Step 8: Configure Port Forwarding
        7. Deploying SSL VPNs (WebVPN) on the ASA 5500
          1. Step 1: Configure the HTTP Server
          2. Step 2: Enable WebVPN on the Outside Interface
          3. Step 3: Configure the WebVPN User Group Policy and Attributes
          4. Step 4: Configure Remote Access User Authentication
          5. Step 5: Specify URL Lists
          6. Step 6: Configure File Access, Entry, and Browsing
          7. Step 7: Configure Port Forwarding
          8. Step 8: Configure E-mail Proxy
          9. Step 9: Specify an SSL Trustpoint, SSL Version, and SSL Encryption Algorithm (Optional)
            1. Specifying an SSL Trustpoint
            2. Restricting Acceptable SSL Versions
            3. Configuring the Cryptographic Algorithms That the ASA Will Negotiate with Remote Access Clients
          10. Step 10: Customize Login and Home Pages (Optional)
          11. Verifying SSL VPNs on the ASA
        8. Summary
        9. Review Questions
    10. IV. Appendixes
      1. A. VPLS and IPLS Layer 2 VPNs
        1. Understanding VPLS
          1. Ensuring a Loop-Free Topology in a VPLS
          2. Frame Forwarding over a VPLS
          3. VPLS MAC Address Learning
          4. Hierarchical VPLS (H-VPLS) Deployments
        2. Understanding IPLS
          1. Unicast and Broadcast/Multicast Pseudowires in IPLS
          2. Unicast and Broadcast/Multicast Forwarding in IPLS
        3. Summary: Comparing VPLS and IPLS
      2. B. Answers to Review Questions
        1. Chapter 1
        2. Chapter 2
        3. Chapter 3
        4. Chapter 4
        5. Chapter 5
        6. Chapter 6
        7. Chapter 7
        8. Chapter 8
        9. Chapter 9
        10. Chapter 10