VPDN Configuration Guide, Cisco IOS Release 15M&T
Configuring Client-Initiated Dial-In VPDN Tunneling
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Configuring Client-Initiated Dial-In VPDN Tunneling

Contents

Configuring Client-Initiated Dial-In VPDN Tunneling

Client-initiated dial-in virtual private dialup networking (VPDN) tunneling deployments allow remote users to access a private network over a shared infrastructure with end-to-end protection of private data. Client-initiated VPDN tunneling does not require additional security to protect data between the client and the Internet service provider (ISP) network access server (NAS).

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Prerequisites for Client-Initiated VPDN Tunneling

  • If the client device is a PC, appropriate Virtual Private Network (VPN) software must be installed and configured. For information on installing and configuring client VPN software, refer to the instructions provided with the VPN software package.
  • The NAS should be configured to receive incoming calls from clients using ISDN, the public switched telephone network (PSTN), digital subscriber line (DSL), or cable modem.
  • The interface between the NAS and the tunnel server must be configured for PPP.
  • Before performing the tasks documented in this module, you must perform the required tasks in the Configuring AAA for VPDNs module.

Restrictions for Client-Initiated VPDN Tunneling

  • The Layer 2 Forwarding (L2F) protocol is not supported.
  • Layer 2 Tunneling Protocol (L2TP) and L2TP Version 3 (L2TPv3) protocols are supported only for tunnels initiated by a client router.
  • The Point-to-Point Tunneling Protocol (PPTP) is supported only for tunnels initiated by a client PC running appropriate VPN software.

Information About Client-Initiated VPDN Tunneling

Client-Initiated VPDN Tunneling

Client-initiated dial-in VPDN tunneling is also known as voluntary tunneling. In a client-initiated dial-in VPDN scenario, the client device initiates a Layer 2 tunnel to the tunnel server, and the NAS does not participate in tunnel negotiation or establishment. In this scenario the NAS is not a tunnel endpoint, it simply provides internet connectivity.

The client can be either of these devices:

  • A properly configured router attached to a client network using either L2TP or L2TPv3.
  • A PC that is running appropriate VPN client software using PPTP.

Client-initiated VPDN tunneling provides end-to-end security for the connection from the client to the tunnel server. Unlike NAS-initiated VPDN scenarios, no additional security is required to protect the connection between the client device and the NAS.

The figure below depicts a generic client-initiated VPDN tunneling scenario. The local device, which can be either a client PC or a client router, connects to the NAS through a medium that supports PPP. The client can initiate a VPDN tunnel to the tunnel server using either the PPTP, L2TP, or L2TPv3 protocol. The type of Layer 2 tunnel that is established is dependent on the configuration of both the client device and remote tunnel server.

Figure 1. Client-Initiated Tunneling

Client-Initiated VPDN Tunneling Using the L2TP or L2TPv3 Protocol

Client-initiated tunnels using the L2TP or L2TPv3 protocol must be initiated by a router configured as the local peer. The L2TP and L2TPv3 protocols are not supported for client-initiated tunnels from a client PC.

In the client-initiated tunneling scenario depicted in the figure below, the local peer connects to the NAS through a medium that supports PPP, such as a dialup modem, DSL, ISDN, or cable modem. The PPP interface adds Layer 2 encapsulation to Layer 3 packets, allowing them to be sent to the tunnel server over an L2TP or L2TPv3 tunnel.

The client can initiate a VPDN tunnel to the tunnel server using either the L2TP or L2TPv3 protocol. The type of Layer 2 tunnel that is established is dependent on the configuration of both the local peer and remote tunnel server. The local and remote peers must be configured to establish the same type of tunnel.

Figure 2. L2TP or L2TPv3 Client-Initiated Tunneling

Client-Initiated VPDN Tunneling Using the PPTP Protocol

Client-initiated tunnels using the PPTP protocol must be initiated by a client PC configured with appropriate VPN client software. The client must manage the software that initiates the tunnel on the PC. The PPTP protocol is not supported for client-initiated tunnels from a local peer router.

In the client-initiated tunneling scenario depicted in the figure below, the client PC connects to the NAS through a medium that supports PPP, such as a dialup modem, DSL, ISDN, or cable modem. The client can initiate a VPDN tunnel to the tunnel server using the PPTP protocol.

Figure 3. PPTP Client-Initiated Tunneling

PPTP uses an enhanced Generic Routing Encapsulation (GRE) mechanism to provide a flow- and congestion-controlled encapsulated datagram service for carrying PPP packets.

These sections contain information about PPTP features:

MPPE Encryption of PPTP Tunnels

Microsoft Point-to-Point Encryption (MPPE) can be used to encrypt PPTP VPDN tunnels. MPPE encrypts the entire session from the client to the tunnel server.

MPPE is an encryption technology developed by Microsoft to encrypt point-to-point links. These connections can be over a dialup line or over a VPDN tunnel. MPPE works is a feature of Microsoft Point-to-Point Compression (MPPC).

MPPC is a scheme used to compress PPP packets between Cisco and Microsoft client devices. The MPPC algorithm is designed to optimize bandwidth utilization in order to support multiple simultaneous connections.

MPPE is negotiated using bits in the MPPC option within the Compression Control Protocol (CCP) MPPC configuration option (CCP configuration option number 18).

MPPE uses the RC4 algorithm with either 40- or 128-bit keys. All keys are derived from the cleartext authentication password of the user. RC4 is stream cipher; therefore, the sizes of the encrypted and decrypted frames are the same size as the original frame. The Cisco implementation of MPPE is fully interoperable with that of Microsoft and uses all available options, including stateless mode (sometimes referred to as historyless mode). Stateless mode can increase throughput in lossy environments such as VPDNs, because neither side needs to send CCP Resets Requests to synchronize encryption contexts when packets are lost.

Two modes of MPPE encryption are available:

  • Stateful MPPE encryption--Stateful encryption provides the best performance but might be adversely affected by networks that experience substantial packet loss. Because of the way that the RC4 tables are reinitialized during stateful synchronization, it is possible that two packets might be encrypted using the same key. For this reason, stateful encryption might not be appropriate for lossy network environments (such as Layer 2 tunnels on the Internet). If you configure stateful encryption, the PPTP flow control alarm is automatically enabled.
  • Stateless MPPE encryption--Stateless encryption provides a lower level of performance, but will be more reliable in a lossy network environment. Stateless mode is sometimes referred to as historyless mode. The PPTP flow control alarm is automatically disabled when stateless encryption is being used.

PPTP Flow Control Alarm

The PPTP flow control alarm indicates when congestion or lost packets are detected. When the flow control alarm goes off, PPTP reduces volatility and additional control traffic by falling back from a stateful to a stateless encryption mode for the MPPE session.

How to Configure Client-Initiated VPDN Tunneling

Configuring Client-Initiated Tunneling Using the L2TP or L2TPv3 Protocol

Prerequisites

  • This procedure requires Cisco IOS Release 12.3(2)T or a later release on both the local peer and the tunnel server for L2TPv3 tunneling configurations.
  • This procedure requires Cisco IOS Release 12.3(2)T or a later release on the local peer for L2TP tunneling configurations.
  • Cisco Express Forwarding must be enabled.

Restrictions

  • PPP is the only encapsulation method supported.
  • PPTP tunneling is not supported.
  • Session establishment cannot be triggered by interesting traffic.
  • Failover is not supported with the L2TP peer.
  • L2TP redirect is not supported.

Configuring L2TP or L2TPv3 Client-Initiated VPDN Tunneling on the Local Peer

Perform this task to configure the local peer to initiate VPDN tunnels to the tunnel server. This task applies to both L2TP and L2TPv3 configurations.

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    l2tp-class [l2tp-class-name]

    4.    exit

    5.    pseudowire-class [pw-class-name]

    6.    exit

    7.    interface virtual-ppp number

    8.    ip unnumbered interface-type interface-number

    9.    ppp authentication protocol1 [protocol2...] [if-needed] [list-name | default] [callin] [one-time]

    10.    ppp chap hostname [hostname]

    11.    pseudowire peer-ip-address vcid pw-class pw-class-name [sequencing {transmit | receive | both}]

    12.    exit

    13.    ip route prefix mask {ip-address| interface-type interface-number [ip-address]} [distance] [name] [permanent] [tag tag]


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example:
    Router> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.
     
    Step 2 configure terminal


    Example:
    Router# configure terminal
     

    Enters global configuration mode.

     
    Step 3 l2tp-class [l2tp-class-name]


    Example:
    Router(config)# l2tp-class l2tpclass2
     

    Specifies the L2TP class name and enters L2TP class configuration mode.

    • The l2tp-class-name argument is optional. However, if you want to configure multiple L2TP classes you must specify a unique l2tp-class-namefor each one.
    • You can configure L2TP control channel parameters in L2TP class configuration mode. See the Configuring L2TP Control Channel Parameters for more information.
     
    Step 4 exit


    Example:
    Router(config-l2tp-class)# exit
     

    Exits L2TP class configuration mode.

     
    Step 5 pseudowire-class [pw-class-name]


    Example:
    Router(config)# pseudowire-class pwclass2
     

    Enters pseudowire class configuration mode and optionally specifies the name of the L2TP pseudowire class.

     
    Step 6 exit


    Example:
    Router(config-pw)# exit
     

    Exits pseudowire class configuration mode.

     
    Step 7 interface virtual-ppp number


    Example:
    Router(config)# interface virtual-ppp 2
     

    Enters interface configuration mode and assigns a virtual-PPP interface number.

     
    Step 8 ip unnumbered interface-type interface-number


    Example:
    Router(config-if)# ip unnumbered loopback 1
     

    Enables IP processing on an interface without assigning an explicit IP address to the interface.

     
    Step 9 ppp authentication protocol1 [protocol2...] [if-needed] [list-name | default] [callin] [one-time]


    Example:
    Router(config-if)# ppp authentication chap
     

    Enables Challenge Handshake Authentication Protocol (CHAP) or Password Authentication Protocol (PAP) or both and specifies the order in which CHAP and PAP authentication is selected on the interface.

     
    Step 10 ppp chap hostname [hostname]


    Example:
    Router(config-if)# ppp chap hostname peer2
     

    Creates a pool of dialup routers that all appear to be the same host when authenticating with CHAP.

     
    Step 11 pseudowire peer-ip-address vcid pw-class pw-class-name [sequencing {transmit | receive | both}]


    Example:
    Router(config-if)# pseudowire 172.16.32.24 10 pw-class pwclass2
     

    Specifies the IP address of the tunnel server and the 32-bit virtual circuit identifier (VCID) shared between the devices at each end of the control channel.

    • peer-ip-address vcid --The tunnel server IP address and VCID must be a unique combination on the router.
    Note   

    For L2TPv3 tunnels, the VCID configured on the local peer must match the VCID configured on the tunnel server.

    • pw-class pw-class-name --The pseudowire class configuration from which the data encapsulation type will be taken.The pw-class keyword binds the pseudowire statement to a specific pseudowire class. The pseudowire class then serves as the template configuration for all attachment circuits bound to it.
    • sequencing --The optional sequencing keyword specifies whether sequencing is required for packets that are received, sent, or both received and sent.
    Note   

    If the network between the tunnel endpoints is unreliable, packets might be delivered out of order. Enabling sequencing can reduce the number of dropped packets and network latency.

     
    Step 12 exit


    Example:
    Router(config-if)# exit
     

    Exits interface configuration mode.

     
    Step 13 ip route prefix mask {ip-address| interface-type interface-number [ip-address]} [distance] [name] [permanent] [tag tag]


    Example:
    Router(config)# ip route 10.20.20.0 255.255.255.0 virtual-PPP 1
     

    Establishes static routes.

     
    What to Do Next

    You must perform one of these tasks depending on the tunneling protocol you are configuring:

    • Configuring Client-Initiated Tunneling on the Tunnel Server for L2TP Tunnels
    • Configuring Client-Initiated Tunneling on the Tunnel Server for L2TPv3 Tunnels

    Configuring Client-Initiated Tunneling on the Tunnel Server for L2TP Tunnels

    When a request to establish an L2TP tunnel is received by the tunnel server, the tunnel server must create a virtual access interface. The virtual access interface is cloned from a virtual template interface, used, and then freed when no longer needed. The virtual template interface is a logical entity that is not tied to any physical interface. The tunnel server must be configured to terminate VPDN tunnels.

    Perform this task to configure the tunnel server to terminate client-initiated L2TP tunnels and to configure a basic virtual template.

    Before You Begin
    • You must perform the required tasks in the Configuring AAA for VPDNs module.
    • The same tunneling protocol must be configured on the tunnel server and the local peer device. For L2TP tunnels, the tunneling protocol is configured in a VPDN group on the tunnel server. On the local peer, the tunneling protocol is configured in a pseudowire class.
    SUMMARY STEPS

      1.    enable

      2.    configure terminal

      3.    vpdn-group name

      4.    description string

      5.    accept-dialin

      6.    protocol l2tp

      7.    virtual-template template-number

      8.    exit

      9.    terminate-from hostname hostname

      10.    exit

      11.    interface virtual-template number

      12.    ip unnumbered interface-type interface-number

      13.    ppp authentication protocol1 [protocol2...] [if-needed] [list-name | default] [callin] [one-time]

      14.    ppp chap hostname [hostname]


    DETAILED STEPS
       Command or ActionPurpose
      Step 1 enable


      Example:
      Router> enable
       

      Enables privileged EXEC mode.

      • Enter your password if prompted.
       
      Step 2 configure terminal


      Example:
      Router# configure terminal
       

      Enters global configuration mode.

       
      Step 3 vpdn-group name


      Example:
      Router(config)# vpdn group vpdngroup1
       

      Enters VPDN group configuration mode and associates a VPDN group to a customer or VPDN profile.

       
      Step 4 description string


      Example:
      Router(config-vpdn)# description clientl2tp
       

      (Optional) Adds a description to a VPDN group.

       
      Step 5 accept-dialin


      Example:
      Router(config-vpdn)# accept-dialin
       

      Enters VPDN accept-dialin configuration mode, configures the tunnel server to accept tunneled PPP connections, and creates an accept-dialin VPDN subgroup.

       
      Step 6 protocol l2tp


      Example:
      Router(config-vpdn-acc-in)# protocol l2tp
       

      Specifies the Layer 2 protocol that the VPDN subgroup will use.

       
      Step 7 virtual-template template-number


      Example:
      Router(config-vpdn-acc-in)# virtual-template 1
       

      Specifies which virtual template will be used to clone virtual access interfaces.

       
      Step 8 exit


      Example:
      Router(config-vpdn-acc-in)# exit
       

      Exits VPDN accept-dialin configuration mode.

       
      Step 9 terminate-from hostname hostname


      Example:
      Router(config-vpdn)# terminate-from hostname peer1
       

      Specifies the hostname of the remote LAC or LNS that will be required when accepting a VPDN tunnel.

       
      Step 10 exit


      Example:
      Router(config-vpdn)# exit
       

      Exits VPDN group configuration mode.

       
      Step 11 interface virtual-template number


      Example:
      Router(config)# interface virtual-template 1
       

      Enters interface configuration mode and creates a virtual template interface that can be configured and applied dynamically in creating virtual access interfaces.

       
      Step 12 ip unnumbered interface-type interface-number


      Example:
      Router(config-if)# ip unnumbered loopback 1
       

      Enables IP processing on an interface without assigning an explicit IP address to the interface.

       
      Step 13 ppp authentication protocol1 [protocol2...] [if-needed] [list-name | default] [callin] [one-time]


      Example:
      Router(config-if)# ppp authentication chap
       

      Enables CHAP or PAP or both and specifies the order in which CHAP and PAP authentication is selected on the interface.

       
      Step 14 ppp chap hostname [hostname]


      Example:
      Router(config-if)# ppp chap hostname peer2
       

      Creates a pool of dialup routers that all appear to be the same host when authenticating with CHAP.

       
      What to Do Next

      You must perform the task in the Configuring the Pseudowire.

      Configuring Client-Initiated Tunneling on the Tunnel Server for L2TPv3 Tunnels

      The tunnel server must be configured to terminate VPDN tunnels. The same tunneling protocol must be configured on the tunnel server and the local peer device. For L2TPv3 tunnels, the tunneling protocol is configured in a pseudowire class on both the tunnel server and the local peer.

      Perform this task to configure the tunnel server to terminate client-initiated L2TPv3 tunnels.

      SUMMARY STEPS

        1.    enable

        2.    configure terminal

        3.    l2tp-class [l2tp-class-name]

        4.    exit

        5.    pseudowire-class [pw-class-name]

        6.    exit

        7.    interface virtual-ppp number

        8.    ip unnumbered interface-type interface-number

        9.    ppp authentication protocol1 [protocol2...] [if-needed] [list-name | default] [callin] [one-time]

        10.    ppp chap hostname [hostname]

        11.    pseudowire peer-ip-address vcid pw-class pw-class-name [sequencing {transmit | receive | both}]

        12.    exit

        13.    ip route prefix mask {ip-address| interface-type interface-number [ip-address]} [distance] [name] [permanent] [tag tag]


      DETAILED STEPS
         Command or ActionPurpose
        Step 1 enable


        Example:
        Router> enable
         

        Enables privileged EXEC mode.

        • Enter your password if prompted.
         
        Step 2 configure terminal


        Example:
        Router# configure terminal
         

        Enters global configuration mode.

         
        Step 3 l2tp-class [l2tp-class-name]


        Example:
        Router(config)# l2tp-class l2tpclass2
         

        Specifies the L2TP class name and enters L2TP class configuration mode.

        • The l2tp-class-name argument is optional. However, if you want to configure multiple L2TP classes you must specify a unique l2tp-class-namefor each one.
        • You can configure L2TP control channel parameters in L2TP class configuration mode. See the Configuring L2TP Control Channel Parameters.
         
        Step 4 exit


        Example:
        Router(config-l2tp-class)# exit
         

        Exits L2TP class configuration mode.

         
        Step 5 pseudowire-class [pw-class-name]


        Example:
        Router(config)# pseudowire-class pwclass2
         

        Enters pseudowire class configuration mode and optionally specifies the name of the L2TP pseudowire class.

         
        Step 6 exit


        Example:
        Router(config-pw)# exit
         

        Exits pseudowire class configuration mode.

         
        Step 7 interface virtual-ppp number


        Example:
        Router(config)# interface virtual-ppp 2
         

        Enters interface configuration mode and assigns a virtual-PPP interface number.

         
        Step 8 ip unnumbered interface-type interface-number


        Example:
        Router(config-if)# ip unnumbered loopback 1
         

        Enables IP processing on an interface without assigning an explicit IP address to the interface.

         
        Step 9 ppp authentication protocol1 [protocol2...] [if-needed] [list-name | default] [callin] [one-time]


        Example:
        Router(config-if)# ppp authentication chap
         

        Enables CHAP or PAP or both and specifies the order in which CHAP and PAP authentication is selected on the interface.

         
        Step 10 ppp chap hostname [hostname]


        Example:
        Router(config-if)# ppp chap hostname peer2
         

        Creates a pool of dialup routers that all appear to be the same host when authenticating with CHAP.

         
        Step 11 pseudowire peer-ip-address vcid pw-class pw-class-name [sequencing {transmit | receive | both}]


        Example:
        Router(config-if)# pseudowire 172.16.32.24 10 pw-class pwclass2
         

        Specifies the IP address of the local peer and the 32-bit VCID shared between the local peer and the tunnel server.

        • peer-ip-address vcid --The peer router IP address and VCID must be a unique combination on the router.
        Note   

        The VCID configured on the tunnel server must match the VCID configured on the local peer.

        • pw-class pw-class-name --The pseudowire class configuration from which the data encapsulation type will be taken.The pw-class keyword binds the pseudowire statement to a specific pseudowire class. The pseudowire class then serves as the template configuration for all attachment circuits bound to it.
        • sequencing --The optional sequencing keyword specifies whether sequencing is required for packets that are received, sent, or both received and sent.
        Note   

        If the network between the tunnel endpoints is unreliable, packets might be delivered out of order. Enabling sequencing can reduce the number of dropped packets and network latency.

         
        Step 12 exit


        Example:
        Router(config-if)# exit
         

        Exits interface configuration mode.

         
        Step 13 ip route prefix mask {ip-address| interface-type interface-number [ip-address]} [distance] [name] [permanent] [tag tag]


        Example:
        Router(config)# ip route 10.20.20.0 255.255.255.0 Virtual-PPP 1
         

        Establishes static routes.

         
        What to Do Next

        You must perform the task in the Configuring the Pseudowire.

        Configuring L2TP Control Channel Parameters

        The L2TP class configuration procedure creates a template of L2TP control channel parameters that can be inherited by different pseudowire classes. L2TP control channel parameters are used in control channel authentication, keepalive messages, and control channel negotiation. Configuring L2TP control channel parameters is optional.

        The three groups of L2TP control channel parameters that you can configure for an L2TP class are described in these sections:

        After the router enters L2TP class configuration mode, you can configure L2TP control channel parameters in any order. If you have multiple authentication requirements you can configure multiple sets of L2TP class control channel parameters with different L2TP class names. However, only one set of L2TP class control channel parameters can be applied to a connection between any pair of IP addresses.

        Prerequisites
        L2TP Tunnels

        For L2TP, the L2TP class is configured only on the local peer. An L2TP class was defined for the local peer in the Configuring L2TP or L2TPv3 Client-Initiated VPDN Tunneling on the Local Peer.”

        L2TPv3 Tunnels

        For L2TPv3, an L2TP class must be configured on both the local peer and the tunnel server. An L2TP class was defined for the local peer in the Configuring L2TP or L2TPv3 Client-Initiated VPDN Tunneling on the Local Peer. An L2TP class was defined for the tunnel server in the Configuring Client-Initiated Tunneling on the Tunnel Server for L2TPv3 Tunnels.

        Configuring L2TP Control Channel Timing Parameters

        These L2TP control channel timing parameters can be configured in L2TP class configuration mode:

        • Packet size of the receive window used for the control channel
        • Retransmission parameters used for control messages
        • Timeout parameters used for the control channel

        Perform this task to configure a set of timing control channel parameters for an L2TP class. All of the timing control channel parameter configurations are optional and can be configured in any order. If these parameters are not configured, the default values are applied.

        SUMMARY STEPS

          1.    enable

          2.    configure terminal

          3.    l2tp-class [l2tp-class-name]

          4.    receive-window size

          5.    retransmit {initial retries initial-retries | retries retries| timeout {max | min} timeout}

          6.    timeout setup seconds


        DETAILED STEPS
           Command or ActionPurpose
          Step 1 enable


          Example:
          Router> enable
           

          Enables privileged EXEC mode.

          • Enter your password if prompted.
           
          Step 2 configure terminal


          Example:
          Router# configure terminal
           

          Enters global configuration mode.

           
          Step 3 l2tp-class [l2tp-class-name]


          Example:
          Router(config)# l2tp-class class1
           

          Specifies the L2TP class name and enters L2TP class configuration mode.

          • The l2tp-class-name argument is optional. However, if you want to configure multiple L2TP classes you must specify a unique l2tp-class-namefor each one.
           
          Step 4 receive-window size


          Example:
          Router(config-l2tp-class)# receive-window 30
           

          (Optional) Configures the number of packets that can be received by the remote peer before backoff queueing occurs.

          • The valid values range from 1 to the upper limit the peer has for receiving packets. The default value is the upper limit.
           
          Step 5 retransmit {initial retries initial-retries | retries retries| timeout {max | min} timeout}


          Example:
          Router(config-l2tp-class)# retransmit retries 10
           

          (Optional) Configures parameters that affect the retransmission of control packets.

          • initial retries --Specifies how many start control channel requests (SCCRQs) are re-sent before the device gives up on the session. Valid values for the initial-retries argument range from 1 to 1000. The default value is 2.
          • retries --Specifies how many retransmission cycles occur before the device determines that the peer router does not respond. Valid values for the retries argument range from 1 to 1000. The default value is 15.
          • timeout {max | min}--Specifies maximum and minimum retransmission intervals (in seconds) for resending control packets. Valid values for the timeout argument range from 1 to 8. The default maximum interval is 8; the default minimum interval is 1.
           
          Step 6 timeout setup seconds


          Example:
          Router(config-l2tp-class)#
           
          timeout setup 400
           

          (Optional) Configures the amount of time, in seconds, allowed for setting up a control channel.

          • Valid values for the seconds argument range from 60 to 6000. The default value is 300.
           
          What to Do Next

          You must perform the task in the Configuring the Pseudowire.

          Configuring L2TP Control Channel Authentication Parameters

          These L2TP control channel authentication parameters can be configured in L2TP class configuration mode:

          • Authentication for the L2TP control channel
          • Local hostname used for authenticating the control channel
          • Hiding the attribute-value (AV) pairs in outgoing control messages
          • Password used for control channel authentication and AV pair hiding

          Perform this task to configure a set of authentication control channel parameters for an L2TP class. All of the authentication control channel parameter configurations are optional and can be configured in any order. If these parameters are not configured, the default values will be applied.

          SUMMARY STEPS

            1.    enable

            2.    configure terminal

            3.    l2tp-class [l2tp-class-name]

            4.    authentication

            5.    hostname name

            6.    hidden

            7.    password [encryption-type] password


          DETAILED STEPS
             Command or ActionPurpose
            Step 1 enable


            Example:
            Router> enable
             

            Enables privileged EXEC mode.

            • Enter your password if prompted.
             
            Step 2 configure terminal


            Example:
            Router# configure terminal
             

            Enters global configuration mode.

             
            Step 3 l2tp-class [l2tp-class-name]


            Example:
            Router(config)# l2tp-class class1
             

            Specifies the L2TP class name and enters L2TP class configuration mode.

            • The l2tp-class-name argument is optional. However, if you want to configure multiple L2TP classes you must specify a unique l2tp-class-namefor each one.
             
            Step 4 authentication


            Example:
            Router(config-l2tp-class)# authentication
             

            (Optional) Enables authentication for the control channel between PE routers.

            • Authentication is enabled by default.
             
            Step 5 hostname name


            Example:
            Router(config-l2tp-class)# hostname yb2
             

            (Optional) Specifies a hostname used to identify the router during L2TP control channel authentication.

            • If you do not use this command, the default hostname of the router is used.
             
            Step 6 hidden


            Example:
            Router(config-l2tp-class)#
             
            hidden
             

            (Optional) Hides the AV pairs in control messages.

            • AV pairs are not hidden by default.
             
            Step 7 password [encryption-type] password


            Example:
            Router(config-l2tp-class)#
             
            password tunnel2
             

            (Optional) Configures the password used for control channel authentication.

            • The valid values for the optional encryption type range from 0 to 7. If you do not use this command to specify a password, the password associated with the remote peer PE is taken from the value entered with the username password value global configuration command.
            Note   

            The password configured on the local peer must match the password configured on the tunnel server.

             
            What to Do Next

            You must perform the task in the Configuring the Pseudowire.

            Configuring L2TP Control Channel Maintenance Parameters

            The L2TP hello packet keepalive interval control channel maintenance parameter can be configured in L2TP class configuration mode.

            Perform this task to configure the interval used for hello messages for an L2TP class. This control channel parameter configuration is optional. If this parameter is not configured, the default value will be applied.

            SUMMARY STEPS

              1.    enable

              2.    configure terminal

              3.    l2tp-class [l2tp-class-name]

              4.    hello interval


            DETAILED STEPS
               Command or ActionPurpose
              Step 1 enable


              Example:
              Router> enable
               

              Enables privileged EXEC mode.

              • Enter your password if prompted.
               
              Step 2 configure terminal


              Example:
              Router# configure terminal
               

              Enters global configuration mode.

               
              Step 3 l2tp-class [l2tp-class-name]


              Example:
              Router(config)# l2tp-class class1
               

              Specifies the L2TP class name and enters L2TP class configuration mode.

              • The l2tp-class-name argument is optional. However, if you want to configure multiple L2TP classes you must specify a unique l2tp-class-namefor each one.
               
              Step 4 hello interval


              Example:
              Router(config-l2tp-class)#
               
              hello 100
               

              (Optional) Specifies the exchange interval (in seconds) used between L2TP hello packets.

              • Valid values for the interval argument range from 0 to 1000. The default value is 60.
               
              What to Do Next

              You must perform the task in the Configuring the Pseudowire.

              Configuring the Pseudowire

              The pseudowire class configuration procedure creates a configuration template for the pseudowire. You use this template, or class, to configure session-level parameters for L2TP or L2TPv3 sessions that will be used to transport attachment circuit traffic over the pseudowire.

              The pseudowire configuration specifies the characteristics of the L2TP or L2TPv3 signaling mechanism, including the data encapsulation type, the control protocol, sequencing, fragmentation, payload-specific options, and IP properties. The setting that determines if signaling is used to set up the pseudowire is also included.

              Specifying a source IP address to configure a loopback interface is highly recommended. If you do not configure a loopback interface, the router will choose the best available local address. This configuration could prevent a control channel from being established.

              If you do not configure the optional pseudowire class configuration commands, the default values are used.

              Before You Begin

              L2TP Tunnels

              For L2TP, the pseudowire class is configured only on the local peer. A pseudowire class was defined for the local peer in the task Configuring L2TP or L2TPv3 Client-Initiated VPDN Tunneling on the Local Peer.

              L2TPv3 Tunnels

              For L2TPv3, the pseudowire class must be configured on both the local peer and the tunnel server. A pseudowire class was defined for the local peer in the task Configuring L2TP or L2TPv3 Client-Initiated VPDN Tunneling on the Local Peer. A pseudowire class was defined for the tunnel server in the task Configuring Client-Initiated Tunneling on the Tunnel Server for L2TPv3 Tunnels.

              SUMMARY STEPS

                1.    enable

                2.    configure terminal

                3.    pseudowire-class [pw-class-name]

                4.    encapsulation {l2tpv2 | l2tpv3}

                5.    protocol {l2tpv2 | l2tpv3} [l2tp-class-name]

                6.    ip local interface interface-name

                7.    ip pmtu

                8.    ip tos {value value | reflect}

                9.    ip dfbit set

                10.    ip ttl value

                11.    sequencing {transmit | receive | both}


              DETAILED STEPS
                 Command or ActionPurpose
                Step 1 enable


                Example:
                Router> enable
                 

                Enables privileged EXEC mode.

                • Enter your password if prompted.
                 
                Step 2 configure terminal


                Example:
                Router# configure terminal
                 

                Enters global configuration mode.

                 
                Step 3 pseudowire-class [pw-class-name]


                Example:
                Router(config)# pseudowire-class etherpw
                 

                Enters pseudowire class configuration mode and optionally specifies the name of the L2TP pseudowire class.

                 
                Step 4 encapsulation {l2tpv2 | l2tpv3}


                Example:
                Router(config-pw)# encapsulation l2tpv3
                 

                Specifies the data encapsulation method used to tunnel IP traffic.

                • l2tpv2 --L2TP is the tunneling method to be used to encapsulate data in the pseudowire.
                • l2tpv3 --L2TPv3 is the tunneling method to be used to encapsulate data in the pseudowire.
                 
                Step 5 protocol {l2tpv2 | l2tpv3} [l2tp-class-name]


                Example:
                Router(config-pw)#
                 
                protocol l2tpv3 class1
                 

                Specifies the Layer 2 signaling protocol to be used to manage the pseudowires created with the control channel parameters in the specified L2TP class.

                • l2tpv2 --Specifies L2TP as the signaling protocol to be used.
                • l2tpv3 --Specifies L2TPv3 as the signaling protocol to be used.
                • l2tp-class-name --(Optional) The name of the L2TP class configuration to be used for pseudowires set up from the pseudowire class.
                Note   

                If the l2tp-class-name argument is not specified, the default values for L2TP control channel parameters will be used.

                 
                Step 6 ip local interface interface-name


                Example:
                Router(config-pw)#
                 
                ip local interface e0/0
                 

                Specifies the PE router interface whose IP address is to be used as the source IP address for sending tunneled packets.

                • Use the same local interface name for all pseudowire classes configured between a pair of PE routers.
                Note   

                This command must be configured for pseudowire class configurations using L2TPv3 as the data encapsulation method.

                 
                Step 7 ip pmtu


                Example:
                Router(config-pw)#
                 
                ip pmtu
                 

                (Optional) Enables the discovery of the path maximum transmission unit (PMTU) for tunneled traffic.

                • This command enables the processing of Internet Control Message Protocol (ICMP) unreachable messages that indicate fragmentation errors in the backbone network that carries L2TPv3 session traffic. Also, this command enables MTU checking for IP packets sent into the session and that have the Don’t Fragment (DF) bit set. Any IP packet larger than the MTU is dropped and an ICMP unreachable message is sent. MTU discovery is disabled by default.
                • This command must be enabled in the pseudowire class configuration for fragmentation of IP packets before the data enters the pseudowire to occur.
                Note   

                For fragmentation of IP packets before the data enters the pseudowire, we recommend that you also enable the ip dfbit set command in the pseudowire class configuration. This allows the PMTU to be obtained more rapidly.

                 
                Step 8 ip tos {value value | reflect}


                Example:
                Router(config-pw)# ip tos reflect
                 

                (Optional) Configures the value of the type of service (ToS) byte in IP headers of tunneled packets, or reflects the ToS byte value from the inner IP header.

                • Valid values for the value argument range from 0 to 255. The default ToS byte value is 0.
                 
                Step 9 ip dfbit set


                Example:
                Router(config-pw)# ip dfbit set
                 

                (Optional) Configures the value of the DF bit in the outer headers of tunneled packets.

                • Use this command if (for performance reasons) you do not want reassembly of tunneled packets to be performed on the peer PE router. This command is disabled by default.
                 
                Step 10 ip ttl value


                Example:
                Router(config-pw)# ip ttl 100
                 

                (Optional) Configures the value of the time to live (TTL) byte in the IP headers of tunneled packets.

                • Valid values for the value argument range from 1 to 255. The default TTL byte value is 255.
                 
                Step 11 sequencing {transmit | receive | both}


                Example:
                Router(config-pw)# sequencing both
                 

                (Optional) Specifies the direction in which sequencing of data packets in a pseudowire is enabled.

                • transmit --Updates the Sequence Number field in the headers of data packets sent over the pseudowire according to the data encapsulation method that is used.
                • receive --Keeps the Sequence Number field in the headers of data packets received over the pseudowire. Out-of-order packets are dropped.
                • both --Enables both the transmit and receive options.
                Note   

                If the network between the tunnel endpoints is unreliable, packets might be delivered out of order. Enabling sequencing can reduce the number of dropped packets and network latency.

                 

                Verifying an L2TP Control Channel

                Perform this task to display detailed information about the L2TP control channels that are set up to other L2TP-enabled devices for all L2TP sessions on the router.

                SUMMARY STEPS

                  1.    enable

                  2.    show l2tun tunnel all


                DETAILED STEPS
                   Command or ActionPurpose
                  Step 1 enable


                  Example:
                  Router> enable
                   

                  Enables privileged EXEC mode.

                  • Enter your password if prompted.
                   
                  Step 2 show l2tun tunnel all


                  Example:
                  Router# show l2tun tunnel all
                   

                  Displays the current state of Layer 2 tunnels and information about configured tunnels, including local and remote L2TP hostnames, aggregate packet counts, and control channel information.

                   

                  Configuring Client-Initiated VPDN Tunneling Using the PPTP Protocol

                  Prerequisites for Configuring Client-Initiated VPDN Tunneling Using the PPTP Protocol

                  The client PC must be configured with appropriate VPN client software.

                  Restrictions for Configuring Client-Initiated VPDN Tunneling Using the PPTP Protocol

                  • Only Cisco Express Forwarding and process switching are supported. Regular fast switching is not supported.
                  • PPTP does not support multilink.
                  • VPDN multihop is not supported.
                  • Because all PPTP signaling is over TCP, TCP configurations will affect PPTP performance in large-scale environments.
                  • MPPE is not supported with TACACS.
                  • Windows clients must use Microsoft Challenge Handshake Authentication Protocol (MS-CHAP) authentication in order for MPPE to work.
                  • If you are performing mutual authentication with MS-CHAP and MPPE, both sides of the tunnel must use the same password.
                  • To use MPPE with authentication, authorization, and accounting (AAA), you must use a RADIUS server that supports the Microsoft vendor specific attribute for MPPE-KEYS. CiscoSecure NT supports MPPE beginning with release 2.6. CiscoSecure UNIX does not support MPPE.

                  Configuring the Tunnel Server to Accept PPTP Tunnels

                  The tunnel server must be configured to terminate PPTP tunnels.

                  Perform this task to configure the tunnel server to accept tunneled PPPTP connections from a client.

                  SUMMARY STEPS

                    1.    enable

                    2.    configure terminal

                    3.    vpdn-group name

                    4.    accept-dialin

                    5.    protocol pptp

                    6.    virtual-template template-number


                  DETAILED STEPS
                     Command or ActionPurpose
                    Step 1 enable


                    Example:
                    Router> enable
                     

                    Enables privileged EXEC mode.

                    • Enter your password if prompted.
                     
                    Step 2 configure terminal


                    Example:
                    Router# configure terminal
                     

                    Enters global configuration mode.

                     
                    Step 3 vpdn-group name


                    Example:
                    Router(config)# vpdn-group 1
                     

                    Creates a VPDN group or associates a VPDN group to a customer or VPDN profile and enters VPDN group configuration mode.

                     
                    Step 4 accept-dialin


                    Example:
                    Router(config-vpdn)# accept-dialin
                     

                    Creates an accept dial-in VPDN subgroup that configures a tunnel server to accept requests from a NAS to tunnel dial-in calls, and enters accept dial-in VPDN subgroup configuration mode.

                     
                    Step 5 protocol pptp


                    Example:
                    Router(config-vpdn-acc-in)# protocol pptp
                     

                    Specifies the Layer 2 protocol that the VPDN group will use.

                     
                    Step 6 virtual-template template-number


                    Example:
                    Router(config-vpdn-acc-in)# virtual-template 1
                     

                    Specifies which virtual template will be used to clone virtual access interfaces.

                     
                    What to Do Next

                    You must perform the task in the Configuring the Virtual Template on the Tunnel Server.

                    Configuring the Virtual Template on the Tunnel Server

                    When a request to establish a tunnel is received by the tunnel server, the tunnel server must create a virtual access interface. The virtual access interface is cloned from a virtual template interface, used, and then freed when no longer needed. The virtual template interface is a logical entity that is not tied to any physical interface.

                    Perform this task on the tunnel server to configure a basic virtual template.

                    SUMMARY STEPS

                      1.    enable

                      2.    configure terminal

                      3.    interface virtual-template number

                      4.    ip unnumbered type number

                      5.    ppp authentication protocol1 [protocol2...] [if-needed] [list-name | default] [callin] [one-time] [optional]

                      6.    peer default ip address {ip-address| dhcp-pool | dhcp | pool [pool-name]}

                      7.    encapsulation encapsulation-type

                      8.    ppp encrypt mppe {auto | 40 | 128} [passive | required] [stateful]


                    DETAILED STEPS
                       Command or ActionPurpose
                      Step 1 enable


                      Example:
                      Router> enable
                       

                      Enables privileged EXEC mode.

                      • Enter your password if prompted.
                       
                      Step 2 configure terminal


                      Example:
                      Router# configure terminal
                       

                      Enters global configuration mode.

                       
                      Step 3 interface virtual-template number


                      Example:
                      Router(config)# interface virtual-template 1
                       

                      Enters interface configuration mode and creates a virtual template interface that can be configured and applied dynamically in creating virtual access interfaces.

                       
                      Step 4 ip unnumbered type number


                      Example:
                      Router(config-if)# ip unnumbered FastEthernet 0/0
                       

                      Enables IP processing on a serial interface without assigning an explicit IP address to the interface.

                      Note   

                      Configuring the ip address command within a virtual template is not recommended. Configuring a specific IP address in a virtual template can result in the establishment of erroneous routes and the loss of IP packets.

                       
                      Step 5 ppp authentication protocol1 [protocol2...] [if-needed] [list-name | default] [callin] [one-time] [optional]


                      Example:
                      Router(config-if)# ppp authentication chap
                       

                      Enables at least one PPP authentication protocol and specifies the order in which the protocols are selected on the interface.

                       
                      Step 6 peer default ip address {ip-address| dhcp-pool | dhcp | pool [pool-name]}


                      Example:
                      Router(config-if)# peer default ip address pool mypool
                       

                      Specifies an IP address, an address from a specific IP address pool, or an address from the Dynamic Host Configuration Protocol (DHCP) mechanism to be returned to a remote peer connecting to this interface.

                       
                      Step 7 encapsulation encapsulation-type


                      Example:
                      Router(config-if)# encapsulation ppp
                       

                      Sets the encapsulation method used by the interface.

                       
                      Step 8 ppp encrypt mppe {auto | 40 | 128} [passive | required] [stateful]


                      Example:
                      Router(config-if)# ppp encrypt mppe auto required
                       

                      (Optional) Enable MPPE encryption on the virtual template.

                      • passive --The tunnel server will not offer MPPE encryption, but will negotiate if the other tunnel endpoint requests encryption.
                      • required --MPPE must be negotiated, or the connection will be terminated.
                      • stateful --MPPE will negotiate only stateful encryption. If the stateful keyword is not used, MPPE will first attempt to negotiate stateless encryption, but will allow stateful encryption if the other tunnel endpoint requests the stateful mode.
                       

                      Configuring MPPE on the ISA Card

                      Using the Industry-Standard Architecture (ISA) card to offload MPPE from the Route Processor will improve performance in large-scale environments.

                      Perform this optional task to offload MPPE encryption from the tunnel server processor to the ISA card.


                      Note


                      An ISA card must be installed on the tunnel server.


                      SUMMARY STEPS

                        1.    enable

                        2.    configure terminal

                        3.    controller isa slot / port

                        4.    encryption mppe


                      DETAILED STEPS
                         Command or ActionPurpose
                        Step 1 enable


                        Example:
                        Router> enable
                         

                        Enables privileged EXEC mode.

                        • Enter your password if prompted.
                         
                        Step 2 configure terminal


                        Example:
                        Router# configure terminal
                         

                        Enters global configuration mode.

                         
                        Step 3 controller isa slot / port


                        Example:
                        Router(config)# controller isa 5/0
                         

                        Enters controller configuration mode on the ISA card.

                         
                        Step 4 encryption mppe


                        Example:
                        Router(config-controller)# encryption mppe
                         

                        Enables MPPE encryption on an ISA card.

                         
                        What to Do Next

                        You must reboot your router for the configuration of the encryption mppe command to take effect.

                        Tuning PPTP

                        You can configure PPTP control options to tune the performance of your PPTP deployment. All of the PPTP tuning configuration commands are optional and can be configured in any order. If these parameters are not configured, the default values are applied.

                        SUMMARY STEPS

                          1.    enable

                          2.    configure terminal

                          3.    vpdn-group name

                          4.    pptp flow-control receive-window packets

                          5.    pptp flow-control static-rtt timeout-interval

                          6.    pptp tunnel echo seconds


                        DETAILED STEPS
                           Command or ActionPurpose
                          Step 1 enable


                          Example:
                          Router> enable
                           

                          Enables privileged EXEC mode.

                          • Enter your password if prompted.
                           
                          Step 2 configure terminal


                          Example:
                          Router# configure terminal
                           

                          Enters global configuration mode.

                           
                          Step 3 vpdn-group name


                          Example:
                          Router(config)# vpdn group pptp1
                           

                          Enters VPDN group configuration mode and associates a VPDN group to a customer or VPDN profile.

                           
                          Step 4 pptp flow-control receive-window packets


                          Example:
                          Router(config-vpdn)# pptp flow-control receive-window 20
                           

                          Specifies how many packets the client can send before it must wait for the acknowledgment from the tunnel server.

                           
                          Step 5 pptp flow-control static-rtt timeout-interval


                          Example:
                          Router(config-vpdn)# pptp flow-control static-rtt 2000
                           

                          Specifies the timeout interval of the tunnel server between sending a packet to the client and receiving a response.

                          Note   

                          If the configured timeout interval elapses with no response, the flow control alarm will be triggered.

                           
                          Step 6 pptp tunnel echo seconds


                          Example:
                          Router(config-vpdn)# pptp tunnel echo 90
                           

                          Specifies the period of idle time on the tunnel that will trigger an echo message from the tunnel server to the client.

                           

                          Verifying a PPTP Client-Initiated VPDN Configuration

                          Perform this task to verify that a PPTP client-initiated VPDN configuration functions properly.

                          SUMMARY STEPS

                            1.    Dial in to the NAS from a client PC.

                            2.    From the client PC, establish a PPTP connection to the tunnel server using the VPN client software.

                            3.    From the client, ping the remote network.

                            4.    enable

                            5.    show vpdn

                            6.    show vpdn session all

                            7.    show ppp mppe virtual-access number


                          DETAILED STEPS
                            Step 1   Dial in to the NAS from a client PC.

                            Ensure that the client PC is able to connect to the NAS by establishing a dial-in connection. As the call comes in to the NAS, a LINK-3-UPDOWN message automatically appears on the NAS terminal screen. In the following example, the call comes into the NAS on asynchronous interface 14:



                            Example:
                            *Jan  1 21:22:18.410: %LINK-3-UPDOWN: Interface Async14, changed state to up
                            Note   

                            No debug commands are turned on to display this log message. This message should be displayed within 30 seconds after the client first sends the call.

                            If this message is not displayed by the NAS, there is a problem with the dial-in configuration.
                            Step 2   From the client PC, establish a PPTP connection to the tunnel server using the VPN client software.
                            Step 3   From the client, ping the remote network.

                            From the client desktop:

                            1. Click Start.
                            2. Choose Run.
                            3. Enter ping remote-ip-address .
                            4. Click OK.
                            5. Look at the terminal screen and verify that the remote network is sending ping reply packets to the client.
                            Step 4   enable

                            Enter this command on the tunnel server to enter privileged EXEC mode. Enter your password if prompted:



                            Example:
                            Router> enable
                            
                            Step 5   show vpdn

                            Enter this command on the tunnel server to display information about active tunnels and message identifiers. Verify that the client has established a PPTP session.



                            Example:
                            Router# show vpdn 
                            % No active L2TP tunnels
                            % No active L2F tunnels
                            PPTP Tunnel and Session Information (Total tunnels=1 sessions=1)
                            LocID RemID Remote Name     State    Remote Address  Port  Sessions
                            13    13    10.1.2.41       estabd   10.1.2.41       1136  1       
                            LocID RemID TunID Intf    Username      State   Last Chg
                            13    0     13    Vi3                   estabd  000030        
                            
                            Step 6   show vpdn session all

                            Enter this command for more detailed information about the VPDN session. The last line of output from the show vpdn session all command indicates the current status of the flow control alarm.



                            Example:
                            Router# show vpdn session all 
                            % No active L2TP tunnels
                            % No active L2F tunnels
                            PPTP Session Information (Total tunnels=1 sessions=1)
                            Call id 13 is up on tunnel id 13
                            Remote tunnel name is 10.1.2.41
                             Internet Address is 10.1.2.41
                             Session username is unknown, state is estabd
                             Time since change 000106, interface Vi3
                             Remote call id is 0
                             10 packets sent, 10 received, 332 bytes sent, 448 received
                             Ss 11, Sr 10, Remote Nr 10, peer RWS 16
                             0 out of order packets
                             Flow alarm is clear.
                            
                            Step 7   show ppp mppe virtual-access number

                            Enter this command to display MPPE information for the virtual access interface:



                            Example:
                            Router# show ppp mppe virtual-access 3
                            Interface Virtual-Access3 (current connection)
                              Hardware (ISA5/1, flow_id=13) encryption, 40 bit encryption, Stateless mode
                              packets encrypted = 0        packets decrypted  = 1     
                              sent CCP resets   = 0        receive CCP resets = 0     
                              next tx coherency = 0        next rx coherency  = 0     
                              tx key changes    = 0        rx key changes     = 0     
                              rx pkt dropped    = 0        rx out of order pkt= 0     
                              rx missed packets = 0     
                            

                            To display changed information, reissue the command:



                            Example:
                            Router# show ppp mppe virtual-access 3
                            Interface Virtual-Access3 (current connection)
                              Hardware (ISA5/1, flow_id=13) encryption, 40 bit encryption, Stateless mode
                              packets encrypted = 0        packets decrypted  = 1     
                              sent CCP resets   = 0        receive CCP resets = 0     
                              next tx coherency = 0        next rx coherency  = 0     
                              tx key changes    = 0        rx key changes     = 1     
                              rx pkt dropped    = 0        rx out of order pkt= 0     

                            rx missed packets = 0


                            Configuration Examples for Client-Initiated VPDN Tunneling

                            Example Configuring L2TP Client-Initiated Tunneling

                            The following example configures L2TP client-initiated tunneling on the local peer and the tunnel server. This configuration is for L2TP tunnels.

                            Local Peer Configuration

                            l2tp-class l2tpclass1
                            !
                            pseudowire-class pwclass1
                             encapsulation l2tpv2
                             protocol l2tpv2 l2tpclass1
                             ip local interface ethernet0/0
                            !
                            interface virtual-ppp 1
                             ip unnumbered loopback1
                             ppp authentication chap
                             ppp chap hostname peer1
                             pseudowire 172.24.13.196 10 pw-class pwclass1
                            !
                            ip route 10.10.10.0 255.255.255.0 virtual-PPP 1

                            Tunnel Server Configuration

                            vpdn-group l2tpgroup1
                             accept-dialin
                              protocol l2tp
                              virtual-template 1
                             terminate-from hostname peer1
                            !
                            interface virtual-template 1
                             ip unnumbered loopback 1
                             ppp authentication chap
                             ppp chap hostname peer2

                            Example Configuring L2TPv3 Client-Initiated Tunneling

                            The following example configures L2TP client-initiated tunneling on the local peer and tunnel server. This configuration is for L2TPv3 tunnels.

                            Local Peer Configuration

                            l2tp-class l2tpclass1
                            !
                            pseudowire-class pwclass1
                             encapsulation l2tpv3
                             protocol l2tpv3 l2tpclass1
                             ip local interface ethernet0/0
                            !
                            interface virtual-ppp 1
                             ip unnumbered loopback1
                             ppp authentication chap
                             ppp chap hostname peer1
                             pseudowire 172.24.13.196 15 pw-class pwclass1
                            !
                            ip route 10.10.10.0 255.255.255.0 virtual-PPP 1

                            Tunnel Server Configuration

                            l2tp-class l2tpclass2
                            !
                            pseudowire-class pwclass2
                             encapsulation l2tpv3
                             protocol l2tpv3 l2tpclass2
                             ip local interface ethernet0/1
                            !
                            interface virtual-ppp 2
                             ip unnumbered loopback 1
                             ppp authentication chap
                             ppp chap hostname peer2
                             pseudowire 172.16.32.24 15 pw-class pwclass2
                            !
                            ip route 10.20.20.0 255.255.255.0 virtual-PPP 1

                            Example Verifying an L2TP Control Channel

                            The following output displays detailed information the L2TP control channels that are set up to other L2TP-enabled devices for all L2TP sessions on the router:

                            Router# show l2tun session all 
                            Session Information Total tunnels 0 sessions 1
                            Session id 111 is up, tunnel id 0
                            Call serial number is 0
                            Remote tunnel name is 
                              Internet address is 2.0.0.1
                              Session is manually signalled
                              Session state is established, time since change 00:06:05
                                0 Packets sent, 0 received
                                0 Bytes sent, 0 received
                                Receive packets dropped:
                                  out-of-order:             0
                                  total:                    0
                                Send packets dropped:
                                  exceeded session MTU:     0
                                  total:                    0
                              Session vcid is 123
                            Session Layer 2 circuit, type is ATM VPC CELL, name is ATM3/0/0:1000007
                            Circuit state is UP
                                Remote session id is 222, remote tunnel id 0
                              DF bit off, ToS reflect disabled, ToS value 0, TTL value 255
                              Session cookie information:
                                local cookie, size 8 bytes, value 00 00 00 00 00 00 00 64 
                                remote cookie, size 8 bytes, value 00 00 00 00 00 00 00 C8 
                              SSS switching enabled
                            Sequencing is off

                            Example Configuring Client-Initiated VPDN Tunneling Using PPTP

                            The following example shows the configuration of a tunnel server for client-initiated VPDN tunneling with the PPTP protocol using an ISA card to perform stateless MPPE encryption:

                            vpdn-group pptp1
                            accept-dialin
                              protocol pptp
                              virtual-template 1
                             local name cisco_pns
                            !
                            interface virtual-template 1
                             ip unnumbered FastEthernet 0/0
                             peer default ip address pool mypool
                             encapsulation ppp
                             ppp authentication ms-chap
                             ppp encrypt mppe auto
                            !
                            controller ISA 5/0
                             encryption mppe

                            Where to Go Next

                            You can perform any of the relevant optional tasks in the Configuring Additional VPDN Features and in the VPDN Tunnel Management modules.

                            Additional References

                            Related Documents

                            Related Topic

                            Document Title

                            Cisco IOS commands

                            Cisco IOS Master Commands List, All Releases

                            VPDN commands

                            Cisco IOS VPDN Command Reference

                            VPDN technology overview

                            VPDN Technology Overview module

                            Information about virtual templates

                            Configuring Virtual Template Interfaces module

                            Dial Technologies commands

                            Cisco IOS Dial Technologies Command Reference

                            Technical support documentation for L2TP

                            Layer 2 Tunnel Protocol (L2TP)

                            Technical support documentation for PPTP

                            Point to Point Tunneling Protocol (PPTP)

                            Technical support documentation for VPDNs

                            Virtual Private Dial-Up Network (VPDN)

                            Standards

                            Standard

                            Title

                            None

                            --

                            MIBs

                            MIB

                            MIBs Link

                            • CISCO-VPDN-MGMT-MIB
                            • CISCO-VPDN-MGMT-EXT-MIB

                            To locate and download MIBs for selected platforms, Cisco software releases, and feature sets, use Cisco MIB Locator found at the following URL:

                            http:/​/​www.cisco.com/​go/​mibs

                            RFCs

                            RFC

                            Title

                            RFC 2637

                            Point-to-Point Tunneling Protocol (PPTP)

                            RFC 2661

                            Layer Two Tunneling Protocol L2TP

                            RFC 3931

                            Layer Two Tunneling Protocol - Version 3 (L2TPv3)

                            Technical Assistance

                            Description

                            Link

                            The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

                            http:/​/​www.cisco.com/​cisco/​web/​support/​index.html

                            Feature Information for Client-Initiated VPDN Tunneling

                            The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

                            Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

                            Table 1 Feature Information for Client-Initiated VPDN Tunneling

                            Feature Name

                            Software Releases

                            Feature Configuration Information

                            L2TP Client-Initiated Tunneling

                            12.3(2)T

                            This feature introduces the ability to establish client-initiated L2TP tunnels. The client can initiate an L2TP or L2TPv3 tunnel to the tunnel server without the intermediate NAS participating in tunnel negotiation or establishment.

                            The following commands were introduced or modified by this feature: authentication (L2TP), encapsulation (L2TP), hello, hidden, hostname (L2TP), interface virtual-ppp, ip dfbit set, ip local interface, ip pmtu, ip protocol, ip tos (L2TP), ip ttl, l2tp-class, password (L2TP), protocol (L2TP), pseudowire, pseudowire-class, receive-window, retransmit, sequencing, timeout setup.