Providing Protocol Support for Broadband Access Aggregation of PPP over ATM Sessions

PPP over ATM enables a high-capacity central site router with an ATM interface to terminate multiple remote Point-to-Point Protocol (PPP) connections. PPP over ATM provides security validation per user, IP address pooling, and service selection capability.

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.

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 Providing Protocol Support for Broadband Access Aggregation of PPP over ATM Sessions

Perform the preparation tasks in the "Preparing for Broadband Access Aggregation" module.

Restrictions for Providing Protocol Support for Broadband Access Aggregation of PPP over ATM Sessions

PPP over ATM cannot be configured on IETF-compliant Logical Link Control (LLC) encapsulated PPP over ATM.

Information About Providing Protocol Support for Broadband Access Aggregation of PPP over ATM Sessions

Virtual Access Interface

When you configure PPP over ATM, a logical interface known as a virtual access interface associates each PPP connection with an ATM virtual circuit (VC). You can create this logical interface by configuring an ATM permanent virtual circuit (PVC) or switched virtual circuit (SVC). This configuration encapsulates each PPP connection in a separate PVC or SVC, thus allowing each PPP connection to terminate at the ATM interface of a device as if received from a typical PPP serial interface.

After you have configured the device for PPP over ATM, the PPP subsystem starts and the device attempts to send a PPP configuration request to the remote peer. If the peer does not respond, the router periodically goes into a listen state and waits for a configuration request from the peer.

Before you create the ATM VC, we recommend that you create and configure a virtual template as described in the "Preparing for Broadband Access Aggregation" module. When the VC is created, the virtual access interface for each VC obtains the configuration from a virtual interface template (virtual template) .

The virtual access interface is associated with the VC after the completion of the LCP negotiation. When the PPP session goes down, the virtual access interface is no longer associated with the VC and is returned to the pool of free virtual-access interfaces.

If you set a keepalive timer of the virtual template on the interface, the virtual access interface uses the PPP echo mechanism to verify the existence of the remote peer.

The following types of PPP over ATM connections are supported:

  • IETF-compliant Multiplex (MUX) encapsulated PPP over ATM

  • IETF-compliant LLC encapsulated PPP over ATM

How to Provide Protocol Support for Broadband Access Aggregation of PPP over ATM Sessions

Configuring IETF-Compliant MUX Encapsulated PPP over ATM on Point-to-Point Subinterface

Internet Engineering Task Force (IETF)-compliant multiplexer (MUX) encapsulated PPP over ATM, also known as null encapsulation , allows you to configure PPP over ATM using a VC multiplexed encapsulation mode. This feature complies with IETF RFC 2364 entitled PPP over AAL5.

You can configure ATM PVCs for IETF-compliant MUX encapsulated PPP over ATM on either point-to-point or multipoint subinterfaces.

Perform this task to configure IETF-compliant MUX Encapsulated PPP over ATM point-to-point subinterface.

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    interface atm number.subinterface-number point-to-point

    4.    Do one of the following:

    • pvc [name] vpi / vci
    • range [range-name] pvc start-vpi / start-vci end-vpi / end-vci

    5.    encapsulation aal5mux ppp virtual-template number

    6.    Do one of the following:

    • end


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example:
    Device> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.

     
    Step 2 configure terminal


    Example:
    Device# configure terminal
     

    Enters global configuration mode.

     
    Step 3 interface atm number.subinterface-number point-to-point


    Example:
    Device(config)# interface atm 1.0 point-to-point
     

    Specifies the ATM point-to-point subinterface using the appropriate form of the interface atmcommand1 and enters subinterface configuration mode.

     
    Step 4Do one of the following:
    • pvc [name] vpi / vci
    • range [range-name] pvc start-vpi / start-vci end-vpi / end-vci


    Example:
    Device(config-subif)# pvc cisco 0/5


    Example:
    or


    Example:
    Device(config-subif)# range range1 pvc 1/200 1/299
     

    Configures the PVC or a range of PVCs and enters ATM virtual circuit subinterface mode or ATM range subinterface configuration mode.

     
    Step 5 encapsulation aal5mux ppp virtual-template number


    Example:
    Device(config-subif-atm-vc)# encapsulation aal5mux ppp virtual-template 3


    Example:
    or


    Example:
    Device(config-subif-atm-range)# encapsulation aal5mux ppp virtual-template 3
     

    Configures VC multiplexed encapsulation on a PVC or PVC range.

     
    Step 6Do one of the following:
    • end


    Example:
    Device(config-subif-atm-vc)# end


    Example:
       or


    Example:
    Device(config-subif-atm-range)# end
     

    Exits ATM virtual circuit range subinterface configuration mode.

    or

    Exits ATM range subinterface configuration mode.

     
    1 To determine the correct form of the interface atm command, consult your ATM shared port adapters documentation.

    Configuring IETF-Compliant MUX Encapsulated PPP over ATM on a Multipoint Subinterface

    Multiple PVCs on multipoint subinterfaces significantly increase the maximum number of PPP-over-ATM sessions running on a device. You can configure IETF-compliant MUX encapsulated PPP over ATM on a single ATM PVC or an ATM PVC range.

    Perform this task to configure IETF-compliant MUX Encapsulated PPP over ATM on a multipoint subinterface.

    SUMMARY STEPS

      1.    enable

      2.    configure terminal

      3.    interface atm number.subinterface-number multipoint

      4.    Do one of the following:

      • pvc [name] vpi / vci
      • range [range-name] pvc start-vpi / start-vci end-vpi / end-vci

      5.    encapsulation aal5mux ppp virtual-template number

      6.    Do one of the following:

      • end


    DETAILED STEPS
       Command or ActionPurpose
      Step 1 enable


      Example:
      Device> enable
       

      Enables privileged EXEC mode.

      • Enter your password if prompted.

       
      Step 2 configure terminal


      Example:
      Device# configure terminal
       

      Enters global configuration mode.

       
      Step 3 interface atm number.subinterface-number multipoint


      Example:
      Device(config)# interface atm 1/0/0.4 multipoint
       

      Specifies the ATM multipoint subinterface using the appropriate form of the interface atmcommand and enters subinterface configuration mode.

       
      Step 4Do one of the following:
      • pvc [name] vpi / vci
      • range [range-name] pvc start-vpi / start-vci end-vpi / end-vci


      Example:
      Device(config-subif)# pvc cisco 0/5


      Example:
      or


      Example:
      Device(config-subif)# range range1 pvc 1/200 1/299
       

      Configures the PVC or a range of PVCs and enters ATM virtual circuit subinterface mode or ATM range subinterface configuration mode.

       
      Step 5 encapsulation aal5mux ppp virtual-template number


      Example:
      Device(config-subif-atm-vc)# encapsulation aal5mux ppp virtual-template 3


      Example:
      or


      Example:
      Device(config-subif-atm-range)# encapsulation aal5mux ppp virtual-template 3
       

      Configures VC multiplexed encapsulation on a PVC or PVC range.

       
      Step 6Do one of the following:
      • end


      Example:
      Device(config-subif-atm-vc)# end


      Example:


      Example:
      Device(config-subif-atm-range)# end
       

      Exits ATM virtual circuit subinterface configuration mode.

      or

      Exits ATM range subinterface configuration mode.

       

      Configuring IETF-Compliant LLC Encapsulated PPP over ATM on a Point-to-point Subinterface

      IETF-compliant LLC encapsulated PPP over ATM allows you to configure PPP over ATM with LLC encapsulation. It accommodates Frame Relay-to-ATM service interworking (Frame Relay Forum standard FRF.8). There is no equivalent VC multiplexed encapsulation mode for Frame Relay; therefore, LLC encapsulation is required for Frame Relay-to-ATM networking. This version of PPP over ATM also enables you to carry multiprotocol traffic. For example, a VC will carry both PPP and IPX traffic.

      The figure below shows Frame Relay-to-ATM interworking.

      Figure 1. Frame Relay-to-ATM Interworking

      You can configure ATM PVCs for IETF-compliant LLC encapsulated PPP over ATM on either point-to-point or multipoint subinterfaces. Multiple PVCs on multipoint subinterfaces significantly increase the maximum number of PPP-over-ATM sessions running on a router.

      Perform this task to configure IETF-compliant LLC encapsulated PPP over ATM PVC or range of PVCs on a point-to-point interface.

      SUMMARY STEPS

        1.    enable

        2.    configure terminal

        3.    interface atm number.subinterface-number point-to-point

        4.    Do one of the following:

        • pvc [name] vpi / vci
        • range [range-name] pvc start-vpi / start-vci end-vpi / end-vci

        5.    encapsulation aal15snap

        6.    protocol ppp virtual-template number

        7.    Do one of the following:

        • end


      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 atm number.subinterface-number point-to-point


        Example:
        Router(config)# interface atm 6.200 point-to-point
         

        Specifies the ATM point-to-point or multipoint subinterface using the appropriate form of the interface atm command2 and enters subinterface configuration mode.

         
        Step 4Do one of the following:
        • pvc [name] vpi / vci
        • range [range-name] pvc start-vpi / start-vci end-vpi / end-vci


        Example:
        Router(config-subif)# pvc cisco 0/5


        Example:
        or


        Example:
        Router(config-subif)# range range1 pvc 1/200 1/299
         

        Configures the PVC or a range of PVCs and enters ATM virtual circuit subinterface mode or ATM range subinterface configuration mode.

         
        Step 5 encapsulation aal15snap


        Example:
        Router(config-subif-atm-vc)# encapsulation aal15snap


        Example:
        or


        Example:
        Router(config-subif-atm-range)# encapsulation aal15snap
         

        Configures LLC SNAP encapsulation on the PVC or a range of PVCs.3

         
        Step 6 protocol ppp virtual-template number


        Example:
        Router(config-subif-atm-vc)# protocol ppp virtual-template 2


        Example:
        or


        Example:
        Router(config-subif-atm-range)# protocol ppp virtual-template 2
         

        Configures IETF PPP over ATM LLC encapsulation on the PVC or a range of PVCs.

         
        Step 7Do one of the following:
        • end


        Example:
        Router(config-subif-atm-vc)# end


        Example:
        or


        Example:
        Router(config-subif-atm-range)# end
         

        Exits ATM virtual circuit subinterface configuration mode.

        or

        Exits ATM range subinterface configuration mode.

         
        2 To determine the correct form of the interface atm command, consult your ATM shared port adapters documentation.
        3 "SNAP encapsulation" is a misnomer here, since this encapsulation configures both LLC and SNAP encapsulation on the VC. If SNAP encapsulation is not configured at a lower inheritance level, or another type of encapsulation is configured at a lower inheritance level, you will have to configure both SNAP and the protocol ppp command to ensure that PPP over ATM with LLC encapsulation is configured on your VC.

        Configuring IETF-Compliant LLC Encapsulated PPP over ATM on a Multipoint Subinterface

        Multiple PVCs on multipoint subinterfaces significantly increase the maximum number of PPP-over-ATM sessions running on a Device.

        Perform this task to configure IETF-compliant LLC encapsulated PPP over ATM PVC or a range of PVCs on a multipoint subinterface.

        SUMMARY STEPS

          1.    enable

          2.    configure terminal

          3.    interface atm number.subinterface-number multipoint

          4.    Do one of the following:

          • pvc [name] vpi / vci
          • range [range-name] pvc start-vpi / start-vci end-vpi / end-vci

          5.    encapsulation aal5mux ppp virtual-template number

          6.    protocol ppp virtual-template number

          7.    Do one of the following:

          • end


        DETAILED STEPS
           Command or ActionPurpose
          Step 1 enable


          Example: 
          Device> enable
           

          Enables privileged EXEC mode.

          • Enter your password if prompted.

           
          Step 2 configure terminal


          Example: 
          Device# configure terminal
           

          Enters global configuration mode.

           
          Step 3 interface atm number.subinterface-number multipoint


          Example: 
          Device(config)# interface atm 1/0/0.4 multipoint
           

          Specifies the ATM multipoint subinterface using the appropriate form of the interface atmcommand4 and enters subinterface configuration mode.

           
          Step 4Do one of the following:
          • pvc [name] vpi / vci
          • range [range-name] pvc start-vpi / start-vci end-vpi / end-vci


          Example: 
          Device(config-subif)# pvc cisco 0/5


          Example: 
          or


          Example: 
          Device(config-subif)# range range1 pvc 1/200 1/299
           

          Configures the PVC or a range of PVCs and enters ATM virtual circuit subinterface mode or ATM range subinterface configuration mode.

           
          Step 5 encapsulation aal5mux ppp virtual-template number


          Example: 
          Device(config-subif-atm-vc)# encapsulation aal5mux ppp virtual-template 3


          Example: 
          or


          Example: 
          Device(config-subif-atm-range)# encapsulation aal5mux ppp virtual-template 3
           

          Configures VC multiplexed encapsulation on a PVC or PVC range.

           
          Step 6 protocol ppp virtual-template number


          Example: 
          Device(config-subif-atm-vc)# protocol ppp virtual-template 2


          Example: 
          or


          Example: 
          Device(config-subif-atm-range)# protocol ppp virtual-template 2
           

          Configures IETF PPP over ATM LLC encapsulation on the PVC or a range of PVCs.

           
          Step 7Do one of the following:
          • end


          Example: 
          Device(config-subif-atm-vc)# end


          Example:


          Example: 
          Device(config-subif-atm-range)# end
           

          Exits ATM virtual circuit subinterface configuration mode.

          or

          Exits ATM range subinterface configuration mode.

           
          4 To determine the correct form of the interface atm command, consult your ATM shared port adapters documentation.
          What to Do Next

          You can also configure IETF-compliant LLC encapsulated PPP over ATM in a VC class and apply this VC class to an ATM VC, subinterface, or interface. For information about configuring a VC class, see the "Configuring VC Classes" section in the Configuring ATM module.

          Configuration Examples for PPP over ATM

          IETF-Compliant MUX Encapsulated PPP over ATM Configuration

          This section provides the following examples for configuring IETF-compliant PPP over ATM:

          Example: ETF-Compliant PPP over ATM with Different Traffic-Shaping Parameters

          PVCs with different PPP-over-ATM traffic-shaping parameters can be configured on the same subinterface. In the following example, three PVCs are configured for PPP over ATM on subinterface ATM 2/0.1. PVC 0/60 is configured with IETF-compliant PPP over ATM encapsulation. Its traffic-shaping parameter is an unspecified bit rate with peak cell rate at 500 kb/s. PVC 0/70 is also configured with IETF-compliant PPP over ATM encapsulation, but its traffic-shaping parameter is nonreal-time variable bit rate, with peak cell rate at 1 Mb/s, sustainable cell rate at 500 kb/s, and burst cell size of 64 cells. 

          interface atm 2/0.1 multipoint 
 pvc 0/60 
  encapsulation aal5mux ppp virtual-template 3 
   ubr 500 
  exit 
pvc 0/70 
 encapsulation aal5mux ppp virtual-template 3 
 vbr-nrt 1000 500 64 
  exit

          Example: Two Routers with Back-to-Back PVCs

          The figure below illustrates an ATM interface with two PPP sessions over two PVC session connections. The sample commands following the figure establish the back-to-back router configuration.

          Figure 2. Two Routers with Back-to-Back PVCs

          R1 Configuration
          interface atm 2/0 
atm clock internal 
pvc 0/60 
encapsulation aal5mux ppp virtual-template 1 
ubr 90 
exit 
pvc 0/70 
encapsulation aal5mux ppp virtual-template 2 
vbr-nrt 90 50 1024 
exit 
interface virtual-template 1 
ip address 10.0.1.1 255.255.255.0 
interface virtual-template 2 
ip address 10.0.2.1 255.255.255.0 
exit
          R2 Configuration
          interface atm 2/0.1 multipoint 
pvc 0/60 
encapsulation aal5mux ppp virtual-template 1 
ubr 90 
exit 
pvc 0/70 
encapsulation aal5mux ppp virtual-template 2 
vbr-nrt 90 50 1024 
exit 
exit 
interface virtual-template 1 
ip address 10.0.1.2 255.255.255.0 
exit 
interface virtual-template 2 
ip address 10.0.2.2 255.255.255.0

          Example: Multiplexed Encapsulation Using VC Class

          In the following example, PVC 0/60 is configured on subinterface ATM 2/0.1 with a VC class attached to it. By rule of inheritance, PVC 0/60 runs with IETF-compliant PPP over ATM encapsulation using the configuration from interface virtual-template 1. Its parameter is an unspecified bit rate with peak cell at 90 kb/s. 

          interface atm 2/0/0.1 
pvc 0/60 
class-vc pvc-ppp 
exit 
exit 
vc-class atm pvc-ppp 
encapsulation aal5mux ppp virtual-template 1 
ubr 90 
exit

          IETF-Compliant LLC Encapsulated PPP over ATM Configuration

          This section provides the following examples for configuring IETF-compliant LLC encapsulated PPP over ATM:

          Example: Configuring IETF-Compliant PPP over ATM LLC Encapsulation

          This example shows how to configure IETF PPP over ATM LLC encapsulation in the VC class called ppp-default. The VC class specifies virtual template 1 from which to spawn PPP interfaces, SNAP encapsulation (the default), and a UBR class traffic type at 256 kb/s. When the VC class ppp-default is configured on interface 0.1, PVC 0/70 inherits these properties. PVC 0/80 overrides virtual template 1 in the VC class and uses virtual template 2 instead. PVC 0/90 also overrides virtual template 1 and uses virtual template 3 instead. In addition, PVC 0/90 uses a VC multiplexed encapsulation and a UBR class traffic type at 500 kb/s. 

          interface atm 2/0/0.1 multipoint 
class-int ppp-default 
! 
pvc 0/70 
exit 
! 
pvc 0/80 
protocol ppp virtual-template 2 
exit 
! 
pvc 0/90 
encapsulation aal5mux ppp virtual-template 3 
ubr 500 
exit 
exit 
! 
vc-class atm ppp-default 
protocol ppp virtual-template 1 
ubr 256 
exit

          Example: Overriding a Virtual Template for IETF-Compliant PPP over ATM

          This example illustrates how to use inheritance to override a virtual template configuration for muxppp encapsulation options. For PVC 5/505 the encapsulation option at that level is ciscoppp virtual template 1, as specified in the VC class called muxppp, the protocol ppp virtual-template 2 command overrides only the virtual-template configuration. 

          interface atm 2/0/0.1 
class-int muxppp 
! 
pvc 5/505 
protocol ppp virtual-template 2 
exit 
! 
muxppp 
encapsulation aal5mux ppp virtual-template 1 
exit

          Example: Disabling IETF-Compliant PPP over ATM LLC Encapsulation on a Specific VC

          This example shows how to limit the configuration of a particular LLC encapsulated protocol to a particular VC. First, we see that the VC class called ppp is configured with IETF PPP over ATM with LLC encapsulation and virtual template 1. This VC class is then applied to ATM interface 1/0/0. By configuring SNAP encapsulation by itself on PVC 0/32, you disable IETF PPP over ATM with LLC encapsulation on this particular PVC; PVC 0/32 will only carry IP. 

          interface atm 1/0/0 
class-int ppp 
exit 
! 
interface atm 1/0/0.100 point-to-point 
description IP only VC 
ip address 10.1.1.1 255.255.255.0 
pvc 0/32 
encapsulation aal5snap 
exit 
exit 
! 
vc-class atm ppp 
encapsulation aal5snap 
protocol ppp virtual-template 1 
exit

          Additional References

          Related Documents

          Related Topic

          Document Title

          Cisco IOS commands

          Cisco IOS Master Commands List, All Releases

          Broadband and DSL commands

          Cisco IOS Broadband and DSL Command Reference

          Broadband access aggregation preparation tasks

          Preparing for Broadband Access Aggregation

          Configuring ATM

          Configuring ATM

          Standards/RFCs

          Standards

          Title

          Frame Relay Forum standard FRF.8

          Frame Relay to ATM Internetworking

          RFC 2364

          PPP over AAL5

          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 Providing Protocol Support for Broadband Access Aggregation of PPP over ATM Sessions

          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 Providing Protocol Support for Broadband Access Aggregation of PPP over ATM Sessions

          Feature Name

          Releases

          Feature Configuration Information

          PPP over ATM

          Cisco IOS XE Release 3.3S

          Cisco IOS Release XE 3.14S

          PPP over ATM provides support for the termination of multiple PPP connections on an ATM interface of a router.

          In Cisco IOS XE Release 3.3S, this feature was introduced on the Cisco ASR 1000 Series Aggregation Services Routers.

          In Cisco IOS XE Release 3.14S, support for this feature was added on the Cisco 4451-X Integrated Services Router.

          The following commands were introduced or modified:

          encapsulation aal5mux ppp virtual-template , interface atm, protocol ppp virtual-template, pvc, range.