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.

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 Action Purpose

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 atm command1 and enters subinterface configuration mode.

Step 4

Do 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

Do 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 Action Purpose

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 atm command and enters subinterface configuration mode.

Step 4

Do 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

Do 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 Action Purpose

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 4

Do 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 7

Do 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 Action Purpose

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 atm command4 and enters subinterface configuration mode.

Step 4

Do 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 7

Do 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

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.