Preparing for Broadband Access Aggregation

First Published: May 2, 2005
Last Updated: August 11, 2009

Before you begin to perform the tasks required to accomplish broadband access aggregation, there are some preparatory tasks that you can perform at your option to enable you to complete the aggregation task with more efficiency.

A virtual template interface saves time because all PPP parameters are managed within the virtual template configuration. Any configurations made in the virtual template are automatically propagated to the individual virtual access interfaces.

Using the enhancement for broadband scalability reduces the amount of memory that is used per terminated PPP session by creating virtual access subinterfaces. Determining if virtual access subinterfaces are available on your system and preconfiguring these enhancements can speed your aggregation process and improve system performance.

Finding Feature Information

For the latest feature information and caveats, see 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 for Preparing for Broadband Access Aggregation" section.

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

Contents

•Restrictions for Preparing for Broadband Access Aggregation

•Information About Preparing for Broadband Access Aggregation

•How to Prepare for Broadband Access Aggregation

•Configuration Examples for Preparing for Broadband Access Aggregation

•Additional References

•Feature Information for Preparing for Broadband Access Aggregation

Restrictions for Preparing for Broadband Access Aggregation

The following restriction apply:

•Due to high scaling requirements, only virtual access subinterfaces are supported. Disabling virtual access subinterfaces is not supported.

•Precloning virtual access interfaces is not supported.

Information About Preparing for Broadband Access Aggregation

To prepare for broadband access aggregation, you should understand the following concepts:

•Virtual Access Interfaces

•Configuration Enhancements for Broadband Scalability

Virtual Access Interfaces

A virtual template interface is used to provide the configuration for dynamically created virtual access interfaces. It is created by users and can be saved in NVRAM.

Once the virtual template interface is created, it can be configured in the same way as a serial interface.

Virtual template interfaces can be created and applied by various applications such as virtual profiles, virtual private dialup networks (VPDNs), and protocol translation.

All PPP parameters are managed within the virtual template configuration. Configuration changes made to the virtual template are automatically propagated to the individual virtual access interfaces. Multiple virtual access interfaces can originate from a single virtual template.

Cisco IOS XE software supports up to 4096 virtual template configurations. If greater numbers of tailored configurations are required, an authentication, authorization, and accounting (AAA) server can be used.

If the parameters of the virtual template are not explicitly defined before the interface is configured, the PPP interface is brought up using default values from the virtual template. Some parameters (such as an IP address) take effect only if specified before the PPP interface comes up. Therefore, it is recommended that you explicitly create and configure the virtual template before configuring the interface to ensure that such parameters take effect. Alternatively, if parameters are specified after the interface has been configured, use the shutdown command followed by the no shutdown command on the subinterface to restart the interface; this restart will cause the newly configured parameters (such as an IP address) to take effect.

Configuration Enhancements for Broadband Scalability

The Configuration Enhancements for Broadband Scalability feature reduces the amount of memory that is used per terminated PPP session by creating virtual access subinterfaces. Depending on the configuration of the source virtual template, virtual access subinterfaces may be available. This feature also introduces a command to determine if a virtual template is compatible with virtual access subinterfaces.

Virtual Access Subinterfaces

The virtual-template command supports existing features, functions, and configurations. By default, the virtual-template subinterface command is enabled; this command cannot be disabled.

The virtual template manager will determine if the set of options configured on the virtual template are all supported on a subinterface. Virtual access subinterfaces will be created for all virtual templates that support subinterfaces. If the user has entered any commands that are not supported on a subinterface, a full virtual access interface is created and cloned for all PPP sessions using that virtual template.

Different applications can use the same virtual template even if one application is subinterface-capable and another is not. The virtual template manager is notified whether the application supports virtual access subinterfaces and creates the appropriate resource.

Virtual Template Compatibility with Subinterfaces

The test virtual-template subinterface privileged EXEC command determines whether a virtual template can support the creation of a virtual access subinterface. If the virtual template contains commands that prevent the creation of subinterfaces, the test virtual-template subinterface command identifies and displays these commands.

The debug vtemplate subinterface command displays debug messages that are generated if you enter configuration commands on the virtual template that are not valid on a subinterface. These messages are generated only if the debug vtemplate subinterface command is enabled, the virtual-template subinterface command is enabled, and a virtual template is configured that can support the creation of subinterfaces. If the creation of virtual access subinterfaces is disabled by the no virtual-template subinterface command, the debug vtemplate subinterface command produces no output.

Benefits of Broadband Scalability Features

Using broadband scalability reduces the amount of memory that is used per terminated PPP session by creating virtual access subinterfaces. These virtual access subinterfaces, along with improvements that are transparent to the user, speed up the cloning process.

How to Prepare for Broadband Access Aggregation

This section contains the following procedures:

•Configuring a Virtual Template Interface

•Configuring Enhancements for Broadband Scalability

Configuring a Virtual Template Interface

Configure a virtual template before you configure PPPoE on a Gigabit Ethernet interface. The virtual template interface is a logical entity that is applied dynamically as needed to an incoming PPP session request. To create and configure a virtual template interface, enter the following commands beginning in global configuration mode:

SUMMARY STEPS

1. enable

2. configure terminal

3. interface virtual-template number

4. ip unnumbered loopback number

5. mtu bytes

6. ppp authentication chap

7. ppp ipcp ip address required

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 virtual-template number

Example:

Router(config)# interface virtual-template 1

Creates a virtual template interface and enters interface configuration mode.

Step 4 

ip unnumbered loopback number

Example:

Router(config-if)# ip unnumbered loopback 0

Enables IP without assigning a specific IP address on the LAN.

Step 5 

mtu bytes

Example:

Router(config-if)# mtu 1492

(Optional) Sets the maximum MTU size for the interface.

Note MTU size can be set only to 1492 or 1500. To set MTU size greater than 1492, you must use the tag ppp-max-payload command.

Step 6 

ppp authentication chap

Example:

Router(config-if)# ppp authentication chap

Enables PPP authentication on the virtual template interface.

Step 7 

ppp ipcp ip address required

Example:

Router(config-if)# ppp ipcp ip address required

Prevents a PPP session from being set up without a valid address being negotiated.

This command is required for legacy dialup and DSL networks.

Examples

The following example shows the configuration of a virtual template interface: 

interface virtual-template 1

 ip unnumbered Loopback 0

 no peer default ip address

 ppp authentication chap vpn1

 ppp authorization vpn1

 ppp accounting vpn1

Configuring Enhancements for Broadband Scalability

To configure enhancement for broadband scalability, you will perform the following task:

•Verifying Virtual Template Compatibility with Virtual Access Subinterfaces

Verifying Virtual Template Compatibility with Virtual Access Subinterfaces

Perform the following task to test a virtual template to determine if it is compatible with the creation of virtual access subinterfaces.

SUMMARY STEPS

1. enable

2. test virtual-template template subinterface

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

enable

Example:

Router> enable

Enables privileged EXEC mode.

•Enter your password if prompted.

Step 2 

test virtual-template template subinterface

Example:

Router# test virtual-template virtual-template1 subinterface

Tests the specified virtual template to determine if it is compatible with the creation of virtual access subinterfaces.

Examples

The output generated by the test virtual-template subinterface command describes the compatibility of the virtual template with the creation of subinterfaces.

This example shows output indicating that the virtual template is not compatible. This output also includes a list of the commands, which are configured on the virtual template, that cause the incompatibility. 


Router# test virtual-template virtual-template1 subinterface 


Subinterfaces cannot be created using 

Virtual-Template1


Interface commands:

traffic-shape rate 50000 8000 8000 1000

Configuration Examples for Preparing for Broadband Access Aggregation

This section provides the following configuration examples:

•Virtual Access Subinterfaces Configuration: Examples

Virtual Access Subinterfaces Configuration: Examples

This section provides the following configuration examples:

•Virtual Access Subinterface Configuration: Example

•Testing a Virtual Template for Compatibility with Subinterfaces: Example

Virtual Access Subinterface Configuration: Example

The example that follows shows a virtual template that is compatible with virtual access subinterfaces:

Note The virtual-access subinterface command is enabled by default and does not appear in running configurations. Only the no virtual-access subinterface command will appear in running configurations. 

interface Virtual-Template1

 ip unnumbered Loopback0

 peer default ip address pool pool-1

 ppp authentication chap

 ppp multilink

The following example shows a configuration in which the creation of virtual access subinterfaces has been disabled by the no virtual-access subinterface command. When this command is configured, virtual access interfaces are not registered with the SNMP code on the router. In network environments that do not use SNMP to manage PPP sessions, this saves the memory and CPU processing that would be used to register the virtual access interfaces with the SNMP code. 


Current configuration :6003 bytes

!


! Last configuration change at 10:59:02 EDT Thu Sep 19 2004

!

version 12.2

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption

service internal

service udp-small-servers

service tcp-small-servers

!

hostname ioswan5-lns

!

enable password lab

!

username cisco password 0 cisco

clock timezone EST -5

clock summer-time EDT recurring

aaa new-model

!

!

aaa authentication ppp default local


aaa authorization network default local 

aaa session-id common

ip subnet-zero

no ip gratuitous-arps

ip cef

!

!

no ip domain lookup

ip name-server 10.44.11.21

ip name-server 10.44.11.206

!

ip vrf vpn1

rd 10:1

route-target export 10:1

route-target import 10:1

!

vpdn enable

!

vpdn-group 1

accept-dialin

protocol l2tp

virtual-template 1

terminate-from hostname ioswan5-lac

local name tunnel1

l2tp tunnel password 7 01100F175804

!

! 

!

no virtual-template subinterface

no virtual-template snmp

virtual-template 1 pre-clone 10

!         

! 

!         

buffers small permanent 20000

buffers middle permanent 7500

!         

!         

!         

interface Loopback1

ip address 10.111.1.1 255.255.255.0

Testing a Virtual Template for Compatibility with Subinterfaces: Example

This example shows the process for testing a virtual template to determine if it can support virtual access subinterfaces. The following command displays the configuration for virtual template 1: 

Router# show running interface virtual-template 1


Building configuration...

!

interface Virtual-Template1

ip unnumbered Loopback0

peer default ip address pool pool-1

ppp authentication chap

traffic-shape rate 50000 8000 8000 1000

end

The test virtual-template subinterface command tests virtual template 1 to determine if it can support subinterfaces. The output shows that the traffic-shape rate command that is configured on virtual template 1 prevents the virtual template from being able to support subinterfaces. 

Router# test virtual-template 1 subinterface


Subinterfaces cannot be created using Virtual-Template1

Interface commands:

traffic-shape rate 50000 8000 8000 1000

Additional References

The following sections provide references related to preparing for broadband access aggregation.

Related Documents

Related Topic
Document Title

Broadband access aggregation of PPPoE Sessions

Providing Protocol Support for Broadband Access Aggregation of PPPoE Sessions

Specifying a range for the ppp-max payload tag value

PPP-Max-Payload and IWF PPPoE Tag Support

Additional information about commands used in this document

•Cisco IOS Broadband Access Aggregation and DSL Command Reference

•Cisco IOS Master Command List, All Releases


Standards

Standards
Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

—


MIBs

MIBs
MIBs Link

No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

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

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


RFCs

RFCs
Title

No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.

—


Technical Assistance

Description
Link

The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies.

To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.

Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

http://www.cisco.com/techsupport


Feature Information for Preparing for Broadband Access Aggregation

Table 4 lists the features in this module and provides links to specific configuration information

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS XE software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Note Table 4 lists only the Cisco IOS XE software release that introduced support for a given feature in a given Cisco IOS XE software release train. Unless noted otherwise, subsequent releases of that Cisco IOS XE software release train also support that feature.

Table 4 Feature Information for Preparing for Broadband Aggregation

Feature Name
Software Releases
Feature Configuration Information

Virtual Sub-Interface—Configuration Enhancements for Broadband Scalability

Cisco IOS XE Release 2.1

This feature was introduced on Cisco ASR 1000 Series Routers.

This feature reduces the amount of memory that is used per terminated PPP session by creating virtual access subinterfaces. Depending on the configuration of the source virtual template, virtual access subinterface may be available. This feature also introduces a command to determine if a virtual template is compatible with virtual access subinterfaces.

The following sections provide information about this feature:

•Configuring Enhancements for Broadband Scalability

•Virtual Access Subinterfaces Configuration: Examples



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