Dial Configuration Guide, Cisco IOS Release 15.5M&T

Alternate Sources for IP Address Pools

The Asynchronous Line Monitoring feature feature is useful in large-scale dial-out environments with large numbers of independently controlled AAA servers that can make it difficult for the NAS to provide proper IP address pool resolution in the following cases:

• A new pool name is introduced by one of the AAA servers before that pool is set up on the NAS.
• An existing local pool becomes exhausted, but the owner of that AAA server has other pools that would be acceptable as an IP address source.

The Asynchronous Line Monitoring feature feature introduces two new interface configuration commands, peer pool backup and peer pool static, which allow you to define alternate sources for IP address pools in the event the original address pool is not present or is exhausted.

Backup Pools to Prevent Local Pool Exhaustion

The problems of pool name resolution and specific local pool exhaustion can be solved by configuring backup pool names on a per-interface basis using the peer default ip address pool and peer pool backup interface configuration commands. The peer pool backup command uses the local pool names configured with the peer default ip address pool interface configuration command to supplement the pool names supplied by AAA.

Limit Loading of Dynamic Pools

The peer pool static command controls attempts by the pool software to load dynamic pools in response to a pool request from a specific interface. These dynamic pools are loaded at system startup and refreshed whenever a pool name not configured on the NAS is specified for IP address allocation. Because the behavior of the NAS in response to a missing pool name can be changed using the peer pool backup interface configuration command, you can use the peer pool static command to control attempts to load all dynamic pools when the AAA-supplied pool name is not an existing local pool name.

Peer Pool Backup Feature Interface Compatibility

The Asynchronous Line Monitoring feature feature has been successfully tested at Cisco Systems in networks using ISDN, asynchronous, and digital subscriber line (DSL) interfaces.

Configuring IP Pools

Perform the following task to create one or more local IP address pools and directs the pool software to use the local pool name that is configured with the peer default ip address pool interface configuration command, to supplement the pool names supplied by AAA.

SUMMARY STEPS

1. enable

2. configure terminal

3. interface type number

4. peer pool backup

5. peer default ip address pool pool-name-list

6. exit

7. ip local pool { named-address-pool | default } { first-IP-address [ last-IP-address ]} [ group group-name ] [ cache-size size ]

8. exit

DETAILED STEPS

This task configures basic IP address pooling and pool backup. See the “Configuration Examples for Peer Pool Backup” section for additional configuration information.

Suppressing Dynamic Pool Load Attempts

Perform the following task to suppress an attempt to load all dynamic pools from the AAA server.

SUMMARY STEPS

1. enable

2. configure terminal

3. interface type number

4. peer pool static

5. exit

DETAILED STEPS

See the “Configuration Examples for Peer Pool Backup” section for additional configuration information.

Verifying Asynchronous Line Monitoring feature

Perform this task to verify that the peer pool backup command has been configured correctly. The report from the debug ip peer command indicates the order in which the pool software searches for IP address pools. The report should also indicate that only the backup IP address pools are searched; any attempt to load a dynamic IP address pool will be suppressed when the peer pool static command is configured, or if the pools were refreshed within the last two minutes.

SUMMARY STEPS

1. enable

2. debug ip peer

DETAILED STEPS

Step 1 enable

Use this command to enter privileged EXEC mode. Enter your password if prompted.

Router> enable

Step 2 debug ip peer

Use this command to display a report about backup pool activity. Comments are enclosed within <angle brackets> and commands involved in the reports are in bold text.

Verifying That a Pool Was Not Skipped

When the IP pool backup configuration is verified, there may be a situation where the dynamic pools were recently refreshed and messages will indicate that pool refresh was not done. The following partial output from the debug ip peer command shows how this situation would be reported; comments are enclosed within <angle brackets> and commands involved in the reports are in bold text.

Monitoring and Maintaining Asynchronous Line Monitoring feature

To display statistics for any defined IP address pool, use the show ip local pool EXEC command.

ISDN Pool Backup Configuration: Example

In the following partial example, the IP address pools configured with the peer default ip address pool command are searched by the pool software in the event the original address pool is not present:

DSL Static Pool Backup Configuration: Example

In the following partial example of a DSL network configuration, the peer pool static command prevents any attempt by the AAA server to load a dynamic IP address pool:

Pool Backup with Local Restrictions Configuration: Example

You can apply local restrictions on the use of a AAA-supplied pool name by using the peer match aaa-pools interface configuration command in the pool backup configuration. The peer match aaa-pools command allows you to specify that any AAA-supplied pool name must match one of the pool names supplied with the peer default ip address pool command.

In the following example, assume that there is a AAA-supplied IP address pool named poolA. When the peer match aaa-pools command is added to the configuration, the pool named poolA will not be used because it does not appear in the peer default ip address pool command; only the pools named pool1 and pool2 will be searched.

In the following example, a pool named poolA is added to the peer default ip address pool command list, so that now poolA will be used by the pool software and the search order will be poolA, pool1, and then pool2. The pool named poolA is used first because AAA-supplied data is always given precedence over local data.

The debug ip peer command would show the following messages for these configurations (comments are in <angle brackets> and use bold text to indicate commands involved in the reports.):

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Cisco and the Cisco logo are trademarks or registered trademarks of Cisco and/or its affiliates in the U.S. and other countries. To view a list of Cisco trademarks, go to this URL: www.cisco.com/go/trademarks. Third-party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1110R)

Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

© 2007–2009 Cisco Systems, Inc. All rights reserved.