RADIUS: Separate Retransmit Counter for Accounting

First Published: February 3, 2003
Last Updated: July 31, 2009

The RADIUS: Separate Retransmit Counter for Accounting feature allows users to configure an exponential backoff retransmit. That is, after the normally configured retransmission retries have been used, the router will keep on trying with an interval that doubles on each retransmission failure until a configured maximum interval is reached. This functionality allows users to retransmit accounting requests for many hours without overloading the RADIUS server when it does come back up.

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 RADIUS: Separate Retransmit Counter for Accounting" 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://tools.cisco.com/ITDIT/CFN/jsp/index.jsp. An account on Cisco.com is not required.

Contents

•Restrictions for RADIUS: Separate Retransmit Counter for Accounting

•Information About RADIUS: Separate Retransmit Counter for Accounting page 1

•How to Configure RADIUS: Separate Retransmit Counter for Accounting

•Configuration Examples for RADIUS: Separate Retransmit Counter for Accounting

•Additional References

•Feature Information for RADIUS: Separate Retransmit Counter for Accounting

Restrictions for RADIUS: Separate Retransmit Counter
for Accounting

The following tasks will result in excessive memory consumption on the router:

•Configuring this feature on a router with a high call rate.

•Configuring the aaa accounting send stop-record authentication failure command: an accounting record and a RADIUS packet will be generated for each user that fails to authenticate while the RADIUS server is down.

•Configuring interim accounting: new accounting records are generated and stored on the router.

Information About RADIUS: Separate Retransmit Counter
for Accounting

To configure RADIUS: Separate Retransmit Counter for Accounting, you should understand the following concepts:

•How Retransmission of Accounting Requests Works

•Benefits

How Retransmission of Accounting Requests Works

In many environments, a single RADIUS server is used for authentication and accounting. Whenever this server is down for approximately 24 hours, the accounting records of users already on the router are lost after authentication, authorization, and accounting (AAA) does all the retransmissions. Before the introduction of this feature, the retransmissions could be configured for a maximum of 100 retries and the timeout could be configured for 1,000 seconds. Although these configurations keep the accounting records on the router for 24 hours, a timeout of 1,000 seconds is unreasonable, causing problems when the RADIUS server cannot be reached due to network congestion.

The RADIUS: Separate Retransmit Counter for Accounting feature allows users to configure an exponential backoff retransmit. That is, after the normally configured retransmission retries have been used, the router will keep on trying with an interval that doubles on each retransmission failure until a configured maximum interval is reached. This functionality allows users to retransmit accounting requests for many hours without overloading the RADIUS server when it does come back up.

This feature can be configured globally (via the radius-server backoff exponential command), per server (via the radius-server host command), or per group (via the backoff exponential command).

Benefits

With this feature, users can extend the time in which the RADIUS client (the router) sends accounting requests to the RADIUS server in the event that the RADIUS server or the connection to the server is down and there is no accounting response confirmation. This functionality enables accounting records to remain on the router for up to 24 hours.

How to Configure RADIUS: Separate Retransmit Counter
for Accounting

This section contains the following tasks:

•Configuring a Retransmit Counter for Accounting Globally or per RADIUS Host (required)

•Configuring a Retransmit Counter for Accounting per RADIUS Server Group (required)

•Verifying Retransmit Configurations (optional)

Configuring a Retransmit Counter for Accounting Globally or per RADIUS Host

To configure exponential backoffs of RADIUS retransmits over an extended period of time on a global basis and per RADIUS host, perform the following steps:

SUMMARY STEPS

1. enable

2. configure terminal

3. radius-server backoff exponential [max-delay minutes] [backoff-retry retransmits]

4. radius-server host {hostname | ip-address} [test username user-name] [auth-port port-number] [ignore-auth-port] [acct-port port-number] [ignore-acct-port] [timeout seconds] [retransmit retries] [key string] [alias {hostname | ip-address}] [idle-time seconds] [backoff exponential {backoff-retry number-of-retransmits | key encryption-key | max-delay minutes}]

DETAILED STEPS

 
Command
Purpose

Step 1 

enable

Example:

Router> enable

Enters privileged EXEC mode.

Enter your password if prompted.

Step 2 

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3 

Router(config)# radius-server backoff exponential [max-delay minutes] [backoff-retry retransmits]

Example:

Router (config)# radius-server backoff exponential max-delay 60 backoff-retry 32

Configures the router for exponential backoff retransmit of accounting requests.

Step 4  

Router(config)# radius-server host 
{hostname | ip-address} [test username 
user-name] [auth-port port-number] 
[ignore-auth-port] [acct-port 
port-number] [ignore-acct-port] [timeout 
seconds] [retransmit retries] [key 
string] [alias {hostname | ip-address}] 
[idle-time seconds] [backoff exponential 
{backoff-retry number-of-retransmits | 
key encryption-key | max-delay minutes}]
Example:

Router (config)# radius-server host 192.0.2.1 test username test1 auth-port 1645 acct-port 1646

Specifies a RADIUS server host and configures that RADIUS server host for exponential backoff retransmit of accounting requests.

Configuring a Retransmit Counter for Accounting per RADIUS Server Group

To configure exponential backoffs of RADIUS retransmits over an extended period of time per RADIUS server group, perform the following steps:

SUMMARY STEPS

1. enable

2. configure terminal

3. aaa group server radius group-name

4. backoff exponential [max-delay minutes] [backoff-retry retransmits]

DETAILED STEPS

 
Command
Purpose

Step 1 

enable

Example:

Router> enable

Enters privileged EXEC mode.

•Enter your password if prompted.

Step 2 

configure terminal

Example:

Router (config)# configure terminal

Enters global configuration mode.

Step 3 

Router(config)# aaa group server radius group-name

Groups different RADIUS server hosts into distinct lists and distinct methods and enters server-group RADIUS configuration mode.

Step 4 

Router(config-sg-radius)# backoff exponential [max-delay minutes] [backoff-retry retransmits]

Configures the router for exponential backoff retransmit of accounting requests per RADIUS server group.

Verifying Retransmit Configurations

To verify feature functionality, use any of the following EXEC commands:

SUMMARY STEPS

1. enable

2. debug radius

3. show accounting

4. show radius statistics

DETAILED STEPS

 
Command
Purpose

Step 1 

enable

Example:

Router> enable

Enters privileged EXEC mode.

•Enter your password if prompted.

Step 2 

debug radius

Example:

Router# debug radius

Displays information associated with RADIUS.

Step 3 

show accounting

Example:

Router# show accounting

Displays all active sessions and prints all the accounting records for actively accounted functions.

Step 4 

show radius statistics

Example:

Router# show radius statistics

Displays the RADIUS statistics for accounting packets.

Configuration Examples for RADIUS: Separate Retransmit Counter for Accounting

This section provides the following configuration examples:

•Retransmit Counter for Accounting Comprehensive Configuration: Example

•Per-Server Configuration: Example

Retransmit Counter for Accounting Comprehensive Configuration: Example

The following example shows how to configure your router for exponential backoff retransmit of accounting requests. In this example, an exponential backoff is configured globally (via the radius-server backoff exponential command) and for the RADIUS server host "172.107.164.206" (via the radius-server host command). 

aaa new-model

aaa authentication login default group radius

aaa authentication ppp default group radius

aaa authorization exec default group radius 

aaa authorization network default group radius 

aaa accounting send stop-record authentication failure 

aaa accounting update periodic 1

aaa accounting network default start-stop group radius

!

radius-server host 172.107.164.206 auth-port 1645 acct-port 1646 backoff exponential 
max-delay 60 backoff-retry 32 

radius-server backoff exponential max-delay 60 backoff-retry 32 

radius-server retransmit 3

radius-server key rad123

end

Per-Server Configuration: Example

The following example shows how to enable exponential backoff retransmits on a per-server basis. In this example, assume that the retransmit is configured for 3 retries and the timeout is configured for 5 seconds; that is, the RADIUS request will be transmitted 3 times with a delay of 5 seconds. Thereafter, the router will continue to retransmit RADIUS requests with a delayed interval that doubles each time until 32 retries have been achieved. The router will stop doubling the retransmit intervals after the interval surpasses the configured 60 minutes; it will transmit every 60 minutes. 

radius-server host foo.xyz.com backoff exponential max-delay 60 backoff-retry 32

After enabling this command, the retransmits will be sent as follows ("t" equals seconds): 

t = 0 req sent 

t = 5 retrans 1 

t = 10 retrans 2 

t = 15 retrans 3 

t = 25 retrans 4 

t = 45 retrans 5 

t = 85 retrans 6 

t = 165 retrans 7 

t = 325 retrans 8 

t = 645 retrans 9 

t = 1285 retrans 10 

t= 2565 retrans 11 

t = 5125 retrans 12 

t = 8725 retrans 13 (The interval has stabilized to 60 minutes here). 

t = 12325 retrans 14 till retransmit 35

After all the retransmits are sent, the RADIUS request follows the same path that it would when all the normal retransmits are done.

Additional References

The following sections provide references related to the RADIUS: Separate Retransmit Counter for Accounting.

Related Documents

Related Topic
Document Title

RADIUS and AAA accounting configuration tasks and commands

•The chapters "Configuring RADIUS"and "Configuring Accounting"in the Cisco IOS XE Security Configuration Guide: Configuring User Services, Release 2

•Cisco IOS Security Command Reference


Standards

Standard
Title

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

—


MIBs

MIB
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 software releases, and feature sets, use Cisco MIB Locator found at the following URL:

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


RFCs

RFC
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

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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 RADIUS: Separate Retransmit Counter for Accounting

Table 1 lists the release history for this feature.

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://tools.cisco.com/ITDIT/CFN/jsp/index.jsp. An account on Cisco.com is not required.

Note Table 1 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 1 Feature Information for RADIUS: Separate Retransmit Counter for Accounting

Feature Name
Releases
Feature Information

RADIUS: Separate Retransmit Counter for Accounting

Cisco IOS XE Release 2.1

The RADIUS: Separate Retransmit Counter for Accounting feature allows users to configure an exponential backoff retransmit. That is, after the normally configured retransmission retries have been used, the router will keep on trying with an interval that doubles on each retransmission failure until a configured maximum interval is reached. This functionality allows users to retransmit accounting requests for many hours without overloading the RADIUS server when it does come back up.

In Cisco IOS XE Release 2.1, this feature was introduced on the Cisco ASR 1000 Series Aggregation Services Routers.

The following commands were introduced or modified: backoff exponential, radius-server host, radius-server backoff exponential.


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