How to configure standby APM

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Article ID: 167908

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Updated On:

Products

XOS

Issue/Introduction

Describes process of configuring a standby APM

Cause

The Crossbeam X-Series Platform provides the ability to have one or more APMs configured as a Standby VAP.

A standby VAP is an APM that is not assigned to any VAP group. The standby VAP is loaded with the VAP image of a failed VAP when required. 

If an APM running in a VAP group fails, the standby VAP is dynamically allocated to the VAP group. The standby VAP is loaded to run the image of the failed VAP.

Resolution

The APM to be used as Standby must be located in a slot included in the ap-list for that VAP group.

The default setting is to include all slots, however, it is good practice to configure a specific list for each VAP group. Use the following command to specify the VAP group ap-list
configure vap-group <VAP-GROUP-NAME> ap-list <put_your_list>

In order to confirm APM slot locations, use the following show command: 
# show chassis

Note: Putting an APM into maintenance mode does not trigger a failover to standby APM.


If the number of active VAPs in a VAP group  is lower than max-load-count set for this VAP group, then system will look for APMs in the ap-list. When an available standby APM is found, it will be loaded with the image of the failed VAP. 

As an alternative to configuring a standby VAP, preemption priority can be assigned to each VAP group. This allows you to configure an application in a VAP group as a higher or lower priority compared to another application. Should a higher priority VAP group have a failure, a VAP from the lower priority group will be taken. This configuration works well when you have a mission critical application and a non-mission critical application running in the same X-Series Platform.