How is configuration information sent from master to slave APs from Aruba InstantOS 3.3?

Aruba Employee
Aruba Employee

Environment : This articles applies to all Aruba Instant Access Points running Aruba InstantOS 3.3 or higher.



n the InstantOS versions prior to 3.3, Virtual Controller (VC) used to send out different configuration messages to all slave APs after it receives configuration changes from WEBUI. But it has been observed that in a large size IAP deployments, this behavior might cause VC stay in very busy state frequently.

Master behavior on configuration change:
  • Msater Instant AP assigns a cfg_id (Configuration ID) to every different configuration change.
  • Recording different configuration information and increasing the cfg_id, instead of sending out to every slave Instant AP.
  • If the Slave IAPs cfg_id is different with master, master should send recorded configuration to the slave Instant AP.
  • Master adds cfg_id to message which was sent to Slave Instant AP to update configuration.

Salve behavior on configuration change:
  • Slave sends hearbeat  messages periodically around every 10 seconds.
  • Adds its own cfg_id into heartbeat messsage that is sent to master.
  • After receiving configuration message, updates teh configuration and then its own cfg_id.


Below image gives shows the configuration sync between Master Instant AP and Slave Instant AP:


To know if the configuration in the IAP cluster is synchronized, one need to look at the "current_config_id"  in the Master and Slave Instant APs. Below is command:

#show delta-config

On Master:

rtaImage (1).jpg

On Slave:

rtaImage (2).jpg

As we see in the command output, there are two parameters:

Current_config_id: As the name states this is the current and updated configuration ID from master. If  the value is same for Master and Slave, then the configuration is synchronized between them.

Top_config_ID:  Value for this parameter is seen only in Master IAP. When the existing Master goes down, then the next IAP in the cluster takes the role of new Master and would mention the config_ID that it has last taken from the previous Master in the "top_config_id".


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‎06-27-2014 04:57 PM
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