Environment : Aruba Instant version 126.96.36.199-188.8.131.52 and IAP-105 is used for all the sample output provided in this article.
"Auto Join mode" feature allow IAPs to discover the virtual controller and join the cluster. This feature is enabled by default.
Disabling "Auto Join" mode on Master IAP would not effect other member IAPs that joined the cluster earlier. The moment this option is disabled, MAC addresses of all the active member IAPs in the cluster would be added as allowed-APs in the Virtual Controller's configuration automatically.
Any new IAP that needs to be joined to the cluster has to be manually allowed by adding its MAC address.
--> Login to IAP Web Interface
--> Under list of IAPs, Click on "New" and enter the IAP Mac address that you want to join