Does Aruba Central consider IAPs in the cluster as down, when license is unassigned for master IAP?
Yes. That is Correct.
Virtual Controller (VC) or Master IAP, is the one who communicates with the Aruba Central on behalf of the entire cluster. Apart from obtaining configuration and commands from Central, it also shares all the statistics of the Instant Cluster. This include the status of slave access points within the cluster, no of clients, RF statistics, application usage statistics, throughput and so on.
Therefore, when the license is un-assigned to the master IAP on Aruba Central, no more data or statistics would be shared with Central, making it to assume the Instant cluster as Down. So Central goes on creating notifications in the event logs, indicating that the IAPs in the cluster went down.
Sample of such notifications in the event log for 10 access points of an Instant Cluster, is shown below:
NOTE: The host part of mac-address is made hidden, in the below output.
Once you re-assign the license to the Master IAP of the cluster, on Aruba Central, then you would see an other set of similar notifications in event logs, where the status would be shown as UP.