Wireless Access

Under the Managed Network, I created a Cluster Profile called abc_cluster. I pre-staged two controllers configurations under the managed network profile. I entered the mgmt ip for each controller.

Under the newly created Cluster Profile, when I click Add Controller, the IP doesn't appear for either controller. Under the Managed Device Clusters tab, I configured the Cluster group-membership and excluded vlans settings. 

Question: To successfully add a controller into newly created abc_cluster profile, are the controller required to be online and reachable via L2?

Yes.

Not only do you have to have the controllers online to select their IPs in the cluster profile, but if you assign the controllers into that cluster profile, you cannot modify the config of that cluster anymore. In order to modify, you must remove the controllers from the cluster, make the changes, then add them back. This does cause a "blip" to your Wi-Fi clients as I believe the APs radios temporarily drop while they reattach to their controller.

You cannot modify the controllers in a cluster profile if they have a COA VRRP assigned.  If they don't have a COA VRRP, you can modify it.  That bug was introduced in 8.4.0.0 and has been fixed in ArubaOS 8.5.0.7 and 8.6.0.3.