I have a pair of ISE appliances running 18.104.22.168 code.
I have the 2 nodes setup as primary and secondary and they were synced OK.
There was a DNS issue in the network and the ISE nodes were not able to resolve the hostname of the other node so the link between the 2 dropped.
The DNS issue was resolved but the connection stayed down and there doesn't seem to be anyway to re-initiate the connection.
My solution was to de-register the secondary node and then register it again. However, although the de-registration seemed to go OK, the secondary node never came back up in standlaone mode so I was unable to register it on the primary again.
The only solution seemed to be to re-image the appliance.
This seems a very drastic solution for a simple issue such as DNS failing.
Does anyone have any useful comments on this issue?