Just a couple of questions about a CUCM Cluster Upgrade.
So I've got a 2 server cluster. If I move all my devices off the PUB and onto the SUB, I upgrade the PUB first.
Once the PUB is upgraded, how do I get the devices to re-register from the SUB to the PUB if I wanted to simply test the PUB. Because if I go onto the SUB after the PUB has been upgraded, I can't make any changes, so I can't change the server order of the device pool.
or is it a simple case of not being able to fully test until both have been upgraded?
I'd appreciate some advice,