Switch version into upgraded partition when ready on Pub
Once up and running change all Device Default Firmware back to originals – only needs to be done after Pub upgrade
Verify server health of Pub…others may not be available
Switch version on other Subs – note here that calls between devices registered to servers on different versions of CUCM may not work due to SDL being broken so plan to always have all the phones on one version or the other.
Turn on EM
POST
RTMT again
Server health
DB Replication between all nodes
Any alerts
Registered Device and distribution again – check against screen shot taken earlier