We are doing a CUCM cluster upgrade from physical 8.0.3 to virtual 8.6(2a). There is 1 pub and 1 sub. We are doing the 8.6 upgrade in an isolated VM environment before going live to test and reduce downtime. Which brings me to my question:
The phones will upgrade their firmware load to 9-2-1 when we go live with the 8.6 cluster. If we have issues and need bring the 8.0.3 cluster back online, will the phones have issues registering/functioning with the 8.0.3 cluster using the 9-2-1 loads versus the 8.0.3 default 9-0-3 load?
I'm not anticipating issues, but we never do and we all know how these things can go
Thanks to all!
it will work.
One nice way to mitigate all this additional overhead during the upgrade window
and/or reverting to 8.0.3 is to upgrade the phone firmware ahead of time.
We have done this on all our upgrades over the last few years.
This way you can have the phones on 9-2-1 ahead of time and will save you time
and effort during the "upgrade" window
"Why not help one another on the way" - Bob Marley