Upgrading CUCM and CUC, which should I do first?

[helpdesk147]

I need to upgrade my CUCM and CUC servers from 11.5(SU4) to 11.5(SU11). My questions are, Do I need to do the CUCM first then the CUC or does it matter which ones I do first? I have read through the upgrade guides and I didn't see anywhere that explicitly says do one before the other. I am reading them at work so I might have missed it. Second do I have to do them both at the same time? I am worried about how long it will take compared to my maintenance windows. Any guidance is greatly appreciated.

[Roger Kallberg · Accepted solution]

You can do them in any order and they do not need to be done simultaneously. The most common order would be to do CM first and then CUC, but it is not a must.

[helpdesk147]

Thank you Roger! My main reason for doing this is to get the CUC O365 connector off of basic authentication. I would like to start with that. Would there be any advantage of doing it the CM first?

[Roger Kallberg · Accepted solution]

Not any specific that I can come to think of right now. If your main concern is with CUC I don’t think that you’ll run into any issues if you do that first.