CUCM upgrade

[Gmurray3]

Question, While doing a CUCM upgrade will the IP phones reboot?  We have failover servers so I would think that the phones will failover to a subscriber.  But will the phones still reboot or just a quick outage to move between primary server and failover server?  Also if a call is active during the failover, will the call be dropped and stay live until the call is completed.

[Roger Kallberg · Accepted solution]

The phones will re-register with the secondary server and create a connection with the tertiary server to be ready to failover to it if needed. All this happen when there are no active call. Nothing will happen to ongoing calls as long as you don’t restart all 3 CM CPE nodes in the assigned CMG at the same time.

[Gmurray3]

Thanks for answer.  This was very helpful.