Adding new SUB to PUB

[jacob.landry]

We had a subscriber that failed so we will be doing a fresh install on new hardware and attaching it to the PUB.  All of our phones are currently registered to the PUB.  My question is will there be a service interruption when we connect the SUB to the PUB?

[Georgios Fotiadis]

No, not at all. They only thing you may notice is a slight increases in resource usage because of DB replication. But you have nothing to worry about.

[Jaime Valencia]

After you install a new node in an existing cluster, all phones that are registered to the cluster are reset.

https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/install/11_5_1/cucm_b_installation-guide-cucm-imp-1151.pdf

[Georgios Fotiadis]

Very good point! I had never noticed that.

[Jonathan Schulenberg]

Also, you should be performing a DRS restore on the new node if it’s replacing an existing one. Use identical platform details (eg hostname, IP, etc) and then perform a restore after the node is installed.
https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/install/11_5_1/replace/cucm_b_replacing-single-server-or-cluster-1151/cucm_b_replacing-single-server-or-cluster-1151_chapter_010.html#CUCM_TK_RDD3EA62_00