Cisco CUCM Cluster and Phone Registration Question

[MarcusWoodard61583]

I have two CUCM Clusters, for this example I'll call them CUCM Cluster A and CUCM Cluster B. They are both on the same network (different vlans). Cluster A and B have their own CUCM Pub and CUCM Sub. Cluster A and B do connect via SIP Trunk for internal dialing.

We have two buildings, Building A and Building B. 

Building A's phones register to the CUCM Cluster A.

Building B's phones register to the CUCM Cluster B.

The issue now is Building A's phones are going to Building B, but need to stay registered to CUCM Cluster A, not the CUCM Cluster B. And vice versa.

What's going to be the easiest where someone can just pick up there phone, move between the buildings, but still keep their extension and registered to their CUCM cluster? 

I know there is the manually Alternate TFTP process which forces the phone to stay registered to that CUCM cluster. I'm aware of the VLAN and Option 150 that can be configured on the network, but isn't this process more for a 1 to 1 solution (1 network and 1 CUCM cluster). 

Thanks for your helps,

MW

[Nithin Eluvathingal]

Consider utilizing Extension Mobility Cross Cluster if updating option 150 or using an alternative TFTP is not feasible.

Here are the options available to you in this scenario:

• Update option 150 to point to Cluster A’s TFTP in Building B, ensuring phones register to Cluster A.
• Manually define an alternative TFTP server.
• Utilize Extension Mobility Cross Cluster (ensure you have completed the cross-cluster configurations between Cluster A and B).

[Roger Kallberg · Accepted solution]

Even if a user takes the phone and moves it from building A to B and the phone then would get option 150 that points to the CM that serves building B the phone would not register to the other CM as it would not have the cluster B CMs in its trust list. With this it will continue to remain registered to cluster A, at least as long as you do not factory reset the phone. On the option 150 part, in some more advanced DHCP servers you can override the scope defined settings on individual IP reservation to point for example option 150 to the cluster where the phone belongs.

[MarcusWoodard61583]

That's right the ITL certificate. I forgot about that. I will accept this as the answer I was looking for. Thank You.