[Ask Expert] Is it possible to use 2 CUCM and 1 Voice gateway ?

[SK T1]

Hello Cisco Expert,

Due to I've the CUCM connect to SIP trunk to Voice gateway. My customer need to migrate some IP Phone to their standard CUCM (The new one, new supplier) on another place.. 

I've 2 questions ;

1. Is it possible to use only one Voice gateway to working with 2 CUCM ?

They've 600 IP Phones and need migrated the 1st lot of 100 IP Phones to register with the new CUCM.

Old topology

Phones (600) ----- Old CUCM version 9 ---SIP--- Voice gateway

Migration Topology (Expected)

Phones (500) ----- Old CUCM version 9 ----SIP--- Voice gateway ---SIP--- New CUCM version 10.x ---- Phones (100)

Finally 

Voice gateway ---SIP--- New CUCM version 10.x ---- Phones (600)

2. Is there any dial-peer or translation rules need to modify ? They've E1 ISDN PRI  with pots dial-peer.

[Terry Cheema]

Yes you can use the same VG from two CUCM as long as it is H323 or SIP and you will need some additional dial-peers to send/receive calls from new CUCM.

Not sure if I understand correctly but you can also have direct SIP trunk between the both CUCMs as well - Leave PSTN connectivity through existing CUCM, phones on different cluster can talk to each other over SIP trunk and if they need to dial out to PSTN you can route over to SIP trunk to the existing CUCM - which will route through PSTN gateway.

-Terry

Please rate all helpful posts

[Mohammed al Baqari]

+5 Terry. In addition, take a note that ITL files need to be delete on the 100 phones before migration. Otherwise they won't register with the new CUCM cluster.

Also, you will require some smart digit manipulation and dialpeers combination if you are looking to use the same DID range for both old and new clusters in parallel during the migration phase.