Moving 12 PRIs with 2 D-channels from Avaya PBX to multiple 3945 routers

[Bill Mungaven]

I'm migrating from an Avaya PBX to CUCM 9.1.2 (to be upgraded to 11.5 or 12.x within 1 year). I have 12 DID PRIs with a primary and secondary D-channel coming from the PSTN terminating on the Avaya. The DID calls are routed from the Avaya to CUCM on 12 PRIs connected between the Avaya and CUCM. The only thing the Avaya switch is doing is passing the PRIs calls to CUCM via 12 PRIs between Avaya and CUCM; the Avaya is only acting as a tandem switch right now.

The last thing I need to do in the migration is to move the 12 DID PRIs to 3 3945 routers running 15.3(3)M6. The 3945s have enough DSPs to land 4 circuits each of the 12; one has enough to land all 12 circuits if necessary. I've been doing some research and found this document which is what I think I need to do: Configuring NFAS with Four T1s. I also found this document helpful: NFAS with D-Channel Backup.

However, I don't want to put all 12 circuits on the same router just so I can group the primary and secondary D-channels; I want to put 4 circuits on each of the 3 routers to spread the load and not have a single point of failure. I don't think I can do this since only 1 router will have the D-channels.

What I don't know is if I have to have the Telco re-provision the circuits in groups of 4 each with its own separate D-channels (primary and backup) since I don't think I can share D-channels across multiple routers. I guess I could have the Telco re-provision the circuits into 12 separate circuits each with their own D-channel. This would make the 3945 configuration much easier.

If anyone has done some similar or can provide any guidance, I would appreciate it.

Bill

[Chris Deren · Accepted solution]

Yes, NFAS is the feature you are after and all NFAS members need to be on the same gateway. You need to work with your telco to either adjust the NFAS membership or better yet, completely get rid of NFAS and have separate D-channel for each PRI, losing few B-channels in this capacity is worth it to eliminate the headache and limitations with NFAS.

[Bill Mungaven]

Chris,

Thanks for confirming what I suspected. I'd prefer to have each circuit with its own D-channel to make the migration easier and for easier troubleshooting.

For the short term, I can move the PRIs to 1 gateway and get NFAS configured.

I'm also working with my Telco to evaluate SIP so I can eventually convert all of my PRIs (34 total) to SIP. This has been a very slow, painful process with my Telco.

I appreciate your information.

Bill