Redundant voice gateways?

[mfwilkinson]

I currently have a single voice gateway which is a 2821 ISR serving four PRIs. I'd like to make this redundant. I do have the CUCM redundancy/failover set up, but nothing for my 2821 voice gateway. I was thinking a T1 failover switch with the PRIs from the PSTN connected to it, then to two 2821 ISRs (one primary and one standby); that part seems pretty straightforward. However, what I don't understand, and the documentation I can't seem to find, is how to set up CUCM with multiple voice gateways (rather failover endpoints).

Because the T1 failover switch keeps the failover side of the PRIs dark, the 2nd 2821 gateway will essentially have no connectivity to PRIs. And if, in a failover situation, the now failed endpoints on the primary 2821 will be dark and still be in my route group. Is there a graceful way to handle this in CUCM?

[George Thomas · Accepted solution]

For redundancy from CUCM perspective, you will have to assign the two gateways to a route group and both the route groups to a route list and select the distribution algorithm you required. Also make sure you change the service parameter "Stop routing on unallocate number" to False for failover to work. 

What people have done is they split the PRIs across two gateways so that if one gateway goes down, the 2nd gateway routes the call without manual intevention. The same will have to be configured by the provider (basically put all PRIs in a single trunkgroup) so that failover for inbound calls also work.

[Oussama.bachiri]

Hi,

If you have one voice gateway, in this case to assure Redundancy with CUCM configure 2 voip dial-peer with different preference.

and if you want to assure Redundancy with PSTN you will need two up T1 line to the ISP switch and then configure 2 pots dial-peer with different preference.

Good Luck.

[mfwilkinson]

We finally have this implemented; to summarize I did exactly what George proposed. We didn't use HSRP a load balancer or any fanciness like that. Just two VoIP gateways on different IP addresses and spread multiple PRIs over one trunkgroup. We did also implement a T1 failover switch and mixed the live PRIs and fail-over PRIs across the two VoIP gateways.