Redundant Voice Gateway Configuration - Possible?

Unanswered Question
Jun 1st, 2009


We are looking at installing a redundant gateway solution for one of our facilites. The existing PBX has a problem that could cause us to lose our ability to run a PRI. The thought was to bring each T1 PRI into two voice gateways. Those gateways would then connect with a T1 CAS to the PBX. One of the gateways will then have a T1 PRI to the PBX as well. We want the PRI for Caller-ID information. If the system fails, we want calls still able to flow.

T1 PRI1 --- GW1 --- T1 CAS1 --- PBX

T1 PRI2 --- GW2 --- T1 CAS2 --- PBX

GW2 --- T1 PRI3 --- PBX

We want the gateways setup in H.323 mode for call preservation. The problem I'm finding is this... I want all the calls going to the PBX to go down PRI3. In the event of a PBX failure, we want the calls to go down CAS1 or CAS2. If GW2 fails, we'd want to do the same thing.

Both GW1 and GW2 will have dial-peers built back to our Call Manager servers. (7.0)

Is what we're trying to acomplish possible?


I have this problem too.
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Nicholas Matthews Wed, 06/03/2009 - 18:33

This will be accomplished two different ways. For reference, let's say extension 1000 lives on the PBX.

On each of the 3 H323 gateways you would create 2 dial peers.

dial-peer voice 1 voip

destination-patter 1000

preference 1

session target ipv4

dial-peer voice 2 pots

destination-patter 1000

preference 2

port 0/0/0:0

You could make it more redundant in case one of the CAS circuits fail, and create a 3rd dial peer with the 2nd lowest preference and route it via voip like the first dial peer as well.

The other option is to have all of your dial peers for all of your routers point to CUCM. Then, in CUCM for the route pattern of 1000 you would point it to a Route List. This route list would contains 2 Router Groups. The first priority would be a Route Group containing the H323 gateway for GW3. The 2nd would contain both GW1 and GW3.

This would operate where it would send all calls to GW3, and if it fails, to load balance between 1+2.

Implications of using CUCM are that all the signaling will pass through CUCM but the media will not. It adds another step of complexity for the call flow, but may be easier for you to manage if you don't understand dial peers as well.

I'd go with the dial peer approach myself.



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