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New Contributor

SBC w/ Multiple SIP Trunks

Hey All,

I've perused the site for the last couple of weeks and I am now getting into the actual programming of a 3140. I've ran into a few snags.

We're looking to deploy a 3140 as an edge device for one of customers in their data center. Currently the PBX registers to a SIP provider through their data network. Lately their current edge device has been causing various audio issues. Thus we decided to deploy the Adtran. Running a SBC seemed logical as a way to normalize SIP traffic. The thought was - SIP Provider <-SIP Trunk-> 3140 <-SIP Trunk-> PBX , all phones and devices register with the PBX locally. I think we would call this a back to back user agent setup. The issue I'm running into is that the PBX currently has 6 distinct SIP trunks. All with same provider but each with varying amounts of call paths and each with different DIDs etc, this was done to allow each trunk on outbound from the PBX to set a main outbound caller ID number.

My question is if we want to keep the multiple trunks I'd have to register 6 trunks to the WAN of the Adtran and 6 trunks the LAN of the Adtran. How do I program the 3140 to say 'this call comes in on trunk x publicly, send it down trunk x locally" and "this outbound call from PBX trunk x must call out on trunk x WAN side". We are also looking at perhaps the transparent proxy of the 3140.

Any and all advice and guidance is greatly appreciated!

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Honored Contributor
Honored Contributor

Re: SBC w/ Multiple SIP Trunks

You will need to create a voice trunk for each SIP server on the outside. One voice trunk to the PBX. Configure the voice grouped-trunk feature to prioritize the trunks in therms of "cost" for outbound calls in the order you want as well as which outbound dial patterns should go out which trunk. In the voice trunk configuration you can specify the maximum number of calls for capacity. If different originating numbers (ANI) from the PBX are supposed to go out different trunks, the SABR feature can handle this. Don't forget to configure emergency and service numbers (9-1-1, 4-1-1, etc.) to use the appropriate trunk.

Totally configurable and workable. You're moving the call selection process from the PBX to the 3140. Only one trunk out from the PBX to the 3140 and let the 3140 route it.

I strongly recommend that you use specific dial patterns rather than the generic "$" for the grouped-trunk accept patterns. Also ensure that the provider trunks are blocked by SABR from routing calls to each other. You don't want to provide transit from one SIP provider to another for calls that don't terminate on the PBX due to accident or fraud.

Re: SBC w/ Multiple SIP Trunks

Thanks for the quick response.

The PBX sets the outgoing caller ID based on what outgoing line group it uses and the outgoing line group is basically the trunk. Moving the call selection process as you say from PBX to Netvanta would be a larger undertaking than what I think we want to try. Have you any experience with the the SIP Proxy or Transparent features of the AOS? More than anything we just need an edge device that will not screw up SIP packets as the current device does.

Honored Contributor
Honored Contributor

Re: SBC w/ Multiple SIP Trunks

Transparent proxy might work, but I suspect not. It's typically for individual phones that each register a single DID.

You'll find that the Adtran 3140 is quite capable of pretty much anything you throw at it from a call routing standpoint, including manipulating outbound CLID per trunk.