I hope someone can help me with this one and I will be most grateful for any advice.
We have a freepbx box running and it handles a SIP trunk connected to SIP provider (Gamma) and has incoming routes for various DID’s and handles all outbound traffic.
To make use of the current SIP trunks and free calls attached to the PBX we would like to interface a NEC PBX onto this asterisk box via SIP trunks. All we be able to dial out from the NEC, through asterisk and thus the asterisk would need to route the call out through the Gamma SIP trunks. Inbound calls will need to come in through the Gamma SIP trunks, through asterisk and then trough these internal Sip trunk to the NEC.
It all depends on the NEC PBX. Certainly doable with Asterisk, but you will have to check what specific SIP capabilities does the NEC have. You will probably need a license for SIP trunking on the NEC if you don’t have one already. Are you trying to keep the NEC for a particular reason? Why not go all in with Asterisk?
Thanks for your reply, I am most grateful. Sorry I should have explained the situation a little better. We have a Freepbx running in a cloud enviroment with plenty of SIP trunks on it for external traffic. We also have a few seperate sites with new NEC PBX’s which currently have SIP trunks attached. What we would like to do is run all this traffic through the freepbx so that we can utilise the trunks we have on there and thus enjoy cost savings by getting rid of the SIP trunks on the other NEC systems. The NEC systems will essentially sit after the Freepbx, they do not need to communicate with the exception of being able to route through the FreePBX to the external SIP trunks. The other benefit is that all our numbers sit on the one SIP trunk meaning we have better control should nay issues arise.
Essentially what I am looking for is to be able to use the FreePBX as a SIP trunk provider I guess.
What you are trying to accomplish is perfectly doable, but Asterisk might not be the best choice, as it is a B2BUA and what you would need in this scenario is a SIP Proxy.
For a large system, I agree with @arielgrin , but if your FreePBX has enough resources to handle the additional traffic, it’s much simpler to set up your inter-site trunks on the PBX.
Simplest, (and best if the branch offices don’t have static IP addresses) is for the NECs to register and authenticate to FreePBX. For a pjsip trunk, set Registration Receive and Authentication Inbound. For chan_sip, use host=dynamic. If the branch offices are permitted unrestricted access and use the same number formats, just set the intra-company trunk context to from-internal and you should be good to go.
However, there are lots of subtleties; provide details if you want to pursue this further.