I am trying to get my head around how to build out a Freeswitch box to sit between several FreePBX on-prem servers and a couple of SIP providers. Freeswitch will act as a B2BUA and provide call routing and fail-over.
I am having a mental block about how to think about the different elements here. I am stuck in the conceptual framework of a simple PBX/Trunk scenario and Freeswitch is generally geared towards a PBX concept also. But I know it is certainly capable of fulfilling the role I am looking for.
In my scenario - we have a Public and Private profile with the SIP providers on the Public side and the FreePBX boxes on the Private side - so far so good. The SIP providers are clearly gateways where we receive and route calls to/from the PSTN. But, are the FreePBX servers Extensions? Is an “Extension” just an endpoint for SIP UACs to register? That is where is all gets messy. It seems that I need a gateway that is also a registrar?