We have same VoIP provider in two cities. Provider is absolutely inflexible of making any changes. We have VPN connections between locations. Imagine this situation for example.
My PBX on 172.16.16.200 (PBX is behind NAT).
IP assigned by our provider for our PBX at first location is 172.16.1.70/30
IP assigned by our provider for our PBX at second location is 172.16.9.242/30
Provider's VoIP server on 172.16.0.18 (sip.provider.com)
Provider does not allow us to connect SIP trunk from first location on second one, and vice versa.
My idea is to use only one server for both SIP trunk.
I think I could force second trunk to go to different IP (172.16.0.20 for example). Since the server is behind NAT, I would need to change source, and destination IP in a rule. Do you think it is possible to do that, or maybe someone has another solution?
Basically, same PBX, same VoIP server, but different routes.