Using OpenSIPS
I have a local SIP proxy server that manages domain local-domain that has two users: alice@local-domain and bob@local-domain. There is also a cloud SIP proxy server that I want use to reach Alice and Bob when they're not in the local network (the cloud SIP proxy is used as "outbound proxy"). The local SIP proxy is behind NAT and I don't want to forward any ports.
An example scenario:
alice@local-domain registers themself to the local SIP proxy. bob@local-domain registers themself via the cloud SIP proxy since they are not in the local network. I want Alice to be able to call Bob (the other direction is less important).
How can I let the local SIP proxy set up a connection to the cloud SIP Proxy, so that the cloud SIP Proxy can forward any request to local-domain to the local SIP Proxy? Flexisip uses domain-registrations to accomplish this. But this does not seem to be something OpenSIPS supports?
I looked at OpenSIPS NAT Traversal Module, but this seems to be for user agents behind NAT, not proxy servers.
