[SR-Users] Determine correct port in record-route if kamailio is behind NAT

[Michal Popovic]

Hello,

our kamailio used for sip trunk interconnections is behind NAT and our cloud provider opens random outgoing ports for outbound connections.
Our record-route is set to our external address and port 5060, that is probably incorrect, but we did not had any issues.
One of our partners suddenly begin sending BYEs to the port advertised in record-route instead of port from where he received call.

What is a correct approach here if we are not able to determine open port behind NAT?

Bye,
Michal