[OpenSIPS-Users] Should I change 'Contact' or 'Via' header fields, when UAC and proxy are behind a NAT?

Rodrigo Pimenta Carvalho pimenta at inatel.br
Mon Dec 28 15:17:26 CET 2015


I have OpenSIPS 2.2 and a softphone (S1) behind a NAT. The softphone is registered on such SIP proxy. Proxy and S1 are in the same local network.

There is another softphone (S2) located somewhere on Internet.

When S2 calls S1, S1 receives the SIP INVITE normally. When the call is answered S1 sends SIP 200 OK to S2. However, the 'Contact' header field in the SIP 200 OK message has an address not reachable by S2. Such address is valid only in the the local network. In this case, S2 doesn't send a SIP ACK to S1, probably due to that invalid address on the 'Contact' header field.

I suspect that I have to use a OpenSIPS module, related to NAT questions, and try to fix the value of 'Contact' header field. Am I correct?

I am not using any Stun server yet.

What should I do?

What about the 'Via' header fields? Should I fix it too, using the OpenSIPS?

Any hint will be very helpful, because I'm not expert in SIP.

Best regards.

Inatel Competence Center
Ph: +55 35 3471 9200 RAMAL 979
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