Having trouble with externalip

I am trying to get a home asterisk server set up with a sip trunk group that i will use for LD. The server is behind a firewall. Calls between UAs in my local network work fine. I am able to set up calls on the external sip trunk group but no sound.

Obviously some sort of NAT issue.

Sniffing the packets on the external side of the router, i can see that the SDP portion in the SIP invite is using the internal 192.168.x.x address and not the external one that i have specified. I suspect this is why i never get RTP back.

in the [general] section of sip.conf i have:

externalip=(my external ip, at least for now)

and also
nat=yes (but i think this has more to do with how asterisk responds to invites then how it initiates calls)

shouldnt that be enough?

Have you tried opening up ports 10,000-20,000 on routers firewall or port forward those ports to the server ?

Also try ‘nat=force_rport,comedia’ if your running 1.8 or later.

try with media_address=“your ext ip”.