We want to use the PBX on one of our servers. We have a fixed external IP. The server is linked thru 192.168.0.2 to a router. Outgoing and ingoing calls work fine but we have can not hear the external sound. Checking packet sniffer logs and talking to our provider, this is due to a problem with 3CX "INVITE" message: INVITE sip:firstname.lastname@example.org:5060 SIP/2.0 Via: SIP/2.0/UDP 192.168.0.2:5060;branch=z9hG4bK-d8754z-56101939c132c37e-1---d8754z-;rport Max-Forwards: 70 Contact: <sip:email@example.com:5060> To: <sip:firstname.lastname@example.org:5060> From: "910060"<sip:email@example.com:5060>;tag=4e4a3e12 Call-ID: OTZjNTg0NmUxMjFlNTk2ZmM5ZmNhYjUwODg3ZDEzN2Q. CSeq: 1 INVITE Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REGISTER, SUBSCRIBE, NOTIFY, REFER, INFO Content-Type: application/sdp User-Agent: 3CXPhoneSystem 8.0.9481.0 Content-Length: 274 v=0 o=3cxPS 537542000640 314405027841 IN IP4 192.168.0.2 s=3cxPS Audio call c=IN IP4 192.168.0.2 Instead of 192.168.0.2 it should send the global IP address 18.104.22.168 so the provider can send back SDP to the correct IP. We have not found any parameter to adjust this. Anybody knows about it?