Hello,

I am running Kamailio behind NAT.

Kanailio has a private IP and I am relaying NAT to internet router.

I am using:

- #!define WITH_NAT
- listen=udp:PRIVATE-IP:5060 advertise PUBLIC-IP:5060

- Patched RTP proxy including the advertise option

And everything goes fine. I can make calls and have two way audio.

The problem begins when the callee ends the call. BYE is not received in Kamailio (caller)

I included the public IP using "add_contact_alias" because "set_contact_alias" was not adding the public IP. I included this in in NATDETECT (pre loaded router)

        if(is_first_hop()) {
            xlog("L_NOTICE","Metodo: $rm \n");
            xlog("L_NOTICE","is first hop\n");
            #set_contact_alias();
                 if (!add_contact_alias("PUBLIC-IP", "$Rp", "udp")) {
                 xlog("L_ERR", "Error in aliasing contact $ct\n");
                    send_reply("400", "Bad request");
                            exit;
                    }
        }

I think the problem is related to destination that BYE is sent by the vendor. From what I see IP and port is taken from advertised in contact (PUBLIC-IP and 5060).
The problem is that internet router changes the source port.

Contact: <sip:999999999@PRIVATE-IP:5060;alias=PUBLIC-IP~5060~1>

--- Is it correcto to add_contact_alias("PUBLIC-IP", "$Rp", "udp") in order to received new transactions or should I follow a different procedure???

Thank you