Hello everyone,

I'm doing some custom Kamailio configuration to achieve few things but seem to be stuck with SIP trunks. I'm currently using Kamailio 4.4.5 and here is what I have at the moment:

1. Asterisk 11.25.1 servers behing Kamailio using RealTime for SIP peers.

2. Route that checks if packet was sent from one of configured SIP trunks. This part works correctly:

route[FROMPSTN] {

        xlog("== FROMPSTN ==\n");

        $var(socket) = $si + ":" + $sp;

        xlog("**** $var(socket)\n");

        xlog("**** $(sht(trunks_kamailio=>$var(socket)))\n");

        if ($(sht(trunks_kamailio=>$var(socket))) != $null) {

                xlog("**** From $(sht(trunks_kamailio=>$var(socket))) PSTN\n");

                return 1;

                }

        xlog("**** Not from PSTN\n");

        return -1;

}

3. Here is a fragment that sends INVITE packet to TOASTERISK route if it was received from one of trunks. I have 4444444444@XXX.XXX.XXX.XXX hardcoded for now, and in my configuration 4444444444 and XXX.XXX.XXX.XXX represent my real caller id number and carrier's IP address:

if(route(FROMPSTN)) {

        uac_replace_from("sip:4444444444@XXX.XXX.XXX.XXX");

        route(TOASTERISK);

}

4. TOASTERISK basically has folloving fragment that load balances traffic between Asterisk nodes:

if(!ds_select_dst("0", "4")) {

        xlog("**** Call was not sent to none of Asterisk hosts\n");

        if(!is_method("REGISTER")) {

                xlog("**** Method is not REGISTER\n");

                send_reply("404", "No destination");

        }

        xlog("**** Dispatcher fail\n");

        exit;

}

So when I'm making a call to my test number, I can see following incomming packet in Asterisk from Kamailio. From header has correct caller id number and carrier's IP address (192.168.88.5 is Kamailio's internal IP address):

And when Asterisk tries to find a maching peer for this incoming call, it is using Kamailio's instead of Carrier's IP address. So it is actually finds one of peers (101-XXXXXXX) that is being authenticated on Kamailio as many others:

I'm not sure if Asterisk is just using packet's source IP to lookup for corresponding peer or something else from it's content. I will really appreciate any help on this.

Thanks a lot!