[Users] test openser behind NAT not work

Dear All i will setup openser behind NAT like these OPENSER ---> ADSL ROUTER(A) <---> INTERNET <---> ADSL ROUTER(B)<-- UAC(1) <-- UAC(2) for UAC to talk each others in the same network with OPENSER server and try to REGISTER AND INVITE IT OK . but if i use UACs that located behind ADSL ROUTER(B) for REGISTER it OK when UAC(1) INVITE UAC(2) it RING and session established can heard sound but after about 30 second the CALLEE UAC(2) is HANG UP while CALLER UAC(1) still show established i saw some mail said that the problem may occour from ADSL ROUTER ITSELF (AGL problem)or some say that ACK problem. if i connect UAC(1) and UAC(2) through ADSL ROUTER(B) to iptel.org and i use UAC(1) INVITE UAC(2) it work no problem for 30 second disconnection . also if i use UAC(1) and UAC(2) conect to iptel.org through ADSL ROUTER(A) no problem . AT this point can I CONCLUDE THAT BOTH ADSL ROUTER NO PROBLEM FOR SIP CONNECTION. is it TRUE ?? Next i saw from LOG file it seem no ACK MESSAGE and error like these -- LOG FILE ------------- ERROR: tcp_blocking_connect: poll error: flags 18 ERROR: tcp_blocking_connect: SO_ERROR (111) Connection refused ERROR: tcpconn_connect: tcp_blocking_connect failed ERROR: tcp_send: connect failed --- for simply NAT testing i use openser.cfg like these ---------- OPENSER.CFG --------- if (!method=="REGISTER") record_route(); if (loose_route()) { # mark routing logic in request append_hf("P-hint: rr-enforced\r\n"); route(1); }; if (!uri==myself) { # mark routing logic in request append_hf("P-hint: outbound\r\n"); route(1); }; if (uri==myself) { if (method=="REGISTER") { if (!www_authorize("infowavenet.com", "subscriber")) { www_challenge("infowavenet.com", "0"); exit; }; fix_nated_register(); save("location"); exec_msg("cat >> /tmp/test"); exit; }; lookup("aliases"); if (!uri==myself) { append_hf("P-hint: outbound alias\r\n"); route(1); }; # native SIP destinations are handled using our USRLOC DB if (!lookup("location")) { sl_send_reply("404", "Not Found"); exit; }; append_hf("P-hint: usrloc applied\r\n"); }; route(1); } route[1] { # send it out now; use stateful forwarding as it works reliably # even for UDP2TCP fix_nated_contact(); if(method == "INVITE") { fix_nated_sdp("3"); } if (!t_relay()) { sl_reply_error(); } else { exec_msg("cat >> /tmp/test");} exit; } ------------ MY QUESTION: 1) can openser server is BEHIND NAT ADSL ROUTER and receive Call from UAC from other NAT ROUTER . 2) if so what the problem that CALLEE HANGUP every 30 seconds ( i use XLITE v.3 for UAC ) 3) if it possible can you fix openser.cfg that work for this situation Best Somsak Vattanavakin