[Serusers] NAT Issues (ACK & BYE sent to Private IP)

Hi All, How can i solve the issue of ACK and BYE being sent to private IP? i'm behind a DSL modem/router (siemens speedstream), when i register to the SIP server, the SIP server does not think that i'm behind a NAT. because on my config: if (method=="REGISTER") { if (nat_uac_test("19")) { xlog("L_INFO","%fu behind NAT"); fix_nated_register() xlog("L_INFO","%fu NATTED REGISTER FIXED"); force_rport() xlog("L_INFO","%fu rport forced"); }; xlog("L_INFO","%fu trying to register"); if (!www_authorize("mydomain.com", "subscriber")) { www_challenge("mydomain.com", "0"); break; }; xlog("L_INFO","%fu registered"); save("location"); break; }; i don't see on my log messages, the message if nat_uac_test returns true, i tried changing it to 23 then 31 and still nat_uac_test returns false. also i'm seeing that c IN= is already the public IP, but why is it that ACK and BYE are still sending it to the private IP? TIA Nhadie