[Users] "BYE" messages change path

Hi Users, I am using SER-0.9.6 on public domain . and I am using another Sip-proxy behind NAT (ip-address=192.168.1.100:5060) i have some clients registered to that nated sip-proxy and here that nated sip-proxy forwards PSTN calls to SER on public domain. when call make from client (registered to nated sip-proxy) the session establishing suscessfully , but when the client hung the phone the SER on public domain is taking the BYE message and is not sending the BYE message to the other end and it is sending directly to the Sip-proxy which is a private-ip . So, here SER is not getting ACK and its keep on sending the BYE requests to the privateip instead of sending to the NAT address . In some docs which jiri wrote on record route he mentioned the same problem below is the link ; but he dint mention how to solve that record route problem, If SER send messages back as it recieving path (from NAT)there is no problem , but its changing the route to send BYE , For the request "CANCEL","ACK","INVITE","200 OK" every thing is happening in the same Route but it is not happening only for the "BYE" request . Hope some body can help me. Thank You. here is the link which i told;-http://216.239.59.104/search?q=cache:A32Unl9P0hkJ:voip.internet2.edu/… Regards, Ravi.