[SR-Users] Kamailio not mdifying Contact in multi-homed setup

Hi All, I'm running into an issue, I'm not sure whether any of you seen this yourselves and resolved it. Please share some pointers. My network is: clients <--> Public IP(Kamailio/RTPProxy)10.1.128.11 <--> 10.1.128.34 (Freeswitch) The 200 OK response from Freeswitch (on the way back from called party to caller) to Kamailio is shown below. Notice the Contact header URI host part contains Freeswitch Private IP (10.1.128.34). Kamailio suppose to change that to Public IP before forwarding the 200 OK (copied below) to Caller in public domain. But, it's not. As a result, ACK from Caller is not reaching back to Kamailio. How did you or anybody out there using Kamailio resolve this problem? If needed, I can copy/paste my kamailio.cfg. SIP 200 OK -> Via: SIP/2.0/UDP 10.1.128.11;branch=z9hG4bKa7ea.4013d9881c1b7fe7b4c6c0f0e8f9d6b6.0 Via: SIP/2.0/UDP <Caller Public IP>:5060;rport=5060;branch=z9hG4bK-383736-9b4621118533d3ccea17992738433249 Record-Route: <sip:10.1.128.11;r2=on;lr=on;ftag=791b5ae3;nat=yes> Record-Route: <sip:<Kamailio Pub IP>;r2=on;lr=on;ftag=791b5ae3;nat=yes> From: \"Dipak Biswas\" <sip:dipak.biswas@<Kamailio Pub IP>>;tag=791b5ae3 To: <sip:dipak.biswas.test2@<Kamailio Pub IP>>;tag=atXF5443gQj9p Call-ID: 20d5d6d366fcb06c259a0895b3e44b52@0:0:0:0:0:0:0:0 CSeq: 2 INVITE Contact: <sip:dipak.biswas.test2@10.1.128.34:5060;transport=udp> User-Agent: FreeSWITCH mod_sofia/1.4.2+git~20140108T200418Z~d8fc8469b4~64bit Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, MESSAGE, INFO, UPDATE, REGISTER, REFER, NOTIFY Supported: timer, precondition, path, replaces Allow-Events: talk, hold, conference, refer Content-Type: application/sdp Content-Disposition: session Content-Length: 269 -- Thanks, Dipak