[SR-Users] SEMS with sbc application

Hello, I have a problem today, It's strange for me. Suppose we have this senario: uac1------->SEMS(mo profile)------->Kamailio-------->SEMS(mt profile)---------->uac2 In above topology, we have two interfaces(intern,extern) for SEMS, and just used as SBC (sbc application). if i used port=5060 as external port, every things is right and log file is like this: [#7fed3f9f9700/32820] [run, udp_trsp.cpp:352] DEBUG: vv M [|] u recvd msg via UDP from 89.165.117.125:42411 vv --++-- REGISTER sip:kava.shatel.ir;transport=UDP SIP/2.0 Via: SIP/2.0/UDP 89.165.117.125:42411;branch=z9hG4bK-d8754z-021bd8b61efc7ac0-1---d8754z- Max-Forwards: 70 Contact: <sip:4000@ 89.165.117.125:42411;rinstance=79011092e56e1a09;transport=UDP> To: <sip:4000@kava.shatel.ir;transport=UDP> From: <sip:4000@kava.shatel.ir;transport=UDP>;tag=82820e1f Call-ID: Y2U4YThiYjEwNTUzMzliZTIwNWZkMDI3MTM4OTZlNWU. CSeq: 2 REGISTER Expires: 3600 Allow: INVITE, ACK, CANCEL, BYE, NOTIFY, REFER, MESSAGE, OPTIONS, INFO, SUBSCRIBE Supported: replaces, norefersub, extended-refer, timer, X-cisco-serviceuri User-Agent: Z 3.3.25608 r25552 Allow-Events: presence, kpml Content-Length: 0 but when i changed port=4080 for external port, The Via header and contact header are changed to my public ip, like this: [#7fed3f9f9700/32820] [run, udp_trsp.cpp:352] DEBUG: vv M [|] u recvd msg via UDP from 89.165.117.125:42411 vv --++-- REGISTER sip:kava.shatel.ir;transport=UDP SIP/2.0 Via: SIP/2.0/UDP 172.1.1.125:42411;branch=z9hG4bK-d8754z-021bd8b61efc7ac0-1---d8754z- Max-Forwards: 70 Contact: <sip:4000@172.1.1.125:42411;rinstance=79011092e56e1a09;transport=UDP> To: <sip:4000@kava.shatel.ir;transport=UDP> From: <sip:4000@kava.shatel.ir;transport=UDP>;tag=82820e1f Call-ID: Y2U4YThiYjEwNTUzMzliZTIwNWZkMDI3MTM4OTZlNWU. CSeq: 2 REGISTER Expires: 3600 Allow: INVITE, ACK, CANCEL, BYE, NOTIFY, REFER, MESSAGE, OPTIONS, INFO, SUBSCRIBE Supported: replaces, norefersub, extended-refer, timer, X-cisco-serviceuri User-Agent: Z 3.3.25608 r25552 Allow-Events: presence, kpml Content-Length: 0 Why my public ip address is there here? I just changed external port=4080 in sems server. In SDP protocol i have the same problem when i changed external ip port in sems server. Thanks. --Mojtaba Esfandiari.S