[OpenSER-Users] Strange REGISTER problem

Hi, I am experiencing a very strange problem with REGISTER. If my SIP client registers to Openser with openser's internal IP ( 192.168.1.104), then it works. But if the SIP client registers using Openser's public IP, it does not work. The 200K returned from Openser is different for each case. For the 1st case, my SIP client recognizes the 200 OK, but for the 2nd case, my SIP client will keep on sending another REGISTER upon receiving the 200 OK. Here are the two different 200 OK msg that Openser sends back to the client. U 192.168.1.104:5060 -> 192.168.1.100:44522 SIP/2.0 200 OK. Via: SIP/2.0/UDP 192.168.1.100:44522 ;branch=z9hG4bK-d87543-7e47d706ec23b831-1--d87543-;rport=44522. To: "1006"<sip:1006@192.168.1.104 &lt;sip%3A1006(a)192.168.1.104&gt; From: "1006"<sip:1006@192.168.1.104 &lt;sip%3A1006(a)192.168.1.104&gt; Call-ID: MGYyMjczODBmNTRkMzA3Y2JmZjk4ODM0MjkxOWI5ZDQ.. CSeq: 2 REGISTER. Contact: <sip:1006@192.168.1.100:16728;rinstance=d380362012deaf00>;expires=1909, <sip:1006@192.168.1.100:16727;rinstance=94567af350ff0cad>;expires=1870, <sip:1006@192.168.1.100:25572;rinstance=57a835af07252a9e>;expires=3286, < U 192.168.1.104:5060 -> 78.251.75.157:16156 SIP/2.0 200 OK. Via: SIP/2.0/UDP 192.168.1.100:2388 ;branch=z9hG4bK-d87543-f0701c5a1050361a-1--d87543-;rport=16156;received= 78.251.75.157. To: "1006"<sip:1006@58.251.75.157 &lt;sip%3A1006(a)58.251.75.157&gt; From: "1006"<sip:1006@58.251.75.157 &lt;sip%3A1006(a)58.251.75.157&gt; Call-ID: ZDVjODBlMjAxODQ5ZjAxYTRkYzRjYzUxMjY3YzAxNjk.. CSeq: 2 REGISTER. Contact: <sip:1006@192.168.1.100:16728;rinstance=d380362012deaf00>;expires=1493, <sip:1006@192.168.1.100:16727;rinstance=94567af350ff0cad>;expires=1454, <sip:1006@192.168.1.100:25572;rinstance=57a835af072 Any help will be greatly appreciated. Thanks, Mark