Perhaps you do fix_nated_contact() in k1, which should not be done, because k1 is not the first hop from ua2. Cheers, Daniel On 13/12/13 02:22, dolphin wrote: hello, I’m trying to build two kamailio-3.3.4 server like this: ua1 ----> kamailio1(k1)-----> kamailio2(k2) -----> ua2 ua1 (5978003 ) is register k1 ua2 (5001005) is register k2 When ua1 callout to ua2 sip process through k1 and k2 The problem is k2 server ACK not transfer to ua2 and k2 has received ack signals from u1 through k1 I ngrep sip process for k2 and k2 /var/log/debug see the attached File ngrep_k2server.txt, debug_k2 1. First ACK uri have ua2 number sip:5001005@xxx.xxx.xxx.xxx(k2):5003;ob , is correct !! 2. Second ack not include 5001005 , again loop itself ; Route: <sip:xxx.xxx.xxx.xxx(k2):5003;lr;did=763.941> loose_route Next hop: 'sip:xxx.xxx.xxx.xxx(k2):5003;lr;did=763.941' is loose router. so next hop Not found in usrloc db 5001005 user and not transfer to ua2 How to fix this problem, any suggestions ? _______________________________________________ SIP Express Router (SER) and Kamailio (OpenSER) - sr-users mailing listsr-users@lists.sip-router.orghttp://lists.sip-router.org/cgi-bin/mailman/listinfo/sr-users -- Daniel-Constantin Mierla - http://www.asipto.comhttp://twitter.com/#!/miconda - http://www.linkedin.com/in/miconda