[SR-Users] Regrading Kamailio

Hello Kamailio Team, I am using kamailio server successfully for some time now. I have a specific set of problem. We have a Kamailio Server setup in Amazon EC2 Cloud, the users are able to register on the server and make use of this. *Now the problem:* If I am trying to register multiple SIP clients from same Public_IP:Private_IP (i.e. alice and bob from same computer) on a kamailio server which is sitting behind Amazon EC2 Cloud Based Server, then only the first user (who sends REGISTER packet first) is able to register successfully on the server and all the other users after the first one are not able to register on the server. Am I missing something in the configuration file such that this is happening. Please help in this regard. Waiting in anticipation Thanks & Best Regards Saurabh Srivastava