Hi! Another problem with NAT... I hope I will solve it soon! My rtpproxy is running and ser can connect to the rtpproxy. I can make calls to users that are connected to the ser server behind a NAT (Restricted Cone NAT and symmetrical NAT). That's working fine!!! Thanks for your help!!! But I have the problem that if I want to call to a Cisco PSTN-Gateway, that I can establish the call... but I don't hear anything. The callee is hearing me. What is the difference between an internal user and the Gatway?? The routing for Gateway and Users is almost equal (the only difference is the "P-hint: GATEWAY"). And: I'm wondering why the communication is OK with a symmetrical NAT (Linksys) and WITHOUT rtpproxy. If I turn on the rtpproxy (with symetrical NAT) the voice stream of the Gateway isn't arriving anymore. Any ideas? Thanks! Sebastian