[Kamailio-Users] Openser and Asterisk Configuration problem

Hi everybody, so, I'm tryng to use Openser and Asterisk toghether in this scenario: Ser and Asterisk are in the same LAN 10.2.7.X, and they are both behind a firewall. SER can be reached from the outside network via a Public IP forwarded to it, Asterisck can only be reached from Ser, and it cannot reach the ouside network. I'm using Ser as proxy and registrar, all requests are forwarded to Asteisk by the proxy. In this way I can use all the feature of Asterisk. Users can regiser to Ser both via the private LAN and the public IP , so I have to distinguish from where calls are coming from in order to properly initialize rtpproxy. IF a client is registered from the outsie and it has a Public IP, rtpproxy is not called and the Asterisk try to send the media directly to it, but since asterisk cannot reach the outside network, no media is passed. How can I fix this? Thanks in advance for any hints, Cosimo