[OpenSIPStack] OpenSBC behind NAT/router

[Roland A. <fo...@op...>]

Hi all,

I have a bit of a tricky problem and am not sure if OpenSBC can handle this setup. The network config is as follows

Office:                            Office                                       Home
SBC (10.17.20.4) <------> Router/NAT <---public internet--> Router/NAT <------> SIPPhone

Now the office NAT has port forwarding rules to send the SIP traffic to the SBC. The SIPPhone can send the invite to the SBC which internally forwards it to a voice service. The SBC sends back the 200 OK and ACK follows. So the SIP sginalling works, but the SDP offer/answer is not quite right.

Obvioulsy the SDP in the invite has the wrong (sipphone-local) ip address. The SBc should be able to correct that. But the SDP answer from the SBC also shows it's internal IP address(10.17.20.4). 

Now the question i have is if it is possible to configure the SBC to use the public ip address in the SDP. Furthermore, i'd like to know if it is possible to configure a port-range for the RTP traffic so that i can put some forwarding onto the NAT/router.

A last question would be, whether i'm able to get this setup to work?

does somebody have some experience or give some advice?

cheers

roland