[Freeswitch-users] using public IP and Port versus sdp port

I have a server sitting on a public IP and all endpoints are behind routers. In some cases I get rtp where the sdp port differs from the received port. The freeswitch picks up the public ip to route to but uses the sdp port to route the rtp back to versus the public port, anyone have any suggestions. I believe I corrected this on another server awhile back but cannot remember the setting. Thanks Darcy