[Freeswitch-users] NAT'd FS / publice softphone problems

Hi All, I know this question has come up before but I couldn't find the answer that I could understand! Sorry in advance. My setup is: Freeswtch NAT'd (192.168.x.x) -> Router -> Internet -> Softphone with public IP I can easily get the softphones to register, but when I try to call from the softphone to voicemail (for example), I don't get any audio. I checked out this page: http://wiki.freeswitch.org/wiki/External_profile (section Switch with External SoftPhone) but I am not clear how I can get this to work. I have played around with the rtp-ip and external-rtp-ip but without success. Is it possible for someone to help me configure this so softphones that are outside the nat'd lan get audio correctly? Help appreciated! Thanks