I run a small ISP and have my customers all NATed behind one public IP. I am testing VOIPo reseller service before rolling it out to my customers and running into problems with incoming calls going directly to voicemail or ringing but no audio or one way audio when answered.

I have read some forum posts that suggest forwarding a huge range of ports to the ATA. Obviously this will not work for my network configuration. Is it possible to get your service to work reliably without doing this?

I have been using HT286es with their default configuration. I do also have one VOIPo rt31P2 that I'm going to swap in tonight to test. I will also test assigning a public IP directly to the ATA to see if I can prove that it is the NAT causing the problem. I have tried turning on STUN using the voipo server, but that did not help.

I'm looking for any suggestions on how to get this working without having to allocate one public IP per ATA. I don't have enough IPs to do this in a production environment.