I have an install and am trying to get a remote extension working. I have the server on one subnet and the client on another, with all ports open. The client (softphone) registers and compltes calls, but no RTP Stream from the server makes it through.
You should actually read the forums here, yes many have that problem, there a plethora of answers and the wiki should also cover it well enough, but basically you have a network/PNAT/routing problem you need to resolve.
It was a routing issue. Didnt have the route set to forward to the remote subnet so thats why RTP streams were failing. Odd thing was that ICMP was working fine from the remote to the main, but not from the main to the remote. (which is how I figured out I had an issue.)