One-Way Audio With VOIP Adapter

I bought a Linksys PAP2T-NA adapter and set it up with sipgate.co.uk I managed to call the test number 10000 and I can hear the message fine. I can also call the number I have been assigned and the phone rings and I can pick it up and hear the caller. The problem is that I cannot be heard by the caller, there is no outbound audio. I have tried loads of different combinations of ports and set up port forwarding. I have also tried putting the adapter into a DMZ from my router. I have tried different phones and still got nowhere. I then decided that maybe the adapter was no good so bought a Cisco SPA112, I've just set that up this morning and am in exactly the same situation, all fine except no outbound audio.

It seems to me that my router is probably the source of my problems, I have a Buffalo WBMR-HP-G300H and have spoken to Buffalo about turning off the firewall which they say you cannot do. I have tried to bypass the firewall by using a DMZ and that doesn't fix the problem.

My ISP is PlusNet if that makes any difference. I have tried setting the STUN server on both devices.

Any suggestions on how to get this to work?

http://www.voip-info.org/wiki/view/One-way+Audio suggests packet sniffing to see what's going on.

I would also try a router where you can disable the firewall to demonstrate where the problem lies.

I seem to have solved the problem by upgrading to DD-WRT firmware on my router, the VOIP adapter now works without any port forwarding required.

If memory serves DD-WRT has the SIP Proxy component, which I believe is ON by default - this'll be why Port Forwarding isn't needed, the ALG is taking care of it.

Be careful though as the ALG *may* cause random issues - especially if you have more than one handset on your network...