Me again... this time VOIP

dl763 · 22 May 2009 at 15:13

Hi all,

We've got a client with a VPN between two Draytek 2820 routers. He has got VOIP going across the connection but can only get one way voice, data is fine.

I believe this is a problem with NAT? We were advised to open ports so it could get to the VOIP system (Panasonic something or other) which we did but it hasnt helped.

Anyone got any ideas? Would putting the VOIP switch on the DMZ help?

TIA

Jon

ZuG · 24 May 2009 at 09:25

I am not sure putting into the DMZ would help. One way traffic is caused from one side not being able to send RTP packets to the other side. Your SIP is working correctly, but the audio is sent over RTP. You will need to find out which RTP ports the Panasonic VoIP System uses and make sure the traffic can get through. A packet capture would really help diagnose this.

m4cc45 · 24 May 2009 at 09:29

Traffic has to be bi-directional as well so if you have only opened one side this could be the problem.

M.

dl763 · 26 May 2009 at 08:16

Thanks guys,

I opened ports on both routers as advised by our phone tech support people. I'll try the RTP method.

iaind · 26 May 2009 at 14:15

Generally draytek VPNs arent firewalled and they shouldnt be doing any NAT, so neither of those things will be your problem

dl763 · 26 May 2009 at 14:43

So I shouldnt need to open any ports? Apparently it improved when I opened ports 5004 to 5011 which are the RTP ports.

This is doing my head in now, it's been going on for nearly a week!

m4cc45 · 27 May 2009 at 18:30

Well the draytek model you mention does have a firewall and the fact you opened the ports and its better suggests it is a firewall issue.

If the ports are closed then they need to be opened.

I guess either one of your firewall rules is incorrect or you're missing some rules. If you have some spare hardware you could lab it up and then disable the firewall to see if this makes it better if it does then you know, with 100% certainty, its the firewall and all you need to do is find the ports.

M.

iaind · 28 May 2009 at 07:51

With most of these when you configure a VPN it considers the other subnet as part of it's internal range - new models may be different though

dl763 · 28 May 2009 at 08:11

If I put the Panasonic into the DMZ that would bypass the firewall wouldnt it?

ZuG · 28 May 2009 at 20:35

possibly, however it shouldnt make much difference if it's over a VPN... When you said it was better, what did you mean? Surely you can hear them or your can't...

dl763 · 29 May 2009 at 08:17

The client could here more than nothing but not much more...

ZuG · 29 May 2009 at 22:05

if it was a ports/firewall issue then they would not hear anything at all at one end. It maybe something else completely....

s0ck · 30 May 2009 at 02:41

Does sound like a NAT issue. Have no idea about the Panasonic PBX though, usually have to define the LAN ranges and as well as the EXTERNIPs, otherwise the SIP header packets carry the wrong info. It's been a while since I played with it though.

dl763 · 1 Jun 2009 at 08:59

I'm thinking it could be a fubard router now. Is it possible one of the routers could just need resetting to factory settings?