voip over vpn tunnel

[malcolm115]

hi long question I have 5 vpn tunnels using zyxel routers that are all voip working fine to the office but when you try to connect to any of the off site ip telephones it rings answers but you get no voice all though the phones are seem connected

 

[robl3000]

Something is misconfigured in the VPNs. There are 2 parts of VoIP calls, signaling and the audio stream. If you have signaling, you can get the ringing. However, something is blocking the audio streams on the VPNs and firewalls.

Does the problem exist for all 5 sites? Or only a portion of them?

 

[malcolm115]

all the same except when calling the office they work when you call the office

 

[robl3000]

It definitely sounds like a VPN problem. I had similar issues for some remote phones and it ended up being a problem with the way I setup the VPN. The VPN is not passing the RTP (audio) stream.

Unfortunately, I am not familiar with Zyxel VPNs. We used OpenVPN for our remote locations.

 

[bluemr2]

The problem is the packets can't go from 1 vpn to another. When a call is set up the packets go from the IP phone to the BCM. No problem in your case. Once the call is answered the BCM drops out of the equation and packets just route from IP phone to IP phone which your setup can't do correctly.

 

[robl3000]

bluemr2: correct. A route between each site to the other sites needs to exist in the VPN. Having a routes just from a remote site to the centra site is not sufficient. All 5 VPNs must know about the remaining 4 LANs.

 

[malcolm115]

thanks guys I needed to set up an extra vpn tunnel to the remote site it all works fine now