3CX phone over VPN

[IT-IMC]

Hello,

I was already searching the forum for this issue, I noticed similar issues were reported before but I could not get the solution yet.... 3CX Phone for windows (latest version) works perfectly fine while inside the local network, but it wont work over L2TP VPN connection (zyxell firewall). I run firewall checker, results are all OK. I have static NAT enabled with 5060 and 5090 on my zyxel firewall. 3CX phone register over the L2TP VPN, says "on hook" and it dials a number no problem but no sounds is heard. If I dial *777 I can hear the central repeating what I said. If I however connect with SSTP VPN connection all is working perfectly (dialing, sound all is good).

I just cannot figure out why there is not sound with L2TP VPN (hosted on zyxel) and also how it is possible to have the *777 test to be successful but the sound is missing on the actual call.

3CX central is connected with PATTON device to PSTN network.

Any help appreciated. thank you!

 

[CentrexJ]

Try enabling the "PBX Delivers Audio" under the extensions properties.

 

[DSXVOICE]

See below. With an external call, only the SIP conversation traverses the VPN - unless you have PBX handles audio checked. However, that will increase the load on the VPN unnecessarily, so you might want to take the trouble to open up RTP ports on the local firewall.

 

[tratz]

why would you need to use a l2tp firewall. I would use the tunnel that's already builtin to the client.

--Tracy

 

[ian.watts]

DSXDATA's diagram does explain how SIP sets up and tears down the call by signaling the endpoints over each leg.. but for internal calls the audio streams are set up by SIP to pass to each other directly. Keeps the PBX out of the way when it doesn't need to be involved.

On the other hand, if external calls are also missing audio.. that's different. The PBX delivers the audio stream to your leg, and to the trunk on the other leg.

If external sounds fine but internal is missing audio, indeed tell the PBX to deliver audio.. it's a bummer it's by extension when you may have another device "in-office" on that extension.. a different 'problem' I guess.