Voice dropping on calls via VPN

[staffop]

I'm seeing a few problems with audio in certain directions on calls made from or to extensions over a VPN.
Running 3CX version 12 with Yealink T46G on both ends. VPN is setup using a Draytek Vigor 2860 at the server end and Vigor 2830 at the remote end, both are on 50-70MB cable broadband connections with average/low usage.
I've enabled the 'PBX delivers Audio' option in the 3CX 'Other' options on the Extension Capabilities section of the phone extension.
Generally the problem will be we can hear the caller at the server end but the remote user cannot hear us.
Would this be a QoS issue or something else (QoS is not enabled).

 

[GiannosC_3CX]

Hi staffop,

Generally the problem will be we can hear the caller at the server end but the remote user cannot hear us.

This seems that your phones has different subnet. Please make sure the port forwarding rules are applied correctly on your firewall. Please note the delivery audio ports on internal calls are 7000-7500 ( as destination to the PBX and when the call is initiated from the PBX then this is the source port range ) and on external calls are 9000-9255 ( in case you make external calls to Provider or to extensions that are on Public ip addresses ). Also, please ensure the SIP-ALG is disabled.
In case if you need more information please visit this link https://www.3cx.com/blog/docs/draytek-firewall-voip/ (Only with telnet)

 

[staffop]

Hi staffop,
This seems that your phones has different subnet. Please make sure the port forwarding rules are applied correctly on your firewall. Please note the delivery audio ports on internal calls are 7000-7500 ( as destination to the PBX and when the call is initiated from the PBX then this is the source port range ) and on external calls are 9000-9255 ( in case you make external calls to Provider or to extensions that are on Public ip addresses ). Also, please ensure the SIP-ALG is disabled.
In case if you need more information please visit this link https://www.3cx.com/blog/docs/draytek-firewall-voip/ (Only with telnet)

The ports open on the router at the PBX end are 5000, 5060, 5090 & 9000-9500. None are open on the router at the remote end of the VPN. Note that we have several VPN connections between PBX & remote locations and they are all the same with no ports open on remote ends. The PBX end uses 192.168.0.X subnet and remote ends vary between 192.168.2.X - 192.168.6.X
I've checked and SIP-ALG is disabled on all routers.
Not all the VPNs exhibit the same problem which is odd so wondering if it is more of a QoS issue?

 

[GiannosC_3CX]

Hi staffop,

I have sent you a p.m.