Internal Calls Drop out for a few seconds

[jmp28]

I am getting the following issue.
2 Sites which have their own internet connection but are connected to each other by a site to site SSL VPN tunnel using Sophos XG firewalls at each site.
3CX is hosted in 3CX Cloud.
Handsets are Yealink SIP-T53W.
If a staff member at one site calls another staff member at the other site, the call connects but they are randomly experiencing a 5 second dropout where each user cannot hear the other, then it comes back. The call does not disconnect. It does not happen if they call an external number.
The SIP module is turned off on both devices.
The interesting part is that we recently setup the Sophos firewall and VPN tunnel. Before that, they operated from another office without a firewall or VPN tunnel and never experienced the issue.
Not sure what could be causing the issue and would really appreciate some feedback as to how to troubleshoot or what may be the cause.

 

[NicholasP_3CX]

This could be some routing issue on the firewalls between the sites. You mentioned that external calls do not face this, so try enabling PBX delivers audio on the extensions and see if that resolves the issue. That way you can be certain that it is something with the inter site routing of the sites.

 

[jmp28]

Thanks Nicholas. I have now enabled that on the handsets. Will monitor over the next few days and let you know if that resolves it.

 

[jmp28]

Hi Nicholas. Client has advised it is still an issue. My next step will be to temporarily disable the VPN and see how that affects the calls. If the issue disappears when the VPN is disabled, I will follow up with Sophos, unless you have some other ideas of what could be causing it.
John

 

[TheodorosG_3CX]

This is a network related issue, the call monitoring tool can also give you more information and point on which direction to troubleshoot:
• https://www.3cx.com/blog/docs/call-quality-tool/

 

[jmp28]

Thanks Theodore. I have now enabled that on the extensions in the remote office and will see what the results come back.

 

[TheodorosG_3CX]

This can show you more information and help you troubleshoot further,

 

[jmp28]

Thanks for your help. It looks like a Sophos issue so I have raised a ticket with Sophos.

 

[TheodorosG_3CX]

Good to know. Also you may share your feedback for other users in the forum is this is possible.