Random audio holes with hosted by 3cx pbx and sbc

[M.Zanetti]

Hello,
I'm experiencing a problem on my 1st hosted by 3cx setup.
We've a Professional V16 3cx and 2 remote location connected by SBC (both Windows 16.2.24), at the 1st office there are 9 phones (7 Fanvil X5U and 2 X6U), and at the second there are 3 phones (Fanvil X5U). All phones are updated to latest firmware version (v.2.4.11) and provisioned with latest official 3cx template.
Both remote offices complains that randomly during external calls (both inbound and outbound) happens some 1-2 seconds "audio holes" of remote voice: external caller is always able to listen. After that 1-2" hole, voice came back and phone call can continue, but sometimes can happen another similar hole for 1-2".
Normally this happens after about 2-3 minutes of regular calling.
I've tried change internet connectivity (first office with 9 phones have a failover wan link), as well as setting G729 codec instead of G711, but nothing changed.
I've tried enabiling a Wireshark capture on pbx, while reproducing problem, but I was able to listen both audio during issue; so it looks like an SBC related problem.
Internal calls do not experience this problem, nor calls between remote location do.

It's very strange to me, because I already have dozens of cloud 3cx hosted by AWS Lightsail with Windows SBC, most of them with Fanvil phones, but I've never had this problem before.
SIP Trunk provider is always the same, with 3cx official templates.

Do you have any idea?

 

[VasilisV_3CX]

Hello @M.Zanetti,

If there are issues with the SBC, you should have the audio problem when calling site to site, calling locally on one site shouldn't have the issue (as you mentioned).

A couple things to check:

1. Ensure the firewall checker has been passed.
2. Change the codecs back to G.711, this will make it easier to decode during your Wireshark captures
3. Try to isolate the different legs of the call, from Provider to PBX, from SBC 1 to PBX etc to see where the audio is breaking.

 

[M.Zanetti]

Hi Vasilis and thank you for you answer.

1. FW check successfully passed, I've did it again just to be sure about it.
2. Codecs went back to G711 immediately after G729 tests.
3. Audio @ PBX is working properly: problem seems related to SBC

 

[VasilisV_3CX]

Hi @M.Zanetti,

This is something 3CX Support would need to look into. You can contact 3CX Support via your Customer Portal under the Get Support tab.