One-Way Audio Issues

[tdhaslett]

Hey Team,
We're having some issues with one-way audio on all three desk phones (Fanvil X7C) in a remote office (I am in the remote office). On inbound calls to 3CX, there is one-way audio - caller to callee works, callee to caller does not. On outbound calls out of 3CX to a public phone number, there is normal two-way audio from all three extensions. No reports of audio issues in the main office, there is only one remote office, and it's all three phones in the remote office having issues.

There is a site-to-site VPN between offices with FortiGates on both ends. The phones connect through the VPN to the private IP of the 3CX server. I've checked the policies. All ports are opened both directions between the 3CX server and the phones, and static routes are properly in place.

I upgraded from v18 to v20 on Saturday and they tell me that the phones worked fine yesterday (Monday), so I don't think it's related.

I have enabled Call Quality Tracking on the two phones that are most used, but I do not see anything in those reports that tells me anything useful yet. In fact, the score is 'Unknown' for all four legs. I tried a call from my mobile app to two extensions and got normal two-way audio (the third phone is mine, so same extension). Scores on the app calls were Medium to Excellent.

I am totally stumped at this point. Any help or direction anyone can provide would be greatly appreciated!

 

[Alphabetic]

Are they X7C-V2?

Make one a router phone and have the phones go through that or install an SBC.

Or get a network engineer in to fix your routing.

 

[NicholasP_3CX]

If these phones are in a private VPN network, then you may need to open up the internal audio ports to and from the PBX to the phones.

Do a packet capture and see which ports are being negotiated. You should see the internal call leg between the phones and the PBX negotiating a port in the 7000 range. This range (7000-8449) should be opened on your VPN firewalls, as they may be the ones blocking this. This is only internal traffic. DO NOT open this from the public internet.

The capture should show you if all the streams are being delivered properly

 

[tdhaslett]

@Alphabetic the phones are v1.0.

@NicholasP_3CX All ports are allowed in both directions. I am seeing ports in the 10000 range, but traffic seems to be normal according to the packet captures.

It gets even stranger:
Calls answered via their queue on the desk phone have one-way audio. Calls directly to or from the extensions, both internal and external, on the desk phones have normal two-way audio.

There is a second issue with the system that I have learned about. This is system-wide. Voice mail emails no longer have the transcription after the upgrade to v20. All users are set to use department settings, and all Departments are set to transcribe Voicemails Only.

I forgot to mention that this is an on-prem Windows server. I plan to restart the server tonight because I can't find a reason for either of these issues.