Solved Polycom SP335 -- Echo Test sounds great, but getting one-way audio on all other calls

[fancyHeat]

Ran into a pretty weird issue where I can call the Echo Test, and it works fantastic. However, on any other calls (internal, external, voicemail) all have one-way audio. In this case, audio is not being delivered to the Polycom SP335, but the other party can hear me fine.

Infra: Clean install 3CX V18 hosted in the Cloud, with Polycom SP335 onsite connected via a VPN. I also have a Yealink T54W connected to the PBX in the same manner, with no issue. SP335 is updated to the latest firmware.

 

[SweetAction]

Try changing the extension settings "PBX delivers audio"

 

[fancyHeat]

Try changing the extension settings "PBX delivers audio"

Already tried that, unfortunately no change.

 

[JohnS_3CX]

Hi,

a) Firstly, keep in mind that these are EOL devices with a lot of limitations, so we no longer test them against the latest version of 3CX. They may work upto a certain point, but in case they have any issues with newer versions of 3CX, there won't be any updates or further improvements to them.
https://www.3cx.com/sip-phones/polycom-soundpoint-450-550-560-650-670/

b) VPN can be done in a number of ways (both in the protocol of choice, and the method of routing). Perhaps it is related to the way your VPN works, but the Yealink working might be a sign that the VPN is OK (unconfirmed).

Your best bet would be to run captures on the PBX and on the Polycom's LAN port, and compare the SDP and packet flow if you are able to do so. That's pretty much the only way you can reliably learn whether it is a VPN issue, phone issue or some other factor, or even perhaps a combination of these factors.

 

[fancyHeat]

This has been resolved! There was a weird issue with the Tailscale VPN not updating the routes correctly until after a reboot. We also had to turn off snat on the VPN.

 

[JohnS_3CX]

Glad to hear you located the issue, thanks for updating the thread with your solution