Polycom VVX 250 and 450 not ringing

[hillview]

I have a few Polycom phones that are no longer ringing when calls are received. On my Yealink in the same network - it shows calls are being received and the BLF status changes. On the webapp, it also shows the calls being received as well as the mobile app receiving them.This is on latest firmware 6.4.3.5018. They are provisioned using STUN and can make calls externally just fine but not internally using extension calling. I've reset to factory- reprovisioned and rebooted terminal. If I call from a polycom to a yealink internally; it will ring the phone however from Yealink to Polycom the sender will ring but the recceiving phone won't and then go to voicemail. From Polycom to Polycom, the sender phone will ring on headset/speaker but the receiver phone does not ring from the base.

 

[JohnS_3CX]

Hi,

That's a typical issue that comes and goes with STUN phones, sometimes you can get lucky other times you will run into everything you described above. Due to this main disadvantage of STUN, we would recommend to consider installing an SBC at the location where the phones are.

Without getting overly technical, what the SBC does for you is that it acts as your "bridge" to 3CX and the phones no longer have to pass through the NAT and ALG services of your firewall and ISP (the main reasons which cause this known behavior you described).

The 3CX SBC can run on a Windows machine, Debian machine, Raspberry Pi 4B, or on a VM and now we also offer it on some select Yealink models (built into the firmware).

So what should you do in this case?

1. If you have one of these Yealink models, you can convert it into an SBC phone and it can serve the Polycoms too:
https://www.3cx.com/sip-phones/yealink-t5-series/

2. Alternatively you can install the 3CX SBC on a PC / VM on a Windows machine, Debian machine, Raspberry Pi 4B
https://www.3cx.com/docs/3cx-tunnel-session-border-controller/

3. Your final (and least desirable option) is to manually edit your firewall and create rules for each and every Polycom's SIP port and RTP port range. You also have to disable SIP ALG on both your firewall and your ISP equipment. We don't recommend this option but it is a hard requirement you cannot skip if you use STUN phones and want them to be as reliable as possible (yet still less reliable than SBC based).

Let us know if you have any questions regarding the above and we can help out