Solved SNOM Network Failure

[technique1]

Hi,

i use a recent 3CX server hosted directly by 3CX (xxx.my3cx.fr), i have Snom and Yealink phone with latest firmware.

For the same extension i use a Yealink T46G and a Snom D765 phone. All is good on the Yealink.
On the Snom, i can receive call without any problem, but when i call someone internal or external, quickly (less than 20seconds) the phone end the call, i have a Network Failure show on the screen. My correspondant is still in call, in the 3CX console the call is still active, but nothing in my phone.

I try with another Snom, a 760. The firmware is more old but i have the same problem with outgoing call

Do you have any idea?

PS : i'm french

Regards,

Jean-Michel

 

[JohnS_3CX]

Hi Jean-Michel,

Do you use SBC or STUN mode?

 

[technique1]

Hi John, i use Direct SIP (STUN - distant)

 

[JohnS_3CX]

In this case I strongly suggest you install an SBC

STUN phones have more requirements, and we do not support them on "Hosted by 3CX" instances.
Limitations can be seen here: https://help.3cx.com/kb/en-us/68-hosted-by-3cx/6-restriction-on-hosted-by-3cx

If you still want to keep them as STUN you can do it, but you will have to do some extra work otherwise you may run into problems (like the one you described). The SBC removes those requirements and makes life easier

 

[technique1]

I just install SBC on our server, i erase my phone and i provisionne it with SBC and all works good, thank you.

It's strange that only outgoing call works bad with Snom, all other things works good.

 

[JohnS_3CX]

Hi Jean-Michel,

I'm happy to hear that it works now!

It's not really Snom's fault. When using STUN we often see that the network traffic cannot pass through the firewall to reach the PBX unless you manually open all the ports. The SBC takes care of all those problems and also allows you to have encryption without having to modify the firewall settings or the modem settings.