Network Failure Message on Snom Handsets

[PaulCarter]

Hi,

We have a new customer for whom we have installed 3CX and re-used their old Snom 715/725 handsets. The 3CX is hosted in Google and the users at the moment are all homeworkers provisioned as STUN remote phones.

All users are complaining of calls cutting off after around 30 seconds and they get a Network Failure message on the Snom, the call stays connected for the other party. For our other customers we now have thousands of users all using Yealink handsets and we never seem to get any issues like this with remote workers so I'm guessing it is something about the Snom phones causing this, has anyone else come across this?

TIA

 

[JohnS_3CX]

Hi Paul,

As you are probably aware, STUN has some additional requirements in order to work.

The 30 seconds is rather telling, probably one of the two sides cannot reach the other properly to deliver the SIP signalling and the call is cut off once the SIP timer expires.

Assuming the firewall checker passed on the PBX end, your options now are:

- Either manually configure each users' router to open the necessary ports
- Or give them each an SBC (ie. on a small Raspberry Pi) to bypass any restrictions set by their modem/router
- And alternatively, give them access over the 3CX webclient or 3CX apps which have built in methods that can bypass router NAT restrictions are remote locations

Take a look at the above article and try troubleshooting a single user to see if you can get one working properly, then decide from there how you want to proceed.

Let us know if we can be of further assistance!

 

[PaulCarter]

Hi John,

Thanks for your reply. It seems strange when with our Yealink remote STUN users they do get the odd one that has an issue and needs to be setup as you have mentioned but on the whole they work OK. But with this site with all Snom handsets they ALL have the issue. Is this issue known to be worse when using Snom handsets?

 

[JohnS_3CX]

Hi Paul,

Not necessarily a Snom matter, but the thing with STUN is that you have to many variables that can get in the way, even though they might appear to work beautifully, a day comes when they stop working out of the blue with seemingly no explanation.

We do know the usual culprits of course, some of the reasons are:

- SIP ALG on the modem
- Provider changing/updating their modems
- Provider reserving standard SIP ports
- Modem NAT behaves in unpredictable manner after some time passes
- 1000s of possible router/modem brands with multiple FW versions each having their own internal ruleset and implementation
- And yes, even the phone's own implementation of STUN may somewhat differ from brand to brand, making one brand more likely to "escape" the confines of the modem than another but it's not really their fault to be honest..

I could go on but it's much simpler to control these factors with static port forwards telling the modem "here's what I specifically want you to do with this IP address"

PS: also make sure the snoms are running the latest 3CX-supported firmware. A quick visit to the "Updates" and then the "Phones" tab should confirm.

 

[PaulCarter]

Hi John,

Thanks for your help. Unfortunately setting up phones with static IP addresses and NAT on customers' home routers is not really feasible so we will suggest a raspberry pi SBC.

Regards,
Paul

 

[JohnS_3CX]

Good choice!