Solved Snom M300 - suddendly no audio

[yetopen]

Hi. We have one M300 base with two dect configured with two different extensions. Each dect has two accounts, one on 3CX and one on the Fritx!Box modem. It has all been working wonderfully for weeks, suddenly yesterday both the phones are mute, no audio is received or transmitted! We didn't change anything, it all happened over the weekend. No update performed, no configuration change... An Android phone with 3CX app works fine. Phone calls from the two DECT (via 3cx) are mute, from android to DECT are mute. Calls within the Fritz work fine.

The M300 is behind the Fritz router, using a private IP. SIP (3cx) server is configured with STUN, extensions have the PBX Delivers Audio enabled.
What could be wrong?
Thanks

 

[FS_Mathieu]

Hello @yetopen can you provide us some important informations ?

• 3CX Version
• Server OS
• Is the 3CX Server Hosted and where ?
• IP Phone Make/Model/Firmware
• Provisioning Method: STUN
• Trunk Provider or Gateway Make/Model
• Has the Firewall Checker passed: YES / NO
• Are custom Phone Templates being used: YES / NO

By the way I check for your Fritz!Box and fount that :

AVM Fritz!Box

SIP ALG cannot be disabled. (See above on how to get around this)

from : https://www.voicehost.co.uk/help/sip-alg-and-why-it-should-be-disabled-your-router

 

[yetopen]

Thanks @INDY_Mathieu for the feedback, here's the info:

• 3CX Version: 16.0.493
• Server OS: Debian 9.9
• Is the 3CX Server Hosted and where ? Self hosted (cloud)
• IP Phone Make/Model/Firmware: Snom M300 IPDECT/04.10/B0004/22-Mar-2018 14:28
• Provisioning Method: STUN
• Trunk Provider or Gateway Make/Model
• Has the Firewall Checker passed: YES
• Are custom Phone Templates being used: NO

I see FritzBox cannot disable ALG, but as said it has been working for weeks until yesterday. Is this possible?
And now... After making some tests on the Snom base, I switched 3CX SIP registration from TLS and then back to UDP, and it's back working!

 

[FS_Mathieu]

We had the same issue at a customer's place, a STUN Yealink T48S behind a Livebox (from french provider Orange) with SIP ALG which cannot be deactivated. They randomly have the same issue as your.
We added a Raspberry SBC few days ago and they don't have the issue anymore..

SIP ALG IS THE DEVIL

 

[yetopen]

Thanks for the update, I'll see how I can circumvent the Fritz. Maybe I'll move the Snom in our LAN where I have IPv6. Thanks

 

[FS_Mathieu]

You're welcome, Let us know how it goes !

 

[yetopen]

I contacted AVM (Fritz!Box) about SIP ALG and their reply is:

Please know that none of our current FRITZ!Box models supports SIP-ALG. Thus, this feature/option/protocol cannot be disabled in the FRITZ!Box - it is simply neither active, nor existing at all in the FRITZ!Box.

Neverthelss I occasionally get no audio.
I tried enabling IPv6 but the damn SNOM doesn't seem to be IPv6 compatible, only IPv4 settings are present and even with DHCP it's not obtaining a v6 address

 

[AWS2P]

try a FW update from here
https://service.snom.com/display/wiki/BSV410B14+(base)+HSV410B11+(handset)+-+Official+Release

 

[yetopen]

try a FW update from here
https://service.snom.com/display/wiki/BSV410B14+(base)+HSV410B11+(handset)+-+Official+Release

Thanks. Unfortunately I already have the latest 4.10 version. I also wrote them more than 6 months ago for an issue with our local telecom provider, they found a bug which should have been fixed in November but they yet have to release the fix.

 

[AWS2P]

From your screen copy you have old one from 2018, not the latest one i pasted the link previously
this is link from your actual
https://service.snom.com/pages/viewpage.action?pageId=17367642

 

[JohnS_3CX]

You can also using the Exposed Host option on the Fritzbox:



If your Snom still cannot have audio after this, then it's probably something else other than the router.

 

[yetopen]

From your screen copy you have old one from 2018, not the latest one i pasted the link previously
this is link from your actual
https://service.snom.com/pages/viewpage.action?pageId=17367642

Ok, I've configured correctly the upgrade page and it updated to the one of Feb 2019. Still no audio.

You can also using the Exposed Host option on the Fritzbox:

I already have a firewall as exposed host on the Fritz! I could try moving the SNOM behind the firewall if it could have any benefit.

Thanks

 

[JohnS_3CX]

Do you have the following layout now?

Fritz -> Firewall Device -> Snom

 

[yetopen]

Fritz -> Firewall Device -> Snom

No, I currently have the Snom directly in the modem. The firewall has a public IP and a different subnet

 

[JohnS_3CX]

I think you should reset the Snom back to a single account and provisioning it as per the 3CX instructions then and see if this works as intended before you go back to using dual accounts.

https://www.3cx.com/sip-phones/snom-m300-m700-dect/

 

[yetopen]

I've reset the base and reprovisioned the DECT via 3cx (it wasn't before) and the phones are working now. Thanks everyone for the hints!

 

[JohnS_3CX]

Glad to hear it was resolved!