3CX V20 and Fanvill X3U Pro without an SBC/router phone on-premises

[pete]

Background:

 

• We use Fanvill X3U and X3U Pro phones. No issues in ~3 years not related to end-user misadventure.
  
• 3CX is sat offsite as a VM in a third-party datacentre for "if it all burns down, would be great if the phones still work" reasons.
  
• Prior to 3CX V20, all was fine.
  
• Since V20, via an SBC (secondary schools) the X3U and X3U pros all work fine.
  
• Without an SBC (primary schools) the X3Us work fine, but some (~6 phones so far) previously-working X3U Pros will sit with a status of "timeout".
  

 

Deleting an affected X3U Pro phone from 3CX, manually reprovisioning it with the MAC and then resetting the phone to factory will cause it to rejoin 3CX and be managable and receive calls. Except the recipient can't hear the caller.

 

If I add an Fanvill X3U (provisioned the same way) to an affected extension (same physical site/network/route to datacentre) it can make and receive calls without any issues.

 

I've got third-party support looking into it with a backup plan of swapping the X3U Pros for the bare X3Us. Support did mention that V20 has a lot of improperly documented strangeness that they're slowly discovering across their customers.

 

Anyone else had anything similar with V20? The event logs in 3CX and the phones themselves don't have a lot of clues. I'm wondering if there's an issue with the phone template or firmware in 3CX for the Pro version.

[Davit2005]

I noticed with 3cx v20 that my trunk stopped working all of a sudden. This is with an on prem 3cx server.

 

The 3cx system would not register with the SIP trunk provider, setting registration to auto fixed it. No firewall changes had been made between it braking and working OK. It does not help that I am using a non-supported SIP trunk and they were absolutely useless in getting any basic information and simply said we don't support 3cx and I've been with them for 5 years

 

Firewall wise is SIP ALG enabled or disabled, has that been changed?

[pete]

Yeah, ALG is off because it's always terribly implemented.

 

3rd party support looked into it and the gist is.

 

While direct STUN may still work, it's deprecated in 3CX and if you open a 3CX support ticket related to issues with phones talking directly to 3CX they'll close the tickets with "we don't support STUN anymore, use the softphone or deploy an SBC/routerphone".

 

So I'm currently rolling out SBCs (each school has at least one Hyper-V host) to the primaries.

 

However, that's a problem for people WFH with a physical phone plugged into their BT homehub.

Edited September 5, 2024 by pete