SBC phone not registering, 4102 error (system down)

[voxclear]

See attached, I requested MSP that manages network to check firewall but nothing has changed since overhaul in 2019 and rules were set then. Public IP address is static, has not changed, fwiw. What else to look for/at?

Thanks!

 

[KyriacosS_3CX]

Hi,

For starters, reboot the SBC phone in case it's having a bad day. Let's see if that clears the issue.

 

[KyriacosS_3CX]

Also, if it is used as wireless, look into that, maybe wifi interference - and more generally SBCs should not be set up over wifi.

 

[Alphabetic]

Does 3CX pass firewall test?

Is there an SBC at another site you can monitor to see if this drops at the same time?

How far do you want to test? vs swap out the sbc

is their internet dropping?

What is the sbc connected to? is there a hw failure on its path out to the internet

next steps - network captures.

you could try upping the logs on the phone and reviewing them too.

when the SBC goes down, from a device on the network, do a telnet test

telnet fqdn 5090

if it can talk to 3cx you should get something like this back

 

[voxclear]

Hi,

For starters, reboot the SBC phone in case it's having a bad day. Let's see if that clears the issue.

Thanks, tried that one, no joy.

 

[voxclear]

Does 3CX pass firewall test?

Is there an SBC at another site you can monitor to see if this drops at the same time?

How far do you want to test? vs swap out the sbc

is their internet dropping?

What is the sbc connected to? is there a hw failure on its path out to the internet

next steps - network captures.

you could try upping the logs on the phone and reviewing them too.

when the SBC goes down, from a device on the network, do a telnet test

telnet fqdn 5090

if it can talk to 3cx you should get something like this back

View attachment 50390

thanks, will try that.

 

[voxclear]

Also, if it is used as wireless, look into that, maybe wifi interference - and more generally SBCs should not be set up over wifi.

I'll look into that, get them to move it to a wired position if it's on wifi.

 

[voxclear]

Does 3CX pass firewall test?

Is there an SBC at another site you can monitor to see if this drops at the same time?

How far do you want to test? vs swap out the sbc

is their internet dropping?

What is the sbc connected to? is there a hw failure on its path out to the internet

next steps - network captures.

you could try upping the logs on the phone and reviewing them too.

when the SBC goes down, from a device on the network, do a telnet test

telnet fqdn 5090

if it can talk to 3cx you should get something like this back

View attachment 50390

So their MSP finally reached out to me. The T53W SBC phone has a wired connection, it is getting an IP address and a PC connected through it reaches the internet. They do not see any issues on the firewall (looking for the phone's IP address reaching out to FQDN. Is the command > telnet xxxxx.yy.3cx.us 5090 ? I tried that from my office using putty, not connecting (but might be doing it wrong). Could the problem be at the 3cx server?

 

[voxclear]

Added an SBC to the Windows server and 3cx logs show it's up: Trunk SBC 'SBC942403' (###.###.###.###/192.168.222.3) has changed status to Up. Ran telnet from server, host lost (see attached). Firewall issue? What to look for? Thx

 

[Alphabetic]

When you run the telnet command you get that APK text returned which shows you're able to communicate with 3CX over the tunnel port. The connection lost is to be expected.

If you couldnt reach it, you wouldnt get the "APK".

Are you able to do this from their network when their phones go down?

 

[voxclear]

When you run the telnet command you get that APK text returned which shows you're able to communicate with 3CX over the tunnel port. The connection lost is to be expected.

If you couldnt reach it, you wouldnt get the "APK".

Are you able to do this from their network when their phones go down?

That was from their network. The SBC is up but no physical phones are registering, no matter whether their pegged to the server SBC or the T53W. .

 

[Alphabetic]

is the SBC statically set with its IP or have they done a DHCP reservation

 

[SteveITS]

@voxclear I didn’t see an answer about the 3CX server’s firewall test…?

 

[JohnS_3CX]

That was from their network. The SBC is up but no physical phones are registering, no matter whether their pegged to the server SBC or the T53W. .

That's your biggest hint right there that this is network related as you have now confirmed with both the router phone and dedicated SBC.

Here's what's next:

1. Read the SBC logs to learn if the problem is reaching 3CX or not C:\ProgramData\3CXSBC\Logs
2. Make friends with Wireshark on the SBC machine to learn if the phone registrations are hitting the SBC machine, from what actual IPs and ports, and what the SBC replies back
3. Use pcap on the phone to confirm any suspicions

With this you can then go to the network administrator and make your case if needed.