SBC setup

[pcmis]

I have 3cx running on local office LAN. yealink phones at office connect fine no issues. With work from home, I also have opened ports to have phones connect remotely. This also works good. The only issue I have is we have a few cases where there are 2 or 3 phones in the same house/remote lan. Sometimes only one phone works, sometimes 2 out of 3.

Is this a case for having an SBC? What would be the best (and easiest) way to resolve this?
Is the SBC supposed reside on the local office lan, or does it need to be installed at the remote lan location?

thank you in advance!!

 

[cobaltit]

We always install a SBC when multiple phones are involved, and sometimes even with just a single phone since it just works. But since you already have STUN setup, I would make sure you have unique ports for the phones as well as port forwarding and see if that resolves the issue.

 

[SteveITS]

Is the SBC supposed reside on the local office lan

In general the SBC should be used when the 3CX server is not on the same network as the phones. The phones talk to the SBC, the SBC tunnels to 3CX.

I've not had to do it but I've wondered if for this usage case it would make sense to just install the Windows SBC on one of the home PCs. Of course that PC would need to stay on for the phones to work.

 

[cobaltit]

In general the SBC should be used when the 3CX server is not on the same network as the phones. The phones talk to the SBC, the SBC tunnels to 3CX.

I've not had to do it but I've wondered if for this usage case it would make sense to just install the Windows SBC on one of the home PCs. Of course that PC would need to stay on for the phones to work.

It certainly works, as long as the user understands this. We did this a lot back in the day when the SBC was called the SIP Proxy Manager. We'd run the software on the laptop and the phone would connect through that. Most people are perfectly happy with the fact the phone doesn't work when the computer is off.

 

[pcmis]

thanks for the replies! As long as there is only one physical phone at a users house, the direct STUN method seems to work fine. But we have some cases where more than one family member both work for company. I have to tell them second person has to use windows app, or cell phone app.
I was thinking of using the windows SBC, but haven't gotten it working correctly anywhere outside office. Does running SBC at user LAN require opening up a public port on the users LAN('remote office') to SBC?

 

[cobaltit]

The SBC requires the appropriate ports forwarded to 3CX (firewall checker tests this). It does not require any port forwarding or firewall changes on the firewall in front of the SBC unless you are specifically restricting outbound traffic which most residential setups would not be doing. The other thing to check if using the Windows SBC on a users device is to make sure windows firewall or some other 3rd party firewall is allowing traffic to the SBC. This would be outbound traffic from the SBC to 3CX and inbound traffic from the phone to the SBC.

 

[ChrisC_3CX]

Just want to clarify that the 3CX Firewall checker does indeed check most required ports, however it only tests UDP ports. In the case of the 3CX SBC both TCP and UDP 5090 are required so do make sure that everything listed here has been forwarded to the 3CX PBX regardless of whether the firewall checker passes or not. That said, as @cobaltit already mentioned, in most cases no firewall configuration will be required on the 3CX SBC side.