3CX can't see new IP phone over site-to-site VPN

[Frank86]

For the first time, I connected a Yealink T48S at site B connected to our 3CX server at site A over a site-to-site VPN.

I was expecting the phone to show up in 3CX > Phones as it does when on the local LAN, but it doesn't. The VPN works fine between the two sites for everything else (DFSR, AD, pinging, etc)

The phone gets a local IP address at site B in a subnet shared over the VPN (it's a small site with a flat network), but it's not seen by 3CX.

Am I doing something wrong?

 

[cobaltit]

I believe the PnP is multicast so you have to be able to pass that traffic over the tunnel.

 

[Saqqara]

At site B, configure DHCP option 66 to point to provisioning url

https://www.3cx.com/sip-phones/dhcp-option-66/

Manually add the phone to the required extension within the 3CX console - setup as local lan and enter the mac address of the phone. Can not remember if you have to untick 'Disallow use of extension outside the LAN'

Reboot the phone, and the phone should provision itself.

 

[Frank86]

At site B, configure DHCP option 66 to point to provisioning url

https://www.3cx.com/sip-phones/dhcp-option-66/

Manually add the phone to the required extension within the 3CX console - setup as local lan and enter the mac address of the phone. Can not remember if you have to untick 'Disallow use of extension outside the LAN'

Reboot the phone, and the phone should provision itself.

Is DHCP option 66 required for a site connected to the PBX via site-to-site VPN?
Does DHCP option 66 need to be set up at the remote site where the IP phone is located? That site's DHCP server is the firewall (not a Windows DHCP server) and does not support DHCP option 66.

 

[Frank86]

I believe the PnP is multicast so you have to be able to pass that traffic over the tunnel.

Is this confirmed? If so, I'm afraid my firewalls do not support PnP multicast over VPN.

 

[eddv123]

Hi Frank86,

Yes your DHCP server for those phones must be able to support opt 66. They pick up an IP address the server will point them in the direction of their provisioning link.

You could try putting the link in to the phone manually however this may not work, so as a backup I think you should consider using the 3CX SBC.

 

[Saqqara]

If the remote DHCP (site B) does not allow option 66, just entered the provisioning url manually into each phone.

 

[Frank86]

Thank you for the advice. If I set up an SBC at site B, and also want to make site B the failover site [through 3CX enterprise], would the SBC interfere with that? Would I have to manually disable/turn off the SBC for the site-A-to-site-B failover to work?

 

[eddv123]

There shouldn't be any issues using the SBC in this way. The SBC actually has a fail-over mechanism in-built that you get set on installation.

 

[Frank86]

Thank you. Will try that.