Provisioning issues with Yealink T46S via SBC.

[Sarif]

Hi all,

I have a remote test site, which comprises of just a SBC (Raspbian), a YeaLink T46S (Fimrware: 66.84.0.35) and a Windows 10 laptop.
These devices are all connected to a Cisco switch, which in turn connects to a test FW (also acting as the DHCP server) that has a VPN to the production FW (the FW's are actually locally connected by a copper cable) and finally a cable running from the production FW to a Cisco switch and the VM server acting as the 3CX PBX (v 15.5.15502.6).

Currently I'm struggling to provision the YeaLink. If I take the YeaLink and plug it into the LAN where the PBX is located, I can provision the phone without any issues.
However when I try it through my remote test network, I can see on the PBX GUI under "Phones" the phone appearing as "10.10.96.102:5059 via SBC 10.10.96.101:5060" (Image Phone Visibility attached)
But when I try to Assign Ext > Choose extension number > Check the settings under IP Phone are correct (Image Assign Ext. attached) then click OK, the phone doesn't receive the configuration file.

In terms of troubleshooting, I have:

• Performed packet captures on the PBX/SBC/Phone and verify that all 3 devices can communicate with each other.
• Through the YeaLink T46S admin menu, I have set "Only Accept Trusted Certificates" to Disabled as packet captures initially revealed a problem here, but changing this setting had no effect.
• Upgraded SBC to the latest version.
• On the Windows 10 laptop, I can can responses to the FQDN of the PBX. Also using the 3CX downloadable Firewall checker utility tool, I can confirm nothing was being blocked.
• Followed the guides:
  • https://www.3cx.com/docs/3cx-tunnel-session-border-controller/
  • https://www.3cx.com/sip-phones/yealink-t4-series/
  • https://www.3cx.com/docs/manual/configuring-ip-phones/

One area I may have misunderstood is the provisioning process, my understanding is:

1. Phone boots up, discovers SBC device.
2. SBC acts as a intermediary for the phone, sends provision request to PBX.
3. On PBX GUI, user assigns phone to extension.
4. Configuration file is sent to phone to provision it.

If that is the case, the URL in the Provisioning Link doesn't initiate a request to download a link if I enter it into a browser and just leads to a 404 - is this expected behaviour at all?
Any help would be greatly appreciated as I feel like I'm missing something obvious.

Kind regards,

 

[Saqqara]

Do you have a site to site vpn between the two locations and traffics flow in both directions, if so configure the phones as local (you do not need an SBC Server). You may have to setup DHCP with option 66. (https://www.3cx.com/sip-phones/dhcp-option-66/) to point to the 3CX server

If you do not, then you have to use an SBC server

Make sure you have unticked - 'Block Remote Tunnel Connections (3CX App connections with Tunnel enabled & SBC will be blocked)' under Phones - Options

Check your blacklist, remove any necessary IP's as required.

Make sure you have the https port 5001 configure on the firewall to point to the 3CX server. This is required to provision the phones

All info on setting up this phone - https://www.3cx.com/sip-phones/yealink-t4-series/

 

[iversion-Support]

You don't need SBC if you are running a VPN, if you running a VPN in your remote site are you using local DNS or public DNS, is your 3CX DNS is resolving to private IP or Public.

We prefer using SBC rather than relying on site to site VPN. You mentioned you provisioned the phone in local site but when you move the phone to the remote site its not provisioning, can you please make sure you wipe the phone set factory reset before you try to re-provision at the remote site.

You don't need to login to the phone if you are using SBC, when assigning phone to extension make sure to select SBC / type the correct IP. Sometime adding phone mac manually to the extension under provisioning work better than assigning phone from the phone tab. Also be patience, reboot the phone after factory reset and wait.

Let us know if any of this help.