Solved Yealink T33G Phones Show “No Service” via 3CX SBC While Grandstream PhonesWork

[Aldakheeloud]

Our Grandstream GXP-1625 phones are registering and operating normally, including from remote networks.


However, the Yealink T33G phones show “No Service” when connected from remote networks through our VPN/SBC environment.


The Yealink phones can work when connected within the local network, but they fail to register when used from remote locations.


Multiple Yealink T33G phones are affected, while Grandstream phones continue to operate correctly in the same environment.
Troubleshooting Already Performed

We have already performed the following:


Factory reset the Yealink T33G phones.


Deleted and re-added the phones/extensions in 3CX.


Reprovisioned the phones.


Verified the phone MAC addresses.


Verified that the Windows 3CX SBC service is running.


Verified DNS resolution of the 3CX FQDN.


Verified connectivity from the SBC server to the 3CX cloud PBX

 

[Alphabetic]

Nevermind, i dont think it would make a difference.

Are you able to enable wireshark on the SBC and confirm you see the registration attempt from the phone?

 

[Aldakheeloud]

Nevermind, i dont think it would make a difference.

Are you able to enable wireshark on the SBC and confirm you see the registration attempt from the phone?

we have Debian SBC Server..Here i can,t see registration attempt.only show phone which already registration

 

[Alphabetic]

You'd need to stick your SBC into verbose logging and probably have to restart it. Try the phone registration, pull the logs off the SBC and then use Wireshark to check if the traffic from the phone is hitting it. If it isnt, then you have a routing issue.

you could also first try a capture from the 3CX mgmt console but if it doesnt hit it, you'll need to troubleshoot back from the SBC.

https://www.3cx.com/docs/capture-network-traffic/

 

[Aldakheeloud]

i Attact the pcap file.

 

[Aldakheeloud]

Wireshark

 

[Alphabetic]

Wireshark

Maybe pcaps are blocked you might have to change the extension to .txt first

 

[Aldakheeloud]

Txt File

 

[Aldakheeloud]

Zip

 

[Alphabetic]

Run the capture again and zip it up, this file is corrupt.

Are you running this off the SBC or 3CX?

 

[Alejandro_3CX]

Hi @Aldakheeloud just a quick question, if you provision the same user extension but using the 3CX application on your smartphone, does it register or not? try it using Mobile Data and another test with the WiFi connection using the same LAN as the phone.

 

[Aldakheeloud]

Thank you so much Guys .
i founded the issue and now it's work

 

[bitn2]

Thank you so much Guys .
i founded the issue and now it's work

What was the issue?

 

[Alphabetic]

yeah be helpful to know..

 

[Aldakheeloud]

There was issue in Firewall.
Routering and Roles , After Changed Then its worked But Then another issue No voices coming but side.
After i Allow Media Ports Then its start working.
Also Media Ports was Block.
Thanks

 

[JohnS_3CX]

The main problem was that your SBC is not in the same LAN as the phones.

• Phones were in 172.x.x.x
• SBC was in 192.x.x.x

The SBC is intended to be on the same LAN as the phones, otherwise you have to start editing firewall rules to build a path like you were forced to do in this case.