Yeastar TG1600: Persistent UNREACHABLE / Request Sent Status

[anthony.labrador]

Hello 3CX Community,

I am seeking urgent assistance with an issue connecting my Yeastar TG1600 GSM Gateway to my self-hosted 3CX instance. The gateway fails to maintain registration and consistently shows "Request Sent" / "UNREACHABLE" status.

I suspect the problem lies with the Cloud Provider's Firewall, as I cannot access the security group, yet all internal diagnostics passed.


1. System and Network Context

Component	Value	Rationale for Inclusion
PBX Public IP (Server)	188.166.XXX.XXX	The server IP that needs to accept the connection.
Gateway Public IP (TG1600)	203.XXX.XXX.XXX	The IP that needs to be whitelisted by the Cloud Host.
PBX Diagnostics	3CX Firewall Checker PASSED	Proves the issue is external to the 3CX application and OS firewall.
Local Firewall (TG1600 Site)	Cisco Firepower 1120 (FTD)	To rule out blocking on the TG1600's side.

2. Diagnostic Findings​

1. TG1600 NAT Setup: STUN is Enabled (using stun-au.3cx.com and the External IP Address is correctly set to 203.XXX.XXX.XXX.
2. Registration Behavior: The gateway temporarily achieved Registered status, confirming correct credentials, but immediately reverted to Request Sent/UNREACHABLE.
3. Packet Capture (Wireshark): The capture confirms One-Way Traffic. The TG1600 sends SIP REGISTER/OPTIONS, but receives no response packets from the 188.166.XXX.XXX server.

3. Specific Question​

I do not have access to the Cloud Host's Security Group/Firewall.

• Has anyone encountered issues with the 188.166.x.x IP range needing manual whitelisting for SIP traffic?
• Could you advise on which common Cloud/VPS Provider uses this IP range so I can attempt to contact their support?

Thank you for your help!

 

[Alphabetic]

Where did you do the packet capture?

do you see the registration attempt in 3CX? If no, check firewall/blacklisting.

 

[anthony.labrador]

Where did you do the packet capture?

do you see the registration attempt in 3CX? If no, check firewall/blacklisting.

Hello @Alphabetic
Thank you for the quick reply.

1. Packet Capture Location: The capture file was taken directly on the Yeastar TG1600 Gateway through the packet capture tool.
2. Registration Attempts: I can confirm that the registration attempt IS reaching the 3CX. The gateway status temporarily changed to Registered (Status: Registered, Reachability: UNREACHABLE) before reverting to Status: Request Sent.
3. Key Finding: The capture file confirms that the REGISTER packet goes out, but NO RESPONSE packets (no 401 Unauthorized, no 200 OK) are received back by the TG1600.

3CX internal firewall is fine when testing firewall running inside 3CX system, the Cloud Provider Firewall on the [188.166.XXX.XXX] side is selectively dropping the return UDP responses (SIP 5060) to our public IP 203.177.XXX.X.

I currently do not have administrative experience or access to the Cloud Provider's console, where the 3CX is hosted. This is the main blocker preventing us from manually whitelisting our public IP.

Do you have any experience with which major cloud host uses the 188.166.xx IP range, as we are currently unable to access the Cloud Host's firewall settings?


Thank you

 

[Alphabetic]

Hello

I have no idea which cloud platform you're referring to. But it sounds like you've already identified your issues - you should reach out to their support too and see what they say.