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Looking for a solution to get around T-Mobile Home Internet 464XLAT

AG4Q
AG4Q Member ✭✭
in Remote Operation (SmartLink)

Everything at my home seems to work very well over T-Mobile Home internet, including VPNs. The only exception is that Smartlink does not work. I am looking at two VPN approaches:

Option 1) (OpenVPN and CloudConnexa) build a layer 3 VPN to tunnel from the home network to a cloud service that to provide internet access for the flex radio to get around the T-Mobile network. I anticipate then registering the radio with Smartlink through the cloud IP gateway and then SmartSDR on IOS would discover the radio IP address via Smartlink. I am assuming Smartlink would provide authentication and be acting very much as a DDNS to locate the radio. Does this approach sound plausible? Is this how Smartlink works?

Option 2) build a VPN for the home network with a VPN client installed on the IOS device. If I build a Layer 2 VPN, the flex radio and and SmartSDR IOS client will appear as if they are on the same network and SmartSDR should be able to receive the directed broadcast from the radio and communicate directly to the radio. However I might only be able to build a Layer 3 VPN and my understanding is that the flex radio broadcast messages will not traverse a Layer 3 network. So this leads me to ask how is the broadcast handled with Smartlink?

Is there information in the Flex Radio API that I have not located that describes how the broadcast packets are handled for a Smartlink connection?

I appreciate any information or guidance. I am interested in finding a remote connection solution and also in learning the networking details required to acheive a stable solution.

Thank You,

Randy Nash, AG4Q

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Comments

  • AG4Q
    AG4Q Member ✭✭
    edited August 2025

    Digging more into the API and reading documentation again, I am beginning to answer some of my own questions. The direct broadcast and discovery are only used on the local network and that the radio sends a separate UDP stream to the WAN for Smartlink connected radios (The waterfalls and meters are which clients subscribe to are not sent via multicast). I expect I should be able to use a Layer 3 VPN if I can connect with Smartlink through a cloud IP gateway. I will be experimenting with Option 1 above.

  • sas053
    sas053 Member ✭✭

    Background

    Recently I spent a week at my grandson’s house and brought my laptop so I could remote into my FlexRadio 6400. I assumed everything would work normally, but I quickly learned the house was using T‑Mobile Home Internet. I could connect to the radio, but no data would come through—just a blank panadapter. Even my iPhone using SmartLink wouldn’t work.

    At that point I started to panic, thinking the radio might have bricked.

    Later, after leaving the house, I tried again from the school parking lot using my iPhone, and everything worked perfectly. That’s when it became clear the issue wasn’t the radio at all—it was the network.

    The Problem

    T‑Mobile Home Internet uses Carrier‑Grade NAT (CGNAT), which means you can’t do traditional port forwarding. Because SmartLink relies on open ports and direct inbound connections, it simply won’t function behind CGNAT.

    Solutions

    There are workarounds, including:

    • Using a third‑party VPN that supports inbound connections (Tailscale, Torguard, etc.)

    • Using a reverse‑tunnel service (Pinggy, LocalXpose)

    • Setting up an SSH tunnel through a VPS

    • Upgrading to a T‑Mobile Business account, which provides a static IP and allows proper port forwarding

    For T‑Mobile hotspots, there are some basic UPnP or port‑forwarding options in the advanced firewall settings, but they’re limited and often still blocked by upstream CGNAT.

    Conclusion

    My FlexRadio 6400 was never the problem—T‑Mobile’s CGNAT was. If you plan to operate remotely using SmartLink, T‑Mobile Home Internet simply won’t work without additional tunneling or VPN solutions. Anyone relying on remote operation should be aware of this limitation before traveling.

  • Mike-VA3MW
    Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin

    Sadly, this is a well known and discussed problem (many reports in this group).

    Long before SmartLink, we used SoftEther VPN to handle remote connections.

    https://www.softether.org/4-docs/2-howto/1.VPN_for_On-premise/2.Remote_Access_VPN_to_LAN

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