Easy Solution for Double NAT: Tailscale VPN and Smart SDR Using "Sub Net Routes"

I found an easy solution for using Smart SDR outside your home network (WAN), including when you have a double NAT (think cellular and StartLink). Also, perhaps, an easy work around to the current SmartLink not working with static Flex IP addresses.

Disclaimer - I have not give this a lot of testing, but it appears to be working in my situation with a Starlink connection on one end and a cellular connection on the other end (both have cellular grade NAT). I am so excited to share, I hope it works as well for others.

I have been a user of Tailscale, an easy to use VPN with secure validation. For one user, there is no charge.

Best VPN Service for Secure Networks - Tailscale

https://tailscale.com

Tailscale is a zero config VPN for building secure networks. Install on any device in minutes. Remote access from any network or physical location.

Up until the latest TailScale update, it was necessary to install the TailScale client on each machine in your network.....this prevented accessing the Flex Server thru Tailscale because it is not possible to install Tailscale on the Flex Server itself.

Tailscale recently announced two new features, "Sub-Net Routes" and "Exit Nodes". Of interest for Flex WAN access is "Sub-Net Routes". Current users of Tailscale must upgrade to get this new feature.

From the Tailscale description:

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However, you may have machines you don’t want to, or cannot, install Tailscale on directly. In those cases, you can set up a Tailscale “relay node” to advertise whole subnets at once. Relay nodes route all traffic from the Tailscale network onto your physical subnet. This makes it easy to incrementally deploy Tailscale, even on legacy networks.

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Here is a link to the installation instructions.

I updated my TailScale and ran the command to link my local subnet to the TailScale network of devices (devices I installed Tailscale on and validated myself).

Then with my laptop, running Tailscale, connected only to my cell phone, I ran Smart SDR (outside my LAN). Smart SDR showed my Flex Server on its local IP address. I clicked to connect and it connected and ran very smoothly......easy peasy!

Note - Tailscale has apps to install on all devices and operating systems. However, for now, they warn the machine providing the "Sub-Net Route" link to the Tailscale network must be a unix machine.....they plan to include the option for Windows and Mac on upcoming upgrades.

Alan. WA9WUD