Flex behind CGNAT network; experiences with SoftEther / VPN Azure and alternatives

HB9CAT

If your Flex is connected behind a router using a CGNAT connection (typically a 4G/5G router in Europe), you can't use Smartlink because the public IP address your router gets is not reachable (typically 10.x.y.z).

Flex recommends to use the SoftEther VPN software to get around this problem; the advantage of SoftEther is it's bridging function; so the SoftEther client will create a new virtual IP interface that is virtually sitting on the same LAN as the Flex on the server's side, so you get to see the Flex just like if it was on your local LAN.

SoftEther works just fine if the Server (so the Flex) are on a reachable network; if not (the CGNAT case) it can relay through a VPN Azure connection to resolve the connectivity issue.
It works. The issue is that going through VPN azure introduces latency, in my case around 500ms, which is functionally OK (SmartSDR works) but quite frustrating.

I had already deployed an alternative solution to the CGNAT problem by using LogMeIn Hamachi ( https://www.vpn.net/ ) ; one PC (or Raspberry) on the Flex side connects to the LogMeIn cloud, and so does the client PC: they find themselves to be in the same IP network ( in my case a 25.x.y.z network).

So I tested using Softether with no VPN Azure funtionality, instead the Softether client connects to the LogMeIn IP of the Server (where the Flex is). The bridging function of Softether is performed and voilà I see my Flex virtually on my LAN.
The good thing is that latency is much much better than going through the Azure cloud, in my case it was just 30ms, so perfectly usable :-)

I believe LogMeIn comes for free for up to 5 connected PCs; as I have more than 5 I did buy a yearly subscription and I'm very happy with it. (Disclaimer: I do not work or am in any way associated with Hamachi / LogMeIn).

I know that a Flex behind CGNAT is a pain for many people, so I throught that sharing experiences in the community is important.

73
Marco HB9CAT