Quick story:

I run both Docker and Hyper-V often. I also run OpenVPN.

Earlier today I ran into an issue using OpenVPN, I've never had problems with up until today, where it wouldn't connect to any of my VPNs. Turns out it was because it could no longer bind to any of it's usual ports on my machine (Windows 10).

Long story short, after a ton of gumshoeing, Docker and Hyper-V, as far as I can tell, funked up Windows after some update somewhere along the line and reserved MASSIVE amounts of ports, so no other app could use them anymore. This applies not only to OpenVPN, but ANY app you try to use than needs to connect to a port within that absolutely massive range of excluded ports.

To be honest, I'm not entirely sure who's the dick in this situation; be it Microsoft or Docker (pretty sure MS), but at this point in time I don't even care as long as my 's working normal again. Which it is.

Here's the fix, and it's safe to try even if it turns out this specific cause wasn't your own issue, because it just fixes a "bug", setting your Windows back to the way it is supposed to be, which allegedly MS addresses in an update.

Do these steps in order, from an Admin command prompt:

• net stop winnat
• netsh int ipv4 set dynamic tcp start=49152 num=16384
• netsh int ipv6 set dynamic tcp start=49152 num=16384
• net start winnat

You can stop there and you're all done with this; everything should work fine once again, but if you want a bit of technical insight, and to see if this IS indeed your issue, run this from a command prompt:

• netsh int ipv4 show excludedportrange tcp

If you have a crazy long list, then you've probably been bitten by the bug. To further confirm, run this command:

• netsh int ipv4 show dynamicport tcp

If you see 1025 instead of 49152, you've most certainly definitely 100 million percent been bitten, and you'll be dancin a jig after running the above fix.

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