Updating with some more testing on the new build 10162.
That command now returns this:
C:\Windows\system32>netsh interface ipv6 add v6v4tunnel interface=IP6Tunnel 10.0.0.2 216.66.80.26
The function attempted to use a name that is reserved for use by another transaction.
This was on a fresh install.
Each time the command is ran, it will create an additional interface in Device Manager -> Network Adapters, but none of them will work.
This bug is getting quite worrying, as the release date draws closer.
EDIT -
Well, this is embarassing, and really weird. I've been trying different things for a couple days before posting this message, and I always had the same result.
I tried -again- just as I was typing, to copy the error message..
And, well.. I tried again after posting.. it went through. It properly created the interface, and it works. I did not change any setting, nor any connected device or anything.
I did nothing different than 5 minutes ago. just deleted the broken interface in device manager, and tried adding v6v4tunnel again.
I'm not sure if it will work again if I try to remove it. If nobody is interested in proper troubleshooting, I'll just leave it there since having working ipv6 is more important to me
than mere personal curiosity.