LukasJul 18, 2025

Mildly cursed factoid about UNC paths:

- UNC Paths can contain IP addresses such as \\192.168.1.1\share
- IPv6 addresses are supported as well
- IPv6 addresses contain colons
- can't have colons in Windows paths since colons are reserved for drive letters

So Microsoft came up with the the ipv6-literal.net domain that's special-cased by Windows so you can to write IPv6 addresses in UNC paths as 2a0e-3c0--21.ipv6-literal.net without it hitting any resolvers.

Show threadLukasJul 18, 2025

Turns out, it's worse than this: The ipv6-literal.net shenanigans aren't limited to UNC paths.

It works in all places:
> ping 2a0e-3c0--21.ipv6-literal.net

Pinging 2a0e:3c0::21 with 32 bytes of data:

Also works in browsers: http://2a0e-3c0--21.ipv6-literal.net/

Thanks to @casandro for asking.

Show threadNik | Klampfradler 🎸🚲
@karotte @casandro They could at least have made it resolve globally as well.
Jul 19, 2025 at 6:15amWeb
Show threadDavid MaloneJul 19, 2025
@nik @karotte @casandro This is interesting - the domain is registered, but not to Microsoft and it seems like it has been that way for a while! https://serverfault.com/questions/566382/is-it-possible-to-use-an-ipv6-address-to-connect-to-a-remote-share