undefined | Better HN

0 pointssomerandomqaguy3y ago0 comments

.... ?

Windows and many Linux distros by default enable the privacy extensions on the link local address; it's randomized for a period of time. This is right off a Windows 10 VM:

ipconfig:

  Link-local IPv6 Address . . . . . : fe80::9aaf:a280:d593:db1%2

Notice that there's no ff:fe in the middle of the address?

RHEL 9:

  [user@localhost ~]# ip addr | grep fe80
    inet6 fe80::3544:fe14:5cf:5ad9/64 scope link noprefixroute

Fedora Core 35:

  [user@fedora ~]$ ip addr | grep fe80
    inet6 fe80::7752:d2c6:82c3:482c/64 scope link noprefixroute

Ubuntu 22.04:

  user@ubuntu:~# ip addr | grep fe80
    inet6 fe80::5ffe:c565:9de2:58f8/64 scope link noprefixroute

I don't have a Debian right on hand but IIRC they do the same thing. Alpine uses EUI64 I think though.

0 comments

bert643y ago

The link-local address is generated when you first enable the interface (ie when you load the drivers for your NIC), it won't change unless you manually force it to.

Linux will use EUI-64 if left to its own devices, or privacy extensions if you're using something like networkmanager. This makes sense because a desktop oriented distro will typically use networkmanager while a server oriented distro will not, and having a predictable eui-64 address is usually beneficial for a server.

xnyanta3y ago

Well, that is unfortunate because it invalidates a lot of the benefit of the link-local address while providing "pivacy" over the local link scope... I have not encountered any equipment in the wild that does this, thankfully. The only distros I use (NixOS and VyOS) do not have this behaviour by default so this was news to me.

j / k navigate · click thread line to collapse