[m463]

An "fun" use of ip addresses is in NTP.

in the ntp config file, you will have stuff like this:

  server 127.127.1.0 # local clock

or:

  server 127.127.20.0 minpoll 4 iburst prefer  # gps clock

where the "ip address" is of the form: 127.127.<clocktype>.<instance>

here's a page explaining the clock types:

https://www.eecis.udel.edu/~mills/ntp/html/refclock.html

but basically it's a weird anachronism. I'm not sure if NTP will actually bind to those addresses using the tcp/ip stack, or if it someone just got lazy and coopted the ip address parser for off-label use.