As alluded to in issue bpo-38655, the behaviour for getting categorising IPv4 networks is inconsistent with the IANA guideline, which the docs say it follows.

I'm proposing we either change the documentation so that it describes the behaviour that should actually be expected, or we rewrite some parts of the ipaddress module so that they follow the guidelines.

For the latter, my thoughts would be to actually implement the check table on the IANA page (https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml).

i.e for a given address, you can ask of it "is_forwardable", "is_globally_reachable", etc.