My current thoughts are to avoid the usual approach of embedding the method and property definitions in the class definitions, and instead have separate sections under [1] for

IP Addresses
IP Interfaces
IP Networks

Inside each of those sections, document the constructors directly under the section heading, and then separate out these subsections:

Common IP <kind> properties and methods
IPv4 <kind> properties and methods (if any)
IPv6 <kind> properties and methods (if any)

[1] http://docs.python.org/dev/library/ipaddress#representing-ip-addresses-and-networks