Sipcalc is an advanced console-based IP subnet calculator. It can take multiple forms of input (IPv4/IPv6/interface/hostname) and output a multitude of information about a given subnet.
Retrieving of address information from interfaces.
Classfull and CIDR output.
Multiple address and netmask input and output formats (dotted quad, hex, number of bits).
Output of broadcast address, network class, Cisco wildcard, hosts/range, network range.
The ability to «split» a network based on a smaller netmask, now also with recursive runs on the generated subnets. (also IPv6)