Sipcalc is an console based ip subnet calculator with IPv4 and IPv6 support. Sipcalc development started back in 2001 and has most of the features I want in an ip calculator. It is no longer under active development, though bugfixes and patches are accepted. Sipcalc is available in many Linux/BSD distributions, usually as a package named sipcalc.
Source Files (show merged sources derived from linked package)