http://www.routemeister.net/projects/sipcalc/description.html

Example features include:
IPv4 -

* Multiple address and netmask input formats.
* Retrieving of address information from interfaces.
* Classful and CIDR output.
* Multiple address and netmask output formats (dotted quad, hex, number of bits).
* Output of broadcast address, network class, Cisco wildcard, hosts/range, network range.
* Output of multiple types of bitmaps.
* Output of a userdefined number of extra networks.
* Multiple networks input from commandline.
* Parsing of a newline seperated list of networks from standard input (STDIN).
* The ability to "split" a network based on a smaller netmask,
now also with recursive runs on the generated subnets.
* DNS resolution.

IPv6 -

* Compressed and expanded input addresses.
* Compressed and expanded output.
* Standard IPv6 network output.
* v4 in v6 output.
* Reverse dns address generation.
* The ability to "split" a network based on a smaller netmask,
now also with recursive runs on the generated subnets.
* DNS resolution.

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