ipcalc takes an IP address and netmask and calculates the resulting
broadcast, network, Cisco wildcard mask, and host range. By giving a
second netmask, you can design subnets and supernets. It is also
presents the subnetting results as easy-to-understand binary values.

Enter your netmask(s) in CIDR notation (/25) or dotted decimals
(255.255.255.0). Inverse netmasks are recognized. If you omit the
netmask ipcalc uses the default netmask for the class of your network.