IP Subnet Calculator
A good subnet calculator should be handy in any network engineers toolbelt. This subnet calculator allows for the input of a netmask, a Cisco wildcard mask, a /CIDR notation or it can be given the number of hosts needed and calculate the network required. See examples for possible inputs.
The tool also has the ability to create a random IP address which can then be calculated. This is useful when studying how to subnet and practice networks are needed.