Subnet++ is specifically designed for network professionals and students alike. It can be useful for complex super-netting, as well for learning binary math and subnet calculations.

+++Now provides Universal support for Iphone+++

Features:
Dynamically selects the proper class of address based on IP provided by the user.

Populates host ranges, network, and broadcast addresses on the fly.

For each selected subnet mask the following details are available. These paramaters can also modify the network if changed:

Netmask Bits
Hosts Per Subnet
Subnet Bits
Max Subnets

Finally based on the selected fields it will provide all available subnets for the class of IP address. Touching any available network, the host range, network, and broadcast match will also update to reflect the selected network.