Each IP address uniquely identifies an interface in the internet and consists of a network part and a part for the hosts in the network. It is 32 bits long (equivalently, 4 bytes) and besides its binary representation, it can be written in a so-called dotted-decimal notation, in which each byte of the address is written its decimal form and is separated by a dot from the other bytes.
With subnetting, a hierarchical partitioning of the network into several subnets is provided. Routers constitute borders between the subnets. To implement subnetting, a subnet mask is needed, that indicates the split between network, subnet and host number. Subnet masks are also written in binary or dotted-decimal notation. An alternative notation is the dotted decimal IP address with the addition of a slash followed by the number of bits in the network and subnet part (e.g., 126.96.36.199/24).
This IP calculator takes an IP address and a subnet mask and calculates the resulting subnet ID, the broadcast IP and the host range. Try several addresses and masks and find the corresponding subnets! How many hosts are in the subnet?