IP Addresses identify both a network as well as host on a network. Depending on the class of a network, certain amount of bits in the IP (32 bits overall) are allocated for network adressing and the rest is for: adressing the host on the network.
- Class A: first octet is network, last three: host
- Class B: first two octets are for network, last two: host
- Class C: first three octets are for network, only last octet is for host.
Furthermore, looking at the IP itself, you can tell which class of IP it is, using the following rules: