Network addresses were originally defined by the internet the Internet community in five address classes. These classes were defined in order to accommodate networks of varying sizes. TCP/IP supports class A, B, and C addresses assigned to hosts. These classes define which bits are used for the network ID and which bits are used for the host ID. It also defines the possible number of networks and the number of hosts per network. Class A addresses are assigned to networks that have a very high number of hosts. The first 8-bits make up the network ID while the remaining 24-bits are used to define the host ID. This affords a network with class A addresses to have up to 126 unique networks and over 16,000,000 hosts per network. This is the largest address class in respect to hosts and compared to class B addresses. Addresses in the B class are assigned to networks that are medium to large in size. The first two bits are always assigned to binary 1 and 0, while the remainder of bit completing the first octet as well as the second are used to define the network ID. The following and remaining 14-bits are used to define the ID of the hosts. There are 16,384 networks that are allowed in this class and 65,534 hosts per network. This class has close to an even amount of networks to hosts per network ratio. Whereas class C addresses give you more networks than hosts. A class C address is assigned to networks that are small and don’t have very many hosts. The first three bits of this address class are assigned the binary code 1 1 0 respectfully. Then next 21-bits are used to define the network ID. The last 8-bits are used to define the host ID. This allows for the largest amount of networks but the fewest amounts of hosts within those networks. A little over 2.1 million networks can be made in the address class however only 254 hosts are allowed per network.
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