Internet Protocol addressing supports five different address classes: A, B, C, D and E, only A, B, and C are available for commercial use. Microsoft TCP/Internet Protocol supports class A, B, and C addresses assigned to host. The class of address defines 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 host per network.

Class A

ca

Class A addresses are assigned to network with a very large number of hosts. The high-order bit in a class A address is always set to zero. The next seven bits (completing the first octal) complete the network ID.The remaining 24 bits (the last three octal) represent the host ID. This allows for 126 network and 16, 77, 214 host per network.

Class B

cb

Class B addresses are assigned to medium-sized to large-size networks. The two high-order bits in a class B address are always set to binary 0,1. The 14 bits (completing the first two octal) complete the network ID. The remaining 16 bits (last two octal) represent the host ID. The allows for 16. 45 network and 65,234 host per network.

Class C

cc

Class C addresses are used for small network. The three high-order bits in a class C address are always set to binary 1,1,0. The next 21 bits (completing the first three octal) complete the network ID. The remaining 8 bits (last octal) represent the host ID. this allows for 2, 34, 132 network and 156 host per network.

Class D

Class D addresses are reserved for IP multi-cast addresses. The four high-order bits in a class D address are always set to binary 1, 1, 1, 0. The remaining bits are for the address that interested host recognize. Microsoft supports class D address for application to multi-cast data to multi-cast-capable hosts on an internetwork.

Class E

Class E is an experimental address that is reserved for future use. The high-order bits in a class E address are set to 1, 1, 1,1.

Example.

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