Internet Addresses

Internet address refers to the unique identification or address assigned to each machine in the physical network. The basic need for assigning Internet address is to identify every machine in the network. Internet address is defined as the 32-bit (or 64 bit) address assigned to each machine on the internet so as to identify that machine while establishing network communications. There are 5 classes of Internet addresses – Class A, B, C, D and E, thus dividing the physical addresses into class A, class B, class C, class D and class E networks.

Class A address

Class A Address corresponds to the address assigned to the machines in the class A network. Class A address starts with bit 0 as shown above. Network address part is 1 byte and host-id part is 3 bytes long. The total number of physical networks possible in class A address scheme is thus – 2⁷ – 1 = 127 networks (its 2 to the power of 7 not 8 since the first bit [0 to 1] is used up as 0 or starting bit; minus 1 is done to account for a reserved pattern). The total number of hosts possible in class A networks is 2²⁴ – 2 = 16,777,2 hosts (minus 2 to account for reserved patterns). The network address part of class A networks ranges from 1 to 127. Bit patterns of all 1s and 0s are reserved in case.

Class B address

Class B Address corresponds to the address assigned to the machines in the class B network. Class B address starts with 1 0 bit pattern as shown above. Network address and host-id part is 2 bytes each. The total number of physical networks possible in class B address scheme is thus – 2¹⁴ = 4096 networks. The total number of hosts possible in class B networks is 2¹⁴ – 2 = 65,534 hosts (minus 2 to account for reserved patterns).

Class C address

Class C Address corresponds to the address assigned to the machines in the class B network. Class B address starts with 1 1 0 bit pattern as shown above. Network address part is 3 bytes and host id part is 1 byte long. The total number of physical networks possible in class C address scheme is thus – 2²¹ networks. The total number of hosts possible in class C networks is 2⁸ – 2 = 254 hosts (minus 2 to account for reserved patterns).

Class D address

Class E address

Since there can be many network connections to a machine, it require multiple IP addresses to identify each physical connection. So in general, since IP addresses encode both a network and a host on that network, they do specify an individual machine, but a connection to a network.