Overview of IP Addressing

Internet protocol (IP) addresses are 32 bits long. Thus, there is a possibility of approximately a total 4 billion addresses for the entire Internet. An IP address is expressed as a series of octets separated by dots. For example, the address 11111111 00000001 00000101 00001010 is written as 127.1.5.10, or using hexadecimal notation, 7f.1.5.a0.

Because of this vast number of addresses, the network is organized hierarchically into administrative domains. This organization led to the definition of name administrative domains and network classes. Since each site can vary in size, IP addresses are divided into three main types or classes. A large site can reserve a class A address and receive 2²⁴ individual addresses. A small site can reserve a class C address and receive 2⁸ individual addresses.

Network Classes

Class A uses the first octet for the network address, and the rest for host addresses within this network. For example, a site whose network address is 129.0.0.0 would own the 2²⁴ addresses between 129.0.0.0 and 129.255.255.255.

Class B uses two octets for the network address, and two for the host address. For example, a site whose network address is 129.123.0.0 would own the 2¹⁶ addresses between 129.123.0.0 and 129.123.255.255.

Class C uses three octets for the network address, and one octet for the host address. For example, a site whose network address is 129.123.56.0 would own the 2⁸ addresses between 129.123.56.0 and 129.123.56.255.