IP Addressing

By Stephen Bucaro

Internet Protocol (IP) is a Network layer protocol used to route packets across networks. The IP protocol uses a 32-bit address to define the network segment address and the node address. If the device is to be connected to the Internet, the address needs to be unique among all other devices connected to the Internet. You can ensure that your IP address is unique by obtaining an address from the Internet Network Information Center (InterNIC). For networks, InterNIC assigns blocks of addresses.

An 8-bit binary number can be written as a decimal number between 0 and 255. An IP address is usually written as four 8-bit decimal numbers that are separated by dots. The numbers 0 and 255 are reserved for special purposes. A "subnet mask" is used to determine which part of the IP address is the network address and which part is the node address. The right side part of the number is the node identifier. The more digits used for the node identifier part of the number, the more hosts you can assign to the network.

Address Classes

InterNIC assigns blocks of addresses defined by classes. Class A networks use the right three parts of the address for host identifiers. This allows the assignment of 16,77,214 unique host identifiers. This leaves the left part of the address for network identifiers. The first bit of the leftmost part of the IP address is used to identify the class type. This leaves seven bits for network identifiers, allowing for 126 unique network identifiers.

Class B networks use the right two parts of the address for host identifiers. Class C networks use the right one parts of the address for host identifiers. Using a network class with less parts for host identifiers leaves more parts for network identifiers. Below is a chart of the number of networks and hosts supported by the different network classes.