IP addressing

IP addressing
9.2.1 This page will describe IP addressing.


For any two systems to communicate, they must be able to identify and locate each other. The addresses in Figure are not actual network addresses. They represent and show the concept of address grouping.

A computer may be connected to more than one network. In this situation, the system must be given more than one address. Each address will identify the connection of the computer to a different network. Each connection point, or interface, on a device has an address to a network. This will allow other computers to locate the device on that particular network. The combination of the network address and the host address creates a unique address for each device on a network. Each computer in a TCP/IP network must be given a unique identifier, or IP address. This address, which operates at Layer 3, allows one computer to locate another computer on a network. All computers also have a unique physical address, which is known as a MAC address. These are assigned by the manufacturer of the NIC. MAC addresses operate at Layer 2 of the OSI model.

An IP address is a 32-bit sequence of ones and zeros. Figure shows a sample 32-bit number. To make the IP address easier to work with, it is usually written as four decimal numbers separated by periods. For example, an IP address of one computer is 192.168.1.2. Another computer might have the address 128.10.2.1. This is called the dotted decimal format. Each part of the address is called an octet because it is made up of eight binary digits. For example, the IP address 192.168.1.8 would be 11000000.10101000.00000001.00001000 in binary notation. The dotted decimal notation is an easier method to understand than the binary ones and zeros method. This dotted decimal notation also prevents a large number of transposition errors that would result if only the binary numbers were used.

Both the binary and decimal numbers in Figure represent the same values. However, the address is easier to understand in dotted decimal notation. This is one of the common problems associated with binary numbers. The long strings of repeated ones and zeros make errors more likely.

It is easy to see the relationship between the numbers 192.168.1.8 and 192.168.1.9. The binary values 11000000.10101000.00000001.00001000 and 11000000.10101000.00000001.00001001 are not as easy to recognize. It is more difficult to determine that the binary values are consecutive numbers.

The next page will discuss the conversion of binary and decimal numbers.