Understanding IP Addressing

Every computer that communicates over the Internet is assigned an IP address that uniquely identifies the device and distinguishes it from other computers on the Internet.

Every computer that communicates over the Internet is assigned an IP address that uniquely identifies the device and distinguishes it from other computers on the Internet.

What is an IP Address?

An IP address is an identifier for a computer or device on a TCP/IP network. Networks using the TCP/IP protocol route messages based on the IP address of the destination.

Recommended Reading: Learn more about the TCP/IP protocol.

An IP address consists of 32 bits, often shown as 4 octets of numbers from 0-255 represented in decimal form instead of binary form. For example, the IP address: 168.212.226.204 in binary form is 10101000.11010100.11100010.11001100.

But it is easier for us to remember decimals than it is to remember binary numbers, so we use decimals to represent the IP addresses when describing them. However, the binary number is important because that will determine which class of network the IP address belongs to.

The Two Parts of an IP Address

An IP address consists of two parts, one identifying the network and one identifying the node, or host.

The Class of the address determines which part belongs to the network address and which part belongs to the node address. All nodes on a given network share the same network prefix but must have a unique host number.

Class A Network

In a Class A Network binary address start with 0, therefore the decimal number can be anywhere from 1 to 126. The first 8 bits (the first octet) identify the network and the remaining 24 bits indicate the host within the network. An example of a Class A IP address is 102.168.212.226, where “102” identifies the network and “168.212.226” identifies the host on that network.

Class B Network

In a Class B Network, binary addresses start with 10, therefore the decimal number can be anywhere from 128 to 191. The number 127 is reserved for loopback and is used for internal testing on the local machine. The first 16 bits (the first two octets) identify the network and the remaining 16 bits indicate the host within the network. An example of a Class B IP address is 168.212.226.204 where “168.212” identifies the network and “226.204” identifies the host on that network.

Class C Network

Binary addresses start with 110, therefore the decimal number can be anywhere from 192 to 223. The first 24 bits (the first three octets) identify the network and the remaining 8 bits indicate the host within the network. An example of a Class C IP address is 200.168.212.226 where “200.168.212” identifies the network and “226” identifies the host on that network.

Class D Network

In a Class D Network, binary addresses start with 1110, therefore the decimal number can be anywhere from 224 to 239. Class D networks are used to support multicasting.

Class E Network

In a Class E Network, binary addresses start with 1111, therefore the decimal number can be anywhere from 240 to 255. Class E networks are used for experimentation. They have never been documented or utilized in a standard way.

This article was originally published on June 24, 2010

Vangie Beal
Vangie Beal
Vangie Beal is a freelance business and technology writer covering Internet technologies and online business since the late '90s.

Top Articles

The Complete List of 1500+ Common Text Abbreviations & Acronyms

Text Abbreviations reviewed by Web Webster   From A3 to ZZZ we list 1,559 SMS, online chat, and text abbreviations to help you translate and understand...

How to Create a Website Shortcut on Your Desktop

Website Shortcut on Your Desktop reviewed by Web Webster   This Webopedia guide will show you how to create a website shortcut on your desktop using...

Windows Operating System History & Versions

The Windows operating system (Windows OS) refers to a family of operating systems developed by Microsoft Corporation. We look at the history of Windows...

First to Fifth Generations of Computers

Reviewed by Web Webster   Learn about each of the 5 generations of computers and major technology developments that have led to the computing devices that...

SSID (Service Set Identifier)...

Service Set Identifier (SSID) reviewed by Web Webster   SSID is short for service set...

First to Fifth Generations...

Reviewed by Web Webster   Learn about each of the 5 generations of computers and...

What Are the 7...

Reviewed by Web Webster   The phrase "7 layers of the OSI model" refers to...