Demystifying the Composition and Layout of IPv4 Addresses


In the ever-evolving landscape of the internet, where countless devices communicate seamlessly, understanding the fundamental building blocks is essential. One such fundamental element is the IPv4 address. These unique numerical identifiers play a crucial role in routing data across the World Wide Web. In this blog post, we’ll delve into the composition and layout of IPv4 addresses, unraveling the mystery behind these essential components of the internet.

What is an IPv4 Address?

IPv4, or Internet Protocol version 4, is the fourth iteration of the Internet Protocol and is the most widely used protocol for routing data across the internet. IPv4 addresses are numerical labels assigned to devices on a network. They serve as virtual street addresses, allowing data to find its way from the source to the destination.

IPv4 Address Composition:

Dotted-Decimal Notation:

IPv4 addresses are typically expressed in dotted-decimal notation, which consists of four decimal numbers separated by periods. Each of these numbers can range from 0 to 255, making up a total of 32 bits. For example, an IPv4 address might look like this:

Binary Representation:

Underneath the familiar dotted-decimal format, IPv4 addresses are composed of 32 binary bits. These bits are grouped into four octets, with each octet containing 8 bits. Understanding the binary representation can provide insights into how IPv4 addresses are structured and manipulated.

IPv4 Address Layout:

Network Portion:

In an IPv4 address, the first portion represents the network. The length of this portion can vary depending on the address’s class (Class A, B, or C) or subnetting. The network portion identifies the network to which the device belongs. For example, in the address, “192.168.1” is the network portion.

Host Portion:

The host portion of an IPv4 address identifies a specific device within the network. It is used for routing data to the correct device on the network. In the address, “1” is the host portion.

IPv4 Address Classes:

IPv4 addresses are divided into five classes: A, B, C, D, and E. Each class has a different structure, which determines the range of available addresses for networks and hosts. Classes A, B, and C are commonly used for regular networks, while D and E have specialized purposes.

Class A: These addresses have the first bit set to 0 and allow for a large number of networks, each with a vast number of hosts.

Class B: Class B addresses have the first two bits set to 10 and provide a balance between networks and hosts.

Class C: Class C addresses have the first three bits set to 110 and are suited for smaller networks with a limited number of hosts.

Subnetting and CIDR Notation:

To efficiently allocate and manage IPv4 addresses, subnetting and CIDR (Classless Inter-Domain Routing) notation are used. Subnetting allows networks to be divided into smaller subnetworks, each with its range of addresses. CIDR notation specifies both the network and host portions of an address, making it easier to define subnets and allocate addresses effectively.


Understanding the composition and layout of IPv4 addresses is essential for anyone working with networking and internet technologies. These addresses serve as the foundation for data routing on the internet and play a pivotal role in maintaining the global connectivity we rely on daily. Whether you’re a network administrator, developer, or simply a curious internet user, grasping the intricacies of IPv4 addresses is a valuable knowledge asset in today’s digital age.

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