What is an IPv4 address?

  • IPv4 stands for Internet Protocol version 4 and is a numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication.
  • An IPv4 address is a 32-bit number typically expressed in four decimal numbers separated by periods. Each decimal number represents 8 bits, resulting in a total of four octets.
  • IPv4 addresses are used to identify and locate devices on a network, enabling data packets to be routed across the Internet to their intended destination.

At the heart of the internet’s connectivity lies the Internet Protocol (IP) address, a numerical label that facilitates the exchange of data between devices on a network. Among the various iterations of IP addresses, IPv4 stands as a cornerstone, providing a foundational framework for network communication.

The anatomy of IPv4 addresses

IPv4 addresses are composed of 32 bits, segmented into four octets of eight bits each. These octets are expressed in decimal form, with each octet representing a number from 0 to 255. For example, an IPv4 address might appear as

Every device connected to a network is assigned a unique IPv4 address. This address serves as a distinct identifier, allowing devices to be located and communicated with across the Internet.

IPv4 addresses follow a hierarchical addressing scheme. The first portion of the address identifies the network to which the device belongs, while the remaining bits specify the individual device within that network. This hierarchical structure facilitates efficient routing of data packets across networks.

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IPv4 classification

There are five categories of IPv4 addresses: A, B, C, D, and E, each with its own range of IP addresses.

Class A: This class spans from to, with the first bit being 0. It is tailored for large networks, with 8 bits allocated for the network and 24 bits for hosts.

Class B: Ranging from to, Class B addresses start with the first two bits set to 10. They are suitable for medium to large networks, offering 16 bits for hosts and 16 bits for the network.

Class C: Reserved for small local area networks (LANs), Class C addresses range from to The network in this class is identified using three octets, providing 24 network bits and 8 host bits.

Class D: Used exclusively for multicasting purposes, Class D addresses have the first three bits set to “1” and the fourth bit as “0”. They consist of 32-bit network addresses but are not employed for standard networking functions.

Class E: Intended for experimental or research purposes, Class E addresses cover the range from to The first four bits of a Class E IP address are set to one in binary format.

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The role and challenges of IPv4 addresses

IPv4 addresses play a fundamental role in facilitating communication between devices on a network and beyond. When a device sends data over the Internet, it is segmented into packets, each tagged with the destination IPv4 address. These packets traverse various networks based on their destination address until they reach their intended recipient. Without IPv4 addresses, the seamless exchange of data across the Internet would be impossible, hindering the global connectivity that defines the digital age.

Despite their critical importance, IPv4 addresses face several challenges and limitations in today’s digital landscape. The most pressing issue is the depletion of available IPv4 addresses due to the exponential growth of Internet-connected devices. With the pool of IPv4 addresses nearing exhaustion, the transition to IPv6 has become imperative. IPv6 offers a significantly larger address space, capable of accommodating the expanding array of devices in the Internet of Things (IoT) era.


Lydia Luo

Lydia Luo, an intern reporter at BTW media dedicated in IT infrastructure. She graduated from Shanghai University of International Business and Economics. Send tips to j.y.luo@btw.media.

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