IPv4 Addresses: structure & classes & methods

In the world of networking, IP Version 4 (IPv4) addresses serve as the foundation for the internet’s infrastructure. Every device connected to the internet, from smartphones to servers, relies on IPv4 addresses to identify and communicate with each other. In this comprehensive guide, we will explore the ins and outs of IPv4 addresses, explaining what they are, how they are structured, and their significance in the realm of internet communication.

What is an IPv4 Address?

An IPv4 address is a unique numerical label assigned to every device connected to an internet protocol (IP) network. It acts as a virtual address, allowing devices to send and receive data across the internet. An IPv4 address consists of four sets of numbers, each ranging from 0 to 255, separated by periods (e.g., These addresses are 32 bits long and can provide approximately 4.3 billion unique combinations.

Structure of IPv4 Addresses

The structure of an IPv4 address comprises two main components: the network portion and the host portion. The network portion represents the network to which the device is connected, while the host portion represents the specific device within that network. The division between the network and host portions is determined by a subnet mask, which helps identify the size of the network.

Classes of IPv4 Addresses

IPv4 addresses are categorized into different classes, namely A, B, C, D, and E, based on the size of the network and the number of hosts they can accommodate. Here’s a brief overview:

  • Class A addresses: These addresses have their first bit set to 0 and can support a large number of networks with a large number of hosts per network.
  • Class B addresses: The first two bits of class B addresses are set to 10. They can support a moderate number of networks, with a significant number of hosts per network.
  • Class C addresses: Class C addresses have their first three bits set to 110. They can accommodate a large number of networks but have a smaller number of hosts per network compared to class A and B.
  • Class D addresses: These addresses are reserved for multicast purposes, allowing data to be sent to a group of devices simultaneously.
  • Class E addresses: Reserved for experimental purposes, class E addresses are not intended for regular use.

IP Address Assignment Methods

IPv4 addresses can be assigned to devices using various methods, including:

  • Static IP addressing: In this method, an administrator manually assigns a specific IP address to a device. It ensures that the device always has the same IP address, making it easier to manage and track.
  • Dynamic IP addressing: Dynamic Host Configuration Protocol (DHCP) is commonly used to dynamically assign IP addresses to devices on a network. DHCP servers automatically allocate available IP addresses to devices when they connect to the network.

Challenges with IPv4 Addresses and the Transition to IPv6

As the number of internet-connected devices continues to grow rapidly, the limitations of IPv4 addresses have become apparent. The main challenge is the depletion of available IPv4 addresses due to their finite nature. To address this, IPv6 (Internet Protocol Version 6) was introduced, offering a significantly larger address space and enhanced features. The transition from IPv4 to IPv6 is an ongoing process to accommodate the ever-expanding internet ecosystem.


IPv4 addresses are the backbone of internet communication, providing a unique identifier to every device connected to an IP network. Understanding the structure, classes, and assignment methods of IPv4 addresses is crucial for network administrators and individuals working in the field of networking. As the world becomes increasingly connected, the transition to IPv6 is essential to ensure the continued growth and scalability of the internet.