The Five Classes of IPv4 Addresses

Learn about the five basic types of IPv4 addresses, including their ranges and intended purpose.


IP addresses are the fundamental building blocks of the internet, enabling devices to communicate with each other over networks. IPv4, the fourth version of the Internet Protocol, uses a system of classes to categorize IP addresses. In this article, we will explore the five classes of IPv4 addresses and how they function within the world of networking.

What is an IP Address?

An IP address is a numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication. It serves two main functions: identifying the host or network interface and providing the location of the host in the network.


IP Header Classes:

The IPv4 protocol defines five classes of IP addresses, which are identified by the first few bits of the address. These classes are Class A, Class B, Class C, Class D, and Class E. Each class has its own range of addresses and specific purposes.

How does an IP Address Work?

IP addresses work by providing a unique identifier to each device on a network. When data is sent over the internet, it is broken down into packets, and each packet is tagged with the source and destination IP addresses. Routers and switches then use these addresses to determine the path the data should take to reach its destination.

What is Classful Addressing?

Classful addressing is a method of IP address assignment that was used in the early days of the internet. In this system, IP addresses were divided into five classes based on their first few bits, as mentioned earlier.


Five Categories of IPv4

To gain a better understanding of IPv4, let's delve into the five major categories of IPv4 addresses.

1. Class A Addresses:

  • Range: to
  • Class A addresses have a first byte range from 1 to 126 and are used for large networks, such as the global Internet backbone. These addresses have the highest network bits and the lowest host bits, allowing for a vast number of hosts to be connected to a Class A network.
  • Each Class A address can support approximately 167 million hosts.

2. Class B Addresses:

  • Range: to
  • Class B addresses are used for medium-sized networks, like university campuses or medium-sized businesses. Their first byte range from 128 to 191 permits them to support around 65,000 hosts.
  • Class B addresses are typically used in networks that require a moderate number of hosts.

3. Class C Addresses:

  • Range: to
  • Class C addresses are for small networks, such as home networks or small offices. Their first byte range from 192 to 223 makes them suitable for networks with a limited number of hosts.
  • Each Class C address can support approximately 254 hosts.

4. Class D Addresses:

  • Range: to
  • Class D addresses are multicast addresses used to stream data to multiple receivers. They are not used to identify individual hosts or networks but rather to facilitate multicast communication.

5. Class E Addresses:

  • Range: to
  • Class E addresses are reserved for experimental purposes and are intended for future use. Currently, they are not allocated for any specific use on the Internet and are kept for potential future extensions.

Limitations of Classful IP Addressing

While classful addressing served its purpose in the early days of the internet, it had several limitations. One major issue was the inefficient allocation of IP addresses, leading to address space exhaustion. As a result, classless addressing (CIDR) was introduced to allow for more flexible and efficient allocation of IP addresses.

Rules for Assigning Network ID

ip-address.webp In classful addressing, the rules for assigning network IDs were straightforward. The class of the address determined the number of bits assigned to the network and host portions. However, with CIDR, these rules became more flexible, allowing for variable-length subnet masks and more efficient address allocation.


Understanding the five classes of IPv4 addresses and their characteristics is essential for anyone working with computer networks. While classful addressing was once the standard, CIDR has since replaced it to better accommodate the growing demands of the internet and provide more efficient IP address allocation. As the internet continues to evolve, so too does the way we manage and assign IP addresses.

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