The world of networking relies heavily on IP addresses, particularly IPv4 addresses. These unique numerical labels enable devices to communicate and navigate the vast landscape of the internet. In this article, we will explore the distinctions between private and public IPv4 addresses, delve into IP classes, and even provide a formula to calculate network addresses.

Understanding IPv4 Addresses

IPv4, or Internet Protocol version 4, uses 32-bit addresses, represented as four octets separated by periods (e.g., Each octet can have values ranging from 0 to 255, making for a total of 4,294,967,296 possible IPv4 addresses. This seemingly vast address space was quickly exhausted, leading to the development and adoption of IPv6, but IPv4 is still widely used today.

Private vs. Public IPv4 Addresses

Public IPv4 Addresses: These are globally unique addresses assigned by Internet Service Providers (ISPs) to devices directly connected to the internet. Public IP addresses allow devices to communicate with other devices across the internet. They are, in essence, the “public” face of your network.

Private IPv4 Addresses: Private IP addresses are used within a local network, such as your home or office network. They allow devices within the same network to communicate with each other but are not directly accessible from the internet. Private IP addresses are reserved and can be reused across different local networks.

IP Classes

IPv4 addresses are divided into five classes: A, B, C, D, and E. Each class has a specific range of addresses and is used for different purposes:

  1. Class A ( to Typically used for large networks, with the first octet representing the network and the remaining three octets for hosts. This class can support over 16 million hosts on a single network.
  2. Class B ( to Suitable for medium-sized networks, with the first two octets reserved for the network and the other two for hosts. This class can accommodate up to 65,000 hosts per network.
  3. Class C ( to Ideal for smaller networks, with the first three octets used for the network and only one octet for hosts. Class C can support up to 254 hosts per network.
  4. Class D ( to Reserved for multicast groups, often used for multimedia streaming or routing protocols.
  5. Class E ( to Reserved for experimental purposes and not intended for general use.

Calculating Network Addresses

Calculating network addresses, specifically for Class A, B, and C IP addresses, follows a formula:


  • Network Address: Obtained by setting all host bits to 0 in the host portion of the IP address.
  • Broadcast Address: Obtained by setting all host bits to 1 in the host portion of the IP address.

For Class A, B, and C addresses:

  • Subnet Mask: The subnet mask defines the network portion of the address. It consists of consecutive 1s followed by consecutive 0s. For example, a subnet mask of means that the first 24 bits (the first three octets) are the network portion, and the last 8 bits (the last octet) are for hosts.

Let’s calculate a network address using an example:

IP Address: Subnet Mask:

Using the formula, we set the host bits to 0:

Network Address =

This is the network address for devices within the same network segment.


IPv4 addresses are the foundation of internet communication, enabling devices to find and communicate with one another. Understanding the distinctions between public and private IP addresses, the classes of IPv4 addresses, and how to calculate network addresses is fundamental for network administrators and developers. While IPv6 adoption is on the rise, IPv4 remains a crucial component of the modern internet, making this knowledge valuable for anyone working with networks or the internet.

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