---
title: "IPv4 Address Ranges: Classes, Private vs Public, CIDR"
url: "https://astraguardvpn.com/blog/ipv4-address-ranges-classes-private-vs-public-cidr"
description: "Learn IPv4 classes A, B, C, private vs public addresses, and CIDR basics in this comprehensive guide."
updated: "2026-06-28T09:00:08.199Z"
---

# IPv4 Address Ranges: Classes, Private vs Public, CIDR

Understand IPv4 address classes, private vs public ranges, and CIDR notation with this clear guide.

Understanding IPv4 Address Classes When delving into networking, it’s crucial to grasp how IPv4 address classes are organized. IPv4 stands for Internet Protocol version 4, a system that assigns unique addresses to devices on a network. These addresses are divided into classes, primarily A, B, and C, to streamline network design. Class A addresses range from 1.0.0.0 to 126.0.0.0. They are designed for large networks with a small number of networks but a vast number of hosts. Class B addresses span from 128.0.0.0 to 191.255.0.0, suitable for medium-sized networks. Finally, Class C addresses range from 192.0.0.0 to 223.255.255.0, perfect for smaller networks. Private vs Public IPv4 Addresses IPv4 addresses can be either private or public. Public IP addresses are globally unique and used to identify devices on the internet. Private IP addresses, however, are used within a network and not routable on the internet. The private ranges for each class are defined as follows: - Class A: 10.0.0.0 to 10.255.255.255 - Class B: 172.16.0.0 to 172.31.255.255 - Class C: 192.168.0.0 to 192.168.255.255 These private ranges are defined by RFC 1918 and are used for local communications within a private network. CIDR Notation Basics CIDR, or Classless Inter-Domain Routing, is a method for allocating IP addresses more flexibly than the traditional class-based system. CIDR notation includes a suffix, such as /24, which indicates the number of bits used for the network portion of the address. For example, an IP address in CIDR notation might look like 192.168.1.0/24. Here, /24 means the first 24 bits are used for the network part, leaving 8 bits for host addresses. This allows for subnetting, dividing a large network into smaller, manageable segments. Before You Start To understand and work with IPv4 addresses, you need: 1. Basic networking knowledge. 2. Access to network configuration tools. 3. Understanding of binary and decimal conversions. Be careful when configuring network addresses, as incorrect setups can lead to connectivity issues. Practical Example To further understand these concepts, let’s apply them in a practical scenario of setting up a home network with a router. 1. Log into your router’s settings page. This usually involves entering the router’s IP address in a web browser. 2. Navigate to the network settings. Remember, menu names may vary, so check your router’s manual or online help for guidance. 3. Assign a private IP address to each device in your network from the Class C private range (e.g., 192.168.1.2). 4. Configure the subnet mask. For a typical home network, a /24 subnet mask (255.255.255.0) is common. 5. Save your settings and restart your router if necessary. Key Takeaways • IPv4 addresses are divided into Classes A, B, and C. • Public IPs are used on the internet, private IPs within a network. • CIDR notation allows flexible IP address allocation and subnetting. • Understanding of these concepts is crucial for effective network management. FAQ Q: What is the main difference between private and public IP addresses? A: Private IPs are used within a local network, while public IPs are routable on the internet. Q: How many hosts can a Class C network support? A: A Class C network can support up to 254 hosts. Q: Why is CIDR important? A: CIDR allows for more efficient IP address allocation and supports subnetting. Q: Can I convert a public IP to private? A: No, public IPs are assigned by ISPs and cannot be converted to private by users.

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