IP Address Class Ranges Explained

Understanding IP address class ranges is fundamental to networking and internet communications. Whether you are managing cloud servers, dedicated servers, or web hosting with Go4hosting, knowing how IP addresses are structured helps you design efficient networks, allocate IP resources, and troubleshoot connectivity issues.

This knowledgebase article breaks down what IP address classes are, their ranges, characteristics, and how they are used in network design.

What Is an IP Address?

An IP address (Internet Protocol address) is a unique identifier assigned to every device connected to a network that uses the Internet Protocol for communication. It allows devices to locate and communicate with each other over the internet or local networks.

IP addresses are written as four numbers separated by dots, known as IPv4 addresses, for example:

CopyEdit

192.168.1.1

Each number ranges from 0 to 255 and represents 8 bits (a byte), making the entire IPv4 address 32 bits long.

Why IP Address Classes?

In the early days of the internet, IP addresses were divided into classes to simplify routing and address allocation. The classful addressing system bulk IP addresses into fixed-size blocks, each designed for networks of different sizes.

Though today the internet mostly uses Classless Inter-Domain Routing (CIDR), understanding the original IP address classes remains important for:

• Understanding legacy systems.
  

• Managing private networks.
  

• Configuring subnet masks and IP ranges.
  

The Five IP Address Classes

IP addresses are divided into five classes based on their leading bits and address ranges:

Let's explore each class in detail.

Class A IP Addresses

• Range: 0.0.0.0 to 127.255.255.255
  

• Leading bit pattern: 0xxx xxxx
  

• Default subnet mask: 255.0.0.0 or /8
  

• Network/Host split: First 8 bits for the network, remaining 24 bits for hosts.
  

Characteristics:

• Designed for extremely large networks.
  

• Allows for 128 networks (0 to 127).
  

• Each network can support over 16 million hosts (2^24 - 2).
  

• The first octet identifies the network, and the remaining three octets identify hosts.
  

• The IP address 127.0.0.1 is reserved for localhost (loopback).
  

Example:

• Network address: 10.0.0.0
  

• Host IPs: 10.0.0.1 to 10.255.255.254
  

• Broadcast: 10.255.255.255
  

Use cases:

• Large organizations or ISPs.
  

• Private Class A network range: 10.0.0.0 - 10.255.255.255 (RFC 1918).
  

Class B IP Addresses

• Range: 128.0.0.0 to 191.255.255.255
  

• Leading bits: 10xx xxxx
  

• Default subnet mask: 255.255.0.0 or /16
  

• Network/Host split: First 16 bits for the network, 16 bits for hosts.
  

Characteristics:

• Suitable for medium-sized networks.
  

• Allows for 16,384 networks.
  

• Each network can support up to 65,534 hosts (2^16 - 2).
  

• First two octets define the network, last two define hosts.
  

Example:

• Network address: 172.16.0.0
  

• Host IPs: 172.16.0.1 to 172.16.255.254
  

• Broadcast: 172.16.255.255
  

Use cases:

• Universities, medium-sized businesses.
  

• Private Class B network range: 172.16.0.0 - 172.31.255.255 (RFC 1918).
  

Class C IP Addresses

• Range: 192.0.0.0 to 223.255.255.255
  

• Leading bits: 110x xxxx
  

• Default subnet mask: 255.255.255.0 or /24
  

• Network/Host split: First 24 bits network, last 8 bits host.
  

Characteristics:

• Designed for small networks.
  

• Supports up to 2 million networks.
  

• Each network can support up to 254 hosts (2^8 - 2).
  

• First three octets define the network; the last octet defines hosts.
  

Example:

• Network address: 192.168.1.0
  

• Host IPs: 192.168.1.1 to 192.168.1.254
  

• Broadcast: 192.168.1.255
  

Use cases:

• Small businesses and home networks.
  

• Private Class C range: 192.168.0.0 - 192.168.255.255 (RFC 1918).
  

Class D IP Addresses - Multicast

• Range: 224.0.0.0 to 239.255.255.255
  

• Leading bits: 1110 xxxx
  

• Purpose: Not assigned to individual hosts but used for multicast groups.
  

Characteristics:

• Multicast allows a single packet to be sent to multiple destinations.
  

• Used in streaming media, conferencing, and real-time data feeds.
  

Class E IP Addresses - Experimental

• Range: 240.0.0.0 to 255.255.255.255
  

• Leading bits: 1111 xxxx
  

• Purpose: Reserved for experimental or future use, not generally used in public networks.
  

Reserved IP Ranges and Special Addresses

• 127.0.0.0/8 - Loopback addresses (localhost).
  

• Private IP ranges (RFC 1918):
  

• Class A: 10.0.0.0/8
  

• Class B: 172.16.0.0 - 172.31.255.255
  

• Class C: 192.168.0.0/16
  

• Link-local addresses: 169.254.0.0/16 (used for auto-IP when DHCP fails).
  

• Broadcast address: Used to communicate with all devices on a subnet.
  

How IP Classes Affect Network Design

IP address classes were designed to help network administrators assign addresses based on organization size:

• Class A: Large networks needing millions of IPs.
  

• Class B: Medium networks with thousands of hosts.
  

• Class C: Small networks with fewer than 255 devices.
  

Today, CIDR allows for flexible allocation beyond class boundaries, but understanding classes aids in subnetting and addressing schemes.

IP Address Classes and Subnet Masks

Subnet masks define which portion of the IP address is the network and which is the host.

• Class A default: 255.0.0.0 --> Network: 8 bits, Host: 24 bits
  

• Class B default: 255.255.0.0 --> Network: 16 bits, Host: 16 bits
  

• Class C default: 255.255.255.0 --> Network: 24 bits, Host: 8 bits
  

Subnetting divides networks into smaller parts, increasing efficiency and security.

Example: Calculating Network and Host Ranges for Class C

Consider IP: 192.168.10.0 with subnet mask 255.255.255.0:

• Network portion: 192.168.10
  

• Host portion: Last octet (0-255)
  

• Usable host IPs: 192.168.10.1 to 192.168.10.254
  

• Broadcast address: 192.168.10.255
  

Why You Need to Know IP Address Classes for Go4hosting Services

Whether you're provisioning a Cloud VPS, configuring a dedicated server, or setting up managed hosting with Go4hosting:

• Understanding IP classes helps with IP allocation.
  

• Helps configure network interfaces correctly.
  

• Useful when setting up firewalls and routing rules.
  

• Aids in planning private and public IP address usage.
  

Conclusion

IP address classes provide a foundational framework for understanding network architecture. Despite the rise of CIDR, the legacy class system remains relevant in various network scenarios.

Here's a quick recap:

• Class A: Large networks, 0-127 first octet.
  

• Class B: Medium networks, 128-191 first octet.
  

• Class C: Small networks, 192-223 first octet.
  

• Class D: Multicast.
  

• Class E: Experimental.
  

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