IPv4

Overview

IPv4 (Internet Protocol version 4) is the fourth version of the Internet Protocol (IP) and the most widely used to identify devices on a network and route traffic across the internet. It is based on a 32-bit address system, allowing for around 4.3 billion unique addresses.

Key Features of IPv4:

• Address Length: 32-bit address.
• Address Notation: Written in dotted decimal notation (e.g., 192.168.1.1).
• Supports Broadcast: IPv4 allows for broadcasting to communicate with all devices on a local network.
• Dynamic Addressing: Uses DHCP (Dynamic Host Configuration Protocol) to dynamically assign IP addresses to devices.
• Limited Security: IPv4 was designed without inherent security features, although security protocols such as IPSec can be added.

Structure of IPv4 Address:

An IPv4 address consists of four octets (or bytes), separated by periods. Each octet is represented as a decimal number between 0 and 255.

Example: 192.168.1.1

• Binary Representation: Each octet in decimal is converted to an 8-bit binary number.
  • Example: 192.168.1.1 in binary is 11000000.10101000.00000001.00000001.

IPv4 Address Classes:

IPv4 addresses are divided into five classes based on their range and usage:

Class	Range (First Octet)	Purpose
A	0 - 127	Large networks
B	128 - 191	Medium-sized networks
C	192 - 223	Small networks
D	224 - 239	Multicast groups
E	240 - 255	Experimental use

Private Address Ranges:

Certain IPv4 addresses are reserved for private networks and are not routable on the public internet:

• 10.0.0.0 – 10.255.255.255 (10.0.0.0/8)
• 172.16.0.0 – 172.31.255.255 (172.16.0.0/12)
• 192.168.0.0 – 192.168.255.255 (192.168.0.0/16)

Subnetting:

Subnetting allows the division of a large network into smaller, manageable sub-networks (subnets). A subnet mask helps distinguish between the network portion and the host portion of an IP address.

• Example: The subnet mask 255.255.255.0 applied to an IPv4 address breaks it into 24 bits for the network ID and 8 bits for the host ID.

IPv4 Limitations:

• Limited Address Space: Only around 4.3 billion addresses are available, leading to address exhaustion.
• No Built-in Security: IPv4 was not designed with security features, though IPSec can be added externally.
• Broadcasting: Broadcasting can lead to inefficiencies and increased network traffic.

Transition to IPv6:

Due to the exhaustion of IPv4 addresses, IPv6 was developed. However, IPv4 is still in widespread use, with many networks implementing dual-stack solutions to support both protocols during the transition.

IPv4 remains foundational to internet communication despite the move towards IPv6 for better scalability and security.