Q1. Explain the following in detail

a) IPv4 Classful Addressing

Introduction

IPv4 classful addressing is a network addressing architecture used in the early Internet, where IP addresses were divided into fixed classes based on the first few bits of the address. It was used from 1981 to 1993.

Definition

Classful addressing divides the 32-bit IPv4 address space into five classes (A, B, C, D, E) where each class has a fixed network and host portion. Classes A, B, and C are used for unicast addressing, Class D for multicast, and Class E for experimental purposes.

Classes Overview

• Class A: First bit = 0, Range: 0.0.0.0 to 127.255.255.255, Default mask: /8 (255.0.0.0), Used for large networks
• Class B: First bits = 10, Range: 128.0.0.0 to 191.255.255.255, Default mask: /16 (255.255.0.0), Used for medium networks
• Class C: First bits = 110, Range: 192.0.0.0 to 223.255.255.255, Default mask: /24 (255.255.255.0), Used for small networks
• Class D: First bits = 1110, Range: 224.0.0.0 to 239.255.255.255, Used for multicasting
• Class E: First bits = 1111, Range: 240.0.0.0 to 255.255.255.255, Reserved for experimental use

Example

IP address 150.200.15.10 belongs to Class B because the first octet (150) falls in the range 128-191. The default subnet mask is 255.255.255.0, meaning the first 16 bits represent the network and the last 16 bits represent hosts.

Limitations

Classful addressing led to inefficient use of IP addresses and wastage of address space, which led to the development of classless addressing (CIDR).

b) IPv4 Classless Addressing

Introduction

IPv4 classless addressing, also known as CIDR (Classless Inter-Domain Routing), was introduced in 1993 to overcome the limitations of classful addressing. It allows for flexible allocation of IP addresses.