CREST Practitioner Security Analyst (CPSA) Practice 2025 - Free CPSA Practice Questions and Study Guide

Classful addressing is a method used in networking to define the structure of IP addresses. In this system, different classes are distinguished by their leading bits in binary representation, which helps to categorize networks based on size and usage.

Class A addresses start with a binary '0' in the first bit. This corresponds to IP addresses ranging from 1.0.0.0 to 126.0.0.0 in decimal notation, allowing for a large number of hosts on each network. The structure of Class A implies that the first octet (the first eight bits of the IP address) is utilized to identify the network, while the remaining three octets are available for host addresses within that network. This results in a significant capability to support vast networks with many individual devices.

In contrast, the other classes, such as B, C, and D, begin with different leading bits. Class B starts with '10', Class C with '110', and Class D with '1110'. This differentiation in the first bits allows for varied allocations of addresses across the classes, catering to different needs; Class B serves medium-sized networks, Class C is for smaller networks, and Class D is utilized for multicast addresses.

Understanding these classifications and their binary representations