CREST Practitioner Security Analyst (CPSA) Practice

What is the maximum number of hosts available in a Class A network?

1. 65,536

2. 16,777,214

3. 254

4. 65,534

The correct answer is: 16,777,214

In a Class A network, the addressing scheme allows for a significant number of hosts due to the way its subnet mask is structured. Class A addresses utilize the first octet for the network identifier and the remaining three octets for host addresses. The first octet in a Class A address is designated under the range of 1 to 126, which allows for 128 theoretically possible networks (including reserved addresses). Each of these Class A networks uses a subnet mask of 255.0.0.0 (or /8), which means the first 8 bits are reserved for the network mask, leaving 24 bits available for host addresses. To calculate the maximum number of hosts per Class A network, you consider the formula 2^n - 2, where n is the number of bits available for hosts. In this case, n is 24 (from the 3 remaining octets). Therefore, 2^24 equals 16,777,216 potential addresses. However, two addresses are reserved within this range: one for the network address itself and one for the broadcast address, leading to the calculation of: 16,777,216 - 2 = 16,777,214 Thus, the maximum number of usable