IP address classes Which class of IP address provides the largest number of host addresses by default (before subnetting is applied)?

Introduction / Context:
Classful addressing divides IP addresses into Classes A, B, C, D, and E. Understanding the default number of host addresses available in each class is a fundamental networking concept for historical IP addressing schemes and subnetting.

Given Data / Assumptions:

• We are considering traditional classful addressing, not CIDR (Classless Inter-Domain Routing).
• Host availability is determined before subnetting.
• Class D is reserved for multicast, Class E for experimental use.

Concept / Approach:

Class A networks use an 8-bit network prefix and a 24-bit host portion, providing 2^24 – 2 usable host addresses (about 16.7 million). Class B provides 65,534 hosts, Class C provides 254 hosts. Therefore, Class A has the most hosts by default.

Step-by-Step Solution:

Verification / Alternative check:

Textbook IP addressing tables confirm these values.

Why Other Options Are Wrong:

• Class B and C: significantly fewer hosts.
• A and B combined: classes are not combined in addressing.
• Class D: reserved for multicast, not hosts.

Common Pitfalls:

• Forgetting to subtract 2 for network and broadcast addresses.
• Confusing CIDR notation with classful addressing.

Final Answer:

Class A