In classful IPv4 addressing, how many networks and how many hosts per network does a Class B address support (usable hosts)?

Introduction / Context:Before Classless Inter-Domain Routing (CIDR), IPv4 addressing used fixed classes (A, B, C) with predetermined network/host bit allocations. Understanding these legacy sizes remains useful for exams and for interpreting historical network designs.

Given Data / Assumptions:

• Class B uses a 16-bit network prefix starting with 10xx at the high bits.
• Host portion comprises the remaining 16 bits.
• Usable hosts exclude the all-zeros (network) and all-ones (broadcast) host IDs.

Concept / Approach:For Class B, there are 14 variable network bits (after the fixed '10'), yielding 2^14 = 16,384 distinct networks. Each network has 16 host bits, giving 2^16 = 65,536 total addresses; subtracting 2 reserved values leaves 65,534 usable hosts per network. Options describing Class A/C quantities are included as distractors.

Step-by-Step Solution:

Verification / Alternative check:Cross-check with Class A (2^7 = 128 networks, minus reserved 0/127 historically) and Class C (2^21 networks, 2^8 - 2 = 254 hosts) to see that the provided numbers align with classful rules.

Why Other Options Are Wrong:

• 127 networks and 16,777,216 hosts: Roughly Class A host count; network count does not match Class B.
• 2,097,152 networks and 254 hosts: That is Class C networks and hosts per network.
• All of the above: Mutually inconsistent; only one can be correct.

Common Pitfalls:Forgetting to subtract network and broadcast addresses when asked for usable hosts, or confusing Class B with Class C characteristics due to the common 254-host figure.

Final Answer:16,384 networks and 65,534 nodes per network