Difficulty: Easy
Correct Answer: 8 subnets, 8,190 hosts each
Explanation:
Introduction / Context:
Mask length determines both the number of subnets and host capacity. Quickly computing these values is essential for scalable design, especially when planning allocations inside private ranges like 172.16.0.0/12 and its sub-blocks.
Given Data / Assumptions:
Concept / Approach:
Borrowed subnet bits = 19 − 16 = 3 → number of subnets = 2^3 = 8. Host bits per subnet = 32 − 19 = 13 → usable hosts = 2^13 − 2 = 8192 − 2 = 8190. These computations do not depend on classful “zero subnet” restrictions in modern CIDR practice.
Step-by-Step Solution:
Compute subnet count: 2^(borrowed) = 2^3 = 8.Compute host bits: 32 − 19 = 13.Compute usable hosts: 2^13 − 2 = 8190.Report as “8 subnets, 8,190 hosts each.”
Verification / Alternative check:
Block size per subnet in the third octet is 256 − 224 = 32; subnets progress 0, 32, 64, … which corroborates 8 distinct subnets across the /16 space (256/32 = 8).
Why Other Options Are Wrong:
Common Pitfalls:
Mixing classful defaults with CIDR arithmetic or forgetting to subtract 2 for network and broadcast when host addressing is required.
Final Answer:
8 subnets, 8,190 hosts each
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