200-901 Network Fundamentals Practice Question
A network administrator is configuring a new subnet for a branch office that requires 50 usable host addresses. The corporate network uses the 192.168.10.0/24 block. Which subnet mask should be used to meet the requirement with minimal waste?
⚠ Common exam trap
The trap here is that candidates often forget to subtract the two reserved addresses (network and broadcast) from the total host count, leading them to incorrectly select a /27 mask (which has 32 total addresses but only 30 usable) thinking it is sufficient for 50 hosts.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
255.255.255.192 (/26)
A /26 subnet mask (255.255.255.192) provides 2^(32-26) = 64 total addresses, of which 62 are usable (subtracting network and broadcast addresses). This meets the requirement of 50 usable hosts with minimal waste, as the next smaller mask (/27) only offers 30 usable addresses, which is insufficient.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
255.255.255.128 (/25)
Why it's wrong here
A /25 mask yields 126 usable hosts, leaving 76 addresses unused for a 50-host requirement. It would be correct for a segment needing between 51 and 126 hosts, but here it wastes half the address space.
- ✗
255.255.255.0 (/24)
Why it's wrong here
A /24 mask yields 254 usable hosts, wasting over 200 addresses against the 50-host requirement. It is tempting because /24 aligns neatly with the existing 192.168.10.0/24 block, and would be correct if the branch needed a full Class C-sized segment rather than a minimal-waste allocation.
- ✓
255.255.255.192 (/26)
Why this is correct
A /26 mask yields 64 addresses, leaving 62 usable hosts after reserving network and broadcast addresses, which satisfies the 50-host requirement with minimal waste. A /27 would provide only 30 usable hosts, insufficient here, while a /25 wastes 126 addresses.
- ✗
255.255.255.224 (/27)
Why it's wrong here
A /27 yields 30 usable hosts, short of the 50 required, so the subnet is undersized. It is tempting because /27 is the classic answer for roughly 30-host segments, and would be correct if the branch needed about 25 to 30 addresses.
Visual reference
About these practice questions
Courseiva writes every 200-901 question from scratch — 975 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-901 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-901 exam.