Quick Answer
The answer is a /26 subnet mask (255.255.255.192) because it provides exactly 62 usable host addresses, which is the smallest subnet that meets the requirement of supporting 50 hosts. This is determined by the formula 2^(32 - subnet bits) - 2, where the subtraction of 2 accounts for the network and broadcast addresses; a /27 yields only 30 usable addresses, falling short, while a /25 offers 126, which is wasteful. On the CompTIA Network+ N10-009 exam, this question tests your ability to perform subnet mask selection for required host count, a core skill for network design scenarios. A common trap is forgetting to subtract the two reserved addresses or misapplying the power-of-two rule—always round up the host count to the next power of two (50 rounds to 64), then subtract 2 to find the needed block size. Memory tip: think “/26 gives you 62, which is plenty for 50, but /27 leaves you short with only 30.”
This N10-009 practice question tests your understanding of networking concepts. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A network administrator needs to create a subnet that supports exactly 50 hosts. Which subnet mask provides the smallest subnet that meets this requirement?
A
Why wrong: /25 provides 126 usable addresses, which is more than necessary but does not represent the smallest subnet meeting the requirement.
B
/26 provides 62 usable addresses, which is the minimum that supports 50 hosts.
C
Why wrong: /27 provides only 30 usable addresses, insufficient for 50 hosts.
D
Why wrong: /28 provides only 14 usable addresses, insufficient for 50 hosts.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
B
Option B is correct because a /26 subnet mask (255.255.255.192) provides 62 usable host addresses (2^(32-26) - 2 = 64 - 2 = 62), which is the smallest subnet that supports at least 50 hosts. A /27 would only provide 30 usable addresses, which is insufficient.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
A
Why it's wrong here
/25 provides 126 usable addresses, which is more than necessary but does not represent the smallest subnet meeting the requirement.
B
Why this is correct
/26 provides 62 usable addresses, which is the minimum that supports 50 hosts.
Related concept
Read the scenario before looking for a memorised answer.
C
Why it's wrong here
/27 provides only 30 usable addresses, insufficient for 50 hosts.
D
Why it's wrong here
/28 provides only 14 usable addresses, insufficient for 50 hosts.
Common exam traps
The trap here is that candidates often forget to subtract 2 for the network and broadcast addresses, leading them to choose a /27 (which has 32 total addresses but only 30 usable) thinking it supports 50 hosts.
Detailed technical explanation
The formula for usable hosts is 2^(32 - prefix_length) - 2, where the subtraction accounts for the network and broadcast addresses. In practice, when planning subnets, you must always consider future growth; a /26 allows for up to 62 hosts, which provides a small buffer beyond the 50-host requirement. This calculation is fundamental to IPv4 subnetting and is directly tested in the CompTIA Network+ N10-009 exam under the Networking Concepts domain.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
What to study next
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FAQ
Networking Concepts — This question tests Networking Concepts — Read the scenario before looking for a memorised answer..
The correct answer is: B — Option B is correct because a /26 subnet mask (255.255.255.192) provides 62 usable host addresses (2^(32-26) - 2 = 64 - 2 = 62), which is the smallest subnet that supports at least 50 hosts. A /27 would only provide 30 usable addresses, which is insufficient.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Same concept, more angles
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A network technician is assigned a subnet mask of 255.255.255.248. How many usable host addresses are available in this subnet?
mediumWhy A: The subnet mask 255.255.255.248 corresponds to a /29 prefix length, which provides 2^(32-29) = 8 total addresses. Subtracting the network address and broadcast address leaves 8 - 2 = 6 usable host addresses.
Last reviewed: Jun 11, 2026
This N10-009 practice question is part of Courseiva's free CompTIA 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 N10-009 exam.
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