Quick Answer
The answer is a /28 subnet mask, which provides exactly 14 usable host addresses. This is correct because a /28 mask (255.255.255.240) allocates 4 bits for host addresses, yielding 2⁴ = 16 total addresses per subnet; after reserving the network and broadcast addresses, 14 remain usable. When you calculate subnet mask for required host count, you must always subtract two from the total block size to account for these reserved addresses. On the CompTIA Network+ N10-009 exam, this concept tests your ability to match subnet masks to specific host requirements, often appearing in scenario-based questions where the trick is to avoid choosing a mask that provides too many or too few addresses. A common trap is selecting a /29 (which gives only 6 usable hosts) because it seems close, but it fails the minimum of 10 hosts. For a quick memory tip, remember the formula: 2ⁿ – 2 ≥ required hosts, then n is the number of host bits; for 10 hosts, n=4 gives 14 usable, so the mask is /32–4 = /28.
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 engineer is designing a subnet that can support at least 10 hosts. Which subnet mask would provide exactly 14 usable host addresses?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "least"
Why it matters: You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
/27
Why wrong: /27 gives 2^(32-27)-2 = 30 usable hosts, more than needed but not exactly 14.
/28
Correct. /28 gives 2^(32-28)-2 = 14 usable hosts, satisfying the requirement of at least 10 and exactly 14.
/29
Why wrong: /29 gives 6 usable hosts, which is less than 10.
/30
Why wrong: /30 gives 2 usable hosts, far less than 10.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
/28
A /28 subnet mask (255.255.255.240) provides 16 total addresses per subnet. Subtracting the network address and broadcast address leaves 14 usable host addresses, which exactly meets the requirement of at least 10 hosts.
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.
/27
Why it's wrong here
/27 gives 2^(32-27)-2 = 30 usable hosts, more than needed but not exactly 14.
/28
Why this is correct
Correct. /28 gives 2^(32-28)-2 = 14 usable hosts, satisfying the requirement of at least 10 and exactly 14.
Clue confirmation
The clue word "least" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
/29
Why it's wrong here
/29 gives 6 usable hosts, which is less than 10.
/30
Why it's wrong here
/30 gives 2 usable hosts, far less than 10.
Common exam traps
Cisco often tests the distinction between total addresses and usable addresses, where candidates forget to subtract the network and broadcast addresses, leading them to incorrectly select /29 (8 total addresses) thinking it supports 8 hosts.
Detailed technical explanation
The number of usable hosts per subnet is calculated as 2^(32 - prefix_length) - 2. For /28, this is 2^4 - 2 = 14. In real-world scenarios, engineers must carefully choose subnet masks to avoid wasting IP addresses, especially in VLSM (Variable Length Subnet Mask) designs where efficient address allocation is critical for minimizing routing table entries and conserving address space.
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
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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: /28 — A /28 subnet mask (255.255.255.240) provides 16 total addresses per subnet. Subtracting the network address and broadcast address leaves 14 usable host addresses, which exactly meets the requirement of at least 10 hosts.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "least". You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
Read the scenario before looking for a memorised answer.
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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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