- A
/27
Why wrong: /27 gives 2^(32-27)-2 = 30 usable hosts, more than needed but not exactly 14.
- B
/28
Correct. /28 gives 2^(32-28)-2 = 14 usable hosts, satisfying the requirement of at least 10 and exactly 14.
- C
/29
Why wrong: /29 gives 6 usable hosts, which is less than 10.
- D
/30
Why wrong: /30 gives 2 usable hosts, far less than 10.
Question 96 of 520
N10-009 Networking Concepts Practice Question
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.
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
✓
/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
Option-by-option breakdown
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.
When this WOULD be correct
A question asking for a subnet that supports at least 10 hosts but also allows for future growth, or one that asks for the smallest subnet supporting at least 14 hosts (since /27 supports 30, it would be correct if the requirement were 'at least 14' without the exactness).
- ✓
/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.
When this WOULD be correct
This option would be correct for a question asking for a subnet that supports exactly 6 usable hosts, such as a point-to-multipoint link with a few devices.
- ✗
/30
Why it's wrong here
/30 gives 2 usable hosts, far less than 10.
When this WOULD be correct
This option would be correct for a point-to-point link requiring exactly 2 usable host addresses, such as a WAN connection between two routers.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The N10-009 exam frequently reuses these exact scenarios with slightly different constraints.
✓/28Correct answer▾
Why this is correct
Correct. /28 gives 2^(32-28)-2 = 14 usable hosts, satisfying the requirement of at least 10 and exactly 14.
✗/27Wrong answer — click to see why▾
Why this is wrong here
/27 provides 30 usable addresses (2^(32-27)-2 = 30), which exceeds the requirement of exactly 14 usable addresses. The question specifies 'exactly 14 usable host addresses', so /27 is too large.
★ When this WOULD be the correct answer
A question asking for a subnet that supports at least 10 hosts but also allows for future growth, or one that asks for the smallest subnet supporting at least 14 hosts (since /27 supports 30, it would be correct if the requirement were 'at least 14' without the exactness).
Why candidates choose this
Candidates often misremember the host formula or think /27 is the smallest subnet that supports 10 hosts, not realizing /28 also works and is more precise for the exact count.
✗/29Wrong answer — click to see why▾
Why this is wrong here
A /29 subnet mask provides only 6 usable host addresses (2^(32-29)-2 = 6), which is fewer than the required 10 hosts.
★ When this WOULD be the correct answer
This option would be correct for a question asking for a subnet that supports exactly 6 usable hosts, such as a point-to-multipoint link with a few devices.
Why candidates choose this
Candidates may mistakenly calculate 2^(32-29) = 8 and forget to subtract 2 for network and broadcast addresses, or they may confuse the number of hosts with the number of addresses.
✗/30Wrong answer — click to see why▾
Why this is wrong here
A /30 subnet provides only 2 usable host addresses (2^2 - 2 = 2), which is insufficient for the requirement of at least 10 hosts.
★ When this WOULD be the correct answer
This option would be correct for a point-to-point link requiring exactly 2 usable host addresses, such as a WAN connection between two routers.
Why candidates choose this
Candidates may confuse the number of host bits with usable hosts, or mistakenly think /30 provides 14 usable addresses due to misremembering the formula.
Analysis generated from the official N10-009blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
The N10-009 exam 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
How to think about this question
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.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
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.
Visual reference
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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Learn the concepts, then practise the questions
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FAQ
Questions learners often ask
What does this N10-009 question test?
Networking Concepts — This question tests Networking Concepts — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
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.
What should I do if I get this N10-009 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "least". You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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Last reviewed: Jun 11, 2026
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