The correct subnet mask is /26, or 255.255.255.192, because it provides exactly 62 usable host addresses per subnet, which satisfies the requirement of at least 50 hosts while minimizing wasted addresses. This works because a /26 borrows 2 bits from the host portion of a /24 network, yielding 2^(32-26) - 2 = 62 usable hosts per subnet, and it allows you to create four equal-sized subnets from the original 192.168.1.0/24 block. On the CompTIA Network+ N10-009 exam, this type of subnet mask calculation tests your ability to balance host capacity with subnet count—a common trap is choosing a /25 (126 hosts) which wastes addresses, or a /27 (30 hosts) which doesn’t meet the 50-host requirement. A quick memory tip: for 50 hosts, think “/26 gives 62, just enough to spare a dozen,” and remember that the magic number for a /26 is 64 (the block size), so subnets start at 0, 64, 128, and 192.
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. A key principle to apply: a /26 subnet mask borrows 2 bits from the host portion of a /24 network.. 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 needs to create subnets for four departments, each requiring at least 50 host addresses. The available network is 192.168.1.0/24. Which subnet mask should be used to satisfy the requirements while minimizing wasted 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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
/26 (255.255.255.192)
A /26 subnet mask (255.255.255.192) provides 62 usable host addresses per subnet (2^(32-26) - 2 = 62), which meets the requirement of at least 50 hosts per department. With a /24 network, you can create exactly four /26 subnets (192.168.1.0/26, 192.168.1.64/26, 192.168.1.128/26, 192.168.1.192/26), perfectly matching the four departments while minimizing wasted addresses.
Key principle: A /26 subnet mask borrows 2 bits from the host portion of a /24 network.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
/26 (255.255.255.192)
Why this is correct
Correct. /26 provides 4 subnets with 62 usable hosts each, fitting the need for 50 hosts per department.
Clue confirmation
The clue word "least" in the question point toward this answer.
Related concept
A /26 subnet mask borrows 2 bits from the host portion of a /24 network.
✗
/25 (255.255.255.128)
Why it's wrong here
/25 provides only 2 subnets (126 usable hosts each), which is insufficient as the engineer needs 4 subnets.
✗
/27 (255.255.255.224)
Why it's wrong here
/27 provides 8 subnets, but each subnet has only 30 usable hosts, which is below the 50 host requirement.
✗
/24 (255.255.255.0)
Why it's wrong here
/24 provides only 1 subnet with 254 usable hosts, which does not fulfill the requirement for 4 separate subnets.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose /27 because they calculate 2^5 = 32 and forget to subtract 2 for the network and broadcast addresses, mistakenly thinking 32 hosts are available, or they choose /25 because they see it provides more than 50 hosts without realizing it only creates two subnets, not four.
Detailed technical explanation
How to think about this question
The subnet mask determines the boundary between the network and host portions of an IPv4 address; for /26, the last 6 bits are host bits, yielding 2^6 = 64 total addresses per subnet, with the first being the network address and the last the broadcast address, leaving 62 usable. In real-world scenarios, network engineers must account for future growth; while /26 minimizes waste here, a /25 might be chosen if departments are expected to expand beyond 62 hosts, but the question explicitly asks to minimize wasted addresses given current requirements.
KKey Concepts to Remember
A /26 subnet mask borrows 2 bits from the host portion of a /24 network.
A /26 network creates 4 subnets from a /24 parent network.
VLSM (Variable Length Subnet Masking) allows for efficient use of IP addresses by varying subnet sizes.
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
A /26 subnet mask borrows 2 bits from the host portion of a /24 network.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this N10-009 question in full detail.
Review a /26 subnet mask borrows 2 bits from the host portion of a /24 network., then practise related N10-009 questions on the same topic to reinforce the concept.
Networking Concepts — This question tests Networking Concepts — A /26 subnet mask borrows 2 bits from the host portion of a /24 network..
What is the correct answer to this question?
The correct answer is: /26 (255.255.255.192) — A /26 subnet mask (255.255.255.192) provides 62 usable host addresses per subnet (2^(32-26) - 2 = 62), which meets the requirement of at least 50 hosts per department. With a /24 network, you can create exactly four /26 subnets (192.168.1.0/26, 192.168.1.64/26, 192.168.1.128/26, 192.168.1.192/26), perfectly matching the four departments while minimizing wasted addresses.
What should I do if I get this N10-009 question wrong?
Review a /26 subnet mask borrows 2 bits from the host portion of a /24 network., then practise related N10-009 questions on the same topic to reinforce the concept.
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?
A /26 subnet mask borrows 2 bits from the host portion of a /24 network.
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