CCNA Network Infrastructure and Connectivity Practice Question
A subnet must support 14 usable hosts. Which prefix is the smallest that meets the requirement?
⚠ Common exam trap
Avoid choosing a subnet size that either doesn't meet the host requirement or is unnecessarily large, leading to wasted addresses.
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
To support 14 usable hosts, the subnet must have 16 total addresses, because two are reserved for the network and broadcast addresses. In plain language, you need enough address slots so that after those two reserved entries are removed, 14 remain. A /28 provides exactly that: 16 total addresses and 14 usable addresses. This is a classic minimum-subnet-size question because it tests whether you can work backward from host requirement to prefix length. A /29 would be too small, while a /27 would work but waste more addresses than necessary.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
/29
Why it's wrong here
A /29 prefix translates to subnet mask 255.255.255.248 and a block size of 8 addresses. The number of usable hosts is calculated as 2^(32-29) - 2, which equals 6 hosts after excluding the network and broadcast addresses. Since the requirement demands 14 usable hosts, a /29 subnet falls short by 8 addresses and cannot be used.
When this WOULD be correct
If the question asked for a subnet that supports a maximum of 6 usable hosts, then a /29 prefix would be the correct answer, as it allows for exactly 6 usable addresses in that subnet.
- ✓
/28
Why this is correct
A /28 prefix uses subnet mask 255.255.255.240, creating a block of 16 addresses per subnet. After reserving the network address and broadcast address, exactly 14 addresses remain available for hosts. This precisely matches the requirement of 14 usable hosts, making it the most efficient prefix length that meets the demand without wasting address space.
- ✗
/27
Why it's wrong here
While a /27 prefix (subnet mask 255.255.255.224) can support 30 usable hosts—two raised to five minus two—it is not the optimal choice. The subnet provides more than double the required 14 hosts, meaning 16 usable addresses would go unused. Because the goal is to support exactly 14 usable hosts with minimal waste, the /27 is technically functional but not the most appropriate prefix.
When this WOULD be correct
In a different scenario where the question asks for a subnet that can support at least 30 usable hosts, option C: /27 would be the correct answer, as it provides exactly 30 usable addresses, meeting the new requirement.
- ✗
/26
Why it's wrong here
A /26 subnet mask is 255.255.255.192, which yields 62 usable hosts per subnet—far more than the 14-host requirement. Choosing this prefix would waste 48 usable addresses and unnecessarily shrink the number of available subnets. The smallest prefix that satisfies the 14-host constraint is /28, making /26 an excessive and inefficient allocation.
When this WOULD be correct
If the question asked for a subnet that supports at least 62 usable hosts, then /26 would be the correct answer, as it provides a sufficient number of addresses for that requirement.
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 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓/28Correct answer▾
Why this is correct
A /28 prefix uses subnet mask 255.255.255.240, creating a block of 16 addresses per subnet. After reserving the network address and broadcast address, exactly 14 addresses remain available for hosts. This precisely matches the requirement of 14 usable hosts, making it the most efficient prefix length that meets the demand without wasting address space.
✗/29Wrong answer — click to see why▾
Why this is wrong here
A /29 subnet provides only 6 usable host addresses, which is insufficient for the requirement of 14 usable hosts. Therefore, it does not meet the specified criteria.
★ When this WOULD be the correct answer
If the question asked for a subnet that supports a maximum of 6 usable hosts, then a /29 prefix would be the correct answer, as it allows for exactly 6 usable addresses in that subnet.
Why candidates choose this
Candidates may be tempted to choose /29 due to a misunderstanding of subnetting calculations, mistakenly believing that smaller subnets can accommodate more hosts than they actually can.
✗/27Wrong answer — click to see why▾
Why this is wrong here
Option C: /27 provides 30 usable hosts, which exceeds the requirement of 14 usable hosts. However, the question asks for the smallest prefix that meets the requirement, making /28 the correct choice.
★ When this WOULD be the correct answer
In a different scenario where the question asks for a subnet that can support at least 30 usable hosts, option C: /27 would be the correct answer, as it provides exactly 30 usable addresses, meeting the new requirement.
Why candidates choose this
Candidates may choose /27 because they misinterpret the requirement, thinking that a larger subnet is always better, or they may confuse the number of usable addresses with the total number of addresses in the subnet.
✗/26Wrong answer — click to see why▾
Why this is wrong here
Option D: /26 provides 62 usable hosts, which exceeds the requirement of 14 usable hosts. Therefore, it is not the smallest prefix that meets the specified need.
★ When this WOULD be the correct answer
If the question asked for a subnet that supports at least 62 usable hosts, then /26 would be the correct answer, as it provides a sufficient number of addresses for that requirement.
Why candidates choose this
Candidates may choose /26 thinking that a larger subnet is always better for accommodating future growth, not realizing that the question specifically asks for the smallest prefix that meets the current requirement.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Visual reference
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Related to this question
Learn chapter
IPv4 Addressing and Address Classes
Key term
CAN
A CAN (Controller Area Network) is a robust vehicle bus standard designed to allow microcontrollers and devices to communicate with each other without a host computer.
Key term
Subnet
A subnet is a logical subdivision of an IP network, created by partitioning a larger network address space using subnet masks.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 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 200-301 exam.