CCNA Network Infrastructure and Connectivity Practice Question
A subnet requires 200 usable host addresses. Which prefix is the smallest that meets the requirement?
⚠ Common exam trap
Ensure you calculate usable addresses, not just total addresses, and choose the smallest prefix that meets the requirement.
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
✓
/24
A /24 is the smallest valid choice. In plain language, the subnet needs enough total addresses so that after the network and broadcast addresses are reserved, 200 hosts still remain. A /25 is too small because it provides only 126 usable hosts. A /24 provides 254 usable hosts, which satisfies the requirement while being the next logical prefix size up. This is a standard host-capacity planning question. The key is to work from usable hosts, not just total addresses, and then choose the smallest prefix that actually works.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
/25
Why it's wrong here
A /25 prefix uses 7 host bits, yielding 2^7 = 128 total addresses. With the network and broadcast addresses removed, only 126 usable host addresses are available, which is 74 short of the 200 required. Therefore, although /25 is the next larger option, it still cannot support the needed host count.
When this WOULD be correct
If the question required a subnet that accommodates up to 126 usable host addresses, such as needing to support a small department within a larger organization, then /25 would be the correct answer.
- ✓
/24
Why this is correct
A /24 prefix allocates 8 bits for host addressing, producing 2^8 = 256 total addresses. After deducting the network and broadcast addresses, 254 usable host addresses remain, which comfortably exceeds the required 200. This makes /24 the correct prefix, as it is the smallest one that meets the requirement.
- ✗
/26
Why it's wrong here
With 6 host bits, a /26 prefix offers just 2^6 = 64 total addresses. Once the network and broadcast addresses are excluded, the usable pool drops to 62 addresses, a significant shortfall from the 200-host requirement. This option is clearly insufficient for the stated subnet size.
When this WOULD be correct
If the question specified a requirement for a maximum of 62 usable host addresses, then a /26 subnet would be the correct choice, as it meets that specific need.
- ✗
/27
Why it's wrong here
A /27 prefix provides only 5 host bits, resulting in 2^5 = 32 total addresses. Subtracting the network and broadcast leaves merely 30 usable addresses, which is far below the 200 needed. Consequently, /27 cannot be used for a network requiring 200 usable host addresses.
When this WOULD be correct
In a different scenario where a question asks for the smallest subnet that can accommodate up to 30 hosts, option D: /27 would be correct, as it provides exactly 30 usable addresses, meeting the 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.
✓/24Correct answer▾
Why this is correct
A /24 prefix allocates 8 bits for host addressing, producing 2^8 = 256 total addresses. After deducting the network and broadcast addresses, 254 usable host addresses remain, which comfortably exceeds the required 200. This makes /24 the correct prefix, as it is the smallest one that meets the requirement.
✗/25Wrong answer — click to see why▾
Why this is wrong here
A /25 subnet provides 126 usable host addresses, which is insufficient for a requirement of 200 usable addresses. Therefore, it does not meet the specified needs of the question.
★ When this WOULD be the correct answer
If the question required a subnet that accommodates up to 126 usable host addresses, such as needing to support a small department within a larger organization, then /25 would be the correct answer.
Why candidates choose this
Candidates might choose /25 due to a misunderstanding of subnetting calculations, mistakenly believing that it offers enough addresses for larger networks or confusing it with the next larger prefix, /24.
✗/26Wrong answer — click to see why▾
Why this is wrong here
A /26 subnet provides only 62 usable host addresses (64 total minus 2 for network and broadcast), which is insufficient for the requirement of 200 usable addresses.
★ When this WOULD be the correct answer
If the question specified a requirement for a maximum of 62 usable host addresses, then a /26 subnet would be the correct choice, as it meets that specific need.
Why candidates choose this
Candidates may choose /26 due to a misunderstanding of subnetting, thinking that smaller prefixes can still accommodate a larger number of hosts, or they may confuse the number of hosts with the prefix length.
✗/27Wrong answer — click to see why▾
Why this is wrong here
Option D: /27 provides only 30 usable host addresses (32 total addresses minus 2 for network and broadcast), which is insufficient for the requirement of 200 usable host addresses.
★ When this WOULD be the correct answer
In a different scenario where a question asks for the smallest subnet that can accommodate up to 30 hosts, option D: /27 would be correct, as it provides exactly 30 usable addresses, meeting the requirement.
Why candidates choose this
Candidates may choose option D due to a misunderstanding of subnetting, thinking that smaller prefixes can still meet the host requirements, or they may confuse the number of usable addresses with the total address count.
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
Collision Domains and Broadcast Domains
Key term
Usable hosts
Usable hosts are the IP addresses in a subnet that can actually be assigned to devices like computers, printers, or servers, excluding the network and broadcast addresses.
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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JA
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.