CCNA Network Infrastructure and Connectivity Practice Question
A network requires at least 500 usable host addresses in one IPv4 subnet. Which prefix is the smallest that meets the requirement?
⚠ Common exam trap
Be careful not to confuse the total number of addresses with the number of usable host addresses. Remember to account for network and broadcast 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
✓
/23
To support at least 500 usable hosts, the subnet must provide at least 502 total addresses when the network and broadcast addresses are included. In plain language, that means 256 total addresses in a /24 are not enough, so the next larger power-of-two block is required. A /23 provides 512 total addresses and 510 usable host addresses, which satisfies the requirement while remaining the smallest valid option. This is a classic host-capacity question because it checks whether you can work backward from a required usable host count and choose the smallest prefix that works without wasting more space 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.
- ✗
/24
Why it's wrong here
This is wrong because a /24 provides only 254 usable host addresses.
When this WOULD be correct
If the question specified a requirement for a network with fewer than 256 usable host addresses, such as needing a subnet for a small office or a specific application, then a /24 would be the correct choice.
- ✓
/23
Why this is correct
This is correct because a /23 provides 510 usable host addresses.
- ✗
/22
Why it's wrong here
This is wrong because /22 would work but is larger than necessary.
When this WOULD be correct
In a scenario where the question asks for a subnet that can accommodate at least 1000 usable addresses, option C (/22) would be correct, as it provides 1022 usable addresses, satisfying the requirement.
- ✗
/25
Why it's wrong here
This is wrong because a /25 provides only 126 usable host addresses.
When this WOULD be correct
In a scenario where a question asks for the smallest subnet that can accommodate 126 usable hosts, option D: /25 would be the correct answer, as it meets the requirement exactly.
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.
✓/23Correct answer▾
Why this is correct
This is correct because a /23 provides 510 usable host addresses.
✗/24Wrong answer — click to see why▾
Why this is wrong here
A /24 subnet provides only 256 usable host addresses, which is insufficient for the requirement of at least 500 usable addresses. Therefore, it cannot be the correct answer.
★ When this WOULD be the correct answer
If the question specified a requirement for a network with fewer than 256 usable host addresses, such as needing a subnet for a small office or a specific application, then a /24 would be the correct choice.
Why candidates choose this
Candidates may mistakenly believe that a /24 subnet is sufficient due to familiarity with common subnet sizes, leading them to overlook the specific requirement for at least 500 usable addresses.
✗/22Wrong answer — click to see why▾
Why this is wrong here
Option C (/22) provides 1022 usable addresses, which exceeds the requirement of 500 usable addresses, but it is not the smallest prefix that meets the requirement. The correct answer is /23, which provides exactly 510 usable addresses.
★ When this WOULD be the correct answer
In a scenario where the question asks for a subnet that can accommodate at least 1000 usable addresses, option C (/22) would be correct, as it provides 1022 usable addresses, satisfying the requirement.
Why candidates choose this
Candidates may choose option C because they recognize that it meets the minimum address requirement, but they overlook the need for the smallest prefix, leading to confusion between sufficient and optimal solutions.
✗/25Wrong answer — click to see why▾
Why this is wrong here
Option D: /25 provides only 126 usable host addresses, which is insufficient for a requirement of at least 500 usable addresses in a single subnet.
★ When this WOULD be the correct answer
In a scenario where a question asks for the smallest subnet that can accommodate 126 usable hosts, option D: /25 would be the correct answer, as it meets the requirement exactly.
Why candidates choose this
Candidates may choose /25 due to a misunderstanding of subnetting, thinking that smaller prefixes can still accommodate more hosts than they actually can, or they may confuse the number of hosts with the prefix length.
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
Go deeper
Related to this question
Learn chapter
IPv4 Addressing and Address Classes
Key term
Subnet
A subnet is a logical subdivision of an IP network, created by partitioning a larger network address space using subnet masks.
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.
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Courseiva writes every 200-301 question from scratch — 1,389 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
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.