This 200-301 practice question tests your understanding of network infrastructure and connectivity. 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: subnetting divides an IPv4 network into smaller subnets by allocating bits to the network and host portions of the address.. 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 requires at least 500 usable host addresses in one IPv4 subnet. Which prefix is the smallest that meets the requirement?
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.
/24
Why wrong: This is wrong because a /24 provides only 254 usable host addresses.
/23
This is correct because a /23 provides 510 usable host addresses.
/22
Why wrong: This is wrong because /22 would work but is larger than necessary.
/25
Why wrong: This is wrong because a /25 provides only 126 usable host addresses.
Answer choices
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.
Key principle: Subnetting divides an IPv4 network into smaller subnets by allocating bits to the network and host portions of the address.
Answer analysis
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.
Clue confirmation
The clue word "least" in the question point toward this answer.
Related concept
Subnetting divides an IPv4 network into smaller subnets by allocating bits to the network and host portions of the address.
/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
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.
Why this is correct
This is correct because a /23 provides 510 usable host addresses.
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.
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.
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?”
Common exam traps
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.
Detailed technical explanation
Subnetting is a fundamental concept in IPv4 networking that divides a larger network into smaller subnetworks, each identified by a network prefix. The prefix length, expressed as a slash followed by a number (e.g., /24), determines how many bits are used for the network portion versus the host portion of the address. The number of usable host addresses in a subnet is calculated as 2^(32 - prefix length) minus 2, accounting for the network and broadcast addresses which cannot be assigned to hosts. To determine the smallest prefix that supports at least 500 usable hosts, you must find the subnet mask that provides at least 502 total addresses (500 hosts plus network and broadcast). A /24 subnet provides 256 total addresses (254 usable), which is insufficient. A /23 subnet doubles the address space to 512 total addresses, yielding 510 usable hosts, which meets the requirement efficiently without excessive waste of IP space. Larger subnets like /22 provide more addresses than needed, which is less optimal. A common exam trap is to select a /22 subnet because it clearly supports more than 500 hosts, but this wastes IP addresses and is not the smallest valid subnet. Cisco exams test your ability to optimize subnetting for host requirements. Practically, using the smallest subnet that meets host needs conserves IP address space and simplifies network management, especially in environments with limited IPv4 address availability.
Key takeaway
Subnetting divides an IPv4 network into smaller subnets by allocating bits to the network and host portions of the address.
Real-world example
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.
What to study next
Review subnetting divides an IPv4 network into smaller subnets by allocating bits to the network and host portions of the address., then practise related 200-301 questions on the same topic to reinforce the concept.
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FAQ
Network Infrastructure and Connectivity — This question tests Network Infrastructure and Connectivity — Subnetting divides an IPv4 network into smaller subnets by allocating bits to the network and host portions of the address..
The correct answer is: /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.
Review subnetting divides an IPv4 network into smaller subnets by allocating bits to the network and host portions of the address., then practise related 200-301 questions on the same topic to reinforce the concept.
Yes — watch for: "least". You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
Subnetting divides an IPv4 network into smaller subnets by allocating bits to the network and host portions of the address.
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Last reviewed: May 17, 2026
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