Quick Answer
The answer is 10.0.1.0/24, 10.0.3.0/24, and 10.0.5.0/24. These three subnet CIDR blocks are valid because each falls entirely within the parent VPC CIDR of 10.0.0.0/16, meaning their network addresses and all host addresses are contained within the 10.0.0.0–10.0.255.255 range. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this question tests your ability to quickly verify subnet containment, a foundational skill for VPC design and troubleshooting. A common trap is confusing CIDR block size with range—10.1.0.0/24 is outside the VPC, while 10.0.0.0/8 is a larger network that overlaps but is not a valid subnet because it extends beyond the VPC boundary. For a quick memory tip, remember that any valid subnet must have its network address fall within the parent CIDR and its prefix length must be larger (i.e., a smaller network) than the parent’s /16.
This ANS-C01 practice question tests your understanding of network implementation. 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. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. 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 company has a VPC with a CIDR of 10.0.0.0/16. They need to create subnets for a three-tier application. Which THREE subnet CIDR blocks are valid within this VPC?
10.0.1.0/24
Within 10.0.0.0/16.
10.0.3.0/24
Within VPC CIDR.
10.0.5.0/24
Within VPC CIDR.
10.1.0.0/24
Why wrong: Outside VPC CIDR.
10.0.0.0/8
Why wrong: Not a subnet; overlaps but not valid as a subnet within /16.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
10.0.1.0/24
Option A is correct because 10.0.1.0/24 is within 10.0.0.0/16. Option C is correct because 10.0.3.0/24 is within the range. Option D is correct because 10.0.5.0/24 is within the range. Option B is incorrect because 10.1.0.0/24 is outside the VPC CIDR. Option E is incorrect because 10.0.0.0/8 is larger and overlaps but is not a subnet.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Common exam traps
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
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FAQ
Network Implementation — This question tests Network Implementation — CIDR notation defines the prefix length..
The correct answer is: 10.0.1.0/24 — Option A is correct because 10.0.1.0/24 is within 10.0.0.0/16. Option C is correct because 10.0.3.0/24 is within the range. Option D is correct because 10.0.5.0/24 is within the range. Option B is incorrect because 10.1.0.0/24 is outside the VPC CIDR. Option E is incorrect because 10.0.0.0/8 is larger and overlaps but is not a subnet.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
CIDR notation defines the prefix length.
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Last reviewed: Jun 20, 2026
This ANS-C01 practice question is part of Courseiva's free Amazon Web Services 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 ANS-C01 exam.
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