The answer is to create six /24 subnets across two Availability Zones, with three subnets per AZ. This design is correct because each /24 subnet provides exactly 256 IP addresses, meeting the minimum requirement of at least 256 IPs per subnet for the public, private, and database tiers, while also ensuring high availability by distributing the subnets across two AZs. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this question tests your understanding of subnet sizing and AZ redundancy—a common trap is choosing a /25 (128 IPs) or /26 (64 IPs) subnet, which fails the 256-IP requirement, or using only one AZ, which violates high-availability best practices. A useful memory tip: for “256 IPs, think /24—that’s the magic number for a full Class C block, and always pair it with two AZs for fault tolerance.
ANS-C01 Network Implementation Practice Question
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 is setting up a new VPC with a CIDR block of 10.0.0.0/16. They need to create subnets for different tiers: public (web servers), private (application servers), and database (RDS). They want to maximize the number of available IP addresses while ensuring each subnet has at least 256 IP addresses. Which subnet design meets these requirements?
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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create six /24 subnets (256 IPs each) across two Availability Zones (three per AZ).
Using /24 subnets (256 IPs each) across three tiers in two AZs requires 6 subnets, which fits within the /16. Option A uses /25 (128 IPs) which is too small. Option B uses /24 but only one AZ, not highly available. Option D uses /26 (64 IPs) which is too small.
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
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Create six /24 subnets (256 IPs each) across two Availability Zones (three per AZ).
Why this is correct
/24 provides 256 IPs, and using two AZs provides high availability.
Clue confirmation
The clue word "least" in the question point toward this answer.
Create three /24 subnets (256 IPs each) in one Availability Zone.
Why it's wrong here
Single AZ is not highly available.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
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
How to think about this question
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.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
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
How this comes up in practice
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
Got this wrong? Here's your next step.
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.
Network Implementation — This question tests Network Implementation — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Create six /24 subnets (256 IPs each) across two Availability Zones (three per AZ). — Using /24 subnets (256 IPs each) across three tiers in two AZs requires 6 subnets, which fits within the /16. Option A uses /25 (128 IPs) which is too small. Option B uses /24 but only one AZ, not highly available. Option D uses /26 (64 IPs) which is too small.
What should I do if I get this ANS-C01 question wrong?
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.
Are there clue words in this question I should notice?
Yes — watch for: "least". You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
What is the key concept behind this question?
CIDR notation defines the prefix length.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is deploying a VPC with a CIDR block of 10.0.0.0/16. The VPC requires six subnets: three public and three private, each with a /24 CIDR. The company needs to ensure high availability across three Availability Zones. Which TWO of the following are valid subnet CIDR assignments that meet these requirements?
Why B: Options A and D are correct because they provide three non-overlapping /24 subnets per AZ across three AZs. B overlaps and C and E overlap within the same AZ.
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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.
Question Discussion
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