- A
Deploy a single NAT Gateway in one AZ and use a VPN to an on-premises internet gateway as backup.
Why wrong: This still has a single point of failure for the NAT Gateway and adds VPN complexity.
- B
Deploy one NAT Gateway in each AZ that contains private subnets, and update the route tables accordingly.
This ensures each AZ is independent; if one NAT Gateway fails, only that AZ loses internet access.
- C
Use a NAT instance in an Auto Scaling group across multiple AZs instead of a NAT Gateway.
Why wrong: NAT instances are not fully managed and require maintenance; NAT Gateway is preferred for high availability.
- D
Create a second VPC with a NAT Gateway and peer the VPCs to share the NAT Gateway.
Why wrong: VPC peering does not allow transitive routing to a NAT Gateway across VPCs.
ANS-C01 Network Design Practice Question
This ANS-C01 practice question tests your understanding of network design. 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 public and private subnets. The private subnets need to access the internet for software updates. The company wants to use a single NAT Gateway for all private subnets to reduce costs, but the NAT Gateway is in a single Availability Zone (AZ). The network architect is concerned about single points of failure. Which design best addresses high availability while still using the minimum number of NAT Gateways?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"best"Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Clue:
"minimum / minimize"Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
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
Deploy one NAT Gateway in each AZ that contains private subnets, and update the route tables accordingly.
Using one NAT Gateway per AZ that has private subnets provides high availability. The minimum is 2 if there are at least 2 AZs with private subnets. Option B is incorrect because a single NAT Gateway is a single point of failure. Option C is incorrect because NAT instances are less reliable and require management. Option D is incorrect because multiple VPCs add complexity and cost.
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.
- ✗
Deploy a single NAT Gateway in one AZ and use a VPN to an on-premises internet gateway as backup.
- ✓
Deploy one NAT Gateway in each AZ that contains private subnets, and update the route tables accordingly.
- ✗
Use a NAT instance in an Auto Scaling group across multiple AZs instead of a NAT Gateway.
- ✗
Create a second VPC with a NAT Gateway and peer the VPCs to share the NAT Gateway.
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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
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.
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FAQ
Questions learners often ask
What does this ANS-C01 question test?
Network Design — This question tests Network Design — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Deploy one NAT Gateway in each AZ that contains private subnets, and update the route tables accordingly. — Using one NAT Gateway per AZ that has private subnets provides high availability. The minimum is 2 if there are at least 2 AZs with private subnets. Option B is incorrect because a single NAT Gateway is a single point of failure. Option C is incorrect because NAT instances are less reliable and require management. Option D is incorrect because multiple VPCs add complexity and cost.
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: "best", "minimum / minimize". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
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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