- A
Deploy one NAT gateway in each Availability Zone with a route table per AZ that points to the NAT gateway in the same AZ.
This provides per-AZ redundancy and avoids cross-AZ dependency.
- B
Deploy one NAT gateway in the first Availability Zone and route all private subnet traffic to that NAT gateway.
Why wrong: This creates a single point of failure; if that AZ fails, all private instances lose internet access.
- C
Use a single NAT instance in a public subnet with an auto scaling group and health checks.
Why wrong: NAT instances are less reliable and have lower bandwidth than NAT gateways; they also require management.
- D
Deploy two NAT gateways in the first Availability Zone and use a single route table pointing to one of them.
Why wrong: Both NAT gateways in the same AZ are still vulnerable to AZ failure.
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 has a VPC with public and private subnets in multiple Availability Zones. They want to deploy a NAT gateway for outbound internet access for instances in private subnets. Which of the following is the most highly available architecture?
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 Availability Zone with a route table per AZ that points to the NAT gateway in the same AZ.
For high availability, you should deploy a NAT gateway in each Availability Zone and route traffic from private subnets in each AZ to the NAT gateway in the same AZ. This avoids cross-AZ data transfer costs and ensures that an AZ failure does not affect other AZs. Option A is correct. Options B and C do not provide equal HA. Option D is incorrect because a NAT instance is less reliable than a managed NAT gateway.
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 one NAT gateway in each Availability Zone with a route table per AZ that points to the NAT gateway in the same AZ.
Why this is correct
This provides per-AZ redundancy and avoids cross-AZ dependency.
Related concept
CIDR notation defines the prefix length.
- ✗
Deploy one NAT gateway in the first Availability Zone and route all private subnet traffic to that NAT gateway.
Why it's wrong here
This creates a single point of failure; if that AZ fails, all private instances lose internet access.
- ✗
Use a single NAT instance in a public subnet with an auto scaling group and health checks.
Why it's wrong here
NAT instances are less reliable and have lower bandwidth than NAT gateways; they also require management.
- ✗
Deploy two NAT gateways in the first Availability Zone and use a single route table pointing to one of them.
Why it's wrong here
Both NAT gateways in the same AZ are still vulnerable to AZ failure.
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 Implementation — This question tests Network Implementation — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Deploy one NAT gateway in each Availability Zone with a route table per AZ that points to the NAT gateway in the same AZ. — For high availability, you should deploy a NAT gateway in each Availability Zone and route traffic from private subnets in each AZ to the NAT gateway in the same AZ. This avoids cross-AZ data transfer costs and ensures that an AZ failure does not affect other AZs. Option A is correct. Options B and C do not provide equal HA. Option D is incorrect because a NAT instance is less reliable than a managed NAT gateway.
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.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Last reviewed: Jun 20, 2026
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