- A
Deploy a NAT Gateway in each Availability Zone for high availability.
Why wrong: This is more expensive and not necessary if AZ failure is acceptable.
- B
Launch a NAT instance in a public subnet and configure routing.
Why wrong: NAT instance requires manual management and is less reliable than NAT Gateway.
- C
Attach an Internet Gateway to the VPC and add a default route pointing to the IGW in private subnets.
Why wrong: Private subnets cannot route directly to IGW; they need a NAT device.
- D
Deploy a single NAT Gateway in one public subnet and configure route tables to route 0.0.0.0/0 traffic to it.
A single NAT Gateway provides internet access for all private subnets with minimal cost and management.
Question 12 of 1,705
NAT Gateway Cost Optimization — Single Gateway | AWS Advanced Networking Specialty Explained
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 minimize cost and management overhead. Which solution should be used?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
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 a single NAT Gateway in one public subnet and configure route tables to route 0.0.0.0/0 traffic to it.
Option D is correct because a single NAT Gateway in one public subnet provides outbound internet access for private subnets with lower cost and management overhead than multiple NAT Gateways or NAT instances. NAT Gateway is a managed AWS service that automatically handles failover within its Availability Zone, and routing private subnet traffic to it via a 0.0.0.0/0 route allows instances to reach the internet for software updates while remaining unreachable from the internet.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 NAT Gateway in each Availability Zone for high availability.
Why it's wrong here
This is more expensive and not necessary if AZ failure is acceptable.
- ✗
Launch a NAT instance in a public subnet and configure routing.
- ✗
Attach an Internet Gateway to the VPC and add a default route pointing to the IGW in private subnets.
Why it's wrong here
Private subnets cannot route directly to IGW; they need a NAT device.
- ✓
Deploy a single NAT Gateway in one public subnet and configure route tables to route 0.0.0.0/0 traffic to it.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose Option A (NAT Gateway in each AZ) assuming high availability is mandatory, but the question explicitly prioritizes minimizing cost and management overhead, making a single NAT Gateway the correct choice despite the availability trade-off.
Detailed technical explanation
How to think about this question
A NAT Gateway uses Elastic IP addresses and performs source network address translation (SNAT) for outbound traffic, translating private instance IPs to its own public IP. Under the hood, it is implemented as a horizontally scaled, redundant service within a single Availability Zone, so a single NAT Gateway can handle burst traffic but fails if its AZ becomes unavailable. In real-world scenarios, for cost-sensitive workloads with low availability requirements, a single NAT Gateway is acceptable, but production environments often use one per AZ to avoid cross-AZ data transfer costs and single points of failure.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Visual reference
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this ANS-C01 question test?
Network Design — This question tests Network Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Deploy a single NAT Gateway in one public subnet and configure route tables to route 0.0.0.0/0 traffic to it. — Option D is correct because a single NAT Gateway in one public subnet provides outbound internet access for private subnets with lower cost and management overhead than multiple NAT Gateways or NAT instances. NAT Gateway is a managed AWS service that automatically handles failover within its Availability Zone, and routing private subnet traffic to it via a 0.0.0.0/0 route allows instances to reach the internet for software updates while remaining unreachable from the internet.
What should I do if I get this ANS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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