This ANS-C01 practice question tests your understanding of network design. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 three Availability Zones. They want to provide outbound internet access to instances in private subnets while preventing inbound traffic from the internet. Which solution meets these requirements with the least operational overhead?
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 a NAT Gateway in a public subnet and add a default route in the private subnet route table pointing to the NAT Gateway.
Option C is correct because a NAT Gateway is a fully managed AWS service that provides outbound internet access for instances in private subnets while blocking unsolicited inbound connections. By placing the NAT Gateway in a public subnet and adding a default route (0.0.0.0/0) in the private subnet route table pointing to the NAT Gateway, traffic from private instances is source NATed to the NAT Gateway's Elastic IP, ensuring inbound traffic from the internet cannot reach the private instances. This solution offers the least operational overhead as AWS handles scaling, patching, and availability, unlike a self-managed NAT instance.
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 instance in a public subnet and configure the private subnet route table to point to it.
Why it's wrong here
NAT instances require management overhead for scaling and patching.
✗
Attach an Internet Gateway to the VPC and add a default route to it in the private subnet route table.
Why it's wrong here
This would allow inbound traffic from the internet to private instances.
✓
Create a NAT Gateway in a public subnet and add a default route in the private subnet route table pointing to the NAT Gateway.
Why this is correct
NATGateway is a managed service, reduces operational overhead.
Clue confirmation
The clue word "least" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Create a VPC Gateway Endpoint for Amazon S3 and route outbound traffic through it.
Why it's wrong here
VPC endpoint only provides access to supported AWS services, not general internet.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse a NATGateway with a NAT instance, assuming both offer similar operational overhead, or mistakenly think that an Internet Gateway can be used directly in private subnets, ignoring that it would allow inbound traffic from the internet.
Detailed technical explanation
How to think about this question
A NATGateway uses Port Address Translation (PAT) to map multiple private IP addresses to a single Elastic IP, with stateful connections tracked in a connection table that automatically expires after a timeout (e.g., 350 seconds for TCP). Under the hood, the NAT Gateway resides in a specific subnet but is not assigned a security group; instead, it relies on network ACLs and route tables for traffic control. In a real-world scenario, if the NAT Gateway is placed in a single Availability Zone, instances in other AZs may experience cross-AZ data transfer costs and potential single points of failure, so deploying one NAT Gateway per AZ is a common high-availability pattern.
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 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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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: Create a NAT Gateway in a public subnet and add a default route in the private subnet route table pointing to the NAT Gateway. — Option C is correct because a NAT Gateway is a fully managed AWS service that provides outbound internet access for instances in private subnets while blocking unsolicited inbound connections. By placing the NAT Gateway in a public subnet and adding a default route (0.0.0.0/0) in the private subnet route table pointing to the NAT Gateway, traffic from private instances is source NATed to the NAT Gateway's Elastic IP, ensuring inbound traffic from the internet cannot reach the private instances. This solution offers the least operational overhead as AWS handles scaling, patching, and availability, unlike a self-managed NAT instance.
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: "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?
Read the scenario before looking for a memorised answer.
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Question Discussion
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