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 a CIDR block of 172.16.0.0/16. They have a public subnet (172.16.1.0/24) and a private subnet (172.16.2.0/24). They have an internet gateway attached to the public subnet. They launch an EC2 instance in the public subnet with a public IP address. The instance is running a web server on port 80. They also launch an EC2 instance in the private subnet that needs to download updates from the internet. The private subnet does not have a route to the internet. The company wants to provide internet access to the private instance in a secure and cost-effective manner. Which solution should they implement?
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 the public subnet and add a route in the private subnet's route table pointing to the NAT Gateway
A NAT Gateway in the public subnet allows instances in the private subnet to initiate outbound connections to the internet (e.g., for downloading updates) while preventing inbound connections from the internet. The private subnet's route table must have a default route (0.0.0.0/0) pointing to the NAT Gateway. This is secure because the NAT Gateway uses Elastic IPs and does not accept unsolicited inbound traffic, and it is cost-effective as it is a managed service with no maintenance overhead.
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.
✓
Create a NAT Gateway in the public subnet and add a route in the private subnet's route table pointing to the NAT Gateway
Why this is correct
NATGateway provides outbound internet access for private instances.
Related concept
Read the scenario before looking for a memorised answer.
✗
Create a VPC Gateway Endpoint for S3 and configure the private instance to use it
Why it's wrong here
Gateway Endpoint only provides access to S3, not general internet.
✗
Create a forward proxy server in the public subnet and configure the private instance to use it
Why it's wrong here
Proxy server adds complexity and cost.
✗
Create a NAT instance in the public subnet and configure the private instance to use it
Why it's wrong here
NAT instance is less reliable and requires management.
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 or assume a VPC Gateway Endpoint can provide general internet access, but the key distinction is that a NAT Gateway is a managed service for outbound-only internet access, while Gateway Endpoints are specific to AWS services like S3 and DynamoDB.
Detailed technical explanation
How to think about this question
A NATGateway operates at Layer 4 (TCP/UDP) and translates the private source IP of outbound packets to its own Elastic IP address, using stateful connection tracking to return traffic to the correct private instance. It supports up to 45 Gbps of bandwidth and automatically scales, whereas a NAT instance is limited by instance type and requires manual failover. In real-world scenarios, a NAT Gateway is preferred for production workloads because it is highly available within an Availability Zone and can be deployed in multiple AZs for redundancy.
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.
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 the public subnet and add a route in the private subnet's route table pointing to the NAT Gateway — A NAT Gateway in the public subnet allows instances in the private subnet to initiate outbound connections to the internet (e.g., for downloading updates) while preventing inbound connections from the internet. The private subnet's route table must have a default route (0.0.0.0/0) pointing to the NAT Gateway. This is secure because the NAT Gateway uses Elastic IPs and does not accept unsolicited inbound traffic, and it is cost-effective as it is a managed service with no maintenance overhead.
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.
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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