The answer is to create a gateway VPC endpoint for S3 and add a route in the private subnet’s route table pointing to the S3 prefix list via that endpoint. This is correct because a gateway VPC endpoint allows instances in a private subnet to access S3 privately using AWS’s internal network, bypassing both the internet gateway and NAT Gateway entirely. The route to the S3 prefix list ensures that all S3-bound traffic is directed through the endpoint, keeping data within the AWS backbone and avoiding public internet transit. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of VPC endpoints and the distinction between gateway endpoints (for S3 and DynamoDB) and interface endpoints. A common trap is assuming a NAT Gateway is required for private subnet outbound traffic, but for S3 in the same region, a gateway endpoint is more cost-effective and secure. Memory tip: “Gateway for S3, Interface for the rest” — gateway endpoints are free and use route tables, while interface endpoints use private IPs and incur hourly costs.
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 an internet gateway and a NAT Gateway. The private subnet route table has a default route to the NAT Gateway. The company wants to enable instances in the private subnet to access an S3 bucket in the same region without traversing the internet. Which TWO actions should the company take?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add a route to the S3 prefix list via the gateway endpoint in the private subnet route table.
Option B is correct because adding a route to the S3 prefix list via the gateway endpoint directs traffic destined for S3 through the VPC endpoint, keeping it within the AWS network. Option C is correct because a gateway VPC endpoint for S3 provides a private, scalable connection to S3 without requiring internet access or a NAT Gateway. Together, these actions allow private subnet instances to access S3 privately and efficiently.
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.
✗
Remove the default route to the NAT Gateway from the private subnet route table.
Why it's wrong here
Removing default route would break outbound internet access.
✓
Add a route to the S3 prefix list via the gateway endpoint in the private subnet route table.
Why this is correct
This enables private access.
Related concept
Read the scenario before looking for a memorised answer.
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse gateway endpoints with interface endpoints, incorrectly assuming S3 requires an interface endpoint, or they think the NAT Gateway must be removed entirely, when in fact the NAT Gateway should remain for other outbound traffic and only the S3-specific route needs to be added via the gateway endpoint.
Detailed technical explanation
How to think about this question
Gateway VPC endpoints use prefix lists and route table entries to direct traffic to S3 via the AWS global network, leveraging the S3 service’s public IP addresses but routing them through the endpoint without internet exposure. The endpoint is horizontally scaled, redundant, and highly available by default, and it does not require a separate NAT device or internet gateway for S3 access. In real-world scenarios, this setup is critical for cost optimization and security compliance, as it avoids data transfer costs through a NAT Gateway and keeps traffic within the AWS backbone.
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: Add a route to the S3 prefix list via the gateway endpoint in the private subnet route table. — Option B is correct because adding a route to the S3 prefix list via the gateway endpoint directs traffic destined for S3 through the VPC endpoint, keeping it within the AWS network. Option C is correct because a gateway VPC endpoint for S3 provides a private, scalable connection to S3 without requiring internet access or a NAT Gateway. Together, these actions allow private subnet instances to access S3 privately and efficiently.
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.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company has a VPC with public and private subnets. The public subnet has a NAT gateway for outbound internet access from private subnets. The private subnets have EC2 instances that need to access an S3 bucket in the same region. The company wants to minimize data transfer costs and avoid traversing the internet. What is the MOST cost-effective solution?
hard
A.Configure an S3 bucket policy that restricts access to the VPC's public IP addresses.
✓ B.Create a VPC Gateway Endpoint for S3 and attach a policy allowing access from the private subnets.
C.Route traffic to the NAT gateway and then to the S3 bucket using a VPC peering connection.
D.Create a VPC Interface Endpoint for S3 and associate with the private subnets.
Why B: A VPC Gateway Endpoint for S3 allows private subnet instances to access S3 over the AWS network without traversing the internet or a NAT gateway, eliminating data transfer costs for the NAT gateway and avoiding internet egress charges. This is the most cost-effective solution because gateway endpoints are free and use prefix lists in the route table to direct traffic to S3 via the AWS backbone.
Last reviewed: Jun 11, 2026
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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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