The correct solution is to create a VPC Gateway Endpoint for S3 and add a route in the private subnet route table pointing to the endpoint. This works because a Gateway Endpoint uses AWS’s private network backbone to route S3 traffic directly from your VPC, bypassing the public internet entirely, while a private subnet without a NAT Gateway has no other path to reach S3. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this question tests your understanding of VPC endpoint types and their specific use cases—a common trap is confusing Gateway Endpoints (for S3 and DynamoDB) with Interface Endpoints (for other services like API Gateway or KMS). Remember that S3 traffic from a private subnet requires a route table entry targeting the Gateway Endpoint ID, not an internet gateway or NAT. Memory tip: “Gateway for S3, Interface for the rest.”
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 a CIDR block of 10.0.0.0/16. It has a public subnet (10.0.1.0/24) and a private subnet (10.0.2.0/24). An EC2 instance in the private subnet needs to access an S3 bucket. The company wants to ensure that traffic to S3 does not traverse the internet. Which solution should be used?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a VPC Gateway Endpoint for S3 and add a route in the private subnet route table pointing to the endpoint
A VPC Gateway Endpoint for S3 allows private subnet instances to access S3 without internet. A NAT Gateway uses the internet. An Interface Endpoint is for other AWS services, not S3. Direct Connect is not necessary for S3 access within the same region.
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.
✗
Create a VPC Interface Endpoint for S3 and associate it with the private subnet
Why it's wrong here
Interface Endpoint is not supported for S3; S3 uses Gateway Endpoints.
✗
Create a NAT Gateway in the public subnet and add a route in the private subnet route table pointing to the NAT Gateway
Why it's wrong here
NATGateway uses the internet, not private connectivity.
✓
Create a VPC Gateway Endpoint for S3 and add a route in the private subnet route table pointing to the endpoint
Set up an AWS Direct Connect connection and use a private virtual interface
Why it's wrong here
Direct Connect is overkill for in-region S3 access and still requires a VPC endpoint.
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 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.
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.
Network Design — This question tests Network Design — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Create a VPC Gateway Endpoint for S3 and add a route in the private subnet route table pointing to the endpoint — A VPC Gateway Endpoint for S3 allows private subnet instances to access S3 without internet. A NAT Gateway uses the internet. An Interface Endpoint is for other AWS services, not S3. Direct Connect is not necessary for S3 access within the same region.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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 a CIDR block of 10.0.0.0/16. They have three subnets: Subnet A (10.0.1.0/24) in us-east-1a, Subnet B (10.0.2.0/24) in us-east-1b, and Subnet C (10.0.3.0/24) in us-east-1c. The company has deployed a set of EC2 instances in Subnet A that need to access an Amazon S3 bucket. The company wants to ensure that traffic to S3 does not traverse the internet and remains within the AWS network. The VPC has a VPC endpoint for S3 (gateway type) created and associated with the route table for Subnet A. However, the instances are unable to access the S3 bucket. What is the MOST likely cause?
medium
A.The VPC does not have an internet gateway attached.
✓ B.The route table for Subnet A does not have a route for the S3 prefix list pointing to the VPC endpoint.
C.The S3 bucket policy does not allow access from the VPC endpoint.
D.The VPC endpoint is not associated with a security group that allows outbound traffic to S3.
Why B: Option B is correct. A gateway VPC endpoint for S3 is only accessible from the subnet whose route table has a route to the endpoint. The route table for Subnet A must have a route for the S3 prefix list pointing to the VPC endpoint. If that route is missing, traffic will not use the endpoint. Option A is incorrect because a VPC endpoint does not require an internet gateway. Option C is incorrect because a gateway endpoint does not use security groups; it uses endpoint policies. Option D is incorrect because the endpoint policy does not need to be explicitly attached to the bucket; the bucket policy must grant access to the VPC endpoint.
Last reviewed: Jun 20, 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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