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Question 1,447 of 1,705

Network Security, Compliance and Governance →easyMultiple ChoiceObjective-mapped

Quick Answer

The answer is that the VPC endpoint policy does not restrict access to the specific S3 bucket. Even though the S3 bucket policy limits access to the VPC endpoint and the IAM role grants permissions only to that bucket, the VPC endpoint itself has a default policy that allows full access to all S3 buckets. Without an explicit VPC endpoint policy that restricts actions and resources to only the designated bucket, the EC2 instances can reach any S3 bucket over the endpoint, provided the IAM policy permits it. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of how VPC endpoint policies, bucket policies, and IAM policies interact as layered controls. A common trap is assuming a restrictive bucket policy alone blocks all access, but the endpoint policy acts as the outermost guard. Remember the mnemonic “Endpoint First” — the VPC endpoint policy is the first gate, so if it’s wide open, other policies may not fully contain access.

ANS-C01 Network Security, Compliance and Governance Practice Question

This ANS-C01 practice question tests your understanding of network security, compliance and governance. 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 web application running on EC2 instances behind an Application Load Balancer (ALB). The application stores files in an S3 bucket. The security team wants to ensure that the EC2 instances can only access the specific S3 bucket and no other AWS services. They have created an IAM role for the EC2 instances with a policy that grants s3:PutObject and s3:GetObject on the specific bucket. They have also attached a VPC endpoint for S3 to the VPC and added a bucket policy that allows access only from the VPC endpoint. Despite this, the EC2 instances can still access other S3 buckets. What is the most likely reason?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

Question 1easymultiple choice

Full question →

A
The VPC endpoint does not have a route table associated with the private subnets.
Why wrong: Without association, traffic would not use the endpoint, but IAM policy still restricts access to the specific bucket.
B
The security group on the VPC endpoint is allowing all traffic.
Why wrong: Security groups control network traffic, not S3 bucket access.
C
The VPC endpoint policy does not restrict access to the specific S3 bucket.
Without a restrictive endpoint policy, the VPC endpoint allows access to any S3 bucket, and if the instances have any other IAM policies (even default), they could access other buckets.
D
The IAM role does not have a trust policy that allows EC2 to assume it.
Why wrong: If the role were not assumed, the instances would have no permissions at all.

Full breakdown with real-world context →

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

✓

The VPC endpoint policy does not restrict access to the specific S3 bucket.

Option D is correct because the S3 bucket policy restricting access to the VPC endpoint only applies to that bucket, but the EC2 instances can still access other buckets if the IAM policy allows it, unless a VPC endpoint policy restricts access to only the specific bucket. Option A is wrong because the IAM policy only grants access to the specific bucket, but if the instances have other IAM policies attached, they might allow broader access. However, the question implies only this policy is attached. Option B is wrong because the route table for the private subnets must have a route to the VPC endpoint for S3; if it doesn't, traffic would go through the NAT Gateway and not use the endpoint, but that would not allow access to other buckets if the IAM policy is restrictive. Actually, the most likely reason is that the VPC endpoint policy is not set to restrict access to only the specific bucket. Option C is wrong because the security group on the endpoint controls traffic to the endpoint, not what can be accessed through it.

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.

✗
The VPC endpoint does not have a route table associated with the private subnets.
Why it's wrong here
Without association, traffic would not use the endpoint, but IAM policy still restricts access to the specific bucket.
✗
The security group on the VPC endpoint is allowing all traffic.
Why it's wrong here
Security groups control network traffic, not S3 bucket access.
✓
The VPC endpoint policy does not restrict access to the specific S3 bucket.
Why this is correct
Without a restrictive endpoint policy, the VPC endpoint allows access to any S3 bucket, and if the instances have any other IAM policies (even default), they could access other buckets.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
CIDR notation defines the prefix length.
✗
The IAM role does not have a trust policy that allows EC2 to assume it.
Why it's wrong here
If the role were not assumed, the instances would have no permissions at all.

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.

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FAQ

Questions learners often ask

What does this ANS-C01 question test?

Network Security, Compliance and Governance — This question tests Network Security, Compliance and Governance — CIDR notation defines the prefix length..

What is the correct answer to this question?

The correct answer is: The VPC endpoint policy does not restrict access to the specific S3 bucket. — Option D is correct because the S3 bucket policy restricting access to the VPC endpoint only applies to that bucket, but the EC2 instances can still access other buckets if the IAM policy allows it, unless a VPC endpoint policy restricts access to only the specific bucket. Option A is wrong because the IAM policy only grants access to the specific bucket, but if the instances have other IAM policies attached, they might allow broader access. However, the question implies only this policy is attached. Option B is wrong because the route table for the private subnets must have a route to the VPC endpoint for S3; if it doesn't, traffic would go through the NAT Gateway and not use the endpoint, but that would not allow access to other buckets if the IAM policy is restrictive. Actually, the most likely reason is that the VPC endpoint policy is not set to restrict access to only the specific bucket. Option C is wrong because the security group on the endpoint controls traffic to the endpoint, not what can be accessed through it.

What should I do if I get this ANS-C01 question wrong?

Are there clue words in this question I should notice?

Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

What is the key concept behind this question?

CIDR notation defines the prefix length.

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Last reviewed: Jun 20, 2026

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