ANS-C01 Network Security, Compliance and Governance Practice Question
Network Topology
A CloudFormation stack created a VPC Gateway Endpoint for S3 with the above policy. An EC2 instance in the VPC is unable to download objects from the S3 bucket using the AWS CLI. The instance has an IAM role with s3:GetObject permission. What is the most likely cause?
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 allow s3:ListBucket, which is needed for the CLI to list objects.
The VPC Endpoint policy shown in the CloudFormation stack (typically allows only s3:GetObject) does not include s3:ListBucket, which is required by the AWS CLI to list objects in a bucket before downloading them. Even though the IAM role has s3:GetObject, the endpoint policy is an additional layer that must also allow the action. Option A is incorrect because Gateway Endpoints do not use security groups. Option B is incorrect because the endpoint policy does allow s3:GetObject, but the issue is missing ListBucket. Option D is incorrect because the route table must have a route to the endpoint, but the question implies the endpoint is created and associated; the problem is the policy.
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 security group associated with the VPC Endpoint blocks traffic.
Why it's wrong here
Gateway Endpoints do not have security groups; they are managed by route tables and endpoint policies.
- ✗
The VPC Endpoint policy does not allow s3:GetObject.
Why it's wrong here
It does allow s3:GetObject.
- ✓
The VPC Endpoint policy does not allow s3:ListBucket, which is needed for the CLI to list objects.
Why this is correct
The CLI often lists objects first, requiring ListBucket permission.
- ✗
The route table for the private subnet does not have a route to the VPC Endpoint.
Why it's wrong here
If the route were missing, the request would not reach the endpoint; but the issue is likely policy-related.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
Go deeper
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.