ANS-C01 Network Implementation Practice Question
Exhibit
Refer to the exhibit.
```
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Principal": "*",
"Action": [
"s3:GetObject"
],
"Resource": "arn:aws:s3:::example-bucket/*",
"Condition": {
"StringEquals": {
"aws:SourceVpce": "vpce-0123456789abcdef0"
}
}
}
]
}
```A company has an S3 bucket with the bucket policy shown. The VPC endpoint ID is correct. However, an EC2 instance in a private subnet in the same VPC cannot download objects from the bucket. What is a possible reason?
⚠ Common exam trap
The ANS-C01 exam often tests the misconception that VPC endpoints always require security groups or that any route to S3 (including via NAT) will satisfy a bucket policy condition, when in fact the condition `aws:sourceVpce` specifically requires traffic to traverse the VPC endpoint.
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 EC2 instance is accessing S3 via a NAT Gateway instead of the VPC endpoint
The bucket policy likely includes a condition that restricts access to only requests originating from the VPC endpoint (e.g., `aws:sourceVpce`). If the EC2 instance in the private subnet routes traffic through a NAT Gateway instead of the VPC endpoint, the source IP will be the NAT Gateway's public IP, not the VPC endpoint's private IP, causing the condition to fail and the request to be denied. The instance can still reach S3 via the NAT Gateway, but the policy explicitly blocks non-endpoint traffic.
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 EC2 instance does not have a route to the VPC endpoint
Why it's wrong here
VPC endpoints are accessible via the VPC's route table; if the endpoint is in the same VPC, no route is needed.
- ✗
The bucket policy does not allow s3:ListBucket
Why it's wrong here
The action is GetObject; ListBucket is not required for downloading.
- ✓
The EC2 instance is accessing S3 via a NAT Gateway instead of the VPC endpoint
Why this is correct
The policy only allows requests coming through the VPC endpoint; requests via NAT Gateway are denied.
- ✗
The VPC endpoint security group is blocking traffic
Why it's wrong here
Security groups are not applicable to Gateway endpoints.
Visual reference
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
Related to this question
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JA
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.