ANS-C01 Network Implementation Practice Question
Network Topology
Refer to the exhibit. A VPC endpoint for S3 is created as a Gateway endpoint. The route tables rtb-11111111 and rtb-22222222 are associated with the endpoint. An EC2 instance in a subnet associated with rtb-11111111 cannot access S3 via the endpoint. What is the most likely cause?
⚠ Common exam trap
The ANS-C01 exam often tests the distinction between associating a route table with a Gateway Endpoint and actually adding the route to the S3 prefix list — candidates mistakenly think association alone is sufficient, but the route entry is mandatory for traffic to flow through the 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 route table rtb-11111111 does not have a route to the S3 prefix list with the target as the VPC endpoint.
A Gateway VPC Endpoint for S3 works by adding a route in the subnet's route table that points the S3 prefix list (com.amazonaws.region.s3) to the endpoint ID (vpce-xxx). Without this specific route, traffic destined for S3 from the subnet associated with rtb-11111111 will follow the default route (e.g., an Internet Gateway or NAT Gateway) instead of being routed through the endpoint. Since the endpoint is only associated with rtb-11111111 and rtb-22222222, but rtb-11111111 lacks the required prefix list route, traffic from that subnet cannot reach S3 via the endpoint.
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 route table rtb-11111111 does not have a route to the S3 prefix list with the target as the VPC endpoint.
Why this is correct
Without this route, traffic to S3 does not go through the endpoint.
- ✗
The endpoint policy denies access to S3 from the instance's IAM role.
Why it's wrong here
The policy allows all principals and actions.
- ✗
The security group on the EC2 instance does not allow outbound traffic to the S3 prefix list.
Why it's wrong here
Security groups do not control traffic to a Gateway endpoint; they control traffic to IP addresses.
- ✗
The VPC does not have DNS resolution enabled for the endpoint.
Why it's wrong here
DNS resolution is not required for Gateway endpoints; they use prefix lists.
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
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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.