ANS-C01 Network Management and Operations Practice Question
A company has a VPC with multiple EC2 instances that need to access an Amazon S3 bucket. The network team wants to ensure that traffic to S3 stays within the AWS network and does not traverse the internet. The VPC has a VPC endpoint for S3 (Gateway type). The team has created the endpoint and attached the appropriate policy allowing access to the specific S3 bucket. However, EC2 instances in a private subnet cannot access the S3 bucket. The private subnet route table has a default route pointing to a NAT Gateway. Which change should the network team make to allow private instances to access S3 via 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
✓
Add a route in the private subnet route table for the S3 prefix list (com.amazonaws.region.s3) pointing to the VPC endpoint.
For a Gateway VPC endpoint to work, the route table associated with the subnet must include a route for the S3 prefix list (e.g., com.amazonaws.region.s3) pointing to the endpoint ID. The existing default route to the NAT Gateway would otherwise route S3 traffic to the internet, bypassing the endpoint. Adding the specific route for the S3 prefix list ensures that traffic destined for S3 uses the VPC endpoint and stays within the AWS network. Therefore, option D is correct.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Modify the VPC endpoint policy to allow all principals.
Why it's wrong here
Policy may already be correct; the issue is routing.
- ✗
Change the private subnet route table's default route to point to the VPC endpoint.
Why it's wrong here
Default route should point to NAT for internet access, not to the endpoint.
- ✗
Remove the default route from the private subnet route table.
Why it's wrong here
Removing default route would break internet access and cause asymmetric routing.
- ✓
Add a route in the private subnet route table for the S3 prefix list (com.amazonaws.region.s3) pointing to the VPC endpoint.
Why this is correct
This ensures S3 traffic uses the endpoint instead of the NAT Gateway.
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.