ANS-C01 Network Management and Operations Practice Question
A network engineer is troubleshooting an issue where an EC2 instance in a VPC cannot reach an S3 bucket via a gateway endpoint. The instance is in a private subnet with a route table that has a route for the S3 prefix list pointing to the gateway endpoint. Which TWO actions should the engineer take to diagnose the problem?
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
✓
Verify that the route table for the subnet includes a route for the S3 prefix list (com.amazonaws.region.s3) with target type gateway endpoint.
The correct diagnostic steps are A (verify the route table has the S3 prefix list route to the gateway endpoint) and E (check the security group allows outbound HTTPS). The route table must include the prefix list route for the gateway endpoint to work, and the security group must permit HTTPS (443) outbound because S3 API calls use HTTPS. Option B is incorrect because gateway endpoints are used for S3, not interface endpoints (which are for other services). Option C is incorrect; although VPC Flow Logs can help analyze traffic after initial checks, they are not the first diagnostic step. Option D is incorrect because the instance does not need a public IP; gateway endpoints route traffic within the AWS network without leaving the VPC directly.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Verify that the route table for the subnet includes a route for the S3 prefix list (com.amazonaws.region.s3) with target type gateway endpoint.
Why this is correct
Without this route, traffic goes to NAT/IGW.
- ✗
Ensure the VPC has an interface endpoint for S3.
Why it's wrong here
Gateway endpoint is separate and does not require interface endpoint.
- ✗
Review VPC Flow Logs for the subnet to see if traffic is being dropped.
Why it's wrong here
Flow Logs are useful but not the first step.
- ✗
Confirm that the EC2 instance has a public IP address.
Why it's wrong here
Gateway endpoints do not require public IP.
- ✓
Check the security group associated with the EC2 instance to ensure it allows outbound HTTPS (443) traffic.
Why this is correct
S3 uses HTTPS; outbound must be allowed.
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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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.