This ANS-C01 practice question tests your understanding of network implementation. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
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?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Network Topology
A
The route table rtb-11111111 does not have a route to the S3 prefix list with the target as the VPC endpoint.
Without this route, traffic to S3 does not go through the endpoint.
B
The endpoint policy denies access to S3 from the instance's IAM role.
Why wrong: The policy allows all principals and actions.
C
The security group on the EC2 instance does not allow outbound traffic to the S3 prefix list.
Why wrong: Security groups do not control traffic to a Gateway endpoint; they control traffic to IP addresses.
D
The VPC does not have DNS resolution enabled for the endpoint.
Why wrong: DNS resolution is not required for Gateway endpoints; they use prefix lists.
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.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
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.
Detailed technical explanation
How to think about this question
Gateway Endpoints leverage prefix lists (e.g., com.amazonaws.us-east-1.s3) that are automatically managed by AWS and represent the IP address ranges for the service. The route table entry with the prefix list as the destination and the endpoint ID as the target ensures that traffic to S3 stays within the AWS network, avoiding internet egress. A common misconfiguration is associating the endpoint with a route table but forgetting to add the actual route, which is a two-step process: first associate the route table, then add the route.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Network Implementation — This question tests Network Implementation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 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.
What should I do if I get this ANS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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