This DVA-C02 practice question tests your understanding of security. 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.
A developer is troubleshooting an issue where an EC2 instance cannot access an S3 bucket despite having an IAM role with the correct permissions attached. Which THREE steps should the developer take to diagnose the issue?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use the AWS CLI command 'aws sts assume-role' to test the role credentials.
Option A, C, and E are correct. Option A verifies permissions. Option C checks if the instance actually has the role. Option E ensures the instance is in the correct region or service is up. Option B is wrong because modifying the bucket policy is not a diagnostic step. Option D is wrong because security groups do not affect S3 access via IAM roles.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Use the AWS CLI command 'aws sts assume-role' to test the role credentials.
Why this is correct
Helps verify role trust and permissions.
Related concept
Standard ACLs match source addresses.
✗
Check the security group of the EC2 instance for outbound rules.
Why it's wrong here
Security groups do not affect S3 via IAM.
✓
Check the IAM policy attached to the role for any explicit Deny statements.
Why this is correct
Explicit denies override allows.
Related concept
Standard ACLs match source addresses.
✓
Verify that the IAM role is correctly associated with the EC2 instance.
Why this is correct
Instance profile must be attached.
Related concept
Standard ACLs match source addresses.
✗
Modify the S3 bucket policy to grant access to the instance's security group.
Why it's wrong here
Security groups are not used for S3 access.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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.
What to study next
Got this wrong? Here's your next step.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related DVA-C02 ACL questions on filtering logic and placement.
Security — This question tests Security — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Use the AWS CLI command 'aws sts assume-role' to test the role credentials. — Option A, C, and E are correct. Option A verifies permissions. Option C checks if the instance actually has the role. Option E ensures the instance is in the correct region or service is up. Option B is wrong because modifying the bucket policy is not a diagnostic step. Option D is wrong because security groups do not affect S3 access via IAM roles.
What should I do if I get this DVA-C02 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related DVA-C02 ACL questions on filtering logic and placement.
What is the key concept behind this question?
Standard ACLs match source addresses.
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Question Discussion
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