- A
Use the AWS CLI command 'aws sts assume-role' to test the role credentials.
Helps verify role trust and permissions.
- B
Check the security group of the EC2 instance for outbound rules.
Why wrong: Security groups do not affect S3 via IAM.
- C
Check the IAM policy attached to the role for any explicit Deny statements.
Explicit denies override allows.
- D
Verify that the IAM role is correctly associated with the EC2 instance.
Instance profile must be attached.
- E
Modify the S3 bucket policy to grant access to the instance's security group.
Why wrong: Security groups are not used for S3 access.
Question 1,095 of 1,616
How to Diagnose EC2 S3 Access Denied Errors
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 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
✓
Use the AWS CLI command 'aws sts assume-role' to test the role credentials.
Options A, C, and D are correct. Option A: Using 'aws sts assume-role' tests whether the instance can obtain temporary credentials for the role, validating that the role is correctly configured and accessible. Option C: Checking for explicit Deny statements in the IAM policy attached to the role helps identify if any deny is overriding the allow permissions. Option D: Verifying that the IAM role is correctly associated with the instance ensures the instance actually has the role attached. Option B is incorrect because security groups control network traffic, not IAM authorization; S3 access via IAM roles does not rely on security group rules. Option E is incorrect because modifying the bucket policy to grant access to a security group is not a diagnostic step; bucket policies grant access to principals (like IAM roles), not security groups, and this action is a fix, not a diagnosis.
Key principle: Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
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
Authentication checks who the user is.
- ✗
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
Authentication checks who the user is.
- ✓
Verify that the IAM role is correctly associated with the EC2 instance.
Why this is correct
Instance profile must be attached.
Related concept
Authentication checks who the user is.
- ✗
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: authentication is not authorization
Logging in proves the user can authenticate. It does not automatically mean the user is allowed to enter privileged or configuration mode. Watch for AAA authorization, privilege level and command authorization details.
Detailed technical explanation
How to think about this question
This kind of question is testing the difference between identity and permission. A user may successfully log in to a router because authentication is working, but still fail to enter configuration mode because authorization is missing, misconfigured or mapped to a lower privilege level.
KKey Concepts to Remember
- Authentication checks who the user is.
- Authorization controls what the user is allowed to do after login.
- Privilege levels affect access to EXEC and configuration commands.
- AAA, TACACS+ and RADIUS can separate login success from command access.
TExam Day Tips
- Do not assume successful login means full administrative access.
- Look for words such as cannot enter configuration mode, privilege level, authorization or command access.
- Separate login problems from permission problems before choosing the answer.
Key takeaway
Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
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.
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.
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related DVA-C02 questions on access control and AAA configuration.
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FAQ
Questions learners often ask
What does this DVA-C02 question test?
Security — This question tests Security — Authentication checks who the user is..
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. — Options A, C, and D are correct. Option A: Using 'aws sts assume-role' tests whether the instance can obtain temporary credentials for the role, validating that the role is correctly configured and accessible. Option C: Checking for explicit Deny statements in the IAM policy attached to the role helps identify if any deny is overriding the allow permissions. Option D: Verifying that the IAM role is correctly associated with the instance ensures the instance actually has the role attached. Option B is incorrect because security groups control network traffic, not IAM authorization; S3 access via IAM roles does not rely on security group rules. Option E is incorrect because modifying the bucket policy to grant access to a security group is not a diagnostic step; bucket policies grant access to principals (like IAM roles), not security groups, and this action is a fix, not a diagnosis.
What should I do if I get this DVA-C02 question wrong?
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related DVA-C02 questions on access control and AAA configuration.
What is the key concept behind this question?
Authentication checks who the user is.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more ways this is tested on DVA-C02
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A developer is troubleshooting an issue where an EC2 instance cannot access an S3 bucket. The instance has an IAM role with a policy that allows s3:GetObject on the bucket. Which TWO additional checks should the developer perform to resolve the issue?
hard- A.Check the network ACLs for the subnet.
- ✓ B.Check if the S3 bucket policy has an explicit deny statement that affects the EC2 instance.
- C.Check if the EC2 instance is in a VPC with an S3 VPC endpoint configured.
- D.Check the security group rules attached to the EC2 instance.
- ✓ E.Check if the S3 bucket uses SSE-KMS encryption and the EC2 role has kms:Decrypt permissions.
Why B: Option B is correct because S3 bucket policies can explicitly deny access even if the IAM role attached to the EC2 instance grants s3:GetObject. An explicit deny in a bucket policy overrides any allow, so checking for such a deny statement is essential. Option E is correct because if the S3 bucket uses SSE-KMS encryption, the EC2 instance's IAM role must have kms:Decrypt permissions to decrypt the object; without it, GetObject requests will fail.
Keep practising
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Last reviewed: Jun 20, 2026
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