The answer is that the instance profile is not attached to the EC2 instance. This is the most likely cause of the access failure because an EC2 instance profile serves as the container that delivers the IAM role’s temporary credentials to the instance; without this attachment, the instance has no mechanism to assume the role, regardless of how correctly the trust policy or S3 bucket policy are configured. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of the fundamental IAM credential delivery chain, often appearing as a trap where candidates focus on policy syntax errors instead of the missing attachment. A common memory tip is to think of the instance profile as the physical “key slot” on the EC2 instance—without inserting the key (the profile), the role’s permissions remain locked away. Remember: attach first, then policies matter.
ANS-C01 Network Design Practice Question
This ANS-C01 practice question tests your understanding of network design. 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.
Refer to the exhibit. An AWS administrator is troubleshooting an issue where an EC2 instance cannot access an S3 bucket using an instance profile. The instance profile is associated with an IAM role that has the above trust policy. The S3 bucket policy allows s3:GetObject only for the role's ARN. What is the most likely cause of the access failure?
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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The instance profile is not attached to the EC2 instance
The instance profile must be attached to the EC2 instance for the IAM role's credentials to be available to the instance. Without this attachment, the EC2 instance cannot assume the role or use its permissions to access the S3 bucket, even if the trust policy and bucket policy are correctly configured.
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 VPC does not have an S3 VPC endpoint
Why it's wrong here
VPC endpoint is not required if the instance has internet access.
✓
The instance profile is not attached to the EC2 instance
Why this is correct
Without the instance profile, the EC2 instance cannot assume the role.
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 S3 bucket policy does not allow s3:ListBucket
Why it's wrong here
The bucket policy allows GetObject, but the role must be assumed first.
✗
The trust policy does not allow the S3 service to assume the role
Why it's wrong here
The trust policy is for EC2, not S3.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often overlook the instance profile attachment step and instead focus on policy misconfigurations, assuming the trust policy or bucket policy is the issue when the real problem is the missing link between the instance and the role.
Detailed technical explanation
How to think about this question
When an instance profile is attached to an EC2 instance, the AWS credentials provider on the instance retrieves temporary security credentials from the IAM role via the instance metadata service (IMDS) at http://169.254.169.254/latest/meta-data/iam/security-credentials/. The SDK then uses these credentials to sign API requests to S3. If the instance profile is not attached, the metadata endpoint returns an empty response, and the SDK cannot obtain credentials, causing an access failure.
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.
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 Design — This question tests Network Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The instance profile is not attached to the EC2 instance — The instance profile must be attached to the EC2 instance for the IAM role's credentials to be available to the instance. Without this attachment, the EC2 instance cannot assume the role or use its permissions to access the S3 bucket, even if the trust policy and bucket policy are correctly configured.
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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