The answer is that the IAM role lacks a permissions policy granting the required actions on the CloudWatch Logs log group. While the trust policy correctly allows the VPC Flow Logs service principal to assume the role, it does not authorize the role to perform any actions—such as creating log streams or putting log events—against the log group itself. For VPC Flow Log IAM role permissions to function, the role must include a separate, attached permissions policy that explicitly allows these specific CloudWatch Logs actions on the target log group ARN. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding that trust and permissions policies serve distinct purposes; a common trap is assuming a valid trust policy alone is sufficient. Remember the two-policy rule: trust for “who can assume,” permissions for “what they can do.” A quick memory tip: “Trust lets them in, permissions let them act.”
ANS-C01 Network Management and Operations Practice Question
This ANS-C01 practice question tests your understanding of network management and operations. 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.
An engineer is trying to create a VPC Flow Log that delivers to a CloudWatch Logs log group in the same account. The IAM role used has the above trust policy. However, the flow log creation fails with an error. What is the most likely reason?
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 IAM role lacks a permissions policy that grants the actions on the log group.
The trust policy shown trusts the VPC Flow Logs service principal, but the IAM role itself must have a permissions policy that allows the actions on the log group. The exhibit only shows the trust policy; the permissions policy is missing. The error likely indicates that the role does not have the necessary permissions to perform the actions.
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 log group does not exist yet.
Why it's wrong here
The Flow Logs service can create the log group if the role has permission; the error is not about existence.
✗
The trust policy incorrectly specifies the service principal; it should be 'ec2.amazonaws.com'.
Why it's wrong here
The correct service principal for VPC Flow Logs is 'vpc-flow-logs.amazonaws.com'.
✓
The IAM role lacks a permissions policy that grants the actions on the log group.
Why this is correct
The trust policy allows the service to assume the role, but the role needs a permissions policy to perform the actions.
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 resource ARN in the trust policy does not include the log group name.
Why it's wrong here
The trust policy does not require resource ARN; it trusts the service.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
Identify which ANS-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Network Management and Operations — This question tests Network Management and Operations — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The IAM role lacks a permissions policy that grants the actions on the log group. — The trust policy shown trusts the VPC Flow Logs service principal, but the IAM role itself must have a permissions policy that allows the actions on the log group. The exhibit only shows the trust policy; the permissions policy is missing. The error likely indicates that the role does not have the necessary permissions to perform the actions.
What should I do if I get this ANS-C01 question wrong?
Identify which ANS-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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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