The answer is that the IAM role for Flow Logs lacks the necessary permissions to write to S3. This is correct because VPC Flow Logs require a specific IAM role—either a service-linked role or a custom role—that includes a trust policy allowing the flow logs service to assume it, along with an attached policy granting `s3:PutObject` and `s3:GetBucketAcl` actions on the target S3 bucket. Without these permissions, the flow logs service cannot deliver log files, even if the bucket policy is permissive. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of the IAM role dependency for flow log delivery to S3, often appearing as a distractor where candidates mistakenly blame bucket policies or network ACLs. A common trap is assuming the bucket policy alone controls access, but the IAM role is the gatekeeper for the service itself. Memory tip: think “Flow Logs need a role to roll logs”—if the role can’t write, the logs won’t flow.
ANS-C01 Network Management and Operations Practice Question
This ANS-C01 practice question tests your understanding of network management and operations. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 network administrator is setting up VPC Flow Logs to monitor traffic to an Amazon RDS instance. The logs are sent to Amazon S3. After enabling Flow Logs, the administrator notices that no logs are being delivered. 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.
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 for Flow Logs does not have permissions to write to S3
Flow Logs require a service-linked role or an IAM role with permissions to publish to S3. If the role is missing or incorrect, logs will not be delivered.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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 Flow Logs are not enabled for the correct VPC
Why it's wrong here
The administrator enabled them, so they are enabled.
✓
The IAM role for Flow Logs does not have permissions to write to S3
Why this is correct
Flow Logs need an IAM role with s3:PutObject permission on the bucket.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Flow Logs capture all traffic regardless of subnet type.
✗
The S3 bucket is in a different region
Why it's wrong here
S3 is global; cross-region delivery is allowed.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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 block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
Network Management and Operations — This question tests Network Management and Operations — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The IAM role for Flow Logs does not have permissions to write to S3 — Flow Logs require a service-linked role or an IAM role with permissions to publish to S3. If the role is missing or incorrect, logs will not be delivered.
What should I do if I get this ANS-C01 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
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?
CIDR notation defines the prefix length.
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Question Discussion
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