The answer is that the source account lacks an IAM role granting the Flow Logs service permission to write to the central S3 bucket. This is because centralizing VPC flow logs cross account requires the source account to create an IAM role that the vpc-flow-logs service principal can assume, with a trust policy allowing the logging account’s S3 bucket to accept writes. Without this role, the flow logs service in the source account has no valid identity to authenticate against the logging account’s S3 bucket policy, even if that policy permits cross-account writes. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of the service-linked role dependency for cross-account log delivery—a common trap is assuming the S3 bucket policy alone is sufficient. Remember the mnemonic: “Role before bucket” — the IAM role must exist in the source account before the bucket policy can be effective.
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.
A company has multiple AWS accounts and wants to centrally manage VPC flow logs for compliance. The logs should be published to a central S3 bucket in the logging account. The logging account has an S3 bucket policy that allows cross-account writes. However, flow logs are not being delivered. What is the most likely missing configuration?
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 source account lacks an IAM role that grants the Flow Logs service permission to write to the central S3 bucket.
For cross-account flow log delivery, the source account must have an IAM role that trusts the logging account and allows the flow logs service to assume it. The role must have permissions to write to the S3 bucket. Without this role, logs cannot be delivered.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 service is not enabled in the source account.
Why it's wrong here
Flow logs can be created without being enabled globally; it's per VPC.
✗
The S3 bucket policy does not grant 's3:PutObject' to the source account.
Why it's wrong here
The bucket policy is needed, but the missing piece is likely the IAM role in the source account.
✓
The source account lacks an IAM role that grants the Flow Logs service permission to write to the central S3 bucket.
Why this is correct
Cross-account delivery requires an IAM role with appropriate trust and permissions.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
The VPC Flow Logs destination is set to CloudWatch Logs instead of S3.
Why it's wrong here
The question states they want to publish to S3, so destination should be S3.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related ANS-C01 NAT questions on configuration and troubleshooting.
Network Management and Operations — This question tests Network Management and Operations — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The source account lacks an IAM role that grants the Flow Logs service permission to write to the central S3 bucket. — For cross-account flow log delivery, the source account must have an IAM role that trusts the logging account and allows the flow logs service to assume it. The role must have permissions to write to the S3 bucket. Without this role, logs cannot be delivered.
What should I do if I get this ANS-C01 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related ANS-C01 NAT questions on configuration and troubleshooting.
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?
Static NAT maps one inside address to one outside address.
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 →
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 company has multiple AWS accounts and wants to centralize VPC flow logs for analysis. The flow logs are published to Amazon S3 in each account. A central account needs to access these logs. Which solution meets the requirements with the least operational overhead?
medium
A.Set up AWS Glue jobs to copy logs to a central S3 bucket
B.Use AWS Transit Gateway to centralize network traffic and capture logs
C.Use VPC peering to connect the accounts and access the S3 buckets directly
✓ D.Use S3 bucket policies in each account to grant the central account access
Why D: Option C is correct because cross-account bucket policies allow the central account to access logs without additional infrastructure. Option A is wrong because VPC peering does not grant S3 access. Option B is wrong because Transit Gateway does not provide S3 access. Option D is wrong because it adds complexity.
Variation 2. A company wants to centralize VPC flow log management from multiple accounts into a single S3 bucket in the management account. Which combination of AWS services should be used?
easy
A.AWS CloudTrail and Amazon S3
B.AWS Lambda and Amazon S3
C.Amazon Kinesis Data Firehose and Amazon S3
✓ D.AWS Organizations and Amazon S3 bucket policy
Why D: AWS Organizations with SCP can allow cross-account S3 bucket policies. AWS CloudTrail is not needed for flow logs. Option D is correct. Options A, B, and C either miss key services or include unnecessary ones.
Last reviewed: Jun 20, 2026
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This ANS-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the ANS-C01 exam.
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