- A
Flow Logs are published to an S3 bucket instead of CloudWatch Logs.
Why wrong: Flow Logs can be published to either; both work.
- B
The traffic uses UDP protocol.
Why wrong: Flow Logs support all IP protocols.
- C
The traffic is blocked by a security group rule.
Why wrong: Flow Logs capture accepted traffic even if it is subsequently blocked by security groups? Actually, Flow Logs capture traffic that is accepted by the network ACL, but security groups are stateful; if traffic is accepted at the security group, it is logged. However, if traffic is rejected by security group, it is still logged as 'REJECT' if the NACL accepts it. So blocked traffic would appear.
- D
The traffic is to or from the Amazon DNS server (169.254.169.253).
By default, Flow Logs do not record traffic to the Amazon DNS server.
Quick Answer
The correct answer is that VPC Flow Logs do not capture traffic to or from the Amazon DNS server at 169.254.169.253 by default. This is because the AWS DNS resolver operates on a reserved link-local address, and Flow Logs are designed to exclude this internal metadata traffic unless you explicitly enable DNS logging through a separate configuration. On the AWS Certified Security Specialty SCS-C02 exam, this concept tests your understanding of what Flow Logs actually monitor—they capture all accepted and rejected IP traffic (not just TCP) but have specific exclusions, with Amazon DNS being a common blind spot. A frequent trap is assuming all traffic is logged, so remember that traffic to 169.254.169.253 is invisible unless you specifically enable DNS query logging. Memory tip: think of 169.254 as the "silent neighbor"—it never shows up in your Flow Logs unless you invite it.
SCS-C02 Infrastructure Security Practice Question
This SCS-C02 practice question tests your understanding of infrastructure security. 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 company has a VPC with multiple subnets and uses VPC Flow Logs to capture network traffic. The security team notices that some expected traffic is not appearing in the logs. What is a likely cause?
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
The traffic is to or from the Amazon DNS server (169.254.169.253).
Option B is correct because Flow Logs do not capture traffic to the Amazon DNS server (unless you specifically enable that). Option A is wrong because Flow Logs can be published to CloudWatch Logs. Option C is wrong because Flow Logs capture accepted traffic even if it is rejected later. Option D is wrong because Flow Logs capture all IP traffic, not just TCP.
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.
- ✗
Flow Logs are published to an S3 bucket instead of CloudWatch Logs.
Why it's wrong here
Flow Logs can be published to either; both work.
- ✗
The traffic uses UDP protocol.
Why it's wrong here
Flow Logs support all IP protocols.
- ✗
The traffic is blocked by a security group rule.
Why it's wrong here
Flow Logs capture accepted traffic even if it is subsequently blocked by security groups? Actually, Flow Logs capture traffic that is accepted by the network ACL, but security groups are stateful; if traffic is accepted at the security group, it is logged. However, if traffic is rejected by security group, it is still logged as 'REJECT' if the NACL accepts it. So blocked traffic would appear.
- ✓
The traffic is to or from the Amazon DNS server (169.254.169.253).
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 SCS-C02 subnetting questions on CIDR, address ranges, and subnet selection.
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FAQ
Questions learners often ask
What does this SCS-C02 question test?
Infrastructure Security — This question tests Infrastructure Security — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The traffic is to or from the Amazon DNS server (169.254.169.253). — Option B is correct because Flow Logs do not capture traffic to the Amazon DNS server (unless you specifically enable that). Option A is wrong because Flow Logs can be published to CloudWatch Logs. Option C is wrong because Flow Logs capture accepted traffic even if it is rejected later. Option D is wrong because Flow Logs capture all IP traffic, not just TCP.
What should I do if I get this SCS-C02 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 SCS-C02 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Last reviewed: Jun 20, 2026
This SCS-C02 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 SCS-C02 exam.
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