- A
The rate-based rule is set to block requests for 24 hours after the threshold is exceeded, and once triggered, all requests from that IP are blocked indefinitely.
Why wrong: Rate-based rules typically block for a short duration (e.g., 5 minutes). AWS WAF rate-based rules block for the duration of the rate window plus a few minutes. Not indefinitely.
- B
The WAF web ACL is associated with an Application Load Balancer that is not configured for sticky sessions, causing requests from the same user to be distributed across multiple IPs.
Why wrong: Sticky sessions do not affect rate limiting based on source IP. Rate limiting aggregates by IP regardless of load balancer distribution.
- C
The rate-based rule uses the source IP address as the aggregation key, and legitimate users behind a NAT gateway share the same public IP, causing the aggregate rate to exceed the threshold.
When multiple legitimate users share a single public IP (e.g., via NAT), their combined requests can exceed the rate limit, causing blocking of all users behind that IP.
- D
The rate-based rule is evaluating requests before the WAF allows them, and the threshold is too low, but the rule action is set to 'count' instead of 'block', so it should not block traffic.
Why wrong: If the action is 'count', it would not block. The stem says legitimate users were blocked, so the action must be 'block'.
Quick Answer
The answer is that legitimate users were blocked because the rate-based rule aggregates requests by source IP address, and users behind a NAT gateway all share the same public IP, causing the combined traffic to exceed the threshold of 100 requests per 5 minutes. This occurs because AWS WAF rate-based rules count all requests from a single source IP against the limit, so during a DDoS attack, the NAT gateway’s public IP becomes a bottleneck—even normal user traffic from different private IPs is lumped together, triggering rate limiting for everyone behind that IP. On the ANS-C01 exam, this scenario tests your understanding of how WAF rate-based rules interact with network address translation, a common trap where candidates overlook the aggregation key’s behavior. A key memory tip: think of a NAT gateway as a single “megaphone” for many voices—if the megaphone shouts too much, everyone gets muted.
ANS-C01 Network Security, Compliance and Governance Practice Question
This ANS-C01 practice question tests your understanding of network security, compliance and governance. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 uses AWS Shield Advanced to protect their web application against DDoS attacks. They have configured automatic application layer DDoS mitigation with AWS WAF. During a recent attack, the application experienced increased latency, and some legitimate users were blocked. The security team reviews the WAF logs and finds that many requests from legitimate IPs were rate-limited. The team had set a rate-based rule with a threshold of 100 requests per 5 minutes. What is the most likely reason legitimate users were blocked?
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 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 rate-based rule uses the source IP address as the aggregation key, and legitimate users behind a NAT gateway share the same public IP, causing the aggregate rate to exceed the threshold.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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.
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 rate-based rule is set to block requests for 24 hours after the threshold is exceeded, and once triggered, all requests from that IP are blocked indefinitely.
Why it's wrong here
Rate-based rules typically block for a short duration (e.g., 5 minutes). AWS WAF rate-based rules block for the duration of the rate window plus a few minutes. Not indefinitely.
- ✗
The WAF web ACL is associated with an Application Load Balancer that is not configured for sticky sessions, causing requests from the same user to be distributed across multiple IPs.
Why it's wrong here
Sticky sessions do not affect rate limiting based on source IP. Rate limiting aggregates by IP regardless of load balancer distribution.
- ✓
The rate-based rule uses the source IP address as the aggregation key, and legitimate users behind a NAT gateway share the same public IP, causing the aggregate rate to exceed the threshold.
Why this is correct
When multiple legitimate users share a single public IP (e.g., via NAT), their combined requests can exceed the rate limit, causing blocking of all users behind that IP.
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 rate-based rule is evaluating requests before the WAF allows them, and the threshold is too low, but the rule action is set to 'count' instead of 'block', so it should not block traffic.
Why it's wrong here
If the action is 'count', it would not block. The stem says legitimate users were blocked, so the action must be 'block'.
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 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.
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.
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FAQ
Questions learners often ask
What does this ANS-C01 question test?
Network Security, Compliance and Governance — This question tests Network Security, Compliance and Governance — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The rate-based rule uses the source IP address as the aggregation key, and legitimate users behind a NAT gateway share the same public IP, causing the aggregate rate to exceed the threshold.
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.
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Last reviewed: Jun 20, 2026
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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