200-201 Network Intrusion Analysis Practice Question
This 200-201 practice question tests your understanding of network intrusion analysis. 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.
An IPS sensor is configured inline and drops traffic that triggers the signature 'OVERFLOW-ICMP-ECHO', which triggers on ICMP packets with size > 1024 bytes. A network administrator reports that legitimate network monitoring tools using large ICMP packets are being blocked. What is the best course of action?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Why wrong: Increasing the threshold may still not accommodate all legitimate tools and reduces detection.
B
Create a whitelist for the monitoring tool's source IP
A whitelist permits specific IPs to bypass the signature while keeping detection for others.
C
Disable the signature entirely
Why wrong: Disabling removes protection against ICMP overflow attacks.
D
Change the sensor mode to IDS for that signature
Why wrong: Changing to IDS mode would generate alerts but still block traffic? Actually inline IDS mode is not typical; if sensor is inline, changing to alert only may still drop? Better to whitelist.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a whitelist for the monitoring tool's source IP
Option B is correct because creating a whitelist for the monitoring tool's source IP allows the IPS to continue dropping malicious oversized ICMP packets while permitting legitimate traffic from known, trusted sources. This maintains security for the rest of the network without disabling the signature or changing its mode, which would reduce protection.
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.
✗
Increase the threshold to 2048
Why it's wrong here
Increasing the threshold may still not accommodate all legitimate tools and reduces detection.
✓
Create a whitelist for the monitoring tool's source IP
Why this is correct
A whitelist permits specific IPs to bypass the signature while keeping detection for others.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Disable the signature entirely
Why it's wrong here
Disabling removes protection against ICMP overflow attacks.
✗
Change the sensor mode to IDS for that signature
Why it's wrong here
Changing to IDS mode would generate alerts but still block traffic? Actually inline IDS mode is not typical; if sensor is inline, changing to alert only may still drop? Better to whitelist.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that you should adjust the signature threshold (option A) to fix false positives, but the correct approach is to use a whitelist or exception rule to allow known legitimate traffic without weakening the overall security posture.
Detailed technical explanation
How to think about this question
In an inline IPS configuration, the sensor actively drops packets that match a signature, unlike an IDS which only logs alerts. The 'OVERFLOW-ICMP-ECHO' signature typically targets ICMP echo requests exceeding the standard 64-byte payload (RFC 792), but many network monitoring tools (e.g., ping with large payloads for MTU testing) legitimately use packets larger than 1024 bytes. A whitelist based on source IP is a precise exception that preserves the signature's protection for all other traffic while allowing trusted sources to pass.
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.
TExam Day Tips
→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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Network Intrusion Analysis — This question tests Network Intrusion Analysis — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create a whitelist for the monitoring tool's source IP — Option B is correct because creating a whitelist for the monitoring tool's source IP allows the IPS to continue dropping malicious oversized ICMP packets while permitting legitimate traffic from known, trusted sources. This maintains security for the rest of the network without disabling the signature or changing its mode, which would reduce protection.
What should I do if I get this 200-201 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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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