The answer is that the CoPP policy has a conform-action of drop, which drops all traffic matching the class. This is the most likely cause because in Cisco’s Control Plane Policing, the conform-action defines what happens to packets that fall within the configured police rate; when set to drop, every packet matching the class-map is discarded immediately, regardless of whether the traffic rate is below the policer’s threshold. In this scenario, legitimate DSCP AF41 traffic at only 5 Mbps is being dropped because the conform-action overrides the rate check entirely. On the ENCOR 350-401 exam, this question tests your understanding of CoPP policer actions versus rate-based filtering—a common trap is assuming that traffic below the police rate is always permitted. Remember that the default conform-action is transmit, so if you see unexpected drops, always verify the explicit action in the policy-map. A useful memory tip: “Conform-action drop means every packet must stop—rate doesn’t matter, the action is the cop.”
CCNP ACLs and CoPP Practice Question
This 350-401 practice question tests your understanding of acls and copp. 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 engineer is configuring CoPP on a Cisco Nexus 9000 switch to protect the control plane from a potential DoS attack. The engineer creates a class-map that matches traffic with a specific DSCP value (AF41) and applies a police rate of 10 Mbps. After applying the policy, the engineer notices that legitimate traffic with DSCP AF41 is being dropped even though the traffic rate is only 5 Mbps. 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 CoPP policy has a conform-action of drop, which drops all traffic matching the class.
The correct answer is that the CoPP policy is using a conform-action of drop, which drops all traffic that matches the class, regardless of rate. Option B is incorrect because the police rate is not exceeded. Option C is incorrect because DSCP AF41 is a valid value. Option D is incorrect because CoPP does not require a specific queue; it uses policing.
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.
✓
The CoPP policy has a conform-action of drop, which drops all traffic matching the class.
Why this is correct
Correct because if the conform-action is set to drop, all traffic in that class is dropped, even if it is within the police rate.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The police rate is too low, and the traffic is being dropped due to exceeding the rate.
Why it's wrong here
Incorrect because the traffic rate is 5 Mbps, which is below the 10 Mbps police rate.
✗
The DSCP value AF41 is not supported on Nexus switches.
Why it's wrong here
Incorrect because DSCP AF41 is supported on Nexus switches.
✗
The CoPP policy is applied to the wrong queue, causing all traffic to be dropped.
Why it's wrong here
Incorrect because CoPP policies are applied to the control plane, not queues.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 practitioner preparing for the 350-401 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which 350-401 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
ACLs and CoPP — This question tests ACLs and CoPP — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The CoPP policy has a conform-action of drop, which drops all traffic matching the class. — The correct answer is that the CoPP policy is using a conform-action of drop, which drops all traffic that matches the class, regardless of rate. Option B is incorrect because the police rate is not exceeded. Option C is incorrect because DSCP AF41 is a valid value. Option D is incorrect because CoPP does not require a specific queue; it uses policing.
What should I do if I get this 350-401 question wrong?
Identify which 350-401 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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?
Read the scenario before looking for a memorised answer.
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Question Discussion
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