Question 406 of 2,152

Control Plane Policing (CoPP) →hardMultiple ChoiceObjective-mapped

Quick Answer

The answer is that the CoPP policy is causing packet loss for traffic that exceeds the 8 kbps rate, which may impact legitimate control plane traffic. This is correct because the output from the show policy-map control-plane input class CoPP-Class command reveals a clear mismatch: the offered rate is 10 kbps, but the committed information rate (CIR) is only 8 kbps, causing the policer to drop 500 packets in the exceeded bucket. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your ability to interpret CoPP police statistics and identify packet drops, specifically recognizing that a drop rate of 5000 bps alongside a conformed rate of 8000 bps indicates legitimate traffic is being throttled. A common trap is focusing only on the conformed packets count while ignoring the exceeded actions—remember that the drop rate always subtracts from the offered rate. Memory tip: “Offered minus CIR equals drop risk”—if the offered rate exceeds the CIR, expect drops in the exceeded bucket.

300-410 Control Plane Policing (CoPP) Practice Question

This 300-410 practice question tests your understanding of control plane policing (copp). 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 network engineer runs the following command to troubleshoot a Control Plane Policing (CoPP) issue:

R1# show policy-map control-plane input class CoPP-Class

Class-map: CoPP-Class (match-all) 1500 packets, 120000 bytes 5 minute offered rate 10000 bps, drop rate 5000 bps Match: access-group name CoPP-ACL police: cir 8000 bps, bc 1500 bytes, be 1500 bytes conformed 1000 packets, 80000 bytes; actions: transmit exceeded 500 packets, 40000 bytes; actions: drop conformed 8000 bps, exceed 2000 bps, violated 0 bps

What does this output indicate?

Question 1hardmultiple choice

Study the full ACL explanation →

A
The CoPP policy is dropping all traffic because the CIR is too low.
Why wrong: Only exceeding packets are dropped; conforming traffic is transmitted.
B
The CoPP policy is causing packet loss for traffic that exceeds the 8 kbps rate, which may impact legitimate control plane traffic.
The drop rate of 5 kbps indicates that half the offered traffic is being dropped, which could affect protocols like OSPF or BGP.
C
The CoPP policy is not applied correctly because the drop rate is higher than the conform rate.
Why wrong: This is expected behavior when the offered rate exceeds the CIR.
D
The CoPP policy is working as intended with no issues.
Why wrong: The high drop rate suggests a potential problem if the dropped traffic includes critical control plane packets.

Full breakdown with real-world context →

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 CoPP policy is causing packet loss for traffic that exceeds the 8 kbps rate, which may impact legitimate control plane traffic.

The output shows that the CoPP policy is policing traffic matching the CoPP-ACL. The offered rate is 10 kbps, but the CIR is 8 kbps, resulting in 500 packets exceeding the rate and being dropped. This indicates that control plane traffic is being throttled.

Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.

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 is dropping all traffic because the CIR is too low.
Why it's wrong here
Only exceeding packets are dropped; conforming traffic is transmitted.
✓
The CoPP policy is causing packet loss for traffic that exceeds the 8 kbps rate, which may impact legitimate control plane traffic.
Why this is correct
The drop rate of 5 kbps indicates that half the offered traffic is being dropped, which could affect protocols like OSPF or BGP.
Related concept
Standard ACLs match source addresses.
✗
The CoPP policy is not applied correctly because the drop rate is higher than the conform rate.
Why it's wrong here
This is expected behavior when the offered rate exceeds the CIR.
✗
The CoPP policy is working as intended with no issues.
Why it's wrong here
The high drop rate suggests a potential problem if the dropped traffic includes critical control plane packets.

Common exam traps

Common exam trap: ACLs stop at the first match

ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.

Detailed technical explanation

How to think about this question

ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.

KKey Concepts to Remember

Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.

TExam Day Tips

Check inbound versus outbound direction.
Read the ACL from top to bottom.
Look for a broader permit or deny above the intended line.

Key takeaway

ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.

Real-world example

How this comes up in practice

A security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.

What to study next

Got this wrong? Here's your next step.

Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related 300-410 ACL questions on filtering logic and placement.

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FAQ

Questions learners often ask

What does this 300-410 question test?

Control Plane Policing (CoPP) — This question tests Control Plane Policing (CoPP) — Standard ACLs match source addresses..

What is the correct answer to this question?

The correct answer is: The CoPP policy is causing packet loss for traffic that exceeds the 8 kbps rate, which may impact legitimate control plane traffic. — The output shows that the CoPP policy is policing traffic matching the CoPP-ACL. The offered rate is 10 kbps, but the CIR is 8 kbps, resulting in 500 packets exceeding the rate and being dropped. This indicates that control plane traffic is being throttled.

What should I do if I get this 300-410 question wrong?

What is the key concept behind this question?

Standard ACLs match source addresses.

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