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Control Plane Policing (CoPP)hardMultiple SelectObjective-mapped

CoPP Misconfiguration Symptoms — Flapping Neighbors and High CPU | Cisco CCNP ENARSI 300-410 Explained

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.

Which THREE symptoms indicate that Control Plane Policing (CoPP) might be misconfigured or causing connectivity issues? (Choose THREE.)

Quick Answer

The answer is flapping neighbors, intermittent management access, and high CPU utilization despite CoPP being configured. These three symptoms directly indicate a CoPP misconfiguration because Control Plane Policing is designed to protect the CPU by rate-limiting unwanted traffic, but when misapplied, it can inadvertently drop critical control plane packets like routing protocol hellos or SSH keepalives, causing neighbor adjacencies to flap and remote access to become unreliable. On the Cisco CCNP ENARSI 300-410 exam, this topic tests your ability to distinguish CoPP failure symptoms from unrelated issues—a common trap is confusing high CPU with low CPU, but remember that misconfigured CoPP fails to filter the offending traffic, leaving the CPU overloaded. A useful memory tip is "Flap, Drop, and Spike"—neighbors flap, management drops, and CPU spikes—to recall the three hallmark signs of a CoPP misconfiguration.

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

OSPF or BGP neighbors are flapping, with log messages indicating adjacency timeouts.

Option A is correct because CoPP is designed to protect the control plane by rate-limiting traffic. If CoPP is misconfigured with overly restrictive policies, it can drop OSPF or BGP hello packets, causing neighbor adjacencies to time out and flap. Log messages showing adjacency timeouts directly point to control plane packet loss, a classic symptom of CoPP misconfiguration.

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.

  • OSPF or BGP neighbors are flapping, with log messages indicating adjacency timeouts.

    Why this is correct

    If CoPP drops routing protocol hello packets, neighbors may flap, indicating misclassification or overly restrictive policing.

    Related concept

    Read the scenario before looking for a memorised answer.

  • SSH or Telnet sessions to the device are intermittent or time out.

    Why this is correct

    CoPP that polices management traffic too aggressively can cause session drops or timeouts.

    Related concept

    Read the scenario before looking for a memorised answer.

  • CPU utilization remains high despite CoPP being configured.

    Why this is correct

    If CoPP is misconfigured (e.g., not matching the attacking traffic), unwanted packets still reach the CPU, keeping utilization high.

    Related concept

    Read the scenario before looking for a memorised answer.

  • CPU utilization is consistently low, and all control plane traffic is passing without drops.

    Why it's wrong here

    Low CPU and no drops suggest CoPP is working correctly, not misconfigured.

  • Throughput on data interfaces increases significantly.

    Why it's wrong here

    Data plane throughput is not directly affected by CoPP, which only polices control plane traffic.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Cisco often tests the misconception that CoPP only affects management traffic (SSH/Telnet), but candidates forget that routing protocol packets (OSPF, BGP) are also control plane traffic and can be dropped by CoPP, causing neighbor flapping.

Detailed technical explanation

How to think about this question

CoPP uses MQC (Modular QoS CLI) to classify and rate-limit traffic destined to the control plane. A common misconfiguration is applying a 'drop' action to protocol-specific classes (e.g., OSPF, BGP) without proper rate values, or forgetting to include an 'explicit permit' for critical protocols. In real-world scenarios, an overly aggressive CoPP policy can cause routing protocol flapping, leading to network instability that is difficult to diagnose without checking control plane packet drops via 'show policy-map control-plane'.

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 network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.

Visual reference

R1 R2 R3 R4 10 100 10 100 OSPF picks R1→R2→R4 (cost 20) over R1→R3→R4 (cost 200)

Quick reference

Routing Protocol Comparison

ProtocolMetricMax HopsAlgorithmType
RIP v2Hop count15Bellman-FordDistance vector
OSPFCost (bandwidth)UnlimitedDijkstra (SPF)Link state
EIGRPComposite metricUnlimitedDUALHybrid
IS-ISCostUnlimitedDijkstraLink state
BGPPolicy / attributesUnlimitedPath vectorPath vector

RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.

What to study next

Got this wrong? Here's your next step.

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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) — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: OSPF or BGP neighbors are flapping, with log messages indicating adjacency timeouts. — Option A is correct because CoPP is designed to protect the control plane by rate-limiting traffic. If CoPP is misconfigured with overly restrictive policies, it can drop OSPF or BGP hello packets, causing neighbor adjacencies to time out and flap. Log messages showing adjacency timeouts directly point to control plane packet loss, a classic symptom of CoPP misconfiguration.

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

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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Last reviewed: Jul 4, 2026

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