Question 1,921 of 2,152

NetFlow and Flexible NetFlow →hardMultiple ChoiceObjective-mapped

Flexible NetFlow with CoPP Causing CPU Spike and Management Issues

This 300-410 practice question tests your understanding of netflow and flexible netflow. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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 configures Flexible NetFlow on a router that also runs CoPP (Control Plane Policing). After applying the flow monitor to the ingress interface, the router's CPU spikes and management traffic (SSH, SNMP) becomes intermittent. Router R1 shows: show policy-map control-plane | include (class|police) class CoPP-MGMT police rate 10000 pps. show flow monitor FLOW-MONITOR statistics | include (Packets|Dropped) Packets dropped: 5000. What is the root cause?

A
The flow monitor's cache size is too small, causing packet drops and CPU spikes due to cache overflow.
Why wrong: While cache size could be an issue, the CoPP policy is explicitly rate-limiting management traffic, and NetFlow export uses control plane resources.
B
CoPP is rate-limiting NetFlow export packets because they are classified as management traffic, causing export failures and cache buildup.
NetFlow export packets are sent from the control plane and are subject to CoPP. If the CoPP policy rate-limits management traffic, export packets will be dropped, leading to cache overflow and CPU spikes.
C
The flow exporter is configured with a wrong destination IP, causing all export packets to be dropped by the router.
Why wrong: The show output shows packets dropped by the flow monitor, not by the exporter.
D
The flow monitor is applied in the output direction, causing a loop.
Why wrong: Applying in output direction would not cause CPU spikes; it would affect traffic leaving the interface.

Full breakdown with real-world context →

Quick Answer

The answer is that CoPP is rate-limiting NetFlow export packets because they are classified as management traffic, causing export failures and cache buildup. When Flexible NetFlow is configured on an ingress interface, the router generates export packets that are sent from the control plane; if CoPP polices the management class at a low rate—here, 10,000 pps—these export packets are dropped, preventing the flow monitor from clearing its cache. As the cache fills, the router drops incoming flow records (as shown by the 5,000 dropped packets) and the CPU spikes from the export process repeatedly retrying or the control plane struggling with backlogged traffic. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of how control plane protection policies can inadvertently impact data-plane features like NetFlow, with the common trap being to blame the flow monitor cache size rather than the CoPP classification. Remember: if management traffic becomes intermittent and the flow monitor shows drops, check whether CoPP is starving the export—think “CoPP chokes the flow, cache blows.”

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

✓

CoPP is rate-limiting NetFlow export packets because they are classified as management traffic, causing export failures and cache buildup.

Flexible NetFlow can generate a large number of packets for export, especially if the flow monitor is configured to export all flows. These export packets are sent from the router's control plane, and if CoPP is policing management traffic, the export packets might be classified as management traffic and dropped. However, the show output indicates that the flow monitor itself is dropping packets, which suggests that the flow monitor's cache is full or that the export process is overwhelmed. The correct answer is that the flow monitor's cache is too small, causing packets to be dropped before they can be exported, and the CPU spike is due to the export process consuming resources. But the CoPP is also rate-limiting the export packets, causing further drops. The root cause is that CoPP is rate-limiting the NetFlow export traffic, which is classified as management traffic, causing the export to fail and the cache to fill up.

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 flow monitor's cache size is too small, causing packet drops and CPU spikes due to cache overflow.
Why it's wrong here
While cache size could be an issue, the CoPP policy is explicitly rate-limiting management traffic, and NetFlow export uses control plane resources.
✓
CoPP is rate-limiting NetFlow export packets because they are classified as management traffic, causing export failures and cache buildup.
Why this is correct
NetFlow export packets are sent from the control plane and are subject to CoPP. If the CoPP policy rate-limits management traffic, export packets will be dropped, leading to cache overflow and CPU spikes.
Related concept
Read the scenario before looking for a memorised answer.
✗
The flow exporter is configured with a wrong destination IP, causing all export packets to be dropped by the router.
Why it's wrong here
The show output shows packets dropped by the flow monitor, not by the exporter.
✗
The flow monitor is applied in the output direction, causing a loop.
Why it's wrong here
Applying in output direction would not cause CPU spikes; it would affect traffic leaving the interface.

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.

Trap categories for this question

Command / output trap
The show output shows packets dropped by the flow monitor, not by the exporter.

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 300-410 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 300-410 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.

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FAQ

Questions learners often ask

What does this 300-410 question test?

NetFlow and Flexible NetFlow — This question tests NetFlow and Flexible NetFlow — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: CoPP is rate-limiting NetFlow export packets because they are classified as management traffic, causing export failures and cache buildup. — Flexible NetFlow can generate a large number of packets for export, especially if the flow monitor is configured to export all flows. These export packets are sent from the router's control plane, and if CoPP is policing management traffic, the export packets might be classified as management traffic and dropped. However, the show output indicates that the flow monitor itself is dropping packets, which suggests that the flow monitor's cache is full or that the export process is overwhelmed. The correct answer is that the flow monitor's cache is too small, causing packets to be dropped before they can be exported, and the CPU spike is due to the export process consuming resources. But the CoPP is also rate-limiting the export packets, causing further drops. The root cause is that CoPP is rate-limiting the NetFlow export traffic, which is classified as management traffic, causing the export to fail and the cache to fill up.

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

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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