Question 629 of 2,152

Control Plane Policing (CoPP) →mediumMultiple ChoiceObjective-mapped

Quick Answer

The answer is that the CoPP policy has a separate class for Telnet with a lower police rate or a drop action. Both Telnet and SSH use TCP, so a single class matching all TCP traffic at 5000 bps would police both equally; the fact that Telnet sessions time out while SSH succeeds indicates that Telnet is being matched by a different, more restrictive class within the policy. This scenario tests your understanding of how CoPP class-maps and policy-maps interact with control plane traffic—a common trap on the Cisco CCNP ENARSI 300-410 exam is assuming a broad TCP match applies uniformly, when in reality separate classes for Telnet and SSH can have distinct police rates or actions. Remember the memory tip: “TCP is the same, but class is the game”—if one protocol fails and another succeeds under CoPP, look for a separate class targeting the failing protocol.

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 router has a CoPP policy that includes a class-map matching all TCP traffic with a police rate of 5000 bps. The engineer notices that Telnet sessions to the router are timing out, but SSH sessions work fine. The router is configured to accept both Telnet and SSH. 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.

Question 1mediummultiple choice

Study the full ACL explanation →

A
The CoPP policy has a separate class for Telnet with a lower police rate or a drop action.
If Telnet is in a different class with a lower rate or drop, it would explain why Telnet fails while SSH works.
B
The SSH traffic is encrypted, so it uses less bandwidth than Telnet.
Why wrong: SSH encryption adds overhead, so SSH actually uses slightly more bandwidth than Telnet.
C
The Telnet server on the router is not responding due to a configuration error.
Why wrong: The scenario states both are configured, and the issue is related to CoPP.
D
The CoPP policy is rate-limiting TCP traffic to 5000 bps, which is enough for SSH but not for Telnet.
Why wrong: Both use TCP, and 5000 bps should be sufficient for interactive sessions; the difference is likely due to separate classes.

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 has a separate class for Telnet with a lower police rate or a drop action.

Both Telnet and SSH use TCP, so they should both be affected by the same police rate. However, if the CoPP policy has separate classes for Telnet and SSH, or if the police rate is applied per class, the issue might be that Telnet traffic is being policed more aggressively. Alternatively, the Telnet traffic might be hitting a different class that drops it.

Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.

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 separate class for Telnet with a lower police rate or a drop action.
Why this is correct
If Telnet is in a different class with a lower rate or drop, it would explain why Telnet fails while SSH works.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
The SSH traffic is encrypted, so it uses less bandwidth than Telnet.
Why it's wrong here
SSH encryption adds overhead, so SSH actually uses slightly more bandwidth than Telnet.
✗
The Telnet server on the router is not responding due to a configuration error.
Why it's wrong here
The scenario states both are configured, and the issue is related to CoPP.
✗
The CoPP policy is rate-limiting TCP traffic to 5000 bps, which is enough for SSH but not for Telnet.
Why it's wrong here
Both use TCP, and 5000 bps should be sufficient for interactive sessions; the difference is likely due to separate classes.

Common exam traps

Common exam trap: NAT rules depend on direction and matching traffic

NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.

Trap categories for this question

Scenario analysis trap
The scenario states both are configured, and the issue is related to CoPP.

Detailed technical explanation

How to think about this question

NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.

KKey Concepts to Remember

Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.

TExam Day Tips

Identify inside and outside interfaces first.
Check whether the scenario needs static NAT, dynamic NAT or PAT.
Do not confuse NAT matching ACLs with normal packet-filtering intent.

Key takeaway

NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.

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.

Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 300-410 NAT questions on configuration and troubleshooting.

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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) — Static NAT maps one inside address to one outside address..

What is the correct answer to this question?

The correct answer is: The CoPP policy has a separate class for Telnet with a lower police rate or a drop action. — Both Telnet and SSH use TCP, so they should both be affected by the same police rate. However, if the CoPP policy has separate classes for Telnet and SSH, or if the police rate is applied per class, the issue might be that Telnet traffic is being policed more aggressively. Alternatively, the Telnet traffic might be hitting a different class that drops it.

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

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?

Static NAT maps one inside address to one outside address.

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