Question 1,358 of 2,152
Control Plane Policing (CoPP)mediumMultiple ChoiceObjective-mapped

Understanding Burst Values in CoPP police Command

This 300-410 practice question tests your understanding of control plane policing (copp). This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.

Examine this CoPP configuration:

ip access-list extended COPP-ACL
 permit tcp any any eq 22
 permit tcp any any eq

23

permit icmp any any echo

! class-map match-all COPP-CLASS match access-group name COPP-ACL ! policy-map COPP-POLICY

class COPP-CLASS

police 10000 1500 1500 conform-action transmit exceed-action drop violate-action drop

class class-default

police 64000 conform-action transmit exceed-action drop ! control-plane service-policy input COPP-POLICY

What is the effect of the police command in class COPP-CLASS?

Quick Answer

The answer is that traffic matching class COPP-CLASS is limited to 10000 bps with a burst of 1500 bytes, and any excess traffic is dropped. This is correct because the police command in a CoPP policy-map specifies a conform rate of 10000 bits per second, a normal burst of 1500 bytes, and an excess burst of 1500 bytes; when traffic exceeds the burst threshold, the exceed-action drop and violate-action drop parameters ensure all non-conforming packets are discarded. On the Cisco CCNP ENARSI 300-410 exam, this configuration tests your understanding of how Control Plane Policing (CoPP) uses burst values to protect the router’s control plane from DoS attacks while allowing legitimate traffic like SSH, Telnet, and ICMP echo. A common trap is confusing the normal burst with the excess burst—here they are equal, meaning no second token bucket is used, so any traffic beyond the initial 1500-byte burst is immediately dropped. Remember the mnemonic “C-E-V” for conform, exceed, violate—if both exceed and violate actions are set to drop, the burst is a hard limit.

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

Traffic is limited to 10000 bps with a burst of 1500 bytes; excess traffic is dropped.

Option A is correct because the police command in class COPP-CLASS uses a committed information rate (CIR) of 10000 bps, a normal burst (Bc) of 1500 bytes, and an excess burst (Be) of 1500 bytes. The conform-action transmit, exceed-action drop, and violate-action drop ensure that any traffic exceeding the rate and burst limits is dropped, effectively limiting the matched traffic (SSH, Telnet, ICMP echo) to 10000 bps with a burst of 1500 bytes.

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.

  • Traffic is limited to 10000 bps with a burst of 1500 bytes; excess traffic is dropped.

    Why this is correct

    Correct. The police command specifies conform rate 10000 bps, normal burst 1500, excess burst 1500. Exceed and violate actions are both drop.

    Related concept

    Read the scenario before looking for a memorised answer.

  • Traffic is limited to 10000 bps with a burst of 3000 bytes; excess traffic is dropped.

    Why it's wrong here

    Incorrect. The excess burst is 1500 bytes, not 3000. The normal burst and excess burst are separate parameters.

  • The police command is invalid because it uses three parameters after the rate.

    Why it's wrong here

    Incorrect. The police command can include conform rate, normal burst, and excess burst. The syntax is valid.

  • Traffic is limited to 10000 bps, but the burst values are ignored because they are not configured in bytes.

    Why it's wrong here

    Incorrect. The burst values are in bytes and are used by the token bucket algorithm.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Cisco often tests the distinction between the normal burst (Bc) and excess burst (Be) parameters, where candidates mistakenly sum them or assume the second parameter is a time interval, leading to incorrect burst size calculations.

Trap categories for this question

  • Command / output trap

    Incorrect. The police command can include conform rate, normal burst, and excess burst. The syntax is valid.

Detailed technical explanation

How to think about this question

In Cisco IOS, the police command uses a token bucket algorithm where the CIR replenishes tokens at the configured rate, and the normal burst (Bc) defines the token bucket depth for conforming traffic, while the excess burst (Be) allows a larger bucket for peak bursts. When both exceed-action and violate-action are set to drop, traffic exceeding the Bc bucket is dropped immediately, and the Be bucket is effectively unused because violate-action also drops; this creates a strict policer. In CoPP, this is critical for protecting the control plane from DoS attacks on management protocols like SSH (TCP/22) and Telnet (TCP/23), as well as ICMP echo floods.

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 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.

Visual reference

Source Router + ACL permit 10.0.0.0/8 deny any Server 10.0.0.5 ✓ 192.168.1.1 ✗ dropped ACLs evaluate top-down; first match wins — implicit deny all at end

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: Traffic is limited to 10000 bps with a burst of 1500 bytes; excess traffic is dropped. — Option A is correct because the police command in class COPP-CLASS uses a committed information rate (CIR) of 10000 bps, a normal burst (Bc) of 1500 bytes, and an excess burst (Be) of 1500 bytes. The conform-action transmit, exceed-action drop, and violate-action drop ensure that any traffic exceeding the rate and burst limits is dropped, effectively limiting the matched traffic (SSH, Telnet, ICMP echo) to 10000 bps with a burst of 1500 bytes.

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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