- A
Create an extended ACL that matches TCP port 22 (SSH) and UDP port 161 (SNMP).
Correct. ACLs are used to match the specific control plane traffic (SSH and SNMP) for classification.
- B
Apply the CoPP policy under the interface configuration mode using 'service-policy input'.
Why wrong: Incorrect. CoPP is applied under the control-plane configuration, not under a physical interface.
- C
Configure a class-map that matches the ACL created in step A.
Correct. The class-map uses the ACL to classify SSH and SNMP traffic.
- D
Apply the CoPP policy under the control-plane configuration using 'service-policy output'.
Why wrong: Incorrect. CoPP uses 'service-policy input' because the control plane receives traffic; 'output' is not supported for CoPP.
- E
Use the 'police' command with 'conform-action drop' to drop all SSH and SNMP traffic.
Why wrong: Incorrect. Dropping all SSH and SNMP traffic would block legitimate management access. The engineer should rate-limit or drop only excessive traffic.
CoPP Configuration for SSH and SNMP
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.
An engineer must implement CoPP to protect the control plane of a Cisco IOS router from a DoS attack targeting SSH and SNMP. Which TWO configuration changes are required? (Choose TWO.)
Quick Answer
The answer is to configure a class-map that matches the ACL created to identify SSH and SNMP traffic. This is correct because CoPP (Control Plane Policing) protects the router’s control plane by classifying traffic into classes—here, SSH and SNMP—and applying a police rate to drop excessive or malicious packets. The CoPP configuration steps for SSH and SNMP require first building an ACL to match these protocols, then referencing that ACL in a class-map, and finally applying a policy-map with a police action under the control-plane configuration using the service-policy input command. On the Cisco CCNP ENARSI 300-410 exam, this tests your understanding of control plane protection mechanisms and the correct hierarchical structure of MQC (Modular QoS CLI). A common trap is applying the policy-map to a physical interface or using service-policy output, both of which fail to protect the control plane from inbound DoS attacks. Memory tip: think “ACL, class, policy, control—input only” to recall the four-step sequence and the mandatory direction.
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
Create an extended ACL that matches TCP port 22 (SSH) and UDP port 161 (SNMP).
Option A is correct because CoPP uses an extended ACL to classify traffic for the control plane. SSH uses TCP port 22 and SNMP uses UDP port 161, so an extended ACL matching these protocols and ports is required to identify the DoS attack traffic. This ACL is then referenced by a class-map to define the traffic class for the CoPP policy.
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.
- ✓
Create an extended ACL that matches TCP port 22 (SSH) and UDP port 161 (SNMP).
- ✗
Apply the CoPP policy under the interface configuration mode using 'service-policy input'.
Why it's wrong here
Incorrect. CoPP is applied under the control-plane configuration, not under a physical interface.
- ✓
Configure a class-map that matches the ACL created in step A.
- ✗
Apply the CoPP policy under the control-plane configuration using 'service-policy output'.
Why it's wrong here
Incorrect. CoPP uses 'service-policy input' because the control plane receives traffic; 'output' is not supported for CoPP.
- ✗
Use the 'police' command with 'conform-action drop' to drop all SSH and SNMP traffic.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between applying CoPP under control-plane configuration versus interface configuration, and the correct direction (input vs output) for protecting the control plane from inbound attacks.
Trap categories for this question
Command / output trap
Incorrect. CoPP uses 'service-policy input' because the control plane receives traffic; 'output' is not supported for CoPP.
Detailed technical explanation
How to think about this question
CoPP leverages MQC (Modular QoS CLI) to classify control plane traffic using class-maps that reference ACLs or other match criteria. The policy-map applies actions like 'police' to rate-limit traffic, and the policy is attached under 'control-plane' with 'service-policy input' for inbound traffic. A common real-world scenario is protecting SSH and SNMP from a flood while allowing legitimate management traffic, which requires careful policing rates rather than dropping all traffic.
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
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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Control Plane Policing (CoPP) — study guide chapter
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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: Create an extended ACL that matches TCP port 22 (SSH) and UDP port 161 (SNMP). — Option A is correct because CoPP uses an extended ACL to classify traffic for the control plane. SSH uses TCP port 22 and SNMP uses UDP port 161, so an extended ACL matching these protocols and ports is required to identify the DoS attack traffic. This ACL is then referenced by a class-map to define the traffic class for the CoPP policy.
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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