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Control Plane Policing (CoPP) →hardMultiple ChoiceObjective-mapped

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 network engineer runs the following command on Router R1:

R1# show policy-map control-plane

Control Plane

Service-policy input: CoPP-IN

Class-map: CoPP-SNMP (match-all) 0 packets, 0 bytes 5 minute offered rate 0000 bps, drop rate 0000 bps Match: access-group 130 police: cir 32000 bps, bc 6000 bytes, be 6000 bytes conformed 0 packets, 0 bytes; actions: transmit exceeded 0 packets, 0 bytes; actions: drop violated 0 packets, 0 bytes; actions: drop

R1# show access-lists 130

Extended IP access list 130

10 permit udp any any eq snmp
    
20 permit udp any any eq snmptrap

Based on this output, what is the most likely reason that no packets are matching the CoPP-SNMP class?

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 1hardmultiple choice

Study the full ACL explanation →

A
The access-list does not include the correct SNMP port numbers.
Why wrong: Ports 161 and 162 are correct for SNMP.
B
The SNMP traffic is being sent from the router itself, which is not processed through the input control plane policy.
Traffic originated by the router (e.g., SNMP traps) is not subject to input CoPP.
C
The police rate is too low and is dropping all packets before counting.
Why wrong: The counters show 0 packets, so no packets have been classified.
D
The class-map is using 'match-all' instead of 'match-any'.
Why wrong: With a single match criterion, both are equivalent.

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 SNMP traffic is being sent from the router itself, which is not processed through the input control plane policy.

The access-list 130 matches SNMP traffic (UDP ports 161 and 162). However, SNMP traffic to the router itself typically uses the control plane, but the access-list may not match if the traffic is sourced from the router (e.g., SNMP traps) or if the source/destination IPs are not 'any'. The most common issue is that the access-list does not specify the direction of traffic, but since it is applied to the control plane input, it should match incoming SNMP requests. However, if the router is sending SNMP traps, those are output traffic. The problem could be that the access-list is not matching the actual SNMP traffic because the router's own SNMP agent traffic is not subject to CoPP. But the key clue is that the class is not matching any packets, indicating the access-list may not be correct for the traffic type.

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 access-list does not include the correct SNMP port numbers.
Why it's wrong here
Ports 161 and 162 are correct for SNMP.
✓
The SNMP traffic is being sent from the router itself, which is not processed through the input control plane policy.
Why this is correct
Traffic originated by the router (e.g., SNMP traps) is not subject to input CoPP.
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 police rate is too low and is dropping all packets before counting.
Why it's wrong here
The counters show 0 packets, so no packets have been classified.
✗
The class-map is using 'match-all' instead of 'match-any'.
Why it's wrong here
With a single match criterion, both are equivalent.

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

Command / output trap
The counters show 0 packets, so no packets have been classified.

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 SNMP traffic is being sent from the router itself, which is not processed through the input control plane policy. — The access-list 130 matches SNMP traffic (UDP ports 161 and 162). However, SNMP traffic to the router itself typically uses the control plane, but the access-list may not match if the traffic is sourced from the router (e.g., SNMP traps) or if the source/destination IPs are not 'any'. The most common issue is that the access-list does not specify the direction of traffic, but since it is applied to the control plane input, it should match incoming SNMP requests. However, if the router is sending SNMP traps, those are output traffic. The problem could be that the access-list is not matching the actual SNMP traffic because the router's own SNMP agent traffic is not subject to CoPP. But the key clue is that the class is not matching any packets, indicating the access-list may not be correct for the traffic type.

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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