- A
The class-default is set to 'drop', and OSPF packets fall into class-default because they are not matched by any other class.
CoPP processes packets in order. If OSPF is not matched by a higher class, it goes to class-default. If class-default drops, OSPF packets are dropped, causing neighbor loss.
- B
The CoPP policy uses 'police' in bps, but OSPF packets are small and exceed the rate limit.
Why wrong: OSPF hello packets are small and unlikely to exceed a bps rate limit. The issue is more likely that they are dropped entirely.
- C
The CoPP policy is applied to the input direction, but OSPF packets are processed in the output direction.
Why wrong: CoPP can be applied to both input and output. OSPF packets are received, so input direction is correct.
- D
The CoPP policy uses 'police' in pps, but OSPF hello packets are sent every 10 seconds, so they are not rate-limited.
Why wrong: If the rate limit is too low, even occasional packets could be dropped, but the default class drop is more likely the cause.
Quick Answer
The answer is that the class-default is set to 'drop', causing OSPF packets to be discarded because they are not matched by any other class. When Control Plane Policing (CoPP) is configured, traffic is classified into user-defined classes based on match criteria; any traffic not explicitly matched falls into the default class (class-default). If the policy-map sets class-default to 'drop', all unmatched traffic—including OSPF hello packets using IP protocol 89—is dropped, which disrupts neighbor adjacency and brings OSPF neighbors down. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of CoPP classification behavior and the critical role of the default class, often appearing as a trap where engineers forget to permit essential control plane protocols. A common memory tip is "default drops the rest"—if you don't explicitly match OSPF, it hits class-default, so always verify the default action in your policy-map.
300-410 Device Access Control Practice Question
This 300-410 practice question tests your understanding of device access control. 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 configures Control Plane Policing (CoPP) on a router. After applying the policy, OSPF neighbors go down. The engineer checks the policy and sees that OSPF packets are not explicitly matched. Which is the most likely explanation?
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.
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 class-default is set to 'drop', and OSPF packets fall into class-default because they are not matched by any other class.
When Control Plane Policing (CoPP) is configured, traffic is classified into classes based on match criteria. If OSPF packets are not explicitly matched by any configured class, they fall into the default class (class-default). If the policy-map sets class-default to 'drop', all unmatched traffic, including OSPF hello packets (which use IP protocol 89), will be dropped. This causes OSPF neighbors to go down because the router stops receiving or sending OSPF control packets.
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 class-default is set to 'drop', and OSPF packets fall into class-default because they are not matched by any other class.
Why this is correct
CoPP processes packets in order. If OSPF is not matched by a higher class, it goes to class-default. If class-default drops, OSPF packets are dropped, causing neighbor loss.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The CoPP policy uses 'police' in bps, but OSPF packets are small and exceed the rate limit.
Why it's wrong here
OSPF hello packets are small and unlikely to exceed a bps rate limit. The issue is more likely that they are dropped entirely.
- ✗
The CoPP policy is applied to the input direction, but OSPF packets are processed in the output direction.
Why it's wrong here
CoPP can be applied to both input and output. OSPF packets are received, so input direction is correct.
- ✗
The CoPP policy uses 'police' in pps, but OSPF hello packets are sent every 10 seconds, so they are not rate-limited.
Why it's wrong here
If the rate limit is too low, even occasional packets could be dropped, but the default class drop is more likely the cause.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the concept that class-default in CoPP can be set to 'drop', and candidates may overlook that OSPF or other routing protocols are not explicitly matched, leading to neighbor loss.
Trap categories for this question
Command / output trap
CoPP can be applied to both input and output. OSPF packets are received, so input direction is correct.
Detailed technical explanation
How to think about this question
CoPP uses Modular QoS CLI (MQC) to classify and police traffic destined to the route processor. The class-default class is implicitly present in every policy-map and, by default, has a 'transmit' action. However, if the engineer explicitly configures 'drop' for class-default, all traffic not matching higher classes is discarded. OSPF uses IP protocol 89 and multicast addresses 224.0.0.5/6; without an explicit class matching these, OSPF packets are treated as default traffic. This is a common misconfiguration when engineers intend to protect the control plane but inadvertently block essential routing protocols.
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 network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
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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FAQ
Questions learners often ask
What does this 300-410 question test?
Device Access Control — This question tests Device Access Control — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The class-default is set to 'drop', and OSPF packets fall into class-default because they are not matched by any other class. — When Control Plane Policing (CoPP) is configured, traffic is classified into classes based on match criteria. If OSPF packets are not explicitly matched by any configured class, they fall into the default class (class-default). If the policy-map sets class-default to 'drop', all unmatched traffic, including OSPF hello packets (which use IP protocol 89), will be dropped. This causes OSPF neighbors to go down because the router stops receiving or sending OSPF control packets.
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.
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?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This 300-410 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 300-410 exam.
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