- A
The class-default is configured with a police action that drops OSPF packets exceeding the rate.
If OSPF packets are not explicitly classified and permitted, they fall into class-default. The police action in class-default will drop packets that exceed the configured rate, causing OSPF hello packets to be dropped and neighbors to flap.
- B
The CoPP policy is applied to the wrong direction (input vs output).
Why wrong: Applying CoPP in the wrong direction would not affect OSPF packets because OSPF uses multicast and is processed by the control plane.
- C
The access-list used to classify OSPF packets is missing the 'permit' statement for OSPF protocol.
Why wrong: If the access-list is missing the permit, OSPF packets would fall into class-default, which is the same issue, but the more direct explanation is the class-default behavior.
- D
The CoPP policy uses 'drop' action for OSPF class.
Why wrong: If the engineer explicitly configured a drop action for OSPF, that would be intentional, not a misconfiguration.
300-410 Route Summarization Practice Question
This 300-410 practice question tests your understanding of route summarization. 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 configuration, OSPF neighbors are flapping. 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 configured with a police action that drops OSPF packets exceeding the rate.
CoPP applies a policy-map to the control plane. If the default class-default is used without an explicit permit for OSPF packets, the implicit deny at the end of the policy-map will drop OSPF packets. The default class-default action is 'drop' if not explicitly configured, but even if a 'police' action is configured, the default behavior is to drop packets that exceed the rate.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
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 configured with a police action that drops OSPF packets exceeding the rate.
Why this is correct
If OSPF packets are not explicitly classified and permitted, they fall into class-default. The police action in class-default will drop packets that exceed the configured rate, causing OSPF hello packets to be dropped and neighbors to flap.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
OSPF neighbours must agree on key parameters.
- ✗
The CoPP policy is applied to the wrong direction (input vs output).
Why it's wrong here
Applying CoPP in the wrong direction would not affect OSPF packets because OSPF uses multicast and is processed by the control plane.
- ✗
The access-list used to classify OSPF packets is missing the 'permit' statement for OSPF protocol.
Why it's wrong here
If the access-list is missing the permit, OSPF packets would fall into class-default, which is the same issue, but the more direct explanation is the class-default behavior.
- ✗
The CoPP policy uses 'drop' action for OSPF class.
Why it's wrong here
If the engineer explicitly configured a drop action for OSPF, that would be intentional, not a misconfiguration.
Common exam traps
Common exam trap: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Detailed technical explanation
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
- OSPF neighbours must agree on key parameters.
- Router ID selection can affect neighbour relationships and LSDB output.
- OSPF cost influences the preferred path.
- A route can appear in OSPF information but not become the installed route.
TExam Day Tips
- Check area mismatch first when OSPF adjacency fails.
- Review passive interfaces when a network is advertised but no neighbour forms.
- Use show ip ospf neighbor and show ip route clues carefully.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
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.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
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FAQ
Questions learners often ask
What does this 300-410 question test?
Route Summarization — This question tests Route Summarization — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: The class-default is configured with a police action that drops OSPF packets exceeding the rate. — CoPP applies a policy-map to the control plane. If the default class-default is used without an explicit permit for OSPF packets, the implicit deny at the end of the policy-map will drop OSPF packets. The default class-default action is 'drop' if not explicitly configured, but even if a 'police' action is configured, the default behavior is to drop packets that exceed the rate.
What should I do if I get this 300-410 question wrong?
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
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?
OSPF neighbours must agree on key parameters.
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Last reviewed: Jun 18, 2026
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