hardMultiple ChoiceObjective-mapped
300-410 Practice Question: An engineer configures Control Plane Policing…
An engineer configures Control Plane Policing (CoPP) with a policy that denies all traffic in class-default. After applying the policy, BGP sessions to the router fail. What is the most likely explanation?
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 has an explicit 'drop' action, which overrides the implicit permit and drops all unmatched traffic, including BGP packets.
CoPP class-default has an implicit permit at the end, but if an explicit deny is configured in class-default, it will drop all traffic not matched by other classes, including BGP control packets. The explicit deny overrides the implicit permit.
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 has an explicit 'drop' action, which overrides the implicit permit and drops all unmatched traffic, including BGP packets.
Why this is correct
Explicit deny in class-default changes the default behavior from permit to drop.
- ✗
The CoPP policy was applied to the wrong interface, so BGP packets are dropped by the interface ACL.
Why it's wrong here
CoPP is applied to the control plane, not interfaces.
- ✗
The BGP packets are matched by another class with a 'drop' action, but the class-default is irrelevant.
Why it's wrong here
If another class drops BGP, that would be the cause, but the question specifies class-default deny.
- ✗
The CoPP policy uses 'rate-limit' in bps instead of pps, causing BGP packets to be dropped due to rate limiting.
Why it's wrong here
Rate limiting would cause drops only if exceeded, not a complete failure.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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