hardMultiple ChoiceObjective-mapped
300-410 Practice Question: An engineer configures CoPP on a router that is a…
An engineer configures CoPP on a router that is a route reflector for iBGP. The policy includes a class-map matching BGP traffic and polices it to 500 pps. After deployment, some iBGP prefixes are missing from the route reflector's table, but the BGP sessions are up. Which is the most likely explanation?
⚠ Common exam trap
Cisco often tests the misconception that CoPP drops only keepalives or that session state is the sole indicator of BGP health, but the trap here is that BGP sessions can remain up while updates are dropped, leading to missing prefixes without session flaps.
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
✓
CoPP drops BGP update packets from specific clients due to rate limiting, so those prefixes are not learned.
B is correct because CoPP polices BGP traffic to 500 pps, and if BGP update packets from specific iBGP clients exceed this rate, they are dropped. Since BGP keepalives are small and infrequent, the session remains up, but the dropped updates prevent the route reflector from learning certain prefixes, leading to missing routes in the table.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
CoPP drops BGP keepalive packets, causing the session to reset.
Why it's wrong here
Sessions are up, so keepalives are not dropped.
- ✓
CoPP drops BGP update packets from specific clients due to rate limiting, so those prefixes are not learned.
Why this is correct
Update packets are larger and more frequent; they may exceed the police rate.
- ✗
The route reflector is configured to ignore certain prefixes.
Why it's wrong here
No such configuration is mentioned.
- ✗
CoPP only affects eBGP, not iBGP.
Why it's wrong here
CoPP matches on TCP port 179, which includes both eBGP and iBGP.
Go deeper
Related to this question
Learn chapter
OSPF Route Summarization and Filtering
Key term
BGP Route Reflector
A BGP Route Reflector is a networking device that reduces the number of BGP peer connections needed in a large network by allowing routers to share routing information without needing to connect to every other router directly.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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