hardMultiple Choice
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
Keepalives are only a few packets per session, well under 500 pps, so they would not be dropped; the sessions staying up confirms this. It is tempting because CoPP policing can reset sessions when keepalives are lost, but here the missing prefixes point to dropped UPDATE messages instead.
- ✓
CoPP drops BGP update packets from specific clients due to rate limiting, so those prefixes are not learned.
Why this is correct
CoPP polices control-plane traffic to 500 pps, so excess BGP update packets are dropped rather than the session failing. TCP retransmits keep sessions up, but dropped updates mean some prefixes never reach the route reflector's table.
- ✗
The route reflector is configured to ignore certain prefixes.
Why it's wrong here
CoPP policing BGP to 500 pps drops control-plane packets, causing missing prefixes while sessions stay up via keepalives. Prefix filtering would be configured explicitly, making this tempting, but the symptom matches rate-limiting of BGP updates rather than an ignore policy.
- ✗
CoPP only affects eBGP, not iBGP.
Why it's wrong here
CoPP polices all BGP packets arriving at the control plane, including iBGP, so the claim that it spares iBGP is false. It is tempting because CoPP class-maps often target eBGP peering traffic on edge interfaces, yet the policer here matches BGP generally and drops iBGP updates once 500 pps is exceeded.
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.
About these practice questions
Courseiva writes every 300-410 question from scratch — 1,401 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.