hardMultiple ChoiceObjective-mapped
300-410 Practice Question: CoPP is rate-limiting legitimate routing traffic
CoPP is rate-limiting legitimate routing traffic. Router R1 has: class-map match-any ROUTING, match protocol bgp, match protocol ospf, policy-map COPP, class ROUTING, police 10000 conform-action transmit exceed-action drop. BGP sessions flap. What is the root cause?
⚠ Common exam trap
Cisco often tests the misconception that CoPP class-map matching must be exclusive, when in fact the root cause is an overly restrictive police rate that drops essential control-plane packets like BGP keepalives.
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 police rate is too low, causing drops of BGP packets.
B is correct because the police rate of 10,000 bps (10 kbps) is too low for BGP traffic. BGP uses TCP port 179 and can generate bursts of packets during keepalive and update exchanges; if the policer drops BGP packets, the TCP session times out and flaps. The class-map correctly matches both BGP and OSPF, but the rate limit is insufficient for the combined control-plane traffic.
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-map should match only BGP, not OSPF.
Why it's wrong here
Both are routing protocols; the issue is the rate limit.
- ✓
The police rate is too low, causing drops of BGP packets.
Why this is correct
10 kbps is insufficient for BGP keepalives and updates, leading to flaps.
- ✗
CoPP should be applied to the control plane, not the data plane.
Why it's wrong here
CoPP is applied to control plane; the configuration is correct.
- ✗
BGP sessions flap due to MTU mismatch, not CoPP.
Why it's wrong here
MTU issues cause different symptoms; CoPP directly drops packets.
Visual reference
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
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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.