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300-410 Practice Question: A router running EIGRP has a CoPP policy that…
A router running EIGRP has a CoPP policy that includes a class-map matching EIGRP packets with a police rate of 2000 bps. The network engineer notices that EIGRP neighbor adjacencies are flapping. The EIGRP network has 100 routes. The engineer checks the CoPP statistics and sees that the EIGRP class has dropped 500 packets in the last hour. What is the most likely root cause?
⚠ Common exam trap
Cisco often tests the misconception that CoPP drops are always due to misconfiguration or authentication overhead, when in fact the police rate is simply too low for the protocol's normal operation, especially with a moderate number of routes.
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 CoPP police rate of 2000 bps is insufficient for EIGRP hello and update traffic, causing packet drops.
The CoPP police rate of 2000 bps is too low for EIGRP traffic. EIGRP hello packets are sent every 5 seconds (default) and are typically around 60-80 bytes each, plus periodic updates and queries. With 100 routes, the initial exchange and any topology changes generate significant update traffic. Dropping 500 packets in an hour confirms the rate is insufficient, causing hello loss and neighbor flapping.
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 EIGRP hello interval is set too low, causing excessive hello packets that exceed the police rate.
Why it's wrong here
The hello interval default is 5 seconds; even if set lower, the police rate should be adjusted accordingly, but the root cause is the police rate being too low.
- ✓
The CoPP police rate of 2000 bps is insufficient for EIGRP hello and update traffic, causing packet drops.
Why this is correct
EIGRP packets, though small, can be dropped if the police rate is too low, leading to adjacency flapping.
- ✗
The EIGRP authentication is causing larger packets that exceed the police rate.
Why it's wrong here
EIGRP authentication adds a small overhead but not enough to cause significant drops with 2000 bps.
- ✗
The CoPP class-map is matching EIGRP packets incorrectly, causing them to be dropped by a default class.
Why it's wrong here
The statistics show drops in the EIGRP class, so the class is matching correctly.
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.