- A
Create a class-map that matches routing protocol packets (e.g., OSPF, EIGRP, BGP) and assign a police rate with conform-action transmit and exceed-action drop.
Why wrong: Incorrect. Using exceed-action drop will drop legitimate routing packets during spikes, which can cause routing instability.
- B
Create a class-map that matches routing protocol packets and assign a police rate with conform-action transmit and violate-action transmit.
Correct. Using transmit for both conform and violate actions ensures routing protocol packets are never dropped, even during spikes.
- C
Place routing protocol traffic into a class with a 'drop' action to prevent it from overwhelming the control plane.
Why wrong: Incorrect. Dropping routing protocol traffic would cause loss of routing adjacencies and network instability.
- D
Use the 'police' command with a high committed information rate (CIR) and burst size, and apply 'conform-action transmit' and 'exceed-action set-dscp cs6'.
Correct. Setting a high CIR and using set-dscp (instead of drop) for exceeding traffic ensures that routing packets are re-marked but not dropped, preserving protocol stability.
- E
Apply the CoPP policy only to the 'control-plane host' subinterface, which processes all routing protocol packets.
Why wrong: Incorrect. The 'control-plane host' subinterface handles packets destined to the router itself, including routing protocols, but applying CoPP only there does not prevent drops; the policy actions still apply.
Protecting Routing Protocols in CoPP Policies
This 300-410 practice question tests your understanding of control plane policing (copp). This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which TWO actions will prevent a CoPP policy from inadvertently dropping legitimate routing protocol packets during a traffic spike? (Choose TWO.)
Quick Answer
The answer is to use the 'police' command with a high committed information rate (CIR) and burst size, applying 'conform-action transmit' and 'exceed-action set-dscp cs6' rather than a drop action. This is correct because CoPP must protect routing protocols from being dropped during a traffic spike by ensuring that legitimate protocol packets are never subjected to a 'drop' action in any exceed or violate threshold; instead, marking them with DSCP CS6 preserves their priority without discarding them. On the Cisco CCNP ENARSI 300-410 exam, this question tests your understanding that CoPP policies should classify routing protocol traffic into a high-priority class with a guaranteed transmit action, and a common trap is choosing 'exceed-action drop' which would inadvertently discard critical routing updates. A useful memory tip is "never drop a route—mark it high instead," reinforcing that routing protocol packets should always be transmitted, even if they exceed the police rate.
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
Create a class-map that matches routing protocol packets and assign a police rate with conform-action transmit and violate-action transmit.
Option B is correct because using 'conform-action transmit' and 'violate-action transmit' ensures that routing protocol packets are never dropped, even if they exceed the configured police rate. This prevents CoPP from inadvertently dropping critical control plane traffic during a traffic spike, as the violate-action overrides the default drop behavior. The other correct option, D, uses a high CIR and burst size with 'exceed-action set-dscp cs6' to mark but not drop routing protocol packets, preserving them while still applying QoS treatment.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Create a class-map that matches routing protocol packets (e.g., OSPF, EIGRP, BGP) and assign a police rate with conform-action transmit and exceed-action drop.
Why it's wrong here
Incorrect. Using exceed-action drop will drop legitimate routing packets during spikes, which can cause routing instability.
- ✓
Create a class-map that matches routing protocol packets and assign a police rate with conform-action transmit and violate-action transmit.
Why this is correct
Correct. Using transmit for both conform and violate actions ensures routing protocol packets are never dropped, even during spikes.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Place routing protocol traffic into a class with a 'drop' action to prevent it from overwhelming the control plane.
Why it's wrong here
Incorrect. Dropping routing protocol traffic would cause loss of routing adjacencies and network instability.
- ✓
Use the 'police' command with a high committed information rate (CIR) and burst size, and apply 'conform-action transmit' and 'exceed-action set-dscp cs6'.
Why this is correct
Correct. Setting a high CIR and using set-dscp (instead of drop) for exceeding traffic ensures that routing packets are re-marked but not dropped, preserving protocol stability.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Apply the CoPP policy only to the 'control-plane host' subinterface, which processes all routing protocol packets.
Why it's wrong here
Incorrect. The 'control-plane host' subinterface handles packets destined to the router itself, including routing protocols, but applying CoPP only there does not prevent drops; the policy actions still apply.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that any policing action (like exceed-action drop) is acceptable for routing protocol traffic, but the trap is that candidates forget that routing protocol packets must never be dropped, so only actions that guarantee transmission (like violate-action transmit or marking without drop) are correct.
Detailed technical explanation
How to think about this question
Under the hood, CoPP uses MQC (Modular QoS CLI) to apply a police rate to control plane traffic. The 'violate-action transmit' option is a non-standard but valid configuration that overrides the default three-color policer behavior (conform, exceed, violate) to ensure no packets are dropped. In real-world scenarios, routing protocol packets like OSPF hellos (sent every 10 seconds) or BGP keepalives (sent every 60 seconds) are low-bandwidth but critical; a traffic spike from a misconfigured device or DoS attack could otherwise cause these packets to exceed the police rate and be dropped, leading to neighbor flapping.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
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.
What to study next
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FAQ
Questions learners often ask
What does this 300-410 question test?
Control Plane Policing (CoPP) — This question tests Control Plane Policing (CoPP) — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create a class-map that matches routing protocol packets and assign a police rate with conform-action transmit and violate-action transmit. — Option B is correct because using 'conform-action transmit' and 'violate-action transmit' ensures that routing protocol packets are never dropped, even if they exceed the configured police rate. This prevents CoPP from inadvertently dropping critical control plane traffic during a traffic spike, as the violate-action overrides the default drop behavior. The other correct option, D, uses a high CIR and burst size with 'exceed-action set-dscp cs6' to mark but not drop routing protocol packets, preserving them while still applying QoS treatment.
What should I do if I get this 300-410 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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