- A
The CoPP policy is applied to the wrong interface
Why wrong: CoPP is applied to the control plane, not an interface, so incorrect application is unlikely.
- B
The CoPP policy rate-limits all traffic including OSPF below its needed rate
Why wrong: Rate-limiting would still allow some packets; complete dropping of OSPF indicates a drop action, not rate-limit exceed.
- C
OSPF packets match the default class which has a drop action
If the default class action is drop, any traffic not explicitly matched (including OSPF) will be dropped. This is a common misconfiguration.
- D
The class-map matches multiple protocols including OSPF
Why wrong: If the class-map explicitly matches ICMP via protocol or ACL, it should not match OSPF. However, a poorly designed ACL could cause this.
Quick Answer
The answer is that OSPF packets match the default class which has a drop action. This occurs because the CoPP policy explicitly drops ICMP traffic via a class-map, but OSPF hello packets use IP protocol 89, which does not match that ICMP class. Any traffic not matching a user-defined class falls into the implicit default class; if that default class is configured with a drop action, all unmatched control-plane traffic—including OSPF—is discarded. On the Cisco DCCOR and CCNP Data Center Core 350-601 exam, this scenario tests your understanding of CoPP class-matching hierarchy and the critical role of the default class. A common trap is assuming that only the explicitly matched traffic (ICMP) is affected, forgetting that the default class governs everything else. To avoid this, remember the memory tip: “If the default drops, everything stops.” Always verify that your CoPP policy includes an explicit permit for essential routing protocols like OSPF (protocol 89) before applying a drop action to the default class.
350-601 Security Practice Question
This 350-601 practice question tests your understanding of security. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
A Nexus switch experiences high CPU utilization due to excessive ICMP traffic. An engineer applies a CoPP policy that includes a class matching ICMP with a drop action. After applying, legitimate OSPF hello packets are also being dropped. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
OSPF packets match the default class which has a drop action
Option C is correct because when a CoPP policy is applied, traffic that does not match any explicit class-map falls into the default class. If the default class has a drop action, all unmatched traffic—including OSPF hello packets (which use IP protocol 89)—will be dropped. The class-map matching ICMP (typically based on protocol or DSCP) does not match OSPF, so OSPF packets are handled by the default class, causing the observed behavior.
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.
- ✗
The CoPP policy is applied to the wrong interface
Why it's wrong here
CoPP is applied to the control plane, not an interface, so incorrect application is unlikely.
- ✗
The CoPP policy rate-limits all traffic including OSPF below its needed rate
Why it's wrong here
Rate-limiting would still allow some packets; complete dropping of OSPF indicates a drop action, not rate-limit exceed.
- ✓
OSPF packets match the default class which has a drop action
Why this is correct
If the default class action is drop, any traffic not explicitly matched (including OSPF) will be dropped. This is a common misconfiguration.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The class-map matches multiple protocols including OSPF
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the concept that the default class in CoPP is not automatically 'permit' and must be explicitly configured; the trap here is assuming that only the matched class (ICMP) is affected, while forgetting that unmatched traffic falls to the default class, which can have a drop action.
Detailed technical explanation
How to think about this question
CoPP uses a default class (class-default) that implicitly matches all traffic not matched by explicit class-maps. If the default class is configured with a 'drop' action (e.g., 'police cir 0 bps conform-action drop'), any control-plane traffic not explicitly permitted—such as OSPF, BGP, or ARP—will be dropped. In real-world scenarios, engineers often forget to include a 'permit' class for critical routing protocols, leading to outages; best practice is to explicitly match and permit OSPF (protocol 89) and other essential protocols before applying a restrictive default.
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.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this 350-601 question test?
Security — This question tests Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: OSPF packets match the default class which has a drop action — Option C is correct because when a CoPP policy is applied, traffic that does not match any explicit class-map falls into the default class. If the default class has a drop action, all unmatched traffic—including OSPF hello packets (which use IP protocol 89)—will be dropped. The class-map matching ICMP (typically based on protocol or DSCP) does not match OSPF, so OSPF packets are handled by the default class, causing the observed behavior.
What should I do if I get this 350-601 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
2 more ways this is tested on 350-601
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which control plane protection mechanism should be configured to limit the rate of BGP updates destined to the CPU of a Nexus 9000 switch to prevent CPU overload?
easy- A.VLAN Access Control Lists (VACLs)
- ✓ B.Control Plane Policing (CoPP)
- C.EtherChannel load balancing
- D.Switched Port Analyzer (SPAN)
Why B: Control Plane Policing (CoPP) is the correct mechanism because it directly filters and rate-limits control plane traffic, such as BGP updates, before it reaches the CPU of a Nexus 9000 switch. By applying a CoPP policy, you can protect the CPU from being overwhelmed by excessive BGP updates, ensuring stability and preventing denial-of-service conditions.
Variation 2. Which THREE of the following are valid methods to secure the control plane on a Cisco Nexus 9000 switch?
hard- ✓ A.Enable control plane policing (CoPP) to rate-limit control plane traffic.
- ✓ B.Configure management access lists to restrict SSH/SNMP access.
- ✓ C.Disable unused services such as HTTP/HTTPS server.
- D.Enable Bidirectional Forwarding Detection (BFD) on all interfaces.
- E.Implement routing protocol authentication (e.g., OSPF MD5).
Why A: Control plane policing (CoPP) is a valid method to secure the control plane on a Cisco Nexus 9000 switch. CoPP uses a policy map applied to the control plane to rate-limit or drop traffic destined to the supervisor module, protecting the CPU from excessive or malicious traffic. This is a direct control plane security mechanism defined in Cisco NX-OS.
Last reviewed: Jun 24, 2026
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