- A
The CoPP policy has an explicit 'deny' in the class-default, which drops all traffic not matched by other classes.
If class-default has a 'police' or 'drop' action, all unmatched traffic (including SSH) is dropped. The engineer should have added a 'class class-default' with 'police' or 'permit'.
- B
The SSH traffic is being policed to 1 Mbps, but the traffic rate is below that, so it should be allowed.
Why wrong: If the traffic is below the police rate, it should be allowed. The issue is not the police rate but the classification.
- C
The CoPP policy is applied to the control plane of the VRF, not the global control plane, so it does not affect SSH traffic.
Why wrong: CoPP is applied globally to the control plane, not per-VRF. There is no per-VRF CoPP.
- D
The SSH traffic is being matched by a different class that has a 'drop' action, such as a class for ICMP.
Why wrong: This is possible but less likely than the default class issue. The question states the policy includes a class for SSH, so it should match.
Quick Answer
The answer is that the CoPP policy’s class-default has an explicit ‘deny’ action, which drops all traffic not matched by other classes, including SSH from any VRF. This happens because CoPP policies are applied globally to the control plane and classify traffic using the global routing table, regardless of VRF context. When SSH traffic originates from a VRF-Lite instance, the class-map—whether using ‘match protocol’ or ‘match access-group’—evaluates it in the global table, so if the SSH class is not explicitly matched, the traffic falls into class-default and is dropped by the policer. On the Cisco CCNP ENARSI 300-410 exam, this tests your understanding that CoPP interacts with VRF-Lite by ignoring VRF separation during classification, a common trap where engineers assume VRF-aware classification. A key memory tip: “CoPP sees the global table, not the VRF label—if class-default denies, SSH from any VRF is gone.”
300-410 VRF-Lite Practice Question
This 300-410 practice question tests your understanding of vrf-lite. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 network engineer applies a CoPP (Control Plane Policing) policy to a router running VRF-Lite. The policy includes a class that matches SSH traffic and polices it to 1 Mbps. After applying the policy, the engineer cannot SSH into the router from any VRF. Which is the most likely explanation?
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
The CoPP policy has an explicit 'deny' in the class-default, which drops all traffic not matched by other classes.
CoPP policies are applied to the control plane and affect all traffic destined to the router, regardless of VRF. However, CoPP uses the global routing table for classification. If the SSH traffic is sourced from a VRF, the CoPP policy may not match it correctly because the class-map might be using 'match protocol' or 'match access-group' that is evaluated in the global context. Additionally, the default class (class-default) often has a police action that drops traffic if not explicitly allowed. A common edge case is that the engineer forgot to include a 'class-default' action to permit traffic, causing all unmatched traffic to be dropped.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 has an explicit 'deny' in the class-default, which drops all traffic not matched by other classes.
Why this is correct
If class-default has a 'police' or 'drop' action, all unmatched traffic (including SSH) is dropped. The engineer should have added a 'class class-default' with 'police' or 'permit'.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
- ✗
The SSH traffic is being policed to 1 Mbps, but the traffic rate is below that, so it should be allowed.
Why it's wrong here
If the traffic is below the police rate, it should be allowed. The issue is not the police rate but the classification.
- ✗
The CoPP policy is applied to the control plane of the VRF, not the global control plane, so it does not affect SSH traffic.
Why it's wrong here
CoPP is applied globally to the control plane, not per-VRF. There is no per-VRF CoPP.
- ✗
The SSH traffic is being matched by a different class that has a 'drop' action, such as a class for ICMP.
Why it's wrong here
This is possible but less likely than the default class issue. The question states the policy includes a class for SSH, so it should match.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
- Static NAT maps one inside address to one outside address.
- PAT allows many inside hosts to share one public address using ports.
- Inside local and inside global describe the private and translated addresses.
- NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
- Identify inside and outside interfaces first.
- Check whether the scenario needs static NAT, dynamic NAT or PAT.
- Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 300-410 NAT questions on configuration and troubleshooting.
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VRF-Lite — study guide chapter
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VRF-Lite practice questions
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FAQ
Questions learners often ask
What does this 300-410 question test?
VRF-Lite — This question tests VRF-Lite — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The CoPP policy has an explicit 'deny' in the class-default, which drops all traffic not matched by other classes. — CoPP policies are applied to the control plane and affect all traffic destined to the router, regardless of VRF. However, CoPP uses the global routing table for classification. If the SSH traffic is sourced from a VRF, the CoPP policy may not match it correctly because the class-map might be using 'match protocol' or 'match access-group' that is evaluated in the global context. Additionally, the default class (class-default) often has a police action that drops traffic if not explicitly allowed. A common edge case is that the engineer forgot to include a 'class-default' action to permit traffic, causing all unmatched traffic to be dropped.
What should I do if I get this 300-410 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 300-410 NAT questions on configuration and troubleshooting.
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?
Static NAT maps one inside address to one outside address.
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Last reviewed: Jun 18, 2026
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