Question 1,367 of 2,152

SPAN, RSPAN, and ERSPAN →hardMultiple ChoiceObjective-mapped

ERSPAN CoPP Dropping Locally Generated Packets

This 300-410 practice question tests your understanding of span, rspan, and erspan. 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.

Router R1 is configured as an ERSPAN source to monitor traffic on interface Serial0/0/0. The destination is a collector at 172.16.1.100. R1's configuration: monitor session 1 type erspan-source source interface Serial0/0/0 both destination erspan-id 1 ip address 172.16.1.100 origin ip address 10.0.0.1. The collector is reachable via a default route. The network also uses CoPP (Control Plane Policing) with a policy that polices all incoming traffic to the control plane. The collector receives no packets. What is the most likely issue?

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.

A
The ERSPAN destination IP is not in the routing table, so packets are dropped.
Why wrong: The collector is reachable via default route.
B
CoPP is policing the locally generated ERSPAN packets, causing them to be dropped.
ERSPAN packets are locally generated and may be subject to CoPP if the policy applies to control plane input.
C
The ERSPAN session is not configured with 'no shutdown'.
Why wrong: The configuration shows no 'shutdown' command, so it is enabled by default.
D
The source interface Serial0/0/0 is down, so no traffic is mirrored.
Why wrong: The symptom is that the collector receives no packets, but the interface may be up; the scenario does not indicate it is down.

Full breakdown with real-world context →

Quick Answer

The answer is that CoPP is dropping the locally generated ERSPAN packets because the router treats these mirrored packets as control plane traffic. When R1 generates ERSPAN-encapsulated copies of monitored traffic, those packets are sourced from the router itself and must be processed by the control plane for routing and encapsulation before being sent out. If the CoPP policy applies to all incoming control plane traffic and does not include an exception for locally originated ERSPAN packets, the rate-limiter will police and drop them before they ever leave the router. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding that ERSPAN packets are not transit traffic—they are locally generated, so CoPP can inadvertently block them even when the destination is reachable. A common trap is assuming CoPP only affects traffic destined to the router’s IP, but ERSPAN packets hit the control plane during generation. Memory tip: “Locally generated, control plane regulated—if CoPP is applied, ERSPAN gets policed.”

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

✓

CoPP is policing the locally generated ERSPAN packets, causing them to be dropped.

ERSPAN mirrored packets are process-switched by the router's control plane, meaning the route processor handles encapsulation and forwarding. In Cisco IOS, Control Plane Policing (CoPP) applied to the control plane input can affect locally generated traffic if the traffic matches a CoPP class. The CoPP policy in this scenario polices all incoming traffic to the control plane, and even though ERSPAN packets are generated locally (not incoming), the act of generating them involves the control plane, and the policy may classify them as control plane traffic. This can cause the ERSPAN packets to be dropped. This is a known pitfall where CoPP inadvertently impacts ERSPAN traffic.

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 ERSPAN destination IP is not in the routing table, so packets are dropped.
Why it's wrong here
The collector is reachable via default route.
✓
CoPP is policing the locally generated ERSPAN packets, causing them to be dropped.
Why this is correct
ERSPAN packets are locally generated and may be subject to CoPP if the policy applies to control plane input.
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 ERSPAN session is not configured with 'no shutdown'.
Why it's wrong here
The configuration shows no 'shutdown' command, so it is enabled by default.
✗
The source interface Serial0/0/0 is down, so no traffic is mirrored.
Why it's wrong here
The symptom is that the collector receives no packets, but the interface may be up; the scenario does not indicate it is down.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.

Trap categories for this question

Command / output trap
The configuration shows no 'shutdown' command, so it is enabled by default.
Scenario analysis trap
The symptom is that the collector receives no packets, but the interface may be up; the scenario does not indicate it is down.

Detailed technical explanation

How to think about this question

This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.

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.
Use explanations to understand the rule behind the answer.

TExam Day Tips

Underline the problem statement mentally.
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 practitioner preparing for the 300-410 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.

Quick reference

IPv4 Address Class Summary

Class	First Octet Range	Default Mask	Networks	Hosts per Network
A	1–126	/8 (255.0.0.0)	126	16,777,214
B	128–191	/16 (255.255.0.0)	16,384	65,534
C	192–223	/24 (255.255.255.0)	2,097,152	254
D	224–239	N/A	Multicast groups	—
E	240–255	N/A	Reserved / experimental	—

127.x.x.x is reserved for loopback. Modern networks use CIDR (classless) rather than classful addressing.

What to study next

Got this wrong? Here's your next step.

Identify which 300-410 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.

Related 300-410 practice-question pages

Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.

Layer 3 Technologies practice questions

Practise 300-410 questions linked to Layer 3 Technologies.

EIGRP Troubleshooting practice questions

Practise 300-410 questions linked to EIGRP Troubleshooting.

OSPF Troubleshooting (v2/v3) practice questions

Practise 300-410 questions linked to OSPF Troubleshooting (v2/v3).

BGP Troubleshooting practice questions

Practise 300-410 questions linked to BGP Troubleshooting.

Route Redistribution practice questions

Practise 300-410 questions linked to Route Redistribution.

Policy-Based Routing (PBR) practice questions

Practise 300-410 questions linked to Policy-Based Routing (PBR).

VRF-Lite practice questions

Practise 300-410 questions linked to VRF-Lite.

Route Maps and Route Filtering practice questions

Practise 300-410 questions linked to Route Maps and Route Filtering.

Administrative Distance practice questions

Practise 300-410 questions linked to Administrative Distance.

Route Summarization practice questions

Practise 300-410 questions linked to Route Summarization.

Bidirectional Forwarding Detection (BFD) practice questions

Practise 300-410 questions linked to Bidirectional Forwarding Detection (BFD).

VPN Technologies practice questions

Practise 300-410 questions linked to VPN Technologies.

Practice this exam

Start a free 300-410 practice session

Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.

10 questions 20 questions 30 questions 50 questions Timed 30

300-410 practice-test guide →Study guide →Browse all practice tests

FAQ

Questions learners often ask

What does this 300-410 question test?

SPAN, RSPAN, and ERSPAN — This question tests SPAN, RSPAN, and ERSPAN — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: CoPP is policing the locally generated ERSPAN packets, causing them to be dropped. — ERSPAN mirrored packets are process-switched by the router's control plane, meaning the route processor handles encapsulation and forwarding. In Cisco IOS, Control Plane Policing (CoPP) applied to the control plane input can affect locally generated traffic if the traffic matches a CoPP class. The CoPP policy in this scenario polices all incoming traffic to the control plane, and even though ERSPAN packets are generated locally (not incoming), the act of generating them involves the control plane, and the policy may classify them as control plane traffic. This can cause the ERSPAN packets to be dropped. This is a known pitfall where CoPP inadvertently impacts ERSPAN traffic.

What should I do if I get this 300-410 question wrong?

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 →

How Courseiva writes practice questions · Editorial policy

Keep practising

Question Discussion

Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.

Loading comments…

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.