Question 227 of 2,152

SPAN, RSPAN, and ERSPAN →hardMultiple ChoiceObjective-mapped

Quick Answer

The answer is that the RSPAN VLAN is also being used for other VLAN traffic due to misconfiguration. This occurs because an RSPAN VLAN must be dedicated exclusively to the mirroring session; if it is allowed as a native VLAN or mapped to other data VLANs on the trunk, the destination port will forward broadcast and unicast traffic from those other VLANs instead of only the mirrored traffic from VLAN 30. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of RSPAN isolation requirements and is a common trap where engineers forget to prune the RSPAN VLAN from all other VLAN assignments. A key memory tip is to treat the RSPAN VLAN like a private highway—if you let other cars (VLANs) onto it, you will not see the specific traffic you intended to monitor.

300-410 SPAN, RSPAN, and ERSPAN Practice Question

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

An engineer configures an RSPAN session on a Cisco switch to monitor traffic from VLAN 30 and send it to a remote switch. The engineer creates RSPAN VLAN 200 on both switches and configures the trunk to allow VLAN 200. On the remote switch, the engineer configures the destination port as GigabitEthernet0/4 in VLAN 200. The engineer notices that the destination port is forwarding traffic, but the traffic is not from the source VLAN 30; instead, it is broadcast traffic from other VLANs. 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.

Question 1hardmultiple choice

Open the full VLAN trunking answer →

A
The RSPAN VLAN is also being used for other VLAN traffic due to misconfiguration.
Correct because the RSPAN VLAN should be a dedicated VLAN; if it is also used as a native VLAN or for other traffic, it will carry unwanted broadcasts.
B
The source VLAN is not configured correctly on the source switch.
Why wrong: Incorrect because the source VLAN is configured; the issue is that the RSPAN VLAN is carrying extra traffic.
C
The destination port is in the wrong VLAN.
Why wrong: Incorrect because the destination port is in VLAN 200, but the problem is that VLAN 200 is not isolated.
D
The trunk is not pruning VLAN 200 correctly.
Why wrong: Incorrect because pruning is not the issue; the VLAN is allowed, but it is carrying extra traffic due to misconfiguration.

Full breakdown with real-world context →

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 RSPAN VLAN is also being used for other VLAN traffic due to misconfiguration.

RSPAN VLANs should be used exclusively for RSPAN traffic and should not have any other VLANs mapped to them. If the RSPAN VLAN is also used for other purposes, it may carry unintended traffic.

Key principle: A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.

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 RSPAN VLAN is also being used for other VLAN traffic due to misconfiguration.
Why this is correct
Correct because the RSPAN VLAN should be a dedicated VLAN; if it is also used as a native VLAN or for other traffic, it will carry unwanted broadcasts.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Access ports place end devices into a single VLAN.
✗
The source VLAN is not configured correctly on the source switch.
Why it's wrong here
Incorrect because the source VLAN is configured; the issue is that the RSPAN VLAN is carrying extra traffic.
✗
The destination port is in the wrong VLAN.
Why it's wrong here
Incorrect because the destination port is in VLAN 200, but the problem is that VLAN 200 is not isolated.
✗
The trunk is not pruning VLAN 200 correctly.
Why it's wrong here
Incorrect because pruning is not the issue; the VLAN is allowed, but it is carrying extra traffic due to misconfiguration.

Common exam traps

Common exam trap: an active trunk can still block the VLAN you need

A trunk being up does not prove every VLAN is crossing it. Check allowed VLAN lists, native VLAN mismatch, VLAN existence and access-port assignment.

Detailed technical explanation

How to think about this question

VLAN questions usually combine access-port and trunking clues. The key is to identify whether the issue is local to one switchport, caused by the trunk, or caused by the VLAN not existing where it needs to exist.

KKey Concepts to Remember

Access ports place end devices into a single VLAN.
Trunk ports carry multiple VLANs between switches.
Allowed VLAN lists decide which VLANs can cross a trunk.
Native VLAN mismatch can create confusing symptoms.

TExam Day Tips

Use show vlan brief to verify access VLANs.
Use show interfaces trunk to verify trunk state and allowed VLANs.
Do not treat every same-VLAN issue as a routing problem.

Key takeaway

A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.

Real-world example

How this comes up in practice

A help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.

What to study next

Got this wrong? Here's your next step.

Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 300-410 questions on switching, trunking, and access-port configuration.

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FAQ

Questions learners often ask

What does this 300-410 question test?

SPAN, RSPAN, and ERSPAN — This question tests SPAN, RSPAN, and ERSPAN — Access ports place end devices into a single VLAN..

What is the correct answer to this question?

The correct answer is: The RSPAN VLAN is also being used for other VLAN traffic due to misconfiguration. — RSPAN VLANs should be used exclusively for RSPAN traffic and should not have any other VLANs mapped to them. If the RSPAN VLAN is also used for other purposes, it may carry unintended 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?

Access ports place end devices into a single VLAN.

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