- A
The destination port is not in the same VLAN as the source port.
Why wrong: Incorrect because SPAN can monitor traffic across different VLANs; the destination port does not need to be in the same VLAN.
- B
The destination port is configured as a trunk port.
Why wrong: Incorrect because a trunk port can be a SPAN destination; this would not prevent traffic forwarding.
- C
The destination port is in a blocking state due to Spanning Tree Protocol.
Correct because SPAN destination ports are not expected to participate in STP; they should be configured with 'spanning-tree portfast' to avoid blocking.
- D
The source interface is not in the same VLAN as the destination interface.
Why wrong: Incorrect because SPAN does not require the source and destination to be in the same VLAN; the destination port simply receives a copy of the traffic.
Quick Answer
The answer is that the SPAN destination port is in a blocking state due to Spanning Tree Protocol. This occurs because a SPAN destination port, by default, participates in STP, and the switch will place it into a blocking state to prevent loops—even though the port is only receiving copied traffic and should never forward normal frames. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding that a SPAN destination port must be explicitly configured with the `spanning-tree portfast` command to bypass the STP listening and learning phases, immediately transitioning to a forwarding state. A common trap is assuming that simply designating an interface as a SPAN destination automatically disables STP, but it does not; the port remains vulnerable to STP blocking until PortFast is enabled. To remember: think of the SPAN destination as a “listener only”—it needs PortFast to skip the STP handshake and start forwarding immediately.
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.
A network engineer configures SPAN on a Cisco Catalyst switch to monitor traffic between two hosts. The engineer configures the source interface as GigabitEthernet0/1 and the destination interface as GigabitEthernet0/2. After the configuration, the engineer notices that the monitored traffic is not being forwarded to the destination port. 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
The destination port is in a blocking state due to Spanning Tree Protocol.
SPAN destination ports must be configured with the 'spanning-tree portfast' command to avoid being blocked by Spanning Tree Protocol (STP). Without this, the destination port may remain in a blocking state.
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 destination port is not in the same VLAN as the source port.
Why it's wrong here
Incorrect because SPAN can monitor traffic across different VLANs; the destination port does not need to be in the same VLAN.
- ✗
The destination port is configured as a trunk port.
Why it's wrong here
Incorrect because a trunk port can be a SPAN destination; this would not prevent traffic forwarding.
- ✓
The destination port is in a blocking state due to Spanning Tree Protocol.
Why this is correct
Correct because SPAN destination ports are not expected to participate in STP; they should be configured with 'spanning-tree portfast' to avoid blocking.
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 interface is not in the same VLAN as the destination interface.
Why it's wrong here
Incorrect because SPAN does not require the source and destination to be in the same VLAN; the destination port simply receives a copy of the traffic.
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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SPAN, RSPAN, and ERSPAN — study guide chapter
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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 destination port is in a blocking state due to Spanning Tree Protocol. — SPAN destination ports must be configured with the 'spanning-tree portfast' command to avoid being blocked by Spanning Tree Protocol (STP). Without this, the destination port may remain in a blocking state.
What should I do if I get this 300-410 question wrong?
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.
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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Last reviewed: Jun 19, 2026
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.
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