- A
The destination port is automatically configured as a SPAN destination port, which disables normal switching on that port.
Correct; a SPAN destination port is dedicated to receiving mirrored traffic and does not forward normal traffic.
- B
The destination port must be configured as a trunk port to forward SPAN traffic.
Why wrong: Incorrect; the destination port can be an access or trunk port, but it will still not forward normal traffic.
- C
The destination port must be configured as an access port to forward SPAN traffic.
Why wrong: Incorrect; the port type does not affect the forwarding of normal traffic; it is the SPAN destination configuration that disables normal switching.
- D
The destination port is in an err-disabled state due to a loop.
Why wrong: Incorrect; the scenario does not indicate any loop or error condition.
Quick Answer
The answer is that the destination port is automatically configured as a SPAN destination port, which disables normal switching on that port. When you designate an interface as a SPAN destination, the switch immediately stops forwarding standard data traffic through it, repurposing the port exclusively for sending mirrored traffic to the monitoring station. This behavior is fundamental to SPAN operation on Cisco Catalyst switches like the 3850, ensuring the monitoring tool receives a clean copy of the source traffic without interference from normal forwarding. On the ENCOR 350-401 exam, this concept tests your understanding of how SPAN alters port behavior, often appearing as a trap where candidates assume the port is disabled or misconfigured. A common memory tip is to think of the destination port as going into "monitor-only mode"—once it receives the SPAN command, it stops switching normal frames. Remember: SPAN destination = forwarding stops for normal traffic, but the port remains active for mirrored packets.
CCNP SPAN and RSPAN Practice Question
This 350-401 practice question tests your understanding of span and rspan. 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 is monitoring traffic from a server connected to a Cisco Catalyst 3850 switch. The engineer configures a SPAN session with source interface Gi1/0/1 and destination interface Gi1/0/24. The monitoring station receives traffic, but the engineer notices that the destination port is not forwarding any normal traffic. What is the most likely reason?
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 automatically configured as a SPAN destination port, which disables normal switching on that port.
When a port is configured as a SPAN destination, it stops forwarding normal traffic by default. The port becomes a SPAN-only port. The correct answer is that the destination port is automatically put into a special state where it only sends SPAN traffic and does not forward normal data. Option B is incorrect because the destination port does not need to be in trunk mode. Option C is incorrect because the destination port does not need to be in access mode. Option D is incorrect because the destination port is not disabled; it is active for SPAN.
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 automatically configured as a SPAN destination port, which disables normal switching on that port.
Why this is correct
Correct; a SPAN destination port is dedicated to receiving mirrored traffic and does not forward normal traffic.
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 destination port must be configured as a trunk port to forward SPAN traffic.
Why it's wrong here
Incorrect; the destination port can be an access or trunk port, but it will still not forward normal traffic.
- ✗
The destination port must be configured as an access port to forward SPAN traffic.
Why it's wrong here
Incorrect; the port type does not affect the forwarding of normal traffic; it is the SPAN destination configuration that disables normal switching.
- ✗
The destination port is in an err-disabled state due to a loop.
Why it's wrong here
Incorrect; the scenario does not indicate any loop or error condition.
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.
Trap categories for this question
Scenario analysis trap
Incorrect; the scenario does not indicate any loop or error condition.
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 350-401 questions on switching, trunking, and access-port configuration.
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SPAN and RSPAN — study guide chapter
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FAQ
Questions learners often ask
What does this 350-401 question test?
SPAN and RSPAN — This question tests SPAN and RSPAN — 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 automatically configured as a SPAN destination port, which disables normal switching on that port. — When a port is configured as a SPAN destination, it stops forwarding normal traffic by default. The port becomes a SPAN-only port. The correct answer is that the destination port is automatically put into a special state where it only sends SPAN traffic and does not forward normal data. Option B is incorrect because the destination port does not need to be in trunk mode. Option C is incorrect because the destination port does not need to be in access mode. Option D is incorrect because the destination port is not disabled; it is active for SPAN.
What should I do if I get this 350-401 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 350-401 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 18, 2026
This 350-401 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 350-401 exam.
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