This 350-401 practice question tests your understanding of span and rspan. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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 runs the following command on Switch SW4:
SW4# show monitor session 4
Session 4
---------
Type : Local Session
Source VLANs :
RX Only : 10,20
Destination Ports : Gi1/0/25
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Only incoming traffic on VLANs 10 and 20 is mirrored to Gi1/0/25.
The session is local SPAN with source VLANs 10 and 20, capturing only received traffic (RX Only). The destination port Gi1/0/25 sends out the mirrored traffic with Native encapsulation and ingress disabled. This monitors incoming traffic on those VLANs.
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.
✓
Only incoming traffic on VLANs 10 and 20 is mirrored to Gi1/0/25.
Why this is correct
Source VLANs are set to RX Only, so only received traffic is captured.
Related concept
Access ports place end devices into a single VLAN.
✗
Both incoming and outgoing traffic on VLANs 10 and 20 are mirrored.
Why it's wrong here
Only RX is specified, not Both.
✗
This is an RSPAN session using VLANs 10 and 20 as remote VLANs.
Why it's wrong here
The type is Local, not Remote.
✗
The destination port Gi1/0/25 is configured to receive mirrored traffic.
Why it's wrong here
The destination port sends traffic out, not receives.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 350-401 question in full detail.
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.
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: Only incoming traffic on VLANs 10 and 20 is mirrored to Gi1/0/25. — The session is local SPAN with source VLANs 10 and 20, capturing only received traffic (RX Only). The destination port Gi1/0/25 sends out the mirrored traffic with Native encapsulation and ingress disabled. This monitors incoming traffic on those VLANs.
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.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
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 →
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.
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.
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.
Sign in to join the discussion.