The answer is three specific symptoms: a missing `monitor session 1 source` command on the source switch, the RSPAN VLAN not being allowed on the trunk between switches, and the destination switch lacking the RSPAN VLAN configuration. These three failures directly break the RSPAN data path because RSPAN relies on a dedicated VLAN to carry mirrored traffic across the network—if the source switch isn’t capturing traffic, the trunk isn’t transporting the VLAN, or the destination switch isn’t listening for it, the session simply cannot deliver packets. On the Cisco CCNP ENARSI 300-410 exam, this question tests your understanding of Layer 2 SPAN architecture versus remote SPAN, often appearing as a multi-select item where common distractors like native VLAN mismatch or routing protocol issues are intentionally wrong. A helpful memory tip is to think of the three links in the RSPAN chain: capture, transport, and receive—if any one is broken, the session fails.
300-410 SPAN, RSPAN, and ERSPAN Practice Question
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.
Which THREE symptoms indicate a misconfigured RSPAN session on a Cisco switch? (Choose THREE.)
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 not allowed on the trunk between the source and destination switches.
RSPAN requires a dedicated VLAN (RSPAN VLAN) that is trunked across the network. If the RSPAN VLAN is not allowed on the trunk, traffic fails to reach the destination. If the destination switch does not have the RSPAN VLAN configured, the session cannot receive traffic. A missing 'monitor session' command on the source switch means no traffic is being captured. A native VLAN mismatch does not specifically affect RSPAN, and a routing protocol issue is not directly related to Layer 2 RSPAN.
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 not allowed on the trunk between the source and destination switches.
Why this is correct
The RSPAN VLAN must be permitted on all trunk links in the path for traffic to traverse.
Related concept
Access ports place end devices into a single VLAN.
✓
The destination switch does not have the RSPAN VLAN created.
Why this is correct
The destination switch must have the RSPAN VLAN defined to receive the monitored traffic.
Related concept
Access ports place end devices into a single VLAN.
✓
The source switch is missing the 'monitor session 1 source' command.
Why this is correct
Without a source defined, no traffic is captured for the RSPAN session.
Related concept
Access ports place end devices into a single VLAN.
✗
The native VLAN mismatch on the trunk link.
Why it's wrong here
Native VLAN mismatch causes CDP errors but does not directly prevent RSPAN traffic in the RSPAN VLAN.
✗
The routing protocol is not redistributing the RSPAN VLAN.
Why it's wrong here
RSPAN operates at Layer 2; routing protocols do not affect it.
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 300-410 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 300-410 questions on switching, trunking, and access-port configuration.
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 not allowed on the trunk between the source and destination switches. — RSPAN requires a dedicated VLAN (RSPAN VLAN) that is trunked across the network. If the RSPAN VLAN is not allowed on the trunk, traffic fails to reach the destination. If the destination switch does not have the RSPAN VLAN configured, the session cannot receive traffic. A missing 'monitor session' command on the source switch means no traffic is being captured. A native VLAN mismatch does not specifically affect RSPAN, and a routing protocol issue is not directly related to Layer 2 RSPAN.
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.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
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