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Question 299 of 1,052
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CCNA Practice Question: Which TWO actions are valid when using Wireshark…
This 200-301 practice question tests your understanding of 200-301 exam topics. 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 TWO actions are valid when using Wireshark or embedded packet capture (EPC) on IOS-XE to troubleshoot Layer 2 or Layer 3 issues?
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
✓
Apply a Wireshark display filter like 'tcp.stream eq 0' to follow a specific TCP conversation and inspect application data.
Option B is correct because Wireshark's 'Follow TCP Stream' reconstructs the TCP session payload, helping identify application-layer issues that affect Layer 3 connectivity. Option D is correct because EPC on IOS-XE allows filtering by protocol (e.g., IP, ARP) to isolate Layer 2 or Layer 3 problems. Option A is incorrect because Wireshark cannot change interface duplex settings—it only captures frames. Option C is incorrect because EPC captures traffic on the control plane, not the data plane directly; data plane capture requires SPAN or other methods. Option E is incorrect because Wireshark cannot decode proprietary Cisco ISL; it only supports standard 802.1Q.
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.
- ✗
Use Wireshark to change the duplex setting of a switch interface to improve capture quality.
Why it's wrong here
Wireshark is a passive capture tool and cannot modify interface hardware settings like duplex; such changes must be made via the device CLI.
- ✓
Apply a Wireshark display filter like 'tcp.stream eq 0' to follow a specific TCP conversation and inspect application data.
- ✗
Use embedded packet capture on IOS-XE to capture traffic on the data plane by specifying the 'data' keyword in the capture point.
Why it's wrong here
EPC captures control plane traffic; data plane capture requires a switch port analyzer (SPAN) or similar feature.
- ✓
Configure an embedded packet capture on IOS-XE with a filter to capture only ARP packets to troubleshoot Layer 2 address resolution issues.
Why this is correct
EPC supports access-list-based filters; filtering for ARP (protocol 0x0806) allows focused capture of Layer 2 ARP requests and replies, aiding in troubleshooting address resolution.
Related concept
Access ports place end devices into a single VLAN.
- ✗
Use Wireshark to decode Cisco proprietary ISL trunking frames without additional configuration.
Why it's wrong here
Wireshark does not support ISL (Inter-Switch Link) natively; it only decodes standard 802.1Q VLAN tags.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓Apply a Wireshark display filter like 'tcp.stream eq 0' to follow a specific TCP conversation and inspect application data.Correct answer▾
Why this is correct
This filter isolates a single TCP stream, allowing the user to see the full session payload, which is useful for troubleshooting Layer 4 and above issues that impact Layer 3 connectivity.
✗Use Wireshark to change the duplex setting of a switch interface to improve capture quality.Wrong answer — click to see why▾
Why this is wrong here
This action is outside Wireshark's capabilities.
✗Use embedded packet capture on IOS-XE to capture traffic on the data plane by specifying the 'data' keyword in the capture point.Wrong answer — click to see why▾
Why this is wrong here
The 'data' keyword is not used in EPC; it targets control plane packets.
✗Use Wireshark to decode Cisco proprietary ISL trunking frames without additional configuration.Wrong answer — click to see why▾
Why this is wrong here
ISL is a legacy Cisco protocol and not included in Wireshark's dissectors.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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
Similar concept trap
EPC captures control plane traffic; data plane capture requires a switch port analyzer (SPAN) or similar feature.
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 200-301 questions on switching, trunking, and access-port configuration.
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FAQ
Questions learners often ask
What does this 200-301 question test?
Access ports place end devices into a single VLAN.
What is the correct answer to this question?
The correct answer is: Apply a Wireshark display filter like 'tcp.stream eq 0' to follow a specific TCP conversation and inspect application data. — Option B is correct because Wireshark's 'Follow TCP Stream' reconstructs the TCP session payload, helping identify application-layer issues that affect Layer 3 connectivity. Option D is correct because EPC on IOS-XE allows filtering by protocol (e.g., IP, ARP) to isolate Layer 2 or Layer 3 problems. Option A is incorrect because Wireshark cannot change interface duplex settings—it only captures frames. Option C is incorrect because EPC captures traffic on the control plane, not the data plane directly; data plane capture requires SPAN or other methods. Option E is incorrect because Wireshark cannot decode proprietary Cisco ISL; it only supports standard 802.1Q.
What should I do if I get this 200-301 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 200-301 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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