This 200-301 practice question tests your understanding of switching and network access. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. A key principle to apply: a VLAN (Virtual Local Area Network) segments a switch into multiple broadcast domains to isolate traffic logically within the same physical network.. 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 switch displays this output:
Port Name Status Vlan Fa0/1 connected 10 Fa0/2 connected 10 Fa0/24 connected trunk
Which port should be checked first if a user in VLAN 20 cannot reach the distribution switch over the uplink?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Fa0/1
Why wrong: Fa0/1 is an access port in VLAN 10.
Fa0/2
Why wrong: Fa0/2 is also an access port in VLAN 10.
Fa0/24
Correct. The trunk carries inter-switch VLAN traffic.
Any access port in VLAN 1
Why wrong: The uplink is the more relevant first check.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Fa0/24
If users in VLAN 20 must cross the uplink, the trunk port is the first place to verify allowed VLANs and tagging.
Key principle: A VLAN (Virtual Local Area Network) segments a switch into multiple broadcast domains to isolate traffic logically within the same physical network.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Fa0/1
Why it's wrong here
Fa0/1 is an access port in VLAN 10.
When this WOULD be correct
In a different scenario where the question specifies that VLAN 10 is experiencing connectivity issues or misconfigurations affecting users on that VLAN, checking Fa0/1 would be appropriate to troubleshoot the problem.
Fa0/2
Why it's wrong here
Fa0/2 is also an access port in VLAN 10.
When this WOULD be correct
In a scenario where the question specifies that VLAN 20 is configured on Fa0/2 and the user is attempting to reach a device on VLAN 20, checking Fa0/2 would be the correct action to troubleshoot connectivity issues related to that specific VLAN.
Fa0/24
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
A VLAN (Virtual Local Area Network) segments a switch into multiple broadcast domains to isolate traffic logically within the same physical network.
Any access port in VLAN 1
Why it's wrong here
The uplink is the more relevant first check.
When this WOULD be correct
In a scenario where the question asks which access port in VLAN 1 should be checked for connectivity issues affecting users in VLAN 1, option D would be correct. This could involve a misconfiguration or a device connected to an access port in VLAN 1 that is not functioning properly.
Option-by-option analysis
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.
Why this is correct
Correct. The trunk carries inter-switch VLAN traffic.
Why this is wrong here
Fa0/1 is connected to VLAN 10, and since the user in VLAN 20 cannot reach the distribution switch, checking this port would not address the issue, as it is not part of the user's VLAN.
★ When this WOULD be the correct answer
In a different scenario where the question specifies that VLAN 10 is experiencing connectivity issues or misconfigurations affecting users on that VLAN, checking Fa0/1 would be appropriate to troubleshoot the problem.
Why candidates choose this
Candidates may choose Fa0/1 due to its status as a connected port, mistakenly believing that any active port could be relevant to the user's connectivity issue without considering VLAN assignments.
Why this is wrong here
Fa0/2 is connected to VLAN 10, which means it cannot facilitate communication for a user in VLAN 20. The issue lies with the trunk port, which is responsible for carrying multiple VLANs, including VLAN 20.
★ When this WOULD be the correct answer
In a scenario where the question specifies that VLAN 20 is configured on Fa0/2 and the user is attempting to reach a device on VLAN 20, checking Fa0/2 would be the correct action to troubleshoot connectivity issues related to that specific VLAN.
Why candidates choose this
Candidates may choose Fa0/2 because it is an active port and they might assume that any connected port could potentially be involved in the issue, especially if they misunderstand VLAN configurations.
Why this is wrong here
Option D is incorrect because it suggests checking any access port in VLAN 1, which is not relevant to the user's issue in VLAN 20. The problem lies with the trunk port not allowing VLAN 20 traffic, not with access ports in VLAN 1.
★ When this WOULD be the correct answer
In a scenario where the question asks which access port in VLAN 1 should be checked for connectivity issues affecting users in VLAN 1, option D would be correct. This could involve a misconfiguration or a device connected to an access port in VLAN 1 that is not functioning properly.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of VLANs, thinking that any access port might be relevant for troubleshooting connectivity issues, regardless of the specific VLAN in question.
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
Don't confuse access ports with trunk ports; only trunk ports can carry multiple VLANs.
Detailed technical explanation
VLANs are fundamental in segmenting a physical switch into multiple logical networks, isolating broadcast domains and improving network efficiency and security. Access ports are configured to belong to a single VLAN and forward untagged frames to devices, while trunk ports carry traffic for multiple VLANs by tagging frames with VLAN IDs using the 802.1Q standard. This tagging allows switches to identify which VLAN a frame belongs to when it traverses inter-switch links. In a scenario where a user in VLAN 20 cannot reach the distribution switch, the first step is to verify the trunk port connecting the access switch to the distribution switch. This trunk port must be configured to allow VLAN 20 traffic and properly tag frames for VLAN 20. If VLAN 20 is not allowed or the trunk is misconfigured, traffic from VLAN 20 devices cannot traverse the uplink, causing connectivity failures. Access ports assigned to VLAN 10, as in the example, do not impact VLAN 20 traffic beyond the local switch. A common exam trap is to focus troubleshooting on access ports in the wrong VLAN, such as VLAN 10, when the issue involves VLAN 20 traffic crossing the uplink. Since access ports only affect local device VLAN membership, the trunk port configuration is the critical point for inter-switch VLAN communication. In practical networks, ensuring trunk ports carry all necessary VLANs prevents segmentation issues and maintains proper VLAN traffic flow across the network backbone.
Key takeaway
A VLAN (Virtual Local Area Network) segments a switch into multiple broadcast domains to isolate traffic logically within the same physical network.
Real-world example
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
Review a VLAN (Virtual Local Area Network) segments a switch into multiple broadcast domains to isolate traffic logically within the same physical network., then practise related 200-301 questions on the same topic to reinforce the concept.
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FAQ
Switching and Network Access — This question tests Switching and Network Access — A VLAN (Virtual Local Area Network) segments a switch into multiple broadcast domains to isolate traffic logically within the same physical network..
The correct answer is: Fa0/24 — If users in VLAN 20 must cross the uplink, the trunk port is the first place to verify allowed VLANs and tagging.
Review a VLAN (Virtual Local Area Network) segments a switch into multiple broadcast domains to isolate traffic logically within the same physical network., then practise related 200-301 questions on the same topic to reinforce the concept.
Yes — watch for: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
A VLAN (Virtual Local Area Network) segments a switch into multiple broadcast domains to isolate traffic logically within the same physical network.
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Last reviewed: May 17, 2026
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