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?
Answer choices
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
Fa0/1
Fa0/1 is an access port in VLAN 10.
Fa0/2
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
The uplink is the more relevant first check.
Common exam trap
A frequent exam trap is to check access ports assigned to VLAN 10 when the connectivity issue involves a user in VLAN 20. Since access ports carry traffic for a single VLAN and do not forward traffic for other VLANs, verifying ports in VLAN 10 does not address the problem. The real issue lies in the trunk port configuration, which must carry VLAN 20 traffic to enable communication beyond the local switch. Overlooking the trunk port leads to wasted troubleshooting effort and incorrect conclusions about VLAN connectivity.
Technical deep dive
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.
Related practice questions
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
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Practise routing-table output, longest-prefix match, AD and route selection.
Practise trunk verification and VLAN forwarding across switches.
Practise WLAN security, authentication and wireless architecture concepts.
Practise IPv6 addressing, routes, neighbour discovery and common IPv6 exam traps.
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
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FAQ
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.
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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