Troubleshooting VLAN Misconfiguration on vSphere Distributed Switch — Trunk vs Access Port
This VCP-DCV practice question tests your understanding of configure and manage vsphere networking. 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.
Refer to the exhibit. An administrator checks the status of a distributed switch port and sees no errors or drops. However, virtual machines on this port cannot communicate with the default gateway at 192.168.200.1. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The port is configured with Allowed VLANs 100, 200, 300, which is a trunk configuration, but the virtual machine expects an access port on VLAN 200.
The exhibit shows the port has Allowed VLANs: 100, 200, 300. This is unusual because a port should typically be assigned to a single VLAN (access port) or carry multiple VLANs (trunk port). If the port is set to allow multiple VLANs but the virtual machine expects a specific VLAN, packets may be misconfigured. However, the most likely cause is that the port is configured as a trunk port (allows multiple VLANs) when it should be an access port for VLAN 200. This can cause the virtual machine to receive traffic from other VLANs or not tag its own traffic correctly.
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 port has no allowed MAC addresses, which may cause filtering.
Why it's wrong here
No MAC filtering is configured; it's not blocking traffic.
✓
The port is configured with Allowed VLANs 100, 200, 300, which is a trunk configuration, but the virtual machine expects an access port on VLAN 200.
Why this is correct
The port should be set to VLAN 200 only (access) instead of allowing multiple VLANs. This misconfiguration leads to connectivity issues.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Access ports place end devices into a single VLAN.
✗
The MTU is set to 1500, which is standard and should work fine.
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.
Visual reference
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 VCP-DCV questions on switching, trunking, and access-port configuration.
Configure and Manage vSphere Networking — This question tests Configure and Manage vSphere Networking — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: The port is configured with Allowed VLANs 100, 200, 300, which is a trunk configuration, but the virtual machine expects an access port on VLAN 200. — The exhibit shows the port has Allowed VLANs: 100, 200, 300. This is unusual because a port should typically be assigned to a single VLAN (access port) or carry multiple VLANs (trunk port). If the port is set to allow multiple VLANs but the virtual machine expects a specific VLAN, packets may be misconfigured. However, the most likely cause is that the port is configured as a trunk port (allows multiple VLANs) when it should be an access port for VLAN 200. This can cause the virtual machine to receive traffic from other VLANs or not tag its own traffic correctly.
What should I do if I get this VCP-DCV 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 VCP-DCV questions on switching, trunking, and access-port configuration.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
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Variation 1. An administrator configures a distributed switch with a single uplink on each host and a port group with VLAN 10. After connecting a VM to the port group, the VM cannot communicate with other VMs on the same VLAN but on different hosts. What is a likely cause?
medium
✓ A.The physical switch port is set to access mode with VLAN 10.
B.The distributed switch has no teaming configured.
C.The physical switch port connected to the uplink is set to trunk mode and is tagging the VLAN.
D.The VLAN ID is not set correctly on the VM's virtual network adapter.
Why A: Option A is correct because when the physical switch port is in access mode with VLAN 10, it expects untagged frames. However, the distributed port group with VLAN 10 tags the frames with VLAN 10. This mismatch causes the physical switch to drop or mishandle the traffic, preventing the VM from communicating with other VMs on the same VLAN across hosts. Option B is incorrect because teaming is not required for basic connectivity; a single uplink suffices. Option C describes trunk mode which would actually accept tagged frames, so it would work. Option D is incorrect because the VLAN ID is configured on the port group, not on the VM's virtual adapter.
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