The answer is that VLAN 30 must be created in the global VLAN database first. This is required because on Cisco Nexus switches running NX-OS, a VLAN must be explicitly defined with the `vlan 30` command in global configuration mode before it can carry traffic, even if it is allowed on a trunk interface. Without this global creation, the VLAN does not exist in the switch’s VLAN database, so the interface will drop all frames for that VLAN, causing the ESXi host to lose communication. On the Cisco DCCOR 350-601 exam, this concept tests your understanding of the NX-OS VLAN lifecycle, which differs from classic IOS where VLANs can sometimes be created dynamically via VTP. A common trap is assuming that adding a VLAN to an interface’s allowed list is sufficient—it is not; the VLAN must first be born globally. Remember the memory tip: “Create it globally before you trunk it locally.”
350-601 Network Practice Question
This 350-601 practice question tests your understanding of network. 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.
Exhibit
show running-config interface ethernet 1/1
!
interface Ethernet1/1
switchport mode trunk
switchport trunk allowed vlan 10,20,30
spanning-tree port type edge trunk
no shutdown
Refer to the exhibit. An engineer is configuring a server-facing interface on a Nexus switch. The server is running VMware ESXi with multiple virtual machines in VLANs 10, 20, and 30. After applying the configuration, the ESXi host reports that it cannot communicate on VLAN 30. Which configuration change should be made?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create VLAN 30 in the global VLAN database
Option C is correct because VLAN 30 must exist in the global VLAN database before it can be used on any interface. Even though the interface configuration allows VLAN 30 as a trunked VLAN, the switch will not forward traffic for a VLAN that has not been created globally. Without the 'vlan 30' command in global configuration mode, the VLAN is not present in the switch's VLAN database, and the interface will not pass traffic for that VLAN.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Remove the 'spanning-tree port type edge trunk' command
Why it's wrong here
Edge trunk is appropriate for server-facing ports and does not cause communication failure.
✗
Change the native VLAN to 30
Why it's wrong here
Native VLAN is used for untagged traffic; not the issue here.
✓
Create VLAN 30 in the global VLAN database
Why this is correct
If VLAN 30 does not exist, the switch will not forward traffic for it even if allowed on the trunk.
Related concept
Read the scenario before looking for a memorised answer.
✗
Configure the port as an access port in VLAN 30
Why it's wrong here
The server expects trunk mode; changing to access would break other VLANs.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that configuring a VLAN on an interface (e.g., 'switchport trunk allowed vlan add 30') automatically creates the VLAN in the global database, but in NX-OS, the VLAN must be explicitly created first.
Detailed technical explanation
How to think about this question
In Cisco NX-OS, VLANs must be explicitly created in the global VLAN database using the 'vlan <vlan-id>' command before they can be used on any interface, even if the interface is configured as a trunk. This differs from some other platforms where VLANs can be dynamically created when configured on an interface. A common real-world scenario is when an engineer adds a new VLAN to a trunk but forgets to create it globally, resulting in no traffic being forwarded for that VLAN, which can be verified with 'show vlan' or 'show interface trunk' commands.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Network — This question tests Network — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create VLAN 30 in the global VLAN database — Option C is correct because VLAN 30 must exist in the global VLAN database before it can be used on any interface. Even though the interface configuration allows VLAN 30 as a trunked VLAN, the switch will not forward traffic for a VLAN that has not been created globally. Without the 'vlan 30' command in global configuration mode, the VLAN is not present in the switch's VLAN database, and the interface will not pass traffic for that VLAN.
What should I do if I get this 350-601 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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