This 350-401 practice question tests your understanding of vlans and trunking. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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.
A network engineer runs the following command on Switch SW1:
SW1# show interfaces gi0/1 trunk
Port Mode Encapsulation Status Native vlan Gi0/1 desirable n-802.1q trunking 1
Port Vlans allowed on trunk Gi0/1 1-1005
Port Vlans allowed and active in management domain Gi0/1 1,10,20
Port Vlans in spanning tree forwarding state and not pruned Gi0/1 1,10,20
Based on this output, what can be concluded?
The interface is configured as an access port.
Why wrong: Mode 'desirable' indicates trunk configuration.
The trunk is using ISL encapsulation.
Why wrong: Encapsulation is n-802.1q (negotiated 802.1Q).
VLANs 2-9 are allowed but not active.
Allowed VLANs are 1-1005, but only 1,10,20 are active; thus VLANs 2-9 are allowed but not active.
The native VLAN is 10.
Why wrong: Native VLAN is 1.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
VLANs 2-9 are allowed but not active.
The output shows that VLANs 1-1005 are allowed on the trunk, but only VLANs 1, 10, and 20 are active in the management domain. This means VLANs 2-9 and 11-19, 21-1005 are allowed but not active (i.e., not created or not present on the switch). Option C correctly identifies that VLANs 2-9 are among those allowed but not active.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The interface is configured as an access port.
Why it's wrong here
Mode 'desirable' indicates trunk configuration.
The trunk is using ISL encapsulation.
Why it's wrong here
Encapsulation is n-802.1q (negotiated 802.1Q).
VLANs 2-9 are allowed but not active.
Why this is correct
Allowed VLANs are 1-1005, but only 1,10,20 are active; thus VLANs 2-9 are allowed but not active.
Related concept
Read the scenario before looking for a memorised answer.
The native VLAN is 10.
Why it's wrong here
Native VLAN is 1.
Common exam traps
The trap here is that candidates often confuse 'allowed on trunk' with 'active in management domain', leading them to assume all allowed VLANs are actually forwarding traffic, when in fact only those listed in the second line are active.
Detailed technical explanation
The 'Vlans allowed on trunk' line lists all VLANs that are permitted to traverse the trunk (1-1005 by default), while 'Vlans allowed and active in management domain' shows only VLANs that exist on the switch and are in a forwarding state. A VLAN must be created and active on the switch to be listed in the second line; otherwise, it is considered 'allowed but not active' and traffic for those VLANs will not be forwarded. This distinction is critical for troubleshooting inter-VLAN routing and pruning.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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
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FAQ
VLANs and Trunking — This question tests VLANs and Trunking — Read the scenario before looking for a memorised answer..
The correct answer is: VLANs 2-9 are allowed but not active. — The output shows that VLANs 1-1005 are allowed on the trunk, but only VLANs 1, 10, and 20 are active in the management domain. This means VLANs 2-9 and 11-19, 21-1005 are allowed but not active (i.e., not created or not present on the switch). Option C correctly identifies that VLANs 2-9 are among those allowed but not active.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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