The answer is that the frame is dropped because VLAN 10 is not included in the trunk’s allowed VLAN list. When an untagged frame enters Ethernet1/2, it is assigned to the native VLAN of that access port, which defaults to VLAN 10. As the frame is switched toward the egress trunk port Ethernet1/3, the switch checks the VLAN allowed list on that trunk; since VLAN 10 is not permitted, the frame is discarded at the egress interface. On the ENCOR 350-401 exam, this scenario tests your understanding of how native VLAN assignment interacts with trunk filtering—a common trap is assuming an untagged frame will always pass over a trunk, but the allowed list overrides that behavior. Remember the key rule: a trunk drops any frame whose VLAN is not in its allowed list, regardless of whether the frame is tagged or untagged. A helpful memory tip is “Allowed list first, native VLAN second”—the trunk’s permission check always happens before forwarding.
CCNP Virtualization Practice Question
This 350-401 practice question tests your understanding of virtualization. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 configured three interfaces on a switch as shown. A host connected to Ethernet1/2 sends an untagged frame. Which VLAN will this frame be placed into when it reaches Ethernet1/3?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The frame is dropped because VLAN 10 is not allowed.
The switchport on Ethernet1/3 is configured as a trunk with an allowed VLAN list that does not include VLAN 10. When the untagged frame from Ethernet1/2 enters the switch, it is assigned to the native VLAN of the access port (which is VLAN 10 by default or configuration). As the frame is switched to the trunk port Ethernet1/3, the trunk's allowed VLAN list is checked; since VLAN 10 is not permitted, the frame is dropped at the egress trunk port.
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.
✗
VLAN 999
Why it's wrong here
VLAN 999 is native on Ethernet1/1, not on Ethernet1/3.
✗
VLAN 1
Why it's wrong here
VLAN 1 is not the native VLAN on Ethernet1/3; native VLAN is 1, but frame is tagged.
✓
The frame is dropped because VLAN 10 is not allowed.
Read the scenario before looking for a memorised answer.
✗
VLAN 10
Why it's wrong here
VLAN 10 is not in the allowed list on Ethernet1/3.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between the native VLAN on a trunk and the access VLAN on an access port, leading candidates to mistakenly think the frame will use the trunk's native VLAN (999) instead of being dropped because the access VLAN (10) is not allowed.
Detailed technical explanation
How to think about this question
When an untagged frame arrives on an access port, the switch assigns it the access VLAN (here VLAN 10) and internally tags it. For the frame to exit a trunk port, the trunk's allowed VLAN list must include that VLAN; otherwise, the frame is discarded at egress. This behavior is governed by IEEE 802.1Q trunking and the 'switchport trunk allowed vlan' command, which filters VLANs at the egress, not ingress. In real-world scenarios, misconfigured allowed VLAN lists are a common cause of connectivity issues when extending VLANs across trunks.
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.
Virtualization — This question tests Virtualization — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The frame is dropped because VLAN 10 is not allowed. — The switchport on Ethernet1/3 is configured as a trunk with an allowed VLAN list that does not include VLAN 10. When the untagged frame from Ethernet1/2 enters the switch, it is assigned to the native VLAN of the access port (which is VLAN 10 by default or configuration). As the frame is switched to the trunk port Ethernet1/3, the trunk's allowed VLAN list is checked; since VLAN 10 is not permitted, the frame is dropped at the egress trunk port.
What should I do if I get this 350-401 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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