Quick Answer
The correct actions are the switchport mode trunk and switchport trunk encapsulation dot1q commands. The switchport mode trunk command unconditionally sets the interface to trunk mode, forcing it to carry traffic for multiple VLANs using the 802.1Q tagging standard. The switchport trunk encapsulation dot1q command explicitly defines the trunking protocol as IEEE 802.1Q, which is necessary on older Catalyst switches that support both Cisco’s proprietary ISL and the open 802.1Q standard; on modern switches, encapsulation is fixed to dot1q, but the command remains valid for explicit configuration. On the ENCOR 350-401 exam, this topic tests your understanding of Layer 2 trunking fundamentals and the distinction between dynamic trunking protocols and manual trunk setup. A common trap is assuming switchport mode trunk alone is sufficient on older platforms—without setting the encapsulation, the interface may default to ISL or remain in access mode. Memory tip: “Mode for the traffic, encapsulation for the tag”—mode sets the trunk state, encapsulation picks the tagging method.
This 350-401 practice question tests your understanding of infrastructure. 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.
Which TWO actions are valid for configuring 802.1Q trunking on a Cisco switch? (Choose two.)
switchport mode dynamic auto
Why wrong: Auto mode waits for the neighbor to initiate trunking.
switchport mode trunk
This command enables trunking.
switchport mode access
Why wrong: Access mode disables trunking.
switchport trunk native vlan 1
Why wrong: This sets native VLAN but does not enable trunking.
switchport trunk encapsulation dot1q
This sets the trunking protocol to 802.1Q.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
switchport mode trunk
Option B is correct because the 'switchport mode trunk' command unconditionally sets the interface to trunk mode, enabling 802.1Q trunking. Option E is correct because 'switchport trunk encapsulation dot1q' explicitly configures the trunk encapsulation to the IEEE 802.1Q standard, which is required on older switches that support both ISL and 802.1Q.
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.
switchport mode dynamic auto
Why it's wrong here
Auto mode waits for the neighbor to initiate trunking.
switchport mode trunk
Why this is correct
This command enables trunking.
Related concept
Read the scenario before looking for a memorised answer.
switchport mode access
Why it's wrong here
Access mode disables trunking.
switchport trunk native vlan 1
Why it's wrong here
This sets native VLAN but does not enable trunking.
switchport trunk encapsulation dot1q
Why this is correct
This sets the trunking protocol to 802.1Q.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Cisco often tests the distinction between commands that configure trunking parameters (like native VLAN) versus commands that actually enable trunking mode, causing candidates to select 'switchport trunk native vlan 1' as a trunking configuration command.
Detailed technical explanation
802.1Q trunking uses a 4-byte tag inserted into Ethernet frames to identify VLAN membership, with the native VLAN (typically VLAN 1) remaining untagged. On Cisco switches that support both ISL and 802.1Q, the 'switchport trunk encapsulation dot1q' command is mandatory before setting the mode to trunk; on newer switches that only support 802.1Q, this command is not available as encapsulation is fixed. The Dynamic Trunking Protocol (DTP) governs negotiation between 'dynamic auto', 'dynamic desirable', and 'trunk' modes, and mismatched settings can lead to trunking failures.
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.
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FAQ
Infrastructure — This question tests Infrastructure — Read the scenario before looking for a memorised answer..
The correct answer is: switchport mode trunk — Option B is correct because the 'switchport mode trunk' command unconditionally sets the interface to trunk mode, enabling 802.1Q trunking. Option E is correct because 'switchport trunk encapsulation dot1q' explicitly configures the trunk encapsulation to the IEEE 802.1Q standard, which is required on older switches that support both ISL and 802.1Q.
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 11, 2026
This 350-401 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-401 exam.
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