The correct conclusion is that DTP is enabled on this interface, as confirmed by the line “Negotiation of Trunking: On.” This output directly indicates that Dynamic Trunking Protocol (DTP) is active, allowing the switch to negotiate trunking with a neighboring device. In the context of the ENCOR 350-401 exam, interpreting the show interfaces switchport command for DTP status is a core skill, as it tests your ability to distinguish between administrative configuration and operational reality. A common trap is confusing “Administrative Mode: trunk” with DTP being off—DTP can be enabled even on a statically set trunk, as shown here. The key is to always look for the “Negotiation of Trunking” field; if it says “On,” DTP is actively sending and receiving frames. For a quick memory tip, remember: “Negotiation On means DTP is on, regardless of the mode.”
350-401 VLANs and Trunking Practice Question
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:
Why wrong: Administrative mode is 'trunk', not 'access'.
B
DTP is enabled on this interface.
'Negotiation of Trunking: On' indicates DTP is enabled.
C
The native VLAN is tagged with 802.1Q.
Why wrong: Actually, native VLAN tagging is enabled, meaning the native VLAN is tagged, but the statement is ambiguous. However, the correct interpretation is that native VLAN tagging is enabled, but the question asks what can be concluded. Option B is more directly supported.
D
All VLANs except 2-1001 are pruned.
Why wrong: Pruning VLANs Enabled: 2-1001 means those VLANs are eligible for pruning, not that they are pruned.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
DTP is enabled on this interface.
The output shows 'Negotiation of Trunking: On', which indicates that Dynamic Trunking Protocol (DTP) is enabled on the interface. DTP is a Cisco proprietary protocol used to negotiate trunking between switches. Since the interface is in trunk mode and DTP is on, option B is correct.
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.
'Negotiation of Trunking: On' indicates DTP is enabled.
Related concept
Read the scenario before looking for a memorised answer.
✗
The native VLAN is tagged with 802.1Q.
Why it's wrong here
Actually, native VLAN tagging is enabled, meaning the native VLAN is tagged, but the statement is ambiguous. However, the correct interpretation is that native VLAN tagging is enabled, but the question asks what can be concluded. Option B is more directly supported.
✗
All VLANs except 2-1001 are pruned.
Why it's wrong here
Pruning VLANs Enabled: 2-1001 means those VLANs are eligible for pruning, not that they are pruned.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between 'Pruning VLANs Enabled' and 'Trunking VLANs Enabled', where candidates mistakenly think that VLANs listed under pruning are actively removed from the trunk, when in fact they are only eligible for pruning if VTP pruning is enabled.
Detailed technical explanation
How to think about this question
DTP uses three modes: Dynamic Auto, Dynamic Desirable, and Trunk. When 'Negotiation of Trunking: On' is displayed, it means DTP packets are being sent and received on the interface. In a real-world scenario, if a switchport is set to 'dynamic auto' and the neighbor is also 'dynamic auto', the link will remain an access link; DTP must be actively negotiating to form a trunk. The 'Administrative Native VLAN tagging: enabled' setting is often used to prevent VLAN hopping attacks by ensuring native VLAN frames are tagged, but it does not change the fact that the native VLAN is still VLAN 1 by default.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 350-401 question in full detail.
VLANs and Trunking — This question tests VLANs and Trunking — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: DTP is enabled on this interface. — The output shows 'Negotiation of Trunking: On', which indicates that Dynamic Trunking Protocol (DTP) is enabled on the interface. DTP is a Cisco proprietary protocol used to negotiate trunking between switches. Since the interface is in trunk mode and DTP is on, option B is correct.
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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