The answer is that the port on Switch B must be manually set to trunk mode. This is required because Switch A has been configured with switchport nonegotiate, which disables Dynamic Trunking Protocol (DTP) frame transmission. Without those DTP frames, Switch B, left at its default dynamic desirable or auto mode, will never receive a negotiation trigger and will remain in access mode, preventing the trunk from forming. On the CompTIA Network+ N10-009 exam, this scenario tests your understanding of how switchport nonegotiate trunk configuration breaks DTP negotiation—a common trap is assuming the default mode will automatically adapt. Remember that switchport nonegotiate forces both sides to be manually set to trunk mode; if one side stops talking DTP, the other cannot guess. A useful memory tip: "No DTP, no auto—manual trunk is the only way to go."
N10-009 Network Implementation Practice Question
This N10-009 practice question tests your understanding of network implementation. 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. A key principle to apply: the 'switchport nonegotiate' command disables DTP on a trunk port.. 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 is configuring a trunk link between two switches to carry VLANs 10, 20, and 30. On Switch A, the port is configured with 'switchport mode trunk' and 'switchport nonegotiate'. On Switch B, the port is left at the default configuration. Which additional configuration is required on Switch B?
Why wrong: The native VLAN should match on both ends, but the immediate problem is that the trunk is not forming at all.
B
Enable DTP on Switch B.
Why wrong: Enabling DTP (Dynamic Trunking Protocol) on Switch B would not help because Switch A will not respond to DTP due to 'nonegotiate'.
C
Manually set the port to trunk mode.
Since Switch A is set to 'nonegotiate', Switch B must be manually configured as a trunk port (e.g., 'switchport mode trunk') to establish the trunk link.
D
Configure the allowed VLAN list.
Why wrong: The allowed VLAN list controls which VLANs are permitted on the trunk, but the trunk must first be established. The lack of trunk formation is the immediate issue.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Manually set the port to trunk mode.
Switch B is left at default configuration, which on most Cisco switches means the port is in dynamic desirable or dynamic auto mode, relying on DTP to negotiate trunking. Since Switch A has 'switchport nonegotiate' configured, it will not send DTP frames, so Switch B will never receive a negotiation trigger and will remain in access mode. Therefore, the port on Switch B must be manually set to trunk mode with 'switchport mode trunk' to establish the trunk link.
Key principle: The 'switchport nonegotiate' command disables DTP on a trunk port.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Set the native VLAN to 1.
Why it's wrong here
The native VLAN should match on both ends, but the immediate problem is that the trunk is not forming at all.
✗
Enable DTP on Switch B.
Why it's wrong here
Enabling DTP (Dynamic Trunking Protocol) on Switch B would not help because Switch A will not respond to DTP due to 'nonegotiate'.
✓
Manually set the port to trunk mode.
Why this is correct
Since Switch A is set to 'nonegotiate', Switch B must be manually configured as a trunk port (e.g., 'switchport mode trunk') to establish the trunk link.
Related concept
The 'switchport nonegotiate' command disables DTP on a trunk port.
✗
Configure the allowed VLAN list.
Why it's wrong here
The allowed VLAN list controls which VLANs are permitted on the trunk, but the trunk must first be established. The lack of trunk formation is the immediate issue.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA often tests the misconception that DTP is always required or that 'switchport nonegotiate' only affects DTP on the local switch, when in fact it prevents the remote switch from ever learning that trunking is desired, forcing a manual configuration on the remote end.
Detailed technical explanation
How to think about this question
The 'switchport nonegotiate' command on Switch A disables Dynamic Trunking Protocol (DTP) entirely, meaning the port will not send or respond to DTP frames. On a default Cisco switch port (typically dynamic desirable or dynamic auto), the port will only become a trunk if it receives a DTP frame requesting trunking; without that, it remains in access mode. In a real-world scenario, if you mix vendors or disable DTP for security, you must manually configure trunk mode on both ends to ensure the link operates as an 802.1Q trunk.
KKey Concepts to Remember
The 'switchport nonegotiate' command disables DTP on a trunk port.
When DTP is disabled on one side, the other side must be manually configured as a trunk.
Default switchport mode is often 'dynamic auto' or 'dynamic desirable'.
A trunk link requires both ends to be in trunking mode to pass VLAN traffic.
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
The 'switchport nonegotiate' command disables DTP on a trunk port.
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 N10-009 question in full detail.
Review the 'switchport nonegotiate' command disables DTP on a trunk port., then practise related N10-009 questions on the same topic to reinforce the concept.
Network Implementation — This question tests Network Implementation — The 'switchport nonegotiate' command disables DTP on a trunk port..
What is the correct answer to this question?
The correct answer is: Manually set the port to trunk mode. — Switch B is left at default configuration, which on most Cisco switches means the port is in dynamic desirable or dynamic auto mode, relying on DTP to negotiate trunking. Since Switch A has 'switchport nonegotiate' configured, it will not send DTP frames, so Switch B will never receive a negotiation trigger and will remain in access mode. Therefore, the port on Switch B must be manually set to trunk mode with 'switchport mode trunk' to establish the trunk link.
What should I do if I get this N10-009 question wrong?
Review the 'switchport nonegotiate' command disables DTP on a trunk port., then practise related N10-009 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
The 'switchport nonegotiate' command disables DTP on a trunk port.
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