CCNA Switching and Network Access Practice Question
A network technician is connecting a new access switch to an existing distribution switch. The access switch will carry multiple VLANs. The technician wants to ensure that the link becomes a trunk automatically if the other side is set to desirable mode. Which command should be configured on the access switch port?
⚠ Common exam trap
A common mix-up: candidates confuse dynamic auto with dynamic desirable, or thinking that nonegotiate still allows automatic trunking.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
switchport mode dynamic auto
The switchport mode dynamic auto command places the port in a passive trunking state where it will become a trunk if the other side actively negotiates. When the distribution switch is set to dynamic desirable, it will initiate trunking, and the access switch will respond. This allows the link to form a trunk automatically without manual intervention.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
switchport mode dynamic auto
Why this is correct
Dynamic auto mode allows the port to become a trunk if the other side initiates trunking. If the distribution switch is set to desirable mode, it will actively attempt to form a trunk, and the access switch port in dynamic auto mode will respond and become a trunk. This meets the requirement of automatic trunk formation.
- ✗
switchport mode dynamic desirable
Why it's wrong here
Dynamic desirable mode actively attempts to convert the link to a trunk. While this would also result in a trunk if the other side is desirable, the scenario specifies that the technician wants the link to become a trunk if the other side is set to desirable. Dynamic auto is the more passive setting that waits for the other side to initiate, which is the typical expectation when the other side is desirable.
- ✗
switchport mode access
Why it's wrong here
This command forces the port into permanent access mode, which means it will not form a trunk. Even if the other side is set to desirable mode, the port will remain an access port and will not negotiate trunking. This would prevent the link from carrying multiple VLANs as required.
- ✗
switchport nonegotiate
Why it's wrong here
This command disables DTP negotiation entirely. The port will not send or respond to DTP frames, so it will not automatically become a trunk based on the other side's configuration. It must be manually configured as a trunk. This does not meet the requirement for automatic trunk formation.
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Related to this question
Learn chapter
802.1Q Trunking
Key term
Switchport
A switchport is a physical or virtual interface on a network switch that connects devices like computers, printers, or other switches to a local area network.
Key term
Dynamic desirable
A Cisco proprietary switchport mode that makes a port actively request to form a trunk but also allow the port to become a trunk if the connected device requests it.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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