350-401 Question #478: Real Exam Question with Answer & Explanation

Question

Refer to the exhibit. An engineer attempts to configure a trunk between switch SW1 and switch SW2 using DTP, but the trunk does not form. Which command should the engineer apply to switch SW2 to resolve this issue?

Options

• Aswitchport mode dynamic desirable
• Bswitchport nonegotiate
• Cno switchport
• Dswitchport mode access

Explanation

DTP Trunk Formation Explanation

Option A is correct because when SW1 is configured with switchport mode dynamic auto, it passively waits for the other switch to initiate trunking - it will never actively negotiate. SW2 must be set to switchport mode dynamic desirable, which actively sends DTP negotiation frames, allowing the trunk to successfully form between the two switches.

Why the distractors are wrong:

• Option B (switchport nonegotiate) disables DTP entirely, which would prevent trunking negotiation rather than enable it
• Option C (no switchport) converts the port to a routed Layer 3 interface, which is unrelated to trunk configuration
• Option D (switchport mode access) forces the port into access mode, which actively prevents a trunk from forming

Memory Tip: Think of it as a handshake - Auto is shy and waits to be approached, while Desirable is outgoing and initiates the conversation. Two "shy" (auto) ports will never initiate with each other, so you need at least one "desirable" port to get the trunk talking. Remember: Auto + Auto = No Trunk, but Desirable + Auto = Trunk ✓

No community discussion yet for this question.