CCNA Switching and Network Access Practice Question
A switchport connected to another switch is configured with `switchport mode dynamic auto` on both ends. What is the most likely outcome if neither side actively negotiates trunking?
⚠ Common exam trap
Be careful not to confuse dynamic auto with dynamic desirable. Only dynamic desirable actively negotiates 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
✓
The link is likely to remain non-trunking because both sides are waiting passively.
If both ends are set to dynamic auto, the most likely outcome is that the link does not become a trunk automatically. In plain language, both interfaces are waiting passively for the other side to initiate the negotiation. Since neither side is actively trying to form the trunk, the link typically remains non-trunking unless one side is changed to a more active mode or trunk is configured directly. This is a classic DTP behavior question because it tests whether you understand the difference between active and passive negotiation roles. The correct answer is the one that reflects the passive nature of dynamic auto on both sides.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The link is likely to remain non-trunking because both sides are waiting passively.
Why this is correct
On a switchport configured with dynamic auto, the interface passively listens for DTP frames but does not actively send them. Since the neighboring switch is also in dynamic auto, neither side initiates a trunk negotiation, so DTP never completes and the link remains in its default access mode, functioning as a normal nontrunking port.
- ✗
The link always becomes a trunk immediately.
Why it's wrong here
A dynamic auto port never forces a trunk; it only responds to DTP requests from a peer that is actively trying to trunk, such as one set to dynamic desirable or trunk. With both ends dynamic auto, no DTP initiation occurs, so the immediate formation of a trunk is impossible. Only modes like trunk or dynamic desirable actively solicit trunking.
When this WOULD be correct
In a different scenario where both switches are configured with `switchport mode trunk`, the link would always become a trunk immediately upon connection, regardless of negotiation. A question could specify that both ends are set to trunk mode, leading to this outcome.
- ✗
The link becomes a routed Layer 3 link.
Why it's wrong here
DTP negotiation occurs entirely within Layer 2 and applies only to access or trunk ports; it has no capability to transform a physical switchport into a routed Layer 3 interface. To make a port routed, you must explicitly issue the no switchport command and assign an IP address, actions that are not triggered by any DTP exchange.
When this WOULD be correct
In a different scenario, if the question specified that both switches were configured with `switchport mode access` and there was no trunk negotiation, then the link would indeed operate as a routed Layer 3 link if the switches were configured to route traffic.
- ✗
All VLANs are deleted from both switches.
Why it's wrong here
Dynamic Trunking Protocol only exchanges DTP TLVs that advertise trunking capabilities and desired states; it carries no VLAN database information. VLAN creation, modification, and deletion are separate administrative operations executed through commands like vlan database or global vlan configuration, so a DTP negotiation on a link cannot delete any VLANs on either switch.
When this WOULD be correct
In a different scenario where a question states that a switchport is configured to delete VLAN information upon a specific command or configuration change, option D could be correct. For example, if the question involved a command that explicitly removes VLAN configurations, then this option would apply.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓The link is likely to remain non-trunking because both sides are waiting passively.Correct answer▾
Why this is correct
On a switchport configured with dynamic auto, the interface passively listens for DTP frames but does not actively send them. Since the neighboring switch is also in dynamic auto, neither side initiates a trunk negotiation, so DTP never completes and the link remains in its default access mode, functioning as a normal nontrunking port.
✗The link always becomes a trunk immediately.Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because `switchport mode dynamic auto` does not force immediate trunking; it relies on negotiation, and if neither side actively negotiates, the link remains non-trunking.
★ When this WOULD be the correct answer
In a different scenario where both switches are configured with `switchport mode trunk`, the link would always become a trunk immediately upon connection, regardless of negotiation. A question could specify that both ends are set to trunk mode, leading to this outcome.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of dynamic trunking protocols, mistakenly believing that any configuration involving 'dynamic' would automatically result in trunking without considering the negotiation process.
✗The link becomes a routed Layer 3 link.Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because a switchport configured with `switchport mode dynamic auto` does not automatically convert to a routed Layer 3 link unless explicitly configured to do so. The default behavior is to remain in access mode unless trunking is negotiated.
★ When this WOULD be the correct answer
In a different scenario, if the question specified that both switches were configured with `switchport mode access` and there was no trunk negotiation, then the link would indeed operate as a routed Layer 3 link if the switches were configured to route traffic.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of switchport modes and the assumption that dynamic configurations imply automatic Layer 3 functionality, leading to confusion between access and trunking modes.
✗All VLANs are deleted from both switches.Wrong answer — click to see why▾
Why this is wrong here
Option D is incorrect because configuring `switchport mode dynamic auto` does not delete VLANs; it merely affects trunk negotiation. VLANs remain configured on the switches regardless of trunking status.
★ When this WOULD be the correct answer
In a different scenario where a question states that a switchport is configured to delete VLAN information upon a specific command or configuration change, option D could be correct. For example, if the question involved a command that explicitly removes VLAN configurations, then this option would apply.
Why candidates choose this
Candidates may find this option tempting due to a misunderstanding of how switchport configurations impact VLANs, leading them to incorrectly associate trunking negotiation failures with VLAN deletion.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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Related to this question
Learn chapter
Configuring Switch Ports for Desktops, VoIP Phones, APs, IoT, and Virtualized Hosts
Key term
Dynamic auto
Dynamic auto is a switchport trunking mode where the port will automatically form a trunk if it receives a trunk negotiation request from the other device, but will not actively initiate trunking.
Key term
Switch
A switch is a networking device that connects devices on a local area network and uses MAC addresses to forward data only to the intended recipient.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 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 200-301 exam.