hardMultiple ChoiceObjective-mapped
200-901 Practice Question: Refer to the exhibit
Exhibit
Refer to the exhibit. """ interface GigabitEthernet0/1 description Uplink to Core switchport mode trunk switchport trunk allowed vlan 10,20,30 spanning-tree portfast trunk """
Refer to the exhibit. A switch is configured with the shown trunk port. After connecting the uplink, the switch logs show repeated 'errdisable' state transitions on this port. The core switch is configured with the same allowed VLAN list. Which configuration change is most likely to resolve the issue?
⚠ Common exam trap
Cisco often tests the misconception that 'spanning-tree portfast trunk' is safe for trunk ports, but the trap is that PortFast combined with BPDU guard (even if not explicitly configured, but enabled globally) causes errdisable when BPDUs are received, so the fix is to remove PortFast from the trunk.
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
✓
Remove the spanning-tree portfast trunk command from the interface.
The 'errdisable' state transitions on a trunk port are typically caused by a spanning-tree BPDU guard violation when PortFast is enabled. The 'spanning-tree portfast trunk' command enables PortFast on the trunk, which bypasses the normal listening/learning states and can cause the port to be placed into errdisable state if a BPDU is received from the core switch. Removing this command allows the trunk port to participate in standard spanning-tree convergence, preventing the repeated errdisable transitions.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Change the switchport mode to dynamic desirable.
Why it's wrong here
The core is likely configured as trunk, so dynamic desirable may cause negotiation issues, not errdisable.
- ✗
Add VLAN 1 to the allowed VLAN list.
Why it's wrong here
VLAN 1 is native by default and does not need to be explicitly allowed; adding it would not fix errdisable.
- ✓
Remove the spanning-tree portfast trunk command from the interface.
Why this is correct
Portfast trunk is designed for host-facing trunks (e.g., to servers) and can cause STP issues when connecting to another switch.
- ✗
Add the spanning-tree bpduguard enable command to the interface.
Why it's wrong here
BPDU guard would disable the port if it receives BPDUs, which is normal on a trunk to another switch, worsening the issue.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-901 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 200-901 exam.