CCNA Switching and Network Access Practice Question
A network administrator is troubleshooting a Cisco switch that is experiencing high CPU utilization. The administrator suspects a Layer 2 loop. Which command can be used to verify if Spanning Tree Protocol (STP) has blocked any ports due to a loop?
⚠ Common exam trap
A common mix-up: candidates confuse commands that show interface status or MAC addresses with those that show STP information. Only show spanning-tree directly displays STP port states.
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
✓
show spanning-tree
The show spanning-tree command is the correct tool to verify STP port states, including blocking. It shows the root bridge, port roles, and states for each VLAN, allowing the administrator to confirm if STP has blocked a port to prevent a loop.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
show interfaces status
Why it's wrong here
The show interfaces status command provides a summary of interface status, including connected, notconnect, and err-disabled states. It does not show STP port states such as blocking or forwarding. Therefore, it is not useful for verifying STP blocking due to a loop.
- ✗
show ip interface brief
Why it's wrong here
The show ip interface brief command displays IP addresses and interface status for Layer 3 interfaces. It does not provide any information about STP or Layer 2 port states. It is used for IP connectivity troubleshooting, not for STP loop detection.
- ✓
show spanning-tree
Why this is correct
The show spanning-tree command displays the STP status for each VLAN, including which ports are in blocking state. If a loop exists, STP will block redundant ports to prevent loops. This command helps identify blocked ports and verify the root bridge and port roles.
- ✗
show mac address-table
Why it's wrong here
The show mac address-table command displays the MAC address table, showing which MAC addresses are learned on which ports. While a loop can cause MAC address flapping, this command alone does not directly show STP blocking states. It might show multiple ports with the same MAC, but it does not confirm STP blocking.
Visual reference
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Related to this question
Learn chapter
Cisco ISE Overview
Key term
Root bridge
The root bridge is the central reference point in a Spanning Tree Protocol (STP) network, serving as the logical root of the spanning tree topology.
Key term
CAN
A CAN (Controller Area Network) is a robust vehicle bus standard designed to allow microcontrollers and devices to communicate with each other without a host computer.
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JA
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
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.