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CCT: Which Command Verifies Spanning-Tree Status on Cisco Switch Experiencing High CPU Utilization?

By: Author Alex Lim

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How do you check Spanning Tree Protocol (STP) status on a Cisco switch with high CPU usage? Learn why “show spanning-tree” is essential for diagnosing STP issues—key knowledge for the Cisco Certified Field Technician (CCT) exam.

Table of Contents

Question

A switch is experiencing high CPU utilization, and the technician suspects spanning-tree issues. What command should be used to verify spanning-tree status?

A. show vlan brief
B. show interfaces trunk
C. show vtp status
D. show mac address-table
E. show spanning-tree

Answer

E. show spanning-tree

Explanation

This command displays Spanning Tree Protocol (STP) status, including blocked and root ports, which helps diagnose loop-related issues.

The command to verify the spanning-tree status on a Cisco switch is show spanning-tree.

  • The show spanning-tree command provides a comprehensive view of the Spanning Tree Protocol (STP) configuration and operational status for all VLANs or a specific VLAN on the switch.
  • It displays information such as the root bridge, bridge ID, port roles (root, designated, blocked), port states (forwarding, blocking), and the status of all STP instances.
  • This command is critical for diagnosing high CPU utilization caused by STP issues, such as frequent topology changes, loops, or misconfigurations, as it allows you to identify which ports are experiencing changes or instability.
  • Using this command, you can also pinpoint ports that are blocking or forwarding and see when the last topology change occurred, which helps in isolating the cause of excessive STP recalculations and CPU spikes.

show spanning-tree displays the current STP status, port roles, and states, making it the primary tool for diagnosing and troubleshooting spanning-tree-related high CPU utilization on Cisco switches.

Cisco Certified Field Technician (CCT) certification exam practice question and answer (Q&A) dump with detail explanation and reference available free, helpful to pass the Cisco Certified Field Technician (CCT) exam and earn Cisco Certified Field Technician (CCT) certification.