STP Troubleshooting STP 1 — Questions and Answers
Question 1: What is a broadcast storm in a switched network?
- Continuous flooding of broadcast frames caused by a Layer 2 loop, consuming all bandwidth (Correct answer)
- A weather event affecting networking
- High volume of regular traffic
- A DNS flood attack
Correct answer: Continuous flooding of broadcast frames caused by a Layer 2 loop, consuming all bandwidth
A broadcast storm occurs when frames loop endlessly through redundant paths, multiplying exponentially and consuming all network bandwidth.
Question 2: How do you verify the current STP root bridge?
- Use show spanning-tree command to display root bridge ID, priority, and port roles (Correct answer)
- Check the physical labels on switches
- Look at the IP routing table
- Use ping to find the root
Correct answer: Use show spanning-tree command to display root bridge ID, priority, and port roles
The show spanning-tree command displays the root bridge information, local bridge details, and port states and roles.
Question 3: What are common symptoms of an STP failure?
- Network slowness, high CPU on switches, MAC address table instability, broadcast storms (Correct answer)
- Slow internet browsing only
- Email delays
- Printer not responding
Correct answer: Network slowness, high CPU on switches, MAC address table instability, broadcast storms
STP failures typically manifest as network-wide performance issues caused by looping traffic overwhelming switch resources.
Question 4: How do you change the STP root bridge priority?
- Configure a lower bridge priority value on the desired root bridge switch (Correct answer)
- Move the physical switch
- Change the MAC address
- Update the IP address
Correct answer: Configure a lower bridge priority value on the desired root bridge switch
Setting a lower priority value (e.g., 4096) ensures the desired switch wins the root bridge election.
Question 5: What happens when a root bridge fails in STP?
- A new root bridge election occurs using the bridge with the next lowest bridge ID (Correct answer)
- The network permanently stops
- All ports go to blocking
- Manual intervention is always required
Correct answer: A new root bridge election occurs using the bridge with the next lowest bridge ID
When the root bridge fails, the network automatically elects a new root bridge based on the next lowest bridge ID.
Question 6: What is the impact of a suboptimal STP topology?
- Traffic takes longer paths, increased latency, underutilized links, and potential congestion (Correct answer)
- No impact on performance
- Only affects specific VLANs
- Only causes cosmetic issues in monitoring
Correct answer: Traffic takes longer paths, increased latency, underutilized links, and potential congestion
A poorly designed STP topology forces traffic along inefficient paths, wasting bandwidth on some links while overloading others.
STP Troubleshooting STP 1
What is a broadcast storm in a switched network?