6.6. Reflection Checkpoint: Troubleshooting Mastery

Key Takeaways

Before proceeding, ensure you can:

• Apply the 7-step methodology—Step 1 is always "Identify the problem"
• Interpret interface counters (CRC errors = cable/interference, runts = collisions)
• Recognize APIPA (169.254.x.x) as DHCP failure
• Use ping, traceroute, and nslookup for systematic diagnosis
• Identify Layer 1 issues before investigating higher layers
• Distinguish bandwidth from latency from jitter

Self-Check Questions

1. A user reports "the network is down." Following the methodology, what do you do FIRST?

2. A workstation shows IP 169.254.15.30. What does this indicate, and where do you investigate?

3. ping to a server works, but accessing the web application fails. What layer should you investigate?