5.5. Network Connectivity Issues

💡 First Principle: Network troubleshooting must be layer-by-layer — physical first, then logical. Chasing DNS records when the cable is unplugged wastes time. The OSI model provides the framework: start at Layer 1 (physical) and work up only after each layer is confirmed healthy.

The exam tests both the diagnostic reasoning (what layer is the problem in?) and the specific tools and commands used to test each layer.