Network Troubleshooting

1. 1. The "User Can't Reach X" Mindset
2. 2. A Practical OSI Model for Diagnosis
3. 3. Local Connectivity: Interfaces, IP Configuration & the Default Gateway
4. 4. DNS Resolution Troubleshooting
5. 5. Testing the Path: ping and traceroute/tracert — What They Actually Prove
6. 6. Port & Service-Level Checks: telnet, curl & netcat
7. 7. Firewalls & Blocked Traffic
8. 8. Proxies, VPNs & NAT: When the Path Isn't What You Expect
9. 9. Application-Layer Symptoms: HTTP & TLS-Specific Failures
10. 10. Capstone — Triaging Three Real Connectivity Tickets