You have learned a complete troubleshooting methodology:
Structured approach: Define the problem, form a theory, test it, implement the fix, and verify. Work through OSI layers from physical up.
Diagnostic tools: Ping tests reachability. Traceroute shows the path. Nslookup verifies DNS. Netstat shows connections.
Packet capture: Wireshark and tcpdump reveal what happens on the wire.
Documentation: Record your work as you go. Good tickets speed resolution.
Escalation: Know when to escalate. Provide clear documentation.
Prevention: Post-incident reviews find root causes.