6.3. Network Service Issues

💡 First Principle: Network services build on each other—problems cascade upward. If routing fails, everything depending on inter-network connectivity fails. If DNS fails, name-based access fails even though IP connectivity works. Systematic diagnosis identifies which service layer is actually broken.

What breaks when services fail: Users report "can't access the server"—but is it DHCP (no IP), DNS (can't resolve name), routing (can't reach destination), or the server itself? Each produces similar symptoms but requires different fixes. Understanding service dependencies means you test the right thing first: can you ping by IP? Then DNS is likely the issue. Can't ping the gateway? Check Layer 2 and addressing.

Think of service troubleshooting like diagnosing car problems: "won't start" could be battery, starter, fuel, or ignition. You check systematically rather than replacing random parts.