2.3. Network Configuration and Tools

Network misconfiguration is the most common cause of "server is unreachable" incidents. A typo in a netplan YAML file, a missing default gateway, or a wrong DNS resolver will silently break connectivity in ways that are hard to diagnose remotely — because the tools you'd use to diagnose them are themselves unreachable. Getting network configuration right the first time matters.

💡 First Principle: Linux network configuration has two separate concerns: interface configuration (IP address, gateway, DNS — done by NetworkManager or Netplan) and network diagnostics (testing, tracing, capturing — done by the ip suite and standalone tools). These are completely different toolsets serving different purposes.

⚠️ Common Misconception: Candidates confuse ifconfig (deprecated) with ip (current). The ip command from iproute2 replaces ifconfig, route, and netstat. On a modern system, ifconfig may not even be installed. The exam tests ip, ss, and related modern tools.