Managing local passwords on every switch does not scale. AAA with TACACS+ or RADIUS centralizes authentication, authorization, and accounting for all network devices.

VLANs segment broadcast domains. Trunks carry multiple VLANs between switches. Misconfiguring either causes connectivity issues that are notoriously hard to debug.

Every switch starts as a blank slate. Setting the hostname, securing access, and enabling SSH are the first things you do before any production config.

tcpdump is the standard packet analyzer on Linux. Every senior admin uses it to capture raw network traffic and diagnose connectivity issues at the packet level.

Everything on Linux is a file. lsof lists open files and the processes that own them. ss replaces netstat with faster, more detailed socket introspection.

TCP/IP is the backbone of modern networking. Understanding how it works is essential for anyone managing servers or networks.