Network Fundamentals
OSI and TCP/IP layers, the devices at each layer, and how a packet actually travels.
IP Addressing & Subnetting
CIDR notation, subnet masks, usable host ranges — the most tested topic in the interview.
Port Testing & Diagnostics
netstat, telnet, Test-NetConnection, nmap and PowerShell — the diagnostic core of this job.
DNS, DHCP & Name Resolution
How names become addresses, how addresses are handed out, and how each one fails.
VLANs & Routing
Why networks are segmented, how VLANs and trunks work, and the loops that take a site down.