Comptia

IPv4 gives every networked device a 32-bit address split across classes and subnets. Here is how IPv4 addressing works, why it still runs the internet, and its limits.

The OSI model's seven layers explain how data moves from application to wire. Here is each layer, the key protocols, and how to use the model for troubleshooting.

Straight-through cables connect PC to switch or router; crossover cables connect like to like. Here is the pinout, color code, and when Auto-MDIX makes it moot.