Ethernet Switching

Problem

Imagine 50 computers connected to the same LAN. You don't want every frame sent to every machine. The network needs to know: Which physical port leads to this MAC address?

Solution — Ethernet Switch

A switch learns from incoming frames:
MAC AA:01 → port 1
MAC BB:02 → port 7
MAC CC:03 → port 12

When a frame for BB:02 arrives, it can send it toward port 7.

Core idea: a switch learns where MAC addresses are and forwards local traffic accordingly.