Collision and Broadcast Domains

Two ideas explain how switches and hubs shape traffic on a LAN: the collision domain and the broadcast domain. They sound similar but are different, and confusing them is a common mistake. Mastering this distinction is one of the most testable parts of the Network+ exam, because it reveals exactly what switches, hubs, and routers each do to traffic.

A collision domain is a part of a network where two devices transmitting at the same time can collide, corrupting both frames. Collisions happen on shared media like a hub or old coax bus, where everyone shares one wire. The more devices in one collision domain, the more collisions and the slower the network becomes under load.