A Review: Layer 2 Ethernet Switches
Switches are not used to create internetworks; they are employed to add functionality to a network LAN. The main purpose of a switch is to make a LAN work better: to optimize its performance; providing more bandwidth for the LAN's users. Switches don't forward packets to other networks as routers do. Instead, they only "Switch" frames from one port to another within the switched network. By default, switches break up collision domains. This is an Ethernet term used to describe a network scenario where in one particular device sends a packet on a network segment, forcing every other device on that same segment to pay attention to it.