Routers

By the way, 'router' is pronounced in the American fashion - it rhymes with "doubter". To avoid embarrassment in class, don't call it a "rooter"!

There are a few uses for routers.

1. A router is a security device that connects a LAN to the outside world (another LAN or a WAN.)  It can be programmed to only allow authorised incoming and outgoing traffic. For example, it might block certain external sites or not allow MP3 music files to come in. It behaves like a bouncer at the door of a club, who controls who is allowed in.

A smaller router

2. Routers are also used to protect one part of a network from another part of the same network, e.g. a school network may be divided into a curriculum LAN for students and an administration LAN for staff and the LANs would be isolated from each other with a router so students could not access the admin LAN, but admin could access the student network.

3. While the common-or-garden router is a little black box used to protect a LAN or divide a LAN into sections, internet service providers will have routers that are HUGE computers which are used to intelligently bounce IP packets toward their destination. It's these routers that actually do the work to get your IP requests where they are supposed to go, and to get your data back from the destination to you.

Bigger routers.

The biggest router manufacturer is Cisco, and they make millions out of the things!

And please don't confuse network routers with the woodworking tools!