|  | 3.1 | Basic LAN Devices
| 3.1.9 | Routers

The router is the first device that you will work with that is at the OSI network layer, or otherwise known as Layer 3. Working at Layer 3 allows the router to make decisions based on groups of network addresses (Classes) as opposed to individual Layer 2 MAC addresses. Routers can also connect different Layer 2 technologies, such as Ethernet, Token-ring, and FDDI. However, because of their ability to route packets based on Layer 3 information, routers have become the backbone of the Internet, running the IP protocol.
The purpose of a router is to examine incoming packets (Layer 3 data), choose the best path for them through the network, and then switch them to the proper outgoing port. Routers are the most important traffic-regulating devices on large networks. They enable virtually any type of computer to communicate with any other computer anywhere in the world! While performing these basic functions, routers can also execute many other tasks that are covered in later chapters.
The symbol for a router (Note the inward- and outward-pointing arrows.) is suggestive of its two primary purposes - path selection, and switching of packets to the best route. A router can have many different types of interface ports. Figure shows a serial port which is a WAN connection. The graphic also shows the console port connection which allows direct connection to the router to be able to configure it. Figure shows another port interface type. The type shown is an Ethernet port which is a LAN connection. This particular router has both a 10BASE-T and AUI connector for the Ethernet connection.

| Web Links
| Cisco Systems