Routers

A router connects devices on LANs to devices on other LANs, usually via WANs, as shown in Figure C-4.

Figure C-4 A Router Connects Devices on LANs to Devices on Other LANs, Usually Via WANs

Figure C-4 A Router Connects Devices on LANs to Devices on Other LANs, Usually Via WANs

A router has a lot of "smarts." When companies started deploying PCs and connecting them via LANs, they soon wanted to go one step further and interconnect LANs and PCs located at geographically separate locations. The router provides this facility. The router will connect to a local LAN and then connect over a longer distance to another router, which in turn is connected to the remote LAN. Two PCs located hundreds of miles apart can now exchange data.

A router's job is comprised of the following tasks:

• Segment LANs and WANs

• Figure out the best way to send data to its destination

• Talk to other routers to learn from them and tell them what it knows

• Send the data the best way, over a LAN or a WAN

When devices are connected via a router, a device will hear only the following:

• Everything that the other devices on its port send

• Any information from devices on other ports that was meant for devices on its port

A device connected to a router will not hear any of the information meant just for devices on other ports, nor any information from devices on other ports that was meant for everyone.

Cisco has a large selection of routers, including the following series:

Cisco 700 Cisco 800 Cisco 1000 Cisco 1600 Cisco 1720 Cisco 2500 Cisco 2600 Cisco 7500

Cisco 3600

Cisco MC3810 multiservice concentrator Cisco 4000

Cisco AS5200/AS5300/AS5800 access servers Cisco 7200 Cisco 12000

Generally the bigger the series number, the more LAN and WAN ports the router has and the better performance it provides.

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