Chapter 10. Routers

SOME OF THE MAIN TOPICS IN THIS CHAPTER ARE

What Routers Do 148

The Difference Between Routable Protocols and Routing Protocols 150

When Do You Need to Use a Router? 151

Router Ports and Connections 157

Configuring Routers 158

Router Chassis Types 159

Routers are perhaps one of the most misunderstood devices found in a network. After you create a LAN using simple devices such as switcheswhich require little or no configurationmanaging a router can be very intimidating. Some of the reasons for this include

• Most people do not understand the difference between a connectivity device, such as a switch, and a router. This is compounded by the popularity of devices that include both router and switch functionality in one box. After all, they both can be used to connect computers to a LAN, right?

• Unless you use sophisticated network console management software, the management and configuration interface for most routers often seems cryptic.

• Like computers, routers have an "operating system" that controls how they function. There is no universal operating system that can be learned for use with routers from different vendors.

• Routers come in all sizes and shapes. You can find a small, inexpensive router to connect a small office LAN to a broadband connection (such as DSL or a cable modem). Still larger standalone and rack-mounted units can be used for Enterprise networks. At the high end of this market are powerful machines used as Internet core routers.

In this chapter you will learn about the functions performed by routersfrom those at the low end of the scale to the top of the line. In addition, this chapter introduces some of the topics that enable routers to be used as a firewall.

Firewalls are discussed in more detail in Chapter 45, "Firewalls."