Most users of internetworks donít communicate with routers, they communicate through them. Network administrators, however, must deal directly with individual routers in order to install and manage them.
Routers are purpose-built computers dedicated to internetwork processing. They are important devices that individually serve hundreds or thousands of usersósome serve even more. When a router goes down, or even just slows down, users howl and network managers jump. As you might imagine then, network administrators demand foolproof ways to gain access to the routers they manage in order to work on them.
Routers donít come with a monitor, keyboard, or mouse, so you must communicate with them in one of three other ways:
▼ From a terminal thatís in the same location as the router and is connected to it via a cable (the terminal is usually a PC or workstation running in terminal mode).
■ From a terminal thatís in a different location as the router and is connected to it via a modem that calls a modem connected to the router with a cable.
▲ Via the network on which the router sits.
In large networks, network administrators are often physically removed from routers and must access them via a network. However, if the router is unreachable due to a network problem, or if thereís no modem attached to the router itself, someone must go to its location and log directly into the router. The three ways to gain administrative access to routers are depicted in Figure 4-5.
Even when network administrators manage routers in the same building, they still prefer to access them by network. It doesnít make sense to have a terminal hooked up to each router, especially when there are dozens of them stacked in a data closet or computer room. Also, itís much more convenient to manage them all from a single PC or workstation.
There are several way to communicate with a router each made possible by a particular communications protocol. Table 4-2 lists each metod, the protocol, and how each is used.
This chapter is from Cisco: A Beginner's Guide, by Velte and Velte (McGraw-Hill/Osborne, 2004, ISBN: 0072256354). Check it out at your favorite bookstore today. Buy this book now.
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