Before you can learn how to configure and manage routers, however, you want to know the basics of what makes one up. These chapters give a general review of Cisco router hardware and software.

In the basic terms, internetworking is about nothing above linking machines and people through a maze of mediator telecommunications lines and computing devices. This takes routing, which in essence occupies just two fundamental missions: find out a path along which a link can be made and transmit packets across that path. It is within these two functions—which take place inside the router—that internetworking becomes easier to understand. This is because the router itself must cut all the difficulty down to a level it can deal with. The router does this by working with the whole thing, one IP packet at a time.

In basic terms, internetworking is about not only the connection of machines and people through a maze of intermediate routes telecommunications and computing devices. This takes routing, which essentially comprises only two main tasks: define a path along which a connection can be made and broadcast packets across the path. It is these two functions that take place inside the router-as networking becomes more understandable. This is because the router itself needs to cut the all complexity down to a level that can cope. The router does this by working with everything, one IP packet at a time.

Looked at in this way, the router is the basic fabric of internet works. In fact, without the router, the Internet as we know it could not even exist. This is because of the router’s unique and powerful capabilities:

• Routers can at the same time support different protocols (such as Ethernet, Token Ring, ISDN, and others), effectively making virtually all computers friendly at the internet work level.

• They impeccably connect local area networks (LANs) to wide area networks (WANs), which makes it possible to make large-scale internet works with minimum centralized planning—sort of like Lego™ sets.

• Routers filter out unwanted traffic by separating areas in which messages can be “broadcast” to all subscribers in a network.

• They work as security gates by examining traffic against access permission lists.

• Routers assure dependability by providing various paths through internet works.

• They automatically learn about new paths and choose the best ones, removing artificial constraints on expanding and improving internet works.

Simply, routers make internet works possible. They do so by providing a unified and secure environment in which large groups of people can connect. However, there are obstacles to bringing users together on internet works, whether on a

business intranet, a virtual private network, or the Internet itself. A figure shows how routing technology is the key to overcoming these obstacles.

The router’s ability to support various protocols simultaneously is perhaps its most significant feature because this capability lets otherwise incompatible computers talk with one another regardless of OS, data format, or communications medium.

The computer industry spent decades and billions of dollars are struggling to achieve compatibility between proprietary systems and met with limited success. However, less than a decade, the protocol TCP / IP internet networking have created a common platform that almost all computer architectures and the network can exchange information freely.

The router’s capacity to filter out useless traffic is also significant to internetworking. If users are got volumes of unwanted messages or if they feel their systems can be simply broken into, they will resist linking up to internet works. Traffic filtering and access control provided by routers give users enough privacy and assurance to participate in internet works.

There are other important types of network devices, other than routine, but understanding how a router works will go a long way in understanding the whole of internet networking. To be able to learn how to configure and manage routers, but you should know the basics of what makes one up. This chapter provides an overview of Cisco router hardware and software.