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elcome to the exciting world of internetworking. This

first chapter will really help you understand the basics of internetworking
by focusing on how to connect networks together using Cisco routers and
switches. First, you need to know exactly what an internetwork is: You
create an internetwork when you take two or more LANs or WANs and con-
nect them via a router, and configure a logical network addressing scheme
with a protocol like IP.

I'll begin by exploring four things in this chapter:

Internetworking basics

Network segmentation

How bridges, switches, and routers are used to physically segment
a network

How routers are employed to create an internetwork

I'm also going to dissect the Open Systems Interconnection (OSI) model

and describe each part to you in detail, because you really need a good grasp
of it to have a solid foundation on which to build your networking knowl-
edge. The OSI model has seven hierarchical layers that were developed
to enable different networks to communicate reliably between disparate
systems. Since this book is centering upon all things CCNA, it's crucial for
you to understand the OSI model as Cisco sees it, so that's how I will be pre-
senting the seven layers of the OSI model to you.

Since there's a bunch of different types of devices specified at the different

layers of the OSI model, it's also very important to understand the many
types of cables and connectors used for connecting all those devices to a
network. We'll go over cabling Cisco devices, discussing that along with
Ethernet LANs, WAN technologies, and even how to connect a router or
switch with a console connection.

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