4
Chapter 1
Internetworking
Cisco makes a smorgasbord of router, hub, and switch products, so it fol-
lows that by understanding all that's available from Cisco, you can make a
much more solid, informed decision about exactly which product(s) will
most strategically meet your networking needs. I'll help you with that by
going over Cisco's product line of hubs, routers, and switches in a special
section toward the end of this chapter.
I'll end this chapter by discussing the Cisco three-layer hierarchical model.
This was developed by Cisco to help you design, implement, and trouble-
shoot internetworks.
After you finish reading this chapter, you will encounter 25 review ques-
tions and three written labs, which will serve to lock the information from
this chapter into your memory. Do not skip this part of the chapter! In
addition, don't forget to go through the bonus exams as well as the flash
cards on the CD.
Internetworking Basics
B
efore we explore internetworking models and the specifications of
the OSI reference model, you've got to understand the big picture and
learn the answer to the key question: "Why is it so important to learn Cisco
internetworking?"
Networks and networking have grown exponentially over the last
15 years--understandably so. They've had to evolve at light speed just to
keep up with huge increases in basic mission-critical user needs like sharing
data and printers, as well as more advanced demands like video conferenc-
ing. Unless everyone who needs to share network resources is located in
the same office area (an increasingly uncommon situation), the challenge is
to connect the relevant and sometimes many networks together so all users
can share the networks' wealth.
It's also likely that at some point, you'll have to break up one large net-
work into a number of smaller ones because user response has dwindled to
a trickle as the network grew and grew and created LAN traffic congestion.
Breaking up a larger network into a number of smaller ones is called
network
segmentation
, and it's accomplished using
routers
,
switches
, and
bridges
.
The possible causes of LAN traffic congestion are:
Too many hosts in a broadcast domain
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