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- So before we get into the details

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of downloading the
software and pairing it up

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with Cisco iOS images and everything else

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that's involved with that I just want

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to take a step back for a moment and talk

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a little about GNS3 from the standpoint

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of is it a simulator or is it an emulator

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and what's the difference
and quite frankly

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why should I care what the difference is?

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Now GNS3, even though
it does have the word

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simulator in it, graphical
network simulator,

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the word simulator's in
there because it's really

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simulating network
topologies, it's allowing you

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to build network topologies
without the real hardware

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and the real cables in front of you.

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So that's where it's
really simulating things.

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But GNS3 itself is actually
what we call an emulator.

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Now what's the difference?

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Well when we say that
something is an emulator

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that that means that
that software is running

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an actual network operating system.

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It's actually running
in this particular case,

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the real Cisco iOS image
or maybe the June OS image

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or whatever other images
your import into it.

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What's the difference
between that and a simulator?

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Well a simulator is a
program that was built

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from scratch to sort of look
and feel like the software

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but it's not really the software.

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For example, way back when
you were first learning

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about let's say Microsoft Windows,

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let's take that as an example,

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there's some soft route
there that you can,

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on a CD plug into your CD
rom drive your DVD rom drive

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of your laptop and it
will bring up a window

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that looks like Microsoft
Windows and for tutorial purposes

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it'll say okay move your mouse over here

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and click on this button.

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Move your mouse over
here and click over here.

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So it's a software that's
built to look like windows

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but it's very limited right?

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Maybe it only allows
you to hit start and run

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or maybe it only allows you to click

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this particular icon but
all the various things

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that Windows can do it
can't do because a simulator

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is not the real software.

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So I'm sure you're familiar with a lot

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of simulation platforms out there,

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especially when you're studying for

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your Cisco certification exams.

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A lot of simulations
out there but what's one

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key component that they all have in common

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that's kind of difficult?

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They don't give you access
to all the commands,

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there's a lot of stuff that
you can't do in simulators

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because Cisco iOS is huge, it's massive,

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it's hundreds of
thousands of lines of code

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and a simulator just
can't come close to that.

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But GNS3 is an emulator.

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In other words, GNS3 provides the platform

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where you import your
actual Cisco iOS images,

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real Cisco iOS that would
run on a real router

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and then GNS gives you a nice gooey,

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a nice front end that
runs those iOS images.

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So actually whatever
those iOS images support,

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whatever commands, whatever debugs,

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whatever show commands they
support, you now get in GNS3.

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It's not just a simple,
very generic vanilla

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simulation program it is actually
emulating real Cisco iOS.

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So that is why when you're using GNS3

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you have to somehow have
access to a Cisco iOS image

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because it's going to require that.

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So that's all I want to talk about

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in this section about the difference

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between a simulator and
an emulator and hopefully

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I've gotten across to you
the idea that an emulator

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is much more powerful,
gives you a full set

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of the features, it's the exact same thing

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you are using the exact same
software as you would use

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in a real environment with real hardware.

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So in the next section
we're going to start

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talking about considerations.

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You know once you've got this opportunity

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to select various iOS
images, what are some

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of the things you have to think about

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because you want to make sure you select

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the correct one and put it in GNS3

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so everything works according to

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your specifications and your needs.

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And we'll talk about that
in the next set of videos.