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THE ETERNAL STUDENT

GNS3 How to

Installation & Configuration

Nuno Lobao

2/28/2012

Copyright information: This document is destined to be used for educational purposes. It is free for non-

commercial purpose. You can copy, distribute, share and alter it the way you wish.

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Table of ContentsGNS3 Installation on Windows 7_x64............................................... ....................................................2

Getting the Tools .......................................................................... ..................................................2

Installing Wireshark Packet Sniffer ............................................................................ .......................3

Installing GNS3 ................................................ .......................................................... .....................3

Decompressing the IOS images ................................................................................ ........................8

GNS Configuration Settings . ................................................... ......................................................... ....9

Adding IOS images to GNS3 ................................................. .......................................................... 13

Configuring the Idle-PC Values .............................................. ......................................................... 14

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GNS3 Installation on Windows 7_x64

Getting the Tools

I am assuming that you are running Windows 7x64, i f youre running a 32bit version dont worry the

steps are identical, you just need to choose 32bit versions of the software instead of the x64 that Ill be

linking here, other than that just follow the procedures and you will be fine. Download 7zip from

http://downloads.sourceforge.net/sevenzip/7z920-x64.msi , save it to your computer and install it. As of

today 28-2-2012 the current stable version of GNS3 is v0.7.4, although there is a new beta version

release GNS3 v0.8.2 BETA2 which we obviously dont want to be getting into right now for obvious

reasons. Start your favorite browser and download gns3 fromhttp://www.gns3.net/download/ . Be sure

to choose the latest stable version GNS3 v0.7.4 all-in-one, because we dont have any time to loose

with futi le problems, all our time and effort is dedicated to Cisco studying and problem solving which in

my opinion is time and energy consuming enough, but we love it! Ok, save the package to yourcomputer.

Download Wireshark from http://wiresharkdownloads.riverbed.com/wireshark/win64/wireshark-

win64-1.6.5.exe and save it to your computer. If you have Microsoft Visio installed on your computer

thats fine, thats one of your main tools, but in case you dont have a diagram editor software download

Dia from http://dia-installer.de/its super cool and its free! Since GNS3 all in one package comes with

putty we are not going to worry about it. I will assume you have access to the necessary IOS images

from Cisco.

Note: Regarding Dia and 7zip, i will assume you can install them with no problem at all. Just right clickrun as administrator and follow the on screen instructions.

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Installing Wireshark Packet Sniffer

Install wireshark with elevated privileges feature simply by right clicking and choosing Run as

administrator.Follow the instructions, when it asks you to install WinPCap select it and install it, if i t

prompts you to reboot your system go ahead and reboot it. Simple as it gets.

Installing GNS3

Right click on GNS3 package that you just downloaded and selectRun as as administrator,

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The User Account Controlwill ask you if you want to allow the application to run, select Yes

Click Next like is shown in the picture

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Press the I Agree button so you can agree with the GNU GENERAL PUBLIC LICENSE.

In this part you can deselect the WinPCAP installation because it was installed along with Wireshark.

Click Next after deselecting WinPCAP.

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Depending on your hard drive configuration, choose the path to where you want to install GNS3, click

next to leave the default path toC:\Program Files (x86)\GNS3. Click Install

Click Finish to complete the installation.

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Now you have GNS3 v0.7.4 installed on your computer. Its time to configure it.

At this point we need to setup a couple of things before we actually configure GNS3 settings. This is

because GNS3 is very picky about paths and naming, expect to have problems with it without really

knowing why they are happening, but hey, its free!

Lets setup the basics. First we need to configure the folders where the IOS images are going to be

stored and the working directory where all our projects are going to be saved. I advise you to try to

create these folders GNS_Projects and GNS_IMAGES with no spacing between the words and in the

root directory of the drive you are creating them, or at least not too far beyond the root directory. In

this example iv created two folders name GNS_Projects and GNS_IMAGES on the root of my C drive.

Now copy the IOS images you have and paste them into the GNS_IMAGES folder.

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Decompressing the IOS images

As previously mentioned I use 7zip but you can use any decent image compressor/decompression

software but I strongly advise you to use 7zip. Its easy, its powerful and its free! Right click the first

image, mouse over 7zip and select Extract Here

In my case Im using c2691-adventerprisek9-mz.124-25c.binIOSimage file, the extracted or

decompressed image is named C2691-AS.BIN. For ease of management just rename the extracted image

to c2691-adventerprisek9-mz.124-25c.image. Notice that the extension file name has now changed

from .bin to .image.

Click Yes to rename the extracted image. Execute these steps for any IOS image you have.

Note: You do not have to do this though it enables the IOS images to run faster without the need to wait

to the IOS image to be decompressed. Its optional although I do recommend.

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GNS Configuration Settings

Open GNS3, the Setup Wizard comes up when we run GNS3 for the first time. Select task1 Configure

and test the path to Dynamips.

Insert the Project and Image directory created earlier like shown in the picture. Click Apply

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At this point (hopefully), a security warning should come up asking if you want to allow or deny

Dynamips executable to access Private and Public networks. SelectAllow Access.

Move on to the Capture tab. Create another folder for theWiresharkcaptures in the same root

directory of the other two folders so you wil l end up with three folders:

1- C:\GNS_IMAGES2- C:\GNS_Projects3- C:\GNS_Captures

In the Working directory for capture files in the Capture tab of GNS3 insert the path to the

GNS_Captures folder. Click Apply

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Select the Qemu tab. In the Working Directory under Qemu General Settings select or paste the

path to the GNS_Projects folder. Click Apply and clickTest.

A security warning will pop up again; Select Allow Access for both private and public networks. Click

Apply again and click OK.

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Configuring the Idle-PC Values

At this point you just need to drag the router(s) for which you have an IOS image associated to, in my

case the c2691 and the c3725. Drag them to the work area. I would not advise you to use the tool bar to

start the router(s) as this wil l start any routers you have in the work space all at the same time. This can

cause your computer to crash duo to a 100% CPU utilization. This depends on your hardware but even

with a powerful computer the best way to do this is to right click on each router (one at a time) and

select Start. Right click again and select Console to get console access. Remember GNS can be quite

tricky so try to be gentle with it.

After you start the router you will see in the lower right corner of the screen (Task Manager) the CPU is

peeking 100%. To release the CPU from this heavy util ization you need to configure the Idle-PC value.

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Right click on the router again and select Idle PC

You need to wait for a l ittle wile for the best values to be calculated, while this task is working a

windows will appear like the one bellow

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