June 14, 2021

Add Cisco IOS on GNS3

The first thing to do after installing the GNS3 network simulator program is to add a Cisco Router or Switch IOS image. If you don’t have IOS images, you can download the related files from here.

How to Add Cisco Router on GNS3?

You can install this simulator software on Windows, Linux and macOS operating systems. You can make more professional network designs on GNS3 by using IOS images of real Cisco network devices. Let’s examine how to add and run a router IOS image to GNS3.

After installing GNS3, run the program and select “Run only legacy IOS on my computer” in the Setup Wizard window.

Setup Wizard "Run only legacy IOS on my computer"
Setup Wizard “Run only legacy IOS on my computer”

 

Leave the default settings in the “Local Server Configuration” window and click the “Next” button.

Local Server Configuration
Local Server Configuration

 

Click the “Finish” button in the Summary window.

Summary window
Summary window

 

Type the project name and click the “OK” button. Select where you want to register your project by clicking the “Browse” button.

Project name
Project name

 

In the “New appliance template” window, select “Add an IOS Router using a real IOS image (supported by Dynamips)” option and click the “OK” button to continue the IOS add steps.

New appliance template
New appliance template

 

Click the Browse button to specify the location of the image file.

IOS Image
IOS Image

 

Click the Yes button to extract the compressed IOS image.

IOS Image decompress
IOS Image decompress

Wait while the router image is decompressed.

IOS Image decompress
IOS Image decompress

 

After adding iOS, continue by clicking “Next” button.

IOS Image
IOS Image

 

After configuring the name and platform of the version of the Cisco Router you added, click “Next” button.

Name and Platform
Name and Platform

 

In order for the Router to work better on GNS3, configure a RAM value according to the hardware features of your computer and click the “Next” button.
Router Memory
Router Memory

 

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In the Network Adapters window, you can choose which slots you want to add to the Router.

To add the FastEthernet interface to the Router 7200 as in the image below, select “C7200-IO-FE” in Slot0 and click the “Next” button.

Router Network
Router Network

 

You must set an Idle-PC value for the router. This value may vary depending on the performance of your computer.

Click the “Idle-PC Finder” button to set a suitable value for the Router 7200.

Idle-PC Finder
Idle-PC Finder

Wait while setting the “Idle-PC” value.

Idle-PC
Idle-PC

 

After finding the most suitable value, continue by clicking the “OK” button.

Idle-PC Value
Idle-PC Value

 

After setting an “Idle-PC” value for your router, click the “Finish” button.

Idle-PC
Idle-PC

 

After adding the router successfully, click the “OK” button in the “IOS Router Templates” window.

IOS Router Templates
IOS Router Templates

 

Drag and drop the Cisco Router you added from the “Devices / Router” section to the workspace.

Devices / Router
Devices / Router

 

To run the router, right-click on it.

Router Right Click
Router Right Click

 

You can check that the router is not currently running in “Topology Summary”.

Now, click on “Start” to run the Router.

Topology Summary
Topology Summary

 

When the router is running, the Red icon in the “Topology Summary” will be Green. To configure the router, you can open the “CLI” command prompt by double-clicking on it.

Topology Summary
Topology Summary

 

As you can see in the image below, the Router you added on GNS3 is working successfully.

router works without errors
router works without errors

 

For example, you can check the running configuration file of the Cisco Router using the “R1 # show running-config” command.
Show running-config
Show running-config

 

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