How to Add Cisco IOS to GNS3

After installing the GNS3 network simulator, the first thing you do is to copy a Router or Switch IOS image. If you don’t have IOS images, you can download the related files here.

GNS3 Cisco IOS

How to Add Cisco Router to GNS3

With GNS3 (Graphical Network Simulator-3), you can prepare for Cisco exams more extensively.

You can install this simulator software on Windows, Linux, and macOS operating systems.

You can make more professional network designs by using the images of real Cisco network devices on GNS3.

Now let’s examine how to install and run a router IOS image to GNS3.

   Step 1

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

If you select the above option, you need to install the GNS3 VM.

Run only legacy IOS on my computer

   Step 2

After selecting Run only legacy IOS on my computer, click the Next button.

Require IOS Images

   Step 3

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

Local Server Configuration

   Step 4

In the Summary window, click Finish.

Summary Window

   Step 5

Type the project name and click OK.

Creating a New Project in GNS3

   Step 6

In the New appliance template window, select Add an Router using a real IOS image (supported by Dynamips).

Add an IOS Router using a real IOS image (supported by Dynamips)

   Step 7

Click OK to continue adding the image.

IOS Wizard

   Step 8

Click Browse to specify the location of the image file.

Selecting the Image File Location

   Step 9

Select the Router image that you downloaded to your computer and click the Open button.

Selecting an Image File

   Step 10

Click the Yes button to extract the compressed GNS3 Cisco IOS image.


   Step 11

Wait while the router image is decompressing.

Decompressing IOS Image

   Step 12

After adding Router, click Next to continue.

New IOS Router Template

   Step 13

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

Name and Platform

   Step 14

Configure a RAM value on GNS3 according to your computer’s hardware specifications so that the Router can perform more efficiently and click Next.

Specifying RAM for Router or Switch

   Step 15

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

To add the FastEthernet interface to the Router 7200 as shown in the following image, select C7200-IO-FE in Slot0 and click Next.


   Step 16

You must specify 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 an appropriate value for the Router 7200.

Setting the Idle-PC Value for the Router

   Step 17

Wait while setting the Idle-PC value.

Calculating Idle-PC Value

   Step 18

Once the optimal value found, click OK to continue.

Idle-PC Value Found

   Step 19

After specifying an Idle-PC value for your router, click Finish.

Ending the Idle-PC Window

   Step 20

After you have successfully configured the router, click OK in the IOS Router Templates window.

IOS Router Templates

   Step 21

Drag and drop the Cisco Router that you added from Devices / Router to the workspace.

Drag and Drop the Cisco Router to the Workspace

   Step 22

Right-click on the router to start it.

Right-Click on the Router

   Step 23

You can check that the Router is not working at the Topology Summary.

Now, click Start to run the Router.

Operating the Router

   Step 24

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

Router CLI

   Step 25

As you can see in the image below, the Router you added on GNS3 works successfully!

Router works smoothly

   Step 26

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

show running-config

How to Add the Cisco Router to the Physical Network

You must configure a Cloud connection to add the Cisco Router to the physical network to which your desktop or laptop computer is connected.

You can also use this method to take the Router to the Internet.

   Step 1

To configure the router’s FastEthernet interface, double-click on it and open the CLI prompt, and then perform the following commands.

The important point here is to give an IP address to the FastEthernet interface from your physical network.

R1# conf t
R1(config)# interface fastethernet 0/0
R1(config-if)# ip address
R1(config-if)# no shutdown
R1# wr

Assigning the IP Address to the Router

   Step 2

Now add one Cloud to the GNS3 workspace.

Adding Cloud

   Step 3

Right-click on Cloud1.

Cabling Option

   Step 4

In the Cloud setup menu that opens, you need to select which network card your computer accesses to your physical network.

Select Wi-Fi, Ethernet, or VMnet Adapter.

Cabling the Cloud and Router

   Step 5

Connect one end of the cable to Cloud1/Wi-Fi and the other end to the FastEthernet0/0 interface you have configured.

FastEthernet0/0 Interface

   Step 6

Click the Start/Resume all devices button to start the Cloud1 and Router.

Start/Resume all devices

   Step 7

After you have added the router to the physical network, Ping the computer to test the network connection. You can see the GNS3 Router can communicate with the physical network from the image below.

GNS3 Physical Network and Internet Connection

How to Run a Cisco Router in GNS3 ⇒ Video

You can watch the video below to upload Cisco IOS to GNS3, and you can also subscribe to our YouTube channel to support us!

   Final Word

In this article, we have examined how to configure Cisco IOS to the most popular network simulator program used to prepare for the Cisco exams. Thanks for following us!

   Related Articles

♦ Cisco Router Modes
♦ Cisco Router IP
♦ Cisco Router Hostname
♦ Router IOS Images
How to Configure Cisco Router

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