GNS3 (Graphical Network Simulator) is one of the most commonly used network simulators all around the world. To learn more about GNS3 and how to install, please check our guide on how to install GNS3 on Linux Mint 20.

This guide is about how to add IOS images to GNS3. In order start a gns3 project, you need to have network devices images on your GNS3 environment. First download the images you require to your local machine and follow this guide to enable you to upload and use IOS images on GNS3.

Add IOS images to GNS3

Launch gns3 and click on edit > preferences > IOS routers > new

Navigate to you local directory images folder and upload IOS image to GNS3

Select No when gns3 asks to decompress the file because the images are already decompressed by default. Click Next

You may get a warning that using the IOS image may be unstable or buggy. Click Ok then click next

The next screen shows name and platform for the added ISO Image. If the if the information is correct, click next to continue.

In the next page, you can set the RAM you need for you device. The default value is the minimum required RAM but you can adjust accordingly then click Next

The next page enables you to install interfaces in the available slots if you are using IOS of modular devices. Select the interfaces you need and click next. After that select the desired WIC modules and click next

The next page is where we limit the CPU usage by the added device. This is useful in preventing a faulty IOS from consuming all the available CPU. You can click on idle-PC finder to use the default values.

Once you find the value for the idle-PC, click Ok then finish. Your IOS image has successfully been added. To continue to add another image, click new and follow the steps as described above. Click apply then Ok when done adding ios images

Once you finish adding images, on the left pane are icons representing IOS images. Click on the router icon to view the added images.

You have successfully added your cisco IOS images to GNS3. It is time to enjoy network simulation.

Networking lessons to help you get started:


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