GNS3 appliances are pre-defined device templates. Typically, to emulate a Cisco IOS router or other device on GNS3, you must first create a template. By importing an appliance file (.gns3a), you can easily create a template for the device you wish to emulate.

You can add FRR (Free Range Routing) container to GNS3 and use it as a software router.
This page explains how to add the FRR container and an example of interconnection with Cisco IOS routers.

This page explains how to add a Docker container’s lightweight Linux host on GNS3.

The IOS of the actual device is necessary to emulate the Cisco router with GNS3.
This section explains how to download the IOS image file for an actual router.

This page explains how to install GNS3 on Windows 10.

Create a GNS3 project and perform various verifications with GNS3.
This page explains how to create a GNS3 project in detail.

To create a network diagram for the GNS3 project, we first create a router template.
This section explains the steps for creating an IOS router template.