Open the GNS3 application, go to Edit , and select Preferences . Add a New Template:
GNS3 requires a real Cisco IOS image to emulate a switch. Since Cisco does not provide free public images, you must obtain a legitimate .bin file from a valid source (e.g., a Cisco device you own, a lab subscription, or a support contract). This guide covers the legal acquisition steps and the configuration within GNS3. cisco switch ios image download for gns3 install