It only facilitates a platform to use Cisco IOS but does not provide any Cisco IOS itself if someone wants to use any Cisco device in GNS3, they must install that device’s IOS first. GNS3 does not include any Cisco IOS in its default installation since Cisco IOS has copyright laws to protect it. Cisco uses proprietary software called Cisco IOS for its routers and switches. GNS3 (Graphical Network Simulator-3) is a network simulator software used to simulate routers, switches, and other networking devices, and it runs on Cisco IOS.
