Cisco IOS images are copyrighted software. You must have a valid Cisco account with an active service contract (like SMARTnet) or own the physical hardware to legally download the images from Cisco’s official website. This guide assumes you already have legal access.

Not all Cisco images work well in GNS3. Because GNS3 uses a hypervisor to emulate hardware, specific series of routers and switches are optimized for this environment.

If you loaded an "IOSv" image, it boots as a router by default. To make it a switch:

  • Match image to GNS3 appliance requirements (RAM/CPU). Prefer images labeled for virtualization (IOSv, IOSvL2, or IOU/IOL).

    • Warning: Cisco IOS images are copyrighted. Downloading images you are not licensed to use may violate Cisco’s terms and local law. Use official sources (Cisco support/VIRL) or images you own a license for.