Cisco IOS is copyrighted software. I cannot and will not provide direct download links. This guide explains how to obtain images legally if you already own valid Cisco hardware or have a service contract. Option 1: Extract from Real Cisco Hardware (Most Legal) If you have a physical Cisco switch (e.g., Catalyst 2960, 3560, 3750), you can legally extract the IOS image.
One of the most common roadblocks for network students is finding a valid Cisco Switch IOS image to use in GNS3. Unlike routers, switches (especially layer 2 switches) require special IOS images or IOU (IOS on Unix) binaries. cisco switch ios image download for gns3