This guide outlines the legitimate ways to download router IOS images, the specific platforms supported, and how to integrate them into your lab environment. 1. Where to Download Router IOS Images Legally
If you own a physical Cisco router (e.g., a Cisco 3725), you can copy the IOS image directly from the device's flash memory to your computer for use in the simulator. 2. Supported Cisco IOS Router Platforms
Formerly known as VIRL, a CML Personal subscription is the most reliable legal path for students and individuals. A subscription allows you to download modern virtual images (IOSv, IOSv-L2, ASAv, etc.) that can be exported and used within GNS3.
GNS3 uses an emulator called to run older IOS images. Only specific "end-of-life" hardware platforms are supported by this method:
There are three primary authorized methods to obtain the necessary image files for GNS3: