GNS3 how to obtain Cisco IOS images
GNS3 emulator software is free, but the related Cisco IOS images you require to use it are not. Cisco owns the copyright on IOS so they can’t be shared freely. You’ll have to purchase them, or get them from someone who has legal access to them.
Links
https://forum.networklessons.com/t/how-to-prepare-for-cisco-ccnp-r-s/1051/40?u=lagapides
https://forum.networklessons.com/t/ospf-loop-free-alternate-lfa-fast-reroute-frr/2228/39?u=lagapides