Download or obtain the IOS file that you want to use on GNS3. In this way you can utilize the maximum of you RAM and can run the maximum number of routers in GNS3 as compare to any other IOS like 7200 series which required high RAM. Cisco 1700c is a very cool IOS for gns3 as it required a very little RAM.
I also show you how to add Docker containers to your network. Installing and importing Cisco IOS in GNS3. From this article you can download 1700c GNS3 IOS image for router only for GNS3 use. How do you build Cisco networks in GNS3? In this video I show you how to download Cisco IOS images (Cisco VIRL images) to run IOSv and IOSvL2 in your GNS3 topologies.