Download 3640 Switch IOS image for Gns3| 3600 Series: GNS3 is network simulator and offers number of ways to emulate Cisco Image or other IOS. YOu can run different Cisco IOS images in gns3 with Dynamips.
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In Gns3 by default there is no way of running Cisco switch, but using Cisco 3640 IOS image you can convert your router into switch. There is a module i.e. NM-16ESW module which can be used with Cisco 3640 IOS in gns3 and provide you the switching features in GNS3. There are many cisco images which supports NM-16ESW-module, such Switch IOS images for GNS3 is 3600 series c3640.