Gns3 IOS for Switch:
In Gns3 by default there is no such option for creating switch topology, but you can use the router as a switch with NM-16ESW module. There are number of IOS which can support NM-16ESW module, one of most common Switch IOS for GNS3 is 3600 series c3640.
Using this IOS you can perform different Gns3 labs like:
You can download gns3 switch IOS from following link:
You learn how to use switch in GNs3.