GNS3

GNS3 is a graphical network simulator that allows you to design complex network topologies and to launch simulations on them. To allow complete simulations, GNS3 is strongly linked with [Dynamips](/armory/dynamips/), an IOS emulator which allows users to run IOS binary images from Cisco Systems, and [Dynagen](/armory/dynagen/), a text-based front-end for Dynamips. GNS3 is a excellent complementary tool to real labs for administrators of Cisco networks or people wanting to pass their CCNA, CCNP, CCIP or CCIE certifications.