GNS3 is a Graphical Network Simulator that allows emulation of complex networks like VMWare or Virtual PC .

GNS3 allows the emulation of  Cisco Internetwork Operating Systems(IOS).GNS3 is a graphical front end to a product called Dynagen. Dynamips is the core program that allows IOS emulation. Dynagen runs on top of Dynamips to create a more user friendly, text-based environment. A user may create network topologies using simple Windows ini-type files with Dynagen running on top of Dynamips. GNS3 takes this a step further by providing a graphical environment.

Core Programe      Text Based environment        Graphical environment.

Dynamips ————> Dynagen—————–>GNS3

Features:

  • GNS3 is an open source, free program for you to use
  • GNS3 allows the emulation of Cisco IOSs on your Windows as well as Linux based computer
  • Support a long list of router platforms and PIX firewalls
  • Using an EtherSwitch card in a router, switching platforms may also be emulated to the degree of the card’s supported functionality
  • GNS3 is an invaluable tool for preparing for Cisco certifications such as CCNA and CCNP.
  • As compare to the other router simulators in the market , GNS3 runs an actual Cisco IOS, so you will see exactly what the IOS produces and will have access to any command or parameter supported by the IOS, on the other hand router simulators in the market depends upon the developers accuracy of that representation
  • GNS3 will provide around 1,000 packets per second as compare to  a real router will provide a hundred to a thousand times greater throughput