GNS3 (Open Source)

GSN3, or Graphical Network Simulator, is a program used for simulating different complicated networks. The program is similar to a virtualization software package, which is used for emulating different operating systems (i.e. Windows, Ubuntu, Mac) in a virtual environment on the computer. The only difference is that in GSN3, users emulate Cisco Internetwork Operating Systems allowing users to run the Cisco IOS  in a virtual environment on the computer. The application is linked to Dynamips, Dynagen, Qemu, and VirtualBox to attain accurate simulation of Cisco IOS.

The following are some uses of GSN3:

• Certification Study – The program can be used by administrators, network engineers, or anyone interested in studying different certifications such as Cisco CCIP, CCNP, CCIE, and CCNA.
• Configuration Testing – GSN3 can also be used for checking and testing configurations of the Cisco IOS and Juniper JunOS before deploying them on real routers.
• Vendor Certifications Checking – Because of the program’s integration with VirtualBox, it can also be used for studying Microsoft (MSCA/MSCE), Redhat (RHCT/RHCE), Novell (CLP), and other vendor certifications.

GSN3 utilizes the Scalable Vector Graphics (SVG) technology allowing users to obtain high quality symbols when creating network topologies. It also includes a built-in Frame Relay switch, which can be used for making a frame relay map between the source and destination.