Dynamips

Dynamips is an emulator program that was written to emulate Cisco routers. Dynamips runs on Linux , Mac OS X or Windows and can emulate the hardware of the Cisco series routing platforms by directly booting an actual Cisco IOS software image into the emulator.

Dynamips development has stalled since version 0.2.8-RC2, released in October 2007. There are a few add-ons written for it. One of the most popular is Dynagen, which is a front-end add-on that allows the use of an INI configuration file to provision Dynamips emulator networks. Other popular add-on is GNS3, which is graphical front end for Dynamips and Dynagen. The source code is licensed under the GNU GPL.