dynamips

Dynamips (DM) is virtualization software that runs the Cisco router operating system - the real Cisco IOS software. In order to have a router lab pod, Dynamips (DM) can be installed and an IOS image copied to the same computer. Dynamips (DM) can be configured by defining a topology. Dynamips runs on FreeBSD, 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. It uses two other related free packages: Dynagen and GNS3 (an optional graphical front-end).