Dynamips is a software that emulates Cisco IOS on a traditional PC.

It was created by Christophe Fillot who started his work in August 2005.

The last official release of Dynamips supports Cisco 7200, 3600 series
(3620, 3640 and 3660), 3700 series (3725, 3745), 2600 series (2610 to
2650XM, 2691) and 1700 series. Please note that you must provide your
own IOS images compatible with the Cisco hardware emulated by Dynamips.

GNS3 is based on Dynamips and Dynagen (a text-based front-end for
Dynamips) to create a complete virtual Cisco network, adding many
additional features and most importantly making it easy to create,
change and save your network topologies.

Unfortunately, Dynamips is no longer officially maintained, this is why
we have chosen to make -- with the precious help of contributors --
an unofficial version of Dynamips called dynamips-community that brings
many improvements. We encourage contributions and the code repository
is accessible on GitHub.