Information Security and Assurance : (I.S.A)

GNS3 is a Graphical Network Simulator that allows emulation of
complex networks. You may be familiar with VMWare or Virtual PC
that are used to emulate various operating systems in a virtual
environment. These programs allow you to run operating systems
such as Windows XP Professional or Ubuntu Linux in a virtual
environment on your computer. GNS3 allows the same type of
emulation using Cisco Internetwork Operating Systems. It allows you
to run a Cisco IOS in a virtual environment on your computer. 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.