My aim is to use gns3 http://www.gns3.net/ as a platform for my virtual network lab. gns3 is a well known graphical tool for network simulations where users are able to put their own ios files to simulate a fairly large numer of network devices. Cisco’s Packet Tracer can also be used but Packet Tracer is not as Professional as gns3. So lets start with obtaining gns3. At http://packages.debian.org/wheezy/gns3 we see that gns3 is flaged to be “contrib” and one of its dependent packages dynamips is flagged as “non-free” so in order to obtain gns3 from packet manager tool apt-get, we should enable contrib and non-free components at /etc/apt/sources.list. Open this file to add following lines to repositories,


then run
apt-get update
In order to update packet manager. Then installing gns3 should be simple as;
apt-get -f install gns3
Let’s start gns3
First thing is to configure and test dynamips which should be done from “Edit”>”Preferences”>”Dynamips” sections and specifying path for dynamips. Test should result with saying similar to “dynamips successfully started”


Next step is updating gns3 ios repository with our Cisco ios. This may be done with “Edit”>”IOS images and hypervisors” section and locating desired ios files. Unfortunately cisco ios aren’t open, but it shouldn’t be too hard to Google. Successful update should populate section of “images” of the figure below;


Next step will be putting some network elements to gns3…