1. First we will install Dynagen and Python-Qt4

sudo apt-get install dynagen python-qt4

2. Download GNS3 and extract in /opt

cd /opt
sudo wget http://space.dl.sourceforge.net/project/gns-3/GNS3/0.7.2/GNS3-0.7.2-src.ta r.bz2
sudo tar -xjvf GNS3-0.7.2-src.tar.bz2 && rm GNS3-0.7.2-src.tar.bz2
sudo mv GNS3-0.7.2-src /opt/GNS3

3. Create the following directories:
These directories will be used by GNS3 – such as projects – where your working projects will be stored, cache, temp, IOS images, etc.

cd /opt/GNS3
sudo mkdir Dynamips
sudo mkdir IOS
sudo mkdir Project
sudo mkdir Cache
sudo mkdir tmp
sudo chmod o+rw -R ./Project
sudo chmod o+rw -R ./tmp

4. Download binary of dynamips and make it executable

cd Dynamips
sudo wget http://www.ipflow.utc.fr/dynamips/dynamips-0.2.8-RC2-x86.bin
sudo chmod +x ./dynamips-0.2.8-RC2-x86.bin

You can create a desktop shortcut by right-clicking on the desktop and select “Create Launcher..”, Name it GNS3 and in the command section type in

python "/opt/GNS3/gns3"

Double click to open GNS3 and we will edit the default settings. If you don’t want to use desktop icons you can create a launcher from your programs menu by right clicking on the Main Menu, selecting Edit Menu. Select New Item on the right and you will be presented with the same window where you type in the above. From there you can move the launcher into any menu section of your choice.

5. Go to edit | preferences and in the ‘Terminal command:’ section type in:

gnome-terminal -t %d -e 'telnet %h %p' > /dev/null 2>&1 &

6. Under ‘Paths’ change the ‘Project directory:’ to

/opt/GNS3/Project

and the ‘IOS/PIX directory:’ to

/opt/GNS3/IOS

7. Click on Dynamips tab on the left 

For the ‘Executable path:’ type in

/opt/GNS3/Dynamips/dynamips-0.2.8-RC2-x86.bin

8. Change the ‘Working directory:’ to

/opt/GNS3/tmp

Click on the Capture tab on the left

9. For the ‘Working directory for capture files:’ change it to

/opt/GNS3/Project 

10. Click on Qemu tab on the left 

Path to Qemuwrapper:

/opt/GNS3/qemuwrapper/qemuwrapper.py

Working Directory:

/opt/GNS3/tmp