What we need:-

  • GNS3 - is a graphical network simulator that allows simulation of complex networks which included Dynamips, Dynagen, and Pemu (PIX Firewall emulator) project. Download here
  • Cisco IOS ROM - if you want to play with PIX, then you need that ROM image. If you like to use router also, then you have to have router ROM image too. Since this is belong to Cisco, Google is your friend, then download it.
  • Serial # of PIX if you want to use PIX firewall simulator. Again, Google is your best friend here.
  • Turn Windows Features on or offTelnet or SSH client
    • For Windows XP, you are likely to have telnet turn on by default
    • For Vista, telnet is disabled as a default, so go to Control Panel | Program and Features | Turn Windows on and off | check at Telnet Client the list, then click OK.

In order to use this simulator, you have to install GNS3 first. All you have to do is going through setup wizard which you don't have to tweak a thing.

GNS3 setup wizard GNS3 setup wizard

GNS3 setup wizard GNS3 setup wizard

GNS3 setup wizard

Then you have GNS3 in your start menu.

GNS3 start menu 

At this point, you will have set some options to let GNS3 know where IOS image is.


  • For PIX firewall, click edit menu | Preferences... | Pemu
    • then put image file, key, and serial in PIX image, Key, Serial key consecutively.

PIX image file

  • For Router, click edit menu | IOS images and hypervisors
    • put image files to Image file field, then save the image of the model you like to use.

Cisco IOS image files 

If you are at this point, you are good to go now. You can drag any device from left sidebar to create any topology you want.

PIX simulator

Figure above, I am simulating firewall for testing. You have to click start to be able to connect to the firewall (red dot changes to green indicating that Firewall is running)

PIX simulator - start

For setting, you can click Console to connect to firewall through telnet program.

PIX simulator -- telnet

All set.