GNS3 for Beginners

GNS3 is an an open source emulation program for anyone who want to pursue a career on Cisco Routing. It's build on dynagen and dynamips foundation.

I've provided you simple steps on how a topology works on GNS3:

1. Download GNS3 from http://www.gns3.net/download.
2. Install GNS3.
3. Run the program and click option 1 on Setup Wizard. "Configure and test the path to Dynamips. Also check that the working directory is valid". If you exit the Set up wizard, go to Edit | Preferences.
4. Select a Project Directory. This is the path where your projects are saved.
5. Select an Image directory. This is the path where IOS images are stored.
6. Select Dynamips and click Test button. This will return a Dynamips "successfully started" message if Dynamips is running.
7. Select option 2. Add one or more uncompressed IOS images.
8. You have to take note of this: The IOS image in BIN format are compressed. You can load IOS image UNPACKED file for faster booting.
9. Drag and drop devices (with IOS image) to build a topology.
10. Add router modules (Double click the image, select the device and add slot/s on Slots Tab).
11. Cable the connections ( Click add a link button on GNS3's toolbar and select type of cable).
12. Power the devices by clicking the play button on GNS3's toolbar.

Some helpful tips:

Use the Idle PC feature to lessen the CPU usage of dynamips when the device is idle. To do this:
Right click the device, select idle PC, select the best idlepc values and select ok.

You can use wireshark captures to check packet data. To do this:
Right Click on the link between two devices, select Capture, then select a source. Go to Edit | Preferences | Capture and modify the settings to make this one work.