This is the topology that I am using.

First of all we need to have a switch. I have a Cisco Catalyst 3560 that I'll use for my
demonstration.

Secondly we'll need one of those Cisco console cables or we can't connect our computer to the switch.

If you don't have a COM / serial port on your computer or laptop, use your USB to serial cable.

The last thing you require is an application to connect to your serial port.

Putty is a good free application to start with, you can download it here:

http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html

When you start putty it looks like this.

Make sure you select serial and type in the correct COM port number.

If you don't know the COM port number you can look it up in the windows device manager.

You need to leave speed at 9600. Click on open and you will have access to your switch.

As soon as you power on the switch this is what it will do:
1. Check the hardware.
2. Locate the Cisco IOS image.
3. Locate and apply configuration (if available).

This is what it looks like on a real switch: Above you see that it‟s checking the flash drive of the switch. Next step is to load the IOS image that it found on the flash drive.

IOS images are stored on the flash drive in a compress format, it will be uncompressed and copied to the RAM of the switch.

Now IOS is loaded you will see something like this, you see this banner and the IOS version that I‟m running. This is a Cisco 3560 switch.

IOS will check the flash drive.

And once it's done it will do a POST (Power On Self-Test):

Once the POST is done we'll get a final warning:

And finally you'll see an overview of the hardware that this switch offers.

Once the switch is done you finally get to see this message:

Press RETURN to get started!

If the switch does not have a configuration, you'll see the following:

—- System Configuration Dialog —-
Would you like to enter the initial configuration dialog? [yes/no]:

If you type yes and press enter it will walk you through a wizard where you can configure some basic settings.

I'm going to skip it since we'll configure everything ourselves.

Right now you are in user mode.