Linux On My PC: Preparing For RHCE? Create Your Own Classroom Network (Virtual) At Home.

I regretted not having looked into virtualization seriously enough while attending classes to get my RHCE certification. It's an invaluable tool to experiment and learn different Operating Systems without messing around with your Computer hardware.

Without wasting any time download Sun xVM VirtualBox for Windows:
http://www.sun.com
http://www.sun.com/software/products/virtualbox/get.jsp
http://www.virtualbox.org

You should go through the bundled User manual (pdf) if you are unable to find your way to install RHEL. It's quite straightforward and simple if you spend some time on it.

After installing RHEL( or any other linux distro) to have multiple guest Operating Systems running you can quickly clone your previous installation to create as many virtual disk images as you like.

1. Open a command console: Start-> Run-> cmd

2. Enter: cd C:\Program Files\Sun\xVM VirtualBox

3. Execute the following command where the file name is the vdi(virtual HDD) file you created when you installed RHEL, by default inside:
C:\Documents and Settings\username\.VirtualBox\VDI\

vboxmanage clonevdi filename output_filename

Note: You can do the rest in the VirtualBox application window (GUI).

4. Enable SATA controller even if you have an IDE HDD and subsequently make sure to enable SATA for all cloned vdi images.

5. Connect the Network cards to Internal Network and use one Network Name for all clones you want to interconnect.

6. After booting up each virtual machine you will have to set the network configuration manually.

system-config-network

Note: Set the gateway to 0.0.0.0 for all virtual machines.

The number of virtual machines you can possibly run at ones is limited mostly by the hardware you have got.
Also checkout Microsoft Virtual Server 2005 R2: Virtual DHCP, configurable system resource allocation etc.
Supports only RHEL 5.0 and SUSE linux distributions.
http://www.microsoft.com/windowsserversystem/virtualserver/

Running Concurrently