New IT Certification exams, including those from Microsoft, are focusing less on knowledge-based questions and more on measuring skills that require hands-on experience with networking components.
This can be a problem for those going the home-study route. Even certification candidates in instructor-led classes may need more lab time than they get in class to master skills.
The ideal solution is to set up your own practice network at home, but buying several computers, cabling and other equipment can be costly. The solution is to create a virtual network using Microsoft Virtual PC or VMWare's WMWare Workstation software.
Benefits of using a virtual network
A virtual network consists of multiple virtual machines that run on a single physical computer (the host). Each virtual machine appears to be a separate computer on the network, with its own computer name and IP address.
Virtual machines provide flexibility
Virtual machines can run different operating systems and each ca be configured differently. For example, you can have three virtual machines, each running Server 2003, installed on a host computer that runs Windows XP. Each of the Server 2003 machines can be configured differently; one might be a domain controller, another might be a DNS server, and a third might act as an email server (with Exchange installed) or a firewall (with ISA Server installed).
Virtual machines protect your production network
Even if you have a complete network set up in your home, or have access to a network at work, it makes sense to do your exam preparation on a virtual network. Learning how to properly administer requires making all sorts of configuration changes that could cause trouble on your "real" network.
Virtual machines make it easy to start over
Another advantage of VM software is that you can create image files of an operating system installation and then, if your configuration changes cause problems, you can start with a clean OS by using the original image.
Some VM software even lets you take "snapshots" of the system at different points in time and then roll back to those points (similarly to Windows XP System Restore feature).
Choose the right VM software
The two major competitors in the desktop level virtual machine are:
Microsoft Virtual PC
VMWare Workstation
Note: Both Microsoft and VMWare also make enterprise versions of their software that can be used for server consolidation: Microsoft Virtual Server and VMWare Enterprise. However, the cost of these products is much greater than the desktop versions.
Either of these products will do the job. Each has advantages and disadvantages:
Microsoft Virtual PC costs less (list price $129 versus VMWare list price $199).
VMWare Workstation supports up to four network interfaces on a single virtual machine. Virtual PC supports only three.
Virtual PC has "snappier" graphic performance
VMWare Workstation allows you to exceed the amount of physical RAM in the computer when assigning RAM to virtual machines; VPC is limited to the physical RAM.
Virtual PC supports both Unicast and Multicast; VMWare doesn't support Unicast Network Load balancing (NLB).
VMWare makes it easier to take and manage "snapshots" in time of virtual machines.
Virtual PC will run the Windows Vista beta in a VM; VMWare will not.
VMWare supports Linux in a VM; VPC does not.
VMWare allows you to create video movies of a VM without extra software.
Create your virtual practice network
The first step in creating your virtual network is planning. You need to answer these questions:
How many virtual machines do you need on the network? You may be able to consolidate server roles; for example, one VM can serve as domain controller, DNS server and WINS server.
How much memory and disk space do you need to assign to each VM? Disk space can be allocated dynamically, so it uses only as much as is needed, but this slows performance.
How many network segments (subnets) do you need? For study purposes, typically, two to three will suffice.
Note: Both Microsoft and VMWare also make enterprise versions of their software that can be used for server consolidation: Microsoft Virtual Server and VMWare Enterprise. However, the cost of these products is much greater than the desktop versions.
If one of the VMs will be a firewall, how many network interfaces will it need? Regular server will generally have only one, but a firewall needs at least two.
Network Access
Another important consideration is whether you want the virtual machines to be able to access files on the host computer or the physical network. If not, you should disable drag-and-drop support (VPC) or virtual folders (VMWare).
If you want the virtual computers to connect to the internet, the best way is to have them go through an internet connection device, such as a VM set up as a Remote Access Services (RAS) server with two network interfaces. The external interface on the RAS server should be bridged to the physical network with its default gateway set to the IP address of the broadband router. The internal interface should be connected to the virtual network. The default gateway on the virtual clients should be set to the IP address of the RAS server's internal interface.
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