Just found a good article about this topic. I'm a rookie and never attended to any traning class before, so this article help me understand more about the Virtual Network on Windows Server 2008 Hyper-V.
For the beginners, you might need to learn about Microsoft's Hypervision (or Hyper-V) feature first. It's all about virtualization on the server platform. Microsoft has rewriten this application from the scratch and making it to be the replacement of its old Virtual PC/Server technology.
It's cool. If you've never heard about it, learn it now!!