In your class, (or even if you're studying this course at home) you may not have all the machines listed in this sample network layout. don't worry. Neither did I. You see, getting something listed in the DNS does not necessarily mean the machine has to be present physically, since DNS is merely a service that will translate IP addresses to names or visa versa.
There are many domains on the Internet that have been reserved, but are currently not in use. In this module, we're going to create a fictitious domain, and while we're about it, we'll create a couple of fictitious machines too. The minimum number of machines you will need to get this course to work is 2, which is the minimum required in the course specification.
Figure 2.1 below illustrates the proposed configuration of our sample network. You should see that some of the hosts are multi-homed. Multihomed hosts are those that are connected to two networks simultaneously.