I'm going to be testing some software, MDT 2010 and Configuration Manager. I would like to create a virtual test environment. The Host box will be running Server 2008 R2 and the clients will be Hyper V boxes. The host will be the Domain Controller for the environment and what I'm looking to do is have one nic be the "WAN" and a virtual nic be "LAN". Is this possible, and if so, how can i set this up? Also should a Quad Core 3.0 ghz with 4gb of memory be enough resources for 2 2008 r2 boxes and 2 win 7 boxes. I have another machine a dual core 2.0 ghz with 2gb of memory, if needed.
Yes, this is doable. In Hyper-V virtual network manager you create a new virtual network, using the the virtual NIC. You'll probably want it to be External, the guests can hit the internet (if that's desired), with the radio checked for "Allow management operating system to share this network adapter."
That CPU should be good, RAM might be a little light, depending on what you're actually going to be testing on the guests - stands to reason, right? If you're going to be testing Photoshop or a render farm, then nope.
You haven't said anything about disk layout (spindle count), IO profile, etc - so that may also be a concern for performance. Again, without knowing what your real needs and expected uses are, how can we hope to tell you if you have "enough"?
/Re-reading, that you're going to be testing MDT and SCCM. I have no idea about the latter, although I'm sure it depends on SQL, which may be a concern? For the former, if you're going to be testing backup throughput, then you're definitely going to have to care about IO a lot. If you're only testing configurations and testing small jobs, you're probably OK.