The other day I was trying to boot a virtual machine over the network using my Windows Deployment Services (WDS) Server. This normally works fine – but for some reason I was getting nothing but errors. Sometimes I would get a DHCP failure, other times I received varied PXE error messages:
After some investigation I stumbled on to the problem. There was a MAC address conflict. While Hyper-V will not let MAC address conflicts happen on a single server – but you can still have conflicts happen between multiple Hyper-V servers. John Howard has talked about this extensively here: http://blogs.technet.com/b/jhoward/archive/2008/07/15/hyper-v-mac-address-allocation-and-apparent-network-issues-mac-collisions-can-cause.aspx
Once I realized what was happening – I quickly changed the virtual machine to use a static MAC address and set the MAC address to a unique value:
Then network installation worked fine.