Our Virtual Switch got smarter in Windows Server 2008 R2. In Windows Server 2008, VMs are susceptible to MAC spoofing. MAC spoofing is where a (generally) malicious machine pretends to be another machine on a network (there are legitimate applications which do spoof MAC addresses though – Network Load Balancing being one such example).
A MAC (Media Access Control) address in physical NICs is burnt in, although it can usually be over-ridden. In a virtual machine environment, there’s no physical counterpart, so we have to “make up†our own addresses. In fact, that can sometimes cause other networking issues which I talked about last year.
Full Article – http://blogs.technet.com/jhoward/archive/2009/05/21/new-in-hyper-v-windows-server-2008-r2-part-2-mac-spoofing.aspx
