Here is a very nice blog post from the Microsoft Enterprise Networking Team. In this post they spend a good deal of time discussing how Windows and various versions of Windows work at Layer 2, which is the Data Link layer.
Understanding what’s happening on the wire at the Data Link layer is probably one area where Windows networking admins pay the least attention. This is unfortunate, because if you understand what’s happening here, you can solve a lot of problems that are misattributed to the ISA or TMG firewall.
Check out this discussion at:
Thomas W Shinder, M.D., MCSE
Sr. Consultant / Technical Writer