NLB on a Hyper-V host

Just a quick gotcha I came up against when I was trying to set up a CAS array on my Exchange 2010 boxes. I kept getting errors when trying to set up a unicast NLB cluster, and the nodes wouldn’t converge.

I ended up figuring out that I had to enable MAC address spoofing on the virtual NICs. The cluster needs to assign the same MAC to both cluster NICs, and this isn’t possible without having that checkbox ticked. This feature is only available in Hyper-V since Server 2008 R2 was released.

I was going to write a more detailed article about it, but as usual, Paul Cunningham’s great blog has it covered already in detail with screenshots.