I had the weirdest thing happen the other day. I created a VM and migrated it to second host. I created a new VM, and had trouble accessing the first VM. What gives! Well, I ran into a MAC address duplication issue.
To avoid this, first configure your Hosts and VM’s to use Logical Switches. Once configured, set all of your VM’s to the static MAC address of ’00:00:00:00:00:00′ using SCVMM console. Once you hit ‘Apply’ and ‘OK’ to close the properties window, SCVMM will give the VM a new MAC address from the MAC address pool. No more duplicates!
For the Logical Switch configuration, see my post ‘SCVMM 2012 R2 – Logical Switches‘.