I am playing with ONTAP Simulator 8.1.1 & Windows Server 2012.
All the settings on the NetApp side were default, so SMB2 was enabled. Every attempt to access a CIFS share from w2k12 led to the server reboot. I now disabled SMB2 (options cifs.smb2.enable off) & everything works like a charm.
Is it something specific to simulator maybe, or does w2k12 'dislike' SMB2 on ONTAP (8.1.1)?