P     er http://www.yellow-bricks.com/2014/03/31/vsan-misconfiguration-detected-2/     :

Here are your two options:

• Enable IGMP Snooping for your VSAN network (VLAN) and define an IGMP Snooping Querier. Default setting on most Cisco switches is IGMP Snooping enabled but without an IGMP Snooping Querier. In this configuration VSAN will not be able to configure correctly!
• Disable IGMP Snooping for your VSAN network (VLAN). Please note that you can typically disable IGMP Snooping globally and per VLAN, in this case if you want to disable it… disable it on your VLAN!