If you have Cisco Nexus 1000v distributed virtual switch in your VMware virtual environment and you have virtual machines (VMs) running Microsoft NLB (Network Load Balancing) in IGMP multicast mode, then you will need to disable IGMP snooping on N1KV to allow multicast traffic to pass through on the VLAN for those NLB VMs. By default IGMP snooping is enabled on all VLANs in Cisco Nexus 1000v, which is a good thing.
Here is the command to disable IGMP snooping on N1KV on let's say VLAN 100.
N1KV84(config-vlan)# no ip igmp snooping
N1KV84(config-vlan)#copy run start
Note: Nexus 1000v doesn't support MS NLB in Unicast mode.