In my understand OTV data-group is used for the purpose of actual Multicast traffic forwarding if we have in our network. Which means my L2 multicast traffic for example will be encapsulated inside my Multicast address from SSM range I defined under Data-Group.
Now what I don't understand is that since not every customer may be running multicast in first place, why they made definining Data Group under overlay interface configuration as strict requirement in Multicast mode. Since once the remove the data-group command the VPN goes down.
Kidly correct me if I am having wrong assumption here.