VDL2 IP interface on vmknic failed to join multicast group.
The related VXLAN IP interface cannot join the multicast group. Causes can include number of VXLAN multicast groups exceeds the limit of 512.
Assuming that system resources are present, and the maximum number of groups has not been exceeded, then there is no specific solution. It is advised to contact VMware Support.
More details can be found in the VMware KB article VXLAN multicast groups configuration fails.
Refer to the VMware Online Documentation for more information on vCenter event messages and possible solutions.