If you do not plan to use the autodiscover method due to multicast restrictions, and will use the manual method instead for selecting nodes for the cluster build operation, you can skip this task.
VxRail clusters have no backplane, so communication between its nodes is facilitated through the network switch. This communication between the nodes for device discovery purposes uses VMware Loudmouth capabilities, which are based on the RFC-recognized Zero Network Configuration protocol. New VxRail nodes advertise themselves on the network using the VMware Loudmouth service, and are discovered by VxRail Manager with the VMware Loudmouth service.
VMware Loudmouth service depends on multicasting, which is required for the VxRail internal management network. The network switch ports that connect to VxRail nodes must allow for pass-through of multicast traffic on the VxRail Internal Management VLAN. Multicast is not required on your entire network, only on the ports connected to VxRail nodes.
VxRail creates little traffic through multicasting for autodiscovery and device management. Furthermore, the network traffic for the Internal Management network is restricted through a VLAN. You can enable MLD Snooping and MLD Querier on the VLAN if supported on your switches.