vSAN requires that IP multicast be enabled on the physical switches and routers that handle vSAN traffic along the Layer 2 path, and optionally the Layer 3 path. It is utilized for intra-cluster communication, specifically for heartbeats and exchange of metadata between the ESXi hosts participating in the cluster. Multicast traffic can be limited to specific port groups by using IGMP (v3) snooping. This is considered a best practice. VMware recommends not implementing multicast flooding across all ports, rather enabling multicast only on the segments or ports that are being used for vSAN.

By default, multicast communication is not configured on most hardware switches. As a result, there is no IGMP snooper setup, and therefore traffic is not passed. To be sure that multicast traffic is passed, make sure to configure the IGMP snooper so traffic can be passed, or explicitly disable IGMP snooping on the port.