The VxRail product has two separate and distinct management networks. One management network extends externally to connect to IT administration and external data center services. The second management network is isolated, visible only to the VxRail nodes.
The network that is visible only to the VxRail nodes depends on IPv6 multicasting services configured on the adjacent ‘top-of-rack’ switches for node discovery purposes. One node is automatically designated as the primary node. It acts as the source, and listens for packets from the other nodes using multicast. A VLAN assignment on this network limits the multicast traffic only to the interfaces connected to this internal management network.
A common Ethernet switch feature, Multicast Listener Discovery (MLD) snooping and querier is designed to further constrain the flooding of multicast traffic by examining MLD messages, and then forwarding multicast traffic only to interested interfaces. Since the traffic on this node discovery network is already constrained through the configuration of this VLAN on the ports supporting the VxRail cluster, this setting may provide some incremental efficiency benefits, but does not negatively impact network efficiency.
If your data center networking policy has restrictions for the IPV6 multicast protocol, IP addresses can be manually assigned to the VxRail nodes as an alternative to automatic discovery.