The VMware vSphere High Availability feature is configured by default when the VxRail cluster is built.
The VMware vSphere agents on each node monitor the state of the VxRail cluster using heartbeat signals on the VxRail external management network. If a node in question believes it has become separated by network from the rest of the cluster, it can perform an additional heartbeat check to the isolation IP addresses to confirm the problem.
The isolation IP addresses can be configured as part of the automated VxRail initial build process, or configured after the cluster is built. A minimum of two IP addresses reachable from the VxRail external management network should be selected for this purpose.