A cluster comprises of machines or nodes connected to each other. The Cluster software monitors the processes and services running on each Node. The Node that runs a process or service is called the Active Node. The Passive Nodes do not simultaneously run the same process or service. If a Node unexpectedly fails or is intentionally taken down, the Cluster software ensures that the clustered processes and services from the failed Node are switched to another machine in the cluster, where they can restart and continue. This process is referred to as a failover.