A cluster consists of one or more servers. The hardware in a server in a cluster (or cluster member or node) is similar to a standalone server. However, a server that is part of a cluster, otherwise known as a node or a cluster member, requires a second network. This second network is referred to as the interconnect. For this reason, cluster member nodes require at least two network interface cards: one for a public network and one for a private network. The interconnect network is a private network using a switch (or multiple switches) that only the nodes in the cluster can access.Foot 1
Oracle does not support using crossover cables as Oracle Clusterware interconnects.
Cluster size is determined by the requirements of the workload running on the cluster and the number of nodes that you have configured in the cluster. If you are implementing a cluster for high availability, then configure redundancy for all of the components of the infrastructure as follows:
At least two network interfaces for the public network, bonded to provide one address
At least two network interfaces for the private interconnect network