All nodes in an Oracle RAC environment must connect to at least one Local Area Network (LAN) (commonly referred to as the public network) to enable users and applications to access the database. In addition to the public network, Oracle RAC requires private network connectivity used exclusively for communication between the nodes and database instances running on those nodes. This network is commonly referred to as the interconnect.
The interconnect network is a private network that connects all of the servers in the cluster. The interconnect network must use at least one switch and a Gigabit Ethernet adapter.
Oracle supports interfaces with higher bandwidth but does not support using crossover cables with the interconnect.
Do not use the interconnect (the private network) for user communication, because Cache Fusion uses the interconnect for interinstance communication.
You must configure User Datagram Protocol (UDP) for the cluster interconnect, except in a Windows cluster. Windows clusters use the TCP protocol. On Linux and UNIX systems, you can configure Oracle RAC to use either the UDP or Reliable Data Socket (RDS) protocols for inter-instance communication on the interconnect. Oracle Clusterware uses the same interconnect using the UDP protocol, but cannot be configured to use RDS.
An additional network connectivity is required when using Network Attached Storage (NAS). Network attached storage can be typical NAS devices, such as NFS filers, or can be storage that is connected using Fibre Channel over IP, for example. This additional network communication channel should be independent of the other communication channels used by Oracle RAC (the public and private network communication). If the storage network communication must be converged with one of the other network communication channels, then you must ensure that storage-related communication gets first priority.