Compaq ProLiant CL380 Increasing Availability of Cluster Communications in a W - Page 23

The Windows NT operating system views the controller pair as a single controller. In a controller pair, if a primary network controller fails, the Media Access Control (MAC) address of the primary controller transfers to the secondary controller. At that time, the driver switches the MAC address from the primary controller to the secondary controller. The MAC address is a unique address assigned to a particular network controller. The MAC address identifies that network controller on the network. The secondary controller automatically switches to the active controller and takes control of the traffic on the network. The entire process occurs without the intervention of network protocols or operating system applications. Creating a controller pair with the Advanced Network Control Utility is easy, and you can immediately view the results in the utility. A controller pair consists of two Compaq NetFlex-3 or Netelligent Controllers. The paired controller configuration provides connectivity over the network so that the network maintains operation even if a controller connection is lost or if one of the controllers fails. Although a controller pair configuration is installed and monitored with one instance of the NetFlex-3 driver, the driver is always aware that there are two physical controllers. One controller is active and the other non-active controller is a backup (standby). The NetFlex-3 driver controls both controllers and can automatically switch traffic if one controller fails. The operating system views the controller pair as a single controller and the switch over from one physical controller to the other is completely transparent to the operating system and any application programs. Each controller pair consists of a primary and a secondary physical controller. Only one of these controllers can be active at a time. When the system starts up, the driver tries to direct network traffic over to the primary controller, so the primary controller is usually the controller. Should the primary controller fail or lose connection, the secondary or controller can become active depending on the operating mode of the controller pair.