In an M580 Hot Standby configuration, some topologies may unintentionally create a loop that interferes with network communication. These topologies are essentially related to the management of flat networks, i.e., topologies in which the control network, remote I/O network, and/or the device network belong to the same subnet.

To help avoid creating an unintentional loop caused by connection to the service port, select the Automatic blocking of service port on Standby NOC check box that appears in the ServicePort tab of the configuration dialog. This check box is available only in Control Expert 14.0 or later.

No loop condition can exist on the Ethernet backplane connection by connecting one or more BMENOC0301.4 (or later) modules to the Ethernet backplane of an M580 Hot Standby configuration. A BMENOC0301.4 (or later) module automatically blocks its backplane port on the standby local rack.

To configure, select Services → Service Port in the BMENOC0301 Communication DTM.

Select the Automatic blocking of service port on Standby NOC check box so that the service port of the standby BMENOC0301.4 module is automatically blocked.

De-select the check box so that the service port is not automatically blocked.

The check box is deselected by default.

NOTE: These features are implemented in a Hot Standby system using a CPU with firmware version 2.7 or later and a BMENOC0301.4 or later module.