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, the remote I/O network, and/or the device network belong to the same subnet.

To help avoid creating an unintentional loop caused by the connection to the service port, use the automatic blocking of service port feature on the CPU with firmware version 2.7 (or later) or a BMENOC0301.4 (or later) module.

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.

This function is available only in Control Expert 14.0 or later.