The SNMP notification that is generated when a module's operational state changes. The management entity receiving the notification can identify the module and the event by referencing snChasUnitIndex, snAgentBrdIndex, snAgentBrdModuleStatus. In case of a module-down event, the varbind snAgGblTrapMessage is a text string that describes the cause. In case of module-up event, snAgGblTrapMessage is a null string.