This persistent variable controls whether the Agent will attempt to sent a trap the MIB II 'linkUp' trap whenever the Network Management Unit, or NMU, detects a link interface with a 'up' status. The 'linkUp' trap is defined in RFC 1215, but offers no control for enabling or disabling. This MIB represents an extension to this definition for the purpose of allowing all traps to be selectively enabled or disabled. This linkUp trap has a single variable bindings of 'ifIndex', which identifies the index number of the interface in the 'up' state. 'enabled' allows the SNMP Agent to attempt to send the linkUp trap, provided the other checks describe below do not prohibit this trap from transmission. 'disabled' disallows the SNMP Agent from attempting to send the linkUp trap, thus 'filtering' this trap from transmission'. In this case, 'trapFilteredSpecific' will be incremented. This MIB variable is the first of four checks that the NMU Agent uses to filter traps, based upon 1) a specific enable or disable control variable; 2) 'trapControl' which offers a gross on/off/limit control; 3) 'trapMgrTable' with 'trapMgrControl' and 'trapMgrAddress' which filters whether standard traps (such as this linkUp) and/or enterprise traps are sent to each specific trap manager; and 4) 'trapSeverityFilter' which filters traps according to a controlling severity level (In the case of linkUp, there is no associated severity level, so this final filter does not apply). Whenever any of these trap filters cause a trap to be filtered, the corresponding MIB statistic is incremented. These statistics are 'trapFilteredSpecific', 'trapFilteredControl', 'trapFilteredManager', and 'trapFilteredSeverity' . See the MIB descriptions for any of these above variables for details.