z If you have not enabled the loopback port auto-shutdown function on the port, the port willautomatically resume the normal forwarding state after the loop is removed.2) If a loop is found on a trunk or hybrid port, the system sends log and trap messages to the terminal.If you have additionally enabled the loopback port control function or the loopback portauto-shutdown function, the system will deal with the port accordingly:z If the loopback port control function is enabled on the port, the system will set the port to the blockstate (ports in this state cannot forward data packets), send log and trap messages to the terminal,and remove the corresponding MAC forwarding entry. After the loop is removed, the port willautomatically resume the normal forwarding state.z If the loopback port auto-shutdown function is enabled on the port, the system will shut down theport and send log and trap messages to the terminal. After the loop is removed, you need to use theundo shutdown command to bring up the port.You cannot enable both the loopback port control function and the loopback port auto-shutdownfunction on a port. If you do so, the function configured later will take effect.Table 12-1 Configure loopback detection for Ethernet port(s)Operation Command RemarksEnter system view system-view —Enable loopbackdetection globally loopback-detection enableOptionalBy default, the global loopbackdetection function is enabled if thedevice boots with the defaultconfiguration file (config.def); if thedevice boots with null configuration,this function is disabled.Enable loopbackdetection on thespecified ports in bulkloopback-detectioninterface-list enableOptionalBy default, the loopback detectionfunction is enabled on ports if thedevice boots with the defaultconfiguration file (config.def); if thedevice boots with null configuration,this function is disabled.Set the interval forperforming port loopbackdetectionloopback-detectioninterval-time timeOptionalThe default is 30 seconds.Enter Ethernet port view interface interface-typeinterface-number —Enable loopbackdetection on a specifiedportloopback-detection enableOptionalBy default, the loopback detectionfunction is enabled on ports if thedevice boots with the defaultconfiguration file (config.def); if thedevice boots with null configuration,this function is disabled.12-6
