1-51) If a loop is found on an access port, the system will set the port to the block state (ports in this statecannot forward data packets), send log and trap messages to the terminal, and remove thecorresponding MAC forwarding entry.z If you have additionally enabled the loopback port auto-shutdown function on the port, the systemwill shut down the port, and send log and trap messages to the terminal. After the loop is removed,you need to use the undo shutdown command to bring up the port.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 1-1 Configure loopback detection for Ethernet port(s)Operation Command RemarksEnter system view system-view —Enable loopback detectionglobally loopback-detection enableRequiredBy default, loopback detection is disabledglobally.Enable loopback detectionon the specified ports inbulkloopback-detectioninterface-list enableOptionalBy default, loopback port control is notenabled.Set the interval forperforming port loopbackdetectionloopback-detectioninterval-time timeOptionalThe default is 30 seconds.Enter Ethernet port view interface interface-typeinterface-number —Enable loopback detectionon a specified port loopback-detection enableOptionalBy default, loopback port control is notenabled.
