1-5Configuring Loopback Detection for an Ethernet PortLoopback detection is used to monitor if loopback occurs on a switch port.After you enable loopback detection on Ethernet ports, the switch can monitor if external loopbackoccurs on them. If there is a loopback port found, the switch will put it under control.z If loopback is found on an access port, the system disables the port, sends a Trap message to theclient and removes the corresponding MAC forwarding entry.z If loopback is found on a trunk or hybrid port, the system sends a Trap message to the client. Whenthe loopback port control function is enabled on these ports, the system disables the port, sends aTrap message to the client and removes the corresponding MAC forwarding entry.Follow these steps to configure loopback detection for an Ethernet port:To do... Use the command... RemarksEnter system view system-view —Enable loopback detectionglobally loopback-detection enableRequiredBy default, loopback detectionis disabled globally.Set the interval for performingport loopback detectionloopback-detectioninterval-time timeOptionalThe default is 30 seconds.Enter Ethernet port view interface interface-typeinterface-number —Enable loopback detection on aspecified port loopback-detection enableRequiredBy default, port loopbackdetection is disabled.Enable loopback port control onthe trunk or hybrid portloopback-detection controlenableOptionalBy default, loopback portcontrol is not enabled.Configure the system to runloopback detection on allVLANs of the current trunk orhybrid portloopback-detection per-vlanenableOptionalBy default, the system runsloopback detection only on thedefault VLAN of the currenttrunk or hybrid port.z To enable loopback detection on a specific port, you must use the loopback-detection enablecommand in both system view and the specific port view.z After you use the undo loopback-detection enable command in system view, loopback detectionwill be disabled on all ports.z The commands of loopback detection feature cannot be configured with the commands of port linkaggregation at the same time.
