Configuring Layer 2 Ethernet Interfaces 95■ If loops are detected on a port that is of trunk or hybrid type, trap messages aresent to the terminal. If the loopback detection control function is also enabledon the port, the port will be blocked, trap messages will be sent to theterminal, and the corresponding MAC address forwarding entries will beremoved.Follow the following steps to configure loopback detection:c CAUTION:■ Loopback detection on a given port is enabled only after theloopback-detection enable command has been issued in both system viewand the interface view of the port.■ Loopback detection on all ports will be disabled after the issuing of the undoloopback-detection enable command under system view.■ For a Trunk or Hybrid port, make sure that the default VLAN of the port exists.Configuring the CableType for an EthernetInterfacen ■ The optical interface of a Combo port does not support this feature.■ After you perform the configuration described in this section, the link goesdown and up automatically.Two types of Ethernet cables can be used to connect Ethernet devices: crossovercable and straight-through cable. To accommodate these two types of cables, anEthernet interface on a device can operate in one of the following three MediumDependent Interface (MDI) modes:To do... Use the command... RemarksEnter system view system-view -Enable global loopbackdetectionloopback-detection enable RequiredDisabled by defaultConfigure the interval for portloopback detectionloopback-detectioninterval-time timeOptional30 seconds by defaultEnter Ethernet interface view interface interface-typeinterface-number-Enable loopback detection ona portloopback-detection enable RequiredDisabled by defaultEnable loopback detectioncontrol on a Trunk port or aHybrid portloopback-detection controlenableOptionalDisabled by defaultEnable loopback detection inall the VLANs containing theportloopback-detectionper-vlan enableOptionalEnabled only in the defaultVLAN(s) with Trunk port orHybrid portsDisplay the information aboutloopback detectiondisplay loopback-detection OptionalThis command can beexecuted in any view.
