1-8To do… Use the command… RemarksEnable loopback detection on aport loopback-detection enable RequiredDisabled by defaultEnable loopback detectioncontrol on a trunk port or ahybrid portloopback-detection controlenableOptionalDisabled by defaultEnable loopback detection in allthe VLANs to which trunk orhybrid ports belongloopback-detection per-vlanenableOptionalEnabled only in the defaultVLAN(s) with trunk port orhybrid portsz Loopback detection on a given port is enabled only after the loopback-detection enablecommand has been configured in both system view and the interface view of the port.z Loopback detection on all ports will be disabled after the configuration of the undoloopback-detection enable command under system view.Configuring the MDI Mode for an Ethernet Interface10-Gigabit Ethernet ports and combo ports operating as optical interfaces do not support this function.Two types of Ethernet cables can be used to connect Ethernet devices: crossover cable andstraight-through cable. To accommodate these two types of cables, an Ethernet interface on a devicecan operate in one of the following three Medium Dependent Interface (MDI) modes:z Across modez Normal modez Auto modeAn Ethernet interface is composed of eight pins. By default, each pin has its particular role. For example,pin 1 and pin 2 are used for transmitting signals; pin 3 and pin 6 are used for receiving signals. You canchange the pin roles through setting the MDI mode. For an Ethernet interface in normal mode, the pinroles are not changed. For an Ethernet interface in across mode, pin 1 and pin 2 are used for receivingsignals; pin 3 and pin 6 are used for transmitting signals. To enable normal communication, you shouldconnect the local transmit pins to the remote receive pins. Therefore, you should configure the MDImode depending on the cable types.z Normally, the auto mode is recommended. The other two modes are useful only when the devicecannot determine the cable type.z When straight-through cables are used, the local MDI mode must be different from the remote MDImode.
