1-9
z Loopback detection on a given port is enabled only after the loopback-detection enable
command 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 undo
loopback-detection enable command under system view.
Configuring the MDI Mode for an Ethernet Interface
10-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 and
straight-through cable. To accommodate these two types of cables, an Ethernet interface on a device
can operate in one of the following three Medium Dependent Interface (MDI) modes:
z Across mode
z Normal mode
z Auto mode
An 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 can
change the pin roles through setting the MDI mode. For an Ethernet interface in normal mode, the pin
roles are not changed. For an Ethernet interface in across mode, pin 1 and pin 2 are used for receiving
signals; pin 3 and pin 6 are used for transmitting signals. To enable normal communication, you should
connect the local transmit pins to the remote receive pins. Therefore, you should configure the MDI
mode depending on the cable types.
z Normally, the auto mode is recommended. The other two modes are useful only when the device
cannot determine the cable type.
z When straight-through cables are used, the local MDI mode must be different from the remote MDI
mode.
z When crossover cables are used, the local MDI mode must be the same as the remote MDI mode,
or the MDI mode of at least one end must be set to auto.
Follow these steps to configure the MDI mode for an Ethernet interface:
To do… Use the command… Remarks
Enter system view
system-view
—
Enter Ethernet interface view
interface interface-type
interface-number
—
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