Configuring The Mdi Mode For An Ethernet Interface - 3Com 4510G Configuration Manual

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.
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 optical interfaces of SFP ports 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:
Across mode
Normal mode
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.
Normally, the auto mode is recommended. The other two modes are useful only when the device
cannot determine the cable type.
When straight-through cables are used, the local MDI mode must be different from the remote
MDI mode.
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...
Enter system view
Enter Ethernet interface view
Use the command...
system-view
interface interface-type
interface-number
1-9
Remarks
—
—