A copper Ethernet interface uses an RJ-45 connector, which comprises eight pins, each of which plays a
dedicated role. For example, pins 1 and 2 transmit signals, and pins 3 and 6 receive signals. The pin
role varies by the MDI modes as follows:
In normal mode, pins 1 and 2 are transmit pins, and pins 3 and 6 are receive pins.
In across mode, pins 1 and 2 are receive pins, and pins 3 and 6 are transmit pins.
In auto mode, the interface negotiates pin roles with its peer.
To enable the interface to communicate with its peer, ensure that its transmit pins are connected to the
remote receive pins. If the interface can detect the connection cable type, set the interface in auto MDI
mode. If not, set its MDI mode by using the following guidelines:
When a straight-through cable is used, set the interface to work in the MDI mode different than its
peer.
When a crossover cable is used, set the interface to work in the same MDI mode as its peer, or set
either end to work in auto mode.
Follow these steps to set the MDI mode of an Ethernet interface:
To do...
Enter system view
Enter Ethernet interface view
Set the MDI mode of the Ethernet
interface
Enabling bridging on an Ethernet interface
When an incoming packet arrives, the switch looks up the destination MAC address of the packet in the
MAC address table. If an entry is found, but the outgoing interface is the same as the receiving interface
(for example, if the destination and source MAC addresses of the packet are the same), the switch
discards the packet.
To enable the switch to return such packets to the sender through the receiving interface rather than drop
them, enable the bridging function on the Ethernet interface.
Follow these steps to enable bridging on an Ethernet interface:
To do...
Enter system view
Enter Ethernet interface view
Enable bridging on the Ethernet
interface
Testing the cable connection of an Ethernet interface
Use the command...
system-view
interface interface-type interface-
number
mdi { across | auto | normal }
Use the command...
system-view
interface interface-type interface-
number
port bridge enable
14
Remarks
—
—
Optional
By default, a copper Ethernet
interface operates in auto mode to
negotiate pin roles with its peer.
Remarks
—
—
Required
Disabled by default.