1-8
To do…
Use the command…
Remarks
Enter system view
system-view
—
Enable global loopback
detection
loopback-detection enable
Required
Disabled by default
Configure the interval for port
loopback detection
loopback-detection
interval-time time
Optional
30 seconds by default
Enter Ethernet port view
interface interface-type
interface-number
—
Enable loopback detection on a
port
loopback-detection enable
Required
Disabled by default
Enable loopback detection
control on a trunk port or a
hybrid port
loopback-detection control
enable
Optional
Disabled by default
Enable loopback detection in all
the VLANs to which trunk or
hybrid ports belong
loopback-detection per-vlan
enable
Optional
Enabled only in the default
VLAN(s) with trunk port or
hybrid ports
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 port 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 Port
10-Gigabit Ethernet ports and optical ports 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 port 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 port 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 port in normal mode, the pin roles
are not changed. For an Ethernet port in across mode, pin 1 and pin 2 are used for receiving signals; pin