H3C Technologies H3C S5120 Series Switches - Manual (Page 91)

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To do… Use the command… Remarks
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 permitted on the
trunk or hybrid port
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 interface view of the port.
z Loopback detection on all ports will be disabled after you configure the undo loopback-detection
enable command in system view.
Configuring the MDI Mode for an Ethernet Port
The 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 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
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.