6
Step Command
Remarks
3.
Configure physical
state change
suppression on the
interface.
link-delay
delay-time
[
mode
{
up
|
updown
}]
By default, the link-down or link-up event is
immediately reported to the CPU.
If you configure this command multiple times on an
Ethernet interface, the most recent configuration
takes effect.
Performing a loopback test on an Ethernet interface
If an Ethernet interface does not work correctly, you can perform a loopback test on it to identify the
problem. An Ethernet interface in a loopback test does not forward data traffic.
Loopback tests include the following types:
•
Internal loopback test
—Tests all on-chip functions related to the Ethernet interface.
•
External loopback test
—Tests the hardware of the Ethernet interface. To perform an external
loopback test on the Ethernet interface, connect a loopback plug to the Ethernet interface. The
device sends test packets out of the interface, which are expected to loop over the plug and back
to the interface. If the interface fails to receive any test packets, the hardware of the interface is
faulty.
Configuration restrictions and guidelines
•
On an administratively shut down Ethernet interface (displayed as in
ADM
or
Administratively
DOWN
state), you cannot perform an internal or external loopback test.
•
The
speed
,
duplex
,
mdix-mode
, and
shutdown
commands are not available during a loopback
test.
•
During a loopback test, the Ethernet interface operates in full duplex mode. When a loopback test
is complete, the port returns to its duplex setting.
Configuration procedure
To perform a loopback test on an Ethernet interface:
Step Command
Remarks
1.
Enter system view.
system-view
N/A
2.
Enter Ethernet interface view.
interface
interface-type
interface-number
N/A
3.
Perform a loopback test.
loopback
{
external
|
internal
}
By default, no loopback test is
performed.
Configuring generic flow control on an Ethernet interface
To avoid packet drops on a link, you can enable generic flow control at both ends of the link. When
traffic congestion occurs at the receiving end, the receiving end sends a flow control (Pause) frame to ask
the sending end to suspend sending packets.
•
With TxRx mode generic flow control enabled, an interface can both send and receive flow control
frames. When congestion occurs, the interface sends a flow control frame to its peer. When the
interface receives a flow control frame from the peer, it suspends sending packets.
