8
IMPORTANT:
This feature is used only for debugging and troubleshooting.
Perform this task to determine whether an Ethernet link operates correctly.
Loopback testing includes the following types:
•
Internal loopback testing
—Tests the device where the Ethernet interface resides. The
Ethernet interface sends outgoing packets back to the local device. If the device fails to receive
the packets, the device fails.
•
External loopback testing
—Tests the inter-device link. The Ethernet interface sends incoming
packets back to the remote device. If the remote device fails to receive the packets, the
inter-device link fails
After you enable this feature on an Ethernet interface, the Ethernet interface switches to full duplex
mode. After you disable this feature, the Ethernet interface restores to its duplex setting.
Configuration restrictions and guidelines
When you perform loopback tests, follow these restrictions and guidelines:
•
You cannot enable loopback testing on an administratively shut down Ethernet interface
(displayed as in
ADM
or
Administratively DOWN
state).
•
After you enable loopback testing on an Ethernet interface, the
speed
,
duplex
,
mdix-mode
,
port up-mode
, and
shutdown
commands are not available on the Ethernet interface.
•
Do not enable loopback testing on an interface enabled with voice VLAN, MAC learning limit,
MAC address learning, 802.1X, or MAC authentication. Otherwise, these features cannot take
effect. To enable these features to take effect on the interface, cancel the loopback test and
configure the features again.
Configuration procedure
To enable loopback testing 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.
Enable loopback testing.
loopback
{
external
|
internal
}
By default, loopback testing is
disabled on an Ethernet interface.
Configuring generic flow control on an Ethernet interface
IMPORTANT:
•
This feature is not applicable to interfaces that operate in the half duplex mode.
•
Enabling or disabling this feature on an interface will cause the interface to go down and then
come up.
To avoid dropping packets 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. Generic flow control includes the
following types:
•
TxRx-mode
generic
flow
control
—Enabled by using the
flow-control
command. With
TxRx-mode generic flow control enabled, an interface can both send and receive flow control
frames:
Summary of Contents for S7500E-XS Series
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