1-10
To do… Use the command… Remarks
Configure the system to run
loopback detection on all
VLANs for the trunk and hybrid
ports
loopback-detection per-vlan
enable
Optional
By default, the system runs
loopback detection only on the
default VLAN for the trunk and
hybrid ports.
z To enable loopback detection on a specific port, you must use the loopback-detection enable
command in both system view and the specific port view.
z After you use the undo loopback-detection enable command in system view, loopback detection
will be disabled on all ports.
z The commands of loopback detection feature cannot be configured with the commands of port link
aggregation at the same time.
Configuring the Ethernet Port to Run Loopback Test
You can configure the Ethernet port to run loopback test to check if it operates normally. The port
running loopback test cannot forward data packets normally. The loopback test terminates
automatically after a specific period.
Follow these steps to configure an Ethernet port to run loopback test:
To do… Use the command… Remarks
Enter system view system-view —
Enter Ethernet port view interface interface-type
interface-number —
Configure the Ethernet port to run
loopback test loopback { external | internal } Required
z external: Performs external loop test. In the external loop test, self-loop headers (which are made
from four cores of the 8-core cables) must be used on the ports of the device. The external loop test
can locate the hardware failures on the port.
z internal: Performs internal loop test. In the internal loop test, self loop is established in the
switching chip to locate the chip failure which is related to the port.
After you use the shutdown command on a port, the port cannot run loopback test. You cannot use the
speed, duplex, mdi and shutdown commands on the ports running loopback test. Some ports do not
support loopback test, and corresponding prompts will be given when you perform loopback test on
them.