Ethernet interface, insert a loopback plug into the interface. During external loopback testing, the
interface sends a certain number of test packets, which are looped over the plug and back to the
interface. If the interface fails to receive any test packet, the hardware of the interface is faulty.
Figure 3 External loopback testing
Follow these steps to enable Ethernet interface loopback testing:
To do… Use the command… Remarks
Enter system view system-view —
Enter Ethernet interface view
interface interface-type
interface-number
—
Perform loopback testing
loopback { external | internal }
Optional
Disabled by default.
NOTE:
• On an interface that is physically down (in the state DOWN), you can perform only internal loopback
testing. On an interface administratively shut down (in the state ADM DOWN), you can perform neither
internal nor external loopback testing.
• The speed, duplex, mdi, and shutdown commands are not available on an interface durin
loopbac
testing.
• During loopback testing, the Ethernet interface operates in full duplex mode. When you disable
loopback testing, the port returns to its duplex setting.
• Loopback testing is a one-time operation, and is not recorded in the configuration file.
Configuring a port group
Some interfaces on your switch might use the same set of settings. To configure these interfaces in bulk
rather than one by one, you can assign them to a port group.
Create port groups manually. All settings made for a port group apply to all the member ports of the
group. For example, you can configure a traffic suppression threshold (see “Configuring storm
suppression on an Ethernet Interface”) for multiple interfaces in bulk by assigning these interfaces to a
port group.
Even though the settings are made on the port group, they are saved on each interface basis rather than
on a port group basis. You can only view the settings in the view of each interface by using the display
current-configuration or display this command.
Follow these steps to configure a port group:
6
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