R21xx-HP FlexFabric 11900 Layer 2 LAN Switching Command Reference

21
loopback
Use loopback to perform a loopback test on an Ethernet interface.
Use undo loopback to cancel a loopback test on an Ethernet interface.
Syntax
loopback { external | internal }
undo loopback
Views
Ethernet interface view
Predefined user roles
network-admin
Parameters
external: Performs an external loopback test on the Ethernet interface.
internal: Performs an internal loopback test on the Ethernet interface.
Usage guidelines
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.
On a physically down interface (displayed as in DOWN state), you can only perform an internal
loopback test, and an external loopback test will fail. On an administratively shut down interface
(displayed as in ADM or Administratively DOWN state), you cannot perform an internal or external
loopback test.
The speed, duplex, mdi, and shutdown commands are not available during a loopback test.
During a loopback test, the Ethernet interface operates in full duplex mode. When the loopback test is
complete, the port returns to its duplex setting.
Examples
# Perform an internal loopback test on Ten-GigabitEthernet 1/0/1.
<Sysname> system-view
[Sysname] interface ten-gigabitethernet 1/0/1
[Sysname-Ten-GigabitEthernet1/0/1] loopback internal
port link-mode
Use port link-mode to change the link mode of an Ethernet interface.
Use undo port link-mode to restore the default.
Syntax
port link-mode { bridge | route }
undo port link-mode
Default
An Ethernet interface operates in bridge mode.