Loopback-Detection Enable - HP 3100 v2 Series Command Reference Manual

loopback-detection enable

Syntax
loopback-detection enable
undo loopback-detection enable
View
System view, Ethernet interface view, port group view
Default level
2: System level
Parameters
None
Description
Use loopback-detection enable to enable loopback detection globally in system view or on
interfaces in Ethernet interface or port group view. To use loopback detection on an Ethernet
interface, you must enable the function both globally and on the port.
Use undo loopback-detection enable to disable loopback detection globally or on Ethernet
interfaces.
The undo loopback-detection enable command in system view disables loopback detection on all
interfaces.
By default, loopback detection is disabled on all Ethernet interfaces.
If an interface receives a packet that it sent out, a loop has occurred. Loops may cause broadcast
storms, which degrade network performance. You can enable loopback detection to detect loops on
an interface and, if the interface supports the loopback-detection action command, configure the
protective action (shut down the port, for example) to take on the interface when a loop is detected.
In addition to the configured protective action, the switch also performs other actions to alleviate the
impact of the loop condition. For more information, see
Table 9 Actions to take upon detection of a loop condition
Port type
Access port
Hybrid or trunk
port
Related commands: loopback-detection control enable.
Examples
# Enable loopback detection on Ethernet 1/0/1.
Actions
No protective action is configured
•
Place the interface in controlled mode.
The interface does not receive or send
packets.
•
Generate traps.
•
Delete all MAC address entries of the
interface.
•
Generate traps.
•
If loopback detection control is enabled,
set the interface in controlled mode. The
interface does not receive or send
packets.
•
Delete all MAC address entries of the
interface.
Table 9.
A protective action is configured
•
•
•
•
•
•
25
Perform the configured protective
action.
Generate traps and log
messages.
Delete all MAC address entries of
the interface.
Create traps and log messages.
If loopback detection control is
enabled, take the configured
protective action on the interface.
Delete all MAC address entries of
the interface.