Enabling Loopback Detection On An Ethernet Interface; Configuration Restrictions And Guidelines; Configuration Procedure - HP 6125G Configuration Manual

Enabling loopback detection on an Ethernet
interface
If a switch receives a packet that it sent, a loop has occurred to the switch. Loops might cause broadcast
storms, which degrade network performance. You can use this feature to detect whether a loop has
occurred.
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 to take on the receiving interface
when a loop is detected, for example, to shut down the interface. Depending on whether a protective
action is configured, the switch takes the actions in
Table 1 Actions to take upon detection of a loop condition
Port type
Access port
Hybrid or
trunk port

Configuration restrictions and guidelines

• To use loopback detection on an Ethernet interface, you must enable the function both globally and
on the interface.
To disable loopback detection on all interfaces, run the undo loopback-detection enable command
•
in system view.
To enable a hybrid or trunk port to take the administratively specified protective action, you must use
•
the loopback-detection control enable command on the port.
• When you change the link type of an Ethernet interface by using the port link-type command, the
switch removes the protective action configured on the interface. For more information about the
port link-type command, see Layer 2—LAN Switching Command Reference.

Configuration procedure

To configure loopback detection:
Step
1. Enter system view.
2. Enable global
loopback detection.
Actions
No protective action is configured
•
Place the receiving interface in controlled mode.
The interface does not receive or send packets.
•
Generate traps and log messages.
•
Delete all MAC address entries of the interface.
•
Generate traps and log messages.
•
If loopback detection control is enabled, place
the receiving interface in controlled mode. The
interface does not receive or send packets.
•
Delete all MAC address entries of the interface.
Command
system-view
loopback-detection enable
Table 1 to alleviate the impact of the loop condition.
A protective action is configured
•
•
•
•
•
•
Remarks
N/A
Disabled by default.
9
Perform the configured protective
action.
Generate traps and log messages.
Delete all MAC address entries of the
interface.
Generate 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.