Configuration Restrictions And Guidelines - HP 5120 EI Series Lan Switching Configuration Manual

Figure 4 Multi-port loop
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.
When the multi-port loopback detection function is enabled, the function can also detect single-port
•
loops.
• 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.
Actions
No protective action is configured
•
Place the receiving interface in controlled mode.
The interface drops the incoming packets and
correctly sends 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.
Table 1 to alleviate the impact of the loop condition.
A protective action is configured
•
•
•
•
•
•
11
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.