HP 6125G HP 6125G & 6125G/XG Blade Switches Layer 2 - LAN Switching Co - Page 18

Enabling loopback detection on an Ethernet interface, Configuration restrictions and guidelines - switch commands

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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 to alleviate the impact of the loop condition. Table 1 Actions to take upon detection of a loop condition Port type Access port Hybrid or trunk port 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. A protective action is configured • 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. 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. Command system-view loopback-detection enable Remarks N/A Disabled by default. 9

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9
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
to alleviate the impact of the loop condition.
Table 1
Actions to take upon detection of a loop condition
Port type
Actions
No protective action is configured
A protective action is configured
Access port
•
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.
•
Perform the configured protective
action.
•
Generate traps and log messages.
•
Delete all MAC address entries of the
interface.
Hybrid or
trunk port
•
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.
•
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.
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
Command
Remarks
1.
Enter system view.
system-view
N/A
2.
Enable global
loopback detection.
loopback-detection enable
Disabled by default.