H3C Technologies H3C S5560 Series Switches - Manual (Page 148)

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Port status auto recovery
When the device configured with the block or no-learning loop action detects a loop on a port, it
performs the action and waits three loop detection intervals. If the device does not receive a loop
detection frame within three loop detection intervals, it performs the following tasks:
• Automatically sets the port to the forwarding state.
• Notifies the user of the event.
When the device configured with the shutdown action detects a loop on a port, the following events
occur:
1. The device automatically shuts down the port.
2. The device automatically sets the port to the forwarding state after the detection timer configured
by using the shutdown-interval command expires. For more information about the
shutdown-interval command, see Fundamentals Command Reference.
3. The device shuts down the port again if a loop is still detected on the port when the detection timer
expires.
This process is repeated until the loop is removed.
NOTE:
Incorrect recovery can occur when loop detection frames are discarded to reduce the load. To avoid this
problem, use the shutdown action or manually remove the loop.
Loop detection configuration task list
Tasks at a glance
(Required.) Enabling loop detection
(Optional.) Configuring the loop protection action
(Optional.) Setting the loop detection interval
Enabling loop detection
You can enable loop detection globally or on a per-port basis. The global configuration applies to all
ports in the specified VLANs. The per-port configuration applies to the individual port only when the port
belongs to the specified VLANs. Per-port configurations take precedence over global configurations.
Enabling loop detection globally
Step Command Remarks
1. Enter system view. system-view N/A
2. Globally enable loop
detection. loopback-detection global enable
vlan { vlan-list | all }
Disabled by default.