Verifying the configuration – H3C Technologies H3C S12500 Series Switches User Manual
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[DeviceB-GigabitEthernet4/0/2] quit
Verifying the configuration
Use the display loopback-detection command to check the status of loopback detection on each device.
# Display the loopback detection status on Device A.
[DeviceA] display loopback-detection
Loopback-detection is running.
Detection interval is 30 second(s).
Action mode: Shutdown
Loopback-detection is enabled on the following VLAN(s):
100
No loopback is detected on any interface.
The output shows that loopback detection is enabled on Device A, and no looped ports are detected.
# Display the loopback detection status on Device B.
[DeviceB] display loopback-detection
Loopback-detection is not running.
# Display the loopback detection status on Device C.
[DeviceC] display loopback-detection
Loopback-detection is not running.
The output shows that loopback detection is not enabled on Device B or Device C.
GigabitEthernet 4/0/1 of Device B is brought up by the network administrator by mistake. Within a
loopback detection interval, Device A will detect a loop on ports GigabitEthernet 4/0/1 and
GigabitEthernet 4/0/2. Consequently, it automatically shuts down the ports and prints the following log
information:
[DeviceA]
%Feb 24 15:04:29:663 2013 DeviceA LPDT/4/LOOPED:Slot=4;
Loopback exists on GigabitEthernet4/0/1 in VLAN 100.
%Feb 24 15:04:29:667 2013 DeviceA LPDT/4/LOOPED:Slot=1;
Loopback exists on GigabitEthernet4/0/2 in VLAN 100.
%Feb 24 15:04:44:243 2013 DeviceA LPDT/4/RECOVERED:Slot=4;
Loopback on GigabitEthernet4/0/1 recovered.
%Feb 24 15:04:44:248 2013 DeviceA LPDT/4/RECOVERED:Slot=1;
Loopback on GigabitEthernet4/0/2 recovered.
When you see the log information above, use the display loopback-detection command again to display
the loopback detection status on Device A.
# Display the loopback detection operating status on Device A.
[DeviceA] display loopback-detection
Loopback-detection is running.
Detection interval is 35 second(s).
Action mode: Shutdown
Loopback-detection is enabled on the following VLAN(s):
100
No loopback is detected on any interface.