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DGS-3120 Series Managed Switch CLI Reference Guide 
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Chapter 42  Loop Back Detection (LBD) 
Command List 
 
config loopdetect {recover_timer [<value 0> | <sec 60-1000000>] | interval <sec 1-32767> | 
mode [port-based | vlan-based]} 
config loopdetect ports [<portlist> | all] state [enable | disable] 
show loopdetect ports {<portlist>} 
config loopdetect trap [none | loop_detected | loop_cleared | both] 
config loopdetect log state [enable | disable] 
 
42-1  config loopdetect 
Description 
This command is used to setup the loop-back detection function (LBD) for the entire Switch. 
 
Format 
config loopdetect {recover_timer [<value 0> | <sec 60-1000000>] | interval <sec 1-32767> | 
mode [port-based | vlan-based]} 
 
Parameters 
recover_timer - (Optional) The time interval (in seconds) used by the Auto-Recovery mechanism 
to decide how long to check before determining that the loop status has gone. The valid range 
is from 60 to 1000000. 0 is a special value that specifies that the auto-recovery mechanism 
should be disabled. When the auto-recovery mechanism is disabled, a user would need to 
manually recover a disabled port. The default value for the recover timer is 60 seconds. 
<value 0> - 0 is a special value that specifies that the auto-recovery mechanism should be 
disabled. When the auto-recovery mechanism is disabled, a user would need to manually 
recover a disabled port. 
<sec 60-1000000> - Enter the recovery timer value here. This value must be between 60 and 
interval - (Optional) The time interval (in seconds) that the device will transmit all the CTP 
(Configuration Test Protocol) packets to detect a loop-back event. The default setting is 10 
seconds. The valid range is from 1 to 32767 seconds. 
<sec - 1-32767> - Enter the time interval value here. This value must be between 1 and 
mode - (Optional) Specify the loop-detection operation mode. In port-based mode, the port will 
be shut down (disabled) when loop has been detected In VLAN-based mode, the port cannot 
process the packets of the VLAN that has detected the loop. 
port-based - Specify that the loop-detection operation mode will be set to port-based mode. 
 - Specify that the loop-detection operation mode will be set to vlan-based mode. 
 
Restrictions 
Only Administrator, Operator and Power-User level users can issue this command.