1-20 
[Sysname] interface Ethernet1/0/5 
[Sysname-Ethernet1/0/5] link-delay 8 
loopback 
Syntax 
loopback { external | internal } 
View 
Ethernet port view 
Parameter 
external: Performs external loop test. In the external loop test, self-loop headers  must be used on the 
port of the switch ( for 100M port, the self-loop headers are made from four cores of the 8-core cables, 
for 1000M port, the self-loop header are made from eight cores of the 8-core cables, then the packets 
forwarded by the port will be received by itself.). The external loop test can locate the hardware failures 
on the port.   
internal: Performs internal loop test. In the internal loop test, self loop is established in the switching 
chip to locate the chip failure which is related to the port.  
Description 
Use the loopback command to perform a loopback test on the current Ethernet port to check whether 
the Ethernet port works normally. The loopback test terminates automatically after running for a specific 
period.  
By default, no loopback test is performed on the Ethernet port.  
Example 
# Perform an internal loop test on Ethernet1/0/1.  
<Sysname>  system-view 
System View: return to User View with Ctrl+Z. 
[Sysname] interface ethernet 1/0/1 
[Sysname-Ethernet1/0/1] loopback internal 
 Loopback internal succeeded. 
loopback-detection control enable 
Syntax 
loopback-detection control enable 
undo loopback-detection control enable 
View 
Ethernet port view 
Parameter 
None 
Description 
Use the loopback-detection control enable command to enable the loopback port control function on 
the current trunk or hybrid port.