3com 5500-ei pwr Reference Guide

 

1-27 

# Configure the system to run loopback detection on all VLANs of the trunk port Ethernet 1/0/1. 

<Sysname> system-view 

System View: return to User View with Ctrl+Z. 

[Sysname] interface ethernet 1/0/1 

[Sysname-Ethernet1/0/1] port link-type trunk 

[Sysname-Ethernet1/0/1] loopback-detection per-vlan enable 

Ethernet port view 

None 

Use the loopback-detection shutdown enable command to enable the loopback port auto-shutdown 

function. 

Use the undo loopback-detection shutdown enable command to disable the function.  

The loopback port auto-shutdown function works in conjunction with the loopback detection function 

(refer to loopback-detection enable). If a loop is found at a port: 

z 

With the function enabled on the port, the system will shut down the port, and send log messages 

to the terminal. After the loop is removed, you need to use the undo shutdown command to bring 

up the port. 

z 

With the function disabled on the port, the system will only send log messages to the terminal, and 

the port is still in the normal forwarding state. 

By default, the loopback port auto-shutdown function is enabled on ports if the device boots with the 

default configuration file (config.def); if the device boots with null configuration, this function is disabled.  

Related command: loopback-detection enable; loopback-detection control enable. 

 

You cannot enable both the loopback port control function (with the loopback-detection control 

enable command) and the loopback port auto-shutdown function on a port. If you do so, the function 

configured later will take effect.