Alcatel-Lucent OmniSwitch 6250, Cli Reference Manual, Page: 617 / 2018

OmniSwitch 6250 CLI Reference Guide November 2009 page 17-1
17 Loopback Detection
Commands
Loopback Detection (LBD) automatically detects and prevents forwarding loops on ports that have
forwarded network traffic which has looped back to the originating switch. LBD detects and prevents
Layer 2 forwarding loops on a port either in the absence of other loop detection mechanisms such as STP/
RSTP/MSTP, or when these mechanisms cannot detect it (e.g., a client's equipment may drop BPDUs, or
the STP protocol may be restricted to the network edge). On a linkagg port, if one port of linkagg is
getting shutdown due to LBD then all the ports of linkagg will go to shutdown state.
Loopback Detection is enabled system wide and on a per-port basis.Once a loop is discovered, the port
from which the loop originated is placed into an “Inactive” state and when the two ports of a switch is
connected to each other via a hub, either the ports will be shutdown or it will be in normal state.
When loopback occurs, a trap is sent and the event is logged. The port can manually be enabled again
when the problem is resolved, or a Network Manager can define a recovery interval that automatically
places the port into a “Normal” state after a defined period of time.
MIB information for the Loopback Detection commands is as follows:
Filename : alcatelIND1LBD.mib
Module : ALCATEL-IND1-LBD-MIB
A summary of available commands is listed here:
loopback-detection
loopback-detection port
loopback-detection transmission-timer
loopback-detection autorecovery-timer
show loopback-detection
show loopback-detection port
show loopback-detection statistics port