Port Management
Loopback Detection Settings
Cisco Sx350, SG350X, SG350XG, Sx550X & SG550XG Series Managed Switches, Firmware Release 2.2.5.x
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To manually reactivate a port:
STEP 1
Click
Port Management
>
Error Recovery Settings
.
The list of inactivated interfaces along with their
Suspension Reason
is displayed.
STEP 2
Select the interface to be reactivated.
STEP 3
Click
Reactivate
.
Loopback Detection Settings
Loopback Detection (LBD) provides protection against loops by transmitting loop protocol
packets out of ports on which loop protection has been enabled. When the switch sends out a
loop protocol packet, and then receives the same packet, it shuts down the port that received
the packet.
Loopback Detection operates independently of STP. After a loop is discovered, the port that
received the loops is placed in the Shut Down state. A trap is sent and the event is logged.
Network managers can define a Detection Interval that sets the time interval between LBD
packets.
The following loop cases can be detected by the Loopback Detection protocol:
•
Shorted wire
—Port that loop backs all receiving traffic.
•
Direct multi-ports loop
—Switch is connected to another switch with more than one
port and STP is disabled.
•
LAN segment loop
—Switch is connected with one or more ports to a LAN segment
that has loops.
How LBD Works
LBD protocol periodically broadcast loopback detection packets. A switch detects a loop
when it receives its own LBD packets.
The following conditions must be true for a port to be LBD active:
•
LBD is globally enabled.
•
LBD is enabled on the port.
