Loopback Detection Settings - Cisco SX350 Series Administration Manual

Port Management

Loopback Detection Settings

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Loopback Detection Settings
Cisco Sx350, SG350X, SG350XG, Sx550X & SG550XG Series Managed Switches, Firmware Release 2.2.5.x
To manually reactivate a port:
Click Port Management > Error Recovery Settings.
The list of inactivated interfaces along with their Suspension Reason is displayed.
Select the interface to be reactivated.
Click Reactivate.
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.
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