Loopback Detection - Cisco Small Business 200 Series Administration Manual

Port Management

Loopback Detection

• Automatic Recovery Interval—Specify the time delay for automatic error recovery, if enabled, after
a port is shutdown
Automatic ErrDisable Recovery
• Port Security—Select to enable automatic error recovery when the port has been shut down for port
security violations
• 802.1x Single Host Violation—Select to enable automatic error recovery when the port has been
shut down by 802.1x.
• STP Loopback Guard— Enable automatic recovery when the port has been shut down by STP
Loopback Guard.
• Loopback Detection—Select to enable error recovery mechanism for ports shut down by loopback
detection.
STEP 3
To manually reactivate a port:
STEP 1
The list of inactivated interfaces along with their Suspension Reason is displayed.
STEP 2
STEP 3
Loopback Detection
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 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.
Cisco Small Business 200 Series Smart Switch Administration Guide
Click Apply to update the global setting.
Click Port Management > Error Recovery Settings.
Select the interface to be reactivated.
Click Reactivate.
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