Basic Administration Protocols
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Instruction Manual - NXA-ENET8-POE+
LBD Configuration
The switch can be configured to detect general loopback conditions caused by hardware problems or faulty protocol settings.
When enabled, a control frame is transmitted on the participating ports, and the switch monitors inbound traffic to see if the frame
is looped back.
Usage Guidelines
The default settings for the control frame transmit interval and recover time may be adjusted to improve performance for
your specific environment. The shutdown mode may also need to be changed once you determine what kind of packets are
being looped back.
General loopback detection provided by the commands described in this section and loopback detection provided by the
spanning tree protocol cannot both be enabled at the same time. If loopback detection is enabled for the spanning tree
protocol, general loopback detection cannot be enabled on the same interface.
When a loopback event is detected on an interface or when a interface is released from a shutdown state caused by a
loopback event, a trap message is sent and the event recorded in the system log.
Loopback detection must be enabled both globally and on an interface for loopback detection to take effect.
Configuring Global Settings for LBD
Use the Administration > LBD (Configure Global) page to enable loopback detection globally, specify the interval at which to
transmit control frames, the interval to wait before releasing an interface from shutdown state, the response to a detected
loopback, and the traps to send.
The following table lists the options on this page:
Administration - LBD (Configure Global) Options
Global Status
Enables loopback detection globally on the switch. (Default: Enabled)
Transmit Interval
Specifies the interval at which to transmit loopback detection control frames. (Range: 1-32767
seconds; Default: 10 seconds)
Recover Time
Specifies the interval to wait before the switch automatically releases an interface from shutdown
state. (Range: 60-1,000,000 seconds; Default: 60 seconds)
When the loopback detection mode is changed, any ports placed in shutdown state by the
loopback detection process will be immediately restored to operation regardless of the remaining
recover time.
If the recover time is not enabled (checkbox unmarked), all ports placed in shutdown state can be
restored to operation using the Release button. To restore a specific port, re-enable Admin status
on the Configure Interface page.
Action
Specifies the protective action the switch takes when a loopback condition is detected. (Options:
None, Shutdown; Default: Shutdown)
• None - No action is taken.
• Shutdown - When the response to a detected loopback condition is set to shut down a port, and
a port receives a control frame sent by itself, this means that the port is in looped state, and the
VLAN in the frame payload is also in looped state with the wrong VLAN tag. The looped port is
therefore shut down.
When the loopback detection response is changed, any ports placed in shutdown state by the
loopback detection process will be immediately restored to operation regardless of the
remaining recover time.
Trap
Sends a trap when a loopback condition is detected, or when the switch recovers from a loopback
condition. (Options: Both, Detect, None, Recover; Default: None)
• Both - Sends an SNMP trap message when a loopback condition is detected, or when the switch
recovers from a loopback condition.
• Detect - Sends an SNMP trap message when a loopback condition is detected.
• None - Does not send an SNMP trap for loopback detection or recovery.
• Recover - Sends an SNMP trap message when the switch recovers from a loopback condition.
Release
Releases all interfaces currently shut down by the loopback detection feature.