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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.
Parameters
These parameters are displayed:
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Global Status – Enables loopback detection globally on the switch.
(Default: Enabled)
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Transmit Interval – Specifies the interval at which to transmit loopback
detection control frames. (Range: 1-32767 seconds; Default: 10 seconds)
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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 (enabled or disabled), 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.
The recover-time is the maximum time when recovery is triggered after a loop
is detected. The actual interval between recovery and detection will be less
than or equal to the recover-time.
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Action – Specifies the protective action the switch takes when a loopback
condition is detected. (Options: Block, None, Shutdown; Default: Shutdown)
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Block – When the response to a detected loopback condition is set to block
user traffic, and a loopback is detected on a port which a member of a
specific VLAN, packets belonging to that VLAN are dropped at the
offending port. Under these conditions, loopback detection control frames
may be untagged or tagged depending on the port’s VLAN membership
type. Ingress filtering for the port is enabled automatically if not already
enabled by other commands. The port’s original setting for ingress filtering
will be restored when loopback detection is disabled.
■
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.
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