Loopback Detection - D-Link DGS-1100-16 Reference Manual

The fields that can be configured are described below:
Parameter
From Port / To Port
Port Fast
Click the Apply button to accept the changes made.

Loopback Detection

The Loopback Detection (LBD) function is used to detect the loop created by a specific port. This
feature is used to temporarily shut down a port on the Switch when a CTP (Configuration Testing
Protocol) packet has been looped back to the Switch. When the Switch detects CTP packets
received from a port, this signifies a loop on the network. The Switch will automatically block the port
and send an alert to the administrator. The Loopback Detection port will restart (change to normal
state) when the Loopback Detection Recover Time times out. The Loopback Detection function can
be implemented on a range of ports at a time. The user may enable or disable this function using the
drop-down menu.
To view the following window, click L2 Features > Loopback Detection, as shown below:
Figure 7-223 STP Port Settings window
Description
Select the appropriate port range used for the configuration
here.
Select the port fast option here. Options to choose from are
Network, Disabled, and Edge. In the Network mode the
port will remain in the non-port-fast state for three seconds.
The port will change to the port-fast state if no BPDU is
received and changes to the forwarding state. If the port
received the BPDU later, it will change to the non-port-fast
state. In the Disable mode, the port will always be in the
non-port-fast state. It will always wait for the forward-time
delay to change to the forwarding state. In the Edge mode,
the port will directly change to the spanning-tree forwarding
state when a link-up occurs without waiting for the forward-
time delay. If the interface receives a BPDU later, its
operation state changes to the non-port-fast state. By default,
this option is Edge.
Figure 7-234 Loopback Detection window
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D-Link DGS-1100 Series Switch User Manual
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