Planet GS-5220 Series User Manual page 224

Automatically reconfigures the spanning tree to compensate for the failure, addition, or removal of

any element in the tree.
Reconfigures the spanning tree without operator intervention.
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Bridge Protocol Data Units
For STP to arrive at a stable network topology, the following information is used:
The unique switch identifier

The path cost to the root associated with each switch port
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The port identifier
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STP communicates between switches on the network using Bridge Protocol Data Units (BPDUs). Each BPDU
contains the following information:
The unique identifier of the switch that the transmitting switch currently believes is the root switch

The path cost to the root from the transmitting port
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The port identifier of the transmitting port
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The switch sends BPDUs to communicate and construct the spanning-tree topology. All switches connected to
the LAN on which the packet is transmitted will receive the BPDU. BPDUs are not directly forwarded by the
switch, but the receiving switch uses the information in the frame to calculate a BPDU, and, if the topology
changes, initiates a BPDU transmission.
The communication between switches via BPDUs results in the following:
One switch is elected as the root switch

The shortest distance to the root switch is calculated for each switch

A designated switch is selected. This is the switch closest to the root switch through which packets

will be forwarded to the root.
A port for each switch is selected. This is the port providing the best path from the switch to the root

switch.
User's Manual of GS-5220 LCD Series
224