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DES-3326S Layer 3 Fast Ethernet Switch User’s Guide
Switch Management and Operating Concepts 61
chance of a given port being
elected as the root port
Port Cost A value used by STP to
evaluate paths – STP
calculates path costs and
selects the path with the
minimum cost as the active
path.
19 – 100Mbps
Fast Ethernet
ports
10 –
1000Mbps
Gigabit
Ethernet
ports
Table 5-5. STP Parameters – Port Group Level
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
• The port identifier
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
• The port identifier of the transmitting port
The switch sends BPDUs to communicate and construct the
spanning-tree topology. All switches connected to the LAN on