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DES-3226 NWay Standalone Fast Ethernet Switch User’s Guide
below) address
Priority A relative priority for each switch –
lower numbers give a higher
priority and a greater chance of a
given switch being elected as the
root bridge
32768
Hello Time The length of time between
broadcasts of the hello message by
the switch
2 seconds
Maximum Age Timer Measures the age of a received
BPDU for a port and ensures that
the BPDU is discarded when its
age exceeds the value of the
maximum age timer.
20 seconds
Forward Delay Timer The amount time spent by a port
in the learning and listening states
waiting for a BPDU that may
return the port to the blocking
state.
15 seconds
Table 5-1. STP Parameters – Switch Level
The following are the user-configurable STP parameters for the port or port group level:
Variable Description Default
Value
Port Priority A relative priority for each port –
lower numbers give a higher
priority and a greater chance of a
given port being elected as the root
port
32768
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.
100 – 100Mbps
Fast Ethernet
ports
Table 5-2. 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
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