The Switch User’s Guide
Blocking
Switch boot
Listening
Learning
Forwarding
Disabled
Figure 5-20 STP Port State Transitions
You can modify each port state by using management software. When you enable
STP, every port on every switch in the network goes through the blocking state and
then transitions through the states of listening and learning at power up. If properly
configured, each port stabilizes to the forwarding or blocking state. No packets
(except BPDUs) are forwarded from, or received by, STP enabled ports until the
forwarding state is enabled for that port.
2. STP Parameters
The following are the user-configurable STP parameters for the switch level:
Parameter Description
Default
Value
Bridge Identifier(Not user
configurable
except by setting priority
below)
A combination of the User-set
priority and the switch’s MAC
address.
The Bridge Identifier consists of
two parts:
a 16-bit priority and a 48-bit
Ethernet MAC address 32768 +
MAC
32768 + MAC
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 20 seconds
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