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
STP Operation Levels
The Switch allows for two levels of operation: the switch level and the port level. The switch level forms a spanning
tree consisting of links between one or more switches. The port level constructs a spanning tree consisting of
groups of one or more ports. The STP operates in much the same way for both levels.
NOTICE:
On the switch level, STP calculates the Bridge Identifier for each switch and then sets the
Root Bridge and the Designated Bridges.
On the port level, STP sets the Root Port and the Designated Ports.
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 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
The following are the user-configurable STP parameters for the port or port group level:
Variable
Description
Default Value
