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ZT8101 User’s Manual 29
Switch Management and Operating Concepts
STP Parameters for the Switch Level
The following are the user-configurable STP parameters for the switch level.
Use the following formulas when setting these parameters:
• Max Age = 2 x (Forward Delay -1second)
• Mag Age = 2 x (Hello Time + 1 second)
STP Parameters for the Port Level
The following are the user-configurable STP parameters for the port or port group level.
Parameter Description Default Value
Bridge Identifier
Specifies the 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. The only portion that a user
can configure is the priority.
32768 + MAC address
Priority
Specifies the relative priority for each switch. Lower
numbers specify a higher priority and a greater chance
of a given switch being elected as the root bridge
32768
Hello Time
Specifies the length of time between broadcasts of the
hello message by the switch. It can be set from 1 — 10
seconds. This interval is not used until the switch
becomes (if ever) the root bridge.
The Hello Time parameter cannot be longer than the
Max Age parameter.
2 seconds
Max Age
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 Max Age parameter.
It can be set from 6 — 40 seconds.
20 seconds
Forward Delay
Specifies the time a port can remaining in the listening
state while moving from the blocking state to the
forwarding state.
It can be set from 4 — 30 seconds.
15 seconds
Variable Description Default Value
Port Priority
A relative priority for each port. Lower numbers specify
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 for 10 Mbps Fast
Etherenet ports
• 19 for 100 Mbps Fast
Ethernet ports
• 4 for 1000 Mbps Gigabit
Ethernet ports