Switch Management and Operating Concepts

STP Parameters for the Switch Level

The following are the user-configurable STP parameters for the switch level.

Parameter

Description

Default Value

 

 

 

 

Specifies the combination of the user-set priority and

 

 

the switch’s MAC address. The bridge identifier

 

Bridge Identifier

consists of two parts: a 16-bit priority and a 48-bit

32768 + MAC address

 

Ethernet MAC address. The only portion that a user

 

 

can configure is the priority.

 

 

 

 

 

Specifies the relative priority for each switch. Lower

 

Priority

numbers specify a higher priority and a greater chance

32768

 

of a given switch being elected as the root bridge

 

 

 

 

 

Specifies the length of time between broadcasts of the

 

 

hello message by the switch. It can be set from 1 — 10

 

Hello Time

seconds. This interval is not used until the switch

2 seconds

becomes (if ever) the root bridge.

 

 

 

The Hello Time parameter cannot be longer than the

 

 

Max Age parameter.

 

 

 

 

 

Measures the age of a received BPDU for a port, and

 

Max Age

ensures that the BPDU is discarded when its age

20 seconds

exceeds the value of the Max Age parameter.

 

 

 

It can be set from 6 — 40 seconds.

 

 

 

 

 

Specifies the time a port can remaining in the listening

 

Forward Delay

state while moving from the blocking state to the

15 seconds

forwarding state.

 

 

 

It can be set from 4 — 30 seconds.

 

 

 

 

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.

Variable

Description

Default Value

 

 

 

 

A relative priority for each port. Lower numbers specify

 

Port Priority

a higher priority and a greater chance of a given port

32768

 

being elected as the root port

 

 

 

 

 

 

• 100 for 10 Mbps Fast

 

A value used by STP to evaluate paths. STP calculates

Etherenet ports

 

• 19 for 100 Mbps Fast

Port Cost

path costs and selects the path with the minimum cost

Ethernet ports

 

as the active path.

 

• 4 for 1000 Mbps Gigabit

 

 

 

 

Ethernet ports

 

 

 

ZT8101 User’s Manual

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Intel ZT8101 STP Parameters for the Switch Level, STP Parameters for the Port Level, Parameter Description Default Value