Allied Telesis Switch AT-9000/28 Manual de usuario descargar pdf (Pagina 140)

Chapter 12: Setting Switch Spanning Tree Protocols

140

 New Priority (0-15)— Assigns the switch a priority number. The

device that has the lowest priority number in the spanning tree

domain becomes the root bridge. If two or more devices have the

same priority value, the device with the numerically lowest MAC

address becomes the root bridge.

The range is 0 to 61,440, in increments of 4,096. The range is

divided into the sixteen increments listed in Table 2. You specify

the increment that represents the desired bridge priority value. The

default value is 32,768 (increment 8).

Note

Set the hello time, forward delay, and max-age fields according to

the following formulas, as specified in IEEE Standard 802.1d:

max-age <= 2 x (forward time - 1.0 second)

max-age => 2 x (hello time + 1.0 second)

 Hello Time— Indicates the frequency that the switch sends

spanning tree configuration information when it is the root bridge or

is trying to become the root bridge.

 Forward Delay— Indicates the forward time parameter on the

switch. This field specifies how long the ports remain in the

listening and learning states before they transition to the

forwarding state.

The Forward Delay value is active only when the switch is acting

as the root bridge of the spanning tree domain. Switches that are

not acting as the root bridge use a dynamic value supplied by the

root bridge.

Table 2. STP Bridge Priority Value Increments

Increment

Bridge

Priority

Increment

Bridge

Priority

00832768

1 4096 9 36864

2 8192 10 40960

3 12288 11 45056

4 16384 12 49152

5 20480 13 53248

6 24576 14 57344

7 28672 15 61440

1 2 ... 135 136 137 138 139 140 141 142 143 144 145 ... 247 248

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Allied Telesis Switch AT-9000/28 Manual de usuario Pagina 140