Allied Telesis AT-9000/28SP, AT-9000/52 manual

Chapter 12: Setting Switch Spanning Tree Protocols

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).

Table 2. STP Bridge Priority Value Increments

Increment	Bridge	Increment	Bridge
	Priority		Priority
0	0	8	32768
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

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.

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