Allied Telesis AT-9000 Series User Manual
Page 150
Chapter 13: Setting Switch Spanning Tree Protocols
150
The range is 0 to 61,440, in increments of 4,096. The range is
divided into the sixteen increments listed in Table 1. 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— 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— 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.
Max Age— How long bridge protocol data units (BPDUs) are
stored by the switch before they are deleted.
Table 1. STP Bridge Priority Value Increments
Increment
Bridge
Priority
Increment
Bridge
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