Bridge Priority And The Root Bridge; Table 1 Bridge Priority Value Increments - Allied Telesis AT-GS950/8 User Manual

Bridge Priority
and the Root
Bridge
AlliedWare Plus Version 2.1.2 Management Software Web Browser User's Guide
The first task that bridges perform when a spanning tree protocol is
activated on a network is the selection of a root bridge. A root bridge
distributes network topology information to the other network bridges and
is used by the other bridges to determine if there are redundant paths in
the network.
A root bridge is selected by the bridge priority number, also referred to as
the bridge identifier, and sometimes the bridge's MAC address. The bridge
with the lowest bridge priority number in the network is selected as the root
bridge. If two or more bridges have the same lowest bridge priority
number, the one with the lowest MAC address is designated as the root
bridge.
You can change the bridge priority number in the AT-S107 Management
software. You can designate which switch on your network as the root
bridge by giving it the lowest bridge priority number. You may also
consider which bridge should function as the backup root bridge in the
event you need to take the primary root bridge off line and assign that
bridge the second lowest bridge identifier number.
The bridge priority has a range 0 to 61440 in increments of 4096. To make
this easier for you, the AT-S107 Management software divides the range
into increments. You specify the increment that represents the desired
bridge priority value. The range is divided into sixteen increments, as
shown in Table 1.

Table 1 Bridge Priority Value Increments

Increment
0x0000
0x1000
0x2000
0x3000
0x4000
0x5000
0x6000
0x7000
Bridge
Increment
Priority
0 0x8000
4096 0x9000
8192 0xA000
12288 0xB000
16384 0xC000
20480 0xD000
24576 0xE000
28672 0xF000
Bridge
Priority
32768
36864
40960
45056
49152
53248
57344
61440
113