Bridge Priority And The Root Bridge - Allied Telesis AT-8100L/8 User Manual

AT-8100 Switch Command Line User's Guide

Bridge Priority and the Root Bridge

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. 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 bridge priority number, of those bridges, the one with the lowest
MAC address is designated as the root bridge.
You can change the bridge priority number on the switch. You can
designate which switch on your network you want as the root bridge by
giving it the lowest bridge priority number. You might also consider which
bridge should function as the backup root bridge in the event you need to
take the primary root bridge offline, and assign that bridge the second
lowest bridge identifier number.
The bridge priority has a range 0 to 61,440 in increments of 4,096. A lower
priority number indicates a greater likelihood of the switch becoming the
root bridge. The priority values can be set only in increments of 4,096. The
default value is 32,768.
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