Allied Telesis AT-S63 - Manual (Page 262)

Chapter 16: STP and RSTP
262 Section II: Advanced Features
3. Adjust the following parameters as needed.
1 - Bridge Priority
The priority number for the bridge. This number is used to
determine the root bridge for RSTP. The bridge with the lowest
priority number is selected as the root bridge. If two or more
bridges have the same priority value, the bridge with the
numerically lowest MAC address becomes the root bridge. When
a root bridge goes offline, the bridge with the next priority
number automatically takes over as the root bridge. This
parameter can be from 0 (zero) to 61,440 in increments of 4096,
with 0 being the highest priority. For a list of the increments, refer
to Table 12, Bridge Priority Value Increments on page 251.
2 - Bridge Hello Time
The time interval between generating and sending configuration
messages by the bridge. This parameter can be from 1 to 10
seconds. The default is 2 seconds.
3 - Bridge Forwarding
The waiting period in seconds before a bridge changes to a new
state, for example, becomes the new root bridge after the
topology changes. If the bridge transitions too soon, not all links
may have yet adapted to the change, resulting in network loops.
The range is 4 to 30 seconds. The default is 15 seconds.
4 - Bridge Max Age
The length of time after which stored bridge protocol data units
(BPDUs) are deleted by the bridge. All bridges in a bridged LAN
use this aging time to test the age of stored configuration
messages called bridge protocol data units (BPDUs). For example,
if you use the default value 20, all bridges delete current
configuration messages after 20 seconds. This parameter can be
from 6 to 40 seconds.
When you select a value for maximum age, observe the following
rules:
MaxAge must be greater than (2 x (HelloTime + 1)).
MaxAge must be less than (2 x (ForwardingDelay - 1)).
Note
The aging time for BPDUs is different from the aging time used by
the MAC address table.
5 - Bridge Identifier
The MAC address of the switch. This value cannot be changed.