Allied Telesis AT-S60 - Manual (Page 678)

Chapter 39: STP, RSTP, and MSTP
Section VI: Web Browser Management 678
bridges have the same priority value, the bridge with the
numerically lowest MAC address becomes the root bridge. When
a root bridge goes off-line, the bridge with the next priority
number automatically takes over as the root bridge. This
parameter can be from 0 (zero) to 15, with 0 having the highest
priority. For a list of the increments, refer to Table 9, Bridge
Priority Value Increments on page 231
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.
Bridge Forwarding
The waiting period 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, possibly resulting in a network loop.
The range is 4 to 30 seconds. The default is 15 seconds.
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 of 20, all bridges delete current
configuration messages after 20 seconds. The range of this
parameter is from 6 to 40 seconds. The default is 20 seconds.
In selecting a value for maximum age, you must observe the
following equations:
MaxAge < (2 x (HelloTime + 1))
MaxAge < (2 x (ForwardingDelay - 1))
Bridge Identifier
The MAC address of the bridge. The bridge identifier is used as a
tie breaker in the selection of the root bridge when two or more
bridges have the same bridge priority value. This value cannot be
changed.
Root Bridge
Indicates the MAC address of the switch in the network that is
currently functioning as the root bridge for all the switches in the
spanning tree domain. The MAC address is determined by the
spanning tree protocol. This parameter provides an easy way for a
network manager to determine which switch in the network is
functioning as the root bridge. This is a read-only parameter.