Allied Telesis AT-S62 - Manual (Page 496)

Chapter 22: Spanning Tree and Rapid Spanning Tree Protocols
496 Section IV: Spanning Tree Protocols
The bridge hello time, bridge forwarding, and bridge max age
parameters will have two values if STP is enabled on the switch (for
example, Bridge Forwarding .. 15/15). The first number is the
configured value on the switch for the parameter and the second is the
value the switch obtained from the root bridge and is actually using for
the parameter. The switch displays only the configured values for
these parameters if spanning tree is not activated on the switch.
2. Adjust the bridge STP settings as needed. The parameters are
described below.
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 11, Bridge Priority Value Increments on page 485.
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))