User guide

Chapter 18: Spanning Tree and Rapid Spanning Tree Protocols
278 Section IV: Spanning Tree Protocols
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 Delay
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.
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.
In selecting a value for maximum age, the following rules must be
observed:
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.
Table 5. Bridge Priority Value Increments
Increment
Bridge
Priority
Increment
Bridge
Priority
0 0 8 32768
1 4096 9 36864
2 8192 10 40960
3 12288 11 45056
4 16384 12 49152
5 20480 13 53248
6 24576 14 57344
7 28672 15 61440