User Manual

Chapter 20: Spanning Tree, Rapid Spanning Tree, and Multiple Spanning Tree Protocols
280 Section IV: Spanning Tree Protocols
Note
The Defaults button returns all RSTP settings to the default settings.
2. Adjust the parameters are desired. The parameters are defined below.
1 - Force Version
This selection determines whether the bridge will operate with RSTP
or in an STP-compatible mode. If you select RSTP, the bridge
operates all ports in RSTP, except for those ports that receive STP
BPDU packets. If you select Force STP Compatible, the bridge
operates in RSTP, using the RSTP parameter settings, but it sends
only STP BPDU packets out the ports.
2 - Bridge Priority
The priority number for the bridge. This number is used in determining
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 off-line, 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 7, Bridge Priority Value Increments on page 275.
3 - 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.
4 - 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. This setting applies only to ports
running in the STP-compatible mode.
5 - 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
20, all bridges delete current configuration messages after 20
seconds. This parameter can be from 6 to 40 seconds. The default is
20 seconds.
In selecting a value for maximum age, the following must be observed:
MaxAge must be greater than (2 x (HelloTime + 1)).