User guide

Chapter 19: Multiple Spanning Tree Protocol
298 Section IV: Spanning Tree Protocols
Configure the following parameters as necessary.
Force Version
This selection determines whether the bridge operates with MSTP or
in an STP-compatible mode. If you select MSTP, the bridge operates
all ports in MSTP, except those ports that receive STP or RSTP BPDU
packets. If you select Force STP Compatible, the bridge uses its
MSTP parameter settings, but sends only STP BPDU packets from the
ports. The default is MSTP.
Note
Selecting the STP-compatible mode deletes all spanning tree
instances on the switch.
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. This value is active only if the bridge is
selected as the root bridge of the network.
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 of the links may have adapted to
the change, possibly resulting in a network loop. The range is from 4 to
30 seconds. The default is 15 seconds. This setting applies only to
ports running in the STP-compatible mode.
Configuration Name
The name of the MSTP region. The range is 0 (zero) to 32
alphanumeric characters in length. The name, which is case sensitive,
must be the same on all bridges in a region. Examples of a
configuration name include Sales Region and Production Region.
Bridge Max Age
The length of time after which stored bridge protocol data units
(BPDUs) are deleted by the bridge. This parameter applies only if the
bridged network contains an STP or RSTP single-instance spanning
tree. Otherwise, the bridges use the Max Hop counter to delete
BPDUs.
All bridges in a single-instance 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, the following must be observed:
MaxAge must be greater than (2 x (HelloTime + 1))
MaxAge must be less than (2 x (ForwardingDelay - 1))