Configuring Fast Spanning Tree
Page 17-35
Truncating Tree Timing & Speedy Tree Protocol
Two additional enhancements are also included with the Fast Spanning Tree feature for
improved performance: Truncating Tree Timing and Speedy Tree Protocol.
Truncating Tree Timing
Truncating Tree Timing allows Designated Ports attached to Point-to-Point links to change to
Forwarding mode faster, by utilizing two extra bits in the Configuration BPDU for
communication between neighboring bridges. This enhancement promotes quicker
restoration of service between communicating stations and reduced flooding of traffic during
relearning of station location information.
Speedy Tree Protocol
Speedy Tree Protocol significantly improves reconfiguration performance by allowing inferior
information sent by the designated bridge for each LAN to be accepted, rather than timed out.
Additionally, information previously received expires immediately on link failure. In both
cases, spanning tree recomputation occurs, which can cause changes in both root and
designated ports.
Configuring Truncating Tree Timing & Speedy Tree Protocol
Both Truncating Tree Timing and Speedy Tree Protocol are enabled by default. These features
are configured by editing the following lines in the command file (mpx.cmd):
truncatingSt=1
speedySt=1
To disable the Truncating Tree Timing feature, change the numeric entry for truncatingSt from
1 to 0. (To re-enable the feature, change the numeric entry back to 1.)
To disable the Speedy Tree Protocol feature, change the numeric entry for
speedySt from 1 to
0. (To re-enable the feature, change the numeric entry back to 1.)
♦ Important Note ♦
Do not attempt to edit the command file (
mpx.cmd)
unless you have had significant experience working
with files of this type. For additional information, see
Editing Text Files in Chapter 7, “Managing Files.”
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