Product guide

Spanning-Tree Operation
802.1s Multiple Spanning Tree Protocol (MSTP)
Caution Spanning tree interprets a switch mesh as a single link (meshing is supported
on the 5300xl, 3400cl and 6400cl switches only). Because the switch automat-
ically gives faster links a higher priority, the default MSTP parameter settings
are usually adequate for spanning tree operation. Also, because incorrect
MSTP settings can adversely affect network performance, you should not
change the MSTP settings from their default values unless you have a strong
understanding of how spanning tree operates.
In a mesh environment, the default MSTP timer settings (Hello Time and
Forward Delay) are usually adequate for MSTP operation. Because a packet
crossing a mesh may traverse several links within the mesh, using smaller-
than-default settings for the MSTP Hello Time and Forward Delay timers can
cause unnecessary topology changes and end-node connectivity problems.
For MSTP information beyond what is provided in this manual, refer to the
IEEE 802.1s standard.
MSTP Structure
MSTP maps active, separate paths through separate spanning tree instances
and between MST regions. Each MST region comprises one or more MSTP
switches. Note that MSTP recognizes an STP or RSTP LAN as a distinct
spanning-tree region.
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