Multiple Spanning Tree Protocol (MSTP)
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Industrial Communications Handbook
By Mick Crabtree
Chapter 10: Multiple Spanning Tree Protocol (MSTP)
Despite the convergence speed advantages offered by RSTP over STP, there are still several drawbacks.
The first lies in the fact that both RSTP and STP are based on the deployment of a single spanning tree which, in a large switched network, causes a relatively long convergence time.
Secondly, by adopting only a single spanning tree, all the VLANs in the network share the same one. This can lead to problems in ensuring that data communications in each Virtual Local Area Network (VLAN) are carried out along the spanning tree.
Finally, blocked links do not forward traffic and do not, therefore, participate in load balancing, which can lead to inefficient use of bandwidth.
These obstacles are overcome in a system called Multiple Spanning Tree Protocol (MSTP).
Like RSTP, MSTP allows for rapid port state transition and is backwards compatible with STP and RSTP.