3com DUA1750-2BAA01 Manual De Usuario

3Com Switch 8800 Configuration Guide 

Chapter 38  MSTP Region-configuration

 

38-1 

MSTP stands for Multiple Spanning Tree Protocol, which is compatible with Spanning 

Tree Protocol (STP) and Rapid Spanning Tree Protocol (RSTP).  

STP is not fast in state transition. Even on a point-to-point link or a edge port, it has to 

take an interval twice as long as forward delay before the port transits to the forwarding 

state. 

RSTP converges fast, but has the following drawback like STP: all the network bridges 

in a LAN share one spanning tree and the redundant links cannot be blocked based on 

VLANs. Packets of all VLANs are forwarded along one spanning tree. 

MSTP makes up for the drawback of STP and RSTP. It not only converges fast, but also 

allows the traffic of different VLANs to be distributed along their respective paths, which 

provides a better load-balance mechanism for the redundant links.  

MSTP keeps a VLAN mapping table to associate VLANs with their spanning trees. 

Using MSTP, you can divide one switching network into multiple regions, each of which 

can have multiple spanning trees with each one independent of others. MSTP prunes 

the ring network into a loopfree tree to avoid the generation of loops and infinite 

circulations. It also provides multiple redundant paths for data forwarding to implement 

the load-balance mechanism of the VLAN data. 

There are 4 MST regions in Figure 38-1. Each region consists of four switches, all of 

which run MSTP. The following introduces the concept of MSTP with the help of this 

figure.