A10E/A28E/A28F Configuration Guide
Bpdus send: 279 (TCN<0> Config<279> RST<0> MST<0>)
Bpdus received:6 (TCN<6> Config<0> RST<0> MST<0>)
Instance PortState PortRole PortCost(admin/oper) PortPriority
-----------------------------------------------------------------
0 discarding disabled 10/10 0
7.5 MSTP
7.5.1 Introduction
Multiple Spanning Tree Protocol (MSTP) is defined by IEEE 802.1s. Recovering the
disadvantages of STP and RSTP, the MSTP realizes fast convergence and distributes different
VLAN flow following its own path to provide an excellent load sharing mechanism.
MSTP divides a switch network into multiple domains, called MST domain. Each MST
domain contains several spanning trees but the trees are independent one another. Each
spanning tree is called a Multiple Spanning Tree Instance (MSTI).
MSTP protocol introduces Common Spanning Tree (CST) and Internal Spanning Tree (IST)
concepts. CST refers to take MST domain as a whole to calculate and generate a spanning tree.
IST means to generate spanning tree in internal MST domain.
Compared with STP and RSTP, MSTP also introduces total root (CIST Root) and domain root
(MST Region Root) concepts. The total root is a global concept; all switches running
STP/RSTP/MSTP can only have one total root, which is the CIST Root. The domain root is a
local concept, which is relative to an instance in a domain. As shown below, all connected
devices only have one total root, and the number of domain root contained in each domain is
associated with the number of instances.
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