Operation Manual - STP
Quidway S3500 Series Ethernet Switches Chapter 1 MSTP Region-configuration
Huawei Technologies Proprietary
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I. MST region
Multiple Spanning Tree Regions: A multiple spanning tree region contains several
physically and directly connected MSTP switches sharing the same region name,
VLAN-spanning tree mapping configuration, and MSTP revision level configuration,
and the network segments between them. There can be several MST regions on a
switching network. You can group several switches into a MST region, using MSTP
configuration commands. For details, refer to the operation manual in this chapter. For
example, MST region A0 in the network of figure2-1, the 4 switches in this region are
configured same region name, same vlan mapping table (VLAN1 map to instance 1,
VLAN 2 map to instance 2, other VLAN map to instance 0), same revision level (not
indicated in Figure 1-1).
II. VLAN mapping table
An attribute of MST region, is used for descript the mapping relationship of VLAN and
STI. For example, the VLAN mapping table of MST region A0 in figure2-1 is VLAN1
map to instance 1, VLAN 2 map to instance 2, other VLAN map to instance 0.
III. IST
Internal Spanning Tree (IST): The entire switching network has a Common and Internal
Spanning Tree (CIST). An MSTP region has an Internal Spanning Tree (IST), which is a
fragment of CIST. For example, every MST region in figure2-1 has an IST.
IV. CST
Common Spanning Tree (CST): Connects the spanning trees of all the MST region.
Taking every MST region as a “switch”, the CST can be regarded as their spanning tree
generated with STP/RSTP. For example, the red line indicates the CST in figure2-1.
V. CIST
CIST (Common and Internal Spanning Tree): A single spanning tree made of IST and
CST (Common Spanning Tree). CIST of figure2-1 is composed by each IST in every
MST region and the CST.
VI. MSTI
Multiple Spanning Tree Instance (MSTI): Multiple spanning trees can be generated with
MSTP in an MSTI and independent of one another. Such a spanning tree is called an
MSTI. Every MST region can have many STI called MSTI. These STI is related to
corresponding VLAN.
VII. Region root
The region root refers to the root of the IST and MSTI of the MST region. The spanning
trees in an MST region have different topology and their region roots may also be
different. In each MST region in Figure 1-1, every STI has its region root.
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