Huawei quidway s7700 - Page 441

Figure 9-4 MSTP network
CIST Root
A0
B0
C0
D0
Region Root
Region Root
Region Root
CST
IST
On the network shown in Figure 9-4, the CIST root is the root bridge of a CIST. The CIST
root is a device in A0.
l CST
A Common Spanning Tree (CST) connects all the MST regions on a switching network.
Each MST region can be considered a node. A CST is calculated by using STP or RSTP
based on all the nodes.
As shown in Figure 9-4, the MST regions are connected to form a CST.
l IST
An IST resides within an MST region.
An IST is a special MSTI with the MSTI ID of 0, called MSTI 0.
An IST is a segment of the CIST in an MST region.
As shown in Figure 9-4, the switching devices in an MST region are connected to form an
IST.
l CIST
A CIST, calculated by using STP or RSTP, connects all the switching devices on a switching
network.
As shown in Figure 9-4, the ISTs and the CST form a complete spanning tree, that is, CIST.
l SST
A Single Spanning Tree (SST) is formed in either of the following situations:
Quidway S7700 Smart Routing Switch
Configuration Guide - Ethernet 9 MSTP Configuration
Issue 01 (2011-07-15) Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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