Zte ZXR10 2910E-PS Configuration Manual page 79

Rapid Spanning Tree Protocol (RSTP) is on the basis of common STP, added with the
mechanism that the port state can be rapidly changed from Blocking to Forwarding, which
increases the topology convergence speed.
Multiple Spanning Tree Protocol (MSTP) is on the basis of RSTP and STP, added with
the forwarding processing of frames with VLAN ID. The whole network topology structure
can be planned into a Common and Internal Spanning Tree (CIST), which is divided into
Common Spanning Tree (CST) and Internal Spanning Tree (IST).
Many devices enabling MSTP construct MST area in switching network. When the devices
satisfy the following conditions, they can be considered to exist in a MST area. A switching
network can cover many MST areas. User can divide the switches into a MST area by
using MSTP commands.
l
Same area name.
l
Same reversion level.
l
Same mapping relationship between VLAN and instance.
l Switches should be connected directly.
There are many spanning trees can be configured in each MSTP area, and they are
independent each other. Each spanning tree is Internal Spanning Tree (IST), and it can
be called as Multiple Spanning Tree Instance (MSTI). Common Spanning Tree connect
all MST areas in switching network. A MST area can be considered as a switch, CST is
a spanning tree which is generated by STP and RSTP protocol calculation. All ISTs and
CSTs are called as Common and Internal Spanning Tree (CIST). CIST is a single spanning
tree to connect all switches.
In this MSTP topology structure, an IST can serve as a single bridge (switch). In this way,
CTS can serve as an RSTP for the interaction of configuration information (BPDU). Multiple
instances can be created in an IST area and these instances are valid only in this area.
An instance is equivalent to an RSTP, except that the instance needs to perform BPDU
interaction with bridges outside this area.
MSTP topological structure is shown as
SJ-20120409144109-002|2012-07-02(R1.0)
Chapter 4 Service Configuration
Figure 4-9.
4-33
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