Huawei Quidway S3000 Series Operation Manual page 26

Operation Manual - STP
Quidway S3000 Series Ethernet Switches
CIST: Common and Internal
MSTI: Multiple Spanning
Region A0
vlan 1 mapping to Instance 1, region root B
vlan 3 mapped to Instance 2
Other vlans mapped to CIST
Figure2-1 Basic MSTP concepts
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 Figure2-1).
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.
Spanning Tree
Tree Instance
BPDU
A
CST: Common
Spanning Tree
B
C
D
, region root C
Region A0
vlan 1 mapped to Instance 1
vlan 2 mapped to Instance 2
Other vlans mapped to CIST
BPDU
BPDU
Region B0
vlan 1 mapped to Instance 1
vlan 2 mapped to Instance 2
Other vlans mapped to CIST
Region C0
vlan 1 mapped to Instance 1
vlan 2 and 3 mapped to Instance 2
Other vlans mapped to CIST
2-2
Chapter 1 RSTP Configuration