H3C LS-3100-52P-OVS-H3 Operation Manual page 246

MSTP divides a switched network into multiple regions, each containing multiple spanning trees
that are independent of one another.
MSTP prunes a loop network into a loop-free tree, thus avoiding proliferation and endless cycling of
packets in a loop network. In addition, it provides multiple redundant paths for data forwarding, thus
supporting load balancing of VLAN data.
MSTP is compatible with STP and RSTP.
Basic concepts in MSTP
Figure 1-4 Basic concepts in MSTP
A
B
D
Region D0
VLAN 1 mapped to instance 1,
B as regional root bridge.
VLAN 2 mapped to instance 2，
C as regional root bridge.
Other VLANs mapped to CIST
Assume that all devices in
MSTP.
1) MST region
A multiple spanning tree region (MST region) consists of multiple devices in a switched network and the
network segments among them. These devices have the following characteristics:
All are MSTP-enabled,
They have the same region name,
They have the same VLAN-to-MSTI mapping configuration,
They have the same MSTP revision level configuration, and
They are physically linked with one another.
For example, all the devices in region A0 in
The same region name,
The same VLAN-to-MSTI mapping configuration (VLAN 1 is mapped to MSTI 1, VLAN 2 to MSTI 2,
and the rest to the common and internal spanning tree (CIST, that is, MSTI 0), and
The same MSTP revision level (not shown in the figure).
BPDU BPDU
CST
C
BPDU
Figure 1-4 are running MSTP. This section explains some basic concepts of
Figure 1-4
1-10
Region A0
VLAN 1 mapped to instance 1
VLAN 2 mapped to instance 2
Other VLANs mapped to CIST
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 2,3 mapped to instance 2
Other VLANs mapped to CIST
have the same MST region configuration: