3com S7906E Installation Instruction
1-11
Basic Concepts in MSTP
Figure 1-4
Basic concepts in MSTP
CST
Region A0
VLAN 1 mapped to instance 1
VLAN 2 mapped to instance 2
Other VLANs mapped to CIST
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
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
VLAN 1 mapped to instance 1
VLAN 2 and 3 mapped to
instance 2
Other VLANs mapped to CIST
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
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
BPDU
BPDU
BPDU
C
D
B
A
Assume that all devices in
are running MSTP. This section explains some basic concepts of
MSTP.
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:
network segments among them. These devices have the following characteristics:
z
All are MSTP-enabled,
z
They have the same region name,
z
They have the same VLAN-to-instance mapping configuration,
z
They have the same MSTP revision level configuration, and
z
They are physically linked with one another.
For example, all the devices in region A0 in
have the same MST region configuration:
z
The same region name,
z
The same VLAN-to-instance 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
MSTI 2, and the rest to the common and internal spanning tree (CIST, that is, MSTI 0), and
z
The same MSTP revision level (not shown in the figure).
Multiple MST regions can exist in a switched network. You can use an MSTP command to assign
multiple devices to the same MST region.
multiple devices to the same MST region.