Basic Concepts In Mstp - 3Com 4510G Configuration Manual

Basic Concepts in MSTP

Figure 4-4 Basic concepts in MSTP
B
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.
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-instance 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-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
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.
BPDU
A
CST
C
D
Figure 4-4 are running MSTP. This section explains some basic concepts of
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
Figure 4-4 have the same MST region configuration:
4-11