1-10
z MSTP supports mapping VLANs to MST instances by means of a VLAN-to-instance mapping table.
MSTP introduces “instance” (integrates multiple VLANs into a set) and can bind multiple VLANs to
an instance, thus saving communication overhead and improving resource utilization.
z MSTP divides a switched network into multiple regions, each containing multiple spanning trees
that are independent of one another.
z MSTP prunes a ring network into a network with tree topology, preventing packets from being
duplicated and forwarded in a network endlessly. Furthermore, it offers multiple redundant paths
for forwarding data, and thus achieves load balancing for forwarding VLAN data.
z MSTP is compatible with STP and RSTP.
Basic MSTP Terminologies Figure 1-4 illustrates basic MSTP terms (assuming that MSTP is enabled on every device in this figure).
Figure 1-4 Basic MSTP terminologies
MST region
A multiple spanning tree region (MST region) comprises multiple physically-interconnected
MSTP-enabled devices and the corresponding network segments connected to these devices. These
devices have the same region name, the same VLAN-to-MSTI mapping configuration and the same
MSTP revision level.
A switched network can contain multiple MST regions. You can group multiple devices into one MST
region by using the corresponding MSTP configuration commands.
As shown in Figure 1-4, all the devices in region A0 are of the same MST region-related configuration,
including:
z Region name
z VLAN-to-MSTI mapping (that is, VLAN 1 is mapped to MSTI 1, VLAN 2 is mapped to instance 2,
and the other VLANs are mapped to CIST.)
z MSTP revision level (not shown in Figure 1-4)