QTECH
Software Configuration Manual
15-193
MSTP features the following :
·
MSTP supports mapping VLANs to MST instances by means of a VLAN-to-instance mapping table.
·
MSTP divides a switched network into multiple regions, each containing multiple spanning trees that are
independent of one another.
·
MSTP prunes loop networks into a loop-free tree, thus avoiding proliferation and endless recycling of
packets in a loop network. In addition, it provides multiple redundant paths for data forwarding, thus
supporting load balancing of VLAN data in the data forwarding process.
·
MSTP is compatible with STP and RSTP.
15.1.2.2
Some concepts in MSTP
As shown in Figure 4, there are four multiple spanning tree (MST) regions, each made up of four switches
running MSTP. In light with the diagram, the following paragraphs will present some concepts of MSTP.
Figure 4 Basic concepts in MSTP
1) MST region
An MST region is composed of multiple devices in a switched network and 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.
In region A0 in Figure 4, for example, all the device have the same MST region configuration : the same
region name, the same VLAN-to-instance mapping (VLAN1 is mapped to MST instance 1, VLAN2 to MST instance
2, and the rest to the command and internal spanning tree (CIST). CIST refers to MST instance 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 group multiple
devices to the same MST region.
2) VLAN-to-instance mapping table
