H3C S3100-52P Operation Manual page 258

Operation Manual – MSTP
H3C S3100-52P Ethernet Switch
III. VLAN-to-MSTI mapping table
A VLAN-to-MSTI mapping table is maintained for each MST region. The table is a
collection of mappings between VLANs and MSTIs. For example, in
VLAN-to-MSTI mapping table of region A0 contains these mappings: VLAN 1 to MSTI 1;
VLAN 2 to MSTI 2, and other VLANs to CIST. In an MST region, load balancing is
implemented according to the VLAN-to-MSTI mapping table.
IV. IST
An internal spanning tree (IST) is a spanning tree in an MST region.
ISTs together with the common spanning tree (CST) form the common and internal
spanning tree (CIST) of the entire switched network. An IST is a special MSTI; it is a
branch of CIST in the MST region.
In Figure
V. CST
A CST is a single spanning tree in a switched network that connects all MST regions in
the network. If you regard each MST region in the network as a "switch", then the CST
is the spanning tree generated by STP or RSTP running on the "switches".
VI. CIST
A CIST is the spanning tree in a switched network that connects all switches in the
network. It comprises the ISTs and the CST.
In Figure
form the CIST.
VII. Region root
A region root is the root of the IST or an MSTI in an MST region. Different spanning
trees in an MST region may have different topologies and thus have different region
roots.
In region D0 shown in
root of MSTI 2 is switch C.
VIII. Common root bridge
The common root bridge is the root of the CIST. The common root bridge of the network
shown in
IX. Port role
MSTP calculation involves the following port roles: root port, designated port, master
port, region boundary port, alternate port, and backup port.
A root port is used to forward packets to the root.
1-4, each MST region has an IST, which is a branch of the CIST.
1-4, the ISTs in the MST regions and the CST connecting the MST regions
Figure 1-4, the region root of MSTI 1 is switch B, and the region
Figure 1-4 is a switch in region A0.
1-14
Chapter 1 MSTP Configuration
Figure 1-4, the