H3C S3610-28F, Руководство по эксплуатации

Страница: 220 / 1547

Operation Manual – MSTP
H3C S3610&S5510 Series Ethernet Switches
Chapter 1 MSTP Configuration
1-14
2) VLAN-to-instance mapping table
As an attribute of an MST region, the VLAN-to-instance mapping table describes the
mapping relationships between VLANs and MST instances. In Figure 1-4 , for example,
the VLAN-to-instance mapping table of region A0 describes that the same region name,
the same VLAN-to-instance mapping (VLAN 1 is mapped to MST instance 1, VLAN 2 to
MST instance 2, and the rest to CIST). MSTP achieves load balancing by means of the
VLAN-to-instance mapping table.
3) IST
Internal spanning tree (IST) is a spanning tree that runs in an MST region
ISTs in all MST regions and the common spanning tree (CST) jointly constitute the
common and internal spanning tree (CIST) of the entire network. An IST is a section of
the CIST in the given MST region.
In Figure 1-4 , for example, the CIST has a section in each MST region, and this section
is the IST in the respective MST region.
4) CST
The CST is a single spanning tree that connects all MST regions in a switched network.
If you regard each MST region as a “device”, the CST is a spanning tree calculated by
these devices through STP or RSTP. For example, the red lines in Figure 1-4 describe
the CST.
5) CIST
Jointly constituted by ISTs and the CST, the CIST is a single spanning tree that
connects all devices in a switched network.
In Figure 1-4 , for example, the ISTs in all MST regions plus the inter-region CST
constitute the CIST of the entire network.
6) MSTI
Multiple spanning trees can be generated in an MST region through MSTP, one
spanning tree being independent of another. Each spanning tree is referred to as a
multiple spanning tree instance (MSTI). In Figure 1-4 , for example, multiple spanning
tree can exist in each MST region, each spanning tree corresponding to a VLAN. These
spanning trees are called MSTIs.
7) Regional root bridge
The root bridge of the IST or an MSTI within an MST region is the regional root bridge of
the MST or that MSTI. Based on the topology, different spanning trees in an MST region
may have different regional roots.
For example, in region D0 in Figure 1-4 , the regional root of instance 1 is device B,
while that of instance 2 is device C.
8) Common root bridge
The common root bridge is the root bridge of the CIST.