Figure 8-2 Spanning Trees In An Mst Region - Huawei Quidway S9300 Configuration Manual

Quidway S9300 Terabit Routing Switch
Configuration Guide - Ethernet
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MSTP
The IEEE 802.1S standard issued in 2002 defines MSTP.
MSTP is compatible with STP and RSTP and rectifies the defects of STP and RSTP. An MSTP
network converges fast and provides redundant paths for data forwarding. In addition, the MSTP
network implements load balancing among VLANs.
MSTP divides a switching network into multiple regions, each of which has multiple spanning
trees independent of each other. Each spanning tree is called a multiple spanning tree instance
(MSTI) and each region is called a multiple spanning tree (MST) region.
MSTP associates VLANs with MSTIs through a VLAN mapping table.
MSTP is applied to the LAN, as shown in
in Figure

Figure 8-2 Spanning trees in an MST region

Host C
(VLAN3)
Host B
(VLAN2)
Two spanning trees are generated through calculation:
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Issue 03 (2009-08-20)
Host A and Host B belong to VLAN 2. The link between S9300B and S9300E is blocked
and the link between S9300C and S9300F does not permit packets from VLAN 2 to pass
through. Therefore, Host A and Host B cannot communicate with each other.
NOTE
Each VLAN can be associated with only one MSTI, that is, data of the same VLAN can be transmitted in
only one MSTI. One MSTI, however, may be associated with multiple VLANs.
8-2.
S9300A
VLAN3
S9300B
VLAN2
S9300C
MSTI1 (root switch: S9300D)
MSTI2 (root switch: S9300F)
In MSTI 1, S9300D functions as the root switch to forward packets of VLAN 2.
In MSTI 2, S9300F functions as the root switch to forward packets of VLAN 3.
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Figure 8-2, and then the MSTI is generated, as shown
VLAN3
VLAN2
VLAN2
VLAN3
VLAN3
VLAN2 --> MSTI1
VLAN3 --> MSTI2
8 MSTP Configuration
S9300D
VLAN2
VLAN2
S9300E
VLAN2
VLAN3
VLAN3
S9300F
Host A
(VLAN2)
Host D
(VLAN3)
8-3