Figure 9-6 Networking diagram of MSTP multi-process
SwitchA
SwitchB
SwitchC
PE1
PE2
CE
CE
CE
CE
CE
CE
Instance1:VLAN2~100
Instance2:VLAN101~200
Process 1
Process 2
Process 3
Instance3:VLAN201~300
Ring2
Ring1 Ring3
On the network shown in Figure 9-6, multiple Layer 2 rings, Ring 1, Ring 2, and Ring 3
exists. STP must be enabled on these rings to prevent loops. SwitchA and SwitchB are
connected to multiple access rings and these rings are isolated from each other and do not
need intercommunication. STP then will not calculate out one spanning tree for all these
access rings. Instead, STP on each access ring calculates the trees independently.
MSTP supports multiple spanning tree instances (MSTIs) only when all devices support
MSTP and the devices are configured with the same MST region. In the networking, the
CEs connected to switching devices, however, support only STP/RSTP. According to
MSTP, switching devices consider that they are in different regions with CEs after receiving
STP/RSTP messages sent from the CEs. Therefore, only one spanning tree is calculated
for the ring formed by switching devices and CEs and the access rings are not independent
of each other.
In this case, MSTP multi-process can be used. Multiple MSTP processes can be configured
on SwitchA and SwitchB. Each MSTP process has the same function and supports MSTIs.
Each MSTP process corresponds to one access ring.
After MSTP multi-process is enabled, each MSTP process can manage some interfaces on
a device. That is, Layer 2 interfaces on the device are divided and managed by multiple
MSTP processes. Each MSTP process runs the standard MSTP.
NOTE
CEs that support MSTP can also be configured with MSTP multi-process.
After a device properly starts, there is a default MSTP process with the ID 0. MSTP configurations
in the system view and interface view both belong to this process.
l Share link
As shown in Figure 9-6, the link between SwitchA and SwitchB is a Layer 2 link running
MSTP. The share link between SwitchA and SwitchB is different from the links connecting
Quidway S7700 Smart Routing Switch
Configuration Guide - Ethernet 9 MSTP Configuration
Issue 01 (2011-07-15) Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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