MSTP Configuration
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19.1.1.2
Operations between MST Regions
If there are multiple regions or legacy 802.1D bridges within the network, MSTP
establishes and maintains the CST, which includes all MST regions and all legacy STP
bridges in the network. The MST instances combine with the IST at the boundary of the
region to become the CST.
The MSTI is only valid within its MST region. An MSTI has nothing to do with MSTIs in
other MST regions. The bridges in a MST region receive the MST BPDU of other regions
through Boundary Ports. They only process CIST related information and abandon MSTI
information.
19.1.2
Port Roles
The MSTP bridge assigns a port role to each port which runs MSTP.
CIST port roles: Root Port, Designated Port, Alternate Port and Backup Port
On top of those roles, each MSTI port has one new role: Master Port.
The port roles in the CIST (Root Port, Designated Port, Alternate Port and Backup
Port) are defined in the same ways as those in the RSTP.
19.1.3
MSTP Load Balance
In a MSTP region, VLANs can by mapped to various instances. That can form various
topologies. Each instance is independent from the others and each distance can have its
own attributes such as bridge priority and port cost etc. Consequently, the VLANs in
different instances have their own paths. The traffic of the VLANs are load-balanced.
19.2
MSTP Configuration Task List
MSTP configuration task list:
1. Enable the MSTP and set the running mode
2. Configure instance parameters
3. Configure MSTP region parameters
4. Configure MSTP time parameters
5. Configure the fast migrate feature for MSTP
6. Configure the format of port packet
7. Configure the spanning-tree attribute of port
8. Configure the snooping attribute of authentication key
9. Configure the FLUSH mode once topology changes