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In MSTP, a VLAN packet is forwarded along the following paths:
•
Within an MST region, the packet is forwarded along the corresponding MSTI.
•
Between two MST regions, the packet is forwarded along the CST.
Implementation of MSTP on routers
MSTP is compatible with STP and RSTP. STP and RSTP protocol packets can be recognized by routers
running MSTP and used for spanning tree calculation.
In addition to basic MSTP functions, the following functions are provided for ease of management:
•
Root bridge hold
•
Root bridge backup
•
Root guard
•
BPDU guard
•
Loop guard
•
TC-BPDU guard
•
BPDU drop
•
Support for hot swapping of interface cards and active/standby changeover.
Protocols and standards
The spanning tree protocols are documented in the following standards:
•
IEEE 802.1d:
Media Access Control (MAC) Bridges
•
IEEE 802.1w:
Part 3: Media Access Control (MAC) Bridges—Amendment 2: Rapid Reconfiguration
•
IEEE 802.1s:
Virtual Bridged Local Area Networks—Amendment 3: Multiple Spanning Trees
Spanning tree configuration task list
Before configuring a spanning tree, you must determine the spanning tree protocol to be used (STP, RSTP,
or MSTP) and plan the device roles (the root bridge or leaf node).
Complete the following tasks to configure STP:
Task Remarks
Configuring the root
bridge
Setting the spanning tree mode
Required
Configure the router to work
in STP-compatible mode.
Configuring the root bridge or a secondary root
bridge
Optional
Configuring the device priority
Optional
Configuring the network diameter of a switched
network
Optional
Configuring spanning tree timers
Optional
Configuring the timeout factor
Optional
