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MSTI calculation
Within an MST region, MSTP generates different MSTIs for different VLANs based on the
VLAN-to-instance mappings. For each spanning tree, MSTP performs a separate calculation process
similar to spanning tree calculation in STP. For more information, see "
Calculation process of the STP
In MSTP, a VLAN packet is forwarded along the following paths:
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Within an MST region, the packet is forwarded along the corresponding MSTI.
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Between two MST regions, the packet is forwarded along the CST.
MSTP implementation on devices
MSTP is compatible with STP and RSTP. Devices that are running MSTP and that are used for spanning
tree calculation can identify STP and RSTP protocol packets.
In addition to basic MSTP functions, the following functions are provided for ease of management:
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Root bridge hold
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Root bridge backup
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Root guard
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BPDU guard
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Loop guard
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TC-BPDU guard
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Port role restriction
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TC-BPDU transmission restriction
Protocols and standards
MSTP is documented in the following protocols and standards:
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IEEE 802.1d,
Media Access Control (MAC) Bridges
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IEEE 802.1w,
Part 3: Media Access Control (MAC) Bridges—Amendment 2: Rapid Reconfiguration
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IEEE 802.1s,
Virtual Bridged Local Area Networks—Amendment 3: Multiple Spanning Trees
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IEEE 802.1Q-REV/D1.3,
Media Access Control (MAC) Bridges and Virtual Bridged Local Area
Networks —Clause 13: Spanning tree Protocols
Spanning tree configuration task lists
Before configuring a spanning tree, complete the following tasks:
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Determine the spanning tree protocol to be used (STP, RSTP, PVST, or MSTP).
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Plan the device roles (the root bridge or leaf node).
When you configure spanning tree protocols, follow these restrictions and guidelines:
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If both MVRP and a spanning tree protocol are enabled on a device, MVRP packets are forwarded
along MSTIs. To advertise a specific VLAN within the network through MVRP, make sure this VLAN
is mapped to an MSTI when you configure the VLAN-to-instance mapping table. For more
information about MVRP, see "
