The IEEE Multiple Spanning Tree Protocol (MST) is in essence an extension of the Rapid Spanning Tree Protocol (RSTP). MST allows multiple spanning trees to coexist on the same bridged network. A group of VLANs can be mapped to its own independent instance of spanning tree, this allows for design flexibility and better resource utilizaton.
MST was originally defined in IEEE 802.1s, and it is based on Cisco’s Multiple Instances Spanning Tree Protocol (MSTIP). MST uses the same BPDU format as RSTP, therefore it is backward compatible with both STP and RSTP.
In order to understand MST, we must first define its components:
- MST Region: A group of Bridges with identical MST Configuration Identifiers
- Multiple Spanning Tree Instance(MSTI): Independent Spanning Tree topology defined within an MST Region
- MST Configuration Identifier: The MST region name, revision number, and VLAN to MSTI mappings
- Internal Spanning Tree(IST): Extends the CST inside an MST…
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