The Multiple Spanning Tree Protocol (MSTP) and algorithm, provides both simple and full connectivity assigned to any given Virtual LAN (VLAN) throughout a Bridged Local Area Network. MSTP uses BPDUs to exchange information between spanning-tree compatible devices, to prevent loops in each MSTI (Multiple Spanning Tree Instances) and in the CIST (Common and Internal Spanning Tree), by selecting active and blocked paths. This is done as well as in STP without the need of manually enabling backup links and getting rid of bridge loops danger.
Moreover, MSTP allows frames/packets assigned to different VLANs to follow separate paths, each based on an independent MSTI, within MST Regions composed of LANs and or MST Bridges. These Regions and the other Bridges and LANs are connected into a single Common Spanning Tree (CST).
Multiple Spanning Tree Protocol (MSTP), initially defined in IEEE 802.1s and later included in IEEE 802.1Q, supports mapping of multiple VLANs onto a single spanning-tree instance. This reduces the number of spanning-tree instances required in a switched network with many VLANs.
MSTP divides an entire Layer 2 network into multiple MST regions,
which are connected by a calculated CST. Inside an MST region, multiple
spanning trees, called MSTIs, are calculated. Among these MSTIs, MSTI 0
is the IST. Like STP, MSTP uses configuration BPDUs to calculate
spanning trees.
For more information:
https://support.huawei.com/enterprise/en/doc/EDOC1100125472/b5b44da9/overview-of-mstp
https://support.huawei.com/enterprise/en/doc/EDOC1000178168/59fcb06f/mstp-configuration
