Multiple Spanning Tree Protocol

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 bridge protocol data unit (BPDUs) to exchange information between spanning-tree compatible devices, to prevent loops in each Multiple Spanning Tree instance (MSTI) and in the common and internal spanning tree (CIST), by selecting active and blocked paths. This is done as well as in Spanning Tree Protocol (STP) without the need of manually enabling backup links and getting rid of switching loop 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 local area networks (LANs) and MST bridges. These regions and the other bridges and LANs are connected into a single common spanning tree (CST).