What is Multiple Spanning Tree Protocol (MSTP)?

Multiple Spanning Tree Protocol

Multiple Spanning Tree Protocol (MSTP) is an algorithm that enables easy and full connectivity provided to any Virtual LAN (VLAN) across an Integrated Area Network.

  • MSTP uses Bridge Protocol Data Units (BPDUs) to transmit information to tree-related devices by identifying practical ways to prevent loopholes in the MSTI (Multiple Spanning Tree Instance) and CIST (Common and Internal Spanning Tree). This is done in the same way as the STP was designed, but without the need to enable support links and without the risk of bridge loops.

  • In addition, MSTP allows frames/packets allocated to different VLANs to take different routes within MST regions composed of LANs or MST Bridges, each based on an independent MSTI. These regions, along with other bridges and LANs, form one common Spanning Tree (CST).

  • By making a tree topology (open tree) of the entire blocked network with a single open path between the root of the tree and the leaf, the agreements of cleverly cut tree blocks block the network logs.

  • All other methods are forced to go into standby mode. The root of the tree is a network STA (spanning-tree algorithm) that you choose to use when finding a good path between network bridges and root bridges.

  • Frames follow the network to its final destination, leaf. The network section, or link between the bridges, is referred to as the tree branch. Designated bridges change those frames facing forward with an open STP tree.

MSTP Implementation

The following is a set of implementation questions that need to be implemented in theory −

  • Logical Topology Calculation – How can you create multiple STP (sensible topologies) in one body? Should we use more STP scenarios that send their BPDUs independently? If so, then how can we differentiate BPDUs for each period? VLAN tags cannot be used for that purpose, as STPs are no longer bound to VLANs.

  • Data Distribution – What process should be used to distribute VLAN to create map tables between switches? Should VLAN IDs be assigned to BPDUs with the correct number numbers?

  • Consistency check – How can you ensure that the VLAN mapping is compatible with every transition? That is, how would a switch know if another button was mapping VLAN X in the same situation?

Multiple Spanning Tree Instances (MSTI)

You may feel compelled to choose a group or group of VLANs that all use the same open tree since MSTP allows you to edit and map VLANs in different tree environments. MSTI is a term used to describe something like this.

STP or RSTP networks, on the other hand, have one example of an open network for the entire network, including all VLANs. The region may contain the following −

Internal Spanning-Tree Instance (IST)

This is an example of a default tree in any MST region. In this IST model, all VLANs have the same flexibility, which means there is only one transfer link between any two nodes. It also acts as a root switch for any VLAN configuration changes not provided by MSTI.

Unlike the IST, MSTI (Multiple Spanning Tree Instance) contains all the fixed VLANs assigned to them and must include at least one VLAN.

Benefits of Using MSTP

MSTP offers the following benefits −

  • Most VLANs are compliant with the Multiple Spanning Tree Protocol.

  • Multiple MSTP scenarios can be run on a single interface.

  • The combination of RSTP, MSTP, and VSTP can be configured as an edge port on MX and ACX routers.

Disadvantages of MSTP

MSTP has the following drawbacks −

  • If you use MSTIs and do not draw all VLANs on the IST, any changes you make, such as adding a new VLAN to the MSTI, will cause the CIST to reconnect.

  • Some agreements require compliance that MSTP does not offer.

  • MSTP requires a strong understanding of communication.