Multiple spanning tree protocol

Updated: June 15, 2026

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Provides an overview of Multiple Spanning Tree Protocol functionality and outlines MSTP instance mapping and load balancing techniques for efficient network segmentation and traffic optimization.

A multiple spanning tree protocol (MSTP) is a Spanning Tree Protocol (STP) variant that

allows you to configure each spanning tree instance independently
lets you select different root bridges or loop-free paths for each spanning tree, and
enables blocking or unblocking physical interfaces for specific spanning tree instances.

You can configure the parameters for each spanning tree separately. This means you can choose different network devices as the root bridge or select distinct paths to form the loop-free topology. Therefore, you can block a given physical interface for some spanning trees and unblock it for others.

Feature History Table


Feature Name	Release Information	Feature Description
Multiple Spanning Tree Protocol	Release 24.4.1	Introduced in this release on: Fixed Systems (8700) (select variants only) The MSTP functionality is now extended to the Cisco 8712-MOD-M routers.
Multiple Spanning Tree Protocol	Release 24.3.1	Introduced in this release on: Fixed Systems (8200 [ASIC: Q200, P100], 8700 [ASIC: P100])(select variants only); Modular Systems (8800 [LC ASIC: Q100, Q200, P100])(select variants only) *The MSTP functionality is now extended to: 8212-48FH-M 8711-32FH-M 88-LC1-52Y8H-EM 88-LC1-12TH24FH-E
Multiple Spanning Tree Protocol	Release 24.2.11	Introduced in this release on: Modular Systems (8800 [LC ASIC: P100]) (select variants only) The Multiple Spanning Tree Protocol (MSTP) enhances network efficiency by allowing the creation of multiple, independent spanning trees over the same physical network. This flexibility enables customized configuration of parameters for each spanning tree, selection of different root bridges or paths, and the ability to block or unblock specific physical interfaces for different trees. This functionality is extended to routers with the 88-LC1-36EH line cards.

MSTP instance mapping and load balancing

MSTP allows you to partition VLANs among multiple spanning tree instances. By assigning different VLAN ranges to separate spanning tree instances, you can distribute data traffic across available redundant links to achieve load balancing.

A typical VLAN-to-instance mapping might include:

VLANs 1-100 assigned to spanning tree instance 1
VLANs 101-200 assigned to spanning tree instance 2
VLANs 201-300 assigned to spanning tree instance 3

Since each spanning tree instance has its own active topology and uses different links, data traffic is divided among the available link paths based on VLAN assignment. This approach balances network traffic and optimizes link utilization.

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