Configuring Multiple Spanning Tree; Information About Mst; Mst Overview - Cisco Nexus 3000 series Configuration Manual

Configuring Multiple Spanning Tree

Multiple Spanning Tree (MST), which is the IEEE 802.1s standard, allows you to assign two or more VLANs
to a spanning tree instance. MST is not the default spanning tree mode; Rapid per VLAN Spanning Tree
(Rapid PVST+) is the default mode. MST instances with the same name, revision number, and
VLAN-to-instance mapping combine to form an MST region. The MST region appears as a single bridge
to spanning tree configurations outside the region. MST fails over to IEEE 802.1D Spanning Tree Protocol
(STP) when it receives an 802.1D message from a neighboring switch.
Spanning tree is used to refer to IEEE 802.1w and IEEE 802.1s. If the text is discussing the IEEE 802.1D
Note
Spanning Tree Protocol, 802.1D is stated specifically.
This chapter describes how to configure MST on Cisco Nexus 3000 Series switches. It contains the following
sections:
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Information About MST

MST Overview

You must enable MST; Rapid PVST+ is the default spanning tree mode.
Note
MST maps multiple VLANs into a spanning tree instance, with each instance having a spanning tree topology
independent of other spanning tree instances. This architecture provides multiple forwarding paths for data
traffic, enables load balancing, and reduces the number of STP instances required to support a large number
of VLANs.
Information About MST, page 101
Configuring MST, page 109
Verifying MST Configurations, page 127
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