Cisco Systems N3KC3064TFAL3 manual Configuring Multiple Spanning Tree, Information About MST

C H A P T E R 9

Configuring Multiple Spanning Tree

This chapter contains the following sections:

•Information About MST, page 89

•Configuring MST, page 97

•Verifying MST Configurations, page 112

Information About MST

MST Overview

Note Spanning tree is used to refer to IEEE 802.1w and IEEE 802.1s. If the text is discussing the IEEE 802.1D Spanning Tree Protocol, 802.1D is stated specifically.

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.

MST provides rapid convergence through explicit handshaking as each MST instance uses the IEEE 802.1w standard, which eliminates the 802.1D forwarding delay and quickly transitions root bridge ports and designated ports to the forwarding state.

MAC address reduction is always enabled while you are using MST. You cannot disable this feature.

MST improves spanning tree operation and maintains backward compatibility with these STP versions:

•Original 802.1D spanning tree

•Rapid per-VLAN spanning tree (Rapid PVST+)

IEEE 802.1w defined the Rapid Spanning Tree Protocol (RSTP) and was incorporated into IEEE 802.1D.

•IEEE 802.1s defined MST and was incorporated into IEEE 802.1Q.

Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)

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