Cisco Systems N3KC3064TFAL3 Configuring Rapid PVST+, Information About Rapid PVST+, STP Overview

C H A P T E R 8

Configuring Rapid PVST+

This chapter contains the following sections:

•Information About Rapid PVST+, page 63

•Configuring Rapid PVST+, page 78

•Verifying Rapid PVST+ Configurations, page 86

Information About Rapid PVST+

The Rapid PVST+ protocol is the IEEE 802.1w standard, Rapid Spanning Tree Protocol (RSTP), implemented on a per VLAN basis. Rapid PVST+ interoperates with the IEEE 802.1D standard, which mandates a single STP instance for all VLANs, rather than per VLAN.

Rapid PVST+ is enabled by default on the default VLAN (VLAN1) and on all newly created VLANs in software. Rapid PVST+ interoperates with switches that run legacy IEEE 802.1D STP.

RSTP is an improvement on the original STP standard, 802.1D, which allows faster convergence.

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.

Understanding STP

STP Overview

For an Ethernet network to function properly, only one active path can exist between any two stations.

When you create fault-tolerant internetworks, you must have a loop-free path between all nodes in a network. The STP algorithm calculates the best loop-free path throughout a switched network. LAN ports send and receive STP frames, which are called Bridge Protocol Data Units (BPDUs), at regular intervals. Switches do not forward these frames, but use the frames to construct a loop-free path.

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

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