Cisco WS-C4003 Software Guide - Page 97
Configuring Spanning Tree, How Spanning Tree Protocols Work
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CH A P T E R 7 Configuring Spanning Tree This chapter provides a brief overview of the IEEE 802.1D bridge Spanning Tree Protocol (STP) and describes how to use and configure Cisco's proprietary Spanning Tree Protocols, Per VLAN Spanning Tree + (PVST+), and Multi-Instance Spanning Tree Protocol (MISTP) on the Catalyst enterprise LAN switches. Note For information on configuring the spanning tree PortFast, UplinkFast, and BackboneFast features, see Chapter 8, "Configuring Spanning Tree PortFast, UplinkFast, and BackboneFast, and Loop Guard." This chapter consists of these sections: • How Spanning Tree Protocols Work, page 7-1 • Understanding PVST+ and MISTP Modes, page 7-10 • Bridge Identifiers, page 7-12 • Using PVST+, page 7-12 • Using MISTP-PVST+ or MISTP, page 7-18 • Configuring a Root Switch, page 7-27 • Configuring Spanning Tree Timers, page 7-30 • Configuring Spanning Tree BPDU Skewing, page 7-33 Note For complete syntax and usage information for the commands used in this chapter, refer to the Command Reference-Catalyst 4000 Family, Catalyst 2948G, and Catalyst 2980G Switches. How Spanning Tree Protocols Work This section describes the specific functions that are common to all spanning tree protocols. Cisco's proprietary spanning tree protocols, PVST+ and MISTP, are based on the IEEE 802.1D STP. (See the "Understanding PVST+ and MISTP Modes" section on page 7-10 for information about PVST+ and MISTP.) The 802.1D STP is a Layer 2 management protocol that provides path redundancy in a network while preventing undesirable loops. All spanning tree protocols use an algorithm that calculates the best loop-free path through the network. 78-12647-02 Software Configuration Guide-Catalyst 4000 Family, Catalyst 2948G, Catalyst 2980G, Releases 6.3 and 6.4 7-1
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