Understanding How Portfast Works - Cisco WS-C2950SX-48-SI Configuration Manual

Configuring Spanning Tree PortFast, BPDU
Guard, BPDU Filter, UplinkFast, BackboneFast,
and Loop Guard
This chapter describes how to configure the PortFast, BPDU guard, BPDU filter, UplinkFast,
BackboneFast, and loop guard spanning tree enhancements on the Catalyst enterprise LAN switches.
For information on configuring spanning tree, see
Note
Note For complete syntax and usage information for the commands used in this chapter, refer to the
Catalyst 4500 Series, Catalyst 2948G, and Catalyst 2980G Switches Command Reference.
This chapter consists of these sections:
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Understanding How PortFast Works

PortFast causes a switch or trunk port to enter the spanning tree forwarding state immediately, bypassing
the listening and learning states.
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Understanding How PortFast Works, page 8-1
Understanding How PortFast BPDU Guard Works, page 8-2
Understanding How PortFast BPDU Filtering Works, page 8-2
Understanding How UplinkFast Works, page 8-3
Understanding How BackboneFast Works, page 8-4
Understanding How Loop Guard Works, page 8-6
Configuring PortFast, page 8-8
Configuring PortFast BPDU Guard, page 8-11
Configuring PortFast BPDU Filtering, page 8-13
Configuring UplinkFast, page 8-15
Configuring BackboneFast, page 8-17
Configuring Loop Guard, page 8-18
Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide
C H A P T E R
Chapter 7, "Configuring Spanning Tree."
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