Chapter 7 - Configuring Rapid Spanning Tree; Overview - Avaya P580 User Manual

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Overview

Contents
Purpose of
Spanning Tree
RSTP vs. STP
User Guide for the Avaya P580 and P882 Multiservice Switches, v6.0
Configuring Rapid
Spanning Tree
This chapter contains the following sections:
How RSTP Achieves Rapid Recovery
Spanning Tree Configurations
Configuring Global Spanning Tree Options
Viewing Global Spanning Tree Information
Configuring Spanning Tree Bridges
Viewing Bridge Port Information
Configuring a Bridge Port
Configuring Spanning Tree Settings for Switch Ports
STP prevents loops in layer 2 networks that have redundant paths. Loops in
layer 2 networks can result in duplicate frames and switches learning the
same MAC addresses on multiple interfaces.
To prevent loops, STP calculates a single path through the network and then
blocks any redundant paths. STP first identifies a root switch and then
identifies the most efficient path from the root switch to each switch in the
network. Any redundant paths that exist enter a blocked state.
If a network segment in the spanning tree becomes unreachable or if you
change the cost of a path, Spanning Tree recalculates a path through the
network and then activates the new best path.
In software version 6.0, the 802.1D Spanning Tree Protocol (STP) is
replaced with the Rapid Spanning Tree Protocol (RSTP). STP is relatively
slow at recovering from a failure in the network. RSTP was created to
decrease this recovery time.
When a switch is running RSTP, a port can change from blocking to
forwarding more quickly than when the switch is running STP. This
decrease in transition time makes it possible for RSTP to recover more
quickly from failures in the network.
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