Specifications

March 14, 2011 Page 1 of 29
Configuring Spanning Trees
Thisdocumentprovidesthe followinginformationaboutconfiguringandmonitoringSp anning
TreeprotocolsonEnterasys
®
N‐Series,S‐Series,andK‐Seriesmodularswitches,A‐Series,B‐Series,
C‐Seriesstackablefixedswitches,andD‐Series,G‐Series,andI‐Seriesstandalonefixedswitches.
What Is the Spanning Tree Protocol?
TheSpanningTreeProtocol(STP)resolvestheproblemsofphysicalloopsinanetworkby
establishingoneprimarypathbetweenanytwodevices.Duplicatepathsarebarredfromuseand
becomestandbyorblockedpathsuntiltheoriginalpathfails,atwhichpointduplicatepathscan
bebroughtintoservice.Should
abridgebeaddedcreatingaredundantpath,STPblocksoneof
thepaths.Basically,the“tree”intheSpanningTreeProtocolistheoptimalbranchingofnetwork
pathsthatSTP‐enableddeviceskeepinmemoryforefficientandfault‐tolerantdataforwarding.
Why Would I Use Spanning Trees in My Network?
Redundantlinksmustbefactoredintoeventhesimplestoftopologiestoprotectagainstdataloss
anddowntimeduetoanysinglepointoffailure.However,redundantlinkscanalsosetanendless
loopinmotion,significantlystressingyournetwork’sspeedandefficiency.AsshowninFigure 1,
aplannedredundant
linkbetweenSwitch1andSwitch2makesitpossiblefora bridgingloopto
occur.IfStation1transmitsamulticastorbroadcastpackettoStation2inthisscenario,thepacket
For information about... Refer to page...
What Is the Spanning Tree Protocol? 1
Why Would I Use Spanning Trees in My Network? 1
How Do I Implement Spanning Trees? 2
STP Overview 2
Functions and Features Supported on Enterasys Devices 4
Understanding How Spanning Tree Operates 6
Configuring STP and RSTP 11
Configuring MSTP 18
Understanding and Configuring SpanGuard 20
Understanding and Configuring Loop Protect 22
Terms and Definitions 27
Note: For information about configuring Spanning Tree on the X-Series, refer to the X-Series
Configuration Guide.