Enterasys SecureStack B3

SecureStack B3 Configuration Guide 7-1
7
Spanning Tree Configuration
ThischapterdescribestheSpanningTreeConfigurationsetofcommandsandhowtousethem.
Spanning Tree Configuration Summary
Overview: Single, Rapid, and Multiple Spanning Tree Protocols
TheIEEE802.1DSpanningTreeProtocol(STP)resolvesthe problemsofphysicalloopsina
networkbyestablishingoneprimarypathbetweenanytwodevicesinanetwork.Anyduplicate
pathsarebarredfromuseandbecomestandbyorblockedpathsuntiltheoriginalpathfails,at
whichpointtheycan
bebroughtintoservice.
RSTP
TheIEEE802.1wRapidSpanningProtocol(RSTP),anevolutionof802.1D,canachievemuch
fasterconvergencethanlegacySTPinaproperlyconfigurednetwork.RSTPsignificantlyreduces
thetimetoreconfigurethenetwork’sactivetopologywhenphysicaltopologyorconfiguration
parameterchangesoccur.Itselectsoneswitchastherootof
aSpanningTree‐connectedactive
topologyandassignsportrolestoindividualportsontheswitch,dependingonwhetherthatport
ispartoftheactivetopology.
RSTPprovidesrapidconnectivityfollowingthefailureofaswitch,switchport,oraLAN.Anew
rootportandthedesignatedport
ontheothersideofthebridgetransitiontoforwardingthrough
anexplicithandshakebetweenthem.Bydefault,userportsareconfiguredtorapidlytransitionto
forwardinginRSTP.
MSTP
TheIEEE802.1sMultipleSpanningTreeProtocol(MSTP)buildsupon802.1DandRSTPby
optimizingutilizationofredundantlinksbetweenswitchesinanetwork.Whenredundantlinks
existbetweenapairofswitchesrunningsingleSTP,onelinkisforwardingwhiletheothersare
For information about... Refer to page...
Spanning Tree Configuration Summary 7-1
Configuring Spanning Tree Bridge Parameters 7-3
Configuring Spanning Tree Port Parameters 7-31
Configuring Spanning Tree Loop Protect Parameters 7-39
Caution: Spanning Tree configuration should be performed only by personnel who are very
knowledgeable about Spanning Trees and the configuration of the Spanning Tree Algorithm.
Otherwise, the proper operation of the network could be at risk.