Zte ZXR10 5250-28SM - Table 5-1 Port Role and Port State

Chapter5ServiceConguration
lAlternate:TheportreceivesexcessSTPprotocolmessagesfromotherequipment.
However,whentheoriginallinkfails,theportbecomestransmittingandmaintainsthe
networktakingtheplaceofthefaultyport.
lEdged:Theportisusedtoconnecttheterminalequipment,forexample,PC.The
portdoesnotparticipateinthecalculationbeforetheSTPisstable,andthestatecan
beswitchedfast.
Accordingtotheportrole,theportstateisdifferentafterthecalculationbecomessteady.
Fortherelationshipsbetweentheportroleandtheportstate,refertoT able5-1.
Table5-1PortRoleandPortState
PortRolePortState
MasterForward
RootForward
DesignatedForward
BackupDiscard
AlternateDiscard
EdgedForward
ProtectionFeatureOverview
BPDUProtectiononaPort
AboundaryportisnotexpectedtoreceiveanyBPDUs.ReceiptofanyBPDUsindicates
afailureinthenetwork.T oavoidthissituation,BPDUprotectioncanbeconguredona
boundaryport.
AfterbeingconguredwithBPDUprotection,ifaportreceivesaBPDU,theportwillbe
shutdownandawarningmessagewillbedisplayed.Thesystemwaitsforsomeseconds
ofuserconguredandthentriestore-opentheport.IfitstillreceivesBPDUs,theportwill
beshutdownagain.Bydoingso,thenetworkcanbeprotectedfrombeingattackedby
abnormalBPDUstomaintainthestabilityofthetopology.
LoopbackProtectiononaPort
Whenanon-designatedportsotherthanportbreaksdownandcannotreceiveanyBPDUs,
STPwilltransittheporttoadesignatedportanditsstatetoForwardingstate,whichleads
toloops.T oavoidthissituation,portloopbackprotectioncanbeconguredonablocked
port.
Afterbeingconguredwithportloopbackprotection,ifablockedportnolongerreceives
anyBPDUs,itwillenterLoop_Inconsistentstate,underwhichnodatawillbeforwarded
fromthisport.WhenitreceivesBPDUsagain,theportwillautomaticallyrecovertoa
blockedport.
RootProtectiononaPort
Afterthenetworkhascompletedthespanningtreecalculation,ifanewswitchisinvolved
andthenumericalvalueforitsbridgeIDislowerthanthatfortherootbridge,thenew
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SJ-20131111172707-002|2013-11-27(R1.0)ZTEProprietaryandCondential