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Chapter4ServiceConguration

RapidSpanningTreeProtocol(RSTP)isonthebasisofcommonSTP ,addedwiththe

mechanismthattheportstatecanberapidlychangedfromBlockingtoForwarding,which

increasesthetopologyconvergencespeed.

MultipleSpanningTreeProtocol(MSTP)isonthebasisofRSTPandSTP ,addedwith

theforwardingprocessingofframeswithVLANID.Thewholenetworktopologystructure

canbeplannedintoaCommonandInternalSpanningTree(CIST),whichisdividedinto

CommonSpanningTree(CST)andInternalSpanningTree(IST).

ManydevicesenablingMSTPconstructMSTareainswitchingnetwork.Whenthedevices

satisfythefollowingconditions,theycanbeconsideredtoexistinaMSTarea.Aswitching

networkcancovermanyMSTareas.UsercandividetheswitchesintoaMSTareaby

usingMSTPcommands.

lSameareaname.

lSamereversionlevel.

lSamemappingrelationshipbetweenVLANandinstance.

lSwitchesshouldbeconnecteddirectly.

TherearemanyspanningtreescanbeconguredineachMSTParea,andtheyare

independenteachother.EachspanningtreeisInternalSpanningTree(IST),anditcan

becalledasMultipleSpanningTreeInstance(MSTI).CommonSpanningTreeconnect

allMSTareasinswitchingnetwork.AMSTareacanbeconsideredasaswitch,CSTis

aspanningtreewhichisgeneratedbySTPandRSTPprotocolcalculation.AllISTsand

CSTsarecalledasCommonandInternalSpanningTree(CIST).CISTisasinglespanning

treetoconnectallswitches.

InthisMSTPtopologystructure,anISTcanserveasasinglebridge(switch).Inthisway,

CTScanserveasanRSTPfortheinteractionofcongurationinformation(BPDU).Multiple

instancescanbecreatedinanISTareaandtheseinstancesarevalidonlyinthisarea.

AninstanceisequivalenttoanRSTP ,exceptthattheinstanceneedstoperformBPDU

interactionwithbridgesoutsidethisarea.

MSTPtopologicalstructureisshownasFigure4-9.

4-33

SJ-20120409144109-002|2012-07-02(R1.0)ZTEProprietaryandCondential

Zte ZXR10 2928E-PS User Manual

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