Zte ZXR10 5250 Series - Figure 5-8 MSTP Topological Structure

ZXR105250SeriesCongurationGuide
lSamemappingrelationshipbetweenaVLANandaninstance.
lSwitchesshouldbeconnecteddirectly.
MultiplespanningtreescanbeconguredineachMSTParea,andtheyareindependent
fromeachother.EachspanningtreeisanInternalSpanningTree(IST),anditcanbe
calledasMultipleSpanningTreeInstance(MSTI).CommonSpanningTreeconnectsall
MSTareasintheswitchingnetwork.AnMSTareacanbeconsideredasaswitch,aCST
isaspanningtreewhichisgeneratedbySTPandRSTPprotocolcalculation.AllIST s
andCST sarecalledasCommonandInternalSpanningTree(CIST).ACISTisasingle
spanningtreeusedtoconnectallswitches.
InthisMSTPtopologystructure,anISTcanserveasasinglebridge(switch).Inthis
way,aCTScanserveasanRSTPfortheinteractionofcongurationinformation(BPDU).
MultipleinstancescanbecreatedinanISTareaandtheseinstancesarevalidonlyinthis
area.AninstanceisequivalenttoanRSTP ,exceptthattheinstanceneedstoperform
BPDUinteractionwithbridgesoutsidethisarea.
FortheMSTPtopologicalstructure,seeFigure5-8.
Figure5-8MSTPTopologicalStructure
Theportshavedifferentroles:
lMaster:TheporttypeisintroducedintheMSTPprotocol.Whenmultipledifferent
areasexist,themasterportistheportwiththeminimalcosttotheroot.
lRoot:Theportthathastheminimalcosttotherootbridgeandtakeschargein
forwardingdatatotherootnode.Whenmultipleportshavethesamecosttotheroot
bridge,theportwiththelowestportprioritybecomestotherootport.
lDesignated:Theporttransmitsdatatotheswitchdownward,andsendstheSTP
protocolmessagetomaintainthestateofSTP .
lBackup:TheportreceivestheSTPmessage,whichprovesthatthereexistsaloop
totheportitself.
5-34
SJ-20131111172707-002|2013-11-27(R1.0)ZTEProprietaryandCondential