CCNA 3-4冗余拓扑、STP.ppt

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1、Medium-SizedSwitchedNetworkConstructionImprovingPerformancewithSpanningTreeInterconnectionTechnologiesTechnologyUseFastEthernetConnectsend-userdevicestotheaccesslayerswitchGigabitEthernetConnectsaccessswitchtodistributionswitchandhighuseserverstoswitches10-GigabitEthernetProvideshigh

2、-speedswitchtoswitchlinks,backbonesEtherChannelProvideshigh-speedswitchtoswitchlinks,backboneswithredundancyDeterminingEquipmentandCablingNeedsEachlinkprovidesadequatebandwidthforthetotalaggregatetrafficoverthatlink.AdvantagesofEtherChannelLogicalaggregationofsimilarlinksbetweenswit

3、chesLoad-sharesacrosslinksViewedasonelogicalporttoSTPRedundancyRedundantTopologyRedundanttopologyeliminatessinglepointsoffailure.Redundanttopologycausesbroadcaststorms,multipleframecopies,andMACaddresstableinstabilityproblems.StationDsendsabroadcastframe.Broadcastframesarefloodedtoal

4、lportsexcepttheoriginatingport.BroadcastFramesBroadcastStormsHostXsendsabroadcast.Switchescontinuetopropagatebroadcasttrafficoverandover.MultipleFrameCopiesHostXsendsaunicastframetorouterY.TheMACaddressofrouterYhasnotbeenlearnedbyeitherswitch.RouterYwillreceivetwocopiesofthesameframe

5、.HostXsendsaunicastframetorouterY.TheMACaddressofrouterYhasnotbeenlearnedbyeitherswitch.SwitchesAandBlearntheMACaddressofhostXonport1.TheframetorouterYisflooded.SwitchesAandBincorrectlylearntheMACaddressofhostXonport2.MACDatabaseInstabilityProvidesaloop-freeredundantnetworktopologyby

6、placingcertainportsintheblockingstatePublishedintheIEEE802.1DspecificationEnhancedwiththeCiscoPVST+implementationLoopResolutionwithSTPSpanning-TreeOperationOnerootbridgeperbroadcastdomain.Onerootportpernonrootbridge.Onedesignatedportpersegment.Nondesignatedportsareunused.STPRootBridg

7、eSelectionBPDU(default=sentevery2seconds)Rootbridge=bridgewiththelowestbridgeIDBridgeID=BridgePriorityMACAddressSpanningtreetransitseachportthroughseveraldifferentstates:Spanning-TreePortStatesDescribingPortFastPortFastisconfiguredonaccessports,nottrunkports.ConfiguringandVerifyingPo

8、rtFastspanni