introducing basic layer 2 switching and bridging functions and redundant

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1、Medium-SizedSwitchedNetworkConstructionIntroducingBasicLayer2SwitchingandBridgingFunctionsandRedundantSwitchedTopologiesOutlineOverviewFunctionsofEthernetSwitchesandBridgesFrameTransmissionModesHowSwitchesandBridgesLearnSourceMACAddressesHowSwitchesan

2、dBridgesForwardandFilterFramesRedundantSwitchedandBridgedTopologiesBroadcastStormsMultipleFramecopiesMACDatabaseInstabilitySummaryFunctionsofEthernetSwitchesandBridgesAddresslearningForwardingandfilteringLoopavoidanceTransmittingFramesMACAddressTableT

3、heinitialMACaddresstableisempty.LearningAddressesStationAsendsaframetostationC.LearningAddresses(Cont.)StationDsendsaframetostationC.LearningAddresses(Cont.)AllStationsendsframe.ForwardingandFilteringFramesStationAsendsaframetostationC.Thedestinationi

4、sknown;theframeisnotflooded.BroadcastandMulticastFramesBroadcastFramesMAC:FFFF.FFFF.FFFF;MulticastFrameMAC:01-00-5E开头.Broadcastandmulticastframesarefloodedtoallportsotherthantheoriginatingport.StationDsendsabroadcastormulticastframe.RedundantTopologyR

5、edundanttopologyeliminatessinglepointsoffailure.Redundanttopologycausesbroadcaststorms,multipleframecopies,andMACaddresstableinstabilityproblems.BroadcastStormsHostXsendsabroadcast.Switchescontinuetopropagatebroadcasttrafficoverandover.MultipleFrame

6、CopiesHostXsendsaunicastframetorouterY.TheMACaddressofrouterYhasnotbeenlearnedbyeitherswitch.RouterYwillreceivetwocopiesofthesameframe.HostXsendsaunicastframetorouterY.TheMACaddressofrouterYhasnotbeenlearnedbyeitherswitch.SwitchesAandBlearntheMACaddr

7、essofhostXonport1.TheframetorouterYisflooded.SwitchesAandBincorrectlylearntheMACaddressofhostXonport2.MACDatabaseInstabilitySummaryThreeFunctionsofEthernetSwitchesandBridges:LearningAddresses,ForwardingandFilteringFrames,Loopavoidance.Switchesandbridg

8、esuseoneofthreeoperatingmodestotransmitframes:cut-through,andfragment-free,storeandforward.Redundanttopologycausesbroadcaststorms,multipleframecopies,andMACaddresstableinstabilityproblems.