网络工程师-9-交换机原理及配置.ppt

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1、Chapter9交换机原理及配置地址（MAC）学习转发/筛选环路避免Switch的三个功能Switches地址学习初始MAC地址表为空学习源地址MACaddresstable0260.8c01.11110260.8c01.22220260.8c01.33330260.8c01.4444E0E1E2E3ABCDSwitches地址学习StationAsendsaframetoStationCSwitchcachesstationAMACaddresstoportE0bylearningthesource

2、addressofdataframesTheframefromstationAtostationCisfloodedouttoallportsexceptportE0(unknownunicastsareflooded)MACaddresstable0260.8c01.11110260.8c01.22220260.8c01.33330260.8c01.4444E0:0260.8c01.1111E0E1E2E3DCBASwitches地址学习StationDsendsaframetostationCSw

3、itchcachesstationDMACaddresstoportE3bylearningthesourceAddressofdataframesTheframefromstationDtostationCisfloodedouttoallportsexceptportE3(unknownunicastsareflooded)MACaddresstable0260.8c01.11110260.8c01.22220260.8c01.33330260.8c01.4444E0:0260.8c01.1111

4、E3:0260.8c01.4444E0E1E2E3DCABSwitches转发/过滤StationAsendsaframetostationCDestinationisknown,frameisnotfloodedE0:0260.8c01.1111E2:0260.8c01.2222E1:0260.8c01.3333E3:0260.8c01.44440260.8c01.11110260.8c01.22220260.8c01.33330260.8c01.4444E0E1E2E3XXDCABMACaddre

5、sstableStationDsendsabroadcastormulticastframeBroadcastandmulticastframesarefloodedtoallportsotherthantheoriginatingport0260.8c01.11110260.8c01.22220260.8c01.33330260.8c01.4444E0E1E2E3DCABE0:0260.8c01.1111E2:0260.8c01.2222E1:0260.8c01.3333E3:0260.8c01.4

6、444MACaddresstable广播与多播Frame冗余路径冗余路径消除了单故障点冗余路径的不利后果：广播风暴,多个Frame副本,MAC地址表不稳定Segment1Segment2Server/hostXRouterYSegment1Segment2Server/hostXRouterYBroadcastSwitchASwitchBHostXsendsaBroadcast广播风暴Segment1Segment2Server/hostXRouterYBroadcastSwitchASwitchBH

7、ostXsendsaBroadcast广播风暴Segment1Segment2Server/hostXRouterYBroadcastSwitchescontinuetopropagatebroadcasttrafficoverandoverSwitchASwitchB广播风暴多个Frame副本Segment1Segment2Server/hostXRouterYUnicastSwitchASwitchBHostXsendsanunicastframetorouterYRouterYMACaddres

8、shasnotbeenlearnedbyeitherswitchyetSegment1Segment2Server/hostXRouterYUnicastSwitchASwitchBHostXsendsanunicastframetoRouterYRouterYMACAddresshasnotbeenlearnedbyeitherSwitchyetRouterYwillreceivetwocopiesofthesameframeUnicastUnicas