最新CCNA课件 3_生成树技术

©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-1Medium-SizedSwitchedNetworkConstructionIntroducingSpanningTreeProtocol©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-2OutlineEtherChannelIntroducingSTP术语IntroducingSpanningTreeProtocolOverviewSTPelectoralprocessSpanningTreePortStatesSpanningTreePathCostsSpanningTreeRecalculationRapidSpanningTreeProtocolSummary©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-3AdvantagesofEtherChannelLogicalaggregationofsimilarlinksbetweenswitches捆绑Load-sharesacrosslinks负载均衡ViewedasonelogicalporttoSTPRedundancy冗余增加带宽©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-4Etherchanel的配置当配置layer2端口作etherchannel时只要在成员端口配置模式下用channel-groupn命令指定该端口要加入的channel-group组，这时switch会自动创建port-channel接口，而当配置layer3端口作etherchannel时，还需现在全局配置模式下用interfaceport-channeln命令手工创建port-channel接口。具体配置：Switch#configureterminalSwitch(config)#interfacerangefastethernet0/4-5Switch(config-if-range)#channel-group5modedesirable|auto|on|active|passive©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-5Etherchannel端口间协商使用PAGP(PortAggregationProtocol，cisco专有)或LACP(LinkAggregationControlProtocol，802.3AD)PAGP的三种模式:desirable表示该端口会主动发PAGP数据包与对端进行协商auto表示该端口不会主动发PAGP数据包与对端进行协商on表示强制将该端口加入etherchannel，不需用PAGP协议与对端行协商LACP的两种模式:active表示该端口会主动发LACP数据包与对端进行协商passive表示该端口不会主动发LACP数据包与对端进行协商了解了这几种模式的意义后，只要两端port的配置匹配即可。©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-6IEEEandDECIntroducingIEEE：InstituteofElectricalandElectronicsEngineersDEC：DigitalEquipmentCorporationSTP:TheSTPdevelopbytheDECcompany.（IEEE802Committeemodifyredistribute:802.1DStandard）©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-7Providesaloop-freeredundantnetworktopologybyplacingcertainportsintheblockingstatePublishedintheIEEE802.1DspecificationEnhancedwiththeCiscoPVST+implementationLoopResolutionwithSTP©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-8SpanningTreeProtocolOverviewSTPneedusethefollowingparameterestablishloop-freeswitchednetwork:•Rootbridge根桥•Rootports根端口•Designatedports指定端口•Nondesignatedports非指定端口©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-9根桥是交换网络中STP的一个参考点.根端口是非根桥上到根桥距离最短的接口.指定端口是每一段链路到根桥距离最短的接口.非指定端口是不启用的.根桥/根端口/指定端口/非指定端口的定义:©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-10每一个交换网络里面有且只有一个根桥.每一个非根桥中有且只有一个根端口.每一段链路中有且只有一个指定端口.非指定端口是不启用的.根桥/根端口/指定端口/非指定端口的特点:©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-11根桥:是L2交换网络中,STP拓扑的一个参考点.根桥定时发送配置报文(BPDU)，非根桥接收配置报文并转发.成为根桥的条件:BridgeID小的将成为根桥(先比较Switch的优先级,如果相等则比较MAC地址)©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-12STPTerminology:BridgeIDBridgeIDDefaultpriority:32768（0~65535）©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-13STPTerminology:STPPathCostLinkSpeedCost(RevisedIEEESpecification)Cost(PreviousIEEESpecification)10Gb/s211Gb/s41100Mb/s191010Mb/s100100©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-14Spanning-TreeOperation©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-15SpanningTreePractice(Cont.)©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-16SpanningTreePractice(Cont.)©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-17SpanningTreePractice(Cont.)©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-18SpanningTreePractice(Cont.)©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-19BPDUfunctionIntroducingBPDU(default=sentevery2seconds).BPDUMAXage=20seconds.BPDUfunction:Electrootbridge.Discoverredundantpathseat.Advertisenetworktopologychangeinformation.MaintainSTPstatus.©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-20ContentsinformationofBPDURootIDCostBridgeIDPortIDMaxagetimersHellotime©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-21Spanningtreetransitseachportthroughseveraldifferentstates:Spanning-TreePortStates©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-22Spanning-TreeRecalculation©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-23Spanning-TreeRecalculation(Cont.)Whentheswitchednetworkchange©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-24RapidSpanningTreeProtocolRSTP:Discard,Learning,Forwarding.RSTP802.1wstandard,STP802.1DstandardRSTP:AlternatePort,BackupPort.STPPortStatusRSTPPortStatusPortactivetopologyLearningMACBlocking阻塞Discard丢弃nonoListening监听Discard丢弃nonoLearning学习Learning学习noyesForwarding转发Forwarding转发yesyesRSTPandSTPcompare©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-25RSTP(快速生成树协议)802.1w由802.1d发展而成就只有三个状态丢弃-----〉相当于802.1d里面的阻塞、侦听和禁用状态学习转发在RSTP中仍然存在根交换机和指定端口，他们的功能与802.1d相同然而新增加了两个端口角色：替代端口----〉是辅助的未被使用的根端口后备端口-----〉是辅助的未被使用的指定端口每VLANRSTP(PVRST+)它定义了这样一种生成树协议,即每个VLAN都有一个RSTP实例.多生成树协议(MSTP)它定义了这样一种生成树协议,即为网络运行多个生成树实例.但不像PVRST+,MSTP允许将同一个生成树实例用于多个VLAN,以减轻交换机的负担.©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-26RapidSpanningTreeProtocol©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-27RapidSpanningTreeProtocol(Cont.)©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-28RapidSpanningTreeProtocol(Cont.)©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-29RapidSpanningTreeProtocol(Cont.)©2007CiscoSystems,Inc.Allrightsreserved.ICND2v1.0—2-30Desc