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ID:54013050
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时间:2020-04-28
《stp生成树协议培训.ppt》由会员上传分享,免费在线阅读,更多相关内容在应用文档-天天文库。
1、生成树协议SpanningTreeProtocolObjectivesRedundanttopologiesSpanningTreeProtocol冗余(Redundancy)冗余网络拓扑确保网络持续工作,避免单点故障Redundantnetworkingtopologiesaredesignedtoensurethatnetworkscontinuetofunctioninthepresenceofsinglepointsoffailure.冗余拓扑(RedundantTopologies)冗余拓扑(RedundantTopologies)1.冗余拓扑的目标
2、是为了避免网络出现单点故障Agoalofredundanttopologiesistoeliminatenetworkoutagescausedbyasinglepointoffailure.2.所有的网络需要冗余来提高可靠性Allnetworksneedredundancyforenhancedreliability.简单的冗余交换拓扑(SimpleRedundantSwitchedTopology)简单的冗余交换拓扑(SimpleRedundantSwitchedTopology)1.冗余拓扑消除了单点故障Redundanttopologieselim
3、inatesinglepointsoffailure.2.交换机对不知道地址的帧进行泛洪Switcheswillfloodframesforunknowndestinations.3.交换机对广播和组播也进行泛洪。Broadcastsandmulticastsarealsoflooded.4.冗余交换拓扑或许会带来广播风暴、多帧拷贝以及MAC地址表不稳定的问题Aredundantswitchedtopologymaycausebroadcaststorms,multipleframecopies,andMACaddresstableinstabilitypro
4、blems.广播风暴(BroadcastStorm)多帧传输(MultipleFrameTransmissions)在冗余交换网络中,对终端设备来讲,收到多帧相同数据是可能的。Inaredundantswitchednetworkitispossibleforanenddevicetoreceivemultipleframes.创建逻辑无环路拓扑(Creatingalogicalloopfreetopology)1.冗余增加了可靠性,但是同时将物理环路带进网络。Reliabilityisincreasedbyredundancy.redundancyconn
5、ectionsintroducephysicalloopsintothenetwork.2.解决办法就是创建逻辑无环路拓扑,同时保留物理环存在Thesolutionistoallowphysicalloops,butcreatealoopfreelogicaltopology.3.无环路拓扑称为树,并且是可扩展的树。Theloopfreelogicaltopologycreatediscalledatree.Itisaspanningtreebecausealldevicesinthenetworkarereachableorspanned.4.创建无环路拓扑
6、的算法称为生成树算法。Thealgorithmusedtocreatethisloopfreelogicaltopologyisthespanning-treealgorithm.STP术语(STPTerms)1.桥ID(BridgeID)2.开销(Cost)3.桥协议数据单元(BPDU)桥ID(BridgeID)1.BID用来识别每一个交换机/网桥。2.BID用来确定网络的中心,在STP中称为根桥。3.优先级默认为32768TheBIDconsistsofabridgeprioritythatdefaultsto32768开销(Cost)最短路径是cost累
7、加,而cost是基于链路的速率的。Shortestpathisbasedoncumulativelinkcosts.Linkcostsarebasedonthespeedofthelink.桥协议数据单元(BPDU)1.交换机发送的创建逻辑无环路的数据包称为BPDUThemessagethataswitchsends,allowingtheformationofaloopfreelogicaltopology,iscalledaBridgeProtocolDataUnit(BPDU).2.BPDU在阻塞的接口上也可以接收,这确保如果链路或设备出现问题,新的生成
8、树会被计算BPDUscontinuet
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