IP網(wǎng)絡(luò)技術(shù)基礎(chǔ)-路由協(xié)議詳解

路由協(xié)議基礎(chǔ)內(nèi)容路由協(xié)議基本介紹靜態(tài)路由協(xié)議及動態(tài)路由協(xié)議路由協(xié)議分類常用路由協(xié)議概念I(lǐng)nternet：inter+network路由器(router):route+er路由協(xié)議:routingprotocol概念地址：10.10.10.10/24路由表：10.10.10.0/24via10.10.9.1AS：AutonomoussystemToroute,arouterneedstodothefollowing:KnowthedestinationaddressIdentifythesourcesitcanlearnfromDiscoverpossibleroutesSelectthebestrouteMaintainandverifyroutinginformationWhatIsRouting?Routersmustlearndestinationsthatarenotdirectlyconnected.WhatIsRouting?(Cont.)路由StaticDefaultDynamic（1）信息的傳播（2）路由的計(jì)算StaticRouteUsesaroutethatanetworkadministratorentersintotheroutermanuallyDynamicRouteUsesaroutethatanetworkroutingprotocoladjustsautomaticallyfortopologyortrafficchangesIdentifyingStaticandDynamicRoutesStaticRoutesConfigureunidirectionalstaticroutestoandfromastubnetworktoallowcommunicationstooccur.StaticRouteExampleThisisaunidirectionalroute.Youmusthavearouteconfiguredintheoppositedirection.DefaultRoutesThisrouteallowsthestubnetworktoreachallknown networksbeyondrouterA.路由協(xié)議種類按應(yīng)用范圍分:IGP:InteriorgatewayprotocolEGP:exteriorgatewayprotocol按作用原理分:距離矢量:distancevector鏈路狀態(tài):link-state

Anautonomoussystemisacollectionofnetworksunderacommonadministrativedomain.IGPsoperatewithinanautonomoussystem.EGPsconnectdifferentautonomoussystems.AutonomousSystems:InteriororExteriorRoutingProtocolsAdministrativeDistance:

RankingRoutes距離矢量路由協(xié)議

初始化時，所有路由器在本機(jī)形成與本地直接連接的鏈路記錄路由器向所有相連的路由器廣播路由表內(nèi)已有的記錄路由器向外廣播接收到的路由信息，再在鄰路由器形成記錄相關(guān)內(nèi)容路由更新：定期更新路由計(jì)算：hop或復(fù)合路由收斂：缺點(diǎn)：收斂慢、路由回環(huán)、路由表全部更新優(yōu)化措施：毒性翻轉(zhuǎn)、水平分割、觸發(fā)更新增強(qiáng)型距離矢量協(xié)議典型協(xié)議RIPIGRPEIGRP鏈路狀態(tài)路由協(xié)議當(dāng)路由器初始化或當(dāng)網(wǎng)絡(luò)結(jié)構(gòu)發(fā)生變化時，路由器會產(chǎn)生鏈路狀態(tài)廣播數(shù)據(jù)包LSA（Link-StateAdvertisement）所有路由器會通過一種被稱為刷新（Flooding）的方法來交換鏈路狀態(tài)數(shù)據(jù)。路由協(xié)議收斂以后，所有的路由器會根據(jù)其各自的鏈路狀態(tài)信息數(shù)據(jù)庫計(jì)算出各自的路由表。相關(guān)內(nèi)容SPF算法層次結(jié)構(gòu)Metric典型協(xié)議OSPFIS-ISAfterinitialflood,passsmallevent-triggeredlink-state

updatestoallotherroutersLink-StateRoutingProtocolsMinimizesroutingtableentriesLocalizesimpactofatopologychangewithin

anareaLink-StateNetworkHierarchyExampleLink-StateRouting

ProtocolAlgorithmsBenefitsofLink-StateRoutingFastconvergence:changesarereportedimmediatelybythesourceaffected.Robustnessagainstroutingloops:Routersknowthetopology.Link-statepacketsaresequencedandacknowledged.Bycareful(hierarchical)networkdesign,youcanutilizeresourcesoptimally.DrawbackstoLink-StateRoutingProtocolsInitialdiscoverymaycauseflooding.Memory-andprocessor-intensive.距離矢量VS鏈路狀態(tài)距離矢量路由協(xié)議：shareinformationlocallyuseadistributedroutecalculation鏈路狀態(tài)路由協(xié)議:informationdistributedunchanged;eachrouterperformalocalbest-pathcalculationBGP協(xié)議BorderGatewayProtocol廣泛應(yīng)用于目前Internet上路徑矢量IBGP，EBGP路由對等體策略AutonomousSystemsAutonomousSystem65000AutonomousSystem65500IGPs:RIP,IGRP,OSPF,EIGRPEGPs:BGPAnautonomoussystem(AS)isacollectionofnetworksunderasingletechnicaladministrationIGPsoperatewithinanautonomoussystemEGPsconnectdifferentautonomoussystemsBGPIsUsedBetweenAutonomousSystemsBGPisusedbetweenautonomoussystemsGuaranteesexchangeofloop-freeroutinginformationBGPBBGPAS

65500AS

65250BGPAS

64520AS

65000ABCFEDRoutingTablePrefixes

020501 104,027BGPCharacteristicsBGPisadistancevectorprotocolwithenhancements:Reliableupdates—BGPrunsontopof

TCP(port179)Incremental,triggeredupdatesonlyPeriodickeepalivestoverifyTCPconnectivityRichmetrics(calledpathvectorsorattributes)Designedtoscaletohugeinternetworks

(forexample,theInternet)BGPinIPPacketsBGPisanadvanceddistancevectorroutingprotocolReliesonTCPforreliablesessionmanagementUsesTCPportnumber179TCPHeaderPortNo.SegmentPayloadIPHeaderProtocolNumberFrameHeaderCRCPacketPayloadFramePayload6—TCP17—UDP179—BGP23—Telnet25—SMTPTablesIGP

Routing

ProtocolBGP

Routing

ProtocolIPBGPBGPhasitsowntable,inadditiontotheIProutingtableInformationcanbeexchangedbetweenthe

twotablesAnytworoutersthathaveformedaTCPconnectioninordertoexchangeBGProutinginformationarecalledpeersorneighborsPeers=NeighborsAS65000NeighborsAS65500NeighborsACBInternalBGPWhenBGPneighborsbelongtothesameASitiscalledinternalBGP(IBGP)NeighborsdonothavetobedirectlyconnectedAIBGPNeighborsAS65000AS65500NeighborsBCExternalBGPWhenBGPneighborsbelongtodifferentautonomoussystemsitiscalledexternalBGP(EBGP)NeighborsshouldbedirectlyconnectedAAS65000AS65500EBGPNeighborsIBGPNeighborsCBPolicy-BasedRoutingBGPallowsadministratorstodefinepolicies,orrules,forhowdatawillflowthroughtheautonomoussystemsBGPAttributesBGPattributesinclude:AS-pathNext-hopLocalpreferenceMulti-exitdiscriminator(MED)OriginCommunityBGPdefinesthefollowingmessagetypes:OpenIncludesholdtimeandBGProuterIDKeepaliveUpdateInformationforonepathonly

(couldbetomultiplenetworks)IncludespathattributesandnetworksNotificationWhenerrordetectedBGPconnectionclosedaftersentBGPMessageTypesRouteSelectionDecisionProcessConsideronly(synchronized)routeswithnoASloopsandavalidnexthop,andthen:Preferhighestweight(localtorouter)Preferhighestlocalpreference(globalwithinAS)PreferrouteoriginatedbythelocalrouterPrefershortestAS-pathPreferlowestorigincode(IGP<EGP<incomplete)PreferlowestMED(fromotherAS)PreferEBGP