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1、路由优化（Routingoptimization）Thetwenty-firstchapterisroutingoptimizationIntoday'shigh-performancenetworks,inordertoensurenetworkscalability,stability,securityandrapidconvergence,wemustNetworkoptimization.Routingfilteringandpolicyroutingarecommonmethodsforroutin
2、goptimization.21.1overviewofroutingoptimizationRoutingfilteringmeansthatsomeroutesarenotsentandreceivedintherouteupdate,thepassiveinterfaceandthedistributedcontrollist,Bothredistributionandroutingstrategiescanimplementroutingfiltering.Policyroutingprovidesa
3、mechanismforpacketforwardingbasedonstandardssetbynetworkmanagers.PolicybasedRoutingismoreflexibleandmoreflexiblethantraditionalrouting,whichallowsnetworkmanagersnotonlytotargetaddressesbutalsotorootSelecttheforwardingpathbasedonprotocoltype,messagesize,appl
4、ication,orIPsourceaddress.Thepolicyroutingpolicyconsistsofaroutingmap(route,map)todefine.Themostimportantcommandsinthe"routemap"are"match"and"set"".Matchisusedtodefinematchingconditions,andthematchingstatementdetectspacketsattheinputportoftherouter.Frequent
5、ly-usedMatchingcriteriaincludeIPaddresses,interfaces,metrics,andpacketlengths.Setdefinesthebehaviorofastatementthatconformstoamatchingcondition.Theusualbehaviorisshownintable21-1.Table21-1behaviorofsetSetbehaviordescriptionSetIPnexthopsetsthenexthopaddresso
6、fthepacketSetinterfacesetsthepacketoutputinterfaceSet,IP,default,next,hopSetsthedefaultnexthopaddressforroutingtablesWithoutroutingentriestothedestinationaddressofthepacketSetdefaultinterfacesetsthedefaultoutgoinginterfaceThesetIPTOSsetstheIPToSvalueoftheIP
7、packetThesetIPprecedencesetsthepriorityoftheIPpacket[attention]1.,thelastdefaultofaroutemapisdenyany".TheuseofthisdenydependsontheroutemapHowisitused?.Ifapacketdoesnotmatchforroutemap,itisroutedatthenormaldestinationaddressForwards,whereasforroutingentries,
8、ifroutemapdoesnotmatch,itisrejected;2.,aroutemapcancontainmultipleroutemapstatementsthatexecuteinthesameorderasACL,Beexecutedfromtoptobottom.21.2experiment1:controlsroutingupdateswithadistributedcontro
