课件bcmsn30模块4 vlan路由03 cef.pptx

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课件bcmsn30模块4 vlan路由03 cef.pptx

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ImplementingInter-VLANRoutingDeployingCEF-BasedMultilayerSwitching

Layer3SwitchProcessingInLayer3switches,thecontrolpathanddatapatharerelativelyindependent.Thecontrolpathcode,suchasrouting

protocols,runsontherouteprocessor.Datapacketsareforwardedbytheswitchingfabric.

Layer3SwitchProcessing(Cont.)Layer3switchingcanoccurattwodifferentlocationsontheswitch.Centralizedswitching:Switchingdecisionsaremadeontherouteprocessorbyacentralforwardingtable.Distributedswitching:Switchingdecisionscanbemadeonaportorline-cardlevel.Layer3switchingtakesplaceusingoneofthesetwomethods:Routecaching:ALayer3routecacheisbuiltinhardwareastheswitchseestrafficflowintotheswitch.Topology-basedswitching:Informationfromtheroutingtableisusedtopopulatetheroutecache,regardless

oftraffic.

CEF-BasedMultilayerSwitchesCEFcachesroutinginformationintheFIBtableandLayer2next-hopaddressesintheadjacencytable.

MultilayerSwitchPacketForwardingProcessSomeIPpacketscannotbeprocessedinhardware.IfanIPpacketcannotbeprocessedinhardware,itisprocessedbytheLayer3engine.

CEF-BasedMLSLookups1.Layer3packetsinitiateTCAMlookup.2.Thelongestmatchreturnsadjacencywithrewriteinformation.3.Thepacketisrewrittenperadjacencyinformationandforwarded.

ARPThrottling

CEF-BasedMLSOperation

ConfiguringandVerifyingCEFConfiguringCEFipcef(enabledbydefault)iproute-cachecef(onlyonVLANinterface)VerifyingCEFshowipceffa0/1detailshowadjacencyfa0/1detail

EnablingCEFSwitch(config-if)#ipcefSwitch(config-if)#iproute-cachecefThecommandsrequiredtoenableCEFareplatformdependent:OntheCiscoCatalyst4000switchOntheCiscoCatalyst3550switch

VerifyingCEFSwitch#showipcef[typemod/port|vlan_interface][detail]Switch#showipcefvlan11detail

IPCEFwithswitching(TableVersion11),flags=0x0

?10routes,0reresolve