思科-ccna杂cisco中文ccnp001bgp汇总

BorderGatewayProtocolRouteSummarization©2003,CiscoSystems,Inc.Allrightsreserved.1ObjectivesUponcompletingthislesson,youwillbeableto:ExplainhowBorderGatewayProtocolversion4isrelatedtoclasslessinterdomainrouting(BGP4对无类域间路由的支持.)ExplainhowBorderGatewayProtocolimplementsroutesummarizationwiththenetworkcommand(用NETWORK命令实施路由汇总)DescribehowBorderGatewayProtocolimplementsroutesummarizationwiththeaggregate-addresscommand(用地址聚合命令实施路由汇总.)CIDRandAggregateAddresses

WithBGP4,routescan

beaggregatedbyany

ASonanyBGProuter.BGP4isclassless,

supportsVLSMand

longestmatchrouting,

andcarriesanetwork

maskforeachnetwork

intheupdate.BGP更新消息中包括地址前缀和前缀长度.NetworkBoundarySummarizationnoauto-summaryRouter(config-router)#

BGP,RIPv1andRIPv2,IGRP,andEIGRPperform

networkboundarysummarizationbydefault.(自动汇总)BGP,RIPv2,andEIGRPcandisable(关闭)network

boundarysummarization.CIDRhasforcedtheIANAtobeginusingclass

Aaddresses,like,inaclasslessmanner.IfyouareassignedaportionofaclassA,B,orC

address,theno-autosummarycommandneeds

tobeimplementedundertheBGPprocessoryou

riskclaimingownershipofthewholeclassA,B,

orCaddress.

networknetwork-number[masknetwork-mask]

Router(config-router)#Thiscommandwasnotdesignedtoperformsummarizationbyitself.Theaggregate-addresscommandwasdesignedforsummarization.(将外部路由宣告到BGP中去.)BGPnetworkCommandiprouteprefix

masknull0(人工创建汇总静态路由到空端口.)Router(config)#Tousethenetworkstatementforsummarization,thenetworknumberandmaskusedmustalreadyexistintheroutingtable.IftheroutewasalreadysummarizedbyEIGRPorOSPF,thatsummarizationcanbeannouncedintoBGPwiththenetworkandmaskcommands.Iftheroutewasnotalreadysummarized,anullroutemustbecreatedforBGPtoannouncethissummarization.空端口:如果BGP路由表没有这条汇总路由时,BGPNETWORK命令无法发布.汇总路由不能确定从哪个物理端口走,所以用空端口来决定来告诉路由器如何走CautionsaboutNetworkStatementIfanetworkstatementis

usedforsummarization,

donotusethemore

specificentriesandthe

summarizedrouteas

shownhere.Ifbothareused,the

summarizedrouteandthe

morespecificrouteswill

beannounced./22doesnot

existintheIProutingtable

withoutthenullroute.BGP

willnotannouncethenetwork

unlessthesummarizedroute

isalreadypresentinthe

routingtable.NETWORK也有间接汇总功能.要求网络必须先存在,可以使用空端口.BGPSummarizationUsingthenetworkCommandandStaticRoutetoNull0ConfiguringBGPforAggregateAddressingaggregate-addressip-address

mask[summary-only][as-set]Router(config-router)#Createsanaggregate(summary)entryinthe

BGPtable(无须先有路由.)Usesthesummary-onlyoptiontoadvertiseonly

thesummaryandnotthespecificroutes（通告汇总路由）Addstheas-setoptiontoincludealistofallthe

autonomoussystemnumbersthatthemore

specificrouteshavepassedthrough(要求在AS属性中列出包含具体路由的AS号，以避免环路.)mendedmethodofsummarizationforBGPNullstaticroutenotneeded;BGPnullroute

automaticallygenerated(会自动产生一条汇总路由,并且指向空端口.)BGPSummarizationUsingtheaggregate-addressCommandBGPAggregationshowipbgpNetwork/22

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NextHopLocPrfWeight3276832768327683276832768

PathiiiiiMetric00000routerC#showipbgpBGPtableversionis28,localrouterIDisStatuscodes:s=s