思科ccna杂cisco中文ccnp0001.路由重分布

IGP路由再发布

本节内容:在多种路由协议选择协议间进行再发布配置再发布控制路由选择更新的数据流量验证再发布的运行概述在整个IP互联网中，如果从配置管理和故障管理的角度看，我们通常更愿意运行一种路由选择协议，而不是多种路由选择协议。然而，现代的互联网络又常常强迫我们接受多协议IP路由选择域这一现实。这些差异性使得向单一路由选择协议的迁移，成为一项复杂的任务。另外，多厂商环境是需要重新分配路由的另一个因素。重新分配使得IGP路由的动态特性和静态路由的精确控制性融合在一起。MigratingtoaNewRoutingProtocolPlanningtheIPAddressTransitionDecideifthetransitionishappening

allatonceoroveranextendedperiod

oftimeandplanaccordingly.Decideonthenewaddressspaceto

beusedfortheentirenetwork.Allocateaddressspaceanddocument

addressassignment.Examineandplanfortheeffectofthe

addresschangesonthefollowing:SecondaryaddressesNetworkstatementforroutingHostaddressingAccesslistsNATDNSImplementingtheIP-AddressTransitionSelecttherouterandthesubnet

tobetransitioned.AssignsecondaryIPaddresses

torouters.Assignnewnetworkstatementsto

theroutingprocess.UpdateDNSfornewaddresses.ImplementDHCP,ifnotalreadyused.ConfigureDHCPservertoassignnew

addresses,mask,anddefaultgateways.Allowenoughtimefortransition.ChangesecondaryIPaddresstoprimary.Removeoldnetworkstatementsfrom

theroutingprocess.RemoveoldDNSentries.Migratetonewroutingprotocol

withredistribution.ConfiguringaSecondaryIPAddressRouter#showrun

<outputomitted>

interfaceEthernet0

ipaddress10.1.2.3255.255.255.0Router(config)#interfacee0

Router(config-if)#ipaddress

172.17.1.3255.255.255.240secondaryRouter#showrun

<outputomitted>

interfaceEthernet0

ipaddress172.17.1.3255.255.255.240secondaryipaddress10.1.2.3255.255.255.0Before:After:MigratingtoaNewIPRoutingProtocol

Implementandtesttheroutingsolution

inthelabenvironment.Backuptherouterconfigurations.Determinethetimelineforimplementing

andtestingthenewrouterconfiguration.Identifytheboundaryrouterswhere

themultipleroutingprotocolswillrun.Determinewhichroutingprotocolis

thecoreandwhichistheedge.Determinethedirectionsyouwantto

redistributetheprotocols.UsingMultipleRoutingProtocolsInterimduringconversionApplication-specificprotocols

OnesizedoesnotalwaysfitallPoliticalboundaries

GroupsthatdonotworkwellwithothersMismatchbetweendevicesMultivendorinteroperabilityHost-basedrouters

RedistributingRouteInformationSeedMetricThefirst,orseed,metricforarouteis

derivedfrombeingdirectlyconnected

toarouterinterface.Usethedefault-metriccommandto

establishtheseedmetricfortheroute

orspecifythemetricwhenredistributing.Onceacompatiblemetricisestablished,

themetricwillincrementjustlikeany

otherroute.DefaultSeedMetricsRedistributionImplementationConsiderationsRoutingfeedbackSuboptimalpathselectionpatibleroutinginformationInconsistentconvergencetimeRedistributionTechniques

RedistributingRouteInformation对重发布的考虑重发布发引起的问题：路由环路；路由选择信息不兼容；收敛的时间不一致。路由器如何选择最佳路径？通过管理距离和种子度量值来选择最佳路由；只能在那些支持同一路由选择协议栈的协议间进行再发布。附：管理距离和种子度量值管理距离：用来评价不同路由协议的可信度。种子度量值，如果一台边界路由器想要在路由选择协议间再发布信息，那么它必须能够将它从源路由选择协议接收到的路由的度量值转换为其他路由选择协议的度量值。这个开销度量值称为种子度量值。2.配置重发布配置再发布,易产生几种陷阱:路由回环,路由信息不兼容,收敛时间不一致;因此规划设计时要注意:熟悉我们的网络;不要重叠使用路由选择协议;在存在多台边界路由器的情况下使用单向再发布;在单台路由器上使用双向再发布.缺省路由,路由过滤器和管理距离修改等技术的组合可被用来消除路由环路.Routereigrp24Redistributeripmetric1000010025511500RouterripRedistributeeigrp24metric2Routerospf1Redistributeeigrp24metric100subnets重新分配原则：1，当重新分配路由时，必须为路由分配一个接收协议可以理解的度量值。2，在多种路由协议之间，需要为路由源分配管理距离；可把管理距离看作可信度的一个量度，管理距离越小，协议的可信度越高。3，在从无类别路由选择协议向有类别路由选择协议重新分配时也会使用到,仅在掩码相同的接口之间通告路由这一特性。配置重发布的步骤：1，找出将要进行重发布配置的边界路由器；其中使用命令redistribute指定路由源点。2，选定哪个路由协议是核心或主干协议；通常是BGP或OSPF。3，必须为重新分配的路由指定度量值；如果没有指明度量值，那么重新分配到OSPF的路由的度量值为20；而重新分配到其他协议路由度量值的缺省值为0，ISIS可以理解0度量，但是RIP不能，因为它的跳数在1到16之间；0度量与IGRP和EIGRP的多度量格式也不兼容；因此RIP，IGRP，EIGRP都必须为重新分配的路由分配合适的度量，否则重新分配将不能进行。例：OSPF＋IGRPACB172.16.29.0/24172.20.113.192/26172.20.115.0/24172.20.114.48/28172.20.110.0/24172.16.49.0/24IGRPOSPFROUTER

BRouterigrp1Redistributeospf1metric1000010025511500Passive-interfaceethernet1\\上面的配置把OSPF进程1发现的路由向IGRP进程1重新分配；命令的度量部分为路由分配了IGRP度量；按顺序，命令中各数字分别表示为：带宽10000kbit/s，时延100；可靠性；负载；MTURouterospf1Redistributeigrp1metric30metric-type1subnetsNetwork172.16.29.00.0.0.255area0\\把进程1发现的路由重分配进入OSPF进程1。重新分配使得B成为OSPF的ASBR，并且被重新分配的路由是作为外部路由进行通告的。命令metric-type部分指明了外部路由的类型为E1；关键字subnets仅当向OSPF分布路由时使用，它指明了重新分配的子网细节，没有它，仅重新分配主网地址。例：RIP＋IGRPACB10.5.2.0/2410.5.4.0/2410.5.3.0/2410.6.4.0/2410.6.3.0/2410.6.2.1/24IGRPRIPS1S1S0S0L0L1L0L1ROUTERB:RouterripRedistributeigrp1metric5Passive-interfaceS1Network172.16.49.0Routerigrp1RedistributeripDefault-metric100010025511500Network172.16.29.0\\其余见配置文件。例：isis＋ripACB172.16.29.0/2410.1.1.0/2410.1.2.160/2810.1.2.224/2810.1.3.0/2410.2.2.0/24172.16.49.0/24isisRIPRouterBRouterISISRedistributeripmetric0metric-typeinternallevel-2Net01.0001.0000.0000.0001.00RouterripRedistributeisislevel-1-2metric1Passive-interfaceethernet0Network172.16.49.0RedistributionSupportsAllProtocolsRtrA(config-router)#redistribute?

bgpBorderGatewayProtocol(BGP)connectedConnectedegpExteriorGatewayProtocol(EGP)eigrpEnhancedInteriorGatewayRoutingProtocol(EIGRP)igrpInteriorGatewayRoutingProtocol(IGRP)isisISOIS-ISiso-igrpIGRPforOSInetworksmobileMobileroutesodrOnDemandstubRoutesospfOpenShortestPathFirst(OSPF)ripRoutingInformationProtocol(RIP)staticStaticroutesConfiguringRedistributionintoRIPRtrA(config)#routerripRtrA(config-router)#redistributeospf?

<1-65535>ProcessIDRtrA(config-router)#redistributeospf1?

matchRedistributionofOSPFroutesmetricMetricforredistributedroutesroute-mapRoutemapreference

…<cr>

Defaultmetricisinfinity.RedistributingintoRIPConfiguringRedistributionintoOSPFRtrA(config)#routerospf1

RtrA(config-router)#redistributeeigrp?

<1-65535>AutonomoussystemnumberRtrA(config-router)#redistributeeigrp100?

metricMetricforredistributedroutesmetric-typeOSPF/IS-ISexteriormetrictypeforredistributedroutesroute-mapRoutemapreferencesubnetsConsidersubnetsforredistributionintoOSPFtagSettagforroutesredistributedintoOSPF

…<cr>

Defaultmetricis20.(如不指定的话)Defaultmetrictypeis2.(EX1,EX2)Subnetsdonotredistributebydefault.RedistributingintoOSPFConfiguringRedistributionintoEIGRPRtrA(config)#routereigrp100

RtrA(config-router)#redistributeospf?

<1-65535>ProcessIDRtrA(config-router)#redistributeospf1?

matchRedistributionofOSPFroutesmetricMetricforredistributedroutesroute-mapRoutemapreference

…<cr>

Defaultmetricisinfinity.RedistributingintoEIGRP

Bandwidthinkilobytes=10000Delayin10sofmicroseconds=100Reliability=255(maximum)Load=1(minimum)MTU=1500bytesConfiguringRedistributionintoIS-ISRtrA(config)#routerisis

RtrA(config-router)#redistributeeigrp100?

level-1IS-ISlevel-1routesonlylevel-1-2IS-ISlevel-1andlevel-2routeslevel-2IS-ISlevel-2routesonlymetricMetricforredistributedroutes

metric-typeOSPF/IS-ISexteriormetrictypeforredistributedroutesroute-mapRoutemapreference

…<cr>

Routesareintroducedaslevel2withametricof0bydefault.RedistributingintoIS-ISExample1:BeforeRedistribution(ccie)Example1:BeforeRedistribution(Cont.)Example:ConfiguringRedistributionatRouterBExample1:RoutingTablesafterRouteRedistributionExample1:RoutingTablesafterSummarizingRoutesandRedistributionsUsingRouteMapstoControlRoutingUpdates

©2003,CiscoSystems,Inc.Allrightsreserved.41RouteMapsRoutemapsaresimilartoascriptinglanguagebecauseofthefollowingreasons:Theyworklikeamoresophisticatedaccesslist.TopdownprocessingOncethereisamatch,leavetheroutemapLinesaresequence-numberedforeasierediting.InsertionoflinesDeletionoflinesRoutemapsarenamedratherthannumbered

foreasierdocumentation.Matchcriteriaandsetcriteriacanbeused,

similartotheif,thenlogicinascriptinglanguage.RouteMapApplicationsFollowngarethecommonusesofroutemaps:Redistributionroutefiltering:Amoresophisticatedalternativetodistributelists.Policy-basedrouting:Theabilitytodetermineroutingpolicybasedoncriteriaotherthanthedestinationnetwork.NAT:Definespools

ofpublicandprivateaddressspaceused

intranslation.BGPpolicyimplementation:TheprimarytoolfordefiningBGProutingpolicies.Route-MapOperationroute-mapmy_bgppermit10:: :: ::{matchstatements}:: :: ::{setstatements}route-mapmy_bgpdeny20:: :: :::: :: ::route-mapmy_bgppermit30:: :: :::: :: :: Alistofstatementscomposearoutemap.Thelistisprocessedtop-downlikeanaccesslist.Thefirstmatchfoundforarouteisapplied.Thesequencenumberisusedforinsertingordeletingspecificroute-mapstatements.RouteMapOperation(Cont.)Thematchstatementmaycontainmultiplereferences.MultiplematchcriteriainthesamelineusesalogicalOR.Atleastonereferencemustpermittherouteforittobeacandidateforredistribution.EachverticalmatchusesalogicalAND.Allmatchstatementsmustpermittherouteforittoremainacandidateforredistribution.Route-mappermitordenydeterminesifthecandidate

willberedistributed.redistributeprotocol[processid]route-mapmap-tag

router(config-router)#AllowsfordetailedcontrolofroutesbeingredistributedintoaroutingprotocolRouteMapCommandsroute-mapmap-tag[permit|deny][sequence-number] router(config)#Definestheroute-mapconditionsmatch{conditions} router(config-route-map)#Definestheconditionstomatchset{actions} router(config-route-map)#DefinestheactiontobetakenonamatchThematchCommandrouter(config-route-map)#Match{options}options:

ipaddressip-access-list

iproute-sourceip-access-list

ipnext-hopip-address-list

interfacetype

number

metricmetric-value

route-type[external|internal|level-1|level-2|local]

…Thematchcommandsspecifycriteriatobematched.Theassociatedroute-mapstatementpermitsordeniesthematchingroutes.ThesetCommandrouter(config-route-map)#set{options}

options:

metricmetric-value

metric-type[type-1|type-2|internal|external]

level[level-1|level-2|stub-area|backbone]

ipnext-hopnext-hop-address

Thesetcommandsmodifymatchingroutes.Modifiesparametersinredistributedroutesbgpspecificoptions:orginbgp-origin-code

weightbgp-weight

local-preferencebgp-path-attributes

automatic-tag RouteMapsandRedistributionCommandsRouter(config)#routerospf10Router(config-router)#redistributeriproute-mapredis-ripRouter(config)#route-mapredis-rippermit10matchipaddress2329setmetric500setmetric-typetype-1route-mapredis-ripdeny20matchipaddress37route-mapredis-rippermit30setmetric5000setmetric-typetype-2RoutesmatchingeitherACL23or29areredistributedwithanOSPFcostof500,externaltype1.RoutespermittedbyACL37arenotredistributed.AllotherroutesareredistributedwithanOSPFcostmetricof5000,externaltype2.Router(config)#access-list23permit10.1.0.00.0.255.255access-list29permit172.16.1.00.0.0.255access-list37permit10.0.0.00.255.255.255Example:RedistributionwithRouteMapsUsingAdministrativeDistance

toInfluencethe

RouteSelectionProcess©2003,CiscoSystems,Inc.Allrightsreserved.52AdministrativeDistance

Administrativedistanceisawayofrankingthe

trustworthinessofroutinginformation.Administrative

distanceisexpressedasaninteger,from0to255.Lower

administrativedistanceismoretrustworthy.ForR1toR6:RIP(administrativedistance120)wouldchooseR1-R4-R6IS-IS(administrativedistance115)wouldchooseR1-R4-R6OSPF(administrativedistance110)wouldchooseR1-R2-R3-R5-R6EIGRP(administrativedistance90)wouldchooseR1-R2-R3-R5-R6distanceweight[addresswildcard-mask[access-list-number|name]]

Router(config-router)#UsedforallprotocolsexceptEIGRPand

BGPredistributionModifyingAdministrativeDistancedistanceeigrpinternal-distanceexternal-distanceRouter(config-router)#UsedforEIGRPredistributionExample:RedistributionUsingAdministrativeDistanceExample:RedistributionUsingAdministrativeDistance(Cont.)routerospf1redistributeripmetric10000metric-type1subnetsnetwork172.31.0.00.0.255.255area0!routerripversion2redistributeospf1metric5network10.0.0.0noauto-summaryrouterospf1redistributeripmetric10000metric-type1subnetsnetwork172.31.3.20.0.0.0area0!routerripversion2redistributeospf1metric5network10.0.0.0noauto-summaryRouterP3R1RouterP3R2Example:RedistributionUsingAdministrativeDistance(Cont.)Example:RedistributionUsingAdministrativeDistance(Cont.)hostnameP3R1!routerospf1redistributeripmetric10000metric-type1subnetsnetwork172.31.0.00.0.255.255area0

distance1250.0.0.0255.255.255.25564!routerripversion2redistributeospf1metric5network10.0.0.0noauto-summary!access-list64permit10.3.1.0access-list64permit10.3.3.0access-list64permit10.3.2.0access-list64permit10.200.200.31access-list64permit10.200.200.34access-list64permit1