Discovery-Network-Design-Chapter-1-EN（思科網(wǎng)絡(luò)技術(shù)學(xué)院CCNA4.0 官方資料-CCNA Discovery- CAC建議版Discovery- 英文版- D4-Network-Design-EN）

IntroducingNetworkDesignConceptsDesigningandSupportingComputerNetworks–Chapter1ObjectivesExplainhowahierarchicalnetworkdesigncreatesastable,reliable,scalablenetworkExplainwhatfactorsneedtobeconsideredwhentheCoreLayerofanetworkisdesignedandimplementedExplainwhichfactorsneedtobeconsideredwhentheDistributionLayerofanetworkisdesignedandimplementedExplainwhichfactorsneedtobeconsideredwhentheAccessLayerofanetworkisdesignedandimplementedDescribethebenefitsandsecurityimplicationsofcreatingserverfarmsDescribetheconsiderationsofanimplementationofawirelessnetworkdesignDescribethefactorsthataffecttheimplementationofVPNs,includinghowremoteworkerscanbesupportedContentIndex1.1DiscoveringNetworkDesignBasics1.2InvestigatingCoreLayerDesignConsiderations1.3InvestigatingDistributionLayerDesignConsiderations1.4InvestigatingAccessLayerDesignConsiderations1.5InvestigatingServerFarmsandSecurity1.6InvestigatingWirelessNetworkConsiderations1.7SupportingWANandRemoteWorkers1.8ChapterSummary1.1DiscoveringNetworkDesignBasics

1.1.1NetworkDesignOverviewBuildingaGoodNetwork:Donothappenbyaccident.Hardworkbynetworkdesignersandtechnicians.

Designers

needtoidentifynetworkrequirementsandselectthebestsolutionstomeettheneedsofabusiness.1.1.1NetworkDesignOverviewUpallthetimeReliableSecureEasytomodifyFastrecoveryReasonableresponsetimeEasytotroubleshootingNetworkrequirements:1.1.1NetworkDesignOverviewFourFundamentalNetworkDesignGoals:ScalabilityAvailabilitySecurityManageability1.1.2TheBenefitsofaHierarchicalNetworkDesignCoreLayer:connectsDistributionLayerdevicesDistributionLayer:interconnectssmallerLANsAccessLayer:providesconnectionsforhostsandenddevices1.1.2TheBenefitsofaHierarchicalNetworkDesignThebenefitofdividingaflatnetworkintosmaller,moremanageableblocksisthatlocaltrafficremainslocal.Onlytrafficthatisdestinedforothernetworksismovedtoahigherlayer.Layer2devicesinaflatnetworkprovidelittleopportunitytocontrolbroadcastsortofilterundesirabletraffic.1.1.2TheBenefitsofaHierarchicalNetworkDesignCiscoEnterpriseArchitecturesSubdividetheThree-layerModelintoModularAreas:EnterprisecampusServerfarmEnterpriseedge1.1.2TheBenefitsofaHierarchicalNetworkDesignThemodularframeworkoftheCiscoEnterpriseArchitectureshasthefollowingdesignadvantages:AddservicesandsolutionswithoutchangingtheunderlyingnetworkdesignCreatesdeterministicnetworkEasesthedesigntaskProvidesscalability1.1.2TheBenefitsofaHierarchicalNetworkDesign1.1.3NetworkDesignMethodologiesStepsinnetworkdesignprojects:Identifythenetworkrequirements:BusinessgoalsandTechnicalrequirementsCharacterizetheexistingnetwork:gatherandanalyzethecurrentnetworkandservicesDesignthenetworktopologyandsolutions:takeatop-downapproach1.1.3NetworkDesignMethodologiesDeterminingtheScopeoftheProject:impactingtheentirenetwork:AddingnewnetworkapplicationsandmakingmajorchangestoexistingapplicationsImprovingtheefficiencyofnetworkaddressingorroutingprotocolchangesIntegratingnewsecuritymeasuresAddingnewnetworkservicesRelocatingserverstoadatacenterserverfarm1.1.3NetworkDesignMethodologiesDeterminingtheScopeoftheProject:impactingtheportionnetwork:ImprovingInternetconnectivityandaddingbandwidthUpdatingAccessLayerLANcablingProvidingredundancyforkeyservicesSupportingwirelessaccessindefinedareasUpgradingWANbandwidth1.2InvestigatingCoreLayerDesignConsiderations

1.2.1WhathappensattheCoreLayer?calledthe

NetworkbackboneGoalsoftheCoreLayerProvide100%uptimeMaximizethroughputFacilitatenetworkgrowthCoreLayerTechnologiesRoutersormultilayerswitchesRedundancyandloadbalancingHigh-speedandaggregatelinksRoutingprotocolsthatscalewellandconvergequickly1.2.1WhathappensattheCoreLayer?ImplementingredundantlinksattheCoreLayerensuresthatnetworkdevicescanfindalternatepathstosenddataintheeventofafailure.MostCoreLayersinanetworkarewiredineitherafullmeshorpartialmeshtopology.Forlargerinstallations,amodifiedpartialmeshtopologyisused.1.2.1LAB;WhathappensattheCoreLayer?1.2.2NetworkTrafficPrioritizationPreventingNetowrkFailures:DeviceRequimentDualpowersuppliesandfansAmodularchassis-baseddesignAdditionalmanagementmodulesHot-swappablecomponentsUPS

Reducinghumanerror1.2.3NetworkConvergenceNetworkconvergenceoccurswhenallroutershavecompleteandaccurateinformationaboutthenetwork.Thefastertheconvergencetime,thequickeranetworkcanreacttoachangeintopology.Factorsthataffectconvergencetimeinclude:Routingupdatesand

DeterminingthebestpathsEIGRPorOSPFprovidethemoststableroutingsolution.DesignConsiderations:DynamicroutesStaticroutesAddressingSummarization

1.2.3LAB:NetworkConvergence1.3InvestigatingDistributionLayerDesignConsiderations1.3.1WhathappensattheDistributionLayer?TheAccessLayeriscommonlybuiltusingLayer2switchingtechnology.TheDistributionLayerisbuiltusingLayer3devices.Routersormultilayerswitches,locatedattheDistributionLayer,providemanyfunctions:FilteringandmanagingtrafficflowEnforcing

AccesscontrolpoliciesRoutesummarizationIsolatingCoreLayerfromAccessLayerfailuresRoutingbetweenVLANs1.3.1WhathappensattheDistributionLayer?TrunksareusedtocarrytrafficthatbelongstomultipleVLANsbetweendevicesoverthesamelink.WhenredundantlinksexistbetweendevicesintheDistributionLayer,thedevicescanbeconfiguredtoloadbalancethetrafficacrossthelinks.WhentheDistributionLayerdevicesarelocatedinthesamewiringclosetordatacenter,theyareinterconnectedusingGigabitlinks.Whenthedevicesareseparatedbylongerdistances,fibercableisused.1.3.1LAB:WhathappensattheDistributionLayer?1.3.2LimitingtheScopeofNetworkFailureAfailuredomaindefinestheportionofthenetworkthatisaffectedwheneitheradeviceornetworkapplicationfails.1.3.2LAB:LimitingtheScopeofNetworkFailure1.3.3BuildingaRedundantNetwork802.1d——STP802.1w——RSTPInastablenetwork,STPrecalculationsareinfrequent.1.3.4TrafficFilteringattheDistributionLayerACLsareatoolthatcanbeusedattheDistributionLayertolimitaccessandtopreventunwantedtrafficfromenteringtheCorenetwork.StandardACLsfiltertrafficbasedonthesourceaddress.ExtendedACLscanfilterbasedonSourceaddress,Destinationaddress,Protocols,Portnumbersorapplications.TherecanbeoneACLperprotocolperdirectionperinterface.StandardACLsshouldbeappliedclosesttothedestination.ExtendedACLsshouldbeappliedclosesttothesource.ComplexACLs:dynamic,reflexive,andtime-based.ACLsfiltertrafficforsecurityandtrafficmanagement1.3.4TrafficFilteringattheDistributionLayer1.3.4LAB:TrafficFilteringattheDistributionLayer1.3.4LAB:TrafficFilteringattheDistributionLayerRoutesummarizationhasseveraladvantagesforthenetwork:Onerouteintheroutingtablethatrepresentsmanyotherroutes,creatingsmallerroutingtablesLessroutingupdatetrafficonthenetworkLoweroverheadontherouterRIPv2,EIGRP,OSPF,andIS-IScansupportroutesummarization

1.3.5RoutingProtocolsattheDistributionLayer1.4InvestigatingAccessLayerDesignConsiderations

1.4.1WhatHappensattheAccessLayer?TheAccessLayerrepresentstheedgeofthenetworkwhereenddevicesconnect.TheaccesscanbeeitherthroughapermanentwiredinfrastructureorthroughwirelessAccessPoints.1.4.1WhatHappensattheAccessLayer?ManydifferentdevicescanconnecttoanIPnetwork,including:IPtelephones,Videocameras,Videoconferencingsystems.Thesenewtypesofenddevices,andtheassociatedapplicationsandservices,changetherequirementsforscalability,availability,securityandmanageabilityattheAccessLayer.RedundantcomponentsandfailoverstrategiescanbeimplementedattheAccessLayertoimprovereliabilityandincreaseavailabilityfortheenddevices.1.4.1WhatHappensattheAccessLayer?NamingstructuresVLANarchitectureTrafficpatternsPrioritizationstrategiesFollowinggooddesignprinciplesimprovesthemanageabilityofthenetworkby:EnsuringthatthenetworkdoesnotbecometoocomplexAllowingeasytroubleshootingwhenthereisaproblemMakingiteasiertoaddnewfeaturesandservicesinthefuture1.4.1LAB:WhatHappensattheAccessLayer?1.4.2NetworkTopologiesattheAccessLayer1.4.2NetworkTopologiesattheAccessLayerTheadvantagesofastartopologyinclude:

EasyinstallationMinimalconfigurationThedisadvantagesofastartopologyaresignificant:

Thecentraldevicerepresentsasinglepointoffailure.Thecapabilitiesofthecentraldevicecanlimitoverallperformanceforaccesstothenetwork.Thetopologydoesnotrecoverintheeventofafailurewhentherearenoredundantlinks.1.4.2LAB:NetworkTopologiesattheAccessLayer1.4.3HowVLANsSegregateandControlNetworkTrafficFunctionsofVLANs:SeparateandclassifytrafficControlbroadcastsContainVLANswithinasinglewiringcloset1.4.3LAB:HowVLANsSegregateandControlNetworkTraffic1.4.4ServicesattheNetworkEdgeQOS:ClassificationAssignedpriority1.4.5SecurityattheNetworkEdgeUsererrorandcarelessnessaccountforasignificantnumberofnetworksecuritybreaches.AuthenticationWirelesssecurity1.4.5LAB:SecurityattheNetworkEdge1.4.6SecurityMeasuresattheAccessLayerPhysicalsecurityStrongpasswordsSSHDisablingunusedportsSecuritypolicy1.4.6LAB:SecurityMeasuresattheAccessLayer1.4.6LAB:SecurityMeasuresattheAccessLayer1.5InvestigatingServerFarmsandSecurity

1.5.1WhatisaServerFarms?Creatingaserverfarmhasthefollowingbenefits:makesiteasiertosecure,filter,andprioritizetrafficRedundant,high-capacitylinksLoadbalancingandfailoverLowercostofprovidingservices1.5.1LAB:WhatisaServerFarms?1.5.2Security,Firewalls,andDMZsDatacenterserverscanbethetargetofmaliciousattacksandmustbeprotected.FirewallsLANswitchsecurityfeaturesIntrusionandpreventionsystemsLoadbalancersNetworkanalysisandmanagementdevicesDMZs1.5.2Security,Firewalls,andDMZs1.5.3HighAvailabilityofCreatingServerFarmsBuildinginredundancyforhighavailabilityVirtualization1.5.3LAB:HighAvailabilityofCreatingServerFarms1.6InvestigatingWirelessNetworkConsiderations

1.6.1ConsiderationsUniquetoWLAN

Customerrequirements:RoamingAuthenticationServicesandapplicationsEncryptionCoverageareaS

Numberofusers1.6.1ConsiderationsUniquetoWLANUnderstandingCustomerRequirementsPhysicalWLANdesignSitesurveyLogicalWLANdesign1.6.2ConsiderationsUniquetoWLANOpenguestaccessNOWiredEquivalentPrivacy(WEP)orWi-FiProtectedAccess(WPA)encryptedBroadcastSSIDSecuredemployeeaccessNon-broadcastSSIDStrongencryptionUserauthenticationVirtualPriv