俄勒冈大学网络设计03CoreNetworkDesignv2.ppt

CampusNetworkingWorkshop CoreNetworkDesign RoutingArchitectures Wheredoweroute Atthepointwherewewanttolimitourlayer 2broadcastdomainAtyourIPsubnetboundaryWecancreatemorecomplextopologiesusingroutersandatthesametimekeepthingssane RoutingArchitectures IfwestartwiththerighttopologyitwillmakeournetworkmorestableUseahierarchicalapproachthatmakesgooduseofyourtrafficpatternsandIPaddressallocationsBeawarethattopologyandlogicaldesignarenotthesame RoutingArchitectures Whatistherighttopology ContinuetothinkofthreelayersAccessDistributionCoreThinkingoflayershelpsreduceconvergencetimebecauseofthescopeofinformationtoprocessTheselayersshouldnotbeconfusedwithyourL2architecture RoutingArchitectures RoutingArchitectures AccessLayerMinimumroutinginformationFeedstrafficintothenetworkLinksizingProvidesnetworkaccesscontrolNospoofingNobroadcastsourcesNodirectedbroadcastsProvidesotheredgeservicesTaggingforQoSTunnelterminationTrafficmeteringandaccountingPolicy basedrouting RoutingArchitectures DistributionLayerGoalsIsolatestopologychangesControlstheroutingtablesizeAggregatestrafficStrategiesRoutesummarizationMinimizethenumberofconnectionstothecore RoutingArchitectures CoreLayerGoalForwardingpacketsfastStrategiesClearofnetworkpoliciesEverydevicehasfullreachabilitytoeverydestinationFacilitatescoreredundancyReducessuboptimalroutingPreventsroutingloops RoutingArchitectures DependinginhowlargeyourcampusisyoucouldusethetypicalhierarchicalmodelorasubsetTwocollapsecoremodelsSinglerouteractsasthenetworkcoreAllotherroutersinthedistributionlayerSinglerouteractsasthenetworkcoreNodistributionlayerAllaccesslayerroutersconnectedtothecore RoutingArchitectures RoutingArchitectures WhattodoaboutyouraddressspaceAssignitasyouneedit WRONG Poorsummarizationhasanimpactonyournetwork sstabilityVerydifficulttocorrectpoorallocationsSpendsometimethinkingabouthowyouwillassignaddressspaceRoutingstabilityisaffectedbythenumberofroutespropagatedthroughyournetwork RoutingArchitectures RoutingArchitectures WhathappensifthelinktorouterDfails Howisthedistributionlayeraffected Howisthecorelayeraffected WhatchangescanImaketomyaddressallocationandaddresssummarizationtominimizetheimpactofalinkfailureonconvergencetimeandnetworkstability RoutingArchitectures RoutingArchitectures Whereshouldyousummarize OnlyprovidefulltopologywhereitisneededCoreroutersdon tneedtoknowabouteverysinglenetworkAccessroutersdon tneedtoknowhowtogettoeveryothernetworkTheyshouldonlycarryenoughinformationtoreachone oracoupleof distributionrouter s SummarizeatthehierarchyedgesDistributionlayertocoreDistributionlayertoaccess RoutingArchitectures StrategiesforSuccessfulAddressingFirstcome firstserveStartwithalargepoolandhandthemoutasneededPoliticallyDividethespacesoeachgroupwithintheorganizationhaveapoolofaddressesavailableGeographicallyDividethespacesothateverylocationhasapoolofaddressesavailableTopologicallyAssignaddressesbasedonthepointofattachmenttothenetwork maybesameasgeographically RoutingArchitectures Addressing Summarization Easyforyoutosay Ialreadyhavemynetworkrunninganditlooksnothinglikewhatyoushow YouarenotaloneTheprinciplesstillapplyTakeitslowly Defineagoalandstartworkingtowardsit Itcantakeyears MaybewecandotherightthingwithIPv6 HighAvailability Howcanweachievehighavailability IntroducehardwareresiliencyandbackuppathsintoyournetworkDependingonthelayer youwillusetechniquesdifferentlyTheideaistoprotectyournetworkagainstasingledevicefailureaffectingallofyournetworkDirectrelationshipbetweenreliability complexityandcostsThetrickistobalanceallvariablesandcomeupahead HighAvailability YouneedtoevaluateyourneedsMinimalneedNetworkjustneedstobeupforaportionofthedayDowntimeiseasilyscheduleafterworkinghoursBusinessisnotimpactedifthenetworkisdownUsers productivityisnotimpactedbyanetworkfailure HighAvailability MediumneedNetworkneedstobeavailableformostofthedayOnlycentralizedserversneedtobeup24hours dayDowntimeneedstobescheduledonweekendsIfcriticalpartsofthenetworkfail thebusinessoperationisimpactedAnetworkfailureaffectsuserproductivity HighAvailability HighneedNetworkneedstobeup24x7DowntimeneedstobescheduledwellinadvanceandcompletedwithinscheduleAnetworkfailurecausesmajorlossofbusinessUserproductivitydrasticallyimpactedbyanetworkfailure HighAvailability MethodsComponentRedundancyDuplicateorbackuppartsPowersupplies fans processors etc HavespareshandyServerRedundancyProtectyourdatawithbackupsUseofhotstandbyserversOrbetteryetuseloadbalancerstodistributeaccessNetworkLink DataPathRedundancyProvidephysicalredundantconnectionsbetweendevicesAllowforhotbackuppaths STP andparallelism routing HighAvailability CorelayerBuildadualroutercoreandprovidedualpathstoitfromyourdistributionlayerThesecouldbeeitherL2orL3pathsMakesurethatyouhaveredundantpowersuppliesinyourdevicesThisalsoassumestwodifferentsourcesofpowerThinkofUPSprotectedcircuitsMaybeevenapowerinvertersolutionforemergenciesThinkaboutthepossibilityofdualrouting forwardingenginesWeighthisagainsttheuseoftwodevicesOrjustthrowthatinthereasyetanotherlayerofreliability HighAvailability CorelayerYouwanttoalsobalanceReductionofthehopcountReductionoftheavailablepathsIncreaseofthenumberoffailurestowithstandEasytodoinasinglelocationbutcomplexityandcostsdirectlyproportionaltothenumberanddistancebetweenthelocations HighAvailability DistributionLayerProvidedualconnectionstothecoreOrprovidearedundantlinktootherdistributionlayerdevicesDoublesthecore sroutingtablesizePossibleuseoftheredundantpathfortraffictransitingthecorePreferringtheredundantlinktothecorepathRoutinginformationleaksAllowfordual homingofAccesslayerdevices HighAvailability DistributionLayer MakesurethatyouhaveredundantpowersuppliesinyourdevicesThisalsoassumestwodifferentsourcesofpowerThinkofUPSprotectedcircuitsMaybeevenapowerinvertersolutionforemergenciesThinkaboutthepossibilityofdualrouting forwardingenginesWeighthisagainsttheuseoftwodevicesOrjustthrowthatinthereasyetanotherlayerofreliabilityIncreasesthecostofthedistributionlayer HighAvailability AccessLayerSamechallengesandsolutionsasthedistributionlayerDualhometothesamedistributionlayerbranchMakesuretorestrictdestinationsadvertisedtopreventtransittrafficthroughtheaccesslayerrouterAlternatepathtoanotheraccesslayerdeviceDon tusetheredundantlinkfornormaltrafficMakesuretorestrictdestinationsadvertisedtopreventtransittrafficthroughtheaccesslayerrouter HighAvailability AccessLayerDualhometodifferentdistributionlayerbranchesDon tusetheredundantlinkfornormaltrafficMakesuretorestrictdestinationsadvertisedtopreventtransittrafficthroughtheaccesslayerrouter HighAvailability HighAvailability HighAvailability HighAvailability SoIbuiltallthisredundancyandhighavailabilityinmynetwork howcanmyenduserstakeadvantageofit YouarealreadyprovidingmorethatonerouterforasegmentYouwanttoprovideyouruserswithawaytomovetheirtrafficfromonedefaultgatewaytoanother HighAvailability IfoneoftheroutersfailstheotheronewillcontinuetoprovideservicestothesegmentBeawarethatredundancyisnotthesameasloadbalancing HighAvailability Howcanweaccomplishthat Havetheroutersdoproxy ARP Yikes Runaroutingprotocolbetweenyourworkstationsandtherouters Yikes SplityourworkstationsintotwogroupsOneusesonerouterasitsdefaultgatewayTheothergroupusestheotherrouterUseICMPRouterDiscoveryProtocol IRDP Thereisgottobitabetterandsimplerwaytodothis HighAvailability Currentsolutions HotStandbyRedundancyProtocol HSRP CiscoProprietary RFC2281 VirtualRouterRedundancyProtocol VRRP RFC3768 GatewayLoadBalancingProtocol GLBP CiscoProprietary HighAvailability TheconceptisverysimilarWorkstationsgetconfiguredwithasingledefaultgatewayTheroutersinthesegmentwillnegotiatewhowillprovideservicestotheworkstationsandkeeptrackofthestateoftheotherroutersIntheeventofaprimary activerouterfailure oneofthestandbyrouterswilltakeoverthetaskofforwardingtrafficfortheworkstationsandbecometheprimary activeTraffictotheworkstationswillgototheprimary activerouterIncomingtrafficintothesegmentwillfollowtheroutingdecisionsmadebyroutersinthenetwork HighAvailability HSRP HighAvailability VRRP HighAvailability GLBP HighAvailability WhichoneshouldIuse TheyallallowforacommondefaultgatewayandMACaddressVRRPisstandardizedHSRP GLBPareCiscoproprietaryGLBPprovidesloadbalancingHSRP VRRPdonot withoutintroducingcomplexity GLBP HSRPcantrackanuplinkinterfaceVRRPdoesnot HighAvailability VRRPcanreusethedefaultgatewayIPHSRPdoesnotHSRP GLBPsupportIPv6VRRPdoesnotyetVRRPusesprotocol112 224 0 0 18HSRPusesUDP 1985 224 0 0 2GLBPusesUDP 3222 224 0 0 102 RoutingProtocols So nowIknowwhatmynetworkisgoingtolooklike oristhattrue Weneedtofigureouthowpacketswillbeforwarded ThatisafunctionoftherouterandtheroutingprotocolsthatwewillimplementTherearemanyoptionsRIPv2 EIGRP OSPF IS IS BGP RoutingProtocols RoutingprotocolscanbeclassifiedinInteriorGatewayProtocols IGP RIP EIGRP OSPF IS ISWewilltalkaboutOSPFlateronExteriorGatewayProtocols EGP BGPWewilltalkaboutBGPlateron RoutingversusForwarding Routing buildingmapsandgivingdirectionsForwarding movingpacketsbetweeninterfacesaccordingtothe directions IPRouting findingthepath PathderivedfrominformationreceivedfromaroutingprotocolSeveralalternativepathsmayexistbestnexthopstoredinforwardingtableDecisionsareupdatedperiodicallyorastopologychanges eventdriven Decisionsarebasedon topology policiesandmetrics hopcount filtering delay bandwidth etc IProutelookup BasedondestinationIPpacket longestmatch routingmorespecificprefixpreferredoverlessspecificprefixexample packetwithdestinationof10 1 1 1 32issenttotherouterannouncing10 1 16ratherthantherouterannouncing10 8 IProutelookup R2 R3 R4 All10 8except10 1 16 10 1 16 BasedondestinationIPpacket IProutelookup Longestmatchrouting R2 R3 R4 All10 8except