F新版CCNA培训教材ch06

6ManagingYourNetworkDeviceCERTIFICATIONOBJECTIVES6.01RouterHardwareComponents6.02RouterBootupProcess6.03RouterConfigurationFiles6.04ChangesinYourNetwork6.05RouterIOSImageFiles6.06IOSTroubleshooting✓Two-MinuteDrillQ&ASelfTestCertPrs8/CCNACiscoCertifiedNetworkAssociateStudyGuide/Deal/222934-9/Chapter6BlindFolio6:1D:\omh\CertPrs8\934-9\ch06.vpMonday,August04,200311:43:17AMColorprofile:GenericCMYKprinterprofileCompositeDefaultscreenThischaptercoversimportantIOSfeaturesthatyoucanusetomanageyourIOSdevice.ManyofthesefeaturesaresupportedacrossallIOSdevices,butsomeofthemaresupportedononlycertaindevices.ThischapterfocusesonthesefeaturesastheyrelatetoCiscorouters,beginningwithhowtherouterbootsup,findsitsoperatingsystem,andloadsitsconfigurationfile,aswellashowtobackupandrestoreyourIOSimage.Therearemanytoolsthatyoucanuseonyourrouterfortroubleshootingconnectionproblems,includingtheCiscoDiscoveryProtocol(CDP),ping,trace,telnet,anddebug.Thesetoolsarediscussedattheendofthechapter.RouterHardwareComponentsEachIOSdevicehastwomaincomponents:hardwareandsoftware.AlmosteveryIOS-basedrouterusesthesamehardwareandfirmwarecomponentstoassistduringthebootupprocess,includingthefollowing:ROM(read-onlymemory),RAM(randomaccessmemory),flash,NVRAM(nonvolatileRAM),aconfigurationregister,andphysicalinterfaces.Allofthesecomponentscanaffecthowtherouterbootsup,findsitsoperatingsystemandloadsit,andfindsitsconfigurationfileandloadsit.Thefollowingsectionscoverthesecomponentsinmoredepth.Read-OnlyMemory(ROM)ThesoftwareinROMcannotbechangedunlessyouactuallyswapouttheROMchiponyourrouter.ROMisnonvolatile—whenyouturnoffyourdevice,thecontentsofROMarenoterased.ROMcontainsthenecessaryfirmwaretobootupyourrouterandtypicallyhasthefollowingfourcomponents:■POST(power-onself-test)Performstestsontherouter’shardwarecomponents.■BootstrapprogramBringstherouterupanddetermineshowtheIOSimageandconfigurationfileswillbefoundandloaded.■ROMMonitor(ROMMONmode)Amini–operatingsystemthatallowsyoutoperformlow-leveltestingandtroubleshooting,thepasswordrecoveryprocedure,forinstance.Toaborttherouter’snormalbootupprocedureofloadingtheIOS,usetheCTRL-BREAKcontrolsequencetoenterROMMONmode.ThepromptinROMMONmodeiseither““or“rommon,”dependingontheroutermodel.2Chapter6:ManagingYourNetworkDeviceCertPrs8/CCNACiscoCertifiedNetworkAssociateStudyGuide/Deal/222934-9/Chapter6D:\omh\CertPrs8\934-9\ch06.vpMonday,August04,200311:43:18AMColorprofile:GenericCMYKprinterprofileCompositeDefaultscreen■Mini-IOSAstripped-downversionoftheIOSthatcontainsonlyIPcode.ThisshouldbeusedinemergencysituationswheretheIOSimageinflashcan’tbefoundandyouwanttobootupyourrouterandloadinanotherIOSimage.Thisstripped-downIOSisreferredtoasRXBOOTmode.Ifyousee“Router(rxboot)#”inyourprompt,thenyourrouterhasbootedupwiththeROMIOSimage.NoteveryrouterhasaMini-IOSimage;ontheotherhand,somerouters,suchasthe7200,canstoreafull-blownIOSimagehere.OtherComponentsYourroutercontainsothercomponentsthatareusedduringthebootupprocess,includingRAM,flash,NVRAM,theconfigurationregister,andthephysicalinterfaces.Thefollowingparagraphsexplainthesecomponents.RAMislikethememoryinyourPC.Onarouter,it(inmostcases)containstherunningIOSimage;theactiveconfigurationfile;anytables(includingrouting,ARP,CDPneighbor,andothertables);andinternalbuffersfortemporarilystoringinformation,suchasinterfaceinputandoutputbuffers.TheIOSisresponsibleformanagingmemory.Whenyouturnoffyourrouter,everythinginRAMiserased.Flashisaformofnonvolatilememoryinthatwhenyouturntherouteroff,theinformationstoredinflashisnotlost.RoutersstoretheirIOSimageinflash,butotherinformationcanalsobestoredhere.Notethatsomelower-endCiscoroutersactuallyruntheIOSdirectlyfromflash(notRAM).FlashisslowerthanRAM,afactthatcancreateperformanceissues.NVRAMislikeflashinthatitscontentsarenoterasedwhenyouturnoffyourrouter.Itisslightlydifferent,though,inthatitusesabatterytomaintaintheinformationwhentheCiscodeviceisturnedoff.RoutersuseNVRAMtostoretheirconfigurationfiles.InnewerversionsoftheIOS,youcanstoremorethanoneconfigurationfilehere.RouterHardwareComponents3CertPrs8/CCNACiscoCertifiedNetworkAssociateStudyGuide/Deal/222934-9/Chapter6POSTperformsself-testsonthehardware.ThebootstrapprogrambringstherouterupandfindstheIOSimage.ROMMONcontainsamini-operatingsystemusedforlow-leveltestinganddebugging.TheMini-IOSisastripped-downversionoftheIOSusedforemergencybootingofarouterandisreferredtoasRXBOOTmode.AllofthesecomponentsarestoredinROM.D:\omh\CertPrs8\934-9\ch06.vpMonday,August04,200311:43:18AMColorprofile:GenericCMYKprinterprofileCompositeDefaultscreenTheconfigurationregisterisaspecialregisterintherouterthatdeterminesmanyofitsbootupandrunningoptions,includinghowtherouterfindstheIOSimageanditsconfigurationfile.Asyouwillseelaterinthischapter,youcanmanipulatethisregistertoaffecthowyourrouterbootsup.Everyrouterhasatleastoneportandonephysicalinterface.Portsaretypicallyusedformanagementaccess;theconsoleandauxiliaryportsareexamples.Interfacesareusedtomovetrafficthroughtherouter;theycanincludemediatypessuchasEthernet,FastEthernet,TokenR