CCNA Guide to Cisco Networking Fundamentals Fourth Edition

1、CCNA Guide to Cisco Networking Fundamentals Fourth EditionChapter 6Router Startup and ConfigurationCCNA Guide to Cisco Networking Fundamentals, Fourth Edition2ObjectivesDescribe the steps involved in starting a routerDescribe and use the Cisco Discovery ProtocolConfigure IP on the Cisco routerTroubl

2、eshoot router connectivity problemsCCNA Guide to Cisco Networking Fundamentals, Fourth Edition3Router StartupIn general, the boot process follows these steps:Test hardware (POST)Load the bootstrap programLocate and load the Cisco IOSLocate and load the router configuration fileCCNA Guide to Cisco Ne

3、tworking Fundamentals, Fourth Edition4CCNA Guide to Cisco Networking Fundamentals, Fourth Edition5Test Hardware (POST)Read-only memory (ROM) in a routerTypically contains the power-on self-test (POST), the bootstrap program, and often a version of the operating systemPOST is a diagnostic test that d

4、etermines if the hardware is operating correctlyDuring the POST, the bootstrap program, also called the ROM Monitor, checks basic operations of the attached hardwareThe ROM Monitor checks the configuration register for instructions regarding how to load the Cisco IOSCCNA Guide to Cisco Networking Fu

5、ndamentals, Fourth Edition6Router Configuration Filesstartup-configThe router configuration file that loads during the boot processSometimes referred to as the backup configuration Because it is the saved version of the configuration fileTo revert to the settings in your startup-configReboot the sys

6、tem by powering the router off and back on again orIssue the reload command at the privileged EXEC mode promptCCNA Guide to Cisco Networking Fundamentals, Fourth Edition7Router Configuration Files (continued)Note that when you copy over the startup configuration in NVRAM, that file is replacedWhen y

7、ou copy to the running configuration in RAM, the configuration files are blendedTo view the contents of the startup-configType show startu-pconfig or just show start at the enable promptTo see your working or running configurationType show running-config or just show run at the enable promptCCNA Gui

8、de to Cisco Networking Fundamentals, Fourth Edition8CCNA Guide to Cisco Networking Fundamentals, Fourth Edition9Methods for Making ChangesYou can usually implement and test changes without saving them to the startup configurationBasic steps to implement changes:Make changes as desired to the configu

9、rationExamine those changesDetermine if the changes meet the desired resultRemove the changes if they do not meet the desired result, or simply reboot the routerCopy the changes from the running configuration to the startup configuration when they do meet the desired resultCCNA Guide to Cisco Networ

10、king Fundamentals, Fourth Edition10IP on the RouterTo manually configure IP on an interfaceYou must first change to interface configuration modeThen, you can use the ip address command to configure an IP address for the specific interfaceIn the event you are configuring a serial interface as a DCE (

11、data communication equipment)You will also need to add the clockrate bandwidth in bits per second commandCCNA Guide to Cisco Networking Fundamentals, Fourth Edition11IP ConnectivityCCNA Guide to Cisco Networking Fundamentals, Fourth Edition12TelnetTelnetUtility that connects at the highest layer of

12、the OSI model and provides remote access to other devicesCisco routers allow telnet connections via their virtual terminal portsIf you can establish telnet connectivity to a routerIt is available on the network and you have connectivity at all layersCCNA Guide to Cisco Networking Fundamentals, Fourt

13、h Edition13IP Host NamesSometimes, you cannot gain connectivity because the host name that you are trying to connect with is entered in a table incorrectlyTo determine the address to name mapping on your router, type:router#show hostsTo add an entry to your hosts file for name resolutionGo to global

14、 configuration mode and type: CCNA Guide to Cisco Networking Fundamentals, Fourth Edition14IP Host Names (continued)To remove that entry, type:To allow a name server to handle the IP address to name resolution, type:CCNA Guide to Cisco Networking Fundamentals, Fourth Edition15Ping and TracePing and

15、Trace verify connectivity at the Internetwork layer of the TCP/IP modelPing can return the following replies:! Successful receipt of the ICMP echo. Request timed outUDestination was unreachableCCongestion experiencedIPing interrupted?Packet type unknown&Packet TTL exceededCCNA Guide to Cisco Network

16、ing Fundamentals, Fourth Edition16Ping and Trace (continued)Using the ping command aloneReferred to as extended mode pingAllows you to enter your ping command step by stepTrace sends multiple ICMP packets with progressively higher time-to-live counters (TTL) Until the packet reaches the destinationC

17、CNA Guide to Cisco Networking Fundamentals, Fourth Edition17Ping and Trace (continued)The following responses can be returned by a trace:!H Indicates that a router received, but did not forward, the ICMP echo requestP Protocol unreachableN Network unreachableU Port unreachable* Request timed outCCNA

18、 Guide to Cisco Networking Fundamentals, Fourth Edition18IP RouteIf you cannot get connectivity using Ping or Trace, you should check your routing tableIssue the show ip route command from the enable mode promptTo display the routing tableTypically, routing tables are dynamically created when routin

19、g protocols are configured on the routerIf you want, you can use the ip route command from the global configuration modeTo statically enter routes in the routing tableCCNA Guide to Cisco Networking Fundamentals, Fourth Edition19Checking the Interfaceshow interfaces commandCheck the configuration of

20、a specific interface from the enable mode promptExample: router#show int s0/0RepliesSerial0/0 is up, line protocol is upSerial0/0 is up, line protocol is downSerial0/0 is up, line protocol is administratively downSerial0/0 is down, line protocol is downCCNA Guide to Cisco Networking Fundamentals, Fo

21、urth Edition20CCNA Guide to Cisco Networking Fundamentals, Fourth Edition21Checking the Interface (continued)Clear countersThe router keeps detailed statistics regarding data passing across its interfacesTo clear the counters for interface f0/0, type:router#clear interface f0/0debug commandOne of th

22、e most powerful tools you can use to obtain information from your routerTool is only available from privileged EXEC modeDebug has numerous subcommandsCCNA Guide to Cisco Networking Fundamentals, Fourth Edition22CCNA Guide to Cisco Networking Fundamentals, Fourth Edition23CDPCisco Discovery Protocol

23、(CDP)Cisco proprietary Data Link layer protocolShares configuration information between Cisco devices that are connected directly to each otherAll Cisco devices can use CDP to:Discover each otherLearn about the configurations of other devicesUsing CDP can help you quickly determine the network topol

24、ogyCDP was designed to be a low-overhead protocolCCNA Guide to Cisco Networking Fundamentals, Fourth Edition24CDP (continued)CCNA Guide to Cisco Networking Fundamentals, Fourth Edition25Cisco IOSCisco IOS is usually loaded from flash memoryIf the router cannot find the IOS in flash memory, it will l

25、ook for a copy on a TFTP serverIf it cannot find one there, it will boot a minimal version of the IOS from ROMIf you want to see information about your routers flash memory:Type show flash from the enable mode promptCCNA Guide to Cisco Networking Fundamentals, Fourth Edition26CCNA Guide to Cisco Net

26、working Fundamentals, Fourth Edition27Cisco IOS (continued)CCNA Guide to Cisco Networking Fundamentals, Fourth Edition28Configuration RegisterEvery Cisco router has a 16-bit configuration register, which is stored in NVRAMThis register allows you to control several boot functions:Forcing the system

27、into the bootstrap programEnabling or disabling the console Break functionSetting the console terminal baud rateLoading the IOS from ROMLoading the IOS from a TFTP serverExamine the configuration register by typing show versionCCNA Guide to Cisco Networking Fundamentals, Fourth Edition29CCNA Guide t

28、o Cisco Networking Fundamentals, Fourth Edition30Configuration Register (continued)CCNA Guide to Cisco Networking Fundamentals, Fourth Edition31ROM Monitor ModeROM Monitor modeThe bootstrap program that is built into the firmware of the routerUsed to initialize the hardware and load the IOSROM Monit

29、or can be used to perform other tasks such as diagnostics and recovering passwordsConfigure your system to enter ROM Monitor modeEnter the following command at the global configuration prompt:router(config)#config-register 0 x2100CCNA Guide to Cisco Networking Fundamentals, Fourth Edition32ROM Monit

30、or Mode (continued)Configure your system to boot a smaller IOS image from ROM and enter RxBoot modeEnter the following command at the global configuration prompt:router(config)#config-register 0 x2101CCNA Guide to Cisco Networking Fundamentals, Fourth Edition33RxBoot ModeRxBoot modeA limited version

31、 of the IOSEntering RxBoot mode is often done intentionally When you want to access a TFTP server to download a new IOSIf your router enters RxBoot mode without your interventionIndicates that the router could not find a good IOS imagePrompt: router(boot)CCNA Guide to Cisco Networking Fundamentals,

32、Fourth Edition34Boot System CommandsAs long as the configuration register is configured with a 2 as the final hexadecimal digitThe ROM Monitor will look for boot system commands in NVRAM during the bootup processEnable your system to boot an IOS file from the TFTP serverIssue the following command f

33、rom global configuration mode:router(config)#boot system tftp somefile.binCCNA Guide to Cisco Networking Fundamentals, Fourth Edition35Backing Up and Restoring the IOScopy flash tftpThe command for backing up your IOS to a TFTP serverYou will be asked for the source filename, the IP address of the T

34、FTP server, and the destination filenameType erase flash at the privileged EXEC mode promptTo erase the IOSCCNA Guide to Cisco Networking Fundamentals, Fourth Edition36CCNA Guide to Cisco Networking Fundamentals, Fourth Edition37Upgrading the IOSBefore you load a new IOS file to your routerUse the s

35、how flash command to ensure there is enough free memory to hold itThe system will tell you how much memory is used and how much is freeIf there is not enough memory to hold both the current IOS image and the upgradeYou will have to erase the existing flash memory as previously mentionedCCNA Guide to

36、 Cisco Networking Fundamentals, Fourth Edition38Router Password RecoveryPassword recoveryProcess that allows you to get into the router without the necessary passwordsYou must be physically connected to the router using the console cableSteps to perform password recovery on the Cisco 2600 series:Con

37、nect to the router from a PC using the console port and the HyperTerminal programEnter the show version command and record the value of the configuration registerCCNA Guide to Cisco Networking Fundamentals, Fourth Edition39Router Password Recovery (continued)Steps to perform password recovery on the

38、 Cisco 2600 series: (continued)Turn the router off and on using the power switchPress Ctrl+Break several times within the first 60 seconds of bootupAt the rommon 1 prompt, type confreg 0 x2142 and press EnterEnter the reset command at the rommon 2 promptEnter no if asked to enter the system configur

39、ation dialogEnter enable to get to privileged modeCCNA Guide to Cisco Networking Fundamentals, Fourth Edition40Router Password Recovery (continued)Steps to perform password recovery on the Cisco 2600 series: (continued)Enter the copy start run command to load the saved configuration file from NVRAM

40、into RAMEnter the show run command to view the configurationTo change the enable secret command, enter the following commands:Router#config tRouter(config)#enable secret secret passwordCCNA Guide to Cisco Networking Fundamentals, Fourth Edition41Router Password Recovery (continued)Steps to perform p

41、assword recovery on the Cisco 2600 series: (continued)Enter config-register 0 x2102 at the global configuration mode prompt to make sure the router reboots in the default mannerEnter the copy run start command to save your changesCCNA Guide to Cisco Networking Fundamentals, Fourth Edition42Security

42、Device ManagerSecurity Device Manager (SDM)A Web-based tool primarily used for implementing and testing security configurationsCommonly used to configure routing protocols, WAN services, wireless routing, firewalls, virtual private networks (VPNs), and quality of service (QoS)SDM is typically not used to configure basic functionality on a Cisco router In fact, SDM cannot do all thingsCCNA Guide to Cisco Networking Fundamentals, Fourth Edition43