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1、5Basic Switchand RouterConfigurationCERTIFICATION OBJECTIVES5.01IOS Introduction5.02IOS Basics5.03Basic Switch Configuration5.04Basic Router ConfigurationTwo-Minute DrillQ&ASelf TestCertPrs8/CCNA Cisco Certified Network Associate Study Guide/Deal/222934-9/Chapter 5Blind Folio 5:1D:omhCertPrs8934-9ch
2、05.vpMonday,August 04,2003 11:24:05 AMColor profile:Generic CMYK printer profileComposite Default screenThis chapter presents the basics of configuring the 1900 and 2950 Catalyst switchesas well as Cisco routers.As you continue throughout this book,you will build uponthese fundamental and important
3、concepts for accessing,configuring,and managingyour Cisco devices.I am making the assumption that you have never configured a Cisco devicebefore and therefore will begin with the very basics by explaining the operating system that thesedevices use,the advantages that Ciscos operating system provides
4、,and how to use some basicoperating system commands to configure your Cisco device.CERTIFICATION OBJECTIVE 5.01IOS IntroductionOne of the main reasons that Cisco is number one in the enterprise networking marketplace is their Internetwork Operating System(IOS).The IOS provides a similar functionto M
5、icrosoft Windows XP or Linux:it controls and manages the hardware it is runningon.Basically,the IOS provides the interface between you and the hardware,enablingyou to execute commands to configure and manage your Cisco device.Originally,theIOS was developed for Cisco routers,but over the last few ye
6、ars,Cisco has been portingthe IOS to its other platforms,including the Catalyst switches.Cisco has spent many years tweaking and tuning the IOS,as well as adding featuresas new technologies are introduced to the marketplace.Advantages of the IOS include:FeaturesThe IOS includes a wide array of featu
7、res for protocols and functionsthat provide connectivity,scalability,reliability,and security solutions fornetworks of any size.ConnectivityThe IOS supports a variety of data link layer technologies forthe LAN and WAN environments,including copper and fiber wiring as wellas wireless.ScalabilityThe I
8、OS supports both fixed and modular chassis platforms,enabling you to purchase the appropriate hardware for your needs,yet stillallowing you to leverage the same IOS CLI to reduce your management costs.ReliabilityTo ensure that your critical resources are always reachable,Ciscohas developed many prod
9、ucts and IOS features to provide network redundancy.SecurityWith the IOS,you can strictly control access to your network andnetworking devices in accordance with your internal security policies.2Chapter 5:Basic Switch and Router ConfigurationCertPrs8/CCNA Cisco Certified Network Associate Study Guid
10、e/Deal/222934-9/Chapter 5D:omhCertPrs8934-9ch05.vpMonday,August 04,2003 11:24:05 AMColor profile:Generic CMYK printer profileComposite Default screenBecause of the success of their IOS software,Cisco has grown from a garage-based routercompany to one of the largest companies in theworld in a little
11、over a decade.Most enterprisenetworks,as well as ISPs,use Cisco products inone form or another.Actually,a large portionof the Internet backbone is composed of Ciscoproducts.With the IOS coupled with a first-classservice and support team,few companies can compare to Cisco when it comes tocustomer sat
12、isfaction.Device StartupThere are actually many ways of accessing a Cisco device,including the following:console,auxiliary(only certain Cisco routers),telnet,web browser,and an SNMPmanagement station.A console interface provides serial connection access to a routerwith console access,you can enter c
13、ommands in a text-based mode.In order to accessyour Cisco device from a remote station,however,you first need to create a basicconfiguration,including IP addressing.Therefore,to perform your initial configurations,you need access to the console port of your Cisco device.Before you can actually begin
14、 configuring your Cisco device,you first have toconnect it to your network and set up a terminal connection to its console interface,as described in the Chapter 4.Here are the three steps your Cisco device goes throughwhen booting up:1.Perform hardware tests.2.Locate and load the IOS.3.Locate and ex
15、ecute the devices configuration file.Once you power on your Cisco device,hardware tests are performed to ensurethat it is operating correctly.These tests,power-on self tests(POST),are discussedin Chapter 4.After these tests have completed,the Cisco device finds and locatesthe IOS and then proceeds t
16、o load it.Once the IOS is loaded,the IOS then searchesfor the devices configuration and executes it.With steps 2 and 3,there are typicallyfallback measures that the Cisco device goes through if it cannot find an IOS orlocate a configuration file.As you will see in this chapter,and as you work with C
17、isco devices in a productionenvironment,each Cisco product is unique and may have its own methods for findingand loading its IOS and configuration file.As an example,a Catalyst 1900 switch,IOS Introduction3CertPrs8/CCNA Cisco Certified Network Associate Study Guide/Deal/222934-9/Chapter 5IOS stands
18、for InternetworkOperating System.Its advantages includefeatures,connectivity,scalability,reliability,and security.D:omhCertPrs8934-9ch05.vpMonday,August 04,2003 11:24:05 AMColor profile:Generic CMYK printer profileComposite Default screendirect from Cisco,comes with a defaultconfiguration already on
19、 it.This configurationis enough to allow the switch to perform basicswitching functions right out of the box.ACisco router,by contrast,requires some basicconfiguration in order to route traffic betweeninterfaces.Accessing the Command-Line Interface(CLI)How you access the IOS CLI on a Cisco device fo
20、r the first time depends on thekind of device that you are configuring.In almost every case,you will use the consoleinterface to initially interact with the device;however,gaining access to the CLI fromthe console port can be different from one device to another.On a Cisco router,forinstance,you are
21、 taken directly to the IOS CLI when you log in from the console port.If the IOS cannot find a configuration file for the router,the IOS takes you throughSetup mode,which is a basic configuration script that prompts you for information onhow you want to configure your router.However,on a Catalyst 190
22、0 switch,you arefirst taken to a menu-based interface where you must choose the option of configuringthe switch from the CLI.And a 1900 never takes you through Setup mode unless youphysically execute the command from the CLIto begin the script.Once you have configured your Ciscodevice via the consol
23、e port,you can then useother methods of accessing and changing itsconfiguration,such as telnetCisco calls thisvirtual terminal(VTY)TFTP,SNMP,or a webbrowser.Cisco has a variety of managementproducts to configure and manage your Cisco device,such as CiscoWorks 2000;however,the focus of this book is s
24、trictly on the IOS CLI.IOS DifferencesWhat you will see in this and consequent chapters is that even though both Ciscorouters and switches run the IOS,the commands used by these products are frequentlydifferent!In other words,how you configure a feature on a Cisco router might be,andprobably is,diff
25、erent than configuring the same feature on a Catalyst switch.This is even4Chapter 5:Basic Switch and Router ConfigurationCertPrs8/CCNA Cisco Certified Network Associate Study Guide/Deal/222934-9/Chapter 5Be familiar with the varioustypes of access to the IOS CLI:console andauxiliary ports for local
26、access and VTYs(telnet),TFTP,SNMP,and web browsers.When an IOS device bootsup,it runs P(this doesnt look like itscompleteshould there be more here?)D:omhCertPrs8934-9ch05.vpMonday,August 04,2003 11:24:06 AMColor profile:Generic CMYK printer profileComposite Default screentrue among Ciscos Catalyst s
27、witches:how you configure a certain feature on a 1900may be different from configuring the same feature on the 2950!However,you access the IOS and maneuver around the IOS access levels,as wellas using many of the management commands,the same way on all IOS products.This can become confusing to a Cis
28、co novice,where one command for a particularfeature is the same on all Cisco products,but configuring another feature might bedifferent on a Cisco router than on a Catalyst switch.Besides command differences between different products,such as routers andswitches,there may be command differences with
29、in a product line,Cisco routers,forinstance.As an example,Cisco sells different flavors of its IOS software for routers,depending on the features that you need.Or because of hardware differences,somecommands work on some routers but not on others.Interacting with the IOSTheCLIisacharacter-ortext-bas
30、edinterface.TointeractwiththeCLI,youonlyneedto type in commands,just as you would do when typing an essay in a text editor ora message in an e-mail program.You can even use functions like cut-and-paste withthe IOS CLI:you can copy the complete configuration of a router using a terminalemulatorscopyf
31、unction,pastethisintoatexteditor,makechangestotheconfiguration,selectandcopythenewconfiguration,andpasteallofthesecommandsbackintotheCLI.The CLI supports a command parser.Whenever you press theENTERkey,the IOSparses the command and parameters that you entered and checks for correct syntaxand options
32、.When you paste multiple commands into the CLI,the IOS still performsthis process for each command that is included in the paste function.If you made amistake with one command,the CLI parser will display an error message,but continuewith the next command in the pasted list.EXEC ModesEach Cisco devic
33、e supports different access modes.For CLI interaction,there areactually three modes:User EXECProvides basic access to the IOS,with limited commandavailability(basically simple monitoring and troubleshooting commands)Privilege EXECProvides high-level management access to the IOS,includingall commands
34、 available at User EXEC modeConfigurationAllows configuration changes to be made to the deviceIOS Introduction5CertPrs8/CCNA Cisco Certified Network Associate Study Guide/Deal/222934-9/Chapter 5D:omhCertPrs8934-9ch05.vpMonday,August 04,2003 11:24:06 AMColor profile:Generic CMYK printer profileCompos
35、ite Default screenBoth EXEC modes can be password-protected,allowing you to limit the people whocan access your device to perform management,configuration,and troubleshootingtasks.The next two sections cover the two EXEC modes.User EXEC ModeYour initial access to the CLI is via User EXEC mode,which
36、has only a limited numberof commands that you can execute.Depending on the Cisco devices configuration,youmight be prompted for a password to access this mode.This mode is typically used forbasic troubleshooting of networking problems.You can tell that you are in User EXECmode by examining the promp
37、t on the left-hand side of the screen:RouterIf you see a“character at the end of the information,then you know that youare in User EXEC mode.The information preceding the“is the name of the Ciscodevice.For instance,the default name of all Cisco routers is“Router,”whereas onthe 1900 switch,there is n
38、o name by default,and you see only the“sign at thebeginning of the line,like this:The 2950 switchs User EXEC prompt looks like this:Switch.These devicenames can be changed with the hostname command,which is discussed later inthis chapter.Privilege EXEC ModeOnce you have gained access to User EXEC mo
39、de,you can use the enable commandto access Privilege EXEC mode:Router enableRouter#Once you enter the enable command,if a Privilege EXEC password has beenconfigured on the Cisco device,you will be prompted for it.Upon successfullyauthenticating,you will be in Privilege EXEC mode.You can tell that yo
40、u are inthis mode by examining the CLI prompt.In the preceding code example,noticethat the“”changed to a“#.”6Chapter 5:Basic Switch and Router ConfigurationCertPrs8/CCNA Cisco Certified Network Associate Study Guide/Deal/222934-9/Chapter 5D:omhCertPrs8934-9ch05.vpMonday,August 04,2003 11:24:06 AMCol
41、or profile:Generic CMYK printer profileComposite Default screenWhen you are in Privilege EXEC mode,you have access to all of the User EXECcommandsaswellasmanymoreadvancedmanagementandtroubleshootingcommands.These commands include extended ping and trace abilities,managing configurationfiles and IOS
42、images,and detailed troubleshooting using debug commands.Aboutthe only thing that you cant do from this mode is to change the configuration of theCisco devicethis can only be done from Configuration mode.If you wish to return to User EXEC mode,from Privilege EXEC mode,use thedisable command:Router#d
43、isableRouterAgain,by examining the prompt,you can tell that you are now in User EXEC mode.Logging Out of Your DeviceYou can log out of your Cisco device from either User or Privilege EXEC mode by usingthe logout or exit command:Router#logout-or-Router#exitThe Catalyst IOS-based switches do not suppo
44、rt thelogoutcommand,but they do support theexitcommand.5.01.The CD includes a multimedia demonstration of logging in and outof a Cisco router.IOS Introduction7CertPrs8/CCNA Cisco Certified Network Associate Study Guide/Deal/222934-9/Chapter 5Know the three differentmodes in the IOSUser EXEC,Privileg
45、e EXEC,and Configuration modesand what youcan do in each mode.Use theenablecommand to go from User EXEC modeto Privilege EXEC mode.Use thedisablecommand to go from Privilege EXEC to UserEXEC modes and use theexitcommandto log out of the IOS device from eitherof these two modes.D:omhCertPrs8934-9ch05
46、.vpMonday,August 04,2003 11:24:06 AMColor profile:Generic CMYK printer profileComposite Default screenIOS BasicsNow that you know how to log in to and out of a Cisco device,the next few sectionsdescribe some of the features built into the CLI that will make your configuration andmanagement tasks eas
47、ier.These features include how to abbreviate commands,howto bring up detailed help on commands and their specific parameters,the output ofcommands,recalling commands,and editing commands.Command Abbreviation and CompletionThe CLI of the IOS allows you to abbreviate commands and parameters to theirmo
48、st unique characters.This feature is very useful for those of us that are physicallychallenged at typing.As an example,you could type en instead of enable whenyou want to go from User EXEC to Privilege EXEC mode,like this:Router enRouter#The Cisco device,internally,completes the command for you.Howe
49、ver,thecharacters that you enter must make the command unique.As an example,youcouldnt type just the letter e,since there are other commands that being with theletter e,such as exit.Context-Sensitive HelpOne of the more powerful features of the IOS is the support of context-sensitive help.Context-se
50、nsitive help is supported at all modes within the IOS,including User EXEC,Privilege EXEC,and Configuration modes.There are a variety ways to use this feature.If you are not sure what command you need to execute,at the prompt,type eitherhelp or?.The Cisco device then displays a list of commands that