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© Wiley Inc. 2006. All Rights Reserved.
CHAPTER 4: Introduction to the
Cisco IOS
CCNA: Cisco Certified Network Associate Study
Guide
© Wiley Inc. 2006. All Rights Reserved.
The CCNA exam topics covered in this chapter include the following:
Implementation & Operation•Configure IP addresses, subnet masks, and gateway addresses on routers and hosts• Configure a router for additional administrative functionality•Implement a LAN •Perform an initial configuration on a router• Perform an initial configuration on a switch
© Wiley Inc. 2006. All Rights Reserved.
Cisco Router IOS
• Carries network protocols and functions
• Connects high-speed traffic between devices
• Adds security to control access• Provides scalability for growth• Supplies reliability
© Wiley Inc. 2006. All Rights Reserved.
Bringing up a Router
• Boot-up process:1: POST2: Looks for the Cisco IOS from Flash
memory3: IOS loads & looks for a valid configuration;
• startup-configstartup-config• stored in nonvolatile RAM (NVRAM)
4: If a valid config is not found in NVRAM:• setup modesetup mode
© Wiley Inc. 2006. All Rights Reserved.
Setup Mode
• Basic Management Setup
• Extended Setup
• Command-Line Interface
© Wiley Inc. 2006. All Rights Reserved.
Command-Line Interface (CLI)
• More flexible than setup mode.• To use the CLI, just say No to
entering the initial configuration dialog.
© Wiley Inc. 2006. All Rights Reserved.
Logging into the Router
• User mode: – Router>– Used mostly to view statistics
• Privileged mode:– Router#– Used to view & change router configuration
© Wiley Inc. 2006. All Rights Reserved.
Overview of Router Modes
• Global changes:– config terminal or config t– Changes made to running-config running-config (DRAM)– To change the startup-configstartup-config (NVRAM)
• config memory or config memNote: Any configuration changes need to be placed into RAM. Typing config mem or config net (from a TFTP host) will replace the current running-configrunning-config
© Wiley Inc. 2006. All Rights Reserved.
Configuration
• CLI Prompts• Interfaces• Sub-interfaces• Line Commands• Routing Protocol
Configurations
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Editing & Help Features
• Commands starting with a certain letter
Router#c?clear clock configure connect copy
• Enhanced Editing Commands• Router-Command History• Gathering Basic Routing
Information– show versionshow version
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Administrative Functions
The administrative functions that you can configure on a router and switch are
• Hostnames• Banners• Password• Interface descriptions
© Wiley Inc. 2006. All Rights Reserved.
Hostnames & Descriptions
• HostnamesRouter(config)#hostname toddtodd(config)#
• DescriptionsAtlanta(config)#int e0Atlanta(config-if)#description Sales Lan
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Banners
• Purpose• Types
– exec– incoming– login– motd
• Delimiting character
© Wiley Inc. 2006. All Rights Reserved.
Setting the Passwords
• 5 passwords:– 1st two used to set your enable password
• Used to secure privileged mode; Router>enable
– Other three are used to configure a password in useruser mode via:
• console port• auxiliary port• Telnet
© Wiley Inc. 2006. All Rights Reserved.
Passwords
• Enable passwordsRouter(config)#enable password ciscoRouter(config)#enable secret cisco
• Auxiliary Password• Console Password• Telnet Password• Encrypting Your Password
Router(config)#service password-encryption
© Wiley Inc. 2006. All Rights Reserved.
Interface DescriptionsSetting descriptions on an interface is helpful to the administrator and, like the hostname, only locally significant. The description command is a helpful one because you can, for instance, use it to keep track of circuit numbers.
Here’s an example:Atlanta(config)#int e0Atlanta(config-if)#description Sales LanAtlanta(config-if)#int s0Atlanta(config-if)#desc Wan to Miami circuit:6fdda4321
You can view the description of an interface either with the show running-config command or the show interface command.
© Wiley Inc. 2006. All Rights Reserved.
Router Interfaces• Purpose• Bringing up an Interface
no shutdownshutdownshow interface
• Configuring an IP Address on an Interface
Router(config)#int e0Router(config-if)#ip address
172.16.10.2 255.255.255.0Router(config-if)#no shut
• Serial Interface Commandsclock rate & bandwidth (entered
in kilobits)
© Wiley Inc. 2006. All Rights Reserved.
Viewing, & Saving Configurations
• Viewing & Saving Configurations– running-configrunning-config saved in DRAM– startup-configstartup-config saved in NVRAM
copy run startsh runsh starterase startup-config
© Wiley Inc. 2006. All Rights Reserved.
Verifying Your Configuration
Tools:– show running-config– show startup-config– ping– show cdp nei detail– trace– telnet
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