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CCNA Guide to Cisco Networking Fundamentals Fourth Edition


CCNA Guide to Cisco Networking Fundamentals Fourth Edition Chapter 6 Router Startup and Configuration * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * CCNA ... – PowerPoint PPT presentation

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Title: CCNA Guide to Cisco Networking Fundamentals Fourth Edition

CCNA Guide to Cisco Networking Fundamentals
Fourth Edition
  • Chapter 6
  • Router Startup and Configuration

  • Describe the steps involved in starting a router
  • Describe and use the Cisco Discovery Protocol
  • Configure IP on the Cisco router
  • Troubleshoot router connectivity problems

Router Startup
  • In general, the boot process follows these steps
  • Test hardware (POST)
  • Load the bootstrap program
  • Locate and load the Cisco IOS
  • Locate and load the router configuration file

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Test Hardware (POST)
  • Read-only memory (ROM) in a router
  • Typically contains the power-on self-test (POST),
    the bootstrap program, and often a version of the
    operating system
  • POST is a diagnostic test that determines if the
    hardware is operating correctly
  • During the POST, the bootstrap program, also
    called the ROM Monitor, checks basic operations
    of the attached hardware
  • The ROM Monitor checks the configuration register
    for instructions regarding how to load the Cisco

Router Configuration Files
  • startup-config
  • The router configuration file that loads during
    the boot process
  • Sometimes referred to as the backup configuration
  • Because it is the saved version of the
    configuration file
  • To revert to the settings in your startup-config
  • Reboot the system by powering the router off and
    back on again or
  • Issue the reload command at the privileged EXEC
    mode prompt

Router Configuration Files (continued)
  • Note that when you copy over the startup
    configuration in NVRAM, that file is replaced
  • When you copy to the running configuration in
    RAM, the configuration files are blended
  • To view the contents of the startup-config
  • Type show startu-pconfig or just show start at
    the enable prompt
  • To see your working or running configuration
  • Type show running-config or just show run at the
    enable prompt

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Methods for Making Changes
  • You can usually implement and test changes
    without saving them to the startup configuration
  • Basic steps to implement changes
  • Make changes as desired to the configuration
  • Examine those changes
  • Determine if the changes meet the desired result
  • Remove the changes if they do not meet the
    desired result, or simply reboot the router
  • Copy the changes from the running configuration
    to the startup configuration when they do meet
    the desired result

IP on the Router
  • To manually configure IP on an interface
  • You must first change to interface configuration
  • Then, you can use the ip address command to
    configure an IP address for the specific
  • In the event you are configuring a serial
    interface as a DCE (data communication equipment)
  • You will also need to add the clockrate
    bandwidth in bits per second command

IP Connectivity
  • Telnet
  • Utility that connects at the highest layer of the
    OSI model and provides remote access to other
  • Cisco routers allow telnet connections via their
    virtual terminal ports
  • If you can establish telnet connectivity to a
  • It is available on the network and you have
    connectivity at all layers

IP Host Names
  • Sometimes, you cannot gain connectivity because
    the host name that you are trying to connect with
    is entered in a table incorrectly
  • To determine the address to name mapping on your
    router, type
  • routershow hosts
  • To add an entry to your hosts file for name
  • Go to global configuration mode and type
  • router(config)ip host router15

IP Host Names (continued)
  • To remove that entry, type
  • router(config)no ip host router15
  • To allow a name server to handle the IP address
    to name resolution, type
  • router(config)ip name-server

Ping and Trace
  • Ping and Trace verify connectivity at the
    Internetwork layer of the TCP/IP model
  • Ping can return the following replies
  • ! Successful receipt of the ICMP echo
  • . Request timed out
  • U Destination was unreachable
  • C Congestion experienced
  • I Ping interrupted
  • ? Packet type unknown
  • Packet TTL exceeded

Ping and Trace (continued)
  • Using the ping command alone
  • Referred to as extended mode ping
  • Allows you to enter your ping command step by
  • Trace sends multiple ICMP packets with
    progressively higher time-to-live counters (TTL)
  • Until the packet reaches the destination

Ping and Trace (continued)
  • The following responses can be returned by a
  • !H Indicates that a router received, but did not
    forward, the ICMP echo request
  • P Protocol unreachable
  • N Network unreachable
  • U Port unreachable
  • Request timed out

IP Route
  • If you cannot get connectivity using Ping or
    Trace, you should check your routing table
  • Issue the show ip route command from the enable
    mode prompt
  • To display the routing table
  • Typically, routing tables are dynamically created
    when routing protocols are configured on the
  • If you want, you can use the ip route command
    from the global configuration mode
  • To statically enter routes in the routing table

Checking the Interface
  • show interfaces command
  • Check the configuration of a specific interface
    from the enable mode prompt
  • Example routershow int s0/0
  • Replies
  • Serial0/0 is up, line protocol is up
  • Serial0/0 is up, line protocol is down
  • Serial0/0 is up, line protocol is
    administratively down
  • Serial0/0 is down, line protocol is down

(No Transcript)
Checking the Interface (continued)
  • Clear counters
  • The router keeps detailed statistics regarding
    data passing across its interfaces
  • To clear the counters for interface f0/0, type
  • routerclear interface f0/0
  • debug command
  • One of the most powerful tools you can use to
    obtain information from your router
  • Tool is only available from privileged EXEC mode
  • Debug has numerous subcommands

(No Transcript)
  • Cisco Discovery Protocol (CDP)
  • Cisco proprietary Data Link layer protocol
  • Shares configuration information between Cisco
    devices that are connected directly to each other
  • All Cisco devices can use CDP to
  • Discover each other
  • Learn about the configurations of other devices
  • Using CDP can help you quickly determine the
    network topology
  • CDP was designed to be a low-overhead protocol

CDP (continued)
Cisco IOS
  • Cisco IOS is usually loaded from flash memory
  • If the router cannot find the IOS in flash
    memory, it will look for a copy on a TFTP server
  • If it cannot find one there, it will boot a
    minimal version of the IOS from ROM
  • If you want to see information about your
    routers flash memory
  • Type show flash from the enable mode prompt

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Cisco IOS (continued)
Configuration Register
  • Every Cisco router has a 16-bit configuration
    register, which is stored in NVRAM
  • This register allows you to control several boot
  • Forcing the system into the bootstrap program
  • Enabling or disabling the console Break function
  • Setting the console terminal baud rate
  • Loading the IOS from ROM
  • Loading the IOS from a TFTP server
  • Examine the configuration register by typing show

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Configuration Register (continued)
ROM Monitor Mode
  • ROM Monitor mode
  • The bootstrap program that is built into the
    firmware of the router
  • Used to initialize the hardware and load the IOS
  • ROM Monitor can be used to perform other tasks
    such as diagnostics and recovering passwords
  • Configure your system to enter ROM Monitor mode
  • Enter the following command at the global
    configuration prompt
  • router(config)config-register 0x2100

ROM Monitor Mode (continued)
  • Configure your system to boot a smaller IOS image
    from ROM and enter RxBoot mode
  • Enter the following command at the global
    configuration prompt
  • router(config)config-register 0x2101

RxBoot Mode
  • RxBoot mode
  • A limited version of the IOS
  • Entering RxBoot mode is often done intentionally
  • When you want to access a TFTP server to download
    a new IOS
  • If your router enters RxBoot mode without your
  • Indicates that the router could not find a good
    IOS image
  • Prompt router(boot)

Boot System Commands
  • As long as the configuration register is
    configured with a 2 as the final hexadecimal
  • The ROM Monitor will look for boot system
    commands in NVRAM during the bootup process
  • Enable your system to boot an IOS file from the
    TFTP server
  • Issue the following command from global
    configuration mode
  • router(config)boot system tftp somefile.bin

Backing Up and Restoring the IOS
  • copy flash tftp
  • The command for backing up your IOS to a TFTP
  • You will be asked for the source filename, the IP
    address of the TFTP server, and the destination
  • Type erase flash at the privileged EXEC mode
  • To erase the IOS

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Upgrading the IOS
  • Before you load a new IOS file to your router
  • Use the show flash command to ensure there is
    enough free memory to hold it
  • The system will tell you how much memory is used
    and how much is free
  • If there is not enough memory to hold both the
    current IOS image and the upgrade
  • You will have to erase the existing flash memory
    as previously mentioned

Router Password Recovery
  • Password recovery
  • Process that allows you to get into the router
    without the necessary passwords
  • You must be physically connected to the router
    using the console cable
  • Steps to perform password recovery on the Cisco
    2600 series
  • Connect to the router from a PC using the console
    port and the HyperTerminal program
  • Enter the show version command and record the
    value of the configuration register

Router Password Recovery (continued)
  • Steps to perform password recovery on the Cisco
    2600 series (continued)
  • Turn the router off and on using the power switch
  • Press CtrlBreak several times within the first
    60 seconds of bootup
  • At the rommon 1gt prompt, type confreg 0x2142 and
    press Enter
  • Enter the reset command at the rommon 2gt prompt
  • Enter no if asked to enter the system
    configuration dialog
  • Enter enable to get to privileged mode

Router 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 into RAM
  • Enter the show run command to view the
  • To change the enable secret command, enter the
    following commands
  • Routerconfig t
  • Router(config)enable secret secret password

Router Password Recovery (continued)
  • Steps to perform password recovery on the Cisco
    2600 series (continued)
  • Enter config-register 0x2102 at the global
    configuration mode prompt to make sure the router
    reboots in the default manner
  • Enter the copy run start command to save your

Security Device Manager
  • Security Device Manager (SDM)
  • A Web-based tool primarily used for implementing
    and testing security configurations
  • Commonly used to configure routing protocols, WAN
    services, wireless routing, firewalls, virtual
    private networks (VPNs), and quality of service
  • SDM is typically not used to configure basic
    functionality on a Cisco router
  • In fact, SDM cannot do all things

(No Transcript)
  • When a router boots, it follows a set routine
  • Although a routers boot process can vary, the
    typical boot process follows a standard sequence
  • If the Cisco IOS is set to load from a TFTP
    server, but the TFTP server cannot be located,
    then the IOS will boot from flash memory
  • If the IOS cannot be found in flash memory or on
    the TFTP server, then a limited version will boot
    from ROM

Summary (continued)
  • If the Cisco IOS is set to load a configuration
    file from a TFTP server, but the file or server
    is not available, the configuration file will be
    loaded from NVRAM
  • The Cisco Discovery Protocol (CDP) shares
    information between Cisco devices about other
    local Cisco devices
  • CDP uses broadcasts to update neighbors every 60
    seconds by default
  • Devices share information about their interface
    configurations and connections to other devices

Summary (continued)
  • You can verify router connectivity to other
    systems by using telnet to determine if there is
    Application layer connectivity
  • If you cannot get connectivity at the Application
    layer, try Trace and Ping
  • One of the most important troubleshooting
    commands is the show interfaces command
  • Ciscos Security Device Manager (SDM) is a
    Web-based tool designed to help you configure
    Cisco routers