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Commands for CCNA students

Discussion in 'Unix' started by swap.126, Jun 17, 2008.

  1. swap.126

    swap.126 New Member

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    This chapter provides information and commands concerning the following topics:
    • Configuring a router, specifically:
    — Names
    — Passwords
    — Interfaces
    — MOTD banners
    — IP host tables
    — Saving and erasing your configurations
    • show commands to verify the router configurations
    Router Modes
    TIP: There are other modes than these. Not all commands work in all
    modes. Be careful. If you type in a command that you know is correct—show
    run, for example—and you get an error, make sure that you are in the correct
    mode.
    Router> User mode
    Router# Privileged mode
    Router(config)# Global configuration mode
    Router(config-if)# Interface mode
    Router(config-subif)# Subinterface mode
    Router(config-line)# Line mode
    Router(config-router)# Router configuration mode
    18 Configuring Passwords
    Global Configuration Mode
    Configuring a Router Name
    This command works on both routers and switches.
    Configuring Passwords
    Works on both routers and switches.
    Router> Can see config, but not change
    Router# Can see config and move to make
    changes
    Router#config t
    Router(config)#
    Moves to global config mode
    This prompt indicates that you can
    start making changes
    Router(config)#hostname Cisco Name can be any word you choose
    Cisco(config)#
    Router(config)#enable password cisco Sets enable password
    Router(config)#enable secret class Sets enable secret password
    Router(config)#line con 0 Enters console-line mode
    Router(config-line)#password console Sets console-line mode password to
    console
    Router(config-line)#login Enables password checking at login
    Router(config)#line vty 0 4 Enters vty line mode for all 5 vty
    lines
    Router(config-line)#password telnet Sets vty password to telnet
    Router(config-line)#login Enables password checking at login
    show Commands 19
    CAUTION: Enable secret password is encrypted by default. Enable password is
    not. For this reason, recommended practice is that you never use the enable
    password. Use only the enable secret password in a router configuration.
    CAUTION: You cannot set both enable secret and enable password to the same
    password. Doing so defeats the use of encryption.
    Password Encryption
    CAUTION: If you have turned on service password encryption, used it, and then
    turned it off, any passwords that you have encrypted will stay encrypted. New
    passwords will remain unencrypted
    show Commands
    Router(config)#line aux 0 Enters auxiliary line mode
    Router(config-line)#password backdoor Sets auxiliary line mode password to
    backdoor
    Router(config-line)#login Enables password checking at login
    Router(config)#service passwordencryption
    Applies a weak encryption to
    passwords
    Router(config)#enable password cisco Sets enable password to cisco
    Router(config)#line con 0 …
    Router(config-line)#password Cisco Continue setting passwords as above

    Router(config)#no service passwordencryption
    Turns off password encryption
    Router#show ? Lists all show commands available
    Router#show interfaces Displays statistics for all interfaces
    Router#show interface serial 0 Displays statistics for a specific
    interface, in this case Serial 0
    Router#show ip interface brief Displays a summary of all
    interfaces, including status and IP
    address assigned
    20 Interface Names
    Interface Names
    One of the biggest problems that new administrators face is the names of the interfaces on
    the different models of routers. The following chart lists the names of the Ethernet, Fast
    Ethernet, and Serial interfaces on the 2500, 1700, and 2600 series of routers.
    Router#show controllers serial 0 Displays statistics for interface
    hardware. Statistics display if the
    clock rate is set and if the cable is
    DCE, DTE, or not attached
    Router#show clock Displays time set on device
    Router#show hosts Displays local host-to-IP address
    cache. These are the names and
    addresses of hosts on the network to
    which you can connect
    Router#show users Displays all users connected to
    device
    Router#show history Displays history of commands used
    Router#show flash Displays info about Flash memory
    Router#show version Displays info about loaded
    software version
    Router#show arp Displays the ARP table
    Router#show protocols Displays status of configured Layer
    3 protocols
    Router#show startup-config Displays configuration saved in
    NVRAM
    Router#show running-config Displays configuration currently
    running in RAM
    Fixed Interfaces (2500
    Series)
    Modular (Removable)
    Interfaces (1700 Series)
    Modular (Removable)
    Interfaces (2600 Series)
    Router(config)#int
    erface type port
    Router(config)#interf
    ace type port
    Router(config)#interface
    type slot/port
    Router(config)#int
    serial0 (s0)
    Router(config)#interf
    ace serial 0
    Router(config)#int serial
    0/0 (s0/0)
    Router(config)#int
    ethernet 0 (e0)
    Router(config)#interf
    ace fastethernet 0
    Router(config)#int
    fastethernet 0/0 (fa0/0)
    Configuring an Ethernet/Fast Ethernet Interface 21
    Moving Between Interfaces
    What happens in Column 1 is the same thing as is occurring in Column 2.
    Configuring a Serial Interface
    TIP: The clock rate command is used only on a serial interface that has a DCE
    cable plugged into it. There must be a clock rate set on every serial link between
    routers. It does not matter which router has the DCE cable plugged into it, or which
    interface the cable is plugged into. Serial 0 on one router can be plugged into
    Serial 1 on another router.
    Configuring an Ethernet/Fast Ethernet Interface
    Router(config)#int s0 Router(config)#int s0 Moves to interface S0
    mode
    Router(config-if)#exit Router(config-if)#int e0 In int S0, move to E0
    Router(config)#int e0 Router(config-if)# In E0 mode now
    Router(config-if)# Prompt does not
    change; be careful
    Router(config)#int s0/0 Moves to interface Serial 0/0
    mode
    Router(config-if)#description Link to ISP Optional descriptor of the link is
    locally significant
    Router(config-if)#ip address 192.168.10.1
    255.255.255.0
    Assigns address and subnet
    mask to interface
    Router(config-if)#clock rate 56000 Assigns a clock rate for the
    interface
    Router(config-if)#no shut Turns interface on
    Router(config)#int fa0/0 Moves to Fast Ethernet 0/0
    interface mode
    Router(config-if)#description Accounting LAN Optional descriptor of the
    link is locally significant
    22 Assigning a Local Host Name to an IP Address
    Creating a MOTD Banner
    Setting the Clock Time Zone
    Assigning a Local Host Name to an IP Address
    TIP: The default port number in the ip host command is 23, or Telnet. If you want
    to Telnet to a device, just enter the IP host name itself:
    Router#london = Router#telnet london = Router#telnet 172.16.1.3
    Router(config-if)#ip address 192.168.20.1
    255.255.255.0
    Assigns address and subnet
    mask to interface
    Router(config-if)#no shut Turns interface on
    Router(config)#banner motd # This is a
    secure system. Authorized Personnel Only! #
    Router(config)#
    # is known as a delimiting
    character. The delimiting
    character must surround the
    banner message and can be
    any character so long as it is
    not a character used within
    the body of the message
    Router(config)#clock timezone EST –5 Sets the time zone for
    display purposes. Based on
    coordinated universal time
    (Eastern Standard Time is 5
    hours behind UTC)
    Router(config)#ip host london 172.16.1.3 Assigns a host name to the
    IP address. After this
    assignment, you can use the
    host name instead of an IP
    address when trying to
    Telnet or ping to that
    address
    Router#ping london
    =
    Router#ping 172.16.1.3
    exec-timeout Command 23
    no ip domain-lookup Command
    TIP: Ever type in a command incorrectly and left having to wait for a minute or
    two as the router tries to translate your command to a domain server of
    255.255.255.255? The router is set by default to try to resolve any word that is not
    a command to a DNS server at address 255.255.255.255. If you are not going to set
    up DNS, turn this feature off to save you time as you type, especially if you are a
    poor typist.
    logging synchronous Command
    TIP: Ever try to type in a command and an informational line appears in the
    middle of what you were typing? Lose your place? Do not know where you are in
    the command, so you just press ® and start all over? The logging
    synchronous command will tell the router that if any informational items get
    displayed on the screen, your prompt and command line should be moved to a
    new line, so as not to confuse you.
    The informational line does not get inserted into the middle of the command you
    are trying to type. If you were to continue typing, the command would execute
    properly, even though it looks wrong on the screen
    exec-timeout Command
    Router(config)#no ip domain-lookup
    Router(config)#
    Turns off trying to
    automatically resolve an
    unrecognized command to a
    local host name
    Router(config)#line con 0
    Router(config-line)#logging synchronous Turns on synchronous
    logging. Information items
    sent to console will not
    interrupt the command you
    are typing. The command
    will be moved to a new line
    Router(config)#line con 0
    Router(config-line)#exec-timeout 0 0 Sets time limit when console
    automatically logs off. Set to
    0 0 (minutes seconds) means
    console never logs off
    Router(config-line)#
    24 Configuration Example: Basic Router Configuration
    TIP: exec-timeout 0 0 is great for a lab because the console never logs out. This
    is very dangerous in the real world (bad security).
    Saving Configurations
    Erasing Configurations
    TIP: Running-config is still in dynamic memory. Reload the router to clear the
    running-config.
    Configuration Example: Basic Router Configuration
    Figure 3-1 shows the network topology for the configuration that follows, which shows a
    basic router configuration using the commands covered in this chapter.
    Figure 3-1 Network Topology for Basic Router Configuration
    Router#copy run start Saves the running-config to local NVRAM
    Router#copy run tftp Saves the running-config remotely to TFTP server
    Router#erase start Deletes the startup-config file from NVRAM
    Boston Router
    Router>en Enters privileged mode
    Router#clock set 18:30:00 15 Nov 2004 Sets local time on router
    Router#config t Enters global config mode
    Boston
    Network 172.16.10.0/24 Network 172.16.20.0/24 Network 172.16.30.0/24
    fa0/0 fa0/0
    172.16.20.1
    172.16.10.10 s0/0
    172.16.10.1 172.16.30.1
    172.16.30.30
    DCE
    s0/1
    172.16.20.2 Buffalo
    Configuration Example: Basic Router Configuration 25
    Router(config)#hostname Boston Sets router name to Boston
    Boston(config)#no ip domain-lookup Turns off name resolution on
    unrecog-nized commands
    (spelling mistakes)
    Boston(config)#banner motd #
    This is the Boston Router.
    Authorized Access Only
    #
    Creates an MOTD banner
    Boston(config)#clock timezone EST –5 Sets time zone to Eastern
    Standard Time (–5 from UTC)
    Boston(config)#enable secret cisco Enable secret password set to
    cisco
    Boston(config)#service password-encryption Passwords will be given weak
    encryption
    Boston(config)#line con 0 Enters line console mode
    Boston(config-line)#logging sync Commands will not be
    interrupted by unsolicited
    messages
    Boston(config-line)#password class Sets password to class
    Boston(config-line)#login Enables password checking at
    login
    Boston(config-line)#line vty 0 4 Moves to virtual Telnet lines 0
    through 4
    Boston(config-line)#password class Sets password to class
    Boston(config-line)#login Enables password checking at
    login
    Boston(config-line)#line aux 0 Moves to line auxiliary mode
    Boston(config-line)#password class Sets password to class
    Boston(config-line)#login Enables password checking at
    login
    Boston(config-line)#exit Moves back to global config
    mode
    26 Configuration Example: Basic Router Configuration
    Boston(config)#no service passwordencryption
    Turns off password encryption
    Boston(config)#int fa 0/0 Moves to Fast Ethernet 0/0
    mode
    Boston(config-if)#desc Engineering LAN Sets locally significant
    description of the interface
    Boston(config-if)#ip address 172.16.10.1
    255.255.255.0
    Assigns IP address and subnet
    mask to the interface
    Boston(config-if)#no shut Turns on the interface
    Boston(config-if)#int s0/0 Moves directly to Serial 0/0
    mode
    Boston(config-if)#desc Link to Buffalo
    Router
    Sets locally significant
    description of the interface
    Boston(config-if)#ip address 172.16.20.1
    255.255.255.0
    Assigns IP address and subnet
    mask to the interface
    Boston(config-if)#clock rate 56000 Sets a clock rate for serial
    transmission (DCE cable must
    be plugged into this interface)
    Boston(config-if)#no shut Turns on the interface
    Boston(config-if)#exit Moves back to global config
    mode
    Boston(config)#ip host buffalo 172.16.20.2 Sets a local host name
    resolution to IP address
    172.16.20.2
    Boston(config)#exit Moves back to privileged
    mode
    Boston#copy run start Saves running-config to
     
  2. shabbir

    shabbir Administrator Staff Member

    Joined:
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    I could not understand the content and so moved to the forum from the articles section
     

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