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Configuring a router

The command line of a Cisco IOS router: the modes and their prompts, configuring an interface, writing a route, running and startup configuration, and reading show commands.

  • 28 cards
  • 4 topics
  • Free
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The outline, topic by topic

Each topic is weighted the way the exam weighs it.

  1. Concepts
  2. Questions
  3. Sort and link
  4. The steps

A few cards from the deck

  • Router: what is it?

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    A device that links several IP networks and passes each packet from one to the other according to its routing table.

    Each interface of a router belongs to a different network and carries an address of that network: without an address and without being enabled, it forwards nothing.

  • Which mode are you in when the prompt is Router(config-if)#?

    • Interface configuration
    • Global configuration of the router
    • Privileged mode
    • User mode, with no configuration rights
    Show the answer

    Interface configuration

    (config-if) shows that you are configuring one specific interface, chosen with interface g0/0 from Router(config)#. Commands like ip address can only be typed here.

  • To go from Router# to Router(config)#, you type …; to return straight to Router# from any sub-mode, you type ….

    Show the answer

    To go from Router# to Router(config)#, you type configure terminal; to return straight to Router# from any sub-mode, you type end.

    exit only goes up one level, while end (or Ctrl+Z) leaves all configuration sub-modes at once.

  • Cisco IOS: what is it?

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    The operating system, and its command line, of the routers and switches made by Cisco; its syntax is the reference in networking courses.

    You enter it through a console or SSH session, and the prompt tells you at every moment which mode you are in, hence which commands are allowed.

  • Giving g0/0 an address and saving: which step comes after "Router> enable"?

    • Router(config)# interface g0/0
    • Router(config-if)# ip address 192.168.1.1 255.255.255.0
    • Router(config-if)# no shutdown
    • Router# configure terminal
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    Router# configure terminal

    Each line can only be typed in the mode reached by the previous one. Without no shutdown the interface stays off, and without the final copy nothing survives a restart.

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