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Discovering computer networks: hands on in the Open Networking Lab
Discovering computer networks: hands on in the Open Networking Lab

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13.1 The command line and operating system

You were introduced to the Cisco CLI (command-line interface) in an earlier session, but you may have met some things there that you found a little baffling. In this part you’ll look at the CLI in greater detail and unravel some of its mysteries.

Watch the video below, which is a little over 3 minutes long. This video introduces you to the Cisco operating system and explains what happens when it is booted up.

The command line and the operating system

Download this video clip.Video player: 70_the_command_line_and_the_operating_system_edit.mp4
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Activity 1 Think about

5 minutes

  • 1. The following output shows part of a response to the command show ip interface brief. Explain what is meant by the term ‘unassigned’ in the IP address column.


    Router#show ip interface brief

    Interface IP-Address OK? Method Status Protocol

    GigabitEthernet0/0 YES manual up up

    GigabitEthernet0/1 unassigned YES unset administratively down down

    GigabitEthernet0/2 unassigned YES unset administratively down down

    Vlan1 unassigned YES unset administratively down down


  • From the output, you should have noticed that for the interface GigabitEthernet0/0 there was an IP address in the ‘IP-Address’ column. From this you should have been able to deduce that ‘unassigned’ simply means that an IP address hasn’t yet been configured on those interfaces that ‘unassigned’ appears alongside.

  • 2. Which of the following are Cisco IOS functions?

  • a. 

    Checking the router hardware


    Loading the config file


    Sending a ping to all connected devices


    Loading any default settings if there is no config file


    Enabling a config file to be created and saved


    Warning the user of any security threat.

    The correct answers are a, b, d and e.