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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.

Box _unit8.1.1 The command line and the operating system

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Example _unit8.1.1 Activity 1 Think about

5 minutes

ITQ _unit8.1.1

  • 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.

ITQ _unit8.1.2

  • 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.