Step By Step - Installation, Configuration & Usage Guide of GNS3

Posted by Ahsan Tasneem | 2:15 AM | , , , , , | 0 comments »

Installation of GNS3








  1. File download
  2. The file is downloaded from http://www.gns3.net/
    Because all necessary things are packaged, this is recommended for Windows in "win32-all-in-one.exe".



    GNS3 download
  3. Installation
    Next is pushed.
    GNS3 installation screen 1

    I Agree is pushed.
    GNS3 installation screen 2

    Next is pushed as it is.
    GNS3 installation screen 3

    When WinPCAP is installed, the check is removed.
    When Dynamips is installed, the check is removed.
    Next is pushed.
    GNS3 installation screen 4

    The installation folder is selected, and Next is pushed.
    GNS3 installation screen 5

    The installation of WinPcap starts. Next is pushed as it is.
    GNS3 installation screen 6

    Next is pushed.
    GNS3 installation screen 7

    I Agree is pushed.
    GNS3 installation screen 8

    This screen goes out only when the previous version of WinPcap is installed.
    The previous version is uninstalled by Yes.
    GNS3 installation screen 9

    Finish is pushed.
    GNS3 installation screen 10

    Finish is pushed.
    GNS3 installation screen 11
  4. When the installation is completed, the following icons are made for desktop.
The installation of GNS3 is completed above.





Setup of GNS3








  1. GNS3 of desktop is double-clicked, and GNS3 is started.
  2. When "GNS3" is started, such a screen is displayed.
    Dynamips is set in [1], and the setting related to the IOS image is done by [2].
    First of all, [1] is pushed.
    GNS3 setup wizard
  3. [1] is pushed, and the place of the telnet client is specified for the terminal command column again. When Tera Term is used, it is input, "Installation directory > \ttermpro.exe %h %p of < Tera Term", and pushes the application button.
    The directory that preserves the configuration file is specified for the project directory column.
    The directory that preserves IOS is specified for the IOS/PIX directory column.
    A left Dynamips menu is pushed.
    GNS3 setting screen 2
  4. The test button is pushed as it is for WindowsXP/Vista.
    After "C:\Program Files\GNS3\Dynamips\dynamips-w2000.exe" is selected by the program passing, the test button is pushed for Windows2000.
    It is confirmed to be displayed as Dynamips successfully started, and pushes the OK button. (The change of capture and the Pemu menu is unnecessary. )
    GNS3 setting screen 3
  5. Next, [2] is pushed.
    GNS3 setup wizard
  6. The place of the IOS image is input to the image file column, and what suitable for the IOS image in the platform and the model column is selected.
    It is confirmed to push the preservation button, and to have been added to the IOS image column when the input is completed, and pushes the shutting button.
    GNS3 setting screen 4
  7. The OK button is pushed.
    GNS3 setup wizard
The setting of GNS3 is completed above.


Setting of  IdlePC

When you arrange a router and just start, a CPU sticks to 100%, and movement becomes very slow. Therefore setting of idlepc is necessary to lower a CPU rate of use. Setting comes to be easily possible in GNS3. (As for the case to be good as 100%, this setting is unnecessary)









  1. Only one router is arranged, and the router is started by right-clicking > "Start".
    The icon of 【 outline of the topology 】 is virescent when succeeding in the start.
    Start of router
  2. It right-clicks in the router, and "Idle PC" is selected.
    Selection of idlepc
  3. The value is selected and the OK button is pushed. The value is chosen referring to the following because there are two or more choices usually.








    • When there are two or more candidates, it gives priority to the one with * sign and it selects it.
    • *Either is selected when there are two or more signs.
    • *Either is selected when there is no sign.
    CPU utilization rapidly falls momentarily of the choice if it is good each other.
    When CPU utilization doesn't fall by the selected value, Idle PC is executed again and the same work is done.
    Selection of idlepc
  4. The value set here is reflected in the 【IDLE PC】 column in "IOS image and [haipa-baiza]" window.
    When Cisco3745 etc. are used, it is necessary to do a similar operation because it is necessary to do this operation at each IOS image.
    Reflection of idlepc
The setting of idlepc ends above.



Operation Method of GNS3

It explains a basic manner of operation until make - starting of the network block diagram by GNS3.
Here, it explains the procedure to make a simple network that exists in the figure below.

(1) Making of connection diagram








  1. Drug&drop does the router from a left node.
  2. A set screen opens by double-clicking the router, and the setting of the memory and the installed module is changed.
  3. The link is added. The line is selected with the button, and the line is drawn from the other router to the other router.
    The line can be deleted when right-clicking on the line.
  4. Discontinuance that adds linkIt comes off the wiring mode when the button is pushed.Main screen of GNS3

(2) Start








  1. IOS is loaded. It clicks on a button. If * in the line between routers greened, it started.
  2. It right-clicks in the router, and the console is selected.Screen after IOS of GNS3 is loaded
  3. The telnet client set by paragraph 4 of the setup starts.
    Tera Term start screen
  4. Config is poured according to the same procedure as the setting of a usual router as the config file is put.
    (Of course, the config preservation with write memory can be done. )

The explanation of the manner of operation of GNS3 ends above.




Note: I'll be posting more on this keep following me @ahsantasneem

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