How to Use GNS3 in Windows

Many people want to use GNS3 to prepare for network professional exams. But most of the people face issue to use GNS3. In this post, we will explain how to use GNS3. To use GNS3, you need to create a network topology in GNS3 by adding routers and switches. Before you can use a device such as a router to create a network topology in GNS3, first, you need to add the Cisco IOS image for that device. You can freely download the GNS3 IOS images for the desired platform, such as router, switch and PIX firewall. Once you have downloaded the appropriate IOS image, you can add that IOS image in GNS3. In this post. we will explain the detailed steps how to add an IOS image for Cisco router in GNS3 and how to use GNS3. We assume that you have already downloaded the GNS3 tool and the few Cisco IOS images for GNS3. If you have not yet done it, please visit the following links.

So let’s begin how to add an IOS image in GNS3 and how to use GNS3. To add an IOS image for Cisco router in GNS3, you need to perform the following steps:

  1. Open the GNS3 console, click Edit, and then select Preferences.How to Use GNS3
  2. On the Preferences window, select IOS Routers in the left pane. Click New to add a new ISO image.Router IOS Template Window
  3. The New IOS Router template dialog box will be displayed.
  4. Click Browse and select the IOS image that you want to add, and then click Next. In the following figure, we have used 2691 series IOS image.Browse IOS Image for GNS3
  5. On the Name and platform page, select the platform, (in this case, c2691), and then click Next.
    GNS3 IOS Image Name and Platform
  6. On the Memory page, assign the desired memory size, we recommend to set it at least 128 MB,  and then click Next.Set Memory for router in GNS3
  7. On the Network adapter page, you can select the slots to add the additional interfaces.Add Network Adapters in GNS3
  8. On the WIC modules page, select a WAN Interface Card (WIC), and then click Next.Adding WIC module in GNS3
  9. On the Idle-PC page, click Finish.
  10. On the Preferences window, click Apply, and then click OK.
  11. On the GNS3 console, click the router icon, drag the router in the middle pane. Add one more router in the middle pane. Click the connection icon in the left lower corner. Click on R1 and select an interface such as FastEthernt0/0. Click on R2 and select the desired interface to connect R1 to R2.Starting Routers in GNS3
  12. On the GNS3 console, right-click on each router and select Start to start both the routers.Start a router in GNS3
  13. Once the routers are started, right-click on any router and select Console to open its console.
  14. The router’s console will be displayed, as shown in the following figure.
    12
  15. Now, you can do on simulated Cisco IOS whatever you want to do on a physical Cisco router. That’s what GNS3 allows you.

In this post, we have discussed how to add Cisco IOS images in GNS3 and how to use GNS3. Hope you have enjoyed it. Let us know, if you face any issue during adding the IOS images in GNS3.

Posted in Cisco, GNS3 Tutorials Tagged with: ,
2 comments on “How to Use GNS3 in Windows
  1. MD. Sajid says:

    Excellent article and great explanation.

  2. Tarun says:

    I tried adding an c3600 following the above instruction, when I try to connect to console it gives me the following error. Please help:

    Connected to Dynamips VM “R2” (ID 4, type c3600) – Console port
    Press ENTER to get the prompt.
    ROMMON emulation microcode.

    Launching IOS image at 0x80008000…

    Error : compressed image checksum is incorrect 0x534FC290
    Expected a checksum of 0xAC10AA9F

    !!! WARNING – VM is not running, will be unresponsive (status=1) !!!

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