Connecting GNS3 to Real Networks

One of the interesting things about GNS3 is that you can connect your topology to the real world. For some of your CCNA and CCNP studies you may need to run an actual Web browser or Cisco’s Security Device Manager (SDM) among others. Just connect your topology to your real PC. You could even connect to virtual machines running on your computer inside VMware or Virtual PC. I’ve even set up two copies of Windows XP Professional running inside VMware virtual machines. Then, I ran Cisco soft IP Phones that could talk to each other. You could connect your virtual network to a real network as well. Connecting a virtual topology running within GNS3 to real devices is very exciting, but again, your throughput is going to be limited compared to using real equipment for the entire topology. It only makes sense to use GNS3 in a lab environment and for learning purposes.

Drag a Cloud into your workspace. Right-click the Cloud and choose Configure. Click on C1 under Clouds, but choose the NIO Ethernet tab. Administrator rights are required (root account under Linux).

For Windows users, click on the box directly beneath Generic Ethernet NIO, and choose the network adapter you wish to use. For Linux users, click on the drop-down box to choose your network adapter (either your real adapter or a loopback adapter). Click the Add button and OK. You will need to configure the IP settings for your computer’s adapter, and then use the Add a link toolbar button to create your connection.

You may use your regular network adapter, but I usually create an MS Loopback adapter to connect to. In Windows, use the Add Hardware wizard in Control Panel. Choose “Yes, I have already connected the hardware.” On the next screen, choose Add a new hardware device at the end of the list and click Next. Choose to “Install the hardware manually…” and click Next. Choose Network Adapters in the list and click Next. Choose Microsoft as the manufacturer and then Microsoft Loopback Adapter as the network adapter. Finish the wizard. Then right-click My Network Places and choose Properties. You may wish to rename the new Local Area Connection as MS Loopback Adapter. Also, assign the proper IP settings to the adapter in order to connect to your topology. Linux has a built-in loopback adapter already installed.

Now start your router and assign an IP address to the interface that is connected to the Cloud. You should be able to ping from the router to your PC (loopback interface) and the other way around. Don’t forget to deactivate any firewall that could block pings on your computer.

What next?

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4 comments to Quick Start Guide for Linux Users

  • Fernando López


    I would like to ackowledge your work. GNS3 it’s simply fantastic. However i have some trouble in gns3 over Linux debian 3.2.0-4-686-pae #1 SMP Debian 3.2.46-1 i686 GNU/Linux.

    I have installed gns3 through apt’s tools as usual. The package is:

    Package: gns3
    Version: 0.7.4-1
    Installed-Size: 18020
    Maintainer: Erik Wenzel
    Architecture: all
    Depends: python (>= 2.6), python-support (>= 0.90.0), dynamips (>= 0.2.7-0.2.8RC1), python-qt4 (>= 4.3), ucf

    Before these installation, i had installed first qemu and some other qemu packages related, dynamips and virtualbox.

    Package: qemu
    Version: 1.1.2+dfsg-6a
    Installed-Size: 371
    Maintainer: Debian QEMU Team
    Architecture: i386
    Depends: qemu-system (>= 1.1.2+dfsg-6a), qemu-user (>= 1.1.2+dfsg-6a), qemu-utils (>= 1.1.2+dfsg-6a)
    Suggests: qemu-user-static

    Package: dynamips
    Version: 0.2.7-0.2.8RC2-5.1
    Installed-Size: 938
    Maintainer: Erik Wenzel
    Architecture: i386
    Depends: libc6 (>= 2.7), libelf1 (>= 0.131), libpcap0.8 (>= 0.9.8)

    Package: virtualbox
    Version: 4.1.18-dfsg-2+deb7u1
    Installed-Size: 45774
    Maintainer: Debian Virtualbox Team
    Architecture: i386

    All of them have been installed without problem. However I have no options for virtualbox in the window of preferences in gns3 as i can see in the pic that show this web

    So, i must to use qemu host (i have an tinycorelinux as image), and, however the testing process of qemu is passing, i can’t opening a functional terminal or serial console in gns3:
    Connected to
    Escape character is '^]'.

    After that, the console is inoperative.

    Nor installing all the software througth the gns3′s package ist giving me an operative application.

    A greeting!

    • Jeremy

      Do not use version 0.7.4, updated Debian packages for Dynamips and GNS3 are available from the download page but still considered under testing.

  • wan

    Hello …

    I use GNS3 on Slackware 13.27 machines and WinXP. Runs smoothly on both machines. based on my experience, the second method “Using a Router that Acts Like a PC” -if the router c1700 pc has the right idle-, cpu load will be lower than using qemu, which means lower resource?
    Once again thank you for this great software
    best regards

    • Jeremy


      Yes, with the router c1700 acting as a PC and the right idlepc, it is very likely the CPU/RAM will be lower than using Qemu.