GNS3: Add Qemu Host (MicroCore)

This write-up will explain Qemu Image use in GNS3 . Qemu Host image can be either CLI ( Microcore ) or GUI (Tinycore).Its basically a small linux image which can be used for performing some basic connectivity tasks e.g telnet, ssh, iptables, route, tcpdump and IPv6 support.

This tutorial will walk you through step by step for setting up Qemu Host image in GNS3

MicroCore Setup Instructions:

1.Set Qemu Host in GNS3 Preferences.

Edit -> Preferences -> Qemu -> Qemu Host

Set Qemu Host in GNS3 Preferences.

2.Setup Network Topology

Setup Network Topology

3. Start & Configure R1 for Basic Connectivity (IP address etc.)

Start & Configure R1 for Basic Connectivity

4. Start & Configure Qemu Host for Basic Connectivity (IP address etc.)

Start & Configure Qemu Host for Basic Connectivity

5. Test Connectivity between R1 & Qemu1

Test Connectivity between R1 & Qemu1

6. Enable R1 for telnet & ssh connections:

Enable R1 for telnet & ssh connections

7. Remotely manage Router from Qemu Host :

Remotely manage Router from Qemu Host

8. Add Default Route / Gateway to  Qemu Host :

Add Default Route / Gateway to  Qemu Hos

9. Use Qemu Host built-in tools e.g tcpdump & iptables for advanced testing:


Use Qemu Host built-in tools e.g tcpdump & iptables for advanced testing


10. Finally , save all your configs  :

Save Qemu Configs

In order to make your configuration changes persistent so that they get automatically loaded upon reboot, use following commands:

vi /opt/

Add your configuration line by line & save the file (:wq!)

hostname Qemu1
ifconfig eth0 netmask up
route add default gw
iptables -A INPUT -p tcp –dport telnet -j ACCEPT
iptables -A INPUT -j DROP

/usr/bin/ backup

That’s all !

Software Version Used:

  • GNS3 Version : v 0.7.3
  • Microcore Version : 2.11.5
  • Tinycore Version : 2.11.5
  • IOS Image : c3745-adventerprisek9-mz.124-15.T13.bin

->For help using IPtables , refer to this guide

->Download Qemu Microcore / Tinycore Linux binary images from the following link:

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13 Responses to “GNS3: Add Qemu Host (MicroCore)”

  1. Farhad says:

    Great Tutorial . It would have been superb if we had video tutorial as well. Thanks

  2. [...] you are a CLI junkie/lover like me , you should use Qemu Host (Microcore) & follow my previous tutorial. However, If you want to ease-up the setup & configuration using Graphical User Interface [...]

  3. moha33 says:

    great info

    iam using windows 7 64 bit followed all step. but when i tryed to assigne ip address to host it giving this errer message
    (command not foud)
    please help

  4. Kronicklez says:


    I try to save config in Qemu using your method but it not success. After i power off the Qemu host then start back it not load the previous config. Please help me..

  5. KishoreKannan says:

    Can u post some tutorials on how to run qemu host (Microcore, TInycore) under Linux GNS3

    Thanks in Advance

  6. Ramona says:

    Does the image work for Windows? I tried setting it up and it gives me error 202. What should I do?

  7. Kh. Rashedul Arefin says:

    I followed your procedure for qemu configuration. The configuration file is not saved in reboot. Its not getting any IP address. After typing the command “/usr/bin/ backup”, I get the error “Invalid device backup”. Can anyone help me?
    I am using windows xp, GNS3 0.7.3, linux-microcore-3.4.

  8. LHS says:

    >Kh. Rashedul Arefin

    /usr/bin/ -b
    hope that it can help!

  9. Okello Thomas says:

    Floor,am a new entrant in gns3 world,could you please kindly give me all the steps on how to install gns3 v 0.7.4 on windows xp platform from scratch,majorly,I get problems in defining its root in drive c but all in all,show me how to do it from ground zero.
    Kind regards.

  10. Bel says:

    Good tuto, it helps a lot !!!!

    Many thanks

  11. Gary says:

    Can you have multiple QEMU hosts?

  12. Tony says:

    lovely, i got the qemu image but it doesnt work on window vista. can anyone help me how to go about it on window vista. Thanks.t

  13. Ryan says:

    Thanks for this, helped a lot.

    Just wondering 2 things
    1. How do you reopen a Qemu window if you close it without restarting the instance?

    2. Sometimes when trying to go back to reconfigure a router, all I get is a blank putty window with a loopback address. Probably coz I didn’t exit properly, but seems I’m locked out permanently after that. Anyway around that?

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