shorewall_code/docs/KVM.xml

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  <articleinfo>
    <title>KVM (Kernel-mode Virtual Machine)</title>

    <authorgroup>
      <author>
        <firstname>Tom</firstname>

        <surname>Eastep</surname>
      </author>
    </authorgroup>

    <pubdate><?dbtimestamp format="Y/m/d"?></pubdate>

    <copyright>
      <year>2008</year>

      <holder>Thomas M. Eastep</holder>
    </copyright>

    <legalnotice>
      <para>Permission is granted to copy, distribute and/or modify this
      document under the terms of the GNU Free Documentation License, Version
      1.2 or any later version published by the Free Software Foundation; with
      no Invariant Sections, with no Front-Cover, and with no Back-Cover
      Texts. A copy of the license is included in the section entitled
      <quote><ulink url="GnuCopyright.htm">GNU Free Documentation
      License</ulink></quote>.</para>
    </legalnotice>
  </articleinfo>

  <section>
    <title>Introduction</title>

    <para>Kernel-mode Virtual Machines (<ulink
    url="http://kvm.qumranet.com/">http://kvm.qumranet.com/</ulink>) is a
    virtualization platform that leverages the virtualization capabilities
    available with current microprocessors from both
    <trademark>Intel</trademark> and <trademark>AMD</trademark>. For an
    overview of KVM, please see my <ulink
    url="http://www.shorewall.net/Linuxfest-2008.pdf">2008 Linuxfest Northwest
    presentation</ulink>.</para>

    <para>I use KVM to implement a number of virtual machines running various
    Linux Distributions. The following diagram shows the entire
    network.</para>

    <graphic align="center" fileref="images/Network2008.png" />

    <para>My personal laptop (Ursa) hosts the virtual machines. As shown in
    the diagram, Ursa has routes to the internet through both the
    <trademark>Linksys</trademark> WRT300N and through my Shorewall firewall.
    This allows me to test the <ulink url="MultiISP.html">Shorewall Multi-ISP
    feature</ulink>, even though I only have a single internet
    connection</para>

    <para>The Linux Bridges shown in the diagram are, of course, actually
    within their associated system (Firewall or Ursa) but I've pictured them
    separately.</para>
  </section>

  <section>
    <title>Networking Configuration</title>

    <para>I use a network configuration where each VM has it's own VNET and
    tap device and the tap devices are all configured as ports on a Linux
    Bridge. For clarity, I've only shown four of the virtual machines
    available on the system.</para>

    <graphic align="center" fileref="images/KVM1.png" />

    <para>I run a DHCP server on the host to assign IP addresses to the VMs
    and I also run dmsmasq to act as a nameserver for the VMs. The latter is
    important when I take the laptop on the road. I'm currently running a
    separate ISC DHCP server but I have it on my todo list to configure
    dnsmasq as a DHCP server, thus eliminating one process on the
    system.</para>

    <para>The bridge is configured using the script described in my Linuxfest
    presentation linked above. The script may be found at <ulink
    url="http://www.shorewall.net/pub/shorewall/contrib/kvm/kvm">http://www.shorewall.net/pub/shorewall/contrib/kvm/kvm</ulink>.</para>

    <para>With this configuration, and with only a single network interface on
    the laptop, this is just a simple <ulink
    url="two-interface.xml">two-interface masquerading setup</ulink> where the
    local network interface is <filename class="devicefile">br0</filename>. As
    with all bridges, <filename class="devicefile">br0</filename> must be
    configured with the <option>routeback</option> option in <ulink
    url="manpages/shorewall-interfaces.html">shorewall-interfaces</ulink>(5).</para>
  </section>
</article>