<html>
  <body>
    <h1>Network XML format</h1>

    <ul id="toc">
    </ul>

    <p>
      This page provides an introduction to the network XML format. For background
      information on the concepts referred to here, consult the <a href="archnetwork.html">network driver architecture</a>
      page.
    </p>

    <h2><a name="elements">Element and attribute overview</a></h2>

    <p>
      The root element required for all virtual networks is
      named <code>network</code> and has no attributes.
      The network XML format is available <span class="since">since 0.3.0</span>
    </p>

    <h3><a name="elementsMetadata">General metadata</a></h3>

    <p>
      The first elements provide basic metadata about the virtual
      network.
    </p>

    <pre>
      &lt;network&gt;
        &lt;name&gt;default&lt;/name&gt;
        &lt;uuid&gt;3e3fce45-4f53-4fa7-bb32-11f34168b82b&lt;/uuid&gt;
        ...</pre>

    <dl>
      <dt><code>name</code></dt>
      <dd>The content of the <code>name</code> element provides
        a short name for the virtual network. This name should
        consist only of alpha-numeric characters and is required
        to be unique within the scope of a single host. It is
        used to form the filename for storing the persistent
        configuration file. <span class="since">Since 0.3.0</span></dd>
      <dt><code>uuid</code></dt>
      <dd>The content of the <code>uuid</code> element provides
        a globally unique identifier for the virtual network.
        The format must be RFC 4122 compliant, eg <code>3e3fce45-4f53-4fa7-bb32-11f34168b82b</code>.
        If omitted when defining/creating a new network, a random
        UUID is generated. <span class="since">Since 0.3.0</span></dd>
    </dl>

    <h3><a name="elementsConnect">Connectivity</a></h3>

    <p>
      The next set of elements control how a virtual network is
      provided connectivity to the physical LAN (if at all).
    </p>

    <pre>
        ...
        &lt;bridge name="virbr0" stp="on" delay="5"/&gt;
        &lt;domain name="example"/&gt;
        &lt;forward mode="nat" dev="eth0"/&gt;
        ...</pre>

    <dl>
      <dt><code>bridge</code></dt>
      <dd>The <code>name</code> attribute on the <code>bridge</code> element
        defines the name of a bridge device which will be used to construct
        the virtual network. The virtual machines will be connected to this
        bridge device allowing them to talk to each other. The bridge device
        may also be connected to the LAN. It is recommended that bridge
        device names started with the prefix <code>vir</code>, but the name
        <code>virbr0</code> is reserved for the "default" virtual
        network.  This element should always be provided when defining
        a new network with a <code>&lt;forward&gt;</code> mode of
        "nat" or "route" (or an isolated network with
        no <code>&lt;forward&gt;</code> element).
        Attribute <code>stp</code> specifies if Spanning Tree Protocol
        is 'on' or 'off' (default is
        'on'). Attribute <code>delay</code> sets the bridge's forward
        delay value in seconds (default is 0).
        <span class="since">Since 0.3.0</span>
      </dd>
      <dt><code>domain</code></dt>
      <dd>
        The <code>name</code> attribute on the <code>domain</code>
        element defines the DNS domain of the DHCP server. This
        element is optional, and is only used for those networks with
        a <code>&lt;forward&gt;</code> mode of "nat" or "route" (or an
        isolated network with no <code>&lt;forward&gt;</code>
        element). <span class="since">Since 0.4.5</span>
      </dd>
      <dt><code>forward</code></dt>
      <dd>Inclusion of the <code>forward</code> element indicates that
        the virtual network is to be connected to the physical
        LAN.<span class="since">Since 0.3.0.</span>
        The <code>mode</code> attribute determines the method of
        forwarding. If there is no <code>forward</code> element, the
        network will be isolated from any other network (unless a
        guest connected to that network is acting as a router, of
        course). The following are valid settings
        for <code>mode</code> (if there is a <code>forward</code>
        element but mode is not specified, <code>mode='nat'</code> is
        assumed):
        <dl>
          <dt><code>nat</code></dt>
          <dd>
            All traffic between guests connected to this network and
            the physical network will be forwarded to the physical
            network via the host's IP routing stack, after the guest's
            IP address is translated to appear as the host machine's
            public IP address (a.k.a. Network Address Translation, or
            "NAT"). This allows multiple guests, all having access to
            the physical network, on a host that is only allowed a
            single public IP address. If a network has any IPv6
            addresses defined, the IPv6 traffic will be forwarded
            using plain routing, since IPv6 has no concept of NAT.
            Firewall rules will allow outbound connections to any
            other network device whether ethernet, wireless, dialup,
            or VPN. If the <code>dev</code> attribute is set, the
            firewall rules will restrict forwarding to the named
            device only. Inbound connections from other networks are
            all prohibited; all connections between guests on the same
            network, and to/from the host to the guests, are
            unrestricted and not NATed.<span class="since">Since
            0.4.2</span>
          </dd>

          <dt><code>route</code></dt>
          <dd>
            Guest network traffic will be forwarded to the physical
            network via the host's IP routing stack, but without
            having NAT applied. Again, if the <code>dev</code>
            attribute is set, firewall rules will restrict forwarding
            to the named device only. This presumes that the local LAN
            router has suitable routing table entries to return
            traffic to this host. Firewall rules are also installed
            that prevent incoming sessions from the physical network
            to the guests, but outgoing sessions are unrestricted (as
            are sessions from the host to the guests, and between
            guests on the same network.)<span class="since">Since
            0.4.2</span>
          </dd>

          <dt><code>bridge</code></dt>
          <dd>
            This network describes either 1) an existing host bridge
            that was configured outside of libvirt (if
            a <code>&lt;bridge name='xyz'/&gt;</code> element has been
            specified), or 2) an interface or group of interfaces to
            be used for a "direct" connection via macvtap using
            macvtap's "bridge" mode (if the forward element has one or
            more <code>&lt;interface&gt;</code> subelements)
            (see <a href="formatdomain.html#elementsNICSDirect">Direct
            attachment to physical interface</a> for descriptions of
            the various macvtap modes). libvirt doesn't attempt to
            manage the bridge interface at all, thus
            the <code>&lt;bridge&gt;</code> element's <code>stp</code>
            and <code>delay</code> attributes are not allowed; no
            iptables rules, IP addresses, or DHCP/DNS services are
            added; at the IP level, the guest interface appears to be
            directly connected to the physical
            interface.<span class="since">Since 0.9.4</span>
          </dd>
          <dt><code>private</code></dt>
          <dd>
            This network uses a macvtap "direct" connection in
            "private" mode to connect each guest to the network. The
            physical interface to be used will be picked from among
            those listed in <code>&lt;interface&gt;</code> subelements
            of the <code>&lt;forward&gt;</code> element; when using
            802.1Qbh mode (as indicated by
            the <code>&lt;virtualport&gt;</code> type attribute - note
            that this requires an 802.1Qbh-capable hardware switch),
            each physical interface can only be in use by a single
            guest interface at a time; in modes other than 802.1Qbh,
            multiple guest interfaces can share each physical
            interface (libvirt will attempt to balance usage between
            all available interfaces).<span class="since">Since
            0.9.4</span>
          </dd>
          <dt><code>vepa</code></dt>
          <dd>
            This network uses a macvtap "direct" connection in "vepa"
            mode to connect each guest to the network (this requires
            that the physical interfaces used be connected to a
            vepa-capable hardware switch. The physical interface to be
            used will be picked from among those listed
            in <code>&lt;interface&gt;</code> subelements of
            the <code>&lt;forward&gt;</code> element; multiple guest
            interfaces can share each physical interface (libvirt will
            attempt to balance usage between all available
            interfaces).<span class="since">Since 0.9.4</span>
          </dd>
          <dt><code>passthrough</code></dt>
          <dd>
            This network uses a macvtap "direct" connection in
            "passthrough" mode to connect each guest to the network
            (note that this is <i>not</i> the same thing as "PCI
            passthrough"). The physical interface to be used will be
            picked from among those listed
            in <code>&lt;interface&gt;</code> subelements of
            the <code>&lt;forward&gt;</code> element.  Each physical
            interface can only be in use by a single guest interface
            at a time, so libvirt will keep track of which interfaces
            are currently in use, and only assign unused interfaces
            (if there are no available physical interfaces when a
            domain interface is being attached, an error will be
            logged, and the operation causing the attach will fail
            (usually either a domain start, or a hotplug interface
            attach to a domain).<span class="since">Since 0.9.4</span>
          </dd>
        </dl>
        As mentioned above, a <code>&lt;forward&gt;</code> element can
        have multiple <code>&lt;interface&gt;</code> subelements, each
        one giving the name of a physical interface that can be used
        for this network<span class="since">Since 0.9.4</span>:
        <pre>
...
  &lt;forward mode='passthrough'&gt;
    &lt;interface dev='eth10'/&gt;
    &lt;interface dev='eth11'/&gt;
    &lt;interface dev='eth12'/&gt;
    &lt;interface dev='eth13'/&gt;
    &lt;interface dev='eth14'/&gt;
  &lt;/forward&gt;
...
        </pre>
        When a guest interface is being constructed, libvirt will pick
        an interface from this list to use for the connection. In
        modes where physical interfaces can be shared by multiple
        guest interfaces, libvirt will choose the interface that
        currently has the least number of connections. For those modes
        that do not allow sharing of the physical device (in
        particular, 'passthrough' mode, and 'private' mode when using
        802.1Qbh), libvirt will choose an unused physical interface
        or, if it can't find an unused interface, fail the operation.
      </dd>
    </dl>
    <h5><a name="elementQoS">Quality of service</a></h5>

<pre>
...
  &lt;forward mode='nat' dev='eth0'/&gt;
  <b>&lt;bandwidth&gt;
    &lt;inbound average='1000' peak='5000' burst='5120'/&gt;
    &lt;outbound average='128' peak='256' burst='256'/&gt;
  &lt;/bandwidth&gt;</b>
...</pre>

      <p>
        This part of network XML provides setting quality of service. Incoming
        and outgoing traffic can be shaped independently. The
        <code>bandwidth</code> element can have at most one <code>inbound</code>
        and at most one <code>outbound</code> child elements. Leaving any of these
        children element out result in no QoS applied on that traffic direction.
        So, when you want to shape only network's incoming traffic, use
        <code>inbound</code> only, and vice versa. Each of these elements have one
        mandatory attribute <code>average</code>. It specifies average bit rate on
        interface being shaped. Then there are two optional attributes:
        <code>peak</code>, which specifies maximum rate at which bridge can send
        data, and <code>burst</code>, amount of bytes that can be burst at
        <code>peak</code> speed. Accepted values for attributes are integer
        numbers, The units for <code>average</code> and <code>peak</code> attributes
        are kilobytes per second, and for the <code>burst</code> just kilobytes.
        The rate is shared equally within domains connected to the network.
        Moreover, <code>bandwidth</code> element can be included in
        <code>portgroup</code> element.
        <span class="since">Since 0.9.4</span>
      </p>

    <h5><a name="elementsPortgroup">Portgroups</a></h5>

<pre>
...
  &lt;forward mode='private'/&gt;
    &lt;interface dev="eth20"/&gt;
    &lt;interface dev="eth21"/&gt;
    &lt;interface dev="eth22"/&gt;
    &lt;interface dev="eth23"/&gt;
    &lt;interface dev="eth24"/&gt;
  &lt;/forward&gt;
  <b>&lt;portgroup name='engineering' default='yes'&gt;
    &lt;virtualport type='802.1Qbh'&gt;
      &lt;parameters profileid='test'/&gt;
    &lt;/virtualport&gt;
    &lt;bandwidth&gt;
      &lt;inbound average='1000' peak='5000' burst='5120'/&gt;
      &lt;outbound average='1000' peak='5000' burst='5120'/&gt;
    &lt;/bandwidth&gt;
  &lt;/portgroup&gt;</b>
  <b>&lt;portgroup name='sales'&gt;
    &lt;virtualport type='802.1Qbh'&gt;
      &lt;parameters profileid='salestest'/&gt;
    &lt;/virtualport&gt;
    &lt;bandwidth&gt;
      &lt;inbound average='500' peak='2000' burst='2560'/&gt;
      &lt;outbound average='128' peak='256' burst='256'/&gt;
    &lt;/bandwidth&gt;
  &lt;/portgroup&gt;</b>
...</pre>

    <p>
      A portgroup provides a method of easily putting guest
      connections to the network into different classes, with each
      class potentially having a different level/type of service. Each
      network can have multiple portgroup elements (and one of those
      can optionally be designated as the 'default' portgroup for the
      network), and each portgroup has a name, as well as various
      subelements associated with it. The currently supported
      subelements are <code>&lt;bandwidth&gt;</code>
      (documented <a href="formatdomain.html#elementQoS">here</a>)
      and <code>&lt;virtualport&gt;</code>
      (documented <a href="formatdomain.html#elementsNICSDirect">here</a>).
      If a domain interface definition specifies a portgroup (by
      adding a <code>portgroup</code> attribute to
      the <code>&lt;source&gt;</code> subelement), that portgroup's
      info will be merged into the interface's configuration. If no
      portgroup is given in the interface definition, and one of the
      network's portgroups has <code>default='yes'</code>, that
      default portgroup will be used. If no portgroup is given in the
      interface definition, and there is no default portgroup, then
      none will be used. Any <code>&lt;bandwidth&gt;</code>
      or <code>&lt;virtualport&gt;</code> specified directly in the
      domain XML will take precedence over any setting in the chosen
      portgroup.
    </p>

    <h3><a name="elementsAddress">Addressing</a></h3>

    <p>
      The final set of elements define the addresses (IPv4 and/or
      IPv6, as well as MAC) to be assigned to the bridge device
      associated with the virtual network, and optionally enable DHCP
      services. These elements are only valid for isolated networks
      (no <code>forward</code> element specified), and for those with
      a forward mode of 'route' or 'nat'.
    </p>

    <pre>
        ...
        &lt;mac address='00:16:3E:5D:C7:9E'/&gt;
        &lt;dns&gt;
          &lt;txt name="example" value="example value" /&gt;
        &lt;/dns&gt;
        &lt;ip address="192.168.122.1" netmask="255.255.255.0"&gt;
          &lt;dhcp&gt;
            &lt;range start="192.168.122.100" end="192.168.122.254" /&gt;
            &lt;host mac="00:16:3e:77:e2:ed" name="foo.example.com" ip="192.168.122.10" /&gt;
            &lt;host mac="00:16:3e:3e:a9:1a" name="bar.example.com" ip="192.168.122.11" /&gt;
          &lt;/dhcp&gt;
        &lt;/ip&gt;
        &lt;ip family="ipv6" address="2001:db8:ca2:2::1" prefix="64" /&gt;
      &lt;/network&gt;</pre>

    <dl>
      <dt><code>mac</code></dt>
      <dd>The <code>address</code> attribute defines a MAC
        (hardware) address formatted as 6 groups of 2-digit
        hexadecimal numbers, the groups separated by colons
        (eg, <code>"52:54:00:1C:DA:2F"</code>).  This MAC address is
        assigned to the bridge device when it is created.  Generally
        it is best to not specify a MAC address when creating a
        network - in this case, if a defined MAC address is needed for
        proper operation, libvirt will automatically generate a random
        MAC address and save it in the config. Allowing libvirt to
        generate the MAC address will assure that it is compatible
        with the idiosyncrasies of the platform where libvirt is
        running. <span class="since">Since 0.8.8</span>
      </dd>
      <dt><code>dns</code></dt><dd>
        The dns element of a network contains configuration information for the
        virtual network's DNS server. <span class="since">Since 0.9.3</span>
        Currently supported elements are:
        <dl>
          <dt><code>txt</code></dt>
          <dd>A <code>dns</code> element can have 0 or more <code>txt</code> elements.
            Each txt element defines a DNS TXT record and has two attributes, both
            required: a name that can be queried via dns, and a value that will be
            returned when that name is queried. names cannot contain embedded spaces
            or commas. value is a single string that can contain multiple values
            separated by commas. <span class="since">Since 0.9.3</span>
          </dd>
          <dt><code>host</code></dt>
          <dd>The <code>host</code> element within <code>dns</code> is the
            definition of DNS hosts to be passed to the DNS service. The IP
            address is identified by the <code>ip</code> attribute and the names
            for that IP address are identified in the <code>hostname</code>
            sub-elements of the <code>host</code> element.
            <span class="since">Since 0.9.3</span>
          </dd>
        </dl>
      </dd>
      <dt><code>ip</code></dt>
      <dd>The <code>address</code> attribute defines an IPv4 address in
        dotted-decimal format, or an IPv6 address in standard
        colon-separated hexadecimal format, that will be configured on
        the bridge
        device associated with the virtual network. To the guests this
        address will be their default route. For IPv4 addresses, the <code>netmask</code>
        attribute defines the significant bits of the network address,
        again specified in dotted-decimal format.  For IPv6 addresses,
        and as an alternate method for IPv4 addresses, you can specify
        the significant bits of the network address with the <code>prefix</code>
        attribute, which is an integer (for example, <code>netmask='255.255.255.0'</code>
        could also be given as <code>prefix='24'</code>. The <code>family</code>
        attribute is used to specify the type of address - 'ipv4' or 'ipv6'; if no
        <code>family</code> is given, 'ipv4' is assumed. A network can have more than
        one of each family of address defined, but only a single address can have a
        <code>dhcp</code> or <code>tftp</code> element. <span class="since">Since 0.3.0;
        IPv6, multiple addresses on a single network, <code>family</code>, and
        <code>prefix</code> since 0.8.7</span>
        <dl>
          <dt><code>tftp</code></dt>
          <dd>Immediately within
            the <code>ip</code> element there is an optional <code>tftp</code>
            element. The presence of this element and of its attribute
            <code>root</code> enables TFTP services.  The attribute specifies
            the path to the root directory served via TFTP. <code>tftp</code> is not
            supported for IPv6 addresses, and can only be specified on a single IPv4 address
            per network.
            <span class="since">Since 0.7.1</span>
          </dd>

          <dt><code>dhcp</code></dt>
          <dd>Also within the <code>ip</code> element there is an
            optional <code>dhcp</code> element. The presence of this element
            enables DHCP services on the virtual network. It will further
            contain one or more <code>range</code> elements. The
            <code>dhcp</code> element is not supported for IPv6, and
            is only supported on a single IP address per network for IPv4.
            <span class="since">Since 0.3.0</span>
            <dl>
              <dt><code>range</code></dt>
              <dd>The <code>start</code> and <code>end</code> attributes on the
                <code>range</code> element specify the boundaries of a pool of
                IPv4 addresses to be provided to DHCP clients. These two addresses
                must lie within the scope of the network defined on the parent
                <code>ip</code> element.  <span class="since">Since 0.3.0</span>
              </dd>
              <dt><code>host</code></dt>
              <dd>Within the <code>dhcp</code> element there may be zero or more
                <code>host</code> elements; these specify hosts which will be given
                names and predefined IP addresses by the built-in DHCP server. Any
                such element must specify the MAC address of the host to be assigned
                a given name (via the <code>mac</code> attribute), the IP to be
                assigned to that host (via the <code>ip</code> attribute), and the
                name to be given that host by the DHCP server (via the
                <code>name</code> attribute).  <span class="since">Since 0.4.5</span>
              </dd>
              <dt><code>bootp</code></dt>
              <dd>The optional <code>bootp</code>
                element specifies BOOTP options to be provided by the DHCP server.
                Two attributes are supported: <code>file</code> is mandatory and
                gives the file to be used for the boot image; <code>server</code> is
                optional and gives the address of the TFTP server from which the boot
                image will be fetched.  <code>server</code> defaults to the same host
                that runs the DHCP server, as is the case when the <code>tftp</code>
                element is used.  The BOOTP options currently have to be the same
                for all address ranges and statically assigned addresses.<span
                class="since">Since 0.7.1 (<code>server</code> since 0.7.3).</span>
              </dd>
            </dl>
          </dd>
        </dl>
      </dd>
    </dl>

    <h2><a name="examples">Example configuration</a></h2>

    <h3><a name="examplesNAT">NAT based network</a></h3>

    <p>
      This example is the so called "default" virtual network. It is
      provided and enabled out-of-the-box for all libvirt installations.
      This is a configuration that allows guest OS to get outbound
      connectivity regardless of whether the host uses ethernet, wireless,
      dialup, or VPN networking without requiring any specific admin
      configuration. In the absence of host networking, it at least allows
      guests to talk directly to each other.
    </p>

    <pre>
      &lt;network&gt;
        &lt;name&gt;default&lt;/name&gt;
        &lt;bridge name="virbr0" /&gt;
        &lt;forward mode="nat"/&gt;
        &lt;ip address="192.168.122.1" netmask="255.255.255.0"&gt;
          &lt;dhcp&gt;
            &lt;range start="192.168.122.2" end="192.168.122.254" /&gt;
          &lt;/dhcp&gt;
        &lt;/ip&gt;
        &lt;ip family="ipv6" address="2001:db8:ca2:2::1" prefix="64" /&gt;
      &lt;/network&gt;</pre>

    <h3><a name="examplesRoute">Routed network config</a></h3>

    <p>
      This is a variant on the default network which routes traffic
      from the virtual network to the LAN without applying any NAT.
      It requires that the IP address range be pre-configured in the
      routing tables of the router on the host network. This example
      further specifies that guest traffic may only go out via the
      <code>eth1</code> host network device.
    </p>

    <pre>
      &lt;network&gt;
        &lt;name&gt;local&lt;/name&gt;
        &lt;bridge name="virbr1" /&gt;
        &lt;forward mode="route" dev="eth1"/&gt;
        &lt;ip address="192.168.122.1" netmask="255.255.255.0"&gt;
          &lt;dhcp&gt;
            &lt;range start="192.168.122.2" end="192.168.122.254" /&gt;
          &lt;/dhcp&gt;
        &lt;/ip&gt;
        &lt;ip family="ipv6" address="2001:db8:ca2:2::1" prefix="64" /&gt;
      &lt;/network&gt;</pre>

    <h3><a name="examplesPrivate">Isolated network config</a></h3>

    <p>
      This variant provides a completely isolated private network
      for guests. The guests can talk to each other, and the host
      OS, but cannot reach any other machines on the LAN, due to
      the omission of the <code>forward</code> element in the XML
      description.
    </p>

    <pre>
      &lt;network&gt;
        &lt;name&gt;private&lt;/name&gt;
        &lt;bridge name="virbr2" /&gt;
        &lt;ip address="192.168.152.1" netmask="255.255.255.0"&gt;
          &lt;dhcp&gt;
            &lt;range start="192.168.152.2" end="192.168.152.254" /&gt;
          &lt;/dhcp&gt;
        &lt;/ip&gt;
        &lt;ip family="ipv6" address="2001:db8:ca2:3::1" prefix="64" /&gt;
      &lt;/network&gt;</pre>

    <h3><a name="examplesBridge">Using an existing host bridge</a></h3>

    <p>
      This shows how to use a pre-existing host bridge "br0". The
      guests will effectively be directly connected to the physical
      network (i.e. their IP addresses will all be on the subnet of
      the physical network, and there will be no restrictions on
      inbound or outbound connections).
    </p>

    <pre>
      &lt;network&gt;
        &lt;name&gt;host-bridge&lt;/name&gt;
        &lt;forward mode="bridge"/&gt;
        &lt;bridge name="br0"/&gt;
      &lt;/network&gt;</pre>

    <h3><a name="examplesDirect">Using a macvtap "direct" connection</a></h3>

    <p>
      This shows how to use macvtap to connect to the physical network
      directly through one of a group of physical devices (without
      using a host bridge device). As with the host bridge network,
      the guests will effectively be directly connected to the
      physical network so their IP addresses will all be on the subnet
      of the physical network, and there will be no restrictions on
      inbound or outbound connections. Note that, due to a limitation
      in the implementation of macvtap, these connections do not allow
      communication directly between the host and the guests - if you
      require this you will either need the attached physical switch
      to be operating in a mirroring mode (so that all traffic coming
      to the switch is reflected back to the host's interface), or
      provide alternate means for this communication (e.g. a second
      interface on each guest that is connected to an isolated
      network). The other forward modes that use macvtap (private,
      vepa, and passthrough) would be used in a similar fashion.
    </p>

    <pre>
      &lt;network&gt;
        &lt;name&gt;direct-macvtap&lt;/name&gt;
        &lt;forward mode="bridge"&gt;
          &lt;interface dev="eth20"/&gt;
          &lt;interface dev="eth21"/&gt;
          &lt;interface dev="eth22"/&gt;
          &lt;interface dev="eth23"/&gt;
          &lt;interface dev="eth24"/&gt;
        &lt;/forward&gt;
      &lt;/network&gt;</pre>

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