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203 lines
7.3 KiB
HTML
203 lines
7.3 KiB
HTML
<html>
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<body>
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<h1>Network XML format</h1>
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<ul id="toc">
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</ul>
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<p>
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This page provides an introduction to the network XML format. For background
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information on the concepts referred to here, consult the <a href="archnetwork.html">network driver architecture</a>
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page.
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</p>
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<h2><a name="elements">Element and attribute overview</a></h2>
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<p>
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The root element required for all virtual networks is
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named <code>network</code> and has no attributes.
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The network XML format is available <span class="since">since 0.3.0</span>
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</p>
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<h3><a name="elementsMetadata">General metadata</a></h3>
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<p>
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The first elements provide basic metadata about the virtual
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network.
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</p>
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<pre>
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<network>
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<name>default</name>
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<uuid>3e3fce45-4f53-4fa7-bb32-11f34168b82b</uuid>
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...</pre>
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<dl>
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<dt><code>name</code></dt>
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<dd>The content of the <code>name</code> element provides
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a short name for the virtual network. This name should
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consist only of alpha-numeric characters and is required
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to be unique within the scope of a single host. It is
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used to form the filename for storing the persistent
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configuration file. <span class="since">Since 0.3.0</span></dd>
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<dt><code>uuid</code></dt>
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<dd>The content of the <code>uuid</code> element provides
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a globally unique identifier for the virtual network.
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The format must be RFC 4122 compliant, eg <code>3e3fce45-4f53-4fa7-bb32-11f34168b82b</code>.
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If omitted when defining/creating a new network, a random
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UUID is generated. <span class="since">Since 0.3.0</span></dd>
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</dl>
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<h3><a name="elementsConnect">Connectivity</a></h3>
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<p>
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The next set of elements control how a virtual network is
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provided connectivity to the physical LAN (if at all).
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</p>
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<pre>
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...
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<bridge name="virbr0" />
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<forward mode="nat" dev="eth0"/>
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...</pre>
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<dl>
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<dt><code>bridge</code></dt>
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<dd>The <code>name</code> attribute on the <code>bridge</code> element
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defines the name of a bridge device which will be used to construct
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the virtual network. The virtual machines will be connected to this
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bridge device allowing them to talk to each other. The bridge device
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may also be connected to the LAN. It is recommended that bridge
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device names started with the prefix <code>vir</code>, but the name
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<code>virbr0</code> is reserved for the "default" virtual network.
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This element should always be provided when defining a new network.
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<span class="since">Since 0.3.0</span>
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</dd>
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<dt><code>forward</code></dt>
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<dd>Inclusion of the <code>forward</code> element indicates that
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the virtual network is to be connected to the physical LAN. If
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no attributes are set, NAT forwarding will be used for connectivity.
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Firewall rules will allow forwarding to any other network device whether
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ethernet, wireless, dialup, or VPN. If the <code>dev</code> attribute
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is set, the firewall rules will restrict forwarding to the named
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device only. If the <code>mode</code> attribute is set to <code>route</code>
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then the traffic will not have NAT applied. This presumes that the
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local LAN router has suitable routing table entries to return traffic
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to this host. <span class="since">Since 0.3.0; 'mode' attribute since
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0.4.2</span></dd>
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</dl>
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<h3><a name="elementsAddress">Addressing</a></h3>
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<p>
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The final set of elements define the IPv4 address range available,
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and optionally enable DHCP sevices.
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</p>
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<pre>
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...
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<ip address="192.168.122.1" netmask="255.255.255.0">
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<dhcp>
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<range start="192.168.122.2" end="192.168.122.254" />
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</dhcp>
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</ip>
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</network></pre>
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<dl>
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<dt><code>ip</code></dt>
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<dd>The <code>address</code> attribute defines an IPv4 address in
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dotted-decimal format, that will be configured on the bridge
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device associated with the virtual network. To the guests this
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address will be their default route. The <code>netmask</code>
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attribute defines the significant bits of the network address,
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again specified in dotted-decimal format. <span class="since">Since 0.3.0</span>
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</dd>
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<dt><code>dhcp</code></dt>
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<dd>Immediately within the <code>ip</code> element there is an
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optional <code>dhcp</code> element. The presence of this element
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enables DHCP services on the virtual network. It will further
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contain one or more <code>range</code> elements.
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<span class="since">Since 0.3.0</span>
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</dd>
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<dt><code>range</code></dt>
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<dd>The <code>start</code> and <code>end</code> attributes on the
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<code>range</code> element specify the boundaries of a pool of
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IPv4 addresses to be provided to DHCP clients. These two addresses
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must lie within the scope of the network defined on the parent
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<code>ip</code> element. <span class="since">Since 0.3.0</span>
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</dd>
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</dl>
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<h2><a name="examples">Example configuration</a></h2>
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<h3><a name="examplesNAT">NAT based network</a></h3>
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<p>
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This example is the so called "default" virtual network. It is
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provided and enabled out-of-the-box for all libvirt installations.
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This is a configuration that allows guest OS to get outbound
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connectivity regardless of whether the host uses ethernet, wireless,
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dialup, or VPN networking without requiring any specific admin
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configuration. In the absence of host networking, it at least allows
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guests to talk directly to each other.
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</p>
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<pre>
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<network>
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<name>default</name>
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<bridge name="virbr0" />
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<forward type="nat"/>
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<ip address="192.168.122.1" netmask="255.255.255.0">
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<dhcp>
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<range start="192.168.122.2" end="192.168.122.254" />
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</dhcp>
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</ip>
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</network></pre>
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<h3><a name="examplesRoute">Routed network config</a></h3>
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<p>
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This is a variant on the default network which routes traffic
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from the virtual network to the LAN without applying any NAT.
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It requires that the IP address range be pre-configured in the
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routing tables of the router on the host network. This example
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further specifies that guest traffic may only go out via the
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<code>eth1</code> host network device.
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</p>
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<pre>
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<network>
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<name>local</name>
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<bridge name="virbr1" />
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<forward type="route" dev="eth1"/>
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<ip address="192.168.122.1" netmask="255.255.255.0">
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<dhcp>
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<range start="192.168.122.2" end="192.168.122.254" />
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</dhcp>
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</ip>
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</network></pre>
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<h3><a name="examplesPrivate">Isolated network config</a></h3>
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<p>
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This variant provides a completely isolated private network
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for guests. The guests can talk to each other, and the host
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OS, but cannot reach any other machines on the LAN, due to
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the omission of the <code>forward</code> element in the XML
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description.
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</p>
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<pre>
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<network>
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<name>private</name>
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<bridge name="virbr2" />
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<ip address="192.168.152.1" netmask="255.255.255.0">
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<dhcp>
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<range start="192.168.152.2" end="192.168.152.254" />
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</dhcp>
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</ip>
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</network></pre>
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</body>
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</html>
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