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52e3b3d1bb
In a recent expansion of the documentation on network forward modes, I incorrectly stated that incoming sessions to guests on routed networks were blocked. This is true for guests on NATed networks, but not routed. This patch corrects that error, and adds a pointer to the nwfilter page for those who do want to restrict incoming sessions to hosts on routed networks.
603 lines
28 KiB
HTML
603 lines
28 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" stp="on" delay="5"/>
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<domain name="example.com"/>
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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
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network. This element should always be provided when defining
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a new network with a <code><forward></code> mode of
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"nat" or "route" (or an isolated network with
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no <code><forward></code> element).
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Attribute <code>stp</code> specifies if Spanning Tree Protocol
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is 'on' or 'off' (default is
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'on'). Attribute <code>delay</code> sets the bridge's forward
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delay value in seconds (default is 0).
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<span class="since">Since 0.3.0</span>
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</dd>
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<dt><code>domain</code></dt>
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<dd>
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The <code>name</code> attribute on the <code>domain</code>
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element defines the DNS domain of the DHCP server. This
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element is optional, and is only used for those networks with
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a <code><forward></code> mode of "nat" or "route" (or an
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isolated network with no <code><forward></code>
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element). <span class="since">Since 0.4.5</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
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LAN.<span class="since">Since 0.3.0.</span>
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The <code>mode</code> attribute determines the method of
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forwarding. If there is no <code>forward</code> element, the
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network will be isolated from any other network (unless a
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guest connected to that network is acting as a router, of
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course). The following are valid settings
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for <code>mode</code> (if there is a <code>forward</code>
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element but mode is not specified, <code>mode='nat'</code> is
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assumed):
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<dl>
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<dt><code>nat</code></dt>
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<dd>
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All traffic between guests connected to this network and
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the physical network will be forwarded to the physical
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network via the host's IP routing stack, after the guest's
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IP address is translated to appear as the host machine's
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public IP address (a.k.a. Network Address Translation, or
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"NAT"). This allows multiple guests, all having access to
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the physical network, on a host that is only allowed a
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single public IP address. If a network has any IPv6
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addresses defined, the IPv6 traffic will be forwarded
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using plain routing, since IPv6 has no concept of NAT.
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Firewall rules will allow outbound connections to any
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other network device whether ethernet, wireless, dialup,
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or VPN. If the <code>dev</code> attribute is set, the
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firewall rules will restrict forwarding to the named
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device only. Inbound connections from other networks are
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all prohibited; all connections between guests on the same
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network, and to/from the host to the guests, are
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unrestricted and not NATed.<span class="since">Since
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0.4.2</span>
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</dd>
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<dt><code>route</code></dt>
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<dd>
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Guest network traffic will be forwarded to the physical
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network via the host's IP routing stack, but without
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having NAT applied. Again, if the <code>dev</code>
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attribute is set, firewall rules will restrict forwarding
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to the named device only. This presumes that the local LAN
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router has suitable routing table entries to return
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traffic to this host. All incoming and outgoing sessions
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to guest on these networks are unrestricted. (To restrict
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incoming traffic to a guest on a routed network, you can
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configure <a href="formatnwfilter.html">nwfilter rules</a>
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on the guest's interfaces.)
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<span class="since">Since 0.4.2</span>
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</dd>
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<dt><code>bridge</code></dt>
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<dd>
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This network describes either 1) an existing host bridge
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that was configured outside of libvirt (if
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a <code><bridge name='xyz'/></code> element has been
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specified), or 2) an interface or group of interfaces to
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be used for a "direct" connection via macvtap using
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macvtap's "bridge" mode (if the forward element has one or
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more <code><interface></code> subelements)
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(see <a href="formatdomain.html#elementsNICSDirect">Direct
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attachment to physical interface</a> for descriptions of
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the various macvtap modes). libvirt doesn't attempt to
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manage the bridge interface at all, thus
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the <code><bridge></code> element's <code>stp</code>
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and <code>delay</code> attributes are not allowed; no
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iptables rules, IP addresses, or DHCP/DNS services are
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added; at the IP level, the guest interface appears to be
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directly connected to the physical
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interface.<span class="since">Since 0.9.4</span>
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</dd>
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<dt><code>private</code></dt>
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<dd>
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This network uses a macvtap "direct" connection in
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"private" mode to connect each guest to the network. The
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physical interface to be used will be picked from among
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those listed in <code><interface></code> subelements
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of the <code><forward></code> element; when using
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802.1Qbh mode (as indicated by
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the <code><virtualport></code> type attribute - note
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that this requires an 802.1Qbh-capable hardware switch),
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each physical interface can only be in use by a single
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guest interface at a time; in modes other than 802.1Qbh,
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multiple guest interfaces can share each physical
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interface (libvirt will attempt to balance usage between
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all available interfaces).<span class="since">Since
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0.9.4</span>
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</dd>
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<dt><code>vepa</code></dt>
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<dd>
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This network uses a macvtap "direct" connection in "vepa"
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mode to connect each guest to the network (this requires
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that the physical interfaces used be connected to a
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vepa-capable hardware switch. The physical interface to be
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used will be picked from among those listed
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in <code><interface></code> subelements of
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the <code><forward></code> element; multiple guest
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interfaces can share each physical interface (libvirt will
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attempt to balance usage between all available
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interfaces).<span class="since">Since 0.9.4</span>
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</dd>
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<dt><code>passthrough</code></dt>
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<dd>
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This network uses a macvtap "direct" connection in
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"passthrough" mode to connect each guest to the network
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(note that this is <i>not</i> the same thing as "PCI
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passthrough"). The physical interface to be used will be
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picked from among those listed
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in <code><interface></code> subelements of
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the <code><forward></code> element. Each physical
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interface can only be in use by a single guest interface
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at a time, so libvirt will keep track of which interfaces
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are currently in use, and only assign unused interfaces
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(if there are no available physical interfaces when a
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domain interface is being attached, an error will be
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logged, and the operation causing the attach will fail
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(usually either a domain start, or a hotplug interface
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attach to a domain).<span class="since">Since 0.9.4</span>
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</dd>
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</dl>
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As mentioned above, a <code><forward></code> element can
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have multiple <code><interface></code> subelements, each
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one giving the name of a physical interface that can be used
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for this network <span class="since">Since 0.9.4</span>:
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<pre>
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...
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<forward mode='passthrough'>
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<interface dev='eth10'/>
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<interface dev='eth11'/>
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<interface dev='eth12'/>
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<interface dev='eth13'/>
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<interface dev='eth14'/>
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</forward>
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...
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</pre>
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When a guest interface is being constructed, libvirt will pick
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an interface from this list to use for the connection. In
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modes where physical interfaces can be shared by multiple
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guest interfaces, libvirt will choose the interface that
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currently has the least number of connections. For those modes
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that do not allow sharing of the physical device (in
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particular, 'passthrough' mode, and 'private' mode when using
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802.1Qbh), libvirt will choose an unused physical interface
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or, if it can't find an unused interface, fail the operation.
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</dd>
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</dl>
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<h5><a name="elementQoS">Quality of service</a></h5>
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<pre>
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...
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<forward mode='nat' dev='eth0'/>
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<b><bandwidth>
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<inbound average='1000' peak='5000' burst='5120'/>
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<outbound average='128' peak='256' burst='256'/>
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</bandwidth></b>
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...</pre>
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<p>
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This part of network XML provides setting quality of service. Incoming
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and outgoing traffic can be shaped independently. The
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<code>bandwidth</code> element can have at most one <code>inbound</code>
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and at most one <code>outbound</code> child elements. Leaving any of these
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children element out result in no QoS applied on that traffic direction.
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So, when you want to shape only network's incoming traffic, use
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<code>inbound</code> only, and vice versa. Each of these elements have one
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mandatory attribute <code>average</code>. It specifies average bit rate on
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interface being shaped. Then there are two optional attributes:
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<code>peak</code>, which specifies maximum rate at which bridge can send
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data, and <code>burst</code>, amount of bytes that can be burst at
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<code>peak</code> speed. Accepted values for attributes are integer
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numbers, The units for <code>average</code> and <code>peak</code> attributes
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are kilobytes per second, and for the <code>burst</code> just kilobytes.
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The rate is shared equally within domains connected to the network.
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Moreover, <code>bandwidth</code> element can be included in
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<code>portgroup</code> element.
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<span class="since">Since 0.9.4</span>
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</p>
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<h5><a name="elementsPortgroup">Portgroups</a></h5>
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<pre>
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...
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<forward mode='private'/>
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<interface dev="eth20"/>
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<interface dev="eth21"/>
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<interface dev="eth22"/>
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<interface dev="eth23"/>
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<interface dev="eth24"/>
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</forward>
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<b><portgroup name='engineering' default='yes'>
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<virtualport type='802.1Qbh'>
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<parameters profileid='test'/>
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</virtualport>
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<bandwidth>
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<inbound average='1000' peak='5000' burst='5120'/>
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<outbound average='1000' peak='5000' burst='5120'/>
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</bandwidth>
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</portgroup></b>
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<b><portgroup name='sales'>
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<virtualport type='802.1Qbh'>
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<parameters profileid='salestest'/>
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</virtualport>
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<bandwidth>
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<inbound average='500' peak='2000' burst='2560'/>
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<outbound average='128' peak='256' burst='256'/>
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</bandwidth>
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</portgroup></b>
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...</pre>
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<p>
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<span class="since">Since 0.9.4</span>
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A portgroup provides a method of easily putting guest
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connections to the network into different classes, with each
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class potentially having a different level/type of service.
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<span class="since">Since 0.9.4</span> Each
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network can have multiple portgroup elements (and one of those
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can optionally be designated as the 'default' portgroup for the
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network), and each portgroup has a name, as well as various
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subelements associated with it. The currently supported
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subelements are <code><bandwidth></code>
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(documented <a href="formatdomain.html#elementQoS">here</a>)
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and <code><virtualport></code>
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(documented <a href="formatdomain.html#elementsNICSDirect">here</a>).
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If a domain interface definition specifies a portgroup (by
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adding a <code>portgroup</code> attribute to
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the <code><source></code> subelement), that portgroup's
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info will be merged into the interface's configuration. If no
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portgroup is given in the interface definition, and one of the
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network's portgroups has <code>default='yes'</code>, that
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default portgroup will be used. If no portgroup is given in the
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interface definition, and there is no default portgroup, then
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none will be used. Any <code><bandwidth></code>
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or <code><virtualport></code> specified directly in the
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domain XML will take precedence over any setting in the chosen
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portgroup.
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</p>
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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 addresses (IPv4 and/or
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IPv6, as well as MAC) to be assigned to the bridge device
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associated with the virtual network, and optionally enable DHCP
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services. These elements are only valid for isolated networks
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(no <code>forward</code> element specified), and for those with
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a forward mode of 'route' or 'nat'.
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</p>
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<pre>
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...
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<mac address='00:16:3E:5D:C7:9E'/>
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<domain name="example.com"/>
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<dns>
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<txt name="example" value="example value" />
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<host ip='192.168.122.2'>
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<hostname>myhost</hostname>
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<hostname>myhostalias</hostname>
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</dns>
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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="192.168.122.100" end="192.168.122.254" />
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<host mac="00:16:3e:77:e2:ed" name="foo.example.com" ip="192.168.122.10" />
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<host mac="00:16:3e:3e:a9:1a" name="bar.example.com" ip="192.168.122.11" />
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</dhcp>
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</ip>
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<ip family="ipv6" address="2001:db8:ca2:2::1" prefix="64" />
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</network></pre>
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<dl>
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<dt><code>mac</code></dt>
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<dd>The <code>address</code> attribute defines a MAC
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(hardware) address formatted as 6 groups of 2-digit
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hexadecimal numbers, the groups separated by colons
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(eg, <code>"52:54:00:1C:DA:2F"</code>). This MAC address is
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assigned to the bridge device when it is created. Generally
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it is best to not specify a MAC address when creating a
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network - in this case, if a defined MAC address is needed for
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proper operation, libvirt will automatically generate a random
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MAC address and save it in the config. Allowing libvirt to
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generate the MAC address will assure that it is compatible
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with the idiosyncrasies of the platform where libvirt is
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running. <span class="since">Since 0.8.8</span>
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</dd>
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<dt><code>dns</code></dt><dd>
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The dns element of a network contains configuration information for the
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virtual network's DNS server. <span class="since">Since 0.9.3</span>
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Currently supported elements are:
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<dl>
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<dt><code>txt</code></dt>
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<dd>A <code>dns</code> element can have 0 or more <code>txt</code> elements.
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Each txt element defines a DNS TXT record and has two attributes, both
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required: a name that can be queried via dns, and a value that will be
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returned when that name is queried. names cannot contain embedded spaces
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or commas. value is a single string that can contain multiple values
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separated by commas. <span class="since">Since 0.9.3</span>
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</dd>
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<dt><code>host</code></dt>
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<dd>The <code>host</code> element within <code>dns</code> is the
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definition of DNS hosts to be passed to the DNS service. The IP
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address is identified by the <code>ip</code> attribute and the names
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for that IP address are identified in the <code>hostname</code>
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sub-elements of the <code>host</code> element.
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<span class="since">Since 0.9.3</span>
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</dd>
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</dl>
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</dd>
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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, or an IPv6 address in standard
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colon-separated hexadecimal format, that will be configured on
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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. For IPv4 addresses, 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. For IPv6 addresses,
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and as an alternate method for IPv4 addresses, you can specify
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the significant bits of the network address with the <code>prefix</code>
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attribute, which is an integer (for example, <code>netmask='255.255.255.0'</code>
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could also be given as <code>prefix='24'</code>. The <code>family</code>
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attribute is used to specify the type of address - 'ipv4' or 'ipv6'; if no
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<code>family</code> is given, 'ipv4' is assumed. A network can have more than
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one of each family of address defined, but only a single address can have a
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<code>dhcp</code> or <code>tftp</code> element. <span class="since">Since 0.3.0;
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IPv6, multiple addresses on a single network, <code>family</code>, and
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<code>prefix</code> since 0.8.7</span>
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<dl>
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<dt><code>tftp</code></dt>
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<dd>Immediately within
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the <code>ip</code> element there is an optional <code>tftp</code>
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element. The presence of this element and of its attribute
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<code>root</code> enables TFTP services. The attribute specifies
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the path to the root directory served via TFTP. <code>tftp</code> is not
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supported for IPv6 addresses, and can only be specified on a single IPv4 address
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per network.
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<span class="since">Since 0.7.1</span>
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</dd>
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<dt><code>dhcp</code></dt>
|
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<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>
|
|
<network>
|
|
<name>default</name>
|
|
<bridge name="virbr0" />
|
|
<forward mode="nat"/>
|
|
<ip address="192.168.122.1" netmask="255.255.255.0">
|
|
<dhcp>
|
|
<range start="192.168.122.2" end="192.168.122.254" />
|
|
</dhcp>
|
|
</ip>
|
|
<ip family="ipv6" address="2001:db8:ca2:2::1" prefix="64" />
|
|
</network></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>
|
|
<network>
|
|
<name>local</name>
|
|
<bridge name="virbr1" />
|
|
<forward mode="route" dev="eth1"/>
|
|
<ip address="192.168.122.1" netmask="255.255.255.0">
|
|
<dhcp>
|
|
<range start="192.168.122.2" end="192.168.122.254" />
|
|
</dhcp>
|
|
</ip>
|
|
<ip family="ipv6" address="2001:db8:ca2:2::1" prefix="64" />
|
|
</network></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>
|
|
<network>
|
|
<name>private</name>
|
|
<bridge name="virbr2" />
|
|
<ip address="192.168.152.1" netmask="255.255.255.0">
|
|
<dhcp>
|
|
<range start="192.168.152.2" end="192.168.152.254" />
|
|
</dhcp>
|
|
</ip>
|
|
<ip family="ipv6" address="2001:db8:ca2:3::1" prefix="64" />
|
|
</network></pre>
|
|
|
|
<h3><a name="examplesBridge">Using an existing host bridge</a></h3>
|
|
|
|
<p>
|
|
<span class="since">Since 0.9.4</span>
|
|
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>
|
|
<network>
|
|
<name>host-bridge</name>
|
|
<forward mode="bridge"/>
|
|
<bridge name="br0"/>
|
|
</network></pre>
|
|
|
|
<h3><a name="examplesDirect">Using a macvtap "direct" connection</a></h3>
|
|
|
|
<p>
|
|
<span class="since">Since 0.9.4, QEMU and KVM only, requires
|
|
Linux kernel 2.6.34 or newer</span>
|
|
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>
|
|
<network>
|
|
<name>direct-macvtap</name>
|
|
<forward mode="bridge">
|
|
<interface dev="eth20"/>
|
|
<interface dev="eth21"/>
|
|
<interface dev="eth22"/>
|
|
<interface dev="eth23"/>
|
|
<interface dev="eth24"/>
|
|
</forward>
|
|
</network></pre>
|
|
|
|
</body>
|
|
</html>
|