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Someone in an IRC channel or an email pointed out a few days ago that the examples of IPv6 addresses in the libvirt documentation were not in the officially reserved "documentation" range. This addresses their concern.
594 lines
28 KiB
HTML
594 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"/>
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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. Firewall rules are also installed
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that prevent incoming sessions from the physical network
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to the guests, but outgoing sessions are unrestricted (as
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are sessions from the host to the guests, and between
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guests on the same network.)<span class="since">Since
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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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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. 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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<dns>
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<txt name="example" value="example value" />
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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
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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. The
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<code>dhcp</code> element is not supported for IPv6, and
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is only supported on a single IP address per network for IPv4.
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<span class="since">Since 0.3.0</span>
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<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>
|
|
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>
|
|
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>
|