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<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE topic PUBLIC "-//OASIS//DTD DITA Topic//EN" "topic.dtd">
<topic xml:lang="en-us" id="network_hostonly">
<title>Host-Only Networking</title>
<body>
<p>Host-only networking can be thought of as a hybrid between the bridged and internal networking modes. As with
bridged networking, the virtual machines can talk to each other and the host as if they were connected through a
physical Ethernet switch. As with internal networking, a physical networking interface need not be present, and
the virtual machines cannot talk to the world outside the host since they are not connected to a physical
networking interface. </p>
<p>When host-only networking is used, <ph conkeyref="vbox-conkeyref-phrases/product-name"/> creates a new software
interface on the host which then appears next to your existing network interfaces. In other words, whereas with
bridged networking an existing physical interface is used to attach virtual machines to, with host-only networking
a new <i>loopback</i> interface is created on the host. And whereas with internal networking, the traffic between
the virtual machines cannot be seen, the traffic on the loopback interface on the host can be intercepted. </p>
<note>
<p>Hosts running recent macOS versions do not support host-only adapters. These adapters are replaced by host-only
networks, which define a network mask and an IP address range, where the host network interface receives the
lowest address in the range. </p>
<p>The host network interface gets added and removed dynamically by the operating system, whenever a host-only
network is used by virtual machines. </p>
<p>On macOS hosts, choose the <b outputclass="bold">Host-Only Network</b> option when configuring a network
adapter. The <b outputclass="bold">Host-Only Adapter</b> option is provided for legacy support. </p>
</note>
<p>Host-only networking is particularly useful for preconfigured virtual appliances, where multiple virtual machines
are shipped together and designed to cooperate. For example, one virtual machine may contain a web server and a
second one a database, and since they are intended to talk to each other, the appliance can instruct <ph
conkeyref="vbox-conkeyref-phrases/product-name"/> to set up a host-only network for the two. A second, bridged,
network would then connect the web server to the outside world to serve data to, but the outside world cannot
connect to the database. </p>
<p>To enable a host-only network interface for a virtual machine, do either of the following: </p>
<ul>
<li>
<p>Go to the <b outputclass="bold">Network</b> page in the virtual machine's <b outputclass="bold">Settings</b>
dialog and select an <b outputclass="bold">Adapter</b> tab. Ensure that the <b outputclass="bold">Enable
Network Adapter</b> check box is selected and choose <b outputclass="bold">Host-Only Adapter</b> for the <b
outputclass="bold">Attached To</b> field. </p>
</li>
<li>
<p>On the command line, use </p>
<p><userinput>VBoxManage modifyvm <varname>VM-name</varname> --nic<varname>N</varname>=hostonly --host-only-adapter<varname>N</varname>=<varname>interface-name</varname></userinput>.</p>
<p>See <xref href="vboxmanage-modifyvm.dita"/>.</p>
</li>
</ul>
<p>For host-only networking, as with internal networking, you may find the DHCP server useful that is built into <ph
conkeyref="vbox-conkeyref-phrases/product-name"/>. This is enabled by default and manages the IP addresses in
the host-only network. Without the DHCP server you would need to configure all IP addresses statically. </p>
<ul>
<li>
<p>In <ph conkeyref="vbox-conkeyref-phrases/vbox-mgr"/> you can configure the DHCP server by choosing <b
outputclass="bold">File</b>, <b outputclass="bold">Tools</b>, <b outputclass="bold">Network Manager</b>. The
Network Manager window lists all host-only networks which are presently in use. Select the network name and
then use the <b outputclass="bold">DHCP Server</b> tab to configure DHCP server settings. See <xref
href="network-manager.dita#network-manager"/>. </p>
</li>
<li>
<p>Alternatively, you can use the <userinput>VBoxManage dhcpserver</userinput> command. See <xref
href="vboxmanage-dhcpserver.dita"/>. </p>
</li>
</ul>
<note>
<p>On Linux and macOS hosts the number of host-only interfaces is limited to 128. There is no such limit for
Oracle Solaris and Windows hosts. </p>
</note>
<p>On Linux, macOS and Solaris <ph conkeyref="vbox-conkeyref-phrases/product-name"/> will only allow IP addresses in
192.168.56.0/21 range to be assigned to host-only adapters. For IPv6 only link-local addresses are allowed. If
other ranges are required, they can be enabled by creating <filepath>/etc/vbox/networks.conf</filepath> and
specifying allowed ranges there. For example, to allow 10.0.0.0/8 and 192.168.0.0/16 IPv4 ranges as well as
2001::/64 range put the following lines into <filepath>/etc/vbox/networks.conf</filepath>: </p>
<pre xml:space="preserve"> * 10.0.0.0/8 192.168.0.0/16
* 2001::/64
</pre>
<p>Lines starting with the hash <userinput>#</userinput> are ignored. The following example allows any addresses,
effectively disabling range control: </p>
<pre xml:space="preserve"> * 0.0.0.0/0 ::/0
</pre>
<p>If the file exists, but no ranges are specified in it, no addresses will be assigned to host-only adapters. The
following example effectively disables all ranges: </p>
<pre xml:space="preserve"> # No addresses are allowed for host-only adapters
</pre>
</body>
</topic>
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