| 1 | <?xml version='1.0' encoding='UTF-8'?>
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| 2 | <!DOCTYPE topic PUBLIC "-//OASIS//DTD DITA Topic//EN" "topic.dtd">
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| 3 | <topic xml:lang="en-us" id="network_hostonly">
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| 4 | <title>Host-Only Networking</title>
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| 5 |
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| 6 | <body>
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| 7 | <p>
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| 8 | Host-only networking can be thought of as a hybrid between the
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| 9 | bridged and internal networking modes. As with bridged networking,
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| 10 | the virtual machines can talk to each other and the host as if
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| 11 | they were connected through a physical Ethernet switch. As with
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| 12 | internal networking, a physical networking interface need not be
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| 13 | present, and the virtual machines cannot talk to the world outside
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| 14 | the host since they are not connected to a physical networking
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| 15 | interface.
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| 16 | </p>
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| 17 | <p>
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| 18 | When host-only networking is used, Oracle VM VirtualBox creates a new
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| 19 | software interface on the host which then appears next to your
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| 20 | existing network interfaces. In other words, whereas with bridged
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| 21 | networking an existing physical interface is used to attach
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| 22 | virtual machines to, with host-only networking a new
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| 23 | <i>loopback</i> interface is created on the host.
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| 24 | And whereas with internal networking, the traffic between the
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| 25 | virtual machines cannot be seen, the traffic on the loopback
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| 26 | interface on the host can be intercepted.
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| 27 | </p>
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| 28 | <note>
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| 29 | <p>
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| 30 | Hosts running recent macOS versions do not support host-only
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| 31 | adapters. These adapters are replaced by host-only networks,
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| 32 | which define a network mask and an IP address range, where the
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| 33 | host network interface receives the lowest address in the range.
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| 34 | </p>
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| 35 | <p>
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| 36 | The host network interface gets added and removed dynamically by
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| 37 | the operating system, whenever a host-only network is used by
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| 38 | virtual machines.
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| 39 | </p>
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| 40 | <p>
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| 41 | On macOS hosts, choose the <b outputclass="bold">Host-Only
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| 42 | Network</b> option when configuring a network adapter.
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| 43 | The <b outputclass="bold">Host-Only Adapter</b> option is
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| 44 | provided for legacy support.
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| 45 | </p>
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| 46 | </note>
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| 47 | <p>
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| 48 | Host-only networking is particularly useful for preconfigured
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| 49 | virtual appliances, where multiple virtual machines are shipped
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| 50 | together and designed to cooperate. For example, one virtual
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| 51 | machine may contain a web server and a second one a database, and
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| 52 | since they are intended to talk to each other, the appliance can
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| 53 | instruct Oracle VM VirtualBox to set up a host-only network for the two.
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| 54 | A second, bridged, network would then connect the web server to
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| 55 | the outside world to serve data to, but the outside world cannot
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| 56 | connect to the database.
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| 57 | </p>
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| 58 | <p>
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| 59 | To enable a host-only network interface for a virtual machine, do
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| 60 | either of the following:
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| 61 | </p>
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| 62 | <ul>
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| 63 | <li>
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| 64 | <p>
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| 65 | Go to the <b outputclass="bold">Network</b> page in the
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| 66 | virtual machine's <b outputclass="bold">Settings</b>
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| 67 | dialog and select an <b outputclass="bold">Adapter</b>
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| 68 | tab. Ensure that the <b outputclass="bold">Enable Network
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| 69 | Adapter</b> check box is selected and choose
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| 70 | <b outputclass="bold">Host-Only Adapter</b> for the
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| 71 | <b outputclass="bold">Attached To</b> field.
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| 72 | </p>
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| 73 | </li>
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| 74 | <li>
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| 75 | <p>
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| 76 | On the command line, use <userinput>VBoxManage modifyvm
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| 77 | vmname --nic <varname>x</varname> hostonly</userinput>. See
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| 78 | <xref href="vboxmanage-modifyvm.dita"/>.
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| 79 | </p>
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| 80 | </li>
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| 81 | </ul>
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| 82 | <p>
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| 83 | For host-only networking, as with internal networking, you may
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| 84 | find the DHCP server useful that is built into Oracle VM VirtualBox.
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| 85 | This is enabled by default and manages the IP addresses in the
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| 86 | host-only network. Without the DHCP server you would need to
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| 87 | configure all IP addresses statically.
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| 88 | </p>
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| 89 | <ul>
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| 90 | <li>
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| 91 | <p>
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| 92 | In VirtualBox Manager you can configure the DHCP server by choosing
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| 93 | <b outputclass="bold">File</b>,
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| 94 | <b outputclass="bold">Tools</b>,
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| 95 | <b outputclass="bold">Network Manager</b>. The Network
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| 96 | Manager window lists all host-only networks which are
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| 97 | presently in use. Select the network name and then use the
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| 98 | <b outputclass="bold">DHCP Server</b> tab to configure
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| 99 | DHCP server settings. See <xref href="network-manager.dita#network-manager"/>.
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| 100 | </p>
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| 101 | </li>
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| 102 | <li>
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| 103 | <p>
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| 104 | Alternatively, you can use the <userinput>VBoxManage
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| 105 | dhcpserver</userinput> command. See
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| 106 | <xref href="vboxmanage-dhcpserver.dita"/>.
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| 107 | </p>
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| 108 | </li>
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| 109 | </ul>
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| 110 | <note>
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| 111 | <p>
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| 112 | On Linux and macOS hosts the number of host-only interfaces is
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| 113 | limited to 128. There is no such limit for Oracle Solaris and
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| 114 | Windows hosts.
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| 115 | </p>
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| 116 | </note>
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| 117 | <p>
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| 118 | On Linux, macOS and Solaris Oracle VM VirtualBox will only allow IP
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| 119 | addresses in 192.168.56.0/21 range to be assigned to host-only
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| 120 | adapters. For IPv6 only link-local addresses are allowed. If other
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| 121 | ranges are desired, they can be enabled by creating
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| 122 | <filepath>/etc/vbox/networks.conf</filepath> and specifying
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| 123 | allowed ranges there. For example, to allow 10.0.0.0/8 and
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| 124 | 192.168.0.0/16 IPv4 ranges as well as 2001::/64 range put the
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| 125 | following lines into <filepath>/etc/vbox/networks.conf</filepath>:
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| 126 | </p>
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| 127 | <pre xml:space="preserve"> * 10.0.0.0/8 192.168.0.0/16
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| 128 | * 2001::/64
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| 129 | </pre>
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| 130 | <p>
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| 131 | Lines starting with the hash <userinput>#</userinput> are ignored. The
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| 132 | following example allows any addresses, effectively disabling
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| 133 | range control:
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| 134 | </p>
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| 135 | <pre xml:space="preserve"> * 0.0.0.0/0 ::/0
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| 136 | </pre>
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| 137 | <p>
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| 138 | If the file exists, but no ranges are specified in it, no
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| 139 | addresses will be assigned to host-only adapters. The following
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| 140 | example effectively disables all ranges:
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| 141 | </p>
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| 142 | <pre xml:space="preserve"> # No addresses are allowed for host-only adapters
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| 143 | </pre>
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| 144 | </body>
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| 145 |
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| 146 | </topic>
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