| 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_internal">
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| 4 | <title>Internal Networking</title>
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| 5 |
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| 6 | <body>
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| 7 | <p>
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| 8 | Internal Networking is similar to bridged networking in that the
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| 9 | VM can directly communicate with the outside world. However, the
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| 10 | outside world is limited to other VMs on the same host which
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| 11 | connect to the same internal network.
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| 12 | </p>
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| 13 | <p>
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| 14 | Even though technically, everything that can be done using
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| 15 | internal networking can also be done using bridged networking,
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| 16 | there are security advantages with internal networking. In bridged
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| 17 | networking mode, all traffic goes through a physical interface of
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| 18 | the host system. It is therefore possible to attach a packet
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| 19 | sniffer such as Wireshark to the host interface and log all
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| 20 | traffic that goes over it. If, for any reason, you prefer two or
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| 21 | more VMs on the same machine to communicate privately, hiding
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| 22 | their data from both the host system and the user, bridged
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| 23 | networking therefore is not an option.
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| 24 | </p>
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| 25 | <p>
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| 26 | Internal networks are created automatically as needed. There is no
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| 27 | central configuration. Every internal network is identified simply
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| 28 | by its name. Once there is more than one active virtual network
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| 29 | card with the same internal network ID, the Oracle VM VirtualBox support
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| 30 | driver will automatically <i>wire</i> the cards and
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| 31 | act as a network switch. The Oracle VM VirtualBox support driver
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| 32 | implements a complete Ethernet switch and supports both
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| 33 | broadcast/multicast frames and promiscuous mode.
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| 34 | </p>
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| 35 | <p>
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| 36 | In order to attach a VM's network card to an internal network, set
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| 37 | its networking mode to Internal Networking. There are two ways to
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| 38 | accomplish this:
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| 39 | </p>
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| 40 | <ul>
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| 41 | <li>
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| 42 | <p>
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| 43 | Use the VM's <b outputclass="bold">Settings</b> window
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| 44 | in VirtualBox Manager. In the <b outputclass="bold">Network</b>
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| 45 | category of the Settings window, select
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| 46 | <b outputclass="bold">Internal Network</b> from the
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| 47 | drop-down list of networking modes. Select the name of an
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| 48 | existing internal network from the drop-down list below, or
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| 49 | enter a new name into the
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| 50 | <b outputclass="bold">Name</b> field.
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| 51 | </p>
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| 52 | </li>
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| 53 | <li>
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| 54 | <p>
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| 55 | Use the command line, for example:
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| 56 | </p>
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| 57 | <pre xml:space="preserve">VBoxManage modifyvm "VM name" --nic<x> intnet</pre>
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| 58 | <p>
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| 59 | Optionally, you can specify a network name with the command:
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| 60 | </p>
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| 61 | <pre xml:space="preserve">VBoxManage modifyvm "VM name" --intnet<x> "network name"</pre>
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| 62 | <p>
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| 63 | If you do not specify a network name, the network card will be
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| 64 | attached to the network <codeph>intnet</codeph> by default.
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| 65 | </p>
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| 66 | </li>
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| 67 | </ul>
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| 68 | <p>
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| 69 | Unless you configure the virtual network cards in the guest
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| 70 | operating systems that are participating in the internal network
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| 71 | to use static IP addresses, you may want to use the DHCP server
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| 72 | that is built into Oracle VM VirtualBox to manage IP addresses for the
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| 73 | internal network. See <xref href="man_VBoxManage-dhcpserver.dita#vboxmanage-dhcpserver"/>.
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| 74 | </p>
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| 75 | <p>
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| 76 | As a security measure, by default, the Linux implementation of
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| 77 | internal networking only allows VMs running under the same user ID
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| 78 | to establish an internal network. However, it is possible to
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| 79 | create a shared internal networking interface, accessible by users
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| 80 | with different user IDs.
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| 81 | </p>
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| 82 | </body>
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| 83 |
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| 84 | </topic>
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