6 Virtual networking
VirtualBox has limited support for so-called jumbo frames, i.e. networking packets with more than 1500 bytes of data, provided that you use the Intel card virtualiza- tion and bridged networking. In other words, jumbo frames are not supported in NAT mode or with the AMD networking devices; in those cases, jumbo packets will silently be dropped for both the transmit and the receive direction. Guest operating systems trying to use this feature will observe this as a packet loss, which may lead to unex- pected application behavior in the guest. This does not cause problems with guest operating systems in their default configuration, as jumbo frames need to be explicitly enabled.
6.2 Introduction to networking modes
Each of the eight networking adapters can be separately configured to operate in one of the following five modes:
•Not attached
•Network Address Translation (NAT)
•Bridged networking
•Internal networking
•Host-only networking
By default, virtual network cards are set up to use network address translation, which is well suited to standard networking needs (accessing the Internet from programs running in the guest and providing network services for machines in a local intranet). In particular, if all you want is to browse the Web, download files and view e-mail inside the guest, then the default configuration of the NAT network should be sufficient for you, and you can safely skip the rest of this section. Please note that the ping utility does not work over NAT, and that there are certain limitations when using Windows file sharing (see chapter 6.4.3, NAT limitations, page 85 for details).
For advanced networking needs such as network simulations, bridged networking can be used to set up an additional, software based network interface on the host to which the virtual machine is connected.
VirtualBox internal networking can be used to create a virtual network which is visible to selected virtual machines, but not to applications running on the host or to the outside world.
Finally, host-only networking can be used to create a network containing the host and a set of virtual machines, without the need for the host’s physical network interface. Instead, a virtual network interface (similar to a loopback interface) is created on the host, providing connectivity among virtual machines and the host.
The following sections describe the available network modes in more detail.
