When you’re using a Virtual Manager like VirtualBox or VMware Player you would like to use that virtual machine as another computer in the LAN or just have internet in it; well these virtualization’s software let you configure this feature providing some types of network interfaces to use in the machine when it’s running.
Here is a comparative table to understand what mean NAT, Bridged adapter, Internal Network and Host-only adapter.
|VM Network Types|
|**Description**||The virtual machine appears as if it was a physical host on the network.||The virtual machine hides behind the IP address of the VMware host. Other VMs in the same NAT (Network Address Translation) network can access it directly.||The virtual machine can only access the VMware host and other VMs in the same host-only network.|
|**IP Address**||The virtual machine requires it's own IP address from the network it is supposed to belong to.||The virtual machine can have any private IP configured on the VMware host.|
|**Accessibility**||Same as a physical host.||Hides behind NAT, so port forwarding on the VMware host required if external access required.||Not accessible from external network unless routed via another VM with access to both external network and the same host-only network.|
|**Use cases**||An always-on server hosted on VMware, or a virtual router or firewall.||Virtual machines intended for testing, or cases when the amount of IP addresses in the external network is limited.||Virtual machines intended for testing with no need to access the network, or VMs which will be protected by a firewall in another virtual machine.|
|Known to have problems with some wireless chipsets especially with Linux, also with Windows Vista.||NAT is really a host-only network with a default gateway (on the VMware host) that routes and NATs.|
In VirtualBox you can easily choose one of these options from the Network option in the Settings of each Virtual Machine listing the available network types from the selector Attached to; additionally you can set an specific network type for each adapter in your computer.