The various connection type features are supported through the implementation of VMware virtual networks. A virtual network device (for example, /dev/vmnet0) is essentially a virtual Ethernet network that runs completely within a host machine. VMware may start up to four virtual networks, identified as vmnet0 through vmnet3. Any UNIX process can attach to the network.

With the exception of obtaining network numbers, the creation and use of vmnets is completely transparent to users and VMs. You do not define any virtual networks; the VMware application automatically defines and uses them as needed. You need only choose a connection type and complete the network setup as appropriate for each VM.

Whenever you launch the VMware application (whether or not you have started a VM or selected any connection type), VMware application automatically creates one virtual network on the host machine. This network is identified as vmnet0; you can always see this device when VMware application is running.

If you define VMs with various connection types, or if you launch multiple instances of VMware application, you may see more than one virtual network process. vmnets numbered 0 and 1 are reserved by VMware application. If additional networks are required by VMs, they are arbitrarily assigned numbers as they come up, starting with vmnet2. However you never need to refer to a particular virtual network number; their use is totally transparent.

As noted earlier, any UNIX process can attach to a virtual network. This means that you can write applications or utilities that use these virtual networks. You can check the VMware Web site technical pages for examples of such programs (two examples are vnet-sniffer and vnet-rwire) and a description of the interface to the virtual network.

Virtual network 0 is automatically created when the VMware application is installed. It is device /dev/vmnet0 and it is always present, regardless of whether any VM is currently running. vmnet0 is reserved for any VMs using the Bridged connection type. An application called vnet-bridge runs the vmnet0.

Virtual network 1 is automatically created when the VMware application is installed. It is device /dev/vmnet1 and it is always present, regardless of whether any VM is currently running. vmnet1 is reserved for any VMs using the host-only connection type.