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* '''Network address translation (NAT)''' — One or more virtual machines share the IP and MAC address of the host system for the purposes of communicating with the external network. Virtual machines are able to communicate with other clients on the network to which the host is connected, but will appear to those clients as the host system, rather than as individual network clients. This approach allows multiple virtual machines to operate using a single IP address. IP addresses are allocated dynamically to NAT based virtual machines by VMware Server's internal DHCP server. Communication with the external network can only be established by the virtual machine. It is not, therefore, possible for a client on the external network to initiate a connection with a NAT based virtual machine (although ''port forwarding'' may be configured to allow traffic to a particular port, such as HTTP traffic on port 80,, to be directed to a specific virtual machine).

In a physical network configuration, a switch is typically a hardware device which is used to provide a central point of network connectivity for network clients. The devices on a physical network are connected to a switch using twisted pair cabling. When a client sends a network packet to another device on the network, the switch checks the packet for the MAC address of the destination device and forwards the packet to the port to which that device is connected.

VMware Server includes a virtual network switch which. , although entirely software based, performs the same task as physical switch, in that it allows virtual devices, such as virtual machines and other virtual network components, to be connected together to form a virtual network. According to VMware, Inc., VMware Server 2.0 supports a total of 10 virtual switches on Windows hosts and 255 on Linux hosts. In addition, while virtual switches on Windows hosts can have an unlimited number of ports, Linux based switches are limited to 32 ports per switch.

A list of currently configured networknetworks, and the switches to which they are assigned may viewed via the VI Web Access management interface, by selecting the host system from the ''Inventory'' panel and locating the ''Networks'' panel in the ''Summary '' workspace. The following figure illustrates the ''Networks'' panel with three virtual switches configured:

The switches available by default are the result of choices made during the initial VMware Server installation and configuration process as described in the [[Installing VMware Server 2.0 on Linux Systems]] and [[Installing VMware Server 2.0 on Windows Systems]] chapters of this book. ifIf, for example, ''vmnet8'' is not listed this is most likely due to the fact that NAT was not selected as a network configuration option during the VMware Server installation.

In order to communicate with within the virtual networks, virtual machines need at least one virtual network adapter. Although these are software components running the in the VMware Server environment, they appear as physical hardware devices to the guest operating systems, specifically an AMD PCNet adapter on 32-bit guest operating systems, and an Intel Pro/1000 MT adapter for 64-bit and Windows Vista guests. In each of the network configuration modes (Bridged, HostOnly and NAT), the virtual network adapters connect to a ''virtual network switch'', which in turn connects to other network components such as ''host network adapters'', ''host virtual adapters'' and a ''NAT'' and ''DHCP'' server.

With VMware Server 2 it is possible to configure up to 10 virtual network adapters into on a single virtual machine.

The purpose of a Dynamic Host Configuration Protocol (DHCP) server is to provide IP addresses and other configuration to network clients. When a virtual machine is configured to use bridged networking, it can obtain either obtain an IP address from a DHCP server on the external network, or be assigned a network appropriate static IP address by an administrator. Virtual machines on HostOnly or NAT virtual networks need to be dynamically assigned IP addresses but have no means of communicating directly with an external DHCP server. In order to address this requirement, VMware Server provides its own built in DHCP server which is connected to NAT and HostOnly virtual networks via the corresponding ''virtual network switch''. A virtual machine on a HostOnly virtual network would, therefore, communicate via its ''virtual network adapter'' through the ''virtual network switch'' to the internal DHCP server to obtain a suitable IP address for the HostOnly private subnet.