A network address translation (NAT) router for connecting an inside network to an outside network. The inside network uses local addresses and has a plurality of voice over Internet protocol (VoIP) systems and a plurality of hosts, and the outside network uses global addresses. An Ethernet driver is connected to Ethernet drivers in the voice over Internet protocol systems by a hub. An Ethernet and Internet protocol (IP) interface module assigns predetermined physical addresses to the Ethernet drivers of the voice over Internet protocol systems. A transmission control protocol/Internet protocol (TCP/IP) module is connected to the Ethernet and Internet protocol interface module and sets a predetermined number of local Internet protocol addresses for the voice over Internet protocol systems. A network address translation module translates an inside local Internet protocol address within a voice over Internet protocol system to a global Internet protocol address.