Method and device for transmitting data

A network gateway unit and method for transmitting data from a first router to a second router through an external communications network, whereby local area networks connected to the router devices can be connected through the network gateway unit, include connecting the first router to the communications network through the network gateway unit. The network gateway unit is used for conversion between a transmission protocol used by the first router and a transmission protocol used in the communications network. A hardware address, which identifies the second router, is allocated to the data as a destination address by the first router. In the network gateway unit, a network address that identifies an exit point from the communications network is allocated to the destination address. Based upon the network address, the data is transmitted to the exit point from the communications network and from there to the second router.