A computer located on one network segment
that is trying to talk to another computer on a different segment
(that is, across the router) sends the data through a default gateway.
The default gateway is the "near side" interface of the
router, the interface on the router to which the local computer's
network segment or wire is attached. In order for each computer to
recognize its default gateway, the corresponding near side router
interface IP address has to be entered into the host Internet Protocol
(TCP/IP) Properties Dialog Box.
This
information is stored in the computer driver software for the NIC.