A device on a TCP/IP internetwork that can forward Internet Protocol (IP) packets to another network, usually a router. In an internetwork, a given subnet might have several router interfaces that connect it to other, remote subnets. One of these router interfaces is usually selected as the default gateway of the local subnet.
When a host on the network wants to send a packet to a destination subnet, it consults its internal routing table to determine whether it knows which router to forward the packet to in order to have it reach the destination subnet.
If the routing table does not contain any routing information about the destination subnet, the packet is forwarded to the default gateway (one of the routers with an interface on the local subnet).
The host assumes that the default gateway knows what to do with any packets that the host itself does not know how to forward.
Graphic D-13. Default gateway.
When configuring a client machine on a TCP/IP internetwork, the client must know the IP address of the default gateway for its network.
On Microsoft Windows NT, Windows 95, and Windows 98 clients, you configure this information on the TCP/IP property sheet for the client. The property to configure is called the Default Gateway Address.
In Windows 2000, you can have a default gateway assigned automatically using Dynamic Host Configuration Protocol (DHCP).