a gateway connects incompatible networks at the fourth through seventh layer of the OSI model by using prtocol conversion and routing services. Gateways translate one prtocol into another, so that the workstation can carry fewer protocol stacks. this simplifies routing requiremtns. speciallized systems are set up to act as gateways, specific to the type of network supported and the protocols needed. gateways include both hardware and software.

a router is an example of a gateway

like for example, if you have dsl or cable internet at home, there's ususally a modem, well that modem can your your gateway to the internet.

for example, if you have windows computer, go to the DOS command and type: ipconfig you will see something like this: 

Microsoft Windows [Version 5.2.3790]
(C) Copyright 1985-2003 Microsoft Corp.

C:Documents and SettingsAdministrator>ipconfig

Windows IP Configuration


Ethernet adapter Local Area Connection 2:

   Connection-specific DNS Suffix  . :
   IP Address. . . . . . . . . . . . : 192.168.1.102
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Default Gateway . . . . . . . . . : 192.168.1.1

Ethernet adapter Local Area Connection:

   Media State . . . . . . . . . . . : Media disconnected

C:Documents and SettingsAdministrator>


as you can see, my gateway is 192.168.1.1 which is the ip address of my wireless router at home