- NetComm Modem Router User Guide

YML717 Rev1 NetComm NB5 Ethernet/USB Modem Router
www.netcomm.com.au 75
What is a Gateway?
The Internet is so large that a single network cannot handle all of the traffic and still deliver a
reasonable level of service. To overcome this limitation, the network is broken down into smaller
segments or subnets that can deliver good performance for the stations attached to that segment.
This segmentation solves the problem of supporting a large number of stations, but introduces the
problem of getting traffic from one subnet to another.
To accomplish this, devices called routers or gateways are placed between segments. If a machine
wishes to contact another device on the same segment, it transmits to that station directly using a
simple discovery technique. If the target station does not exist on the same segment as the source
station, then the source actually has no idea how to get to the target.
One of the configuration parameters transmitted to each network device is its default gateway. This
address is configured by the network administrators and it informs each personal computer or other
network device where to send data if the target station does not reside on the same subnet as the
source. If your machine can reach all stations on the same subnet (usually a building or a sector
within a building), but cannot communicate outside of this area, it is usually because of an incor-
rectly configured default gateway.