Basic Routing Information
7-1
Chapter 7
Basic Routing Information
This chapter provides an overview of IP networks and routing.
Basic Router Concepts
Large amounts of bandwidth can be provided easily and relatively inexpensively in a local area
network (LAN). However, providing high bandwidth between a local network and the Internet can
be very expensive. Because of this expense, Internet access is usually provided by a slower-speed
wide area network (WAN) link such as ISDN. In order to make the best use of the slower WAN
link, a mechanism must be in place for selecting and transmitting only the data traffic meant for
the Internet. The function of selecting and forwarding this data is performed by a router.
What is a Router?
A router is a device that forwards traffic between networks based on network layer information in
the data and on routing tables maintained by the router. In these routing tables, a router builds up a
logical picture of the overall network by gathering and exchanging information with other routers
in the network. Using this information, it chooses the best path for forwarding network traffic.
Routers vary in performance and scale, number of routing protocols supported, and types of
physical WAN connections supported. The Model RH340 Internet Access ISDN Router is a small
office router that routes the IP protocol over a dial-up ISDN connection.
