3Com 3C840 manual Bridging and Routing, Routing Concepts, Decide, Terrestrial and satellite links

A

BRIDGING AND ROUTING

Introduction	During the initial configuration of the OfficeConnect Remote 840, you
	must decide whether to configure the unit as a bridge or as a router. If
	you are unsure which option you should choose, this section will help you
	decide.
	Bridges and routers are used to connect networks together. The cost of
	connecting networks together is generally proportional to the distance
	over which the network extends and the amount of bandwidth required.
	Large amounts of bandwidth can be provided easily within a LAN by
	connecting different segments together with a local bridge. However, it
	becomes impractical and expensive to extend this bandwidth over larger
	distances, and it is, therefore, usual to interconnect local high-speed
	networks using bridges or routers connecting over slower speed
	terrestrial and satellite links.
	In the following sections we describe the concepts behind bridging and
	routing, and discuss the different ways in which LANs can be configured
	and operated to optimize performance and minimize disruption of traffic
	on each individual LAN.
Bridging and	A bridge connects one or more LANs together. It examines each data
Routing Concepts	frame received at a LAN port and forwards any frames that it assumes are
	for a destination device not connected to that LAN port. The bridge is
	able to do this by learning which devices are connected to each LAN port.
	A router learns much more about the networks connected to it and is
	able to be much more selective about the data it passes on to other
	networks and to which network it transmits. By default routers reject or
	filter data unless it matches predefined attributes (for example, specific
	protocols or destination network addresses). In large interconnected
	networks, a router selects the best route for data to travel.