3Com AccessBuilder 500, User Manual

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P P E N D I X
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R I D G I N G A N D
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O U T I N G
Bridging and Routing Concepts
A bridge connects one or more LANs together. It examines each data
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 networks 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.
Guidelines For Choosing Bridging or Routing
The list below outlines some of the reasons why you might choose to
configure the AccessBuilder 500 as a bridge or a router. Read through
the rest of this appendix for more explanation and to help decide
which of the above conditions apply to your network.
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A bridge is simpler to configure but a router can provide more security on
a busy network and filter unwanted data transmissions more effectively.
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If your network consists of only one or two links between different sites
and your network is not heavily loaded, in most circumstances you can
configure your AccessBuilder 500 units as bridges.
■
If your network structure is complicated and consists of a mixture of
leased line and ISDN links, or if it uses several different protocols, you
may obtain better performance from the AccessBuilder 500 units if you
configure them as routers.
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If you are connecting to a routed corporate network that is already running
IP and/or IPX protocols or if you are using the AccessBuilder 500 to
connect to the Internet you must configure the unit as a router.