3Com AccessBuilder 500 User Manual

Contents

3Com AccessBuilder 500 User Manual Manual pdf 74 page image

A-2 APPENDIX A: BRIDGING AND ROUTINGBridging and Routing ConceptsA bridge connects one or more LANs together. It examines each dataframe received at a LAN port and forwards any frames that it assumes arefor a destination device not connected to that LAN port. The bridge is ableto do this by learning which devices are connected to each LAN port.A router learns much more about the networks connected to it and isable to be much more selective about the data it passes on to othernetworks and to which networks it transmits. By default routers reject orfilter data unless it matches predefined attributes (for example specificprotocols or destination network addresses). In large interconnectednetworks a router selects the best route for data to travel.Guidelines For Choosing Bridging or RoutingThe list below outlines some of the reasons why you might choose toconfigure the AccessBuilder 500 as a bridge or a router. Read throughthe rest of this appendix for more explanation and to help decidewhich of the above conditions apply to your network.n A bridge is simpler to configure but a router can provide more security ona busy network and filter unwanted data transmissions more effectively.n If your network consists of only one or two links between different sitesand your network is not heavily loaded, in most circumstances you canconfigure your AccessBuilder 500 units as bridges.n If your network structure is complicated and consists of a mixture ofleased line and ISDN links, or if it uses several different protocols, youmay obtain better performance from the AccessBuilder 500 units if youconfigure them as routers.n If you are connecting to a routed corporate network that is already runningIP and/or IPX protocols or if you are using the AccessBuilder 500 toconnect to the Internet you must configure the unit as a router.