Cabletron Systems CSX100 series, User Manual, Page: 109 / 153

Router Feature Descriptions 95
LANs. Routing extends the reach of networks beyond the limits of each LAN
segment.
Bridging and Routing
The Router can operate as a bridge, as a router, or as both (sometimes called a
brouter). The router will operate as a router for network protocols that are
supported when routing is enabled. The router will operate as a bridge when
bridging is enabled. When both bridging and routing are enabled, routing
takes precedence over bridging; i.e., the router uses the packet’s protocol
address information to route the packet; if the protocol is not supported, the
router will use the MAC address information to bridge the packet.
Operation of the Router is influenced by routing and bridging controls and
filters set during router configuration as well as automatic spoofing and
filtering performed by the router. General IP or IPX routing, and routing or
bridging from/to specific remote routers are controls set during the
configuration process.
Spoofing and filtering, which minimize the number of packets that flow
across the WAN, are performed automatically by the router. For example,
RIP routing packets and certain NetBEUI packets are spoofed even if only
bridging is enabled. For more detailed information on packet routing and
bridging, refer to the section
Routing and Bridging Operation in the
Command Line Interface guide.
IEEE 802.1D Bridging
The Router supports the IEEE 802.1D standard for LAN to LAN bridging.
Bridging is provided over PPP as well as adjacent LAN ports. The bridging
software uses transparent bridging. Configured as a bridge, the unit bridges
data packets to the destination, regardless of the network protocols used.
Also included is the Spanning Tree Protocol allowing the Router to
interoperate with other vendors’ bridge/routers. This is a learning bridge;
i.e., the bridge builds and updates an address table with each MAC source
address and associated information when the packets are received.