Save the configuration to the boot floppy (through the LEAF backup menu entry) and reboot. Connect the bridge into the network between the gateway and the LAN. During reboot, the system should show a message similar to:
Bridge firewalling enabled Eth2 (port 3) entering promiscuous mode. Eth1 (port 2) entering promiscuous mode. Eth0 (port 1) entering promiscuous mode. Eth2 (port 3) entering listening mode. Eth1 (port 2) entering listening mode. Eth0 (port 1) entering listening mode. Bridge (MAXWAIT 32 Seconds) Eth2 (port 3) entering listening mode. Eth1 (port 2) entering listening mode. Eth0 (port 1) entering listening mode. Topology change detected. Topology change propogated.
Try to ping the gateway from any system. If the ping goes thro' well, the bridge is working properly. If not, check the cables and the type of cable used. If a straight cable is used between the Bering box and the router, switch it for a crossed cable and try the ping.
Try the command ip li sh and a device called br0 should show up with the ip configured.
The bridge to router cable would need to be a straight cat5 cable as switch to router would normally be a crossed cable. It would do good to have a straight and a crossed cable handy so that both can be tried out.