Ignoring a frame is called filtering . Copying the frame is called forwarding . The basic type of filtering is keeping local frames local, and sending remote frames to the other subnetwork. Another type of filtering is based on specific source and destination addresses. Both types of filtering provide some control over internetwork traffic and can offer improved security.
Most Ethernet bridges can filter broadcast and multicast frames.
Occasionally, a device will malfunction and continually send out broadcast frames, which are continuously copied around the network. A broadcast storm, as it is called, can bring network performance to zero. If a bridge can filter broadcast frames, a broadcast storm has less opportunity to brew. Today, bridges are also able to filter according to the Network-layer protocol. This blurs the demarcation between bridges and routers.