Forwarding and filtering
The bridge makes data forwarding or filtering decisions based on the following scenarios:
As shown in Figure 105, when Host A sends an Ethernet frame to Host C, the bridge searches its bridge table and finds out Host C is attached to bridge interface 2, and forwards the Ethernet frame out of bridge interface 2.
Figure 105: Forwarding
As shown in Figure 106, when Host A sends an Ethernet frame to Host B, as Host B is on the same LAN segment as Host A, the bridge filters the Ethernet frame instead of forwarding it.
Figure 106: Filtering
As shown in Figure 107, when Host A sends an Ethernet frame to Host C, if the bridge does not find a MAC-to-interface mapping about Host C in its bridge table, the bridge forwards the Ethernet frame to all interfaces except the interface on which the frame was received.
Figure 107: The proper MAC-to-interface mapping is not found in the bridge table
When a bridge receives a broadcast or multicast frame, it forwards the frame to all interfaces other than the receiving interface.