:Networking 101: Understanding the Data Link Layer
Networking 101: Understanding the Data Link Layer Aug 20, 2008, 23 :04 UTC (5 Talkback[s]) (5891 reads) (Other stories by Charlie Schluting)
"Ethernet switches, as they're called now, began life as a "bridge." Traditional bridges would read all Ethernet frames, and then forward them out every port, except the ones they came in on. They had the ability to allow redundancy via STP, and they also began learning which MAC addresses were on which port. At this point, a bridge then became a learning device, which means they would store a table of all MAC addresses seen on a port. When a frame needed to be sent, the bridge could look up the destination MAC address in the bridge table, and know which port is should be sent out."
