Bridge records arrival port of unknown destination address frame and suppresses flooding if mores frames to that destination arrive on different ports

摘要

Layer 2 switches/bridges (eg Ethernet) record source MAC addresses of received frames with ingress ports in a MAC table 48. Destination addresses of incoming frames are checked against this table 44. if an address is found the frame is forwarded to the corresponding port 56. If no match is found the frame will be flood/broadcast to all ports except the ingress one. Where the network includes loops this flooding operation can lead to a broadcast storm which congests the network. When the invention fails to find a destination address in the MAC table 50, it records the ingress port and destination address instead in the MAC table, along with flag DC 52. The invention then looks for the flag with all destination address checks, if found the ingress port of the new frame is compared with that in the table 58. If they match flooding occurs normally 62/64. Otherwise the packet is dropped 60.