| Bridge Protocol Data Units. | |
| Bridge Protocol Data Units (BPDUs) frames contain information regarding the switch ID, originating switch port, MAC address, switch port priority, switch port cost, etc. Bridge Protocol Data Units frames are sent out as multicast messages regulary at multicast destination MAC address 01:80:c2:00:00:00 When Bridge Protocol Units are received, the swtich uses a mathematical formula called the spanning tree algorythm (STA) to know when there is a layer 2 switch loop in the network and determines which of the redundant ports needs to be shut down. Three types of Bridge Protocol Data Units: -Configuration BPDU (CBPDU) -Topology Change Notification (TCN) BPDU -Topology Change Notification Acknowledgement (TCA) | data |
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