HP J4868A User Manual - Page 13

Introducing the HP Procurve Switch 2124 Introducing the HP Procurve Switch 2124 Switch Operation Overview Forwarding, Filtering, Flooding. When the switch receives a packet, it determines the destination address, and looks for the address in the address table. Based on the port location of that address, the switch then determines whether to forward, filter-out, or flood the packet. I forward - if the destination address is on a different port than the one on which the packet was received, the packet is forwarded to the destination port and on to the destination device. I filter out - if the destination address is on the same port as the one on which the packet was received, the packet is filtered out. The switch thereby isolates local traffic so the rest of the network connected to the switch does not use bandwidth dealing with unnecessary traffic. I flood - whenever a new destination address is found in a packet received on a port, the destination address will not yet be in the switch's address table and the Switch 2124 cannot know whether to forward or filter out the packet. In this case, it sends the packet to all the other switch ports. This is referred to as "flooding". When the destination device receives the packet, it replies, and the switch learns the new address from the reply packet. Then, all future packets destined for that address are forwarded or filtered out appropriately. Network Moves and Changes. When devices are moved in the network, and become connected to a different switch port, the Switch 2124 automatically recognizes the change and updates the address table with the new port location of the device. Communication with the device is automatically maintained, without any address table manipulation being required. 1-7