hi, when a switch recive a packet to a unknown destination, the switch flood it on every port. That normal.
You can show the mac-address-table of the switch: if the destination IP of the packet isn't present, that mean the switch can't know the correct MAC address of the next hop, so flood.
The mac-address-table is dynamic, so as soon as the switch "learn" the correct association MAC-IP that will be populate of entry, so no other flood on know MAC-IP related.
But if that behaviour happen also in other situation, that will originate a problem of duplicated packet.
Only in this case it's a layer2 problem, you can identify it by a packet sniffer, sniffing the packets near the destination. It depend on a uncorrect design of the network, or by the use of a underperformer switch, or be malicious. Bye
http://en.wikipedia.org/wiki/Unicast_flood
