What action does a switch take if the destination MAC address is unknown?

What action does a switch take if the destination MAC address is unknown?
A . Discard frame
B . Send ICMP unreachable message to source
C . Flood packet on all ports
D . Compare destination IP address against an ACL to determine if it is permitted
E . Send gratuitous ARP on all ports and wait for reply before forwarding

Answer: C

Explanation:

"What happens though when the switch receives a frame with a destination MAC address that is not included in the table? In that case the switch will just broadcast/flood the frame with the unknown destination address to all of its ports (apart from the port where the frame came from). This process is called unknown unicast flooding. " http://telconotes.wordpress.com/2013/03/09/how-a-switch-works/