CCNA Practice Exam Test Sample – Question 33

Refer to the exhibit.
q33-q

Switch-1 needs to send data to a host with a MAC address of 00b0.d056.efa4. What will Switch-1 do with this data?

A. Switch-1 will drop the data because it does not have an entry for that MAC address.
B. Switch-1 will flood the data out all of its ports except the port from which the data originated.
C. Switch-1 will send an ARP request out all its ports except the port from which the data originated.
D. Switch-1 will forward the data to its default gateway.

Correct Answer: B
Section: LAN Switching Technologies

Explanation:
This question tests the operating principles of the Layer 2 switch. Check the MAC address table of Switch1 and find that the MAC address of the host does not exist in the table.
Switch1 will flood the data out all of its ports except the port from which the data originated to determine which port the host is located in.

Switches work as follows:
– Switches learn the MAC addresses of PCs or workstations that are connected to their switch ports by examining the source address of frames that are received on that port.
– Machines may have been removed from a port, turned off, or moved to another port on the same switch or a different switch.
– This could cause confusion in frame forwarding.
– The MAC address entry is automatically discarded or aged out after 300 seconds
– If there is not MAC address of destination host in MAC table, switch sends broadcast to all ports except the source to find out the destination host.
In output there is no MAC address of give host so switch floods to all ports except the source port.