The exhibit displays the MAC address table of a switch in your network, along with the location of each device
connected to the switch.

Which of the following frames will cause the switch to add a new MAC address to its table and forward the
frame to all ports when the frame is received?

A.
source MAC: 12-34-56-78-9A-BC, destination MAC: ff-ff-ff-ff-ff-ff

B.
source MAC: ff-ff-ff-ff-ff, destination MAC: 12-34-56-78-9A-BC

C.
source MAC: 12-34-56-78-9A-BF, destination MAC: 12-34-56-78-9A-BC

D.
source MAC: 12-34-56-78-9A-BC, destination MAC: 12-34-56-78-9A-BF

Explanation:
The only frame that will be handled in the specified way is the one with a source MAC of 12-34-56-78-9A-BC
and a destination MAC of ff-ff-ff-ff-ff-ff. Since the source address 12-34-56-78-9A-BC is not already in the MAC
table, the switch will add it. It will forward the frame to all ports because the destination is the broadcast MAC
address of ff-ff-ff-ff-ff-ff.
A frame with a source MAC of ff-ff-ff-ff-ff-ff and a destination MAC of 12-34-56-78-9A-BC is an impossible
combination. That would mean that the frame is coming from all devices, which is not possible.
The frame with a source MAC of 12-34-56-78-9A-BF and a destination MAC of 12-34-56-78-9A-BC would be
sent to all ports because the destination MAC address is not in the MAC address table. However, the switch
would not add a new MAC address to the table because the source address is already in the table.
The frame with a source MAC of 12-34-56-78-9A-BC and a destination MAC of 12-34-56-78-9A-BF would not
be forwarded to all ports because the destination MAC address is in the table. The switch would add a new
MAC address to the table because the source MAC address is not currently in the MAC address table.
Objective:
LAN Switching Fundamentals
Sub-Objective:
Interpret Ethernet frame format

Cisco Press > Articles > Cisco Certification > CCNA Routing and Switching > Basic Data Transmission in
Networks: MAC Tables and ARP Tables
How do Switches Work?