CCNA: Cisco Certified Network Associate — Question 6

What is the default behavior of a Layer 2 switch when a frame with an unknown destination MAC address is received?

Answer options

• A. The Layer 2 switch forwards the packet and adds the destination MAC address to its MAC address table.
• B. The Layer 2 switch sends a copy of a packet to CPU for destination MAC address learning.
• C. The Layer 2 switch floods packets to all ports except the receiving port in the given VLAN.
• D. The Layer 2 switch drops the received frame.

Correct answer: C

Explanation

The correct answer is C because when a Layer 2 switch receives a frame with an unknown MAC address, it floods the frame to all ports in the same VLAN except the one it came from to locate the destination. Option A is incorrect as it only adds known addresses to the MAC table, and B is not the default behavior. Option D is wrong because the switch does not drop frames with unknown addresses; it attempts to forward them.