Unicast Frame Forwarding on a Switch: Exam 200-125 Cisco Certified Network Associate Exam

Unicast Frame Forwarding on a Switch

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Which statement about unicast frame forwarding on a switch is true?



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A. B. C. D.


Unicast frame forwarding on a switch involves the process of forwarding frames to a single destination device based on its MAC address.

A. The TCAM table (Ternary Content-Addressable Memory) stores information about access control lists (ACLs) and is used for hardware-based packet processing to enable fast lookup and matching of packets against ACLs. While it may contain MAC addresses as part of the ACLs, it is not directly involved in unicast frame forwarding.

B. If the destination MAC address is unknown to the switch, the frame is flooded to every port that is configured in the same VLAN except on the port that it was received on. This is known as broadcast flooding. The reason for this is that the switch does not know the location of the destination device and needs to send the frame to all possible devices within the same VLAN in order to ensure that it reaches the intended destination. This can cause unnecessary network congestion and is why it is important to minimize the occurrence of unknown unicast traffic on the network.

C. The CAM table (Content-Addressable Memory) is used to store the MAC addresses of devices that have communicated with the switch. It is used to quickly lookup the MAC address of the destination device to determine which switch port it is connected to. If the destination MAC address is found in the CAM table, the frame is forwarded only to the specific port associated with that MAC address. If the destination MAC address is not found in the CAM table, the switch will flood the frame as described in option B.

D. The source address is used to determine the switch port to which a frame was received. When a frame enters a switch port, the switch examines the source MAC address in the frame header and updates the CAM table with the port number and MAC address. This allows the switch to quickly determine the port to which frames should be forwarded based on their destination MAC address.

Therefore, the correct answer is option C.