Which Tasks Does an Ethernet Bridge Perform in Response to Receiving a Multicast Frame?
Question
By default, which two tasks does an Ethernet bridge perform in response to receiving a multicast frame? (Choose two.)
Answers
Explanations
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A. B. C. D.AC
Multicast packets are flooded out all ports except for the port on which it was received. When an unknown destination responds to traffic that has been flooded through a switch, the switch learns the MAC address fo that node and updates its bridge table with the source MAC address and ingress port.
Ethernet bridges operate at the data link layer (Layer 2) of the OSI model and are responsible for forwarding Ethernet frames between network segments. One of the functions of an Ethernet bridge is to handle multicast traffic, which is traffic sent from one source to multiple destinations.
When an Ethernet bridge receives a multicast frame, it performs the following two tasks by default:
It floods the frame out of all interfaces except the one on which it was received: The bridge does not have a way to know which port leads to the destination host, so it sends the frame out of all ports except the one where it received the frame. This behavior is known as flooding, and it ensures that the multicast traffic reaches all nodes on the network segment.
It learns the MAC address of any responding nodes and updates its bridge table with the source MAC address and ingress port: After the multicast frame is sent out of all interfaces, the bridge listens for responses from the network nodes. When it receives a response, it learns the MAC address of the responding node and updates its bridge table with the source MAC address and the ingress port where the frame was received. This information allows the bridge to forward future unicast traffic directly to the destination node without flooding the network.
Answer A and C are the correct answers.
Option B, dropping the frame, is not a valid option since it would prevent the multicast traffic from reaching its intended destination.
Option D, flooding the frame out of particular interfaces based on its multicast MAC table, is also not the default behavior of an Ethernet bridge. While some switches may use a multicast MAC table to optimize multicast traffic forwarding, the default behavior of an Ethernet bridge is to flood the multicast frame out of all interfaces except the one on which it was received, and then learn the MAC address of responding nodes.
