Bridge Tasks for Unknown Unicast MAC Addresses
Question
An Ethernet bridge is configured such that all interfaces are in a single broadcast domain. Which two tasks does the bridge perform in response to receiving a frame with an unknown unicast destination MAC address? (Choose two.)
Answers
Explanations
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A. B. C. D.BD
An Ethernet bridge is a networking device that connects multiple network segments together and forwards traffic between them based on the destination MAC address. In this scenario, all interfaces of the bridge are in a single broadcast domain, which means that any broadcast or multicast traffic sent on one interface will be received by all other interfaces.
When the bridge receives a frame with an unknown unicast destination MAC address (i.e., a MAC address that is not already in the bridge's MAC address table), it must decide what to do with the frame. The two possible actions are:
A. Drop the frame: This means that the bridge will discard the frame and take no further action. This is the default behavior of many bridges and is often used in security-conscious environments to prevent unknown or unauthorized devices from communicating on the network.
B. Flood the frame out of all interfaces except the one on which it was received: This means that the bridge will forward the frame out of all interfaces except the one on which it was received. This is also known as broadcast forwarding and is used when the bridge does not know the location of the destination device. By flooding the frame, the bridge ensures that it reaches all devices on the network and that the destination device can respond and update the bridge's MAC address table.
C. Learn the destination MAC address: If the bridge decides to flood the frame, it will also learn the destination MAC address by adding it to its MAC address table. This allows the bridge to forward future frames destined for that MAC address directly to the correct interface, rather than flooding them.
D. Learn the source MAC address: Regardless of whether the bridge drops the frame or floods it, it will always learn the source MAC address by adding it to its MAC address table. This allows the bridge to forward future frames from that MAC address directly to the correct interface, rather than flooding them.
In summary, if an Ethernet bridge is configured such that all interfaces are in a single broadcast domain, it will either drop or flood frames with unknown unicast destination MAC addresses, and it will always learn the source MAC address. If it floods the frame, it will also learn the destination MAC address.
