JNCIS-SP: Juniper Networks Certified Specialist – Service Provider Routing — Question 43

An Ethernet bridge is configured such that all interfaces are in a single broadcast domain. Which two tasks does an Ethernet bridge perform in response to receiving a frame with an unknown unicast destination MAC address? (Choose two.)

Answer options

• A. It drops the frame.
• B. It floods the frame out of all interfaces except the one on which is was received.
• C. It learns the destination MAC address when it sees return traffic from the device.
• D. It learns the source MAC address when it sees return traffic from that device.

Correct answer: B, C

Explanation

The correct answers are B and C because an Ethernet bridge will flood the frame out of all interfaces except the one it was received on when it encounters an unknown destination MAC address, allowing it to reach the intended recipient. Additionally, it learns the destination MAC address when it sees return traffic from the device, which helps in building its MAC address table. Option A is incorrect as the bridge does not drop the frame in this scenario, and option D is also incorrect as learning the source MAC address is not relevant to the unknown unicast frame situation.