A basic Ethernet switch uses a frame's source address for learning and its destination address for forwarding decisions. Mixing those two jobs is a common reason to miss CCNA MAC address table practice questions.
Begin with an empty table
Imagine an original lab exercise with three access ports in VLAN 10. Host A connects to port 1, Host B to port 2, and Host C to port 3. All three ports are forwarding, and the switch's dynamic MAC table is initially empty.
Host A sends a unicast frame addressed to Host B. The switch learns A's source MAC address on port 1 in VLAN 10. It does not yet have B's destination MAC address in the table, so it floods the frame out ports 2 and 3, the other forwarding ports in VLAN 10.
The switch does not send that frame back through port 1. A port belonging only to another VLAN is also outside the flood scope in this ordinary access-switch example.
Watch what the reply teaches
When B replies through port 2, the switch learns B's source address there. It already knows A's destination address is on port 1, so it forwards the reply only toward A.
A later frame from A to B can now be forwarded to port 2 without the same unknown-unicast flooding. Learning happened because B transmitted a frame, not because the switch magically read B's identity from A's destination field.
Use the CCNA switching practice questions to test this sequence with different starting tables. A question where B is already learned should produce a different first forwarding decision from an otherwise identical question with an empty table.
Unknown unicast is not a broadcast address
A frame can have a unicast destination and still be flooded because the switch does not know where that destination is. Flooding describes the forwarding action; broadcast describes a destination category. They are related ideas, but they are not interchangeable labels.
Cisco's explanation of unicast flooding describes the missing-destination-table condition and VLAN boundary. Real switches can apply additional protections and features, so use the conditions supplied in a practice problem.
A three-question answer routine
Before looking at the options, ask: What source address is learned? Is the destination already known in this VLAN? Which forwarding ports are eligible for the resulting action?
The CCNA switching study guide can help connect this sequence with VLANs and loop prevention. Draw the table after each frame rather than trying to imagine the whole exchange at once; the small intermediate table often makes the correct answer obvious.