Ethernet switches make their forwarding decision based on what field of the Ethernet frame?

Ethernet switches make their forwarding decisions based on the MAC (Media Access Control) address field of the Ethernet frame. Here are the steps:

1. When a frame arrives at an Ethernet switch, the switch examines the destination MAC address of the frame.

2. The switch then looks up this MAC address in its forwarding table, also known as a MAC address table or CAM (Content Addressable Memory) table.

3. If the switch finds a match in its table, it forwards the frame out of the specific port associated with that MAC address.

4. If the switch doesn't find a match in its table, it floods the frame out of all ports except the one it arrived on. This is known as unknown unicast flooding.

5. The switch also learns from incoming frames. If it doesn't know the source MAC address of an incoming frame, it adds it to its forwarding table, associating it with the port the frame arrived on. This way, the switch builds its knowledge of what MAC addresses are associated with which ports.