When an Ethernet frame is sent out an interface, the destination MAC address indicates:

The destination MAC address in an Ethernet frame indicates the specific device on the network to which the data is being sent.

Here's a step-by-step explanation:

1. When a device needs to send data to another device over a network, it first encapsulates the data in an Ethernet frame.

2. This Ethernet frame contains several pieces of information, including the source MAC address (the address of the device sending the data) and the destination MAC address (the address of the device to which the data is being sent).

3. The destination MAC address is used by network switches to direct the Ethernet frame to the correct device.

4. The switch looks at the destination MAC address and forwards the frame out of the specific port that leads to the destination device.

5. The destination device then receives the Ethernet frame, decapsulates the data, and processes it.

So, in summary, the destination MAC address in an Ethernet frame indicates the specific device on the network that should receive the data contained in the frame.