To what destination address will a host send an ARP request if the ARP cache has no mapping entries?

When a host needs to communicate with another device on the same local network but does not have the MAC address stored in its ARP cache, it sends out an ARP (Address Resolution Protocol) request. This request is broadcast to all devices on that local network segment to discover the MAC address associated with the IP address of the desired destination.

The use of the broadcast MAC address is crucial here because it ensures that all potential recipients on the local network receive the ARP request. All devices on the local segment will see the broadcast message, allowing the device with the matching IP address to reply with its MAC address. This mechanism is essential for IP-to-MAC address resolution so that data packets can be correctly directed within the same local network.

In contrast, other options would not serve the purpose of discovering a MAC address for an IP address. The loopback address is used for internal communication within the same host, while the local IP address refers to the host’s own address. The private MAC address is not a standard term in the context of ARP requests and doesn’t apply here. Therefore, the correct choice for the destination address for an ARP request is the broadcast MAC address.