When an IP host sends out an ARP request, what type of address does it expect in return?

When an IP host sends out an ARP (Address Resolution Protocol) request, it is fundamentally looking to discover the MAC (Media Access Control) address corresponding to a specific IP address on the same local network. The ARP request includes the sender's IP address and MAC address, as well as the target's IP address for which it seeks to find the associated MAC address.

The purpose of ARP is to map an IP address to a MAC address, which is crucial for network communication at the data link layer. When the target host receives the ARP request, it responds with an ARP reply that contains its MAC address, thus allowing the requesting host to encapsulate its data in Ethernet frames and successfully communicate with the target.

In this scenario, while other aspects like the VLAN ID, IP address, and subnet mask relate to the operation of a network, the specific nature of the ARP protocol involves resolving an IP address to a MAC address. Therefore, the key detail is that the IP host expects a MAC address in return from its ARP request.