A DHCP reservation is a feature that allows a DHCP server to assign a specific IP address to a specific device on a network, based on its MAC address. This ensures that the device always receives the same IP address, even if it is disconnected or rebooted. A DHCP reservation is most likely applied to a printer, as it can make it easier for users to find and connect to the printer on the network, without having to change the printer settings or deal with IP address conflicts.