Mark is setting up a small Ethernet network in his home by installing network adapters in three computers running Windows 7 and connecting them to a switch. Mark only uses one of the computers to access the Internet with a dial-up modem, but he wants to be able to access files and his printer from any one of the three systems. After he installs the network interface adapters, he notes that the default networking components have been installed on all three systems, and he sets about configuring their TCP/IP configuration parameters manually. Of the settings on the Internet Protocol Version 4 (TCP/IPv4) Properties sheet, which must Mark configure to provide the network connectivity he desires, and which can he leave blank?