In general, I think that it is best to leave the task of assigning network IP addresses to the main router and have all other devices on the network use DHCP to get their IP addresses from it. In order to ensure that individual non-computer hardware devices are always assigned to consistent IP addresses (which is generally desirable, for lots of reasons), you set up the router to recognize each one's unique MAC address and assign it a specified IP address. Almost all mid- to high-end domestic routers allow this, though they don't all put the facility in an obvious place on their admin menus.