for a device on your local network. You give it a static address. This is generally done by some application/utility within the operating system. In order to do this in such a way as to avoid conflicts with DHCP addressing, you enter your DHCP server's (usually your router) web interface and set some range of addresses to be reserved for that purpose. If you don't do that and the device you've given a static address has been turned off or the lease has expired, your DHCP server sees that address as "fair game" and may give it away. On a smaller home LAN...and if you can't get into your router's web interface, you can try to set that static address very high and hope to get away with it. You still need to know the gateway address in order to determine where to begin. The gateway is usually the same address used when you configure your router through a web browser.