You can hardcode an OBI IP address that is not in use and protect it yourself by not assigning it to any other device. Assume for this discussion that your router uses 1.9.168.1.x where x is 1..255.
If your router says that it supplies DHCP addresses beginning at 100, then192.168.1.100 and up (to the DHCP limit) are assigned by the router to devices that do not have an IP and ask for one. There is an exception, explained in a minute.
So if you wanted to to assign a number that you like, such as 77, you could tell the OBI that it has a fixed IP of 192.168.1.77 and you would not assign that number to any other device.
In this example, hardcoding a fixed IP address in the OBI may require you to reconfigure it should you move it to another network somewhere which does not use the 192.168.1 subnet.
The second way t oconfigure the Obi IP is to use the DHCP. many routers allow you to take the MAC address (the hex grouping on the bottom of the OBI) and enter it along with an IP address that DHCP would assign whenever the OBI boots. No other device would get that address. With this configuration, only your local router is configured to assign an address to the OBI. If you were to take it to a friends house, you would have to choose one of these two options for his network (and his might be 192.168.0.x [0 instead of 1 in the 3rd octet]).
Once you know the IP address of the OBI is not going to change on a particular network, you can assign that IP or MAC to have priority for Quality Of Service QOS.
