The router (the box that connect to your outside phone or satellite receiver outlet) acts as the DHCP server for the entire network in your house. DHCP server assigns the IP addresses when starts up (power up) to all your devices on the network, typically in the ascending order beginning with 100 or some other base. For example if your network is defined as router=192.168.2.1 (the "Server"), then it will try to assign 192.168.2.100, ...101, ...102 etc for all the other devices called "clients".
It usually remember the pre-existing devices IPs using those devices MAC addresses (MAC address is a sort of a serial number, it's not the same as IP addr) from before power outage, and will try to assign the same IPs to the same devices but it cannot always do that. For example if you added or taken out a device then it may have to renumber the other devices. It depends on the router and it also depends whether the router memory may have been zeroed (reset or corrupt) during the power outage. In my house I had to change routers every now and then especially after a lighting storm because they just blow (hardware breaks) and failed to work normally or work sort of but not quite the same as before. Especially their WiFi wireless part is vulnerable, but also long Ethernet cables tend to have high voltage spikes propagating during storms, especially if the wiring is vertical between floors. I have used probably 5 different routers in the last 10 years because they all would break sooner or later.
If your network has a working DHCP server then it does not really matter what IP is assigned to the SP3 because you can always call it by the Netbios name, that is
http://sp3-serialnumber You have a choice of setting the SP3 also not to accept the IP served to it by the router, by setting the MISC-->DHCP option to Static. Then set the IP address in the same screen to what it is supposed to be for example 192.168.2.123
Then it will always be 123 but you probably won't be able to address it by the SP3 serial number but you would have to type
http://192.168.2.123A prefered method of configuring the home LAN is to set the router as the DHCP Server, and enable all other devices and PC's on the network to use DHCP Client or just "DHCP", rather than using the Static IP method. Most devices and PC's use the term "DHCP" and "DHCP Client" interchangeably, means the same thing. The Static IP method is the rescue measure of the last resort because it can lead to IP clash with multiple devices and confusion, when you add new devices, but it is also the one method which will always work.
Stan
Bryston