isomorphism wrotealso, look for another router...
I bought 2 different tenda routers and they have the same problem with configuration, whenever the electricity fluctuates a bit, the modem is reset. moreover, whenever you connect the router to a dsl modem for example, it will not get the gateway correctly, so you need to put everything static.
Not sure about the router being reset but you can try researching to find out if it has a CMOS , a CMOS is a battery that gives 3V to a circuit board to save some settings for it. as for the gateway, all routers have to be done that.