Last night my internet is quite bad and I cannot connect to wifi, so I turn the router off then on again, but that didn't work so I use my mobile connection and go to sleep.
Today my wifi had turn to the default settings. My ISP give me PPPoE login details and put them in. Things works again.
So, will turn it on/off erase those info like PPPoE and wifi settings? I've done this hundreds times before but never have this problem.