Our DHCP server plays some sort of Russian roulette right now: Due to the expansion of our dormitory, we have too less IPv4 addresses for all users right now. So we can't assign one address per host. You will randomly experience, that you can't connect to the internet, even if authentication succeeds. Between ~20:00 and ~24:00 every day there are a small number of people which won't be able to connect to the network. The first steps to solve this problem are already done and further will follow. If you want to help others while you don't need internet, you can unplug / switch off you router and devices.