My ubuntu server 14.04 stops working after week or so. If I reboot it, it starts working again and works for a while but in a week it stops responding to pings and I cannot ssh or anything. If I try to ping it, the server responds "Destination host unreachable.". I know this isn't much information to resolve this problem but I really don't know where to start looking for. Which log file might be recording failures what causes this kind of problem. This might be a HW issue or maybe temperatures cause my server did this same thing before I reinstalled ubuntu.