sorry for bad english. I'm using Ubuntu 14.04 64 bit and I have a strange internet connection problem. When I'm at work I can access internet via DHCP wireless and wired without problems. When I'm at home with wireless connection or when I use tethering hotspot with my mobile phone I cant connect internet using DHCP. The only way to connect internet is to set manually the DNS (188.8.131.52) in Network Manager. Why? With Ubuntu 12.04 I've never set DNS on DHCP and it worked fine... Thank you.
From the fact that your system connects at work via wired and wireless shows that your system works, and that the system at work is configured correctly. The failure of home wireless and "tethering hotspot" means that your home wireless router (and whatever you connect to with your phone) are not configured to share DNS information when you connect. You can fix this problem by accessing your home router configuration, and finding DHCP settings. You could use
wireshark on Linux to monitor packets both as you connect at work, and fail to connect at home.