Today, I use Ubuntu in Tokyo donut,Yangon. I try to update but I can't.It connect to 192.168.0.254. This IP is proxy in SkyWorld cyberber cafe. I also change setting in Network Proxy and Apply System-Wide. But not work. I can use Internet from firefox but not work in terminal. So, I search in google and I try this comment in terminal

$ echo $http_proxy
192.168.0.254:8080

I print the http_proxy environment in terminal.It show IP. So I fixed like that

$ http_proxy=''
$ echo $http_proxy

And then I tryagain.It's work. I can update and install package from terminal again.