yum 無法使用 - Linux

今天想要 yum update

卻發生下面的情況:
Loaded plugins: fastestmirror, refresh-packagekit, security
Determining fastest mirrors
Could not retrieve mirrorlist
http://mirrorlist.centos.org/?release=6&arch=x86_64&repo=os error was
14: PYCURL ERROR 7 - "couldn't connect to host"

然後我找了很多資料去解決也無用.....

--