centos虚拟机ping不通 报错 name or service not known

http://mirrors.ustc.edu.cn/centos/7.2.1511/os/x86_64/repodata/repomd.xml: [Errno 14] curl#6 - "Could not resolve host: mirrors.ustc.edu.cn; Unknown error"
Trying other mirror.

网卡配置问题，

进入 cd /etc/sysconfig/network-scripts

打开vi ifcfg-ens33

更改BOOTPROTO=dhcp

ONBOOT=yes

启用激活网卡

执行命令 

service network restart