问题原因
    该系统在安装的时候是安装了图形化界面服务，默认会安装 NetworkManager 管理服务，NetworkManager服务启动以后导致系统内部的网络配置出现紊乱。
    解决方法：
    [root@localhost ~]# chkconfig NetworkManager off
    Note: Forwarding request to ‘systemctl disable NetworkManager.service’.
    Removed symlink /etc/systemd/system/multi-user.target.wants/NetworkManager.service.
    Removed symlink /etc/systemd/system/dbus-org.freedesktop.NetworkManager.service.
    Removed symlink /etc/systemd/system/dbus-org.freedesktop.nm-dispatcher.service.
    Removed symlink /etc/systemd/system/network-online.target.wants/NetworkManager-wait-online.service.
    [root@localhost ~]# chkconfig network on
    [root@localhost ~]# service NetworkManager stop
    Redirecting to /bin/systemctl stop NetworkManager.service
    [root@localhost ~]# service network start
    Starting network (via systemctl): [ OK ]

    关闭NetworkManager，重启network即可
    systemctl stop NetworkManager ；systemctl restart network

    dhclient