单个网卡操作
[root@localhost ~]# ifdown eth0 #关闭网络
[root@localhost ~]# ifup eth0 #启动网络 网络服务：
[root@localhost ~]# service network stop #关闭网络服务
[root@localhost ~]# service network start #启动网络服务
[root@localhost ~]# service network restart #重启网络服务
root@localhost ~]# service network status #查看网卡状态
当网重启出问题时，如下：
network.service - LSB: Bring up/down networking
Loaded: loaded (/etc/rc.d/init.d/network; bad; vendor preset: disabled)
Active: failed (Result: exit-code) since 五 -- :: CST; 22h ago
Docs: man:systemd-sysv-generator()
Process: ExecStart=/etc/rc.d/init.d/network start (code=exited, status=/FAILURE) 8月 :: node4 systemd[]: Starting LSB: Bring up/down networking...
8月 :: node4 network[]: 正在打开环回接口： 错误：激活连接失败：No suitable device found for this connection.
8月 :: node4 network[]: [失败]
8月 :: node4 network[]: 正在打开接口 eno16777736： 错误：激活连接失败：No suitable device found for this connection.
8月 :: node4 network[]: [失败]
8月 :: node4 network[]: 正在打开接口 eth0： [ 确定 ]
8月 :: node4 systemd[]: network.service: control process exited, code=exited status=
8月 :: node4 systemd[]: Failed to start LSB: Bring up/down networking.
8月 :: node4 systemd[]: Unit network.service entered failed state.
8月 :: node4 systemd[]: network.service failed.
解决办法：
先删除多余的ifcfg-eno16777736文件
systemctl stop NetworkManager systemctl disable NetworkManager 然后在执行
systemctl start network.service