查看防火墙的状况

service iptables status

开启与关闭防火墙

1) 永久生效

开启: chkconfig iptables on
　　  chkconfig ip6tables on ---针对ipv6
关闭: chkconfig iptables off
　　  chkconfig ip6tables off ---针对ipv6

2) 即时生效，重启后失效
开启: service iptables start
关闭: service iptables stop

3) Centos7.0 以后不再使用 service, 而是systemctl
状态：systemctl status firewalld
开启：systemctl start firewalld
关闭：systemctl stop firewalld