在centos7.0默认使用firewalld服务，若萱使用iptables，需要禁用firewalld并启动iptables
systemctl stop firewalld
systemctl disabled firewalld
安装 iptables
yum install iptables-services
systemctl enbale iptables
cp /usr/libexec/iptables/iptables.init /etc/init.d/iptables
service iptables save
service iptables stop
service iptables start
systemctl stop iptables
systemctl start iptables