1.关闭默认的firewall防火墙
systemctl stop firewalld.service 关闭防火墙
systemctl disable firewalld.service 关闭开机启动
2.开启iptables
yum install iptables （根据centOS7的版本和内核，有些版本已经装过，可以跳过此命令）
yum install iptables-services<br>service iptables restart<br>chkconfig iptables on或者systemctl enable iptables.service开机自启<br>
3.编辑防火墙文件（开启了21,22,80,3306端口）
vim /etc/sysconfig/iptables
# sampleconfiguration for iptables service
# # you can edit thismanually or use system-config-firewall
# # please do not askus to add additional ports/services to this default configuration
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -p tcp -m state --state NEW -m tcp --dport 21 -j ACCEPT
-A INPUT -p tcp -m state --state NEW -m tcp --dport 22 -j ACCEPT
-A INPUT -p tcp -m state --state NEW -m tcp --dport 80 -j ACCEPT
-A INPUT -p tcp -m state --state NEW -m tcp --dport 3306 -j ACCEPT
-A INPUT -j REJECT --reject-with icmp-host-prohibited
-A FORWARD -j REJECT --reject-with icmp-host-prohibited
COMMIT
4.添加防火墙命令
/sbin/iptables -I INPUT -p tcp --dport 80 -j ACCEPT
5.查看本机关于IPTABLES的设置情况
iptables -L -n