1.关闭默认的firewall防火墙

systemctl stop firewalld.service #停止firewall

systemctl disable firewalld.service #禁止firewall开机启动

firewall-cmd --state #查看默认防火墙状态（关闭后显示notrunning，开启后显示running）

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

service iptables restart

chkconfig iptables on或者systemctl enable iptables.service开机自启

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 

5.查看本机关于IPTABLES的设置情况

iptables -L -n