centos6.3 配置防火墙，开启80端口、3306端口

vi /etc/sysconfig/iptables
-A INPUT -m state –state NEW -m tcp -p tcp –dport 80 -j ACCEPT（允许80端口通过防火墙）
-A INPUT -m state –state NEW -m tcp -p tcp –dport 3306 -j ACCEPT（允许3306端口通过防火墙）
特别提示：很多网友把这两条规则添加到防火墙配置的最后一行，导致防火墙启动失败，正确的应该是添加到默认的22端口这条规则的下面
添加好之后防火墙规则如下所示：
######################################
# Firewall configuration written by system-config-firewall
# Manual customization of this file is not recommended.
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
-A INPUT -m state –state ESTABLISHED,RELATED -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -m state –state NEW -m tcp -p tcp –dport 22 -j ACCEPT
-A INPUT -m state –state NEW -m tcp -p tcp –dport 80 -j ACCEPT
-A INPUT -m state –state NEW -m tcp -p tcp –dport 3306 -j ACCEPT
-A INPUT -j REJECT –reject-with icmp-host-prohibited
-A FORWARD -j REJECT –reject-with icmp-host-prohibited
COMMIT
#####################################

最后重启防火墙使配置生效
/etc/init.d/iptables restart 

查看打开的端口：

# /etc/init.d/iptables status

关闭防火墙:

/etc/init.d/iptables stop