centos中对iptables进行管理实例：
对固定网段进行3306端口开放
-bash-3.2# iptables -I INPUT -s 121.124.152.0/22 -p tcp --dport 3306 -j ACCEPT
-bash-3.2# iptables -I INPUT -s 111.87.191.0/28 -p tcp --dport 3306 -j ACCEPT
-bash-3.2# /etc/init.d/iptables save
-bash-3.2# service iptables restart
原文：http://www.cnblogs.com/ganb/p/3958373.html