CentOS 7.0默认使用的是firewall作为防火墙，这里改为iptables防火墙。
1、关闭firewall：
systemctl stop firewalld.service #停止firewall systemctl disable firewalld.service #禁止firewall开机启动
2、安装iptables防火墙
yum install iptables-services #安装
vi /etc/sysconfig/iptables #编辑防火墙配置文件
######################################
# Firewall configuration written by system-config-firewall
# Manual customization of this file is not recommended.
*filter
:INPUT ACCEPT [:]
:FORWARD ACCEPT [:]
:OUTPUT ACCEPT [:]
-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 -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport -j ACCEPT
-A INPUT -j REJECT --reject-with icmp-host-prohibited
-A FORWARD -j REJECT --reject-with icmp-host-prohibited
COMMIT ######################################## :wq! #保存退出
systemctl restart iptables.service #最后重启防火墙使配置生效 systemctl enable iptables.service #设置防火墙开机启动