[root@centos httpd]# /sbin/iptables -I INPUT -p tcp --dport 53 -j ACCEPT

[root@centos httpd]# /etc/rc.d/init.d/iptables save

[root@centos httpd]# /etc/init.d/iptables restart

这样就搞定了，查看效果

[root@centos httpd]# /etc/init.d/iptables status