今天发现有一台服务器没有配置防火墙，使用service iptables start/stop没啥反应．然后，/etc/sysconfig/iptables这个文件缺失．
防火墙配置例子：
-
# 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 -j REJECT –reject-with icmp-host-prohibited
-A FORWARD -j REJECT –reject-with icmp-host-prohibited
COMMIT
解决：
随便配置一条规则：iptables -P OUTPUT ACCEPT
service iptables save
