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1，清空存在的策略 当你开始创建新的策略，你可能想清除所有的默认策略，和存在的策略，可以这么做： iptables -F 或者iptables -flush 2，设置默认策略 默认链策略是ACCEPT，改变所有的链策略为DROP: iptables -P INPUT DROP iptables -P FORWARD DROP iptables -P OUTPUT DROP 3，阻止一个指定的ip BLOCK_THIS_IP=“x.x.x.x" iptables -A INPUT -s ”$BLOCK_THIS_IP“ -j DROP iptables -A INPUT -i eth0 -s "$BLOCK_THIS_IP" -j DROP iptables -A INPUT -i eth0 -p tcp -s "$BLOCK_THIS_IP" -j DROP 4，允许SSH 允许所有通过eth0接口使用ssh协议连接本机： iptables -A INPUT -i eth0 -p tcp –dport 22 -m state –state NEW,ESTABLISHED -j ACCEPT iptables -A OUTPUT -o eth0 -p tcp –sport 22 -m state –state ESTABLISHED -j ACCEPT 5，允许某个网段通过ssh连接 iptables -A INPUT -i eth0 -p tcp -s 192.168.100.0/24 –dport 22 -m state –state NEW,ESTABLISHED -j ACCEPT iptables -A OUTPUT -o eth0 -p tcp –sport 22 -m state –state ESTABLISHED -j ACCEPT 6，允许http和https 允许所有进来的web流量：http协议的80端口 iptables -A INPUT -i eth0 -p tcp –dport 80 -m state –state NEW,ESTABLISHED -j ACCEPT iptables -A OUTPUT -o eth0 -p tcp –sport 80 -m state –state ESTABLISHED -j ACCEPT 允许所有进来的web流量：https协议的443端口 iptables -A INPUT -i eth0 -p tcp –dport 443 -m state –state NEW,ESTABLISHED -j ACCEPT iptables -A OUTPUT -o eth0 -p tcp –sport 443 -m state –state ESTABLISHED -j ACCEPT 7，多个策略联合一起 允许ssh，http，https： iptables -A INPUT -i eth0 -p tcp -m multiport –dports 22,80,443 -m state –state NEW,ESTABLISHED -j ACCEPT iptables -A OUTPUT -o eth0 -p tcp -m multiport –sports 22,80,443 -m state –state ESTABLISHED -j ACCEPT 8，允许SSH连接其他主机 iptables -A OUTPUT -o eth0 -p tcp –dport 22 -m state –state NEW,ESTABLISHED -j ACCEPT iptables -A INPUT -i eth0 -p tcp –sport 22 -m state –state ESTABLISHED -j ACCEPT 9，允许SSH连接指定的网段 iptables -A OUTPUT -o eth0 -p tcp -d 192.168.100.0/24 –dport 22 -m state –state NEW,ESTABLISHED -j ACCEPT iptables -A INPUT -i eth0 -p tcp –sport 22 -m state –state ESTABLISHED -j ACCEPT 10，允许https出去 iptables -A OUTPUT -o eth0 -p tcp –dport 443 -m state –state NEW,ESTABLISHED -j ACCEPT iptables -A INPUT -i eth0 -p tcp –sport 443 -m state –state ESTABLISHED -j ACCEPT 11，对web请求做负载均衡(每三个包，均衡到指定服务器，需要扩展iptables) iptables -A PREROUTING -i eth0 -p tcp –dport 443 -m state –state NEW -m nth –counter 0 –every 3 –packet 0 -j DNAT –to-destination 192.168.1.101:443 iptables -A PREROUTING -i eth0 -p tcp –dport 443 -m state –state NEW -m nth –counter 0 –every 3 –packet 1 -j DNAT –to-destination 192.168.1.102:443 iptables -A PREROUTING -i eth0 -p tcp –dport 443 -m state –state NEW -m nth –counter 0 –every 3 –packet 2 -j DNAT –to-destination 192.168.1.103:443 12，允许ping iptables -A INPUT -p icmp –icmp-type echo-request -j ACCEPT iptables -A OUTPUT -p icmp –icmp-type echo-reply -j ACCEPT 13，允许ping远程 iptables -A OUTPUT -p icmp –icmp-type echo-request -j ACCEPT iptables -A INPUT -p icmp –icmp-type echo-reply -j ACCEPT 14，允许本地回环 iptables -A INPUT -i lo -j ACCEPT iptables -A OUTPUT -o lo -j ACCEPT 15，允许内网访问外部网络 这个例子eth1 连接外部网络，eth0连接内部网络 iptables -A FORWARD -i eth0 -o eth1 -j ACCEPT 16，允许DNS出去 iptables -A OUTPUT -p udp -o eth0 –dport 53 -j ACCEPT iptables -A INPUT -p udp -i eth0 –sport 53 -j ACCEPT 17，允许NIS连接 NIS端口是动态的，当ypbind启动时它分配端口。 首先运行 rpcinfo -p 显示得到端口号，这个例子使用端口850,853。 iptables -A INPUT -p tcp –dport 111 -j ACCEPT iptables -A INPUT -p udp –dport 111 -j ACCEPT iptables -A INPUT -p tcp –dport 853 -j ACCEPT iptables -A INPUT -p udp –dport 853 -j ACCEPT iptables -A INPUT -p tcp –dport 850 -j ACCEPT iptables -A INPUT -p udp –dport 850 -j ACCEPT 上面的例子当ypbind重新启动时将失效，有2种解决方案： (1) 分配nis服务静态ip (2) 使用精妙的脚本 18，允许指定网段连接Rsync iptables -A INPUT -i eth0 -p tcp -s 192.168.101.0/24 –dport 873 -m state –state NEW,ESTABLISHED -j ACCEPT iptables -A OUTPUT -o eth0 -p tcp –sport 873 -m state –state ESTABLISHED -j ACCEPT 19，允许mysql从指定的网段连接 iptables -A INPUT -i eth0 -p tcp -s 192.168.100.0/24 –dport 3306 -m state –state NEW,ESTABLISHED -j ACCEPT iptables -A OUTPUT -o eth0 -p tcp –sport 3306 -m state –state ESTABLISHED -j ACCEPT 20，允许sendmail或者postfix iptables -A INPUT -i eth0 -p tcp –dport 25 -m state –state NEW,ESTABLISHED -j ACCEPT iptables -A OUTPUT -o eth0 -p tcp –sport 25 -m state –state ESTABLISHED -j ACCEPT 21，允许IMAP和IMAPS IMAP: iptables -A INPUT -i eth0 -p tcp –dport 143 -m state –state NEW,ESTABLISHED -j ACCEPT iptables -A OUTPUT -o eth0 -p tcp –sport 143 -m state –state ESTABLISHED -j ACCEPT IMAPS: iptables -A INPUT -i eth0 -p tcp –dport 993 -m state –state NEW,ESTABLISHED -j ACCEPT iptables -A OUTPUT -o eth0 -p tcp –sport 993 -m state –state ESTABLISHED -j ACCEPT 22，允许POP3和POP3S POP3： iptables -A INPUT -i eth0 -p tcp –dport 110 -m state –state NEW,ESTABLISHED -j ACCEPT iptables -A OUTPUT -o eth0 -p tcp –sport 110 -m state –state ESTABLISHED -j ACCEPT POP3S： iptables -A INPUT -i eth0 -p tcp –dport 995 -m state –state NEW,ESTABLISHED -j ACCEPT iptables -A OUTPUT -o eth0 -p tcp –sport 995 -m state –state ESTABLISHED -j ACCEPT 23，预防DOS攻击 iptables -A INPUT -p tcp –dport 80 -m limit –limit 25/minute –limit-burst 100 -j ACCEPT -m ：使用iptables扩展 –limit 25/minute : 限制分钟连接请求数 –limit-burst：触发阀值，一次涌入数据包数量 24，端口转发 来自442的都转到22端口 iptables -t nat -A PREROUTING -p tcp -d 192.168.102.37 –dport 422 -j DNAT –to 192.168.102.37:22 你还必须明确允许442端口 iptables -A INPUT -i eth0 -p tcp –dport 422 -m state –state NEW,ESTABLISHED -j ACCEPT iptables -A OUTPUT -o eth0 -p tcp –sport 422 -m state –state ESTABLISHED -j ACCEPT 25，包丢弃日志 你也许想查看所有丢弃包的日志。 首先创建一个新链叫 LOGGING iptables -N LOGGING 确保所有的连接跳到LOGGING iptables -A INPUT -j LOGGING 记录这些包通过自定义名字 "log-prefix" iptables -A LOGGING -m limit –limit 2/min -j LOG –log-prefix "IPTables Packet Dropped:" –log-level 7 最后丢弃这些数据包 iptables -A LOGGING -j DROP (责任编辑：IT) |