iptables小结(6)

                   --sport
                -p icmp
                   --icmp-type 8
                     echo-request ==8  ping出去的数据包
                     echo-reply ==0  ping的相应
              显式扩展         
                 使用各种扩展模块
                   -p tcp -m multiport --drops 21,23,80
           ACTION
              -j  ACTION  
                  DROP   悄悄拒绝
                  REJECT 明确拒绝
                  ACCEPT 接受
                  custom_chain