iptables configuration brief

   The frequency of using iptables configuration is very low, but it is quite troublesome to check the information every time. In fact, the command looks cumbersome, but there are still rules to remember.
   First, under iptables --help, look at the approximate command parameters.
  
   Add entry rules:
    iptables -A [chainname] -p [tcp] --dport [8081] -j ACCEPT
    where chainname is commonly used INPUT and OUTPUT, which can be viewed through iptables -L. For entry rules, fill in INPUT. --dport fill in the access port.
   Add an exit rule:
    iptables -A OUTPUT -p tcp --sport 8081 -j ACCEPT
   is similar to the entry rule, except that -A becomes OUTPUT, and
 
   after editing the port written by --sport, save it: /sbin/service iptables save

   Delete:
    iptables -L --line-numbers to see the current rules.
    iptables -D [rulenum]   
  
   Others:
   iptables -A INPUT -i lo -j ACCEPT
   iptables -A OUTPUT -o lo -j ACCEPT
   Open the "loopback" first to avoid unnecessary trouble.

   iptables -A INPUT -i eth+ -p icmp --icmp-type 8 -j ACCEPT
   iptables -A OUTPUT -o eth+ -p icmp --icmp-type 0 -j ACCEPT
   enables ping on all network cards for easy maintenance and detection .



Some other configurations:
   http://blog.chinaunix.net/uid-9950859-id-98279.html