IPTABLES quick command list
Iptables is the default and powerful firewall that works on almost all Linux version including Ubuntu and Fedora. Here I have listed some important commands and a short description of each command for quick help. It can help people who already know little Iptables.
manage chain: # iptables -N new_chain // create a chain # iptables -E new_chain old_chain // edit a chain # iptables -X old_chain // delete a chain redirecting packet to a user chain: # iptables -A INPUT -p icmp -j new_chain listing rules: # iptables -L // list all rules of all tables # iptables -L -v // display rules and their counters # iptables -L -t nat // display rules for a specific tables # iptables -L -n --line-numbers // listing rules with line number for all tables # iptables -L INPUT -n --line-numbers // listing rules with line number for specific table manage rules: # iptables -A chain // append rules to the bottom of the chain # iptables -I chain [rulenum] // insert in chain as rulenum (default at the top or 1) # iptables -R chain rulenum // replace rules with rules specified for the rulnum # iptables -D chain rulenum // delete rules matching rulenum (default 1) # iptables -D chain // delete matching rules change default policy: # iptables -P chain target // change policy on chain to target # iptables -P INPUT DROP // change INPUT table policy to DROP # iptables -P OUTPUT DROP // change OUTPUT chain policy to DROP # iptables -P FORWARD DROP // change FORWARD chain policy to DROP