Port Allow iptables ubuntu | configure iptables

Here are few steps to allow ports or services :-

Just type these commands :-

To Check iptables RULES :-
$ sudo iptables -L

To Create iptables RULES :-
Eg:- to block icmp traffice on your server (ping block)

$ sudo iptables -A INPUT -d 10.10.10.10 -p icmp -j DROP

-A = to define rule (INPUT, FORWARD or OUTPUT)
-d = destination (your server ip in this case)
-p = protocol that you want to allow or block
-j = The functionality that you wanna perform (ACCEPT or DROP)

To Flush all iptables RULES :- (delete all rules)
$ sudo iptables -F                               (But be careful to use this command)

To Check iptables RULES by Line numbers:-
$ sudo iptables -L --line-numbers

To Delete iptables RULES by Line numbers:-
$ sudo iptables -D  INPUT --line-numbers
Eg: sudo iptables -D INPUT 7

To Allow all traffic on specific IP :-


$ iptables -A INPUT -s 192.168.0.1/32 -j ACCEPT

To Allow specific port :-

 $ iptables -A INPUT  -p tcp --sport 80 -m state --state NEW,ESTABLISHED -j ACCEPT
 $ iptables -A OUTPUT -p tcp --dport 80 -m state --state NEW,ESTABLISHED -j ACCEPT

 $ iptables -A INPUT  -p tcp --sport 443 -m state --state NEW,ESTABLISHED -j ACCEPT
 $ iptables -A OUTPUT -p tcp --dport 443 -m state --state NEW,ESTABLISHED -j ACCEPT


To Allow specific port on specific IP :-

$ iptables -I INPUT -p tcp -s 10.1.1.2 --dport 22 -j ACCEPT

Once you have them added and opened for those IPs, you need to close the door for the rest of IPs :-

$ iptables -I INPUT -p tcp -s 0.0.0.0/0 --dport 22 -j DROP

To save iptables RULES:-

$ sudo /etc/init.d/iptables-persistent save
$ sudo /etc/init.d/iptables-persistent reload

OR

$ sudo netfilter-persistent save
$ sudo netfilter-persistent reload