# Iptables.

## Allow ssh traffic.
~~~
iptables -A INPUT -p tcp --dport=22 -j ACCEPT

# -A  Append (End table) | -I Insert (Start table).
# -p  Protocol.
# -j  Action.
~~~

## Allow localhost traffic.
~~~
iptables -A INPUT -i lo -j ACCEPT

# -i  Interface name.
~~~

## Allow ping.
~~~
iptables -A INPUT -p icmp -j ACCEPT
~~~

## Warning!!!.
~~~
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
~~~

## Input policy drop.
~~~
iptables -P INPUT DROP
~~~

## Save/Restore rules from file.
~~~
iptables-save > ./filename.rules

# iptables-restore < ./filename.rules
~~~