*`iptables` is a systemd service and hence started accordingly.
*`/etc/iptables/iptables.rules` will be applied when you start or enable the `iptables.service`.
* After adding rules via command-line as shown in the following sections, the configuration file is not changed
automatically — you have to save it manually:
```iptables-save -f /etc/iptables/iptables.rules
```
* Listing rules with `iptables -nvL`.
## Basic Rules (Offline setup)
### FORWARD
* First of all, our computer is not a router (unless, of course, it is a router). We want to change the default policy on the FORWARD chain from ACCEPT to DROP
`iptables -P FORWARD DROP`
## INPUT
1.`iptables -A INPUT -i lo -j ACCEPT`
2.`iptables -A INPUT -n conntrack -ctstate ESTABLISHED,RELATED -j ACCEPT`
3.`iptables -A INPUT -n conntrack -ctstate INVALID -j DROP`
