Firewall Configuration

A proper firewall configuration ensures that only essential traffic is allowed while unauthorized traffic is blocked. In this way, the firewall acts as a protective barrier between the secure internal network and potentially untrusted external networks, such as the internet.

Configuration with IpTables

iptables is a firewall rule management tool in Linux, used to control network traffic by defining which packets can enter, exit, or pass through the system. It allows you to configure security policies to filter, redirect, and block traffic based on various criteria such as IP, port, and protocol. For example:

Generic command to open a specific port with iptables (replace <PORTA> with the desired port number)
Terminal input
```
    iptables -A INPUT -p tcp --dport <PORTA> -j ACCEPT
```
Save the iptables rules
Terminal input
```
    service iptables save
```
Reload the iptables service
Terminal input
```
    service iptables reload
```

In some Linux distributions, iptables may not be enabled by default. Use the following commands to check and enable iptables:

Check if iptables is installed
Terminal input
```
    sudo iptables -L
```
Install iptables if necessary

2.1 For RHEL-based systems
Terminal input
```
    sudo yum install iptables-services
```
2.2 For OpenSUSE
Terminal input
```
    sudo zypper install iptables
```

Configuration with firewalld

firewalld is a dynamic firewall manager for Linux that provides a simplified interface to configure and manage firewall rules in real time. It supports trust zones and allows flexible security policies without restarting the network service. For example:

Generic command to open a specific port with firewalld (replace <PORTA> with the desired port number)
Terminal input
```
    sudo firewall-cmd --zone=public --add-port=<PORTA>/tcp --permanent
```
Reload the rules
Terminal input
```
    sudo firewall-cmd --reload
```

Here is how to configure PostgreSYS component ports in firewalld:

Defining the ports

Terminal input
PORTAS=(5432 80 443 6432 8008 9187 8080 1982 2379 2380 9090 3000 9093)

for PORTA in "${PORTAS[@]}"; do
    sudo firewall-cmd --zone=public --add-port=${PORTA}/tcp --permanent
done

Reload the rules to apply the changes
Terminal input
```
sudo firewall-cmd --reload
```

If you need to install and enable firewalld:

Installation

Enterprise Linux
Terminal input
```
    sudo dnf install firewalld
```
OpenSUSE
Terminal input
```
    sudo zypper install firewalld
```

Enable firewalld to start on boot
Terminal input
```
    sudo systemctl enable firewalld
```
Start the firewalld service
Terminal input
```
    sudo systemctl start firewalld
```

Configuration with IpTables​

Configuration with firewalld​

Configuration with IpTables

Configuration with firewalld