SYS: Use iptables to implement packet filtering and configure network address translation (NAT).

To implement NAT on a server with two network cards (eth0:192.168.1.1/24 connected to the Internet and eth1:192.168.2.1/24 connected to the internal network) several steps are required.

Edit the /etc/sysctl.conf file and assign 1 to the ‘net.ipv4.ip_forward‘ option:

net.ipv4.ip_forward = 1

Update the system:

# sysctl -p

Add a new rule to the firewall:

# iptables -t nat -I POSTROUTING -o eth0 -s 192.168.2.0/24 -j MASQUERADE

Save the firewall configuration:

# service iptables save