echo 1 > /proc/sys/net/ipv4/ip_forward

Autoriser tout

iptables -P FORWARD ACCEPT

Autoriser eth0 à accéder à Internet

iptables -A FORWARD -i eth0 -o ppp0 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT
iptables -A FORWARD -i ppp0 -o eth0 -m state --state ESTABLISHED,RELATED -j ACCEPT

Exemple de conf

-A INPUT -i virbr4 -p udp -m udp --dport 53 -j ACCEPT
-A INPUT -i virbr4 -p tcp -m tcp --dport 53 -j ACCEPT
-A INPUT -i virbr4 -p udp -m udp --dport 67 -j ACCEPT
-A INPUT -i virbr4 -p tcp -m tcp --dport 67 -j ACCEPT
-A FORWARD -d 192.168.2.0/24 -i enp130s0 -o virbr4 -j ACCEPT
-A FORWARD -s 192.168.2.0/24 -i virbr4 -o enp130s0 -j ACCEPT
-A FORWARD -i virbr4 -o virbr4 -j ACCEPT
-A FORWARD -o virbr4 -j REJECT --reject-with icmp-port-unreachable
-A FORWARD -i virbr4 -j REJECT --reject-with icmp-port-unreachable
-A OUTPUT -o virbr4 -p udp -m udp --dport 68 -j ACCEPT