dovresti abilitare un po' di cose inerenti iptables...io mi sono fatto questo rudimentale script (ovviamente cambia gli ip e mettici i tuoi):
codice:
/sbin/modprobe ip_tables
/sbin/modprobe ip_conntrack
/sbin/modprobe iptable_nat
/sbin/modprobe ipt_MASQUERADE
ifconfig eth0 192.168.0.1 netmask 255.255.255.0
ifconfig eth1 192.168.2.1 netmask 255.255.255.0
echo "1"> /proc/sys/net/ipv4/ip_forward
iptables -t nat -A POSTROUTING -d ! 192.168.2.2 -j MASQUERADE
iptables -A FORWARD -s 192.168.2.2/24 -j ACCEPT
iptables -A FORWARD -d 192.168.2.2/24 -j ACCEPT
iptables -A FORWARD -j DROP