Assuming external internet card is eth0, and external IP is 123.12.23.43 and the internal network card is eth1, then:
$> modprobe ipt_MASQUERADE $> iptables -F; iptables -t nat -F; iptables -t mangle -F $> iptables -t nat -A POSTROUTING -o ppp0 -j SNAT --to 123.12.23.43 $> echo 1 > /proc/sys/net/ipv4/ip_forward |
Or for a dial-up connection:
$> modprobe ipt_MASQUERADE $> iptables -F; iptables -t nat -F; iptables -t mangle -F $> iptables -t nat -A POSTROUTING -o ppp0 -j MASQUERADE $> echo 1 > /proc/sys/net/ipv4/ip_forward |
Then to secure it:
$> iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT $> iptables -A INPUT -m state --state NEW -i ! eth0 -j ACCEPT $> iptables -P INPUT DROP #only if the first two are succesful $> iptables -A FORWARD -i ! eth1 -j REJECT |
Or for a dial-up connection (with eth0 as the internal network card):
$> iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT $> iptables -A INPUT -m state --state NEW -i ! eth0 -j ACCEPT $> iptables -P INPUT DROP #only if the first two are succesful $> iptables -A FORWARD -i ! eth1 -j REJECT |
And thats it! To view the rules do "iptables -t nat -L"