First of all you should verify if your Linux permits routing over the interfaces:
the file /proc/sys/net/ipv4/ip_forward should contains the value 1.
Just to be sure try with:
Code:
echo "1" > /proc/sys/net/ipv4/ip_forward
Then you have to make NAT between your home net net and the isp net, if you have set up a firewall you have to enable forwarding from your network and then you have to enable NAT:
Code:
iptables -P FORWARD ACCEPT
iptables -F FORWARD
iptables -I POSTROUTING -t nat -s <YOUR HOME NET> -j MASQUERADING
Assuming that your network configurations are ok, if ip_forward and NAT are set up you should be able to ping over your linux box.