echo Enabling Masquerade...
modprobe ipt_MASQUERADE
iptables -F; iptables -t nat -F; iptables -t mangle -F
iptables -t nat -A POSTROUTING -o eth0 -j SNAT --to XX.YY.ZZ.TT
echo 1 > /proc/sys/net/ipv4/ip_forward

Note: eth0 is your local net. XX.YY.ZZ.TT is your public ip (internet)