It runs. Im posting here from a PC connected to a LAN, connected to a netbook, connected to the internet via GPRS/UMTS USB. My setup is
Connection shematic
==================================================
PC1 PC2 PCx
\ | /
\ | / netbook
\ | / ---------------------------
-------------------- I NAT Gateway Device I ---------------------
I HUB I------I- eth0 : 192.168.3.5 I I Web provider I
I I I ppp0 $DEF_GW I-----I I
-------------------- --------------------------- ---------------------
Samsung nc10 Plus pinternet.interkom.com
Huawei USB GPRS modem nameserver 8.8.8.8
broadcast 192.168.3.255 nameserver 8.8.4.4
netmask 255.255.255.0
www.fonic.de gateway 10.64.64.64 = $DEF_GW
commands to be done on the netbook
=================================
tce-load -i iptables.tcz
tce-load -i iproute2.tcz
INT_DEV="eth0"
EXT_DEV="ppp0"
DEF_GW="`/sbin/ifconfig ppp0 | grep 'P-t-P' | awk '{print $3}' | sed -e 's/.*://'`"
echo 1 | sudo tee /proc/sys/net/ipv4/ip_forward
sudo /sbin/ifconfig eth0 192.168.3.5 broadcast 192.168.3.255 netmask 255.255.255.0
echo dont use 192.168.3.5 for the PCs IP but another like 192.168.3.1 or 2 or 7 ..
sudo /sbin/ifconfig eth0 up
sudo iptables -F
sudo iptables -X
sudo iptables -t nat -F
sudo iptables -t nat -X
sudo iptables -P INPUT ACCEPT
sudo iptables -P OUTPUT ACCEPT
sudo iptables -P FORWARD ACCEPT
sudo iptables -A FORWARD -i $INT_DEV -o $EXT_DEV -j ACCEPT
sudo iptables -t nat -A POSTROUTING -o $EXT_DEV -j MASQUERADE
sudo iptables -A FORWARD -i $EXT_DEV -o $INT_DEV -m state --state RELATED,ESTABLISHED -j ACCEPT
sudo route del default
sudo route add default gw $DEF_GW
commands to be done on one PC
=================================
sudo ifconfig eth0 192.168.3.1 broadcast 192.168.3.255 netmask 255.255.255.0
sudo route add default gw 192.168.3.5
echo 192.168.3.5 is the default gateway for eth0 of the netbook router
echo 192.168.3.1 is the IP of the PC you are working on
Attention: the same resolv.conf must be used on PC and netbook.
resolv.conf pinternet.interkom.com
nameserver 8.8.8.8
nameserver 8.8.4.4
Place for improvement: the firewall caracteristics.