Using NATD and IPFW to share a cable connectionw with 2 enet cards


Ok so I'm trying to setup natd and ipfw to share my cable modem connection which is a static ip.

A bit of background..i have a b&w g3 running osx with a built in ethernet and a pci ethernet card...the built in ethernet (en0) is connected to my cable modem. The pci card (en1) is connected to hub that the rest of the computers on my home network are connected to that I want to share my cable connection with.

I've read the posts on configuring natd and ipfw for a ppp connection and tried tweaking it to work with dual ethernet cards but haven't had luck.

I have my two ethernet cards configured correctly:
en0 is connected to my cable modem - static ip and netmask are set

en1 is my internal network connection and the gateway. Its ip is set to and netmask is

IP Forwarding is enabled.

Heres the script I'm currently working with but is not working properly:



natd -interface en0

/sbin/ipfw -f flush
/sbin/ipfw add divert natd all from any to any via en0
/sbin/ipfw add pass all from any to any


I can't figure out what else I need to add...I've read the man pages for ipfw and natd in depth and am somewhat lost.

I think I just need to add something that will enable my en1 port to pass traffic through to the en1 port...? Do I need to add a route for traffic on en1? I'm clueless as to what to do next but feel i'm really close to getting this working...