Simple NATed home network problem

[John Reinke <jmreinke@pantheranet.com>]

I've been beating my head against this for a while, and I better ask for
help before it starts getting bloody...

I have a typical setup at home: a small network connected through my
Debian box via NAT to my cable modem. Or, at least, that's what I used to
have until I upgraded to Woody.

Using the same network cards with the 2.2.x kernel (and ipchains) on
Potato, I had everything running well. Now that I've upgraded to Woody and
the 2.4.x kernel (iptables), I can't seem to get it to recognize my
network.

When I have all the rules applied, I cannot access anywhere - not out on
the Internet or anywhere on my local network. A ping command just sits
there, without any feeback. It will show the IP address only for hosts
listed in /etc/hosts, but nothing else.

I've tried creating scripts for iptables from the Masquerading Made Simple
HOWTO, fwbuilder, firestarter, and Bastille Linux - all without success.
If I comment out my second NIC (eth1 for the local network) in the
/etc/network/interfaces file, I can usually get the first NIC (eth0 for
Internet access) to work again with the cable modem. To date, I've never
been able to ping anything local or remote if both interfaces are
uncommented in the /etc/network/interfaces file and I restart the network.

Here's what I have in the file:

# /etc/network/interfaces -- configuration file for ifup(8), ifdown(8)

# The loopback interface
auto lo
iface lo inet loopback

# The first network card - internet connection
auto eth0
iface eth0 inet dhcp

# The second network card - local network
auto eth1
iface eth1 inet static
	address 172.16.1.1
	netmask 255.255.255.0
	broadcast 172.16.1.255
	network 172.16.1.0
	gateway 172.16.1.1


This is basically what I had in this file before I did an install of
Woody, but I didn't have the auto lines. The options file includes
ip_forward=yes.

I'm currently using the 2.4.18-k7 kernel image, but I've also tried a
compiled 2.4.18 kernel.

I've even swapped out one of my NICs temporarily because I saw in the
archives where someone had trouble with a Realtek NIC.

Does anyone have suggestions? This is driving me bonkers.

Thanks,
John