IP Masq does ICMP but not TCP

1. Set up 2 nic cards with different tcp/ip properties and ip masq

I'm setting up IP masquerading on a cable modem with two different
computers, an NT box and a linux box.  I have two nic cards in the linux
box, both working.  I have set up most of Ip masquerading including
loading the modules nad recompiling the kernel.  Right now i'm trying to
configure each nic card with different tcp/ip properties.  One leading
out to my cable modem and the cable modem provider(24.*.*.*) and the
other pointing to an internal network, (192.168.*.*).  when i do
'netconfig' it just sets up general tcp/ip properties for everything and
does not let me specify each nic card.  Can anyone help me?  Please do
not point me to how tos on IP masquerading as I'm pretty sure about that
and that's not what i need help with.

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