linux routing issue

I am running redhat 9, 2.4.20-8 kernel

I am trying to make a linux box to be my ADSL dialup box with firewall
using iptables aswell as being a wireless connection point for my one
other wireless device.

I have got the the ADSL usb modem, eth0, eth1 and wlan0 working, I have
also setup some iptable rules.

My problem is with iptables off I cannot connect from eth1 to eth0 ( not
tried wlan0 yet)

my setup is as follows


Internet<-->Linux Box<----->eth0
|
------->eth1
|
|------------>wlan0

rc.local

#!/bin/sh
#
# This script will be executed *after* all the other init scripts.
# You can put your own initialization stuff in here if you don't
# want to do the full Sys V style init stuff.

touch /var/lock/subsys/local
echo 1 >/proc/sys/net/ipv4/ip_forward
~


DEVICE=eth0
BOOTPROTO=static
ONBOOT=yes
BROADCAST=192.168.20.255
IPADDR=192.168.20.250
NETMASK=255.255.255.0
NETWORK=192.168.20.0



DEVICE=eth1
BOOTPROTO=static
BROADCAST=192.168.0.255
IPADDR=192.168.0.250
NETMASK=255.255.255.0
NETWORK=192.168.0.0
ONBOOT=yes

[root@home1 network-scripts]# route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use
Iface
192.168.20.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
192.168.10.0 0.0.0.0 255.255.255.0 U 0 0 0
wlan0
169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0
wlan0
127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 lo

how do i get packets routed between my private NIC with a default route
outto the ADSL modem (ppp0) so I can also broswe the web, I have looked
at a few how to's but am a bit lost.
I have tried to included as much info as possible, any help would be
appreciated.

Thanks

Paul