When I installed Ubuntu 5.10, I managed to set up my pppoe connection via eth0 and share this connection with eth1 (XP box). Everything worked fine, but the day after when I executed my iptables script, my xp box was unable to connect to the internet. Whats even worse, the 2 machines can't even ping to each-other anymore. I tried everything and finally I reinstalled the ubuntu, but I couldn't even ping after the fresh installation. My ubuntu has also windows xp so when I boot to xp then it can forward packets and ping other xp machine just fine so its not a hardware problem nor there is not anything wrong with the xp box I want mu ubuntu to have connection with. Btw my pppoe connection via eth0 works fine so please leave that alone

Now please tell me if I'm just being very unlucky or is there something wrong with my configuration

Now something more specific:

jk@jk:~$ ifconfig
eth0 Link encap:Ethernet HWaddr 00:08:A1:7D:79:20
inet addr:1.2.3.4 Bcast:1.255.255.255 Mask:255.0.0.0
inet6 addr: fe80::208:a1ff:fe7d:7920/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:4064 errors:0 dropped:0 overruns:0 frame:0
TX packets:2648 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:1914858 (1.8 MiB) TX bytes:746372 (728.8 KiB)
Interrupt:12 Base address:0xd400

eth1 Link encap:Ethernet HWaddr 00:C0:26:76:9F:CB
inet addr:192.168.0.1 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::2c0:26ff:fe76:9fcb/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:26 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 b) TX bytes:1638 (1.5 KiB)
Interrupt:12 Base address:0xd000

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:8388 errors:0 dropped:0 overruns:0 frame:0
TX packets:8388 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:765432 (747.4 KiB) TX bytes:765432 (747.4 KiB)

ppp0 Link encap:Point-to-Point Protocol
inet addr:84.52.50.124 P-t-P:212.7.9.118 Mask:255.255.255.255
UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1492 Metric:1
RX packets:2551 errors:0 dropped:0 overruns:0 frame:0
TX packets:2506 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:3
RX bytes:1604236 (1.5 MiB) TX bytes:686927 (670.8 KiB)


jk@jk:~$ cat /etc/network/interfaces
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# This is a list of hotpluggable network interfaces.
# They will be activated automatically by the hotplug subsystem.
mapping hotplug
script grep
map eth0
# The primary network interface
iface eth1 inet static
address 192.168.0.1
netmask 255.255.255.0

auto eth1

auto dsl-provider
iface dsl-provider inet ppp
provider dsl-provider

pre-up /sbin/ifconfig eth0 up # line maintained by pppoeconf

iface eth0 inet static
address 1.2.3.4
netmask 255.0.0.0

auto eth0

jk@jk:~$ route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
212.7.9.118 * 255.255.255.255 UH 0 0 0 ppp0
192.168.0.0 * 255.255.255.0 U 0 0 0 eth1
1.0.0.0 * 255.0.0.0 U 0 0 0 eth0
default 212.7.9.118 0.0.0.0 UG 0 0 0 ppp0