Hello,
My server is on Mandrake 10.1 off.
eth0 is WAN with static IP connected 512 DSL
eth1 is LAN.

I went to webmin->networking ->linus firewall
and did a NAT on eth0. I applied and rebooted.

On clients system I am not getting the internet.
But I am able to ping my server's static IP from
clients.

How to troubleshoot ?

My iptables file is as follows :

Generated by iptables-save v1.2.9 on Sun Dec 26 08:51:30 2004
*nat
:OUTPUT ACCEPT [0:0]
:PREROUTING ACCEPT [0:0]
:POSTROUTING ACCEPT [0:0]
-A POSTROUTING -o eth0 -j MASQUERADE
COMMIT
# Completed on Sun Dec 26 08:51:30 2004
# Generated by iptables-save v1.2.9 on Sun Dec 26 08:51:30 2004
*mangle
:PREROUTING ACCEPT [387458:22182653]
:INPUT ACCEPT [387217:22168730]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [386761:22141899]
:POSTROUTING ACCEPT [386489:22126327]
COMMIT
# Completed on Sun Dec 26 08:51:30 2004
# Generated by iptables-save v1.2.9 on Sun Dec 26 08:51:30 2004
*filter
:INPUT ACCEPT [415163:23768840]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [414645:23738052]
COMMIT
# Completed on Sun Dec 26 08:51:30 2004

Thanks

Varun

cat /proc/sys/net/ipv4/ip_forward
1

If that shows a zero then you need to change it..

echo 1 > /proc/sys/net/ipv4/ip_forward

And put that in your startup scripts somewhere.

You need to set the dns servers on the clients and also be sure that they can access them.

You could try an ip address on the internet to see if it works.

Thanks David it worked

Awesome

Hello David,
Can you tell me howto do the same using
shorewall.

Thanks

Varun

hi there

for shorewall just add the followind line to the masq file
ppp0 192.168.0.0/24

where ppp0 is my external device i.e modem and and i am masquarading my netwrk 192.168.0.0

regards

Hello David,
I have :

eth0 is WAN with static IP connected 512 DSL
eth1 is LAN - 192.168.0.0 / 255

Any changes or I should do what you posted

Thanks

Varun

u shoud make an entry like this

eth0 192.168.0.0/24

regards

u shoud make an entry like this

eth0 192.168.0.0/24

regards

Can you explain me :

eth0 192.168.0.0/24

Thanks

Varun

if u have look at the masq file

then
#INTERFACE SUBNET ADDRESS PROTO PORT(S)
eth0 192.168.0.0/24

this specifies that th interface "eth0" is maquerading the subnet 192.168.0.0/24


regards

My post above is only to insure that the machine is forwarding traffic. The proceedure for testing this and also for fixing the problem is the same.

enter this command..

cat /proc/sys/net/ipv4/ip_forward


If you do not see a "1" as in if you see a "0" then you will not have any ip traffic forwarded.

If this is true then you enter this command..


echo 1 > /proc/sys/net/ipv4/ip_forward

If your configuration and startup scripts are not setting this automatically at boot then you would need to add the command to one of your startup scripts.


Most of the mainstream distros have network and firewall configuration tools that have this option and would setup the option to be enabled for you.

You can put the command in your /etc/rc.local file if you have one and it will be executed on every boot. Your other option could be to search for your distros built in method for setting the option if there is one. The end result would be the same either way.


If the value is set to 1 then the kernel will forward ip packets. Other firewall related configuration will also determine if it will do what you expect.

Normally pinging a known ip address would be my first test if I have a problem. Then I would move on to DNS if that works.

If you are not using your distros iptables scripts and shorewall or whatever else your using does not set the ip forwarding option then I would go with /etc/rc.local.