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  • From: baslinux AT lists.ibiblio.org
  • To: baslinux AT lists.ibiblio.org
  • Subject: Re: [BL] gateway between two laptops
  • Date: Fri, 22 Aug 2008 10:48:50 +1200

Message from Steven
===================
Christof wrote:
>
> May be my mistake was that I thought firewall is
> something what only makes a working connection
> more secure.

You are correct, you do not need a firewall for
IP forwarding. However, a firewall is necessary
for IP masquerading (routing a private network
to the internet). I assume you have a firewall
in your wireless router and it is already capable
of routing local traffic to the internet.

> Now it seems to me that there will not be a
> connection at all without the firewall.

That is not correct. You do not need a firewall
to route traffic from the client machine through
the GW machine to your wireless connection.

CLIENT GW WIRELESS ROUTER
192.168.1.2------192.168.1.1
10.0.0.2--------10.0.0.x

> What I did:
> route add default gw 192.168.1.1 on client machine

This tells the client to route traffic for non-local
addresses to the GW. Specifically it sends packets
which do not have 192.168.1.x addresses to 192.168.1.1
The GW machine then decides what to do with the packet.

> The result:
> both machines ping to each other

The 192.168.1.x network is good.

> GW machine is online

The 10.0.0.x network is good and the GW machine
has a good default gateway to the internet. Note:
the GW has its own default gateway to the internet
(I'm guessing it is 10.0.0.1). Each machine has
its own default gateway, and they are different.

> client machine pings to 10.0.0.2

This is the same as pinging 192.168.1.1. Both
of those addresses refer to the same machine.

> client machine does not ping to 10.0.0.138 and
> has no connection to the internet

There are two possible reasons for this:
(1) the GW machine is not set for IP forwarding
(2) the wireless router does not know how to
find the client machine

To fix (1) echo "1" > /proc/sys/net/ip_forward

To fix (2) tell the wireless router where
to send traffic addressed to 192.168.1.2
---------------------------------
route add 192.168.1.2 gw 10.0.0.2
---------------------------------
The question is: are you able to edit the
routing table for the wireless router?

Cheers,
Steven






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