[plug] Still not able to route to adsl

[James Devenish]

Hi,

Are we able to put this thread to bed, soon? I'm worried that you might
not be getting help because people will be ignoring the rambling nature
of this situation. I have been hoping that one of the well-known posters
would step in a set the record straight, but only Matt has stepped
forward so far. I'm a bit concerned by the thread because, to me, it
looks like a 'garden-variety' situation that is probably very familiar
to several of the prominent people on this list, and presumably others
too.

Now, would I be correct is saying that this summarises your situation:

>   _________________Host___________________
>   |                  |                   |
>  eth1              eth0                 ppp0
> 192.168.1.2     192.168.0.1        203.59.131.96
>   |              ____|____               |
>   |              |   |   |             World
> 192.168.1.1    Host Host Host
> ADSL (NB1300+4)
> a.b.c.d
>   |
> World

In this scenario, you know you are fine if you chop off the ADSL branch
completely, because that's what you previously had. Now, you're telling
us that it doesn't work if you turn of PPP and try to use ADSL instead,
is that correct? Looking at the situation with PPP chopped off, I don't
see why you'd be adding lots of manual routes at all. I would think that
you just need to set a static address for eth0, DHCP your eth1, enable
forwarding, then enable masquerading. This would amount to four or five
lines of ifconfig/route/iptables commands, right (well, on a Debian
system, you'd set up your loopback and Ethernet interfaces in
/etc/networking/interfaces so our would only need to enable fowarding
and masquerading manually)? Hopefully an expert will let us know.

Now, I am not a networking expert, but I can't really see why this
situation is being problematic. Could one of the experts with PPP
experience please let us know whether `netstat -r` should show the
showing something like the following in a functional situation
(assuming PPP was being used):

Kernel IP routing table
Destination   Gateway       Genmask         Flags MSS Window irtt Iface
192.168.0.0   *             255.255.255.0   U     0      0       0 eth0
192.168.1.0   *             255.255.255.0   U     0      0       0 eth1
203.69.131.96 *             255.255.255.255 UH    0      0       0 ppp0
default       203.69.131.96 0.0.0.0         UG    0      0       0 ppp0

Bob: is this what your routing table /used/ to look like? If not, it's
my fault for guessing wrongly.

In the above situation, all your Internet traffic is going over PPP
unless someone happens to know your ADSL router's address, in which case
they could also interact with your Linux machine in its capacity as
192.168.1.2. All your internal hosts would talk amongst themselves
happily and use 192.168.0.1 as their gateway for Internet access (i.e.
they would end up masqueraded as 203.69.131.96).

If ADSL were being used instead of PPP:

Kernel IP routing table
Destination   Gateway       Genmask       Flags MSS Window irtt Iface
192.168.0.0   *             255.255.255.0 U     0      0       0 eth0
192.168.1.0   *             255.255.255.0 U     0      0       0 eth1
default       192.168.1.1   0.0.0.0       UG    0      0       0 eth1

And this would just "work" in the same way that PPP worked, except that
your ADSL router would handle the a.b.c.d<->192.168.1.2 aspect of the
situation. Is it possible for you to 'start from scratch' -- even get
rid of your firewall perhaps -- and just do 'simple' things (i.e.
definitely don't go about adding manual routes for all and sundry --
let your kernel calculate Ethernet routes for the other hosts itself).