A problem getting ADSL to work

[Howard Lowndes]

I have a client who has taken up an ADSL connection with Flow Comms and I
am having the devil getting it working correctly.

ASCII piccy

Private network         192.168.1.0/24
                               |
                               |-- 192.168.1.20 (234.234.234.235)
                           eth0|                      (alias)
                   -------------------------
                   |      192.168.1.1      |
                   |   (234.234.234.234)   |
Linux Box          |        (alias)        |
                   |                       |
                   |                       |
                   |      172.24.1.2       |
                   -------------------------
                           eth1|
                               |
                      ^^^^^^^^^^^^^^^^^^^
ADSL Service Provider     172.24.1.1
                               ?
                               ?
                      The world out there


The problem is how do I get masquerading to use the 234.234.234.234
address as if it on the outside interface rather than the 172.24.1.2
address which is the true interface address.  Even if I re-alias the eth1
interface as 234.234.234.234 instead, it still don't work.

If I ping from the Linux box to the outside world then nothing happens
because it tries to use the 172.24.1.2 address as the source address and
that doesn't work with the ADSL service provider, but if I force the ping
to use the 234.234.234.234 address as its interface address (with the -I
option) then success.  I guess the 172.24.x.y address are only there just
so that the modem and the DSLAM have an address each.

Basically I need the 172.24.1.1 address to be the default gateway, but I
always want the Linux Box to say that its interface address to that
default gateway is 234.234.234.234 for the purposes of pinging and
masquerading.

Any ideas?

-- 
Howard.
LANNet Computing Associates - Your Linux people
Contact detail at http://www.lannetlinux.com