[PLUG] routing/networking questions

[Stephen Gran <steve@lobefin.net>]

Hello all,

So, here I am set up in the UK, and facing some routing oddness on my
home network.  First, the description:

I have a routed /29 available to me - 82.71.90.{96-103}
I have a PPPoATM connection, currently being done by a junk ADSL modem.
I have a couple of machines providing public services (smtp, http, etc)
.102 is the gateway between the /29 and the internet - my ISP routes all
  traffic for the /29 to .102, and I use it as my gateway for the other
  machines.  .102 is also the address assigned to whatever machine does
  the PPoATM connection.

Leaving aside for the moment that my ADSL modem is junk, I have some
questions about the best way to arrange the network.

So, whatever machine does PPPoATM has to have 2 interfaces, broadly
speaking - ppp0 and eth0.  This means I have to lose 2 out of 6 usable
IPs to my ADSL modem, which seems extraordinarily silly to me.  I have,
for the moment, in a bit of truly grotesque inspiration, given eth0 on
the ADSL modem the address 192.168.1.1, with a /24, and turned off NAT.
Then I gave it a static route to 82.71.90.96/29 via eth0.  

I gave all the machines with public IPs behind it a single static IP
address in the /29 (.97, .98, etc) and also gave them an eth0:1 in the
range 192.168.1.0/24 - this second IP in the private range is necessary
to make arp work.  So, now I have 5 out of the 6 IP addresses, which is
probably as good as I am going to get out of this sort of setup.

But now to the question - can I make this work without having to resort
to this hack?  It seems to me there ought to be some way to make the
ethernet port on the ADSL modem not have an IP at all, and just act as
a sort of transparent bridge to the subnet.  I do not know if this sort
of thing is possible with consumer grade hardware, of course, or if I
am just wishing for something not really doable.  I think, also, that
there are issues with IP bridging between PPP and ethernet, although I
don't know all the ramifications.

Thanks for any advice,
-- 
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|  Stephen Gran                  |   I don't think anyone should write     |
|  steve@lobefin.net             | their autobiography until after         |
|  http://www.lobefin.net/~steve | they're dead. -Samuel Goldwyn           |
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