Kam Salisbury on 23 Sep 2005 00:58:19 -0000


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RE: [PLUG] routing/networking questions


-----Original Message-----
   >From: "Stephen Gran"<steve@lobefin.net>
   >Sent: 9/22/05 9:23:13 AM
   >To: "PLUG"<plug@lists.phillylinux.org>
   >Subject: [PLUG] routing/networking questions
   >
   >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,
   >-- 

Stephen, maybe check out the Shorewall site. They have lots of documentation and examples. I think you are making your set up unnecessarily difficult.

Kam Salisbury
http://salisburyfamily.us



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