RFC on solution to Rejean's situation

Rejean Proulx rejean at interfree.ca
Sun Nov 2 07:59:56 EST 2003

I am interested in the solution that John proposed that will allow me to set
up an entry that effectively blocks all traffic from one of the Linux cards
from everything except Samba.  it was suggested to read Chapter 4 of the IP
command, but with the number of books out there, I have no idea what that
book is or where to get it.  If anyone has more details on this, I'd
appreciate it.  If this is simple, it might solve the problem quickly until
we devise a more elaborate  and proper solution.  Atg least I could get my
second subnet back which is badly needed.

 Rejean Proulx
Visit my family at http://interfree.ca
MSN is: rejp at rogers.com
Ham License VA3REJ

----- Original Message ----- 
From: "Luke Davis" <ldavis at shellworld.net>
To: <covici at ccs.covici.com>; "Speakup is a screen review system for Linux."
<speakup at braille.uwo.ca>
Sent: Sunday, November 02, 2003 1:33 AM
Subject: Re: RFC on solution to Rejean's situation

> To clarify: are you suggesting that the ADSL modem interface, be installed
> in the existing Linux machine, thus giving it three interfaces: one to the
> Windows network, and two to the net, with the Windows network having no
> net interfaces of its own?
> I see two potential downsides with this:
> 1.  If the Linux machine ever goes down for any reason, the Windows
> network is totally cut off from the internet.
> 2.  In addition to its heavy load in mail, apache, MYSQL, Samba, mailing
> list management, FTP, and other things, for many meg (to gig, if you count
> samba) of data per day, it now also has the load of serving as security
> guard, and traffic cop, for the entire network.
> Is this really a good thing?
> Luke
>  On Sat, 1 Nov 2003, John covici wrote:
> > I think the firewall stuff can be done on the same machine -- no need
> > for another box at all.  There are several ways to route the packets
> > from the windows system out a certain interface and you will need to
> > use iptables heavily along with the ip command to accomplish some of
> > this.
> >
> > One way which comes to mind off the top of my head is that you can
> > use the mangle table of iptables and put a statement in the
> > PREROUTING chain to mark the packets with 1 and then have a rule in
> > the policy database to send all such packets out the interface
> > desired.
> >
> > In addition the the ip tables unreliable guide from Rusty Russell and
> > the manpage, the ip command has an example in chapter 4 of its
> > documentation as to how to work with two interfaces, so this should
> > work fine.
> >
> > You can tell samba to only listen on a certain interface, so that
> > problem should be easily solved.
> >
> > Hope this helps.
> >
> >
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