> -----Original Message-----
> From: centos-bounces@xxxxxxxxxx
> [mailto:centos-bounces@xxxxxxxxxx] On Behalf Of Marko A. Jennings
> Sent: Thursday, January 03, 2008 7:29 AM
> To: centos@xxxxxxxxxx
> Subject: Re: Firewall frustration
>
> On Thu, January 3, 2008 8:18 am, Robert Moskowitz wrote:
> > Steven Haigh wrote:
> >> On 03/01/2008, at 3:34 PM, Robert Moskowitz wrote:
> >>> Christopher Chan wrote:
> >>>>
> >>>>> I spent much of the past 24 hours trying to find out
> how to set up
> >>>>> iptables for firewall routing WITHOUT NATing. Could not find
> >>>>> anything.
> >>>>>
> >>>>
> >>>> Eh? You just need to enable ip forwarding to enable
> routing. After
> >>>> that, it is put up the firewall rules as is necessary, build the
> >>>> appropriate routing tables on the firewall box and the
> boxes on the
> >>>> intranet(s).
> >>>>
> >>>> iptables does not handle routing.
> >>> No, but iptables controls what is allowed to route,
> >>
> >> I think this is where you are getting confused and causing
> yourself
> >> issues. iptables has ZERO effect on what is allowed to
> route. It is a
> >> simple YES or NO as to if it should be allowed to pass or
> be filtered.
> > I have been tested as having a significant language usage
> problem, and
> > am working on it. 'what is allowed to route', was a poor choice of
> > wording. What you wrote above is much closer to what I
> wanted to say.
> >
> > ip src/dest is used for routing decisions by the kernel.
> The IP state
> > machine (check the RFC or any decent TCP/IP textbook) is
> really quite
> > simple. But iptables sticks its nose into the center of that state
> > machine and can mangle addresses to change how packets flow through
> > the machine, or just simplely yank packets right out of the machine
> > with a simple NO (drop).
> >
> > So in my mind's eye of the IP state machine (my MSU CPS 410
> prof was
> > death on state machines; turn in a perfectly executing assignment
> > without one and there went half your grade. See HIP for its state
> > machine) is dictated by iptables as to what it is allowed to route.
> >>
> >>> Those little words, "put up the firewall rules as necessary" are
> >>> equivalent to "and magic happens here."
> >>
> >> It's actually not magical at all... Work with the mindset
> of "I want
> >> to allow X, Y, and Z, then deny everything else". This translates
> >> easily into iptables rules -j ACCEPT and then your last rule (or
> >> policy) should be a deny/drop/reject.
> > That is exactly what I tried to do. I just used the wrong
> bit of pixie
> > dust (during some of the 'heated' IPsec meeting debates one fellow
> > would try to sneak up a speaker 'that just did not get it' and
> > sprinkle some glitter on them. He had labeled his tube of
> glitter as
> > 'security pixie dust').
>
> If you are interested in learning how iptables work, I
> suggest reading this book:
>
> Linux Firewalls, Second Edition
> by Robert L. Ziegler
> ISBN 0-7357-1099-6
>
> It covers everything from packet filtering concepts to
> practical examples.
>
> Marko
Thanks, I was just going to ask....
Dennis
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