Date: Tue, 27 Aug 2002 14:54:45 -0700 From: "Crist J. Clark" <crist.clark@attbi.com> To: Nick Rogness <nick@rogness.net> Cc: John Resnier <john_resnier@yahoo.com>, freebsd-ipfw@FreeBSD.ORG Subject: Re: Policy routing using IPFW for multiple ISP's Message-ID: <20020827215445.GA8419@blossom.cjclark.org> In-Reply-To: <20020827093602.S34430-100000@skywalker.rogness.net> References: <20020827053607.GB4732@blossom.cjclark.org> <20020827093602.S34430-100000@skywalker.rogness.net>
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On Tue, Aug 27, 2002 at 09:41:48AM -0600, Nick Rogness wrote:
> On Mon, 26 Aug 2002, Crist J. Clark wrote:
>
> > On Mon, Aug 26, 2002 at 02:59:59PM -0600, Nick Rogness wrote:
> > > On Mon, 26 Aug 2002, John Resnier wrote:
> > >
> > > > Hey Crist
> > > >
> > > > Thanks for your help. Only reason why I didn't do it with a route is
> > > > that I wanted ipfw to forward on the app layer. Ideally, I would like
> > > > to have all web traffic destined for the 66.25.xx.0/24 range to go out
> > > > the DSL Gateway but the rest of the web traffic go out the Cable
> > > > connection.
> >
> > <pedantic>You mean forward at the transport layer.</pedantic>
> >
> > > > The example I provided did not show all that information
> > > > because I wanted to get this problem solved first. Any examples you
> > > > would have on how to accomplish this would be awesome!!
> > >
> > >
> > > # set next-hop address for packets leaving the ed0 interface
> > > # to the DSL gateway address
> > > fwd 199.185.xx.xx tcp from any to 66.25.xx.0/24 80 out via ed0
> > >
> > > Also, make sure nat is working properly on rl0 interface and turn
> > > on logging to help you debug (both in natd and ipfw). What you
> > > have below looks as if it should work ok.
> >
>
> > I don't think that will do what he wants. You'll get asymetric routing
> > in this case. The packet will go to the 199.185.xx.xx gateway and out
> > that way, but it will come back the other way since it will have a
> > source address on 24.86.xx.xx. In fact, it's quite possible that the DSL
> > ISP will drop packets with a source address that doesn't belong to them.
>
> Um, I believe he is running nat on rl0 (his DSL). As the packet
> leaves rl0 it will be assigned the SRC IP of rl0.
That's the problem, it won't. When the packet hit the 'fwd' rule
above, it is accepted by the firewall and queued up on rl0. It doesn't
continue through or start again through the rules with the new
interface.
--
Crist J. Clark | cjclark@alum.mit.edu
| cjclark@jhu.edu
http://people.freebsd.org/~cjc/ | cjc@freebsd.org
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