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Date:      Wed, 15 May 1996 13:47:47 -0600
From:      Nate Williams <nate@sri.MT.net>
To:        "Jonathan M. Bresler" <jmb@freefall.freebsd.org>
Cc:        nate@sri.MT.net (Nate Williams), questions@FreeBSD.ORG
Subject:   Re: Networking / Routing question
Message-ID:  <199605151947.NAA19867@rocky.sri.MT.net>
In-Reply-To: <199605151902.MAA13913@freefall.freebsd.org>
References:  <199605151555.JAA19142@rocky.sri.MT.net> <199605151902.MAA13913@freefall.freebsd.org>

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> > Background:
> > 
> > I will have a 32 host IP subnet, where I am using about 23 IP addresses
> > right now.  I'd like to add a firewall box on one end of the link
> > connected to router.  So, I have 2 machines on one-subnet, and the rest
> > of my network on the other subnet.
> >                           ethernet            ethernet
> > [ Internet ] <--> Router <--------> Firewall <--------> My machines
> > 
> > Since I only have 32 IP addresses available I don't want to waste any IP
> > addresses if I can help it, especially considering I expect to use a few
> > more addresses beyond the 23 I have now.
> > 
> > Since I have two ethernet segments, I must have two different subnets,
> > but I don't see any easy solution to the problem.  It would be nice if I
> > could use the ethernet segment as a point-point connection in this case
> > (for latency & BW ethernet is the cheapest way to go).
> > 
> > What would you suggest?
> 
> 	use rfc-1918 addresses on the segment between the router and the
> 	firewall.  keep all your 32 ip addresses for your hosts.
> 
> 	default route on the inside points to the firewall.  
> 
> 	default route on firewall points to the router.
> 	specific route for you 32 hosts points thru the internal
> 	interface of the firewall.
> 
> 	default route on the router points to the net.   
> 	router has specific route for your 32 hosts (hopefully
> 	consequetive on 5 bit boundary) pointing to the firewall.
> 
> 	as an aside this makes the internal interface for the router
> 	and the external interface of the firewall unaddressable
> 	from the internet.  that's a good thing!  if you must telnet
> 	to the firewall for configuation,( better to use the console
> 	or a serial line form your host) configure the firewall to
> 	accept telnet only from the OUTSIDE ethernet AND have the
> 	router block rfc-1918 addresses both inbound and outbound ;)

What a *great* idea!  John wins the big prize, which is dinner with me
next week. :)


Nate



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