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Date: Sat, 17 Mar 2001 10:28:25 -0600 (CST)
From: Nick Rogness <nick@rogness.net>
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Cc: Jeroen Ruigrok/Asmodai <asmodai@wxs.nl>
Subject: Re: same interface Route Cache
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On Sat, 17 Mar 2001, Wes Peters wrote:


	[Wes, if you get this, for some reason I can't send to your
	domain.]

	You are not understanding what I am trying to say.  Once again I'll try to
	clarify.  


> >         For dual-homed hosts, this is a problem because your packet gets
> >         sent out the default gateway, which may or may not get filtered
> >         upstream.  This is usually solved by running a routing deamon but
> >         most upstreams won't allow you to do that anyway (cable,dsl,etc).
> 
> If you have a dual-homed host that is simply routing an internal LAN to 
> the external network, you don't need anything other than a default route.
> If it's not bound for the internal network, it goes to the external 
> network, by definition.
> 

	Actually, that is not what "dual-homed" in the internet
	world means.  Dual homed is having 2 *public* Internet
	connections.  That's ISP lingo.


> I completely fail to see that you have actually stated a problem yet.
> 
> What exactly is the problem you think you're trying to solve here?
> 

	Consider the following.  I have to restate this every damn couple
	of weeks to get it through.  Here is the problem:


		ISP#1			ISP#2
		|			|
		|			|
		--- xl0 FreeBSD xl1 -----
			 xl2
			  |
			  |
			 Internal network
			  |
			  |
			  Machine 1

	
	Packet 1 comes in through ISP #2 network.  It comes into your
	internal network to machine 1.  Machine 1 replies to the
	packet...but where does it go?  It will exit through interface 
	to ISP #1 because of the default gateway.  It came in ISP #2 and
	left out ISP #1.  There is your problem.

	What if you are running nat in this case....your hosed.

	You can check out route-cache at Cisco's online site.  It may help
	to clarify as to why you would want to do this.

	If you check the -net mailing list this problem re-occurs over and
	over and over and over and over.  To which there is a work around
	that's a bit messy.



Nick Rogness <nick@rogness.net>
- Keep on routing in a Free World...  
  "FreeBSD: The Power to Serve!"






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