From owner-freebsd-net  Thu Oct 26 21:47:53 2000
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To: Nick Rogness <nick@rapidnet.com>
Cc: "Richard A. Steenbergen" <ras@e-gerbil.net>,
	"Ron 'The InSaNe One' Rosson" <insane@lunatic.oneinsane.net>,
	freebsd-net@FreeBSD.ORG
Subject: Re: Multihomed Routing 
In-reply-to: Your message of "Thu, 26 Oct 2000 19:56:36 MDT."
             <Pine.BSF.4.21.0010261948400.29371-100000@rapidnet.com> 
Date: Fri, 27 Oct 2000 00:47:43 -0400
From: Bakul Shah <bakul@torrentnet.com>
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> 	Sure that will work.  However, consider the following:
> 
> 
> 
> 				Network1 (2000 IP's)
> 				|
> 				|
> 			   |---Router1
> 			   |
> 		machine1---|
> 			   |
> 			   |---Router2 (default gateway)
> 
> 	What happens to Router2 when machine1 is trying to access the IP's
> 	on Router1's network?  Router2 gets clogged down sending ICMP
> 	redirects for Router1 back to machine1.  The problem grows
> 	exponetially[spelling] when you add more machines to the same
> 	network machine1 is on.

Unless I am missing something the redirect traffic won't
grow exponentially.  Machine1 will get one redirect per
destination D and will switch its route to D to go via
Router1.  From then on it won't bother Router2 for D.  So the
total number of redirects is

    SUM(H[i]) for i = 1..number of servers,
	where H[i] == number of hosts server i talks to.

So yes, there is some extra traffic but assuming your local
network is far faster than your external connections this
shouldn't be a problem (unless you send only a single packet
to each destination).

> 	Keep in mind, it only updates routes on machine1 for that IP...not
> 	the subnet...at least on WInBlows.

As per RFC 1812 a router will only generate host redirects.


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