Date: Thu, 29 Jun 1995 16:23:38 +0100 (BST) From: Paul Richards <paul@lambda.demon.co.uk> To: wollman@halloran-eldar.lcs.mit.edu (Garrett Wollman) Cc: nate@sneezy.sri.com, wollman@halloran-eldar.lcs.mit.edu, rgrimes@gndrsh.aac.dev.com, jkh@freebsd.org, FreeBSD-current@freebsd.org Subject: Re: Paul Richards: sysconfig routed setting Message-ID: <199506291523.QAA13229@freebsd.netcraft.co.uk> In-Reply-To: <9506281839.AA01339@halloran-eldar.lcs.mit.edu> from "Garrett Wollman" at Jun 28, 95 02:39:20 pm
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In reply to Garrett Wollman who said
>
> <<On Wed, 28 Jun 1995 12:37:45 -0600, nate@sneezy.sri.com (Nate Williams) said:
>
> > Ethernet =
> > SLIP/PPP *
>
> > machine-A<=>machine-B<=>machine-C<*>{internet}
> > ^
> > *
> > v
> > Nate's box
>
>
> Machine A is a router. It runs a routing protocol.
I'm not even sure that is necessary, since Nate's box is the only machine
hanging off the slip link proxy ARP would be a better set up.
Machine A proxy-ARP's Nate's address so that Nate's box appears
to be on the ethernet. Nate's box will obvious have a default route
to machine A and if A has appropriate netmasks for it's two interfaces
it will know that packet's for Nate's box go out the slip link.
It's is a router but it wouldn't be necessary to run a routing deamon on it.
>
> > With your assumption, machine B does is not running any routing
> > software, so therefore it does not know to send packets to machine A in
> > order to get to my machine.
>
> Machine B has a default router R. R and A exchange routing protocol
> packets to inform each other of their locations. When machine B sends
> a packet for `Nate's box' to R, R sends an ICMP redirect back to B
> telling it that `Nate's box' should be reached by way of A, and B
> sends future packets directly.
If A does proxy ARP then B will send packets to A and A will forward them
across the slip link without having to run a routed.
This is an exception though and Garrett's description above expalins the
more general case, if for example there were several boxes off the slip
link to Nate's machine.
We're getting off the point a bit though, which is whether routed should
be enabled by default. I still think the only time it should be run is
if the box has a real need to exchange RIP info with other routers and in
those cases the admin will know enough to make that decision.
For most boxes it's not needed.
--
Paul Richards, Bluebird Computer Systems. FreeBSD core team member.
Internet: paul@FreeBSD.org, http://www.freebsd.org/~paul
Phone: 0370 462071 (Mobile), +44 1222 457651 (home)
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