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Date:      Tue, 20 Aug 1996 16:38:11 BST
From:      Michael Ryan <mike@NetworX.ie>
To:        Bill Fenner <fenner@parc.xerox.com>
Cc:        FreeBSD Support <questions@freebsd.org>
Subject:   Re: Does FBSD 2.1 honour ICMP redirects?
Message-ID:  <ECS9608201611B@NetworX.ie>

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On Tue, 20 Aug 1996 07:21:40 PDT Bill Fenner wrote:

> If you decided to start sending to 194.125.135.1 instead, would you
> still be sending down the PPP link or would you use another link?  If
> the PPP link, then you can't actually do anything (since the IP address
> of the router is only used to get the link layer address and there's
> only one machine on the other end of the PPP link).  If not, then
> RFC1122 says to ignore the redirect.
> 
> The router on the other end of your PPP link is asking you to do
> something impossible; it's asking you to not use it as a router to
> get to things that are beyond it.

Hi Bill,

Thanks for sticking with me on this one.
Your precise explanation has finally knocked on my head and made me
see the light.

Of course you're right -- the router IP address is only used to
get its link address.

Background:
My ISP had given me a gateway IP address, which I ignored for months.
I simply set my peer as the default router.
But, last night, while tcpdump'ing the PPP traffic, I noticed the
Redirects and got to thinking "yeah, I -should- be using the
gateway, after all".

This has raised two interesting things for me (the 2nd of which might
interest the group as a whole):
(a) Why do PC-based packages not grey-out the Gateway field when
configuring SLIP/PPP as the data link?
(b) I tried to install the gateway address given me by my ISP as the
default route and got a "Disc quota exceeded" message back from
"route".  Does this message indicate a bug/feature in FreeBSD's
handling of the situation?


Mike
<mike@NetworX.ie>
---






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