Date: Thu, 24 Jan 2002 15:29:25 +0100 From: "Reto Trachsel (NetModule)" <reto.trachsel@netmodule.com> To: "'cjclark@alum.mit.edu'" <cjclark@alum.mit.edu>, "'net@freebsd.org'" <net@freebsd.org> Subject: ICMP Redirect - does it not belong to the RFCs??? Message-ID: <F58DFF990DB0D411841D000102A7CD70090C15@tigris.pacific>
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Hi Crist and net-list
> I am not sure of the reason redirects are not sent for the default
> route. In your Stevens reference, he doesn't explain any reasoning for
> it? As you say, the comment I quoted goes wa-ay back to before the
> initial FreeBSD CVS import back to 4.4BSD or earlier. You might ask on
> freebsd-net@freebsd.org as to the reasoning behind this behavior.
It is described, that 4.4BSD Based Systems don't send ICMP-redirects if the
next Hop is the Routers default route. In my opinion, there's no reason for
this. Described into the RFC1812, a router must not send a redirect until
the three conditions are met. In this case, they are.
RFC1812 [Page82]:
Routers MUST NOT generate a Redirect Message unless all the following
conditions are met:
o The packet is being forwarded out the same physical interface that
it was received from,
--> Met, theres only one interface in the Company Network
o The IP source address in the packet is on the same Logical IP
(sub)network as the next-hop IP address, and
--> Met, 172.16.1.1 and 172.16.244.24 are both in the 172.16.0.0/16 Network
o The packet does not contain an IP source route option.
--> Met, sourcerouting is switches off on every host.
Is this a part in ICMP that no belong to the RFC-Standarts, or du you know
an exacter RFC?
Regards
Reto Trachsel
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