Subject: RE: Some comments regarding draft-ietf-ipngwg-default-addr-select-05.txt

From: "Lori Napoli" <[email-masked]>
Date: Tue, 31 Jul 2001 12:15:33 -0400

If you have a multi-homed machine, and you don't have a route to a
particular destination, over which interface do you suggest the packet be
sent out over ?  This is in response to the following statement:

from RFC 2461:
    If the Default Router List is empty,
    the sender assumes that the destination is on-link.

Thanks
Lori

z/OS Communications Server Development - TCP/IP Stack

919-254-6146   T/L 8-444-6146
E-mail: [email-masked]

Pekka Savola <[email-masked]>@sunroof.eng.sun.com on 07/31/2001 08:09:21
AM

Sent by:  [email-masked]

To:   Erik Nordmark <[email-masked]>
cc:   <[email-masked]>, Stig Venaas <[email-masked]>,
      <[email-masked]>, <[email-masked]>
Subject:  RE: Some comments regarding
      draft-ietf-ipngwg-default-addr-select-05.txt

On Tue, 31 Jul 2001, Erik Nordmark wrote:

> > Your use of the terms on-link & default route together could be part
of the

> > confusion. For one, the concept of a default route applies to the next
hop

> > used when there is no obvious path for this destination, and for all
on-link

> > nodes there is an obvious path. For the other, the next hop for the
default

> > route is by definition on-link. I can't say without a picture what
that last

> > line means, but if an implementation believes that all addresses exist
on

> > its link, that implementation would appear to be broken.

> A node that conforms to RFC 2461 should treat all addresses as being on

> its link in one case - so I don't think the implementation is broken but

> correct.

> The text that Stig quoted from RFC 2461 says at the end

>    If the Default Router List is empty,

>    the sender assumes that the destination is on-link.

> In Unix implementations a possible implementation of this aspect

> is by creating this route

>   route add default <hostname> -interface

> where <hostname> is the hostname/IP address assigned to the node.

> One possible way of making the draft clearer would be to, instead of
using the

> implementation concept of a routing table, express the rule using

> the conceptual model in RFC 2461.

One other source of confusion might be that some implementations, when

setting routes manually (ie. not autoconfed), instead of setting _default_

route, prefer something like 2000::/3 so "illegal addresses" won't be

forwarded.

This is an effective default route AFAIS, but might not be one if you go

by the definition above.

--

Pekka Savola                 "Tell me of difficulties surmounted,

Netcore Oy                   not those you stumble over and fall"

Systems. Networks. Security.  -- Robert Jordan: A Crown of Swords

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