Re: Did no one ever realize a Backup-Route with OpenBSD ???

[Vikram Kulkarni <vkulkarn@brownforces.org>]

On Wed, Dec 05, 2001 at 12:10:54AM -0800, David Terrell wrote:
> On Tue, Dec 04, 2001 at 08:39:11PM -0800, Frank Cusack wrote:
> > On Tue, Dec 04, 2001 at 05:24:54PM +0100, Toni Mueller wrote:
> > > btw, _why_ can't I have two (or 3 or 4) default routes, other than
> > > that nobody already implemented it?
> > 
> > No reason.  In fact it's a requirement to support multiple default
> > routes.  (RFC 1122, see par. 3.3.1.2 and 3.5)  There are issues
> > involved in determining which of multiple default routes to actually
> > use.
> 
> It is certainly not a requirement.  I challenge you to quote the text
> that specifies that behavior.

Network Working Group                    Internet Engineering Task Force
Request for Comments: 1122                             R. Braden, Editor
                                                            October 1989


        Requirements for Internet Hosts -- Communication Layers


Status of This Memo

   This RFC is an official specification for the Internet community.  It
   incorporates by reference, amends, corrects, and supplements the
   primary protocol standards documents relating to hosts.  Distribution
   of this document is unlimited.

Summary

   This is one RFC of a pair that defines and discusses the requirements
   for Internet host software.  This RFC covers the communications
   protocol layers: link layer, IP layer, and transport layer; its
   companion RFC-1123 covers the application and support protocols.

....

(Quote from the bottom of page 48 and top of page 49 of RFC1122, section
3.3.1.2)

     When there is no route cache entry for the destination host
     address (and the destination is not on the connected
     network), the IP layer MUST pick a gateway from its list of
     "default" gateways.  The IP layer MUST support multiple
     default gateways.

...

(or from the table on page 74 (column headers from page 72) of the same
RFC)

                                                 |        | | | |S| |
                                                 |        | | | |H| |F
                                                 |        | | | |O|M|o
                                                 |        | |S| |U|U|o
                                                 |        | |H| |L|S|t
                                                 |        |M|O| |D|T|n
                                                 |        |U|U|M| | |o
                                                 |        |S|L|A|N|N|t
                                                 |        |T|D|Y|O|O|t
FEATURE                                          |SECTION | | | |T|T|e
-------------------------------------------------|--------|-|-|-|-|-|--
...
 OUTING OUTBOUND DATAGRAMS:                      |        | | | | | |
...
  If no cache entry, use default gateway         |3.3.1.2 |x| | | | |
    Support multiple default gateways            |3.3.1.2 |x| | | | |


-Vik

-- 
vikram kulkarni          Of course, this being Perl, we could
vkulkarn@uiuc.edu        always take both approaches.
vkulkarn@brownforces.org                          -Larry Wall