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Default Router Preferences and More-Specific Routes (RFC4191)

IP.com Disclosure Number: IPCOM000131702D
Original Publication Date: 2005-Nov-01
Included in the Prior Art Database: 2005-Nov-16
Document File: 16 page(s) / 35K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

R. Draves: AUTHOR [+2]

Abstract

This document describes an optional extension to Router Advertisement messages for communicating default router preferences and more- specific routes from routers to hosts. This improves the ability of hosts to pick an appropriate router, especially when the host is multi-homed and the routers are on different links. The preference values and specific routes advertised to hosts require administrative configuration; they are not automatically derived from routing tables.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 8% of the total text.

Network Working Group                                          R. Draves
Request for Comments: 4191                                     D. Thaler
Category: Standards Track                                      Microsoft
                                                           November 2005


          Default Router Preferences and More-Specific Routes

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This document describes an optional extension to Router Advertisement
   messages for communicating default router preferences and more-
   specific routes from routers to hosts.  This improves the ability of
   hosts to pick an appropriate router, especially when the host is
   multi-homed and the routers are on different links.  The preference
   values and specific routes advertised to hosts require administrative
   configuration; they are not automatically derived from routing
   tables.

1.  Introduction

   Neighbor Discovery [RFC2461] specifies a conceptual model for hosts
   that includes a Default Router List and a Prefix List.  Hosts send
   Router Solicitation messages and receive Router Advertisement
   messages from routers.  Hosts populate their Default Router List and
   Prefix List based on information in the Router Advertisement
   messages.  A conceptual sending algorithm uses the Prefix List to
   determine if a destination address is on-link and uses the Default
   Router List to select a router for off-link destinations.

   In some network topologies where the host has multiple routers on its
   Default Router List, the choice of router for an off-link destination
   is important.  In some situations, one router may provide much better
   performance than another for a destination.  In other situations,
   choosing the wrong router may result in a failure to communicate.
   (Section 5 gives specific examples of these scenarios.)

Draves & Thaler             Standards Track                     [Page 1]
RFC 4191      Router Preferences and More-Specific Routes  November 2005


   This document describes an optional extension to Neighbor Discovery
   Router Advertisement messages for communicating default router
   preferences and more-specific routes from routers to hosts.  This
   improves the ability of hosts to pick an appropriate router for an
  ...