RFC 2526 (rfc2526) - Page 1 of 7

Reserved IPv6 Subnet Anycast Addresses

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Network Working Group                                         D. Johnson
Request for Comments: 2526                    Carnegie Mellon University
Category: Standards Track                                     S. Deering
                                                     Cisco Systems, Inc.
                                                              March 1999


                 Reserved IPv6 Subnet Anycast Addresses

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 (1999).  All Rights Reserved.

Abstract

   The IP Version 6 addressing architecture defines an "anycast" address
   as an IPv6 address that is assigned to one or more network interfaces
   (typically belonging to different nodes), with the property that a
   packet sent to an anycast address is routed to the "nearest"
   interface having that address, according to the routing protocols'
   measure of distance.  This document defines a set of reserved anycast
   addresses within each subnet prefix, and lists the initial allocation
   of these reserved subnet anycast addresses.

1. Introduction

   IP Version 6 (IPv6) defines a new type of address, known as an
   "anycast" address, that allows a packet to be routed to one of a
   number of different nodes all responding to the same address [2, 3].
   The anycast address may be assigned to one or more network interfaces
   (typically on different nodes), with the network delivering each
   packet addressed to this address to the "nearest" interface based on
   the notion of "distance" determined by the routing protocols in use.

   The uses of anycast addresses are still evolving, but such addresses
   offer the potential for a number of important services [5, 6].  For
   example, an anycast address may be used to allow nodes to access one
   of a collection of servers providing a well-known service, without
   manual configuration in each node of the list of servers; or an




Johnson & Deering           Standards Track
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