Reaction of Stateless Address Autoconfiguration (SLAAC) to Flash- Renumbering Events
draft-ietf-v6ops-slaac-renum-05

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IPv6 Operations Working Group (v6ops)                            F. Gont
Internet-Draft                                              SI6 Networks
Intended status: Informational                                   J. Zorz
Expires: May 6, 2021                                            6connect
                                                            R. Patterson
                                                                  Sky UK
                                                        November 2, 2020

   Reaction of Stateless Address Autoconfiguration (SLAAC) to Flash-
                           Renumbering Events
                    draft-ietf-v6ops-slaac-renum-05

Abstract

   In scenarios where network configuration information related to IPv6
   prefixes becomes invalid without any explicit and reliable signaling
   of that condition (such as when a Customer Edge router crashes and
   reboots without knowledge of the previously-employed prefixes), nodes
   on the local network may continue using stale prefixes for an
   unacceptably long time (on the order of several days), thus resulting
   in connectivity problems.  This document describes this issue and
   discusses operational workarounds that may help to improve network
   robustness.  Additionally, it highlights areas where further work may
   be needed.

Status of This Memo

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   This Internet-Draft will expire on May 6, 2021.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Gont, et al.               Expires May 6, 2021                  [Page 1]
Internet-Draft       Reaction to Renumbering Events        November 2020

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Analysis of the Problem . . . . . . . . . . . . . . . . . . .   5
     2.1.  Use of Dynamic Prefixes . . . . . . . . . . . . . . . . .   5
     2.2.  Default Timer Values in IPv6 Stateless Address
           Autoconfiguration (SLAAC) . . . . . . . . . . . . . . . .   6
     2.3.  Recovering from Stale Network Configuration Information .   7
     2.4.  Lack of Explicit Signaling about Stale Information  . . .   7
     2.5.  Interaction Between DHCPv6-PD and SLAAC . . . . . . . . .   8
   3.  Operational Mitigations . . . . . . . . . . . . . . . . . . .   8
     3.1.  Stable Prefixes . . . . . . . . . . . . . . . . . . . . .   8
     3.2.  SLAAC Parameter Tweaking  . . . . . . . . . . . . . . . .   8
   4.  Future Work . . . . . . . . . . . . . . . . . . . . . . . . .   9
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  10
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Introduction

   IPv6 Stateless address autoconfiguration (SLAAC) [RFC4862] conveys
   information about prefixes to be employed for address configuration
   via Prefix Information Options (PIOs) sent in Router Advertisement
   (RA) messages.  IPv6 largely assumes prefix stability, with network
   renumbering only taking place in a planned manner, with old/stale
   prefixes being phased-out via reduced prefix lifetimes, and new
   prefixes (with longer lifetimes) being introduced at the same time.
   However, there are several scenarios that may lead to the so-called
   "flash-renumbering" events, where the prefix employed by a network
   suddenly becomes invalid and replaced by a new prefix.  In some of