Router Renumbering Guide
RFC 2072

Document Type RFC - Informational (January 1997; No errata)
Updated by RFC 4192
Last updated 2013-03-02
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Network Working Group                                       H. Berkowitz
Request for Comments: 2072                             PSC International
Category: Informational                                     January 1997

                        Router Renumbering Guide

Status of this Memo

   This memo provides information for the Internet community.  This memo
   does not specify an Internet standard of any kind.  Distribution of
   this memo is unlimited.

Abstract

   IP addresses currently used by organizations are likely to undergo
   changes in the near to moderate term.  Change can become necessary
   for a variety of reasons, including enterprise reorganization,
   physical moves of equipment, new strategic relationships, changes in
   Internet Service Providers (ISP), new applications, and the needs of
   global Internet connectivity.  Good IP address management may in
   general simplify continuing system administration; a good renumbering
   plan is also a good numbering plan.    Most actions taken to ease
   future renumbering will ease routine network administration.

   Routers are the components that interconnect parts of the IP address
   space identified by unique prefixes.  Obviously, they will be
   impacted by renumbering.  Other interconnection devices, such as
   bridges, layer 2 switches (i.e., specialized bridges), and ATM
   switches may be affected by renumbering.  The interactions of these
   lower-layer interconnection devices with routers must be considered
   as part of a renumbering effort.

   Routers interact with numerous network infrastructure servers,
   including DNS and SNMP.  These interactions, not just the pure
   addressing and routing structure, must be considered as part of
   router renumbering.

Berkowitz                    Informational                      [Page 1]
RFC 2072                Router Renumbering Guide            January 1997

Table of Contents

   1.   Introduction . . . . . . . . . . . . . . . . . . . . . . . .  2
   2.   Disclaimer . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.   Motivations for Renumbering  . . . . . . . . . . . . . . . .  3
   4.   Numbering and Renumbering. . . . . . . . . . . . . . . . . .  9
   5.   Moving toward a Renumbering-Friendly Enterprise. . . . . . . 13
   6.   Potential Pitfalls in Router Renumbering.  .  .  . . . . . . 20
   7.   Tools and Methods for Renumbering  . .  .  . . . . . . . . . 25
   8.   Router Identifiers . . . . . . . . . . . . . . . . . . . . . 29
   9.   Filtering and Access Control . . . . . . . . . . . . . . . . 35
  10.   Interior Routing . . . . . . . . . . . . . . . . . . . . . . 37
  11.   Exterior Routing . . . . . . . . . . . . . . . . . . . . . . 39
  12.   Network Management . . . . . . . . . . . . . . . . . . . . . 41
  13.   IP and Protocol Encapsulation  . . . . . . . . . . . . . . . 43
  14.   Security Considerations. . . . . . . . . . . . . . . . . . . 44
  15.   Planning and Implementing the Renumbering  . . . . . . . . . 44
  16.   Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 46
  17.   References . . . . . . . . . . . . . . . . . . . . . . . . . 47
  18.   Author's Address . . . . . . . . . . . . . . . . . . . . . . 48

1.  Introduction

   Organizations can decide to renumber part or all of their IP address
   space for a variety of reasons.  Overall motivations for renumbering
   are discussed in [RFC2071].  This document deals with the router-
   related aspects of a renumbering effort, once the decision to
   renumber has been made.

   A renumbering effort must be well-planned if it is to be successful.
   This document deals with planning and implementation guidelines for
   the interconnection devices of an enterprise. Of these devices,
   routers have the clearest association with the IP numbering plan.

   Planning begins with understanding the problem to be solved.  Such
   understanding includes both the motivation for renumbering and the
   technical issues involved in renumbering.

      1.  Begin with a short and clear statement of the reason to
          renumber.  Section 3  of this document discusses common
          reasons.

      2.  Understand the principles of numbering in the present and
          planned environments.  Section 4 reviews numbering and
          suggests a method for describing the scope of renumbering.

Berkowitz                    Informational                      [Page 2]
RFC 2072                Router Renumbering Guide            January 1997

      3.  Before the actual renumbering, it can be useful to evolve
          the current environment and current numbering to a more
          "renumbering-friendly" system.  Section 5 discusses ways to
          introduce renumbering friendliness into current systems.

      4.  Be aware of potential pitfalls.  These are discussed in
          Section 6.

      5.  Identify potential requirements for tools, discussed in
          Section 7.
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