RFC 2317 (rfc2317) - Page 1 of 10

Classless IN-ADDR

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Network Working Group                                         H. Eidnes
Request for Comments: 2317                                 SINTEF RUNIT
BCP: 20                                                     G. de Groot
Category: Best Current Practice          Berkeley Software Design, Inc.
                                                               P. Vixie
                                           Internet Software Consortium
                                                             March 1998


                   Classless IN-ADDR.ARPA delegation

Status of this Memo

   This document specifies an Internet Best Current Practices for the
   Internet Community, and requests discussion and suggestions for
   improvements.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (1998).  All Rights Reserved.

2. Introduction

   This document describes a way to do IN-ADDR.ARPA delegation on non-
   octet boundaries for address spaces covering fewer than 256
   addresses.  The proposed method should thus remove one of the
   objections to subnet on non-octet boundaries but perhaps more
   significantly, make it possible to assign IP address space in smaller
   chunks than 24-bit prefixes, without losing the ability to delegate
   authority for the corresponding IN-ADDR.ARPA mappings.  The proposed
   method is fully compatible with the original DNS lookup mechanisms
   specified in [1], i.e. there is no need to modify the lookup
   algorithm used, and there should be no need to modify any software
   which does DNS lookups.

   The document also discusses some operational considerations to
   provide some guidance in implementing this method.

3. Motivation

   With the proliferation of classless routing technology, it has become
   feasible to assign address space on non-octet boundaries.  In case of
   a very small organization with only a few hosts, assigning a full
   24-bit prefix (what was traditionally referred to as a "class C
   network number") often leads to inefficient address space
   utilization.





Eidnes, et. al.          Best Current Practice
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