RFC 1519 (rfc1519) - Page 1 of 24
Classless Inter-Domain Routing (CIDR): an Address Assignment and Aggregation Strategy
Alternative Format: Original Text Document
Network Working Group V. Fuller
Request for Comments: 1519 BARRNet
Obsoletes: 1338 T. Li
Category: Standards Track cisco
J. Yu
MERIT
K. Varadhan
OARnet
September 1993
Classless Inter-Domain Routing (CIDR):
an Address Assignment and Aggregation Strategy
Status of this Memo
This RFC 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" for the standardization state and status
of this protocol. Distribution of this memo is unlimited.
Abstract
This memo discusses strategies for address assignment of the existing
IP address space with a view to conserve the address space and stem
the explosive growth of routing tables in default-route-free routers.
Table of Contents
Acknowledgements ................................................. 2
1. Problem, Goal, and Motivation ................................ 2
2. CIDR address allocation ...................................... 3
2.1 Aggregation and its limitations ............................. 3
2.2 Distributed network number allocation ....................... 5
3. Cost-benefit analysis ........................................ 6
3.1 Present allocation figures .................................. 7
3.2 Historic growth rates ....................................... 8
3.3 Detailed analysis ........................................... 8
3.3.1 Benefits of new addressing plan ........................... 9
3.3.2 Growth rate projections ................................... 9
4. Changes to inter-domain routing protocols and practices ...... 11
4.1 Protocol-independent semantic changes ....................... 11
4.2 Rules for route advertisement ............................... 11
4.3 How the rules work .......................................... 13
4.4 Responsibility for and configuration of aggregation ......... 14
4.5 Intra-domain protocol considerations ........................ 15
5. Example of new allocation and routing ........................ 15
Fuller, Li, Yu & Varadhan