Address Allocation for Private Internets
RFC 1918
| Document | Type |
RFC - Best Current Practice
(February 1996; Errata)
Updated by RFC 6761
Also known as BCP 5
|
|
|---|---|---|---|
| Last updated | 2013-03-02 | ||
| Stream | IETF | ||
| Formats | plain text pdf html bibtex | ||
| Stream | WG state | (None) | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 1918 (Best Current Practice) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | (None) | ||
| Send notices to | (None) | ||
Network Working Group Y. Rekhter
Request for Comments: 1918 Cisco Systems
Obsoletes: 1627, 1597 B. Moskowitz
BCP: 5 Chrysler Corp.
Category: Best Current Practice D. Karrenberg
RIPE NCC
G. J. de Groot
RIPE NCC
E. Lear
Silicon Graphics, Inc.
February 1996
Address Allocation for Private Internets
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.
1. Introduction
For the purposes of this document, an enterprise is an entity
autonomously operating a network using TCP/IP and in particular
determining the addressing plan and address assignments within that
network.
This document describes address allocation for private internets. The
allocation permits full network layer connectivity among all hosts
inside an enterprise as well as among all public hosts of different
enterprises. The cost of using private internet address space is the
potentially costly effort to renumber hosts and networks between
public and private.
2. Motivation
With the proliferation of TCP/IP technology worldwide, including
outside the Internet itself, an increasing number of non-connected
enterprises use this technology and its addressing capabilities for
sole intra-enterprise communications, without any intention to ever
directly connect to other enterprises or the Internet itself.
The Internet has grown beyond anyone's expectations. Sustained
exponential growth continues to introduce new challenges. One
challenge is a concern within the community that globally unique
address space will be exhausted. A separate and far more pressing
concern is that the amount of routing overhead will grow beyond the
Rekhter, et al Best Current Practice [Page 1]
RFC 1918 Address Allocation for Private Internets February 1996
capabilities of Internet Service Providers. Efforts are in progress
within the community to find long term solutions to both of these
problems. Meanwhile it is necessary to revisit address allocation
procedures, and their impact on the Internet routing system.
To contain growth of routing overhead, an Internet Provider obtains a
block of address space from an address registry, and then assigns to
its customers addresses from within that block based on each customer
requirement. The result of this process is that routes to many
customers will be aggregated together, and will appear to other
providers as a single route [RFC1518], [RFC1519]. In order for route
aggregation to be effective, Internet providers encourage customers
joining their network to use the provider's block, and thus renumber
their computers. Such encouragement may become a requirement in the
future.
With the current size of the Internet and its growth rate it is no
longer realistic to assume that by virtue of acquiring globally
unique IP addresses out of an Internet registry an organization that
acquires such addresses would have Internet-wide IP connectivity once
the organization gets connected to the Internet. To the contrary, it
is quite likely that when the organization would connect to the
Internet to achieve Internet-wide IP connectivity the organization
would need to change IP addresses (renumber) all of its public hosts
(hosts that require Internet-wide IP connectivity), regardless of
whether the addresses used by the organization initially were
globally unique or not.
It has been typical to assign globally unique addresses to all hosts
that use TCP/IP. In order to extend the life of the IPv4 address
space, address registries are requiring more justification than ever
before, making it harder for organizations to acquire additional
address space [RFC1466].
Hosts within enterprises that use IP can be partitioned into three
categories:
Category 1: hosts that do not require access to hosts in other
enterprises or the Internet at large; hosts within
this category may use IP addresses that are
unambiguous within an enterprise, but may be
ambiguous between enterprises.
Show full document text