Network Working Group L. Vegoda
Internet-Draft ICANN
Intended status: Best Current Practice February 18, 2011
Expires: August 22, 2011

Time to Remove Filters for Previously Unallocated IPv4 /8s
draft-vegoda-no-more-unallocated-slash8s-01

Abstract

It has been common for network administrators to filter IP traffic coming from unallocated IPv4 address space. Now that there are no longer any unallocated IPv4 /8s, this practise is more complicated, fragile and expensive. Network administrators are advised to remove filters based on the registration status of the address space.

This document explains why any remaining filters for unallocated IPv4 /8s should now be removed on border routers and documents those IPv4 unicast prefixes that should not be routed across the public Internet.

Status of this Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/.

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This Internet-Draft will expire on August 22, 2011.

Copyright Notice

Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved.

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Table of Contents

1. Introduction

It has been common for network administrators to filter IP traffic coming from unallocated IPv4 address space. Now that there are no longer any unallocated IPv4 /8s, this practise is more complicated, fragile and expensive. Network administrators are advised to remove filters based on the registration status of the address space.

This document explains why any remaining filters for unallocated IPv4 /8s should now be removed on border routers and documents those IPv4 unicast prefixes that should not be routed across the public Internet.

2. Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14, RFC 2119 [RFC2119].

3. Traffic Filtering Options

3.1. No Longer Filtering Based on Address Registration Status

Network administrators who implemented filters for unallocated IPv4 /8s did so in the knowledge that those /8s were not a legitimate source of traffic on the Internet and that there was a small number of filters to implement. Now that there are no longer any unallocated unicast IPv4 /8s, there will be legitimate Internet traffic coming from all unicast /8s that are not reserved for special purposes in an RFC.

Removing ingress filters based on the registration status of the IPv4 address is a simple approach that will avoid blocking legitimate Internet traffic.

3.2. Continuing to Filter Traffic from Unallocated IPv4 Space

Some network administrators might want to continue filtering unallocated IPv4 addresses managed by the Regional Internet Registries (RIRs). This requires significantly more granular ingress filters and the highly dynamic nature of the RIRs' address pools means that filters need to be updated on a daily basis to avoid blocking legitimate incoming traffic.

4. Prefixes That Should Not be Routed Across the Internet

Network operators who only wish to filter traffic originating from addresses that should never be routed across the Internet can deploy a set of ingress filters designed to block traffic from address blocks reserved for special purposes. These are:

A full set of special use IPv4 addresses can be found in [RFC5735]. It includes prefixes that are intended for Internet use.

5. Security Considerations

The cessation of filters based on unallocated IPv4 /8 allocations is an evolutionary step towards reasonable security filters. While these filters are no longer necessary, and in fact harmful, this does not obviate the need to continue other security solutions. These other solutions are as necessary today as they ever were.

6. IANA Considerations

This document makes no request of IANA.

7. References

[RFC1112] Deering, S., "Host extensions for IP multicasting", STD 5, RFC 1112, August 1989.
[RFC1122] Braden, R., "Requirements for Internet Hosts - Communication Layers", STD 3, RFC 1122, October 1989.
[RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G. and E. Lear, "Address Allocation for Private Internets", BCP 5, RFC 1918, February 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2544] Bradner, S. and J. McQuaid, "Benchmarking Methodology for Network Interconnect Devices", RFC 2544, March 1999.
[RFC3927] Cheshire, S., Aboba, B. and E. Guttman, "Dynamic Configuration of IPv4 Link-Local Addresses", RFC 3927, May 2005.
[RFC5735] Cotton, M. and L. Vegoda, "Special Use IPv4 Addresses", BCP 153, RFC 5735, January 2010.
[RFC5737] Arkko, J., Cotton, M. and L. Vegoda, "IPv4 Address Blocks Reserved for Documentation", RFC 5737, January 2010.
[RFC5771] Cotton, M., Vegoda, L. and D. Meyer, "IANA Guidelines for IPv4 Multicast Address Assignments", BCP 51, RFC 5771, March 2010.

Appendix A. Acknowledgments

Thanks are owed to Kim Davies, Terry Manderson, Dave Piscitello and Joe Abley for helpful advice on how to focus this document. Thanks also go to Andy Davidson, Philip Smith and Rob Thomas for early reviews and suggestions for improvements to the text and Carlos Pignataro for his support and comments.

Author's Address

Leo Vegoda Internet Corporation for Assigned Names and Numbers 4676 Admiralty Way, Suite 330 Marina del Rey, CA, 90292 United States of America Phone: +1-310-823-9358 EMail: leo.vegoda@icann.org URI: http://www.iana.org/