Network Working Group L. Vegoda
Internet-Draft ICANN
Intended status: BCP August 2, 2011
Expires: February 3, 2012
Time to Remove Filters for Previously Unallocated IPv4 /8s
draft-ietf-grow-no-more-unallocated-slash8s-02
Abstract
It has been common for network administrators to filter IP traffic
from and BGP prefixes of 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 packet and BGP prefix
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
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This Internet-Draft will expire on February 3, 2012.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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publication of this document. Please review these documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Traffic Filtering Options . . . . . . . . . . . . . . . . . . . 3
3.1. No Longer Filtering Based on Address Registration
Status . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.2. Continuing to Filter Traffic from Unallocated IPv4
Space . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Prefixes That Should Not be Routed Across the Internet . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . . 5
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 6
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1. Introduction
It has been common for network administrators to filter IP traffic
from and BGP prefixes of 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 packet and BGP prefix
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].
Bogons are packets sourced from addresses that have not yet been
allocated by IANA or the Regional Internet Registries (RIRs), or
addresses reserved for private or special use by RFCs [RFC3871].
Martians are packets with an altogether bogus (non-registered or ill-
formed) Internet address [RFC1208]. Bogons are referred to as "Dark
IP" in some circles.
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 bogon 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 packet and prefix filters based on the registration status
of the IPv4 address is a simple approach that will avoid blocking
legitimate Internet traffic. Network operators SHOULD remove both
ingress and egress packet filters as well as BGP prefix filters for
previously unallocated IPv4 /8s.
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3.2. Continuing to Filter Traffic from Unallocated IPv4 Space
Some network administrators might want to continue filtering
unallocated IPv4 addresses managed by the 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, Martians,
can deploy a set of packet and prefix filters designed to block
traffic from address blocks reserved for special purposes. These
are:
- 0.0.0.0/8 (Local identification) [RFC1122];
- 10.0.0.0/8 (Private use) [RFC1918];
- 127.0.0.0/8 (Loopback) [RFC1122];
- 169.254.0.0/16 (Link local) [RFC3927];
- 172.16.0.0/12 (Private use) [RFC1918];
- 192.0.2.0/24 (TEST-NET-1) [RFC5737];
- 192.168.0.0/16 (Private use) [RFC1918];
- 198.18.0.0/15 (Benchmark testing) [RFC2544];
- 198.51.100.0/24 (TEST-NET-2) [RFC5737];
- 203.0.113.0/24 (TEST-NET-3) [RFC5737];
- 224.0.0.0/4 (Multicast) [RFC5771]; and
- 240.0.0.0/4 (Future use) [RFC1112].
A full set of special use IPv4 addresses can be found in [RFC5735].
It includes prefixes that are intended for Internet use.
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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
7.1. Normative 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.
[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.
[RFC5771] Cotton, M., Vegoda, L., and D. Meyer, "IANA Guidelines for
IPv4 Multicast Address Assignments", BCP 51, RFC 5771,
March 2010.
7.2. Informative References
[RFC1208] Jacobsen, O. and D. Lynch, "Glossary of networking terms",
RFC 1208, March 1991.
[RFC2544] Bradner, S. and J. McQuaid, "Benchmarking Methodology for
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Network Interconnect Devices", RFC 2544, March 1999.
[RFC3871] Jones, G., "Operational Security Requirements for Large
Internet Service Provider (ISP) IP Network
Infrastructure", RFC 3871, September 2004.
[RFC5737] Arkko, J., Cotton, M., and L. Vegoda, "IPv4 Address Blocks
Reserved for Documentation", RFC 5737, January 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/
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