Internet Engineering Task Force (IETF) L. Vegoda
Request for Comments: 6441 ICANN
BCP: 171 November 2011
Category: Best Current Practice
ISSN: 2070-1721
Time to Remove Filters for Previously Unallocated IPv4 /8s
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 memo documents an Internet Best Current Practice.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
BCPs is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6441.
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
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
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RFC 6441 Remove /8 Filters November 2011
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 2
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 . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Prefixes That Should Not be Routed across the Internet . . . . 3
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 3
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 4
6.1. Normative References . . . . . . . . . . . . . . . . . . . 4
6.2. Informative References . . . . . . . . . . . . . . . . . . 4
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 5
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].
Martians [RFC1208] is a humorous term applied to packets that turn up
unexpectedly on the wrong network because of bogus routing entries.
It is also used as a name for a packet that has an altogether bogus
(non-registered or ill-formed) Internet address. Bogons [RFC3871]
are packets sourced from addresses that have not yet been allocated
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