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Time to Remove Filters for Previously Unallocated IPv4 /8s
RFC 6441

Document type: RFC - Best Current Practice (November 2011; No errata)
Also Known As BCP 171
Document stream: IETF
Last updated: 2013-03-02
Other versions: plain text, pdf, html

IETF State: WG Document
Consensus: Unknown
Document shepherd: No shepherd assigned

IESG State: RFC 6441 (Best Current Practice)
Responsible AD: Ron Bonica
Send notices to: grow-chairs@tools.ietf.org, draft-ietf-grow-no-more-unallocated-slash8s@tools.ietf.org

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

Vegoda                    Best Current Practice                 [Page 1]
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

Vegoda                    Best Current Practice                 [Page 2]
RFC 6441                    Remove /8 Filters              November 2011

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