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Checking references for intended status: Best Current Practice ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Downref: Normative reference to an Informational RFC: RFC 2544 ** Obsolete normative reference: RFC 5735 (Obsoleted by RFC 6890) ** Downref: Normative reference to an Informational RFC: RFC 5737 Summary: 3 errors (**), 0 flaws (~~), 5 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group L. Vegoda 3 Internet-Draft ICANN 4 Intended status: BCP March 12, 2011 5 Expires: September 13, 2011 7 Time to Remove Filters for Previously Unallocated IPv4 /8s 8 draft-ietf-grow-no-more-unallocated-slash8s-00 10 Abstract 12 It has been common for network administrators to filter IP traffic 13 coming from unallocated IPv4 address space. Now that there are no 14 longer any unallocated IPv4 /8s, this practise is more complicated, 15 fragile and expensive. Network administrators are advised to remove 16 filters based on the registration status of the address space. 18 This document explains why any remaining filters for unallocated IPv4 19 /8s should now be removed on border routers and documents those IPv4 20 unicast prefixes that should not be routed across the public 21 Internet. 23 Status of this Memo 25 This Internet-Draft is submitted in full conformance with the 26 provisions of BCP 78 and BCP 79. 28 Internet-Drafts are working documents of the Internet Engineering 29 Task Force (IETF). Note that other groups may also distribute 30 working documents as Internet-Drafts. The list of current Internet- 31 Drafts is at http://datatracker.ietf.org/drafts/current/. 33 Internet-Drafts are draft documents valid for a maximum of six months 34 and may be updated, replaced, or obsoleted by other documents at any 35 time. It is inappropriate to use Internet-Drafts as reference 36 material or to cite them other than as "work in progress." 38 This Internet-Draft will expire on September 13, 2011. 40 Copyright Notice 42 Copyright (c) 2011 IETF Trust and the persons identified as the 43 document authors. All rights reserved. 45 This document is subject to BCP 78 and the IETF Trust's Legal 46 Provisions Relating to IETF Documents 47 (http://trustee.ietf.org/license-info) in effect on the date of 48 publication of this document. Please review these documents 49 carefully, as they describe your rights and restrictions with respect 50 to this document. Code Components extracted from this document must 51 include Simplified BSD License text as described in Section 4.e of 52 the Trust Legal Provisions and are provided without warranty as 53 described in the Simplified BSD License. 55 Table of Contents 57 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 58 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 59 3. Traffic Filtering Options . . . . . . . . . . . . . . . . . . . 3 60 3.1. No Longer Filtering Based on Address Registration 61 Status . . . . . . . . . . . . . . . . . . . . . . . . . . 3 62 3.2. Continuing to Filter Traffic from Unallocated IPv4 63 Space . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 64 4. Prefixes That Should Not be Routed Across the Internet . . . . 4 65 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 4 66 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4 67 7. Normative References . . . . . . . . . . . . . . . . . . . . . 5 68 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 5 69 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 5 71 1. Introduction 73 It has been common for network administrators to filter IP traffic 74 coming from unallocated IPv4 address space. Now that there are no 75 longer any unallocated IPv4 /8s, this practise is more complicated, 76 fragile and expensive. Network administrators are advised to remove 77 filters based on the registration status of the address space. 79 This document explains why any remaining filters for unallocated IPv4 80 /8s should now be removed on border routers and documents those IPv4 81 unicast prefixes that should not be routed across the public 82 Internet. 84 2. Terminology 86 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 87 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 88 document are to be interpreted as described in BCP 14, RFC 2119 89 [RFC2119]. 91 3. Traffic Filtering Options 93 3.1. No Longer Filtering Based on Address Registration Status 95 Network administrators who implemented filters for unallocated IPv4 96 /8s did so in the knowledge that those /8s were not a legitimate 97 source of traffic on the Internet and that there was a small number 98 of filters to implement. Now that there are no longer any 99 unallocated unicast IPv4 /8s, there will be legitimate Internet 100 traffic coming from all unicast /8s that are not reserved for special 101 purposes in an RFC. 103 Removing ingress filters based on the registration status of the IPv4 104 address is a simple approach that will avoid blocking legitimate 105 Internet traffic. 107 3.2. Continuing to Filter Traffic from Unallocated IPv4 Space 109 Some network administrators might want to continue filtering 110 unallocated IPv4 addresses managed by the Regional Internet 111 Registries (RIRs). This requires significantly more granular ingress 112 filters and the highly dynamic nature of the RIRs' address pools 113 means that filters need to be updated on a daily basis to avoid 114 blocking legitimate incoming traffic. 116 4. Prefixes That Should Not be Routed Across the Internet 118 Network operators who only wish to filter traffic originating from 119 addresses that should never be routed across the Internet can deploy 120 a set of ingress filters designed to block traffic from address 121 blocks reserved for special purposes. These are: 123 - 0.0.0.0/8 (Local identification) [RFC1122]; 125 - 10.0.0.0/8 (Private use) [RFC1918]; 127 - 127.0.0.0/8 (Loopback) [RFC1122]; 129 - 169.254.0.0/16 (Link local) [RFC3927]; 131 - 172.16.0.0/12 (Private use) [RFC1918]; 133 - 192.0.2.0/24 (TEST-NET-1) [RFC5737]; 135 - 192.168.0.0/16 (Private use) [RFC1918]; 137 - 198.18.0.0/15 (Benchmark testing) [RFC2544]; 139 - 198.51.100.0/24 (TEST-NET-2) [RFC5737]; 141 - 203.0.113.0/24 (TEST-NET-3) [RFC5737]; 143 - 224.0.0.0/4 (Multicast) [RFC5771]; and 145 - 240.0.0.0/4 (Future use) [RFC1112]. 147 A full set of special use IPv4 addresses can be found in [RFC5735]. 148 It includes prefixes that are intended for Internet use. 150 5. Security Considerations 152 The cessation of filters based on unallocated IPv4 /8 allocations is 153 an evolutionary step towards reasonable security filters. While 154 these filters are no longer necessary, and in fact harmful, this does 155 not obviate the need to continue other security solutions. These 156 other solutions are as necessary today as they ever were. 158 6. IANA Considerations 160 This document makes no request of IANA. 162 7. Normative References 164 [RFC1112] Deering, S., "Host extensions for IP multicasting", STD 5, 165 RFC 1112, August 1989. 167 [RFC1122] Braden, R., "Requirements for Internet Hosts - 168 Communication Layers", STD 3, RFC 1122, October 1989. 170 [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and 171 E. Lear, "Address Allocation for Private Internets", 172 BCP 5, RFC 1918, February 1996. 174 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 175 Requirement Levels", BCP 14, RFC 2119, March 1997. 177 [RFC2544] Bradner, S. and J. McQuaid, "Benchmarking Methodology for 178 Network Interconnect Devices", RFC 2544, March 1999. 180 [RFC3927] Cheshire, S., Aboba, B., and E. Guttman, "Dynamic 181 Configuration of IPv4 Link-Local Addresses", RFC 3927, 182 May 2005. 184 [RFC5735] Cotton, M. and L. Vegoda, "Special Use IPv4 Addresses", 185 BCP 153, RFC 5735, January 2010. 187 [RFC5737] Arkko, J., Cotton, M., and L. Vegoda, "IPv4 Address Blocks 188 Reserved for Documentation", RFC 5737, January 2010. 190 [RFC5771] Cotton, M., Vegoda, L., and D. Meyer, "IANA Guidelines for 191 IPv4 Multicast Address Assignments", BCP 51, RFC 5771, 192 March 2010. 194 Appendix A. Acknowledgments 196 Thanks are owed to Kim Davies, Terry Manderson, Dave Piscitello and 197 Joe Abley for helpful advice on how to focus this document. Thanks 198 also go to Andy Davidson, Philip Smith and Rob Thomas for early 199 reviews and suggestions for improvements to the text and Carlos 200 Pignataro for his support and comments. 202 Author's Address 204 Leo Vegoda 205 Internet Corporation for Assigned Names and Numbers 206 4676 Admiralty Way, Suite 330 207 Marina del Rey, CA 90292 208 United States of America 210 Phone: +1-310-823-9358 211 Email: leo.vegoda@icann.org 212 URI: http://www.iana.org/