Dear fellow network operators, In July 2016, NTT Communications' Global IP Network AS2914 will deploy a new routing policy to block Bogon ASNs from its view of the default-free zone. This notification is provided as a courtesy to the network community at large. After the Bogon ASN filter policy has been deployed, AS 2914 will not accept route announcements from any eBGP neighbor which contains a Bogon ASN anywhere in the AS_PATH or its atomic aggregate attribute. The reasoning behind this policy is twofold: - Private or Reserved ASNs have no place in the public DFZ. Barring these from the DFZ helps improve accountability and dampen accidental exposure of internal routing artifacts. - All AS2914 devices support 4-byte ASNs. Any occurrence of "23456" in the DFZ is a either a misconfiguration or software issue. We are undertaking this effort to improve the quality of routing data as part of the global ecosystem. This should improve the security posture and provide additional certainty [1] to those undertaking network troubleshooting. Bogon ASNs are currently defined as following: 0 # Reserved RFC7607 23456 # AS_TRANS RFC6793 64496-64511 # Reserved for use in docs and code RFC5398 64512-65534 # Reserved for Private Use RFC6996 65535 # Reserved RFC7300 65536-65551 # Reserved for use in docs and code RFC5398 65552-131071 # Reserved 4200000000-4294967294 # Reserved for Private Use RFC6996 4294967295 # Reserved RFC7300 A current overview of what are considered Bogon ASNs is maintained at NTT's Routing Policies page [2]. The IANA Autonomous System Number Registry [3] is closely tracked and the NTT Bogon ASN definitions are updated accordingly. We encourage network operators to consider deploying similar policies. Configuration examples for various platforms can be found here [4]. NTT staff is monitoring current occurrences of Bogon ASNs in the routing system and reaching out to impacted parties on a weekly basis. Kind regards, Job Contact persons: Job Snijders <job@ntt.net>, Jared Mauch <jmauch@us.ntt.net>, NTT Communications NOC <noc@ntt.net> References: [1]: https://tools.ietf.org/html/draft-thomson-postel-was-wrong-00 [2]: http://www.us.ntt.net/support/policy/routing.cfm#bogon [3]: https://www.iana.org/assignments/as-numbers/as-numbers.xhtml [4]: http://as2914.net/bogon_asns/configuration_examples.txt