On 2 June 2016 at 20:56, Job Snijders <j...@ntt.net> wrote: > 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 at ntt.net>, Jared Mauch <jmauch at us.ntt.net>, > NTT Communications NOC <noc at 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
Hi Job, Good effort from NTT. I work for an access provider and we have rolled out the same policy already. There are definately valid arguments against this (I think) however I think the arguments for this approach outweigh them. It's good to see the larger carriers doing this, at $dayjob we have often see bogons IP prefixes coming from the larger carries (they aren't filtering their customer announcements) and the same goes for not dropping private ASNs in the path on prefixes receiveed from their customer announcements. This is the config we have used on IOS boxes; https://null.53bits.co.uk/index.php?page=asn-filtering I will fish out an IOS-XR config we have used too if anyone is interested in doing the same. Has anyone got a Junos config snippet they can share to do the same? If not I can splurge it out in the lab but I'm feeling Friday lazy. Cheers, James.
