Posted: Tue, 30 Dec 2008
Beginning on 1 January 2009, ARIN will be assigning four-byte Autonomous System Numbers (ASNs) by default, unless a 2-byte ASN is specifically requested. Following a globally coordinated policy, ARIN and all the Regional Internet Registries began allocating four-byte ASNs by request in January 2007; January 2009 marks the transition to allocating four-byte ASNs by default (see http://www.arin.net/policy/nrpm.html#five1).
Because this is a relatively new implementation, it is possible that some devices may not be able to recognize the new 4-byte ASNs. ARIN urges operators to verify that their routers and those of any transit providers or peers are ready and able to accept 4-byte ASNs.
Additional information about four-byte ASNs or how to request them can be found at:
Please contact firstname.lastname@example.org if you have any questions concerning the ASN policy and four-byte ASNs.
Director, Registration Services
American Registry for Internet Numbers (ARIN)