[arin-announce] AS number change on 1 January 2009

Member Services info at arin.net
Thu Jul 24 14:30:02 EDT 2008

ARIN reminds the community that on 1 January 2009, all new Autonomous 
System Numbers (ASNs) issued will be four byte by default, unless 
otherwise 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).

Network operators may find themselves with a new four-byte ASN that 
upstream providers, peer networks, and customers cannot recognize. 
Without timely support from vendors, network operators risk having 
routers and network administration systems that will not accept the 
expanded four-byte number format. As such, ARIN urges operators to 
verify their vendors’ routers will support four-byte ASNs.

To help vendors understand how to provide four-byte ASN support and to 
help network operators find products that support four-byte ASNs, APNIC 
has set up a special website at http://icons.apnic.net.

Please contact hostmaster at arin.net if you have any questions concerning 
the ASN policy and four-byte ASNs.

Leslie Nobile
Director, Registration Services
American Registry for Internet Numbers (ARIN)

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