Duplicate ASN Numbers

Organizations need an ASN to run BGP and route on the Internet. They are each assigned globally unique ASN(s) by their local Regional Internet Registry (RIR), who get them from IANA. A few weeks ago, the NANOG folks noticed that AS1712 had been registered by two different organizations (in France and Texas) that were both using the number to announce their separate network prefixes. ARIN issued a statement conveying that they were aware of the problem and were working to resolve it. We took a look at the data and found that AS1712 isn't the only dually-assigned ASN out there. In fact, even a root server didn't escape unscathed.

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