AS Path Loops in practice ?

Stephen J. Wilcox steve at
Thu Dec 11 23:07:03 UTC 2003

> Most (all) large ISP's have a "customer ASN".  This allows a customer
> to connect in multiple places, run BGP, and get something approximating
> real redundancy to that carrier.  However, rather than allocate one
> ASN to each customer, all customers use the same "customer ASN".
> Yes, that means they must default to the provider (and/or have the
> provider provide a default route) to reach the other customers using
> this technique.

Perhaps I'm missing something having not done this myself but why arent the 
customers just using private ASNs? That would also remove the 'must default' 


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