ARIN allocating /20 netblocks?

Patrick W. Gilmore patrick at
Fri May 15 19:46:54 UTC 1998

At 12:36 PM 5/15/98 PDT, Mark D. Nagel wrote:
>One of our customers was recently allocated a /20 netblock from ARIN. 
>I had just been ass-u-ming it was a /19 until I cross-checked our
>announcement update with the request from the customer.  Is this a
>change in policy (I thought they only allocated /19 or bigger) or did
>I miss something?  If the former, are NSPs like Sprint planning to
>update filters to route these new smaller blocks?

Check the ARIN page,

Essentially, ARIN allocates a /21 or /20 of a "Reserved" /19.  When our
downstream got a /19 from ARIN, he announced the full /19 to defeat the
Draconian Sprint 112 filters and copy-cats.

Check with your downstream.  They probably have a reserved /19 they can

And, of course, double-check with ARIN as this isn't my customer we're
talking about. ;)

>Mark D. Nagel <nagel at>, CCIE #3177


Patrick W. Gilmore                      voice: +1-650-482-2840
Director of Operations, CCIE #2983        fax: +1-650-482-2844
              "Tomorrow's Performance.... Today"

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