/8s and filtering

Harsha Narayan hnarayan at cs.ucsd.edu
Tue Dec 10 09:23:17 UTC 2002

  Currently APNIC's policy means that if an organization can fully use a
/26 (since 25% of /24=/26 and to satisfy the multihoming requirement the
organization will need to have a prefix advertised by two or more ISPs) it
can get a multihoming assignment from APNIC.

  If Class C /8s are over and ISPs maintain their filtering policies, the
bar would be raised to fully using a /24 instead (since 25% of /22 =
/24 and filtering in Class A is done at /22).

  8 of the 9 APNIC /8s are from the Class C space. Only one is from the
Class A space. However there are only three untouched /8s left in the
Class C space - 197/8, 222/8, 223/8.

  Actually, I wanted to know if the filtering policies will change to
accommodate this - i.e. will /24s be allowed in the Class A space?

  I was also curious about this - if I am a customer who wants to
multihome and can justify only a /24, I would go to an ISP
which has an allocation from the Class C space rather than one from the
Class A space. Do ISPs get to choose where the allocation comes from?


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