[arin-ppml] Rationale for /22

Jon Lewis jlewis at lewis.org
Tue Jul 28 15:20:25 EDT 2009

On Tue, 28 Jul 2009, Ted Mittelstaedt wrote:

> So, ISP's who filter set their boundary at /24 because it's a few
> bits off /20, to allow themselves a bit of wiggle room
> If you change it so that the bar is lowered to /24 then ISPs that
> filter will have to reduce down to /26 to be absolutely sure that
> they catch those clueless out there who get their /24 and subnet it
> into /25's or /26's and advertise those.

So many networks already filter with /24 being the cutoff that I think 
it'd be really hard for anyone to get full reachability announcing longer 
networks...even if ARIN were to make /24 the minimum regular allocation.

I don't buy the argument that ARIN handing out /24s will force me to 
accept /25's from the internet.  People get away with their TE or CF 
(Clue Free) deaggregation today because /24 somehow became accepted as the 
longest prefix acceptable to those who filter at all on prefix length. 
Those filters aren't going to change overnight...if at all, especially to 
allow longer than RIR minimums.

  Jon Lewis                   |  I route
  Senior Network Engineer     |  therefore you are
  Atlantic Net                |
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