What is the most standard subnet length on internet

Scott Morris swm at emanon.com
Wed Dec 24 13:03:38 CST 2008


In case anyone cares...  From my router's perspective:

/1	0
/2	0
/3	0
/4	0
/5	0
/6	0
/7	0
/8	20
/9	9
/10	20
/11	53
/12	159
/13	310
/14	560
/15	1,096
/16	10,235
/17	4,461
/18	7,593
/19	16,284
/20	19,075
/21	18,598
/22	23,941
/23	24,615
/24	144,832
/25	1
/26	1
/27	1
/28	3
/29	1
/30	1,234
/31	13
/32	23

Total	273,138

No, I wasn't bored enough to count them by hand.  JUNOS has a "count"
feature.  :)

Scott 

-----Original Message-----
From: Jon Lewis [mailto:jlewis at lewis.org] 
Sent: Monday, December 22, 2008 8:12 PM
To: Seth Mattinen
Cc: NANOG list
Subject: Re: What is the most standard subnet length on internet

On Mon, 22 Dec 2008, Seth Mattinen wrote:

> Anyone running a platform that can't take a full table would apply 
> such a filter to weed out anyone who likes to announce all of their 
> space as /24's for "traffic engineering". If one does that and doesn't 
> announce the aggregate as well, one could find themselves facing random
black holes.

There's no "if" about it.  Months ago when I and others were looking into
this, we found plenty of examples of networks with /19s, /20s, etc. 
announcing only the /24 deaggregates.  If you plan to filter these people
and have customers to answer to, you'll need to point default at someone
who's not filtering them.

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