routing table size

Paul Schultz pschultz at pschultz.com
Tue Jul 30 02:27:37 UTC 2002




On Mon, 29 Jul 2002, Richard A Steenbergen wrote:

> If someone has done an actual study of where these /24s (and probably /23s
> too) come from, please point it out. Until then, my money is on clueless
> redist connected/statics, large cable/dsl providers who announce a /24 per
> pop/city/whatever to their single transit provider, and general ignorance.

To ease my own curiousity I kludged together a script to look at how
much of /24 land is taken up by smalltimers announcing few prefixes, and
larger networks announcing many.  My last snapshot of the routing table is
from the end of june, so may be (very slightly) outdated.



Data from June 29, 2002

Total /24's: 61931
ASN's announcing /24's: 8645


Number of /24's announced by AS breakdown

/24's	ASN Count
=======	=========
1	3474
2	1662
3	740
4	533
5	377
6	236
7	203
8	164
9	113
10-14	421
15-19	184
20-29	199
30-39	101
40-49	57
50-59	41
60-69	29
70-79	21
80-89	12
90-99	11
100-149	20
150-199	17
200+	29

Those "basement multihomers" announcing 1-5 /24's only account for ~20% of
the total number of /24's out there.  Multihomers with slightly larger
basements (6-10 /24's) account for 10% of the total.  That leaves the
remaining 70% of /24's in the DFZ announced by people pushing out over 10
/24's from their AS.  Interpret however you will (I tend to lean
towards Richard's take on the situation.)



- Paul




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