routing table size

Tue Jul 30 03:36:14 UTC 2002

The slow-start scenario is valid, but only to a certain extent. My
company was a "slow-start" company, requesting and validating to
Management, ARIN, ISPs, and the guy working at the Quickie Mart. And
although we've managed to get to the point of a /19 at a time, we still
have a couple legacy /24s. What is one to do? Now, one network, one
contiguous AS, has 15 network advertisements ranging from /24 to /18
when it could be one /15 with another year or two to grow. But we can't
just pop off /15s to everyone who's promises to use it up, and I'm
certainly not going to persuade thousands of customers to migrate their
IPs to a new block.

But why I say it is only valid to a certain extent is that you only have
to "validate" a certain percentage of your existing IPs, that affords
larger companies to have more flexibility and thus get away from adding
/24s rather quickly.

Does someone have some perl script handy that can aggregate from a
hashlist dumped from router bgp output using NET::NETMASK?

(I'd do it myself, but ...well, I suk!)

JNULL PGP: 0x54B1A25C

"There are 10 types of people:
those that understand binary,
and those that do not.

-----Original Message-----
From: owner-nanog at merit.edu [mailto:owner-nanog at merit.edu] On Behalf Of
Phil Rosenthal
Sent: Monday, July 29, 2002 9:58 PM
To: 'Paul Schultz'; nanog at merit.edu
Subject: RE: routing table size

Now the question is, of that 70% figure, how much of that is
aggregateable?

--Phil

-----Original Message-----
From: owner-nanog at merit.edu [mailto:owner-nanog at merit.edu] On Behalf Of
Paul Schultz
Sent: Monday, July 29, 2002 10:28 PM
To: nanog at merit.edu
Subject: Re: routing table size

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is from the end of june, so may be (very slightly) outdated.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