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Re: The Cidr Report

  • From: Michael Smith
  • Date: Sun Feb 13 18:08:22 2005

> From: "Warren Kumari, Ph.D, CCIE# 9190" <[email protected]>
> Date: Mon, 14 Feb 2005 10:14:38 -0500
> To: <[email protected]>
> Subject: Re: The Cidr Report
> Hash: SHA1
> On Feb 13, 2005, at 2:31 AM, Christopher L. Morrow wrote:
>> On Sat, 12 Feb 2005, Alexander Koch wrote:
>>> On Sat, 12 February 2005 14:58:42 +0000, Stephen J. Wilcox wrote:
>>>> From: "Stephen J. Wilcox" <[email protected]>
>>>> [...]   - would you agree that most of the poor deaggregating is not
>>>> intentional
>>>> ie that they're announcing their '16 class Cs' or historically had 2
>>>> /21s and
>>> Think about someone putting in a Null0 route and re-
>>> exporting stuff unconditionally, now after he originates
>>> his /19 he is then adding a /24 here, and a /25 there.
>>> Lack of experience, when you suggest to them they should
>>> remove these announcements they are afraid to change it,
>>> not understanding the implications, etc.
>>> Not to mention ppl using cisco and prefix lists, it is
>>> way too easy with cisco to say '/19 le 24', and then they
>>> use outbound prefix lists to their transit supplier
>>> (different, but related as I see it). Some transit ISPs
>>> use that a lot, and encourage the table growth.
>> There are some business reasons to de-aggregate. Look at some outages
>> caused by 'routing problems' (someone leaked my /24's to their peers,
>> peers, peer and my traffic got blackholed, because the public net only
>> knows me as a /20)
>> There are multiple reasons for deaggregation aside from 'dumb
>> operator',
>> some are even 'valid' if you look at them from the protection
>> standpoint.
>> -Chris
> That and the "I have 1 circuit to $good_provider and 1 circuit to
> $bad_provider and the only way I can make them balance is to split my
> space in half and announce more specifics out through each provider"
> argument. I have also often seen people do this without announcing the
> aggregate because   <some undefined bad thing> will happen, usually
> justified with much hand-waving.  The people who do this can usually
> not be reasoned with....
> It happens all the time...
> Warren.

So, say  I'm a provider that has received a /22 from UUNet (just for example
Chris :-) ) and I now get another transit provider and announce the /22
there.  So, I call UUNet and ask them to announce the /22 as a more specific
because I don't want a de-facto asymmetric configuration.  I *want* to get a
/20 from ARIN but my usage doesn't justify it yet, so I have to ride the /22
for some time.

By the long string of anecdotal attacks in the string to date, listing most
or all such providers as "bad" or "uninformed" how do you separate out those
providers who are legitimately interested in routing redundancy and not clue
impaired?  Do we just say "too bad, routing table bloat is more important
than your need for redundancy small guy!"?

I find it interesting that the general theme is one of "we're smarter than
they are because we aggregate more routes" as if clue were directly
correlated to aggregated routing announcements.


Michael K. Smith               NoaNet
206.219.7116 (work)         866.662.6380 (NOC)
[email protected]