The Cidr Report

Mon Feb 14 15:14:38 UTC 2005

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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" <steve at telecomplete.co.uk>
>>> [...]   - 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.

>
>
- -- 
"He who laughs last, thinks slowest."
	-- Anonymous
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