On Sun, 13 Feb 2005, Michael Smith wrote:
From: "Warren Kumari, Ph.D, CCIE# 9190" <warren@kumari.net> Date: Mon, 14 Feb 2005 10:14:38 -0500 To: <nanog@merit.edu> Subject: Re: The Cidr Report
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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@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.
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.
Hi Mike, this isnt the scenario being discussed. The scenario of issue is where you get your /22 from UUNET and announce 4x /24 ie based on what ips you have you choose to announce more than the minimum to make them routable
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!"?
As I say this isnt the issue here, altho what you suggest would be an example of further aggregation that i personally think is extreme. Multihoming must be possible and a hierarchical structure to the internet is not appropriate.
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.
Well, there does seem to be some loose correlation it cant be denied... (counter examples not required, we know they exist) Steve