Route table growth and hardware to the filter

Forrest forrest at
Sat Sep 8 21:47:02 UTC 2007

> From: owner-nanog at on behalf of Jared Mauch
> Sent: Sat 9/8/2007 8:17 AM
> To: William Allen Simpson
> Cc: nanog at
> Subject: Re: Route table growth and hardware to the filter
>         I think this is the most important point so far.  There are a lot
> of providers that think that their announcements need to be global
> to manage link/load balancing with their peers/upstreams.  Proper use
> of no-export (or similar) on the more specifics and the aggregate
> being sent out will reduce the global noise significantly.
>         Perhaps some of the providers to these networks will nudge them
> a bit more to use proper techniques.
>         I'm working on routing leaks this month.  There have already been
> over 2600 leak events today that could have been prevented with as-path
> filters of some sort, either on a cutomer or peer.  (this would obviously
> be in-addition to prefix-list filters).
>         - Jared

Maybe this is a dumb question, but why isn't there a BGP option to just
filter more specific routes that have the same AS path as the larger
aggregate?  This would allow the networks that announce more specifics for
traffic engineering to still accomplish that, while throwing away the
garbage from someone else that decides to announce their /19 as 33 routes
for no apparent reason.  Sure, this would fail if a network decided to 
only announce /24's for example without a larger aggregate, but how many 
networks are really doing that?


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