[145021] in North American Network Operators' Group
Re: Strange static route
daemon@ATHENA.MIT.EDU (=?ISO-8859-1?Q?J=E9r=F4me_Nicolle?)
Sun Sep 25 13:42:22 2011
Date: Sun, 25 Sep 2011 19:42:09 +0200
From: =?ISO-8859-1?Q?J=E9r=F4me_Nicolle?= <jerome@ceriz.fr>
To: nanog@nanog.org
In-Reply-To: <85B958C1-E6DA-4FFC-B6E6-3962BFD3E424@antelope.net>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
Joel, Glen,
Le 24/09/2011 03:18, Joel Maslak a écrit :
> Protection against learning a bad default route through whatever
> routing protocol they are learning, since these two routes would
> be more specific than any typical default route. They probably
> got burned learning a default route.
Having a default route, or rather having a route to every possible
adresses, is required when you expunge your routing tables of some
prefixes yet you still wish to contact them relying on the next-hop's table.
Simple application is to filter incoming routes longer than /20 or /21
to free up some memory on your routers (reducing the global table from
377k to less than 100k routes is a nice perspective ;) )
But a default route is an obvious move and could easily be leeked by an
upstream, yet replacing yours if not properly filtered. So, using more
precise routes (/1s to /8s) helps avoiding these risks and yet lets you
roughly balance load to several gateways.
--
Jérôme Nicolle
