Strange static route

Jérôme Nicolle jerome at ceriz.fr
Sun Sep 25 12:42:09 CDT 2011


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



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