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Mike Hammett
Intelligent Computing Solutions
http://www.ics-il.com

Midwest-IX
http://www.midwest-ix.com

From: "Elmar K. Bins" <elmi@4ever.de>
To: "NANOG Operators' Group" <nanog@nanog.org>
Sent: Monday, October 10, 2022 10:48:56 AM
Subject: Re: any dangers of filtering every /24 on full internet table to preserve FIB space ?

nanog@ics-il.net (Mike Hammett) wrote:

> Feasibility of adding some middleware that culls unneeded routes (existing more specific and aggregate routes pointing to the same next hop), when that table starts to fill?

Well... if that covering prefix goes away, let's hope you still have a default.

I've (been forced to) cull long prefixes on some memory-starved routers, and
given that all of them have defaults, For our (former employers and certainly
the current one) I've seen moderate to no traffic shifting, and this approach
gave the museum gear another lease on life - they were fine with bandwidth.
I've even gone down to strip anything longer than a /20 in v4, and a /40 in v6.

If you run a backbone that needs to know the best exit for a prefix in order to
throw traffic out locally and not pay good money for sightseeing capacity, you
might fare better with beefier routing engines.

El Mare.